祁建华
, 李孟哲
Qi Jianhua, Li Mengzhe
中图分类号: P425.5;X513
文献标识码: A
文章编号: 1001-8166(2018)06-0568-10
收稿日期: 2018-01-29
修回日期: 2018-04-11
网络出版日期: 2018-06-20
版权声明: 2018 地球科学进展 编辑部
基金资助:
作者简介:
First author: Qi Jianhua(1973-),female,Lanzhou City, Gansu Province,Professor. Research areas include atmospheric environment.E-mail:qjianhua@ouc.edu.cn
作者简介:祁建华(1973-),女,甘肃兰州人,教授,主要从事大气环境研究.E-mail:qjianhua@ouc.edu.cn
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摘要
生物气溶胶对全球气候、空气质量、大气过程和人体健康均具有重要影响。每年爆发的沙尘事件,使得生物气溶胶可借助沙尘进行长距离输运,从而影响到下风向地区生物气溶胶的浓度和性质。综述了沙尘天气下生物气溶胶中微生物的浓度、特性和分布特征的研究现状。已有研究显示,沙尘发生时,生物气溶胶中不同类别微生物的组成比例会有显著变化,细菌和真菌相对贡献随之改变。可培养细菌、真菌和总微生物浓度,均在沙尘天气下显著增加,但不同地区不同种类微生物在沙尘天气下的增加幅度相差很大。生物气溶胶中微生物主要分布于粗粒子中,其粒径分布受到沙尘天气的较大影响,而且不同种类微生物粒径分布的变化并不相同。沙尘发生时,生物气溶胶中的微生物群落结构与优势微生物也会发生明显改变。沙尘天气对生物气溶胶浓度、粒径分布、群落结构和活性的影响程度和影响机制,还需要进一步深入研究。
关键词：
Abstract
Atmospheric bioaerosols have great impact on the global climate, air quality, atmospheric process and human health. The dust events have a role in transporting bioaerosols and affecteing the concentration and property of bioaerosols in the downwind area by facilitating long-distance dispersal events every year. This paper reviewed the study progress on the concentration, characteristics and distribution of bioaerosols in dust weather. The references showed that the ratio of different kind of bioaerosols changed in dust weather with the changing of contribution of bacteria and fungi. The concentration of cultural bacteria, fungi and the total microbes increased on dust days. However, the increase ratio was different for different microbes in different areas. Microbes in bioaerosols mainly distributed in coarse particles; the size distribution of bioaerosols was affected greatly by dust events with different variation for different kinds of bioaerosols. The microbial community and predominant species of microorganism in bioaerosols changed in dust weather. The impact and mechanism of dust on the concentration, size distribution, microbial community and activity of bioaerosols need to be studied further.
Keywords：
生物气溶胶是大气气溶胶的重要组成部分,可占到气溶胶粒子总浓度的30%左右[1]。生物气溶胶通常来自于陆地和水生环境的生物活动[2],主要由含有微生物或生物大分子等生命活性物质的生物微粒组成, 包括细菌、真菌、病毒、花粉、孢子和动植物碎裂分解体等具有生命活性的粒子[2,3]。生物气溶胶还可以改变大气中冰核(Ice Nuclei,IN)和云凝结核(Cloud Condensation Nuclei,CCN) 的数量和特性[4,5,6,7,8,9,10],进而影响云量和气候变化,并会对人类社会发展造成影响[11]。生物气溶胶对空气质量和人体健康也具有明显的影响[12,13,14,15,16]。
天气条件对生物气溶胶中微生物的浓度、特性、分布等具有较大影响。在大风和强垂直对流等特定天气下,生物气溶胶可以借助沙尘暴事件进行长距离输运,并向大气输入大量的微生物,从而影响空气中微生物的分布和传输,并会扩大一些有机体的生物地理范围。每年亚洲和非洲沙尘暴事件产生的气溶胶多达几十亿吨[17]。2000—2012年,我国北方共出现157次沙尘天气过程,平均每年发生12次沙尘天气过程[18]。沙尘粒子不仅载有大量的化学物质,还携带着生物气溶胶。以往对沙尘长距离输送的生物气溶胶的研究非常有限,因为人们通常认为沙尘中的微生物在长距离传输过程中会因太阳紫外线、营养匮乏及干燥失水而死亡。实际上,大部分真菌和一些种类的细菌都能形成孢子,可以耐受干燥、高温、辐射和营养匮乏等条件[19]。从气溶胶样品中分离出的许多细菌含有色素,能有效避免紫外线的损伤[20];此外,云、雾、烟和沙尘粒子对微生物也有一定防护作用[20,21,22]。已有的研究表明,沙尘在传输过程中会向下风向输送大量生物气溶胶,从而影响该区域生物气溶胶的浓度和特性[23,24,25,26,27]。此外,沙尘中的生物物质,如细菌和有机物质等,可能会增强冰云形成和降水的效率[28,29]。沙尘中的生物物质也可能导致疾病的增多,Liu等[30]研究发现亚洲沙尘气溶胶中的某些微生物能够导致过敏性的肺部疾病,Ichinose等[31]研究发现,亚洲沙尘中的微生物可能会引起与卵清蛋白相关的嗜酸性细胞肺部炎症的加重,大气中的霉菌、细菌等可能会直接影响人体健康。
鉴于沙尘天气对生物气溶胶浓度、性质和分布特征的重要影响,近年来许多相关研究工作已相继开展。本文综述了沙尘天气发生时,生物气溶胶的浓度、粒径分布、微生物群落及活性等相关方面的研究进展。
空气微生物是生物气溶胶中非常重要的一类,也是生物气溶胶的重要组成部分。从培养特征来说,微生物可以分为可在培养基上培养生长的“可培养”微生物和无法在培养基上培养生长的“不可培养”微生物。“可培养”微生物一般用平板计数法测定,根据所用培养基的不同,可以测定空气中的细菌、真菌和放线菌等。徐文兵等[32]提出了利用DAPI与DNA发生特异性结合,释放出蓝色至青绿色荧光,从而运用荧光显微镜计检测大气颗粒物中总体微生物(除完整孢子状真菌外)的方法,并成功测得青岛大气生物气溶胶中的总微生物为8.52×104~2.11×106 cells/m3[32,33,34,35]。Sahu等[36]研究发现环境中“可培养”微生物只是总体生物气溶胶中的一小部分,占比不到1%。青岛的研究与此结果一致,生物气溶胶中主要是“不可培养”微生物,“可培养”微生物只占总微生物的0.65%,但是所占比例随季节变化较大,为0.25%~0.87%[32,34]。Li等[34]发现,沙尘天气发生时,“可培养”微生物增加了222.8%,“可培养”微生物占总体微生物的比值从沙尘发生前的0.26%迅速增加到了0.49%。可见,沙尘天气会对生物气溶胶中不同类别微生物的组成比例有显著影响。
在“可培养”微生物中,真菌和细菌对可培养菌的贡献随研究区域不同而有较大变化。沈阳、北京、南京、北海和西安等地区大气中可培养细菌浓度高于真菌,细菌与真菌浓度的比值为1.1~4.1倍,随研究区域变化很大[37,38,39,40,41,42]。Agarwal等[43]也在新德里发现空气中可培养细菌的浓度高于可培养真菌。而Karbowska-Berent等[44]对波兰室内空气中的可培养细菌和真菌的测定结果显示,有些点位细菌显著高于真菌,而其他点位则相反。陈浩文[41]于2001—2002年用沉降法研究青岛空气中可培养细菌和真菌的浓度,发现细菌是“可培养”微生物的主要贡献者,是真菌浓度的7.3倍;而2009—2010年Li等[34]用分级采样器研究的结果显示青岛空气中可培养真菌的贡献略高于细菌,占“可培养”微生物的比例平均为65%;韩晨等[45]发现,2015年青岛空气中可培养真菌占有绝对优势,平均浓度是可培养细菌的11倍。可见,生物气溶胶中真菌和细菌对“可培养”微生物的贡献不仅随地域变化而且随时间也在发生变化。Li等[34]发现沙尘天气下,青岛生物气溶胶中可培养细菌和真菌浓度分别增加了174%和50%,细菌对“可培养”微生物的贡献从非沙尘天的59%增加到了72%。在伊朗[46]、以色列[47]和加勒比海[48],同样观测到沙尘事件对可培养菌组成影响较大,“可培养”微生物中细菌的比例从非沙尘天的42%~52%增加到了沙尘天的53%~83%。这些研究结果表明,沙尘事件会改变生物气溶胶中可培养细菌和真菌的相对贡献。
长距离传输沙尘事件对下风向地区生物气溶胶浓度的影响已有一些研究。非洲沙尘通常从大西洋向西传播到美洲和加勒比海,从不列颠群岛向北到斯堪的纳维亚半岛,穿过地中海到欧洲,再进入亚洲西南部[17]。在非洲沙尘事件中观测到,生物气溶胶中的可培养细菌和真菌等微生物浓度会较非沙尘天气显著增加[24,26]。Kellogg等[22]在西非马里地区的研究发现,沙尘期间可培养细菌和真菌的浓度明显增加,分别从背景期的200~1 100 bacterial CFU/m3和0~130 fungal CFU/m3增加到了720~15 700 bacterial CFU/m3和80~370 fungal CFU/m3。Soleimani等[46]在中东沙尘事件中也发现了“可培养”微生物浓度的明显增加,室外可培养细菌和真菌浓度从非沙尘天的423 CFU/m3和596 CFU/m3增加到了1 257 CFU/m3和1 116 CFU/m3,室内可培养细菌和真菌浓度由非沙尘天的329 CFU/m3和386 CFU/m3增加到了406 CFU/m3和550 CFU/m3。Schlesinger等[47]在以色列也观测到沙尘期间大气中“可培养”微生物浓度大幅上升。当沙尘传输到海洋上空时,带来了大量的外源微生物,也会导致海洋上空生物气溶胶中微生物浓度的增加。Griffin等[48]观测到沙尘天气下加勒比海上空大气中可培养微生物浓度明显增加,是非沙尘天微生物浓度的5.2倍。此外,Griffin等[49]于2003年观测到非洲沙尘向北美传输过程中,大西洋中脊地区大气中“可培养”微生物浓度与沙尘颗粒物浓度呈显著正相关。
亚洲沙尘通常从塔克拉玛干沙漠和戈壁沙漠向东传播,横跨韩国、日本和太平洋,并能够影响到北极、夏威夷群岛和美国西海岸地区[17]。亚洲沙尘期间,首尔地区生物气溶胶中的可培养细菌浓度明显增加,并且与总悬浮颗粒物(Total Suspended Particulate,TSP)和PM10(空气动力学粒径≤10 μm的粒子)浓度呈正相关[50]。北京地区沙尘期间可培养细菌浓度也出现了大幅上升,但其与PM10浓度并没有表现出相关性[51]。Ho等[52]也观测到亚洲沙尘事件中,中国台湾地区沙尘期间可培养真菌浓度明显增加,从背景期的4 839 CFU/m3增加到了6 078 CFU/m3。在黄海沿岸,同样观测到沙尘期间“可培养”微生物的浓度较非沙尘天气增加了222.8%,而总微生物浓度增加了118.6%[34]。
目前对于总微生物、耐盐菌等其他类别生物气溶胶的影响研究相对缺乏。Maki等[53]在日本海以南的沿海城市,研究了亚洲沙尘事件期间总微生物浓度的变化,发现生物气溶胶中总微生物浓度从沙尘前的7.5×104 cells/m3迅速增加到了2.0×107 cells/m3,沙尘过后又降到了7.7×104 cells/m3。Yuan等[51]在北京的研究发现,沙尘期间的总细菌浓度比非沙尘期间高出了1个数量级,并且与PM10浓度呈显著正相关。李鸿涛等[33]观测到亚洲沙尘期间,兰州和青岛地区的总微生物浓度均呈现大幅上升趋势,兰州较强沙尘期间总微生物浓度升高了13.8倍,青岛浮尘期间总微生物浓度升高了5.42倍。Tang等[54]也观测到在亚洲沙尘事件中,中国北部地区总微生物浓度由非沙尘天的104~105 cells/m3增加到了沙尘天的105~106 cells/m3。
这些研究显示,不论可培养细菌、真菌还是总微生物浓度,均在沙尘天气下显著增加,但不同地区不同种类微生物的变化相差很大(图1)。可见,沙尘天气对生物气溶胶中微生物种类及其浓度的影响是一个非常复杂的过程,受到多种因素的影响,天气过程与沙尘源地、强度、沙尘粒子浓度、粒子组分等都会影响生物气溶胶的组成与浓度,要真正理解其中的机制,有必要进一步深入研究。
