地球科学进展  2018 , 33 (8): 783-793 https://doi.org/10.11867/j.issn.1001-8166.2018.08.0783

综述与评述

海洋微生物气溶胶的丰度、群落结构及影响机制

王芳慧, 陈莹*, 王波, 李好文, 周升钱

复旦大学环境科学与工程系,上海 200438

Abundance and Community Structure of Airborne Microorganisms over the Ocean and Their Influencing Mechanisms

Wang Fanghui, Chen Ying*, Wang Bo, Li Haowen, Zhou Shengqian

Department of Environmental Science and Engineering, Fudan University, Shanghai 200438, China

中图分类号:  P735

文献标识码:  A

文章编号:  1001-8166(2018)08-0783-11

通讯作者:  *通信作者:陈莹(1975-),女,江苏镇江人,教授,主要从事气溶胶生物地球化学研究.E-mail:yingchen@fudan.edu.cn

收稿日期: 2018-04-2

修回日期:  2018-06-6

网络出版日期:  2018-08-10

版权声明:  2018 地球科学进展 编辑部 

基金资助:  国家重点研发计划项目“海洋生源活性气体在大气中的迁移转化及气候效应”(编号:2016YFA0601304)国家自然科学基金项目“东海微生物气溶胶的丰度和群落结构变化及影响机制”(编号:41775145)资助.

作者简介:

First author: Wang Fanghui(1991-), female, Puyang City, He'nan Province, Ph. D student. Research areas include airborne microorganisms. E-mail: 16210740014@fudan.edu.cn

作者简介:王芳慧(1991-),女,河南濮阳人,博士研究生,主要从事微生物气溶胶研究.E-mail:16210740014@fudan.edu.cn

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摘要

微生物气溶胶在微生物传播和生态系统多样性维护上发挥着核心作用,并且可成为有效的冰核(IN)和云凝结核(CCN)对气候产生显著影响。海洋是大气中微生物的重要源和汇,然而,关于海洋微生物气溶胶丰度和多样性分布的信息知之甚少。系统梳理了已研究报道的海洋微生物气溶胶的丰度、粒径分布和群落结构,以及影响其分布的各种环境和气象因素;列出了微生物气溶胶的常用测定方法及发展态势;最后指出该研究领域亟待解决的问题和未来方向,包括建立标准的海洋微生物气溶胶采集和处理技术,增加开阔大洋的航次观测资料,采用先进的分子生物学技术与传统分析手段结合等。为后续海洋微生物气溶胶的深入研究,揭示其来源、活性、气候和生态效应提供了全面重要的信息。

关键词: 微生物气溶胶 ; 海洋气溶胶 ; 群落结构 ; 丰度 ; 影响因素

Abstract

Airborne microorganisms play an essential role in the microbial propagation and maintenance of the ecosystem diversity, and also significantly affect the climate by acting as effective Ice Nucleus (IN) and Cloud Condensation Nuclei (CCN). The ocean is a vital source and destination for airborne microbes. Nevertheless, little information has been obtained on the distribution of abundance and diversity of airborne microorganisms over the ocean. This paper systematically reviewed the abundance, size distribution, and community structure of airborne microorganisms over the ocean, as well as various environmental and meteorological factors that control the distribution of microbes in marine aerosols. The commonly used methods for detecting airborne microorganisms and their development prospects were also discussed. We pointed out that sampling and detection of extremely low concentration microorganisms in marine aerosols are key problems to be solved in this field, and future research directions include the increase of the cruising observation in open oceans and combination of advanced molecular techniques and other traditional methods. This paper provides extensive and crucial information for subsequently in-depth research on airborne microorganisms over the ocean, revealing their sources, activities, climate and ecological effects.

Keywords: Airborne microorganism ; Marine aerosol ; Community structure ; Abundance ; Influencing factors.

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王芳慧, 陈莹, 王波, 李好文, 周升钱. 海洋微生物气溶胶的丰度、群落结构及影响机制[J]. 地球科学进展, 2018, 33(8): 783-793 https://doi.org/10.11867/j.issn.1001-8166.2018.08.0783

Wang Fanghui, Chen Ying, Wang Bo, Li Haowen, Zhou Shengqian. Abundance and Community Structure of Airborne Microorganisms over the Ocean and Their Influencing Mechanisms[J]. Advances in Earth Science, 2018, 33(8): 783-793 https://doi.org/10.11867/j.issn.1001-8166.2018.08.0783

1 引 言

一次源生物气溶胶颗粒物(Primary Biological Aerosol Particles, PBAP)为源于生物有机体的固体空气颗粒物,包括细菌、古生菌、真菌孢子、花粉、病毒、藻类、蓝细菌、活性生物分泌的有机物质,以及植物或动物的碎片和碎屑等[1]。海洋PBAP可从海洋微表层释放,或从陆地传输而来[2],在释放源的几千公里外沉降[3],对生态和气候系统具有重要影响。海洋微生物气溶胶最初发现于1933年,美国农业部在从缅因州到丹麦的航班收集的空气样本中发现了真菌孢子、藻类和硅藻[4]。海洋空气中的微生物可以影响有机物质的生物转化、碳循环和光化学反应,可作为冰核(Ice Nuclei, IN)和云凝结核(Cloud Condensation Nuclei, CCN)影响气候过程,因此受到研究者们越来越多的重视[5,6,7,8,9,10]。研究表明从海洋云水中分离的活性细菌与生物反应和光化学具有联系[8,11]。海洋微生物气溶胶中可作为IN的主要为小的细菌和古生菌以及由微生物分泌的有机质,这些被认为是远海区域的重要IN[12,13];粒径大于2 μm的生物颗粒可作为大的CCN,例如真菌孢子,形成快速降落的大液滴[14,15]