微生物在空气中的存活能力[58]、传输[25]以及在人体呼吸道的沉积[59]等行为与生物气溶胶的粒径、密度和形状密切相关。不同种类的微生物具有不同的粒径分布[34,60,61]。从表1可看出,除Wang等[67]在中国台湾发现可培养细菌中值粒径在1.51~1.81 μm外,非沙尘天气下,细菌、真菌和总微生物主要分布于粗粒径颗粒物中。陆地生物气溶胶中细菌的中值粒径在2.4~6.6 μm,这与细菌主要附着在粗颗粒物上有关,粗颗粒物可以为细菌提供更好的庇护作用,减少其受紫外线环境暴露的影响,因而有利于微生物的存活[75]。陆地生物气溶胶中真菌多单独悬浮于空气中,其中值粒径在2.08~4.33 μm[62~66,68,70,71],这与早期研究一致[76]。而有限的研究[72,73,74]显示,海洋生物气溶胶中细菌和真菌的中值粒径比陆地样品小,分别为1.89~2.37和2 μm。这些研究显示,不论海洋还是陆地生物气溶胶中,空气微生物均主要存在于粗粒子中。
沙尘天气对生物气溶胶的粒径分布同样具有较大影响。Yeo等[77]在韩国瑞山春季发现,沙尘天气下在1.1~2.1 μm粒子上存在真菌孢子,但在非沙尘天气下并未在该粒径段观测到孢子,说明在亚洲沙尘期间有细粒径的真菌孢子悬浮于空气环境中。而Choi等[78]在亚洲沙尘期间观察到粒径在0.6~4.3 μm的细菌增加很多,但是真菌粒径谱无变化。李鸿涛等[33]研究发现,兰州地区生物气溶胶中总微生物浓度的最高峰值由非沙尘天的大于7.0 μm移动到了沙尘天的1.1~2.1 μm,而青岛地区由非沙尘天的双峰分布转变为沙尘天的粗粒径为主的偏态分布。Polymenakou等[79]于2006年2月在地中海东部沿海城市的一次强沙尘过程中发现,不仅载有产芽孢菌的大粒子(>3.3 μm)浓度增加,可吸入粒子浓度也会增加,而且放线菌和拟杆菌属等微生物的浓度随小粒子粒径的减小而增大,其中很大一部分还与引发人类疾病的几种病原微生物有亲缘关系。
图1 全球沙尘期间生物气溶胶的浓度水平(数据来源于参考文献[33,46~48,50~52,54~57])
a.采样位置为34.999°N, 122.177°E;b.采样位置为33.229°N,125.216°E
Fig.1 Concentration levels of bioaerosols during global dust period (adapted from references[33,46~48,50~52,54~57])
a.Sampling located at 34.999°N,122.177°E;b.Sampling located at 33.229°N,125.216°E
表1 大气生物气溶胶中细菌、真菌和总微生物的中值粒径
Table 1 The median particle size of bacteria, fungi and total microbes in atmospheric bioaerosols
| 研究地区 | 中值粒径/μm | 参考 文献 | ||
|---|---|---|---|---|
| 可培养细菌 | 可培养真菌 | 总微生物 | ||
| 青岛 | 陆源:5.22 海源:5.71 | 陆源:2.61 海源:2.71 | [62] | |
| 青岛 | 2.37 | [57] | ||
| 杭州 | 3.4~3.8 | 2.9~3.0 | [63] | |
| 北京 | 4.59~5.13 | 3.73~4.33 | [64] | |
| 北京西单 | 5.6 | |||
| 北京丰台 | 6.6 | 3.9 | [65] | |
| 天津塘沽 | 5.5 | |||
| 中国台湾 | 2.76 | 2.02 | [66] | |
| 中国台湾 | 1.51~1.81 | [67] | ||
| 中国台北 | 2.3~3.1 | [68] | ||
| 美国华盛顿 | 3.2~4.8 | [58] | ||
| 美国俄勒冈州 | 3.93 | [69] | ||
| 英国 | 3~4.48 | 2.08~4.22 | [70] | |
| 新加坡 | 2.4 | 2.46 | [71] | |
| 瑞典 | 2 m高:2.58~3.75 10 m高: 2.46~3.73 | [72] | ||
| 地中海 | 2.11 | 2 | [73] | |
| 上海至北冰洋航线 | 1.89~2.37 | [74] | ||
可见,不同种类微生物的粒径分布在沙尘天气下的变化是不同的,尚不明确沙尘天气下生物气溶胶粒径分布的变化规律,而且目前的研究较多集中于生物气溶胶中的细菌和真菌,对于总微生物等其他微生物在不同粒径上的分布和浓度变化的关注不够。
微生物群落结构是微生物种群对其外界环境因子的反映,当出现沙尘天气时,气象条件等环境因子会发生改变,生物气溶胶中的微生物群落结构与优势微生物也会发生改变[47,50,51,80~82]。Hara[83]在中国东海的研究发现,沙尘天气下生物气溶胶中的可培养细菌以能形成孢子的细菌为主,此外还有一些则是含有高的鸟嘌呤和胞嘧啶的革兰氏阳性菌,而鸟嘌呤和胞嘧啶的含量越高,细菌的紫外辐射耐受性越强[84]。Fumihisa等[85]的研究也发现了相似的结果,与土壤中的细菌相比,沙尘携带的生物气溶胶中的细菌紫外辐射耐受性更高,其孢子的紫外辐射耐受性也要比土壤中的高。这些优势微生物的改变是生物气溶胶可借助沙尘长距离传输的原因之一。
Lee等[80]研究发现,沙尘天气发生时,微生物的群落结构会发生很大变化,对人体健康有害的类群增多。Chao等[86]在亚洲沙尘生物气溶胶中发现了非沙尘天未观测到的葡孢霉属和单端孢属。Jeon等[50]在韩国观察到生物气溶胶中的细菌群落在亚洲沙尘事件中发生了突然改变,这种改变与PM2.5化学组成的变化呈现相同趋势,意味着沙尘粒子与群落变化有一定的相关性,但尚不能确定是何种粒子组分影响着微生物群落。Maki等[53]在日本海以南的沿海城市,发现沙尘期间因为沙尘和海洋气溶胶的输入,沿海的微生物群落结构易发生变化,沙尘事件初始阶段检测到了海洋源的变形菌纲,而沙尘期间2种来自中国沙漠的硬壁菌门种为优势菌,沙尘结束后主要为来自局地陆源的巨大芽胞杆菌。韩晨等[87]在青岛的研究显示,沙尘天与晴天生物气溶胶中真菌的物种差异较大,不同沙尘天真菌种类差异较大,但优势菌均为曲霉属菌株,而且沙尘天对人类健康存在潜在危险的产毒真菌数量高于晴天。
也有研究发现,沙尘传输过几百乃至几千公里后,耐盐菌成为生物气溶胶中微生物的典型种类[17,88,89]。Maki等[88]在敦煌的沙尘粒子中检测到了存活的耐盐菌,DNA测序显示其与深海中存在的耐盐菌极为相似,推测沙尘沉降是海洋细菌的一个来源。Hua等[90]的研究也发现了类似的结果,沙尘携带的细菌具有高度的耐盐性。而且,沙尘携带的细菌主要为革兰氏阳性菌,对恶劣环境有更强的耐受力[22,24~25,46,48],在地中海沿岸发现沙尘期间77%的细菌是革兰氏阳性菌或革兰氏阳性产孢菌[91]。
综上所述,沙尘事件对空气环境中微生物群落结构影响很大,但是沙尘天气对微生物群落结构的影响是一个非常复杂的过程,加之相关研究缺乏,对沙尘天气下微生物群落结构的变化规律尚不可知,要真正理解沙尘事件对微生物群落结构的影响,需要进一步深入研究。
微生物活性是指微生物进行新陈代谢活动的强度,其活性水平取决于多种生物、化学和物理因素以及环境营养状况,可用于评估各种干扰过程(如人为活动等)对微生物群落的影响[92,93]。环境样品微生物活性测定主要是通过测定其生理代谢活性水平来实现,目前土壤和水体环境样品中微生物活性测定主要包括4类检测技术:碳呼吸、放射性标记物掺入细胞大分子、腺苷能荷(AEC)和酶活性分析[94]。由于空气中微生物的浓度要比土壤、水体等环境中的低很多,微生物活性的分析较为困难,迄今对生物气溶胶中微生物活性的研究仍非常有限。Qi等[95]提出了利用FDA水解法测定生物气溶胶中的微生物活性,该方法可以快速准确地测定微生物的活性水平,并得到了较好的验证。Hara等[56]在日本的研究发现,沙尘样品中细菌总浓度比非沙尘样品高1~2个数量级,但细菌存活率为16%~40%,低于非沙尘期。Yuan等[51]在北京的研究也得到了相同结果,细菌的存活率由沙尘前的64%降到了沙尘中的32%。
沙尘的长距离传输对细菌存活率有较大影响,也会影响到微生物活性,但目前对沙尘天气下生物气溶胶中的活性水平和分布特征尚未见到报道,更不清楚其区域变化和影响机制。但是,生物气溶胶的环境效应和健康效应很大程度上取决于活性,因此,要全面了解沙尘天气对生物气溶胶性质和分布的影响,就需要了解沙尘天气下微生物的活性水平和分布。
近年来,对沙尘天气下生物气溶胶的研究取得了较大进展,研究发现沙尘天气下生物气溶胶的浓度较非沙尘天显著增加,粒径谱发生明显改变,生物气溶胶中微生物活性及群落结构都较非沙尘发生很大变化。但是由于沙尘强度、传输途径、影响范围以及局地生物气溶胶的来源等这些影响因素复杂,目前尚不明确沙尘天气对生物气溶胶浓度、粒径分布和群落结构的影响程度和影响机制。将需要进一步深入研究以下问题。
(1)多数研究集中于可培养的细菌或真菌,而对沙尘天气下其他类别生物气溶胶(如总微生物,耐盐细菌、花粉等)的浓度和粒径分布的研究非常缺乏。运用在线检测技术结合离线分析,研究不同类别生物气溶胶的浓度和粒径谱,有助于全面了解沙尘天气下生物气溶胶的环境、气候和健康效应。
(2)目前对沙尘天下生物气溶胶的研究还很有限,尚未明确不同强度的沙尘(浮尘、扬沙等)天气下生物气溶胶浓度、粒径谱、微生物群落结构和优势微生物等特性的变化规律。需要在更大范围内系统研究不同沙尘事件下生物气溶胶的性质和分布,才能理解长距离传输沙尘对对生物气溶胶的影响机制。
(3)尽管目前发现生物气溶胶浓度和特性的改变与温度、相对湿度以及沙尘等特殊天气有关,但仍不能揭示其控制因素和影响机制。空气中生物气溶胶受到气象条件、大气过程、气溶胶化学组成、污染气体、局地源等多种因素的综合影响,除了现场观测,还需要室内单因子实验确定主要影响因素。
(4)目前有关微生物活性等生物气溶胶特性的研究匮乏,更缺乏沙尘事件对微生物活性影响的了解。以后仍需要建立灵敏测定生物气溶胶微生物活性、毒理性等生物气溶胶特性的方法,进一步深入研究生物气溶胶环境和健康效用。
(5)沙尘携带的生物气溶胶不仅影响到下风向生物气溶胶的性质,而且还会在一定天气条件下传输并沉降到海洋,影响海洋生态和环境,但是对其影响尚不清楚,亟需研究。
The authors have declared that no competing interests exist.
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This chapter demonstrates the relevance of biological aerosol particles as active participants in cloud forming processes. It uses an existing method for the determination of atmospheric biological aerosol particles to investigate rain-water samples and this size distribution in rainwater. Primary biological aerosol particles (PBAP) describe airborne solid particles that are derived from living organisms, including microorganisms and fragments of all varieties of living things. This definition includes a wide spectrum of biological particles spread over a large size range. The larger particle range includes bacteria, algae, spores of lichen, mosses, ferns, and fungi, pollen, plant debris like leaf litter, parts of insects, human, and animal epithelial cells. They are a ubiquitous component of the atmospheric aerosol and come to about 24% of the concentration of the total atmospheric particles. Besides their effects on air hygiene, they play an important role in cloud physics. Schnell and Vali suggested that a portion of atmospheric freezing nuclei was of biogenic origin. The sources of these nuclei include decaying vegetation, marine plankton, and bacteria. The peculiarity of the bacteria is that they have a freezing capability even at temperatures about -4掳 C while most mineral particles need temperatures below -10掳 C.
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Several strains of plant pathogenic bacteria, Erwinia carotovora carotovora and E. carotovora atroseptica, were observed to be active as cloud condensation nuclei (CCN). The CCN supersaturation spectra of bacterial aerosols were measured in the laboratory and compared to the activity of ammonium sulfate. Approximately 25%-30% of the aerosolized bacterial cells activated droplets at 1% water supersaturation compared to 80% activation of the ammonium sulfate aerosol. Physical and numerical simulations of cloud droplet activation and growth on bacteria were also performed. Both simulations predict that aerosolized bacteria will be incorporated into cloud droplets during cloud formation. Results strongly support the hypothesis that significant numbers of the tested bacterial strains are actively involved in atmospheric cloud formation and precipitation processes following natural aerosolization and vertical transport to cloud levels.
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[1] Bacteria cultivated from aerosol and cloud water samples collected at a remote Austrian mountain site under wintry conditions were tested for their ability to act as cloud condensation nuclei (CCN). The experiment was carried out with a cloud condensation nuclei counter (CCNC) operating on the principle of a static thermal diffusion chamber. Average concentrations of cultivable airborne bacteria amounted to 8 colony forming units (CFU) m0908083 in aerosol samples and to 79 CFU mL0908081 in cloud water. The set of tested bacteria comprised Gram positive and Gram negative but no known ice nucleating species. At supersaturations between 0.07 and 0.11% all types of bacteria were activated as CCN. As the sizes of the bacteria were smaller than the Kelvin diameters for the respective supersaturations, the physico-chemical properties of their outer cell walls must have enhanced their CCN activity.
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[1] With 18% of the total U.S. landmass devoted to croplands, farmland and farming activities are potentially major sources of biogenic particles to the atmosphere. Farms harbor large populations of microbes both in the soil and on plant surfaces which, if injected into the atmosphere, may serve as nuclei for clouds. In this study, we investigated two farms as potential sources of biological ice nuclei (IN): an organic farm in Colorado and a cornfield in Nebraska. We used a continuous-flow diffusion chamber (CFDC) to obtain real-time measurements of IN at these farm sites. Total aerosol particles were also collected at the sites, and their temperature-dependent ice nucleating activity was determined using the drop freezing method. Quantitative polymerase chain reaction and DNA sequencing of 16S rDNA clone libraries were used to test aerosols and washings of local vegetation for abundance of theinagene in ice nucleation active bacteria (from the well-known group within the-Proteobacteria) and to identify airborne primary biological aerosol particles. The vegetation in each of these farms contained 6 0103 105 to 2 0103 107 ina genes per gram vegetation. In contrast to the vegetation, airborne ina gene concentrations at the organic farm were typically below detectable limits, demonstrating a disconnect between local vegetative sources and the air above them. However, for measurements made during combine harvesting at the Nebraska corn field, ina gene concentrations were 19 L0908081, with maximum IN concentrations of 50 L0908081 determined from the CFDC at 0908082000°C and above water saturation. At both farms, there was also an apparent biological contribution to the IN population which did not contain the ina gene.
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Despite the enormous volume they represent and the importance they have for Earth’s climate, clouds remain environments where the microbiological features are still poorly understood. Studies of the microbial content existing in the atmosphere have demonstrated extreme quantitative and qualitative variability, of which the drivers yet need to be determined. Between 2007 and 2010, we collected cloud water from the puy de D00me summit in France (146502m a.s.l.) for chemical and microbiological analysis. These data were combined with cloud data collected between 2004 and 2005 following similar protocols. Overall, the cultivable community of chemotrophic aerobic microorganisms was dominated by pigmented colonies and accounted for <1% of the 3.302×0210 3 to 2.502×0210 5 total bacteria mL 611 , but up to 41% of the 8.902×0210 2 to 3.202×0210 4 fungal cells mL 611 . None of the concentrations of the chemical compounds measured was linked to the variations observed for the microbiological content, suggesting distinct sources and/or distinct modes of incorporation into cloud water. However, the overall dataset indicated that microorganisms in clouds were mostly originating from continental areas, especially from vegetation. We isolated and identified 185 heterotrophic bacteria and 150 yeasts from our samples (including -Alpha, -Beta and Gamma-Proteobacteria, Bacteroidetes, Firmicutes and Actinobacteria, and Basidiomycetous and Ascomycetous yeasts), the corresponding 16S and 26S rRNA gene sequences of which have been deposited in GenBank. A few genera largely dominated the pool of cultivable microorganisms in clouds, such as Pseudomonas and Sphingomonas for bacteria, which were detected in more than 40% of the clouds sampled, and Dioszegia and Udeniomyces for yeasts, detected in more than 60% of the samples. The recurring presence of some groups of microorganisms suggests that they have elaborated strategies of increased survival in the atmosphere and clouds.