已有研究结果指出,陆地上空大气边界层中细菌和真菌孢子的平均丰度分别约为1.9×104 cells/m3和2.4×104 cells/m3[12],但对远洋空气中微生物浓度的观测相对较少[3]。实验室模拟和现场测定表明通过海洋泡沫破裂机制产生的飞沫中细菌浓度远超过海洋表层水中细菌的浓度[16]。全球海洋调查研究了悬浮在太平洋、大西洋、东海、南海和印度洋空气中微生物的群落结构、丰度、通量和来源,数据显示海洋是海洋大气中微生物的主要来源,大气传输可对海洋表面微生物的分散及洲际传输起到重要作用[17]。近年来,学者们对不同海拔高度空气中细菌群落之间的差异进行了研究分析,并评估污染对不同大气高度微生物群落结构的影响[18,19]。已有研究采集海洋上空3 000,1 000和10 m海拔高度的微生物气溶胶样本,并利用克隆文库方法测定样本中具有属于蓝细菌和α-变形菌纲的海洋源细菌种类[20]。当前少量的研究[21,22]使用新一代测序技术(高通量测序技术),发现不同来源的气溶胶和沙尘具有不同的微生物群落组成,可对人类的身体健康、生物地球化学循环和生态环境造成不利影响。随着高通量测序技术的快速发展,将有越来越多的研究采用这项技术进行分子生物水平上细菌气溶胶的分类测定[22,23]

本文收集世界不同海域微生物气溶胶的信息,对其丰度和群落结构分布以及受环境和气象因素的影响进行综合分析,指出世界各海区空气中细菌群落结构的特征,探讨不同环境和气象条件下细菌气溶胶的粒径分布、浓度、多样性和群落结构的差异,总结目前较为先进的微生物气溶胶群落结构测定技术。海洋微生物气溶胶的研究尚未建立标准的采样和分析方法,这是该研究领域关注的一个重要科学问题[24]。鉴于海洋空气是微生物极度稀释的环境,为了浓缩气溶胶的含量,并增加发现稀有微生物的可能性,需要高流量且能保护微生物活性的采样机制对其进行高效富集,以便利用分子生物学技术进行后续分析。高时间和空间分辨率也是衡量采样技术的一个重要标准。已有研究大部分在沿海地区或通过飞行器进行空气样品采集,只有少量远海区域的随船样品收集研究[25,26],后续需开展更多开阔大洋空气中微生物的航次观测,从而深入认识其浓度水平、多样性、粒径分布、来源和气候效应。

2 测定方法

2.1 微生物气溶胶丰度的测定

1900—1980年,大部分研究采用琼脂培养法计数空气微生物。传统的基于培养(Colony-Forming Unit, CFU, 菌落形成单位)计数的方法通常不能准确地测定空气环境中微生物的浓度,这是由其较低的可培养水平(<1%)和采样遭受的压力所致。最常见的测定微生物总数的方法是采用荧光显微镜直接计数法,样品经荧光染料(例如活死细胞染料SYTO® 9和Propidium iodide,PI[27,28]、4',6-diamidino-2-phenylindole, DAPI或吖啶橙[29])预处理,所有含核酸的颗粒物均可被染色,而后进行人为计数并将染色颗粒的大小和形态考虑在内[30]。最近几年,诸如荧光原位杂交(Fluorescence In Situ Hybridization,FISH)和流式细胞术(Flow Cytometry, FCM)等分子技术被广泛应用于微生物气溶胶丰度和活性的测定,以便评估它们对公共健康、下风向区域生态系统和大气现象的影响[31,32]。FCM已成为研究环境中PBAP的一个重要工具,可让微生物气溶胶的基因识别达到种的水平,同时计量每类微生物的数量。采用荧光色素SYBR Green I和活死细胞染料SYTO® 9、PI染色,并结合FCM技术已被广泛用于评估水生环境和微生物气溶胶中原核和真核微生物的浓度和活性[31,33,34]

2.2 微生物群落结构的测定

1988年,聚合酶链式反应(Polymerase Chain Reaction, PCR)的出现极大地促进了微生物气溶胶研究领域的发展[4]。PCR被称为无细胞系统的分子克隆或基因扩增技术,可使少量目标DNA扩大100万倍以上,从而极大地增强了DNA的被检测能力。实时定量PCR(qPCR)已被广泛应用于生物生态领域,量化不同环境样品中微生物的丰度、类群表达和功能基因标记[35]。21世纪前后10年,克隆文库(Clone libraries)、桑格测序(Sanger method)、变性梯度凝胶电泳(Denaturing Gradient Gel Electrophoresis, DGGE)、末端限制性片段长度多态性(Terminal Restrictive Fragment Length Polymorphism, T-RFLP)等分子生物方法被大量应用于微生物气溶胶多样性的研究[36,37,38]。虽然这些方法均可提供关于被检测微生物群落结构的一般信息,但不足以进行有意义的比较[21]。例如,DGGE对稀有细菌的流行和多样性的评估不充分,这是由于当引物定向于广泛的细菌种类时,很容易遗漏稀有的细菌类群。

随着新一代测序技术的快速发展,例如,454焦磷酸测序、Illumina MiSeq及Illumina HiSeq测序平台,从PCR扩增中获得持续增加的大量序列数据[39,40],更长序列的读取为了解细菌群落结构提供更高的分辨率,稀有的细菌类群也可被检测到[39]。Solexa/Illumina基因组分析仪已被应用于很多环境研究中,与454焦磷酸测序相比,Solexa/Illumina测序平台的成本平均降低10%,而且具有更高的数据输出[41,42]。随着时间推移,HiSeq测序技术不断提升,现可提供2×150个碱基的读取长度,约200 Gb的输出。目前,MiSeq平台对16S rRNA基因测序研究的应用相对HiSeq测序平台具有更大潜力,因其可提供更长序列的读取,执行相对较高的分辨率,并且对个体研究者而言经济上相对可行。MiSeq和HiSeq测序最近已经被成功地应用于微生物气溶胶群落结构特征的研究及病原体的检测[38]。此外,宏基因组学方法可定向于微生物群落组成的研究,并为群落结构(种类、丰度和分布)及其功能(代谢)潜力提供相对准确的实验结果。

3 海洋微生物气溶胶的丰度

海洋空气中细菌的浓度比陆地空气低100~1 000倍[2]。沿海区域受陆地源和海洋源的共同影响,微生物气溶胶的浓度和活性微生物的数量都要高于开阔大洋,例如,西北太平洋、楚科奇海、加拿大盆地和北冰洋的中心区域[25]。Harrison等[29]和Grffin等[43]根据沿海和海洋站点空气中总细菌浓度的季节平均值和标准偏差计算得出海洋和沿海地区空气总细菌浓度的最佳、最高、最低估值分别为1×104,8×104,1×101和7.6×104,1.3×105,2.3×104 CFU/m3。对大西洋中脊一个钻探站点(45°W,14°43'~15°44'N)的观测佐证了此估算,其可培养细菌的平均浓度为16.4 CFU/m3,浓度变化与沙尘密切相关,表明沙尘传输是海洋空气细菌的一个重要来源[43]。海洋源释放的细菌平均大气停留时间比陆地表面短,它们很快会被海洋上空形成的降水清除,使得一般海洋空气中总的细菌和可培养细菌的浓度比陆源气团低[2,29,43]

Mayol等[3]测量北大西洋一个横断面(约17°N)的低层大气微生物丰度,从气象数据中获得微生物的海气交换源估计,每平方米海洋表层水进入大气边界层的微生物负荷为6.0×104~1.6×107个微生物,每平方米表层海水每天有数百万的微生物离开或进入海洋,这表明海气微生物交换是一个动态的过程。北大西洋大气边界层中原核生物的丰度为103~104 cells/m3,真核微生物的丰度为102~104 cells/m3。亚洲沙尘事件中,日本沿海城市金泽市空气样本中细菌细胞的总浓度变化范围为7.5×104~2.0×107 cells/m3,而在非沙尘事件天气减少到7.7×104 cells/m3[30]。Cho等[44]采集东海的气溶胶和表层海水样品,测得空气原核生物的丰度为0.7×105~1.2×105 cells/m3。Zweifel等[19]采集瑞典和丹麦沿海云凝结发生高度的气溶胶样品,细胞计数得出总细菌浓度的范围为4×101 ~1.8×103 cells/m3

马拉斯皮纳2010环球航行探险(Malaspina 2010 Circumnavigation Expedition)[15]对全球海洋(40°S~40°N)空气原核生物(细菌和古生菌)和单细胞真核生物(真菌孢子、异养和自养原生生物)的丰度进行研究分析,发现海洋大气边界层中微生物的丰度具有明显的空间差异,原核生物细胞浓度的变化范围为5×102~8×104 cells/m3,单细胞真核生物浓度为1×102~1.8×105 cells/m3,均值与估计的海洋空气微生物丰度一致[12]。单细胞真核生物丰度在远离陆地时呈下降趋势,最大值出现在北大西洋和东太平洋,这可能是由于采样时间分别为夏季和春季,这是非洲沙尘和亚洲沙尘分别传输至大西洋和太平洋最为频繁的季节,沙尘携带的微生物可影响不同环境中人类的健康和微生物的群落结构及丰度[45]。表层海水中原核生物丰度的典型范围为0.5×106~1.5×106 cells/mL,开阔大洋的风速条件一般大于6 m/s,据此可估算出海洋对微生物气溶胶丰度的贡献。研究计算显示空气原核生物和真核生物在大气中17~35天的存留时间里可经历几千公里的传输,大气在陆地微生物的洲际传输和海洋微生物的远距离扩散上扮演着重要角色,海岛可作为微生物跨海传输的“驿站”[15]

海洋空气微生物丰度的研究目前主要集中在沿海或近海区域,并在向远洋区域拓展。随着先进采样技术的发展和更多科考调查航次的开展,结合沙尘事件等不同的气象和环境条件及海洋微表层(Sea-surface Microlayer, SML)微生物的研究,将会获得更多开阔大洋微生物气溶胶的信息,未来将能更清楚地了解海洋微生物气溶胶对生物地球化学循环过程的影响。

4 海洋微生物气溶胶的粒径分布

目前研究很大程度上忽视了不同粒径微生物气溶胶的数量和群落组成,而粒径决定微生物传播的分散性和深入人体呼吸道的程度,从而影响气候变化和人体健康[46]。海水中主要的微生物质包括病毒(20~200 nm)、细菌(0.2~1 μm)、浮游植物(0.5~500 μm)、浮游动物(3 μm~1 cm)和非活性碎片(即生物质的分解产物),分散在几米水深的气泡在上升过程中,会携带这些生物质到海洋微表层,通过泡沫破裂机制将微生物质喷射到空气中[47]。通过对东地中海沿海城市伊拉克利翁,克里特岛(Heraklion, Crete)空气中微生物粒径分布的测定[46],发现海洋和生态系统中常见的微生物类群,例如,厚壁菌门这些形成孢子的细菌主要存在于大颗粒物(>3.3 μm)中,放线菌门(通常在土壤中被发现)和拟杆菌门(广泛分布在环境中)在小粒径颗粒物(<3.3 μm)中丰度更大。海盐是粒径大于1 μm的一次源海洋气溶胶的主要物质,然而,水不溶性有机物质(Water Insoluble Organic Matter, WIOM,包括细菌、真菌、微藻、病毒、有机物质)是北大西洋亚微米海洋气溶胶(<0.5 μm)的主要组成部分[48,49,50],一次藻华期间测得北大西洋空气中45%~73%的亚微米气溶胶物质由WIOM组成[51]