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印度半岛和东亚是气溶胶大值区,也是亚洲季风的主要影响区域,季风和季风降水的变化对季风区的经济尤其是农业生产有重大影响。气溶胶影响印度季风的研究开始较早,研究工作也较多,已取得了较为全面的进展。早期研究表明大气棕云导致负辐射强迫可减缓温室气体带来的增暖。现有研究表明吸收性气溶胶对印度季风爆发早期有增强作用,随后气溶胶对印度和东亚夏季风有减弱作用。由于影响季风的因子较多、研究工作较为复杂,现有的气溶胶影响亚洲季风的研究还存在不确定性。回顾和概括了前人的研究,通过气溶胶影响东亚季风与印度季风的对比,讨论现有研究的不足,并为未来气溶胶影响季风特别是影响东亚夏季风的研究指出方向。
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The National Institute for Occupational Safety and Health (NIOSH) has carried out health hazard evaluations in five large office buildings where hypersensitivity pneulmonitis (HP) and other respiratory diseases have been alleged or reported. Environmental studies made both in the occupied space and in the heating, ventilating, and air-conditioning (HVAC) system of each building are described. Several buildings were characterized by a history of repeated flooding, and all contained mechanical systems with pools of stagnant water and microbial slimes. Preventive measures that may be effective in reducing build-associated microbial contamination and building-associated HP illnesses include the following: (A) Prevent moisture incursion into occupied space and HVAC system components; (B) Remove stagnant water and slimes from building mechanical systems; (C) Use steam as a moisture source in humidifiers; (D) Eliminate the use of water sprays as components of office building HVAC systems; (E) Keep relative humidity in occupied space below 70%; (F) Use filters with a 50% rated efficiency; (G) Discard microbially damaged office furnishings; (H) Initiate a fastidious maintenance program for HVAC air handling units and fan coil units.
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Abstract Abstract鈥 The percentage of pigmented to total bacteria in the outdoor atmospheric population was studied in the field and in controlled laboratory experiments to evaluate the effects of solar radiation (SR) on bacterial survival. The field experiments showed that the percentage of pigmented bacteria positively correlated with SR activity during clear summer days. The percentage was lowest during darkness before dawn and around midnight ( ca 33%) and as the SR increased during the day, gradually increased to a maximum of ca 50鈥60% at noontime to early afternoon and decreased thereafter. In the laboratory the ambient outdoor atmospheric bacteria impacted on culture plates were exposed to simulated SR and a germicidal light. With increased exposure, more nonpig-mented bacteria were killed and the percentage of pigmented bacteria gradually increased. These observations suggest an inverse relationship between the atmospheric bacterial survival and the percentage of pigmented bacteria contained therein, thus supporting the notion that pigmentation might provide protection for outdoor atmospheric bacteria from sunlight damage. As a consequence, viable pigmented bacteria (and other UV-resistant forms) in the atmosphere could be enriched under areas of stratospheric ozone depletion.
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Many hypotheses have been proposed to explain the decline of coral reefs throughout the world, but none adequately accounts for the lack of recovery of reefs or the wide geographical distribution of coral diseases. The processes driving the decline remain elusive. Hundreds of millions of tons of dust transported annually from Africa and Asia to the Americas may be adversely affecting coral reefs and other downwind ecosystems. Viable microorganisms, macro- and micronutrients, trace metals, and an array of organic contaminants carried in the dust air masses and deposited in the oceans and on land may play important roles in the complex changes occurring on coral reefs worldwide.
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Characterization of aerosolized bacteria and Fungi from desert dust events in Mali, West Africa [J].
Millions of metric tons of African desert dust blow across the Atlantic Ocean each year, blanketing the Caribbean and southeastern United States. Previous work in the Caribbean has shown that atmospheric samples collected during dust events contain living microbes, including plant and opportunistic human pathogens. To better understand the potential downwind public health and ecosystem effects of the dust microbes, it is important to characterize the source population. We describe 19 genera of bacteria and 3 genera of fungi isolated from air samples collected in Mali, a known source region for dust storms, and over which large dust storms travel.
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Detection of mineral dust over the North Atlantic Ocean and Africa with the Nimbus 7 TOMS [J].
It has recently been found that the ultraviolet measurements obtained with the Nimbus 7 total ozone mapping spectrometer (TOMS) instrument can be used to retrieve information on the distribution of aerosols over oceanic and continental surfaces. Here we examine the use of the derived TOMS aerosol index (AI) for the detection of absorbing aerosol in terms of mineral dust aerosol over the North Atlantic Ocean and North Africa. Specifically, we compare the TOMS AI with the time series of daily aerosol measurements made in the boundary layer at Sal Island (Cape Verde), Barbados, and Miami and in the free troposphere on Tenerife (Canary Islands); these sites are frequently impacted by African dust events. At Tenerife, over the time period 19880900091992, TOMS detected 80% of the African dust events that yielded daily average dust concentrations greater than 20 0204g m0908083; at Barbados and Miami, TOMS detected 65% and 44% respectively of the events over the period 19790900091992. If we exclude events during which some of the TOMS data are missing and also short (1-day) dust events, TOMS detected 99% of the events at Tenerife, 97% at Barbados, and 81% at Miami. TOMS was also successful in detecting the 090008low altitude090009 African dust events recorded at Sal during the winter season. Over Africa we compare the TOMS AI data with ground-based measurements of aerosol optical thickness (AOT) obtained during field experiments in Senegal and Niger; these yield a nearly linear relationship between the TOMS AI and the AOT. Discrepancies between ground-based measurements (in terms of dust concentrations or AOT) and TOMS AI can be attributed to a number of factors: variations in the physical properties of the aerosol; the sensitivity of the TOMS response to the altitude of the aerosol layer; or the coarse spatial resolution of the TOMS pixel. Nonetheless, our results clearly show that the TOMS AI provides a remarkably accurate picture of mineral dust distributions in the atmosphere over both continental and oceanic regions.
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Interhemispheric transport of viable fungi and bacteria from Africa to the Caribbean with soil dust [J]. |
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African desert dust in the Caribbean atmosphere: Microbiology and public health [J].
Air samples collected on St. John in the U.S.Virgin Islands were screened for the presenceof viable bacteria and fungi to determine ifthe number of cultivatable microbes in theatmosphere differed between ``clear atmosphericconditions'' and ``African dust-events.'' Resultsindicate that during ``African dust-events,'' thenumbers of cultivatable airborne microorganismscan be 2 to 3 times that found during ``clearatmospheric conditions.'' Direct microbialcounts of air samples using an epifluorescentmicroscopy assay demonstrated that during an``African dust-event,'' bacteria-like andvirus-like particle counts were approximatelyone log greater than during ``clear atmosphericconditions.'' Bacteria-like particles exhibitingautofluoresence, a trait of phototrophs, wereonly detected during an ``African dust-event.''
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| [26] |
The relationship between gorgonian coral (Cnidaria: Gorgonacea) diseases and African dust storms [J].
The number of reports of coral diseases has increased throughout the world in the last 20 years. Aspergillosis , which primarily affects Gorgonia ventalina and G. flabellum , is one of the few diseases to be characterized. This disease is caused by Aspergillus sydowii , a terrestrial fungus with a worldwide distribution. Upon infection, colonies may lose tissue, and ultimately, mortality may occur if the infection is not sequestered. The spores of A. sydowii are <5 渭m, small enough to be easily picked up by winds and dispersed over great distances. Aspergillosis is prevalent in the Caribbean, and it appears that this primarily terrestrial fungus has adapted to a marine environment. It has been proposed that dust storms originating in Africa may be one way in which potential coral pathogens are distributed and deposited into the marine environments of the Caribbean. To test the hypothesis that African dust storms transport and deposit pathogens, we collected air samples from both dust storms and periods of non-dust in St. John, U.S. Virgin Islands . Because we focused on fungal pathogens and used A. sydowii as a model, we isolated and cultured fungi on various types of media. Fungi including Aspergillus spp. were isolated from air samples taken from dust events and non-dust events. Twenty-three separate cultures and seven genera were isolated from dust event samples whereas eight cultures from five genera were isolated from non-dust air samples. Three isolates from the Virgin Islands dust event samples morphologically identified as Aspergillus spp. produced signs of aspergillosis in seafans, and the original pathogens were re-isolated from those diseased seafans fulfilling Koch's Postulates. This research supports the hypothesis that African dust storms transport across the Atlantic Ocean and deposit potential coral pathogens in the Caribbean.
|
| [27] |
Mixture of Kosa (Asian dust) and bioaerosols detected in the atmosphere over the Kosa particles source regions with balloon-borne measurements: Possibility of long-range transport [J]. |
| [28] |
DeMott P J, French J R, et al. In situ detection of biological particles in cloud ice-crystals [J].
The impact of aerosol particles on the formation and properties of clouds is one of the largest remaining sources of uncertainty in climate change projections. Certain aerosol particles, known as ice nuclei, initiate ice-crystal formation in clouds, thereby affecting precipitation and the global hydrological cycle. Laboratory studies suggest that some mineral dusts and primary biological particles-such as bacteria, pollen and fungi-can act as ice nuclei. Here we use aircraft-aerosol time-of-flight spectrometry to directly measure the chemistry of individual cloud ice-crystal residues (obtained after evaporation of the ice), which were sampled at high altitude over Wyoming. We show that biological particles and mineral dust comprised most of the ice-crystal residues: mineral dust accounted for ~50% of the residues and biological particles for ~33%. Along with concurrent measurements of cloud ice-crystal and ice-nuclei concentrations, these observations suggest that certain biological and dust particles initiated ice formation in the sampled clouds. Finally, we use a global aerosol model to show long-range transport of desert dust, suggesting that biological particles can enhance the impact of desert dust storms on the formation of cloud ice.
|
| [29] |
Dust and biological aerosols from the Sahara and Asia influence precipitation in the western US [J]. |
| [30] |
Lung inflammation by fungus, Bjerkandera adusta isolated from Asian Sand Dust (ASD) aerosol and enhancement of ovalbumin-induced lung eosinophilia by ASD and the fungus in mice [J]. |
| [31] |
The effects of microbial materials adhered to Asian sand dust on allergic lung inflammation [J].