分级撞击采样器可采集不同粒径范围颗粒物,获得细菌气溶胶的粒径分布及数中值,陆地上空微生物气溶胶的粒径约为4 μm,沿海约为2 μm[52],海洋细菌一般比陆地细菌小,生物体积通常在0.036~0.073 μm3,对应的当量球径是0.20~0.26 μm,带有空气细菌的颗粒物明显大于1 μm粒径大小的细菌[52,53]。海洋微生物气溶胶的粒径分布受海洋源和陆地源的共同影响,研究发现瑞典、美国和中国地区[4]的大部分细菌存在于粗颗粒物中(>2.1 μm),其粒径分布出现季节或日变化趋势,例如,俄勒冈州的白天和夏季,总细菌的浓度最高,其中可培养的细菌在最大粒径颗粒物(>7 μm)中丰度最高,而在小于1.1 μm粒径的颗粒中丰度最低,这可能是由于日晒导致大气湍流使得地面农业源(大颗粒)的贡献增加所致[52]。在中国近海、西北太平洋和加拿大盆地中,最高比例的空气真菌主要分布在2.3~3.0 μm的粒径范围内,大颗粒物不适于长途传输。但事实上,由于干燥、温度和紫外线辐射这些环境因素的影响,微生物常利用海盐或粗颗粒物包裹以保护自己[25]

微生物的组成和丰度在不同粒径颗粒物中的分布是海洋微生物气溶胶研究的重点和难点,对于了解其生物地球化学作用具有重要意义。海洋微表层是大气中微生物的重要来源,对其微生物的组成、粒径分布及相关生物地球化学过程已有大量研究[54],但关于海洋气溶胶不同粒径范围内微生物的组成和丰度的信息还相当缺乏。目前,少数研究对沿海区域微生物气溶胶的粒径分布及时空变化展开了观测分析,而受陆源影响较小的开阔大洋上空微生物气溶胶的粒径分布,受不同气象和环境因素的影响作用,以及不同粒径颗粒物中微生物的活性等都有待进一步研究。

5 海洋微生物气溶胶的群落结构

目前,关于海洋空气微生物多样性的研究相对较少,海洋微生物气溶胶的种群组成尚无明确定义[21]。Seifried等[1]的研究结果指出,从北海(North Sea)经斯卡格拉克海峡(Skagerrak)和卡特加特海峡(Kattegat)到达波罗的海(Baltic Sea)这片海域的细菌气溶胶高度多样化(图1),最丰富的门类主要有变形菌门(49.3%)、拟杆菌门(22.9%)、放线菌门(16.3%)和厚壁菌门(8.3%)。蓝藻细菌占所有细菌读取序列的1.5%,丰度最高的属级分类为鞘氨醇单胞菌属,是从北海至波罗的海采集的所有样本中的主导类群(Operational Taxonomic Unit,OTU),已知这种细菌属广泛存在于海洋和水环境中[29,36,55]。此外,潜在的冰核细菌假单胞菌属(Pseudomonas)和泛生菌属(Pantoea)也被测定发现,海洋沉积物中相关细菌的出现也表明海滩或海岸侵蚀过程对形成微生物气溶胶的重要性。图1图2分别展示了全球海洋细菌气溶胶在门和纲分类水平上群落结构的空间分布,从图中可看出目前微生物气溶胶多样性的研究主要集中在地中海、韩国和日本等沿海或近海区域,而开阔大洋空气微生物多样性的研究还未充分开展,这主要是由于地理环境采样困难所致。

图1   全球海洋上空细菌气溶胶在门分类水平上的群落结构分布

Fig.1   Distribution of community structure of airborne bacteria at the phylum level over global oceans

图2   全球海洋上空细菌气溶胶在纲分类水平上的群落结构分布

Fig.2   Distribution of community structure of airborne bacteria at the class level over global oceans

通过比较表层海水和空气微生物的群落组成可了解微生物气溶胶的来源,Cho等[44]采集位于韩国东部海域的东海气溶胶和表层海水样品,测定发现微生物气溶胶的16S rRNA基因的部分序列主要由γ-变形菌纲和拟杆菌类群组成,气溶胶中一半以上细菌OTUs属海洋源,由此表明表层海水可能是海洋空气细菌的主要来源。马拉斯皮纳2010环球航行探险[15]检测到海洋大气边界层中约25%和42%(中值)的原核生物分别来自海洋和陆地,其中主导的β-变形菌纲、放线菌纲和芽孢杆菌纲未出现在表层海水中,但大量存在于淡水和陆地环境(图2)。海洋气溶胶中检测到源自远距离区域的属广古菌门(Euryarchaeota)的MSP8 进化分枝序列,这表明海洋空气原核生物可进行长距离的空气传输[44]

通过层次聚类分析法可在目水平上对细菌的群落结构进行分类,Xu等[56]在泰山采集的一些云水样品中发现伯克氏菌目(Burkholderiales)和肠杆菌目(Enterobacteriales)等源于海洋的菌种,且研究发现泰山采集的云水样品受来自黄海的气团影响时,蓝细菌的丰度比受陆地气团影响时更高,泰山采集的云水样品与陆地源细菌相比,海洋源细菌种群主要在云水中增加,这表明海洋可能是云层中细菌的主要来源[10]。Innocente等[57]的研究区域威尼斯(Venice)具有大多数沿海地区常见的海陆风,其代表一种复杂的大气环流模式,风来自东北和东南方向,影响着天气、气候动力学以及海洋和陆地之间污染物的形成和传输。在威尼斯采样站点Via Lissa冬季检测出属海洋细菌的交替单胞菌科(Alteromonadaceae),当空气团来自意大利南部和亚得里亚海(为地中海的一个海湾)时,其特征是富集了海洋离子Cl-,Na+和Mg2+,以及海洋细菌红杆菌科[58]