Asian sand dust () containing microbiological materials, (SO(4)(2)), and nitrate (NO(3)(-) ) derived from air pollutants in East China, reportedly cause adverse respiratory health effects. aggravates (OVA)-associated experimental lung . In this study, the toxic materials adsorbed onto were excluded by heat treatment at 360 degrees C for 30 min. The effects of nonheated or heated (H-) toward the allergic were compared in lungs. ICR were administered intratracheally with normal saline (control), H-, , OVA, OVA + H-, and OVA + , four times at 2-week intervals. only increased neutrophils in bronchoalveolar lavage fluids (BALFs) along with pro-inflammatory mediators, such as keratinocyte chemoattractant (KC). H-and enhanced eosinophil recruitment induced by OVA in the alveoli and in the submucosa of the airway, which has a goblet in the bronchial epithelium. The two synergistically increased interleukin-5 (), (), and eotaxin, which were associated with OVA, in BALF. The enhancing effects were much greater in than in H-. The two induced the adjuvant effects to specific IgE and IgG1 production by OVA. In the in vitro study using RAW264.7 cells, increased the expression of Toll-like receptor 2 (2) but not . H-caused no expression of either . These results suggest that the aggravated lung by may be due to activation of Th2-associated via the activation of by microbial components adhered to .
|
| [32] |
Concentration distribution of bioaerosols in summer and autumn in the Qingdao Coastal region [J].青岛近海夏、秋季生物气溶胶分布特征研究 [J]. |
| [33] |
Influence of dust events on the concentration and size distribution of microorganisms in bioaerosols [J].沙尘天气对生物气溶胶中总微生物浓度及粒径分布的影响 [J].
为了解沙尘对生物气溶胶中微生物的影响,于2015年3~4月间分别在兰州和青岛沙尘期间运用分级生物气溶胶采样器连续采集了生物气溶胶样品,并利用DAPI染色-荧光显微镜计数方法测定了总微生物浓度.结果表明,沙尘发生时生物气溶胶中总微生物浓度显著增加(P7.0μm的粒径上,最低值均出现在4.7~7.0μm的粒径上,浓度次高峰值分别出现在3.3~4.7μm的粒径上和1.1~2.1μm的粒径上.沙尘时粒径分布均发生明显变化,兰州仍呈现双峰分布,但其中一个峰值从>7.0μm移动到1.1~2.1μm;而青岛粒径由双峰分布变为粗粒径偏态分布.兰州和青岛沙尘前微生物负荷的背景值分别是2224 cells?μg-1和1550 cells?μg-1,而沙尘发生时,颗粒物的微生物负荷均大幅增加,最高值分别达26442 cells?μg-1和10250 cells?μg-1,这说明沙尘天气发生时,微生物浓度的增加不仅仅是因为空气中颗粒物的增加,而是因为长距离传输的沙尘颗粒携带有大量外源微生物.
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| [34] |
Concentration and size distribution of bioaerosols in an outdoor environment in the Qingdao coastal region [J]. |
| [35] |
Concentration and size distribution of total airborne microbes in hazy and foggy weather [J]. |
| [36] |
A static water surface sampler to measure bioaerosol deposition and characterize microbial community diversity [J]. |
| [37] |
Relationship between atmospheric bacteria and fungal particles in Shenyang City [J].沈阳市大气细菌与真菌粒子的关系 [J]. |
| [38] |
Concentration of atmospheric microbes in Beijing and Tianjin area [J].京、津地区大气微生物的浓度 [J].
本文用仿制美国的ANDERSEN生物粒子采样器测定了北京两单、丰台和天津塘沽海滨三个地点的大气细菌和真菌浓度,结果表明,年平均空气细菌浓度北京西单为3.02个/L、丰台为2.56个/L、天津塘沽海演为1.38个/L,丰台真菌为1.20个/L,在一天内,大气细菌浓度分布明显出现7点、22点二个高峰时和13点、夜间1点二个低峰时,由ANDERSEN采样分为六级的大气细菌浓度亦有同样的目变化规律。
|
| [39] |
Survey of atmospheric microorganism pollution in Nanjing City [J].南京市大气微生物污染情况调查 [J].
为了研究城市生物气溶胶的污染及其传播规律,于1998年春夏两季在南京大学校园的气象塔进行微生物监测.24小时内不同时间和不同高度的大气细菌和真菌浓度采样测定研究结果表明,夏季无论是细菌还是真菌平均浓度都高于春季;不论是春季还是夏季的细菌和真菌平均浓度都随高度的增加而减少;一天内4个时间的细菌、真菌样品形态特征分类.结果表明,两个季节大气细菌以革兰氏阳性菌占绝对优势,各种形态的细菌中,球菌占首位;大气真菌共鉴定出五属一科,春夏两季均以青霉属占首位.
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| [40] |
Spatial and temporal distribution of air microorganism content in Beihai City [J].北海市空气微生物含量时空分布 [J].
于１９９６／１９９７年之交研究了广西北海市空气微生物含量及其分布特征，结果表明北海市室外空气细菌、真菌及总微生物含量分别为５７０９．７ＣＦＵ／ｍ３、１８４７．１ＣＦＵ／ｍ３和７５５６．８ＣＦＵ／ｍ３。已超过了相关规定的轻度空气污染程度。客房空气质量较好。空气微生物含量显出的测点差意味着北海市闹市区空气质量一般差于非闹市区，随离陆地采样高度的抬升，空气微生物呈减少之势，其昼夜变化特征表现出空气细菌及总量在下午达峰值，上午次之，晨间为谷，而空气真菌在中午峰值之前出现低谷。空气细菌、空气真菌和空气微生物总量与气温间分别有显著正相关关系。北海市空气微生物含量变化显出不全同于我国一些亚热带或内陆城市的势
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| [41] |
Determination of the air microorganism in Qingdao [J].青岛空气微生物状况的测定 [J].
本文用自然沉降法于2001和2002年分别对青岛10个测点作19次空气微生物测定.论述青岛空气中陆源和海洋微生物的时空变化状况,平均陆源细菌、真菌、总菌量和(F/T)%分别为8781.8\3014.5\11796.3CFU·m-3及25.6,平均海洋细菌、真菌、总菌量及(F/T)%分别为314.4\895.2\1209.6CFU·m-3及74.0.表明青岛空气处中度微生物污染状态,陆源污染较重,向滨海区扩张势头较强.结果显示海洋对陆地空气具调节作用.
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| [42] |
Concentration and size distribution characteristics of culturable bioaerosols at various air quality levels in Fall and Winter in Xi’an, China [J].西安市秋冬季不同空气质量下可培养微生物气溶胶浓度和粒径分布 [J].
利用Anderson空气微生物采样器对西安市2014年9月～2015年1月间可培养微生物气溶胶进行采样、培养,分析不同空气质量下其浓度与粒径变化特征,并对其与颗粒污染物（PM2.5、PM10）、气象参数（温度、相对湿度）和其它气态污染物（NO2、SO2、O3）进行主成分＋多元线性回归分析.结果显示,可培养细菌和真菌气溶胶浓度范围分别为97～1 909CFU·m^-3,92～1 737 CFU·m^-3.随空气污染程度加深,两种微生物气溶胶浓度均呈现增加趋势;细菌气溶胶粒径分布向粗颗粒偏移;而真菌气溶胶在低污染时呈正态分布,高污染时粒径峰值向细颗粒偏移.主成分分析结果显示,可培养微生物气溶胶主要与灰霾、太阳辐射和相对湿度有关.多元线性回归结果表明,细菌气溶胶与灰霾呈显著正相关（P〈0.05）,与太阳辐射呈不显著负相关,与湿度呈不显著正相关;真菌气溶胶与灰霾、太阳辐射和相对湿度均呈不显著正相关.研究结果可以为评估微生物气溶胶所引起的环境与健康效应提供基础数据.
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| [43] |
Characterization of Bioaerosols and their relation with OC, EC and Carbonyl VOCs at a busy roadside restaurants-cluster in New Delhi [J]. |
| [44] |
Airborne and dust borne microorganisms in selected Polish libraries and archives [J].
The other objective of this study was to evaluate the effect of renovation and mechanical cleaning of the flooded storeroom collection on the level of microbial contamination. The obtained results show that both of the applied procedures reduced the concentration of fungal and bacterial aerosols by almost 80% and 50%, respectively. A significant reduction in the number of airborne microbial species was also noted. Hence, if the source of moisture is removed and mechanical cleaning is subsequently applied, the hygienic quality of a storeroom collection can be significantly improved.
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| [45] |
Size distribution characteristics of culturable bioaerosols in relation to air quality levels in Qingdao [J].青岛市不同空气质量下可培养生物气溶胶分布特征及影响因素 [J].
利用Andersen空气微生物采样器采集青岛市不同空气质量下的可培养生物气溶胶,分析了其浓度和粒径分布特征,并利用Spearman’s相关性分析了可培养生物气溶胶浓度和空气质量指数中的颗粒物质量浓度〔ρ(PM_(10))、ρ(PM_(2.5))〕、气体污染物质量浓度〔ρ(O3)、ρ(SO_2)、ρ(NO_2)〕和气象参数(温度、相对湿度、风速)之间的关系.结果表明:可培养真菌和细菌气溶胶浓度范围分别为133~1 113和13~212 CFU/m3.真菌气溶胶浓度与ρ(SO_2)、ρ(PM_(10))、ρ(PM_(2.5))均呈正相关,而与相对湿度呈显著负相关(P0.05).细菌气溶胶浓度与ρ(NO_2)、ρ(SO_2)呈负相关,而与ρ(O3)、温度呈正相关.风速对可培养生物气溶胶浓度的影响较小.以AQI(空气质量指数)中ρ(PM_(10))为依据,将研究时间段空气质量划分为4个空气污染等级.在不同污染等级下,真菌气溶胶均呈对数正态分布,粒径主要分布于2.1~4.7μm.低污染时细菌气溶胶呈偏态分布(粒径4.7μm),高污染时粒径分布发生改变.初步推断,随着空气污染等级的升高,可培养生物(真菌+细菌)气溶胶总浓度增加,但单位颗粒物上的浓度变化较稳定.ρ(PM_(10))是影响可培养生物气溶胶浓度及粒径分布的主要因素.
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| [46] |
Impact of Middle Eastern dust storms on indoor and outdoor composition of bioaerosol [J].
61Bioaerosol composition measurements in and outside of a hospital in Ahvaz, Iran.61Outdoor bioaerosol are shown to impact indoor hospital air quality.61Bacteria and fungi concentrations higher on dusty days in and out of hospital.61Indoor:outdoor ratios of bioaerosol lower on dusty days (≤0.60) versus normal days.61Gram positive bacteria exhibit higher concentrations than Gram negative bacteria.
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| [47] |
Transport of microorganisms to Israel during Saharan dust events [J].