由于直接收集高海拔空气微生物细胞需要复杂的采样技术,自由大气层中空气微生物的群落较少被研究。Maki等[18]在日本的能登半岛区域(37.5°N, 137.4°E)用气球和一架飞机分别在10,1 000 和3 000 m海拔高度上空进行对流层气溶胶样品的采集,研究发现10和1 000 m高度处均存在典型海洋源的蓝细菌,而3 000 m高空未检测到该类群,10 和1 000 m空气中检测到属α-变形菌纲的相对丰度分别为15.7%和22.4%的深海细菌SAR进化分枝[18,20]。气团后向轨迹显示3 000 m高处气团3天前源于中国沙尘区域,而后快速经日本海传输至能登半岛,因此,3 000 m高处的空气细菌可能由中国陆地或沙尘环境中的细菌类群主导。蓝细菌的序列在海拔3 000 m以上高度收集的云水样本中占据主导地位,表明了蓝细菌的大气传输[59]。蓝细菌中的聚球藻属(Synechococcus)可通过光合作用消除过氧化物来抵抗紫外线辐射和氧化压力[60],在东中国海和日本海发现的蓝细菌主要为聚球藻属[37]

6 海洋微生物气溶胶的气候效应

近年来,海洋环境气溶胶中的微生物对大气化学、云形成和降雨的影响正在受到越来越多的重视。海洋生物活动能够直接或间接产生气溶胶(即海洋生物源气溶胶)并通过一系列复杂过程影响气候的研究已成为海洋科学与气候变化研究的前沿课题[61]。大型国际合作研究计划“低层大气和上层海洋研究(The International Surface Ocean-Lower Atmosphere Study, SOLAS)”以海洋中深度100 m以上的水层和1 000 m以下的大气边界层为主要研究对象,通过多学科的交叉研究,揭示海洋与大气相互作用的物理和生物地球化学过程耦合及其在气候变化中的作用[62,63]。海洋微生物气溶胶对气候系统影响的不确定性很大程度上集中在海洋层积云,这是基于全球区域范围的主要云类型,这些云可产生强烈的负辐射效应[64]。空气细菌所含的蛋白质可作为冰核,潜在地影响云的形成[6]和生物地球化学循环[22,23,65]。Amato等[66]的研究发现,从海洋释放的细菌可转入到对流层云滴中,采集的受海洋影响的云水样本中假单胞杆菌属的丰度比无海洋影响的云样本高9倍。

海洋源是有机碳进入大气的一个主要来源[49,67],通过加权气团后向轨迹分析,并结合海洋站点的观测结果显示有机碳气溶胶质量与海洋叶绿素浓度呈一定相关性。在高生物活性季节,亚微米海洋气溶胶主要由非水溶性有机质组成,可能源于海洋一次源气溶胶的释放[68],对气候系统有重要影响,特别是在远洋区域。这一假设得到Meskhidze等[69]的研究支持,即南大洋中有效的云滴半径与海洋浮游植物的浓度显著相关,海洋大气中非水溶性的有机气溶胶组分包含细菌。

研究证据表明云水中存在碳循环,例如,从云水中分离出的细菌可以利用云水中常见的有机化合物(如醋酸酯、甲酸酯、L-乳酸盐、甲醛、甲醇)作为碳源[70]。细菌和这些代谢反应产物经常在云水中被发现,表明这些微生物积极转化云水中的有机物质。大气中有机物质的微生物降解不仅仅局限于云水,气溶胶中的细菌也可降解各种二羧酸,产生可以在大气中进一步转化的最终产物。空气微生物可作为水蒸汽转化为小冰晶的冰核,通过吸收额外的水蒸气进行生长,当它们从云中落下时,会清除超冷的水滴[14,19]。此外,一些细菌的细胞表面具有冰核蛋白(Ice Nucleation Proteins, INPs),可提高水蒸汽转化为冰的温度,达到-2 ℃,因此促成冰晶的形成[19,71]

根据已有研究,尚不确定海洋空气微生物的冰核活性,且不同海拔高度冰晶和卷积云形成的机理有待进一步的探索发现,需全面了解何种细胞特性和蛋白质可构成有效的CCN/IN。相较于先前预测,研究表明空气微生物对大气成核过程具有更重要的作用,该领域需要微生物学家、大气和海洋科学家之间紧密的合作交流,从而更准确地理解和模式模拟微生物气溶胶—云—降水—气候之间的相互作用。

7 影响海洋微生物气溶胶的因素

海洋气溶胶中细菌群落的组成受气象条件、颗粒物(Particulate Matter,PM)化学组分、环境条件及PBAP主要来源的综合影响[1,65]。环境温度对海洋微生物气溶胶具有重要影响,温度可直接影响细菌的新陈代谢和繁殖速率,且与许多影响大气中细菌浓度的重要气象和气候变量有关,比如边界层湍流、季节和每天的时间点。许多研究发现气溶胶中可培养的细菌浓度和总细菌的浓度与空气温度成正相关[29]。海冰密集度影响极地海域空气微生物的浓度和粒径分布[26],海冰通过影响微生物的海—气交换而影响北冰洋空气中真菌的浓度,此外,海冰包含大量微生物和营养盐,如活的和低活性的真菌、细菌。在浮冰区域,永久性的厚海冰阻止了微生物的海—气交换,然而,随着气温升高,海冰融化的进程加快,海冰中的微生物或营养物质被释放到大气中,从而增加了空气中微生物的浓度[25]

风速是影响海洋源微生物气溶胶的另一个重要因素。大风可导致更多的波浪和气泡破裂,海洋细菌伴随海盐一起被喷射到大气边界层中,因此强烈的冬季风可更有效地促使海洋细菌进入大气[55]。另一方面,大风也可导致海洋微生物气溶胶的浓度被更快地“稀释”。 区域差异与气溶胶的来源也是影响空气微生物群落结构和浓度变化的重要因素,Seifried等[1]在北海和波罗的海检测到蓝细菌呈明显依赖采样位置的分布模式,风向和气团后向轨迹较好地反映出气团来源(海洋、大陆)的影响。如果细菌和总气溶胶的来源一致,则细菌的浓度与总颗粒物(PM10)密切相关,这种相关性经常被观测到。沙尘携带的细菌可促进海洋环境中N2的固定,而不同来源的沙尘会对海水中细菌的生产和群落构成产生明显影响[23]。Gat等[22]的研究表明,不同的沙尘源明显影响空气细菌的群落结构组成,由于全球气候变化引起沙尘暴频次、来源和规模发生巨大变化,从而引起海洋微生物气溶胶群落组成和功能的变化。沙尘羽在传输途中会积聚不同来源的细菌类群,例如,传输经过海洋上空时会携带海洋源细菌,导致下风向大气细菌群落结构的组成发生巨大变化[18]

Gandolfi等[72]提出使用多元回归树(Multivariate Regression Trees, MRT)评估环境和气象条件对PM离子、元素和空气细菌群落结构的相对贡献。通常,海洋细菌气溶胶的平均浓度冬季最低、夏季最高,这种变化多大程度上是由海水表层生物活性驱动,还是受气象因素如温度、风速和降雨量的直接影响目前还不清楚[29,52]。许多站点的观测结果显示夏季空气细菌浓度更高,这可能是受温度的季节差异、源强度和大气对流的影响[52]。也有研究指出,波罗的海的一个沿海站点的细菌数量冬季最高是受冬季强海浪源的影响所致,在冬季检测到相比夏季较高的细菌CFU值[55]。 Xu等[56]利用冗余判别分析法(Redundant Discriminant Analysis, RDA)获得环境因素与微生物群落结构的相关性,PM2.5,PM10和温度与鞘氨醇单胞菌属(Sphingomonas)的相对丰度显著相关,这可能是因为这类细菌对高浓度大气颗粒物的相对耐受力较高且能够降解大气中的有机物。

目前,由于缺乏标准的采样和分析过程,很难解释微生物气溶胶研究结果的差异,例如,不同的分析方法(培养方法、变性梯度凝胶电泳和高通量测序),采样方法,气象条件(温度、UV辐射、风速和相对湿度),采样地点(地理位置和海拔高度),以及环境因素(电导率、PM2.5、PM10、SO2、O3、CO、NO2和pH)等都可能影响微生物气溶胶的丰度和群落结构组成[56]

8 研究展望

通过相关研究资料的汇总,对海洋环境微生物气溶胶的浓度、粒径分布和群落结构及气象、环境条件等影响因素进行了阐述与讨论,并回顾了微生物气溶胶的量化、检测和控制等方面的技术以及使用新一代高通量测序技术去描述和分析微生物的群落结构,为后续海洋微生物气溶胶的研究提供了最新的进展资料。研究表明,未来宏基因组学或多组学的联合应用将提高对大气中微生物活性、新陈代谢和功能的理解[5]。化学和生物数据(例如海洋空气中细菌的组成和PM化学组分之间的关系)在气溶胶研究中的结合可使我们对气溶胶生物地球化学循环具有更清晰、更深入的认识[57]

当前生物气溶胶的研究尚处于起步阶段,针对目前研究中的问题(比如,海洋空气是微生物极度稀释的环境,为了浓缩生物气溶胶含量,并增加发现稀有微生物的可能性,需要高容量的采样机制对其进行高效采集[73];因采集样品需进行二次处理(例如洗脱、DNA提取),操作方法不规范导致误差较大的问题;采集活性、可培养微生物及不同粒径范围的生物气溶胶颗粒物,由于高撞击压力、干燥和嵌入问题导致明显低估可培养微生物的负载量等), 需要确定标准的海洋空气微生物采集技术以及不断发展新技术以符合多学科交叉的研究需求。近年来,大流量过滤式采样器被用来短时间高效富集低浓度环境空气微生物。不同分子检测方法的联合使用、高通量测序、新仪器和技术的综合力量可以提高我们在复杂多变的自然环境下同时检测大气细菌、真菌和病毒的能力。这些方法将有助于我们对海洋微生物气溶胶的组成、丰度、功能和传输及其影响因素进行研究分析。

总而言之,海洋微生物气溶胶的观测数据还非常缺乏,其本身的特性、来源及对大气化学、区域气候和海洋生态系统的影响尚不清楚。建议未来从以下几个方面进行研究:①多开展海洋微生物气溶胶的航次观测,利用高通量测序、流式细胞仪计数及宏基因组学或多组学等先进有效的技术方法获取大量实测数据;②对海洋气溶胶中微生物与气溶胶的来源和化学组分之间的关系进行研究以获取微生物气溶胶的来源、传输、活性等信息;③研究海洋微生物气溶胶的粒径分布与群落结构的关系,了解其可能的气候效应与沉降后对海洋生态系统的影响;④特别关注海洋的开发利用和海洋的生态系统类型对观测空气微生物浓度的影响,作为发展大气模型中使用微生物气溶胶排放参数化的一个关键步骤;⑤理解云层和气溶胶中微生物的活性是理解它们在大气物理化学过程中可能存在作用的必要条件,这一知识对于深入理解海洋空气微生物的气候效应具有重大意义。

The authors have declared that no competing interests exist.