Dust storms are serious meteorological events that affect the East Mediterranean region, primarily during the spring season. The physical and chemical nature of dust storms, their origin, and the meteorological conditions leading to the generation of storms have been fully documented, but knowledge on their biological content is almost nonexistent. Four dust events that occurred in the period 2004–2005 were sampled in Haifa, Israel, an urban area on the East Mediterranean coast, for biological characterization. Samples were taken before or after (depending on the meteorological conditions) as well as during the dust events. Dust particles were collected as two size fractions using a dichotomous sampler, and their elemental content was determined using X-ray fluorescence analyses. Airborne bacteria and fungi were collected with the Six Stage Andersen Viable Impactor. Fungi were identified by optical microscopy. Compared to adjacent clear days, there was an increase in the concentration of both atmospheric particles and elements of geological and marine origin during the dust events. The concentration of airborne microorganisms during the dust events was also higher, and the fungal population content was affected. On a winter clear day the abundant airborne fungi were Paecilomyces02variotii , Penicillium02glabrum , and Alternaria02alternata . On a spring clear day, the persisting airborne fungi were Alternaria02alternata , Geotrichum02candidum , Penicillium02chrysogenum , and P.02glabrum . However, during two dust events the fungal population was dominated by Alternaria alternata , Aspergillus02fumigatus , A.02niger , A.02thomii , Cladosporium02cladosporioides , Penicillium02chrysogenum , and P.02griseoroseum . This study suggests that Saharan and other desert dust events in the East Mediterranean have a significant effect on the airborne microbial populations, which might impact on health, agriculture, and ecology.
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| [48] |
Atmospheric microbiology in the northern Caribbean during African dust events [J].
Between July 2000 and August 2001 forty-threeair samples were collected in the northernCaribbean: Twenty-six in the US VirginIslands, and 17 samples aboard ship during two1-week cruises. Samples were collected duringAfrican dust events and non-dust conditions andscreened for the presence of culturablebacteria and fungi. A total of 3,652 liters ofair were collected during non-dust conditions,with 19 bacteria and 28 fungi being recovered.During dust conditions a total of 2,369 litersof air were screened resulting in the recoveryof 171 bacteria and 76 fungi. A statisticallysignificant difference was found between thetwo data sets. These results support previousAfrican dust research and further demonstratethat dust particles can serve as a vessel forthe global dispersion of bacteria and fungi.Dustborne microorganisms may play a significantrole in the ecology and health of downwindecosystems.
|
| [49] |
Airborne microorganisms in the African desert dust corridor over the mid-Atlantic ridge, Ocean Drilling Program, Leg 209 [J]. |
| [50] |
Impact of Asian dust events on airborne bacterial community assessed by molecular analyses [J].
Impact of Asian dust events (ADE) on atmospheric bacterial communities was studied using both cultivation and culture-independent methods. In addition, size-segregated aerosol mass concentrations and their chemical compositions were measured and backward trajectory analysis was performed. During the days affected by ADE, culturable bacterial population levels showed significant positive correlations with total suspended particles (TSP) and particulate matter with aerodynamic diameter < 10 渭m (PM 10), whereas no significant correlation was found during non-Asian dust (NAD) days. Asian dust seemed to directly impact the airborne bacterial communities, as abrupt changes of denaturing gradient gel electrophoresis (DGGE)-band patterns and significant differences in the 16S rDNA clone library between ADE and NAD days were observed. In addition, the changes of DGGE patterns were in agreement with the shift of PM 2.5 chemical composition, suggesting that the outdoor bacterial community was affected by the source and transport pathways of air masses. The isolation sources of clone libraries reflected the sampled air mass transport pathways, which were simulated by backward trajectories. The results of this study revealed that the airborne culturable bacterial concentration was聽significantly increased and the ambient bacterial community structure was abruptly changed during聽ADE.
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| [51] |
Cell concentration, viability and culture composition of airborne bacteria during a dust event in Beijing [J]. |
| [52] |
Characteristics and determinants of ambient fungal spores in Hualien, Taiwan [J].
Characteristics and determinants of ambient aeroallergens are of much concern in recent years because of the apparent health impacts of allergens. Yet relatively little is known about the complex behaviors of ambient aeroallergens. To address this issue, we monitored ambient fungal spores in Hualien, Taiwan from 1993鈥1996 to examine the compositions and temporal variations of fungi, and to evaluate possible determinants. We used a Burkard seven-day volumetric spore trap to collect daily fungal spores. Air pollutants, meteorological factors, and Asian dust events were included in the statistical analyses to predict fungal levels. We found that the most dominant fungal categories were ascospores, followed by Cladosporium and Aspergillus/Penicillium . The majority of the fungal categories had significant diurnal and seasonal variations. Total fungi, Cladosporium , Ganoderma , Arthrinium/Papularia , Cercospora , Periconia , Alternaria , Botrytis , and PM 10 had significantly higher concentrations ( p <0.05) during the period affected by Asian dust events. In multiple regression models, we found that temperature was consistently and positively associated with fungal concentrations. Other factors correlated with fungal concentrations included ozone, particulate matters with an aerodynamic diameter less than 10聽渭m (PM 10 ), relative humidity, rainfall, atmospheric pressure, total hydrocarbons, carbon monoxide, nitrogen dioxide, and sulfur dioxide. Most of the fungal categories had higher levels in 1994 than in 1995鈥96, probably due to urbanization of the study area. In this study, we demonstrated complicated interrelationships between fungi and air pollution/meteorological factors. In addition, long-range transport of air pollutants contributed significantly to local aeroallergen levels. Future studies should examine the health impacts of aeroallergens, as well as the synergistic/antagonistic effects of weather, and local and global-scale air pollutions.
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| [53] |
Variations in the structure of airborne bacterial communities in a downwind area during an Asian dust (Kosa) event [J]. |
| [54] |
Characterization of atmospheric bioaerosols along the transport pathway of Asian dust during the Dust-Bioaerosol 2016 Campaign [J]. |
| [55] |
Impacts of Asian dust events on atmospheric fungal communities [J].
The composition of atmospheric fungi in Seoul during Asian dust events were assessed by culturing and by molecular methods such as mold specific quantitative PCR (MSQPCR) and internal transcribed spacer cloning (ITS cloning). Culturable fungal concentrations in the air were monitored from May 2008 to July 2011 and 3 pairs of ITS clone libraries, one during Asian dust (AD) day and the other during the adjacent non Asian dust (NAD) day for each pair, were constructed after direct DNA extraction from total suspended particles (TSP) samples. In addition, six aeroallergenic fungi in the atmosphere were also assessed by MSQPCR from October, 2009 to November, 2011. The levels of the airborne culturable fungal concentrations during AD days was significantly higher than that of NAD days (P < 0.005). In addition, the correlation of culturable fungal concentrations with particulate matters equal to or less than 10 pm in aerodynamic diameter (PM10) concentrations was observed to be high (0.775) for the AD days while correlation coefficients of PMio as well as other particulate parameters with airborne fungal concentrations were significantly negative for the NAD days during intensive monitoring periods (May to June, 2008). It was found that during AD days several airborne allergenic fungal levels measured with MSQPCR increased up to 5-12 times depending on the species. Comparison of AD vs. NAD clones showed significant differences (P < 0.05) in all three cases using libshuff. In addition, high proportions of uncultured soil fungus isolated from semi-arid regions were observed only in AD clone libraries. Thus, it was concluded that AD impacts not only airborne fungal concentrations but also fungal communities. (C) 2013 Elsevier Ltd. All rights reserved.
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| [56] |
Bacterial abundance and viability in long-range transported dust [J].
Transports of bacteria in the atmosphere relate to climate and global hydrological cycles by acting as nuclei of ice-cloud formation, and affect the ecosystems and public health in the downwind ecosystems. Here we present quantitative investigations of airborne bacterial cells coupled with LIVE/DEAD BacLight assay in southwestern Japan to show that airborne bacteria were widespread with Asian dust. Total bacterial cellconcentrations in dust varied between 1.0×10 6 and 1.6×10 7 cells m 613 , which were one to two orders higher than those in non-dusty air and were correlated with the concentrations of aerosol particles larger than 1μm. The ratio of viable bacterial cells to total bacterial cells (viability) of bacteria in dust ranged from 16 to 40%, which was quite smaller than the viability in non-dusty air. However viable bacterial cell concentrations in dust, 2.5×10 5 –3.8×10 6 cells m 613 , were similar to or higher than those in non-dusty air. Dust is thus a substantial source of airborne bacterial cells as well as mineral particles. These quantitative results suggest Asian dust is one of the processes for dispersal of airborne bacteria in the global atmosphere.
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| [57] |
Influence of Haze and Dust on the Concentration and Size Distribution of Total Airborne Microbes in Bioaerosols[D] .
霾、沙尘等特殊天气对生物气溶胶中总微生物浓度和粒径分布的影响[D] .
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| [58] |
Viable bacterial aerosol particle size distributions in the midsummer atmosphere at an isolated location in the high desert chaparral [J]. |
| [59] |
Modeling the deposition of bioaerosols with variable size and shape in the human respiratory tract—A review [J]. |
| [60] |
Microscopic and submicron components of atmospheric particulate matter during high asthma periods in Brisbane, Queensland, Australia [J]. |
| [61] |
Granularity distribution of airborne microbes in summer in Beijing [J].北京市夏季空气微生物粒度分布特征 [J]. |
| [62] |
Study on Distribution of Biological Aerosol in Fall and Winter in Qingdao Coastal Region[D] .青岛近海秋冬季生物气溶胶分布特征研究[D] . |
| [63] |
The size distribution of airborne microbes in typical tourist city in southeast China [J].
南方典型旅游城市空气微生物粒径分布特征 [J].
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| [64] |
Concentration and size distribution of viable bioaerosols during non-haze and haze days in Beijing [J]. |
| [65] |
Determination on diameter of atmosphere particles with bacteria over beijing-tianjin area [J].
京、津地区大气带菌粒子径测定 [J].
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| [66] |
Size and seasonal distributions of airborne bioaerosols in commuting trains [J].
Aerobiological studies in commuting trains in northern Taiwan were carried out from August, 2007 until July, 2008. Two six-stage (>7 μm, 4.7657 μm, 3.3654.7 μm, 2.1653.3 μm, 1.1652.1 μm, 0.65651.1 μm) cascade impactors of 400 orifices were used to collect viable bacteria and fungi, respectively. The levels of carbon monoxide (CO), carbon dioxide (CO 2), formaldehyde (HCHO), temperature, and relative humidity in the commuting trains were also recorded during the sampling period. Results show that bacterial concentrations ranged from 25 to 1530 CFU m 613, and averaged 417 CFU m 613. The fungal concentrations ranged from 45 to 1906 CFU m 613, and averaged 413 CFU m 613. Additionally, the highest fractions occurred in the fifth stage (1.1652.1 μm) for both bacteria and fungi. The respirable fractions, R b and R f, for bacteria and fungi were 62.8% and 81.4%, respectively, which are higher than those in other studies. Furthermore, the bacterial concentration reached its highest level in autumn, and its lowest level in winter. However, the fungal concentration was highest in spring and lowest in winter. Though the total bacterial or fungal concentration did not exceed the recommendation standard in Taiwan, the relatively high respirable fraction in commuting trains probably implies a higher adverse health risk for sensitive commuters. This study further conducted multiple regression analysis to determine the relationship of various stage fractions of airborne bacteria and fungi with indoor air pollutants (CO and HCHO) and environmental parameters (CO 2, temperature, and relative humidity). The correlation coefficients of multiple regression analysis for total bacteria and fungi concentrations with indoor air pollutants and environmental parameters were 0.707 ( p < 0.00376) and 0.612 ( p < 0.00471), respectively. There are currently no formally regulated laws for indoor air quality (IAQ) in Taiwan, and this preliminary study can provide references to the Taiwan government on IAQ management.
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| [67] |
Bioaerosols as contributors to poor air quality in Taichung City, Taiwan [J].
Bioaerosols are a type of suspended sediments that contribute to poor air quality in Taiwan. Bioaerosols include allergens such as: fungi, bacteria, actinomycetes, arthropods and protozoa, as well as microbial products such as mycotoxins, endotoxins and glucans. When allergens and microbial products are suspended in the air, local air quality will be influenced adversely. In addition, when the particle size is small enough to pass through the respiratory tract entering the human body, the health of the local population is also threatened. Therefore, the purpose of this study is to attempt to understand the concentration and types of bacteria and the bacteria numbers for various particle size ranges during a study period of June 2005 to February 2006 in Taichung City, Central Taiwan. The results indicate that the total average bacterial concentration by using NA medium incubated for 4802h were 8.002× 10 2 , 1.402× 10 3 , 2.4 × 10 3 and 1.302× 10 3 , 1.902× 10 3 , 3.502× 10 3 02cfu/m 3 for CMES, TRIPS and RFS sampling sites during the daytime and nighttime period of June 2005 to February 2006. Moreover, the total average bacterial concentration by using R 2 A medium incubated for 4802h were 8.5 × 10 2 , 1.502× 10 3 , 2.202× 10 3 and 1.202× 10 3 , 1.702× 10 3 , 2.502× 10 3 02cfu/m 3 for CMES, TRIPS and RFS sampling sites the daytime and nighttime during the same sampling period. The total average bacteria concentration was the same in either NA or R 2 A medium for the same sampling times or sites. The total average bacterial concentration was higher in daytime period than that of nighttime period for CMES, TRIPS and RFS sampling sites. The high average bacterial concentration was found in the particle size range of 0.53–0.7102mm (average bioaerosol size was in the range of 2.1–4.702μm) for each sampling site. Also, 20 kinds of bacteria exceeded levels for each sampling site and were classified as according to shape: rod, coccus and filamentous.
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| [68] |
Size characteristics of fungus allergens in the subtropical climate [J].
Aerodynamic size of fungus spores determines particle motion including settling under gravity, resuspension, and transport by air movement, and where fungus allergens are deposited in the human respiratory tract. Field investigation was conducted to evaluate size characteristics of ambient fungus spores in Taipei city by Andersen six-stage viable sampler in summer and winter seasons. It was found that the highest number of concentrations occurred at nighttime, with a concentration value above 1,700 CFU m0908083, but decreased to a level of 450090009600 CFU m0908083 at daytime. Moreover, large numbers of fungus spores isolated were found to be in the size range of 2.10900093.30204m with a geometric mean diameter in the size range of 1.960900093.400204m. The significant concentration variations between daytime and nighttime samples were demonstrated because of a large number increase in the size range of 1.10900093.3 0204m. In addition, size distributions of the yeasts were found to be remarkably different from those of Aspergillus and Penicillium spp. The observations of size differences among the important fungus allergens demonstrated that there might also be significant differences in their behavior and respiratory deposition.
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| [69] |
The annual bacterial particle concentration and size distribution in the ambient atmosphere in a rural area of the Willamette Valley, Oregon [J].
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| [70] |
Winter time concentrations and size distribution of bioaerosols in different residential settings in the UK [J]. |
| [71] |
Airborne fungi in low and high allergic prevalence child care centers [J].
Fungi exposure has been linked to asthma and allergies among children. To determine the association between fungal exposure and wheeze and rhinitis symptoms, we examined concentrations of culturable indoor and outdoor fungi of various aerodynamic sizes in low and high allergic prevalence child care centers (CCCs) in Singapore. Environmental parameters were also performed for air temperature, relative humidity and ventilation rates, while information on CCC characteristics was collected via an inspection. Most commonly recovered fungi were Penicillium , Aspergillus , Geotrichum , Cladosporium and sterile mycelia with Geotrichum and sterile mycelia amounting to an average of 71.5% of the total airborne culturable fungi studied. Indoor and outdoor total culturable fungi concentrations and those in the size range of 1.1–3.3μm were significantly higher in high allergic prevalence CCCs. When fungal types/genera were compared, indoor and outdoor Geotrichum and sterile mycelia of aerodynamic sizes 1.1–3.3μm were found to be significantly elevated in high allergic prevalence CCCs. Indeed, average geometric mean diameters ( D g, ave ) of indoor and outdoor culturable fungi were consistently smaller in CCCs with high prevalence of allergies than those with low prevalence. We found significant associations of higher fungal concentrations, especially those with smaller aerodynamic sizes in CCCs situated near parks. There were no differences in fungal levels between CCCs with respect to their dampness profile mainly due to high CCC ventilation rates. Since particle size is a factor that determines where a fungi particle deposits in the respiratory tract, this study provides useful information in the etiology of wheeze and rhinitis symptoms among the CCC attending children.
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| [72] |
Three-year investigation of the natural airborne bacterial flora at four localities in sweden [J].
Abstract The concentration of airborne bacteria was recorded during a period of 3 years at four localities: (i) in an agricultural district with an average of 99 (range, 2 to 3,400) bacteria per m3; (ii) in a coastal area with an average of 63 (range, 0 to 560) bacteria per m3; (iii) in a city park with an average of 763 (range, 100 to 2,500) bacteria per m3; and (iv) in a city street with an average of 850 (range, 100 to 4,000) bacteria per m3. At all four localities the bacterial concentrations varied within broad limits, but an annual periodicity with high average counts found during summer and autumn could be seen. The influence of certain meteorological factors on the number of airborne bacteria is also reported. Rain or high relative humidity caused a decrease in the bacterial counts, while high temperature or high wind velocities increased the counts. The particle size distribution for the four localities showed that about 50% of the particles carrying bacteria were larger than 8 micrometer.
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| [73] |
Relationship between airborne microbial and particulate matter concentrations in the ambient air at a Mediterranean site [J]. |
| [74] |
Content, Species and Particle Size Distribution of Atmospheric Microbes in the Polar and Oceanic Boundary Layer and Its Influence Factors[D] .极地与海洋边界层大气微生物的含量、种类和粒径分布及其影响因素[D] . |
| [75] |
Trajectory of aerosol droplets from a sprayed bacterial suspension [J].
Simulated droplet trajectories of a polydispersed microbial aerosol in a laminar air flow regimen were compared with observed dispersal patterns of aerosolized Bacillus subtilis subsp. niger spores in quasilaminar airflow. Simulated dispersal patterns could be explained in terms of initial droplet sizes and whether the droplets evaporated to residual aeroplanktonic size before settling to the ground. For droplets that evaporated prior to settling out, a vertical downwind size fractionation is predicted in which the microbial residue of the smallest droplets settles the least, and is found in the airstream at about sprayer height, and progressively larger droplet residues settle to progressively lower heights. Observations of spore particle size distributions downwind from a spray source support the simulation. Droplet and particle size distributions near the source had three size fractions: one containing large, presumably nonevaporated droplets of greater than or equal to 7 microns in diameter, and two smaller fractions, with diameters of 2 to 3 microns (probably the residue of droplets containing more than one spore) and 1 to 2 microns (probably the residue from single-spore droplets). As predicted by the simulation, the aerosol settled and progressed downwind, with the number of small droplets and particles increasing in proportion to the height and distance downwind.
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| [76] |
Factors in the production, release and viability of biological particles [M] |
| [77] |
SPM and fungal spores in the ambient air of west Korea during the Asian dust (Yellow sand) period [J]. |
| [78] |
Distribution of Airborne Microorganisms in Yellow Sands of Korea [J].
Abstract Distribution of airborne microorganisms was determined with two different types of air samplers, the Anderson cascade sampler and the Aerobioscope sampler, in the vicinity of Taejon. The size distribution of particles carrying bacteria and fungi was concurrently measured. The concentration of detected viable airborne particles was greatly varied. It was observed that the number of microbial particles increased in April and October. The most size of particles carrying bacteria was larger than 4.7 渭m in mean aerodiameter, which made up 69.8% of the total particle fraction. About 63.2% of fungi-carrying particles were smaller than 4.7 渭m in aero-diameter. The distribution of particles on Yellow Sand Phenomena-days was also analyzed. The number of fine particles having mass median aero-diameter from 1.0 to 10 渭m increased on Yellow Sand Phenomena days to about 6 times that on normal days and the number of colony forming unit (CFU/m3) of airborne bacteria also increased by 4.3 times in April. The results from the Anderson sampler showed that the concentration of bacteria increased greatly on the fraction of fine particles ranging from 0.6 渭m to 4.7 渭m in diameter. Unlike the increase in bacterial flora on Yellow Sand Phenomena days, the fungal concentration slightly decreased and showed a normal size distribution pattern. This study suggests that a long-range transmission of bacteria results from bacteria adsorbing onto the fine particles during the Yellow Sand Phenomena.