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[40] Bragg L, Stone G, Imelfort M, et al.

Fast, accurate error-correction of amplicon pyrosequences using Acacia

[J]. Nature Methods, 2012, 9(5): 425-426.

DOI      URL      [本文引用: 1]     

[41] Degnan P H, Ochman H.

Illumina-based analysis of microbial community diversity

[J]. The International Society for Microbial Ecology Journal, 2011, 6(1): 183-194.

DOI      URL      PMID      [本文引用: 1]      摘要

Microbes commonly exist in milieus of varying complexity and diversity. Although cultivation-based techniques have been unable to accurately capture the true diversity within microbial communities, these deficiencies have been overcome by applying molecular approaches that target the universally conserved 16S ribosomal RNA gene. The recent application of 454 pyrosequencing to simultaneously sequence thousands of 16S rDNA sequences (pyrotags) has revolutionized the characterization of complex microbial communities. To date, studies based on 454 pyrotags have dominated the field, but sequencing platforms that generate many more sequence reads at much lower costs have been developed. Here, we use the Illumina sequencing platform to design a strategy for 16S amplicon analysis (iTags), and assess its generality, practicality and potential complications. We fabricated and sequenced paired-end libraries of amplified hyper-variable 16S rDNA fragments from sets of samples that varied in their contents, ranging from a single bacterium to highly complex communities. We adopted an approach that allowed us to evaluate several potential sources of errors, including sequencing artifacts, amplification biases, non-corresponding paired-end reads and mistakes in taxonomic classification. By considering each source of error, we delineate ways to make biologically relevant and robust conclusions from the millions of sequencing reads that can be readily generated by this technology.
[42] Zhou H W, Li D F, Tam N F, et al.

BIPES, a cost-effective high-throughput method for assessing microbial diversity

[J]. The International Society for Microbial Ecology Journal, 2011, 5(4): 741-749.

DOI      URL      PMID      [本文引用: 1]      摘要

Abstract Pyrosequencing of 16S rRNA (16S) variable tags has become the most popular method for assessing microbial diversity, but the method remains costly for the evaluation of large numbers of environmental samples with high sequencing depths. We developed a barcoded Illumina paired-end (PE) sequencing (BIPES) method that sequences each 16S V6 tag from both ends on the Illumina HiSeq 2000, and the PE reads are then overlapped to obtain the V6 tag. The average accuracy of Illumina single-end (SE) reads was only 97.9%, which decreased from 芒聢录99.9% at the start of the read to less than 85% at the end of the read; nevertheless, overlapping of the PE reads significantly increased the sequencing accuracy to 99.65% by verifying the 3' end of each SE in which the sequencing quality was degraded. After the removal of tags with two or more mismatches within the medial 40-70 bases of the reads and of tags with any primer errors, the overall base sequencing accuracy of the BIPES reads was further increased to 99.93%. The BIPES reads reflected the amounts of the various tags in the initial template, but long tags and high GC tags were underestimated. The BIPES method yields 20-50 times more 16S V6 tags than does pyrosequencing in a single-flow cell run, and each of the BIPES reads costs less than 1/40 of a pyrosequencing read. As a laborsaving and cost-effective method, BIPES can be routinely used to analyze the microbial ecology of both environmental and human microbiomes.
[43] Griffin D W, Westphal D L, Gray M A.

Airborne microorganisms in the African desert dust corridor over the mid-Atlantic ridge, Ocean Drilling Program, Leg 209

[J]. Aerobiologia, 2006, 22(3): 211-226.

DOI      URL      [本文引用: 3]     

[44] Cho B C, Hwang C Y.

Prokaryotic abundance and 16S rRNA gene sequences detected in marine aerosols on the East Sea (Korea)

[J]. FEMS Microbiology Ecology, 2011, 76(2): 327-341.

DOI      URL      [本文引用: 3]     

[45] Kellogg C A, Griffin D W.

Aerobiology and the global transport of desert dust

[J]. Trends in Ecology and Evolution, 2006, 21(11): 638-644.

DOI      URL      [本文引用: 1]     

[46] Polymenakou P N, Mandalakis M, Stephanou E G, et al.

Particle size distribution of airborne microorganisms and pathogens during an intense African dust event in the Eastern Mediterranean

[J]. Environmental Health Perspectives, 2007, 116(3): 292-296.

DOI      URL      [本文引用: 2]     

[47] Stramski D, Boss E, Bogucki D,et al.

The role of seawater constituents in light backscattering in the ocean

[J]. Progress in Oceanography, 2004, 61(1): 27-56.