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| [79] |
Particle size distribution of airborne microorganisms and pathogens during an intense African dust event in the Eastern Mediterranean [J].
In the summer of 2005, while Atlantic hurricanes battered coastlines from Cuba to Mexico, the...
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| [80] |
Characterization of microbial community during Asian dust events in Korea [J].
An Asian dust event, also sometimes known as a Yellow Sand event, is a seasonal meteorological phenomenon affecting East Asia, typically in the early spring. Because of the significant ecological and health effects of these events on East Asia, and the large amount of dust that is transported from the desert in China to Korea and Japan, these events have been receiving increased attention. It is likely that these storms often provide long-range transport to various microorganisms. However, despite a certain level of attention to the chemical analysis of these storms, microbiological studies of Yellow Sand dust have been scarce. We collected a total of 30 microbiological air samples using a PM 2.5 cyclone sampler in Seoul, Korea from April 2007 to March 2008. Six of these samples were collected during Yellow Sand events, while 24 were from non-Yellow Sand events. Chemical analysis was performed on the samples using a thermal鈥搊ptical transmittance (TOT) method. Total nucleic acids were also extracted, and the 16S rDNA was amplified by PCR and analyzed by denaturing gradient gel electrophoresis (DGGE). Dendrogram analysis, based on DGGE, indicated that the microbial profiles from the Yellow Sand were distinctive from those of the non-Yellow Sand samples. Microorganisms identified in Yellow Sand samples included Aquabacterium sp., Flavobacteriales bacterium sp., Prevotellaceae bacterium sp., and others, whereas microorganisms in non-Yellow Sand samples included Propionibacterium sp., Bacillus sp., Acinetobacter sp., and others . These results suggest that, as a result of Yellow Sand events, humans in the affected regions are exposed to communities of microorganisms that might cause various adverse health effects.
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| [81] |
Microbiological and meteorological analysis of two Australian dust storms in April 2009 [J].
Dust is an important source of bioaerosols including bacteria. In this study, the microbiology and meteorology of specific dust storms in Australia were investigated. The samples were collected from two dust events in April 2009 that were characterised by intense cold fronts that entrained dust from the highly erodible and drought-stricken Mallee and Riverina regions of Victoria and central NSW. In the first storm, the dust travelled eastward over Canberra and Sydney, and in the second storm, the dust travelled east/southeastward over Canberra and Melbourne. Rain fell on both cities during the second dust storm. Dust and rain samples were collected, cultured, and the composition compared using polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE). Multiple bands were evident on DGGE indicative of a diverse microflora, and identification of several bands confirmed the presence of multiple genera and species representing three phyla. Numerous bands represented Bacillus species, and these were present in multiple dust samples collected from both Canberra and Melbourne. Interestingly, the microflora present in rain samples collected in Canberra during the second dust storm was quite different and the DGGE banding patterns from these samples clustered separately to most dust samples collected at the same time. Identification of several DGGE bands and PCR products from these rain samples indicated the presence of Pseudomonas species. These results indicate that Australian dust and rain have a diverse microflora and highlights the contribution of dust events to the distribution of microbes in the environment.
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| [82] |
Variations in the structure of airborne bacterial communities in Tsogt-Ovoo of Gobi desert area during dust events [J]. |
| [83] |
UV-tolerant culturable bacteria in an Asian dust plume transported over the East China Sea [J].
Airborne bacteria are dispersed along with Asian dust and have various influences on atmospheric characteristics, downwind ecosystems, and public health. In this study, aircraft observations were conducted during Asian dust passage and non-dust conditions over the East China Sea in December 2010, and the composition of culturable bacteria within the dust was investigated using culture-based gene analysis. The 16S rRNA gene analysis revealed that the 34 cultured strains isolated from the transported dust could be grouped into Bacillales and Actinomycetales. Highly tolerant endospore-forming bacteria (25 isolates) were predominant in the composition. On the other hand, all non-endospore-forming bacteria (9 isolates) were gram-positive bacteria with high guanine and cytosine contents, which have substantial ultraviolet (UV) resistance. Thus, the isolated culturable bacteria were strains having some tolerance for exposure to UV radiation. Although the atmosphere is an extreme environment for bacterial survival, Asian dust can facilitate atmospheric dispersion of culturable bacteria that are resistant to the harsh ambient air environment.
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| [84] |
Sunlight ultraviolet and bacterial DNA base ratios [J]. |
| [85] |
Bioprocess of Kosa bioaerosols: Effect of ultraviolet radiation on airborne bacteria within Kosa (Asian dust) [J]. |
| [86] |
The effects of transported Asian dust on the composition and concentration of ambient fungi in Taiwan [J]. |
| [87] |
Cultivable Fungi in Spring sandy dust air in Qingdao Coastal Region and their potential health risk [J].青岛近海春季沙尘天空气可培养真菌及其潜在健康风险 [J]. |
| [88] |
Phylogenetic diversity and vertical distribution of a halobacterial community in the atmosphere of an Asian dust (KOSA) source region, Dunhuang City [J]. |
| [89] |
Phylogenetic analysis of atmospheric halotolerant bacterial communities at high altitude in an Asian dust (KOSA) arrival region, Suzu City [J]. |
| [90] |
Detailed identification of desert-originated bacteria carried by Asian dust storms to Japan [J].
Several halotolerant bacteria were isolated from dust allowed to settle passively on saline medium in Higashi-Hiroshima, Japan during Asia dust events in 2005–2006. The primary identification, based on the sequence similarity of the 16S rRNA gene, revealed that these isolates were strains of Bacillus subtilis , B. licheniformis , Staphylococcus epidermidis , Gracillibacillus sp., and Halomonas venusta . A parallel investigation carried out on desert sand collected directly from sand dunes in Dunhuang, Gobi Desert, China resulted in the revivification of seven bacterial strains that were highly identical to the B. subtilis and B. licheniformis strains obtained in Higashi-Hiroshima (99.7 and 100% of 16S rDNA sequence similarity, respectively). A subsequent genetic analysis on the group of B. licheniformis isolates based on the universally house-keeping genes, gyrB and parE , revealed high sequence similarities in both genes among the strains of both locations (99.0–99.4%), which clustered them in a monophyletic line. Phenotype characterized by numerical taxonomy for 150 physiological tests confirmed the close relatedness between strains (similarity coefficient S SM 02=0296.0%). The remarkable agreement between phenotype and genotype of the bacterial isolates allows us to conclude that there may have been an aerosolized dispersion of a Gobi Desert B. licheniformis by dust storms to Japan. This study provides evidence of microbial transport by yellow dust events in North-East Asia.
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| [91] |
Atmospheric movement of microorganisms in clouds of desert dust and implications for human health [J]. |
| [92] |
Quorum sensing as a method for improving sclerotiorin production in Penicillium sclerotiorum [J].
Quorum sensing has been extensively studied in the bacterial kingdom but little is known about it in filamentous fungi. γ-Butyrolactones have been established as quorum sensing molecules in Gram-negative bacteria (as acyl-homoserine lactones) and Gram-positive bacteria (as A-factor) and they are present in many filamentous fungi (e.g. as butyrolactone I in Aspergillus terreus ). This study investigates possible role of multicolic acid (and related derivates) as quorum sensing molecule(s) in P. sclerotiorum and its effect on the production of secondary metabolite sclerotiorin. Exogenous addition of an ethyl acetate extract of supernatants from P. sclerotiorum IMI 104602 (Strain M) at 4802h of growth resulted in maximum sclerotiorin yield of 8.502mg02g 611 in Strain M at 16802h post-inoculation, a 1.8-fold increase as compared to the control. Addition of spent medium containing γ-butyrolactone molecules from this strain to P. sclerotiorum IMI 040574 (Strain S) resulted in 6.4-fold increase in sclerotiorin yield at 16802h post-inoculation without causing a significant change in the biomass production ( p 02>020.05) or carbohydrate consumption rate ( p 02>020.05). The results presented here suggest that multicolic acid (and related derivatives) function as quorum sensing molecules in the filamentous fungus P. sclerotiorum .
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| [93] |
Assay for fluorescein diacetate hydrolytic activity: Optimization for soil samples [J].
With the increased interest in integrated soil bioecosystem studies, there is a need to have a method of measuring overall microbial activity potential. Hydrolysis of fluorescein diacetate [3′,6′-diacetylfluorescein (FDA)] has been suggested as a possible method because the ubiquitous lipase, protease, and esterase enzymes are involved in the hydrolysis of FDA. Following hydrolysis of FDA, fluorescein is released and can be measured spectrophotometrically. Our objective was to optimize the assay for FDA hydrolytic activity in soil samples and determine the kinetic parameters involved in this reaction. The optimized method involves extraction and quantitative measurement of the fluorescein released when 1.0 g of soil is incubated with 50 ml of 60 mM Na–phosphate solution (buffered at pH 7.6) at 37 °C for 3 h. Results showed that FDA hydrolysis was optimum at buffer pH 7.6 and the soil enzymes were denatured at temperatures above 60 °C. Three soils were used to optimize this method: Heiden clay, Raub silt loam, and Cecil sandy loam. This procedure is simple, precise, and can be used in commercial soil testing laboratories to determine general microbial activity and as a soil quality indicator.
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| [94] |
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| [95] |
Microbial activity levels in atmospheric bioaerosols in Qingdao [J].
Bioaerosols are an important subgroup of atmospheric aerosols, and microorganisms are a major component of bioaerosols. Microbial activity can affect climate change, human health and environmental processes. We developed a diacetate (FDA) hydrolysis method to measure microbial activity in bioaerosols. A large number of preliminary experiments were used to optimise the experimental conditions and guarantee the applicability of this assay to environmental bioaerosol samples. The level of microbial activity in the atmosphere in the Qingdao coastal region was measured using the FDA method in May and from September to December 2012. The microbial activity in bioaerosols varied from 10.7 to 85.8聽ng/m 3 sodium fluorescein, with an average of 30.2聽ng/m 3 . The microbial activity in bioaerosols displayed monthly variations, with the highest value in May. However, the activity showed no significant correlation with temperature, relative humidity and wind speed. Thus, further study is needed to elucidate the major factors and mechanisms that affect microbial activity in the atmosphere.
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