DOI      URL      [本文引用: 1]      摘要

The significance of light backscattering in the ocean is wide ranging, especially in optical remote sensing. However, the complexity of natural seawater as an optical medium often obscures the measured optical signals to the point that our present-day interpretation and detailed understanding of major sources of backscattering and its variability in the ocean are uncertain and controversial. Here we review the roles played by various seawater constituents in light backscattering and we address a question of issing backscattering. Historically, this question has resulted from a hypothesis that under non-bloom conditions in the open ocean, phytoplankton make a significantly smaller contribution to the particulate backscattering coefficient than to the particulate (total) scattering coefficient. By discussing the backscattering properties and potential contributions of the various water constituents (colloids, bacteria, phytoplankton, biogenic detritus, minerogenic particles, bubbles), we show that due to substantial variability in water composition, different types of constituents can explain the issing backscattering. Under typical non-bloom conditions in the open ocean, the small-sized non-living particles appear to be the most important because of their high abundance relative to other particle types. These particles are believed to be primarily of organic origin but an important role of minerogenic particles cannot be excluded. Still, in the very clear ocean water the backscattering by water molecules themselves can contribute as much as 80% to the total backscattering coefficient in the blue spectral region. The general scenario of the dominance of molecules and small-sized particles can, however, be readily perturbed due to changes in local conditions. For example, bubbles entrained by breaking waves can intermittently dominate the backscattering at shallow depths below the sea surface, the calcifying phytoplankton (coccolithophores) producing calcite scales of high refractive index can dominate if present in sufficient concentration, and other plankton species can dominate during blooms. The role of phytoplankton could be generally greater than commonly assumed given the fact that real cells backscatter more light than predicted from homogeneous sphere models. In addition, high refractive index mineral particles can dominate in many coastal areas, and perhaps also in some open ocean areas during events of atmospheric dust deposition. It is likely that the different scenarios are quite widespread and frequent. Further improvements in quantitative understanding of the variability in light backscattering and its sources require an increased effort in basic research to better characterize the optical properties of the various seawater constituents and the variability in the detailed composition of seawater. Seawater is a complex optical medium containing a great variety of particle types and soluble species that vary in concentration and composition with time and location in the ocean, so ocean optics science must progress beyond the traditional overly simplified description, which has been based only on a few constituent categories defined broadly as molecular water, suspended particles (phytoplankton and non-algal particles), and dissolved organic matter.
[48] Facchini M C, Rinaldi M, Decesari S, et al.

Primary submicron marine aerosol dominated by insoluble organic colloids and aggregates

[J]. Geophysical Research Letters, 2008, 35(17): L17814. DOI: 10.1029/2008GL034210.

URL      [本文引用: 1]      摘要

The chemical properties of sea-spray aerosol particles produced by artificially generated bubbles using oceanic waters were investigated during a phytoplankton bloom in the North Atlantic. Spray particles exhibited a progressive increase in the organic matter (OM) content from 3 +/- 0.4% up to 77 +/- 5% with decreasing particle diameter from 8 to 0.125 渭m. Submicron OM was almost entirely water insoluble (WIOM) and consisted of colloids and aggregates exuded by phytoplankton. Our observations indicate that size dependent transfer of sea water organic material to primary marine particles is mainly controlled by the solubility and surface tension properties of marine OM. The pattern of WIOM and sea-salt content in the different size intervals observed in bubble bursting experiments is similar to that measured in atmospheric marine aerosol samples collected during periods of high biological activity. The results point to a WIOM/sea-salt fingerprint associated with submicron primary marine aerosol production in biologically rich waters.
[49] O'Dowd C D, Langmann B, Varghese S, et al.

A combined organic-inorganic sea-spray source function

[J]. Geophysical Research Letters, 2008, 35(1): L01801. DOI: 10.1029/2007GL030331.

URL      [本文引用: 2]      摘要

This study presents a novel approach to determine sea-spray generation by a combined organic–inorganic submicron source function. It requires wind speed and surface ocean chlorophyll-a concentration as input parameters. The combined organic–inorganic source function is implemented in the REMOTE regional climate model and sea-spray fields are predicted with particular focus on the Northeast Atlantic. The model predictions, using the new source functions, compare well with observations of total sea-spray mass and organic carbon fraction in sea-spray aerosol. Keywords Marine aerosol, sea-spray source function, organic aerosol
[50] Ceburnis D, O'Dowd C D, Jennings G S, et al.

Marine aerosol chemistry gradients: Elucidating primary and secondary processes and fluxes

[J]. Geophysical Research Letters, 2008, 35(7): L07804. DOI: 10.1029 /2008GL033462.

URL      [本文引用: 1]      摘要

Production mechanisms of aerosol chemical species, in terms of primary and secondary processes, were studied using vertical concentration gradient measurements at the coastal research station in Mace Head, Ireland. Total gravimetric PM1.0 mass, sea salt and water insoluble organic carbon (WIOC) concentration profiles showed a net production at the surface (i.e. primary production), while nssSOand water soluble organic carbon (WSOC) concentration profiles showed a net removal at the surface. These observations indicate that WSOC was predominantly of secondary origin and that WIOC was predominantly of primary origin. Derived PM1 mass fluxes compared reasonably well with those previously obtained from an eddy covariance (EC) technique following a power law relationship with the wind speed (F = 0.000096*U ). For cases with clear primary organic mass fluxes in the flux footprint WIOM mass fluxes ranged between 0.16 and 1.02 ng msand WIOM/sea salt mass ratio was 0.34-3.6, in good agreement with previous measurements at Mace Head.
[51] O'Dowd C D, de Leeuw G.

Marine aerosol production: A review of the current knowledge

[J]. Philosophical Transactions of the Royal Society AMathematical Physical and Engineering Sciences, 2007, 365(1 856): 1 753-1774.

DOI      URL      PMID      [本文引用: 1]      摘要

The current knowledge in primary and secondary marine aerosol formation is reviewed. For primary marine aerosol source functions, recent source functions have demonstrated a significant flux of submicrometre particles down to radii of 20 nm. Moreover, the source functions derived from different techniques up to 10 渭m have come within a factor of two of each other. For secondary marine aerosol formation, recent advances have identified iodine oxides and isoprene oxidation products, in addition to sulphuric acid, as contributing to formation and growth, although the exact roles remains to be determined. While a multistep process seems to be required, isoprene oxidation products are more likely to participate in growth and sulphuric acid is more likely to participate in nucleation. Iodine oxides are likely to participate in both nucleation and growth.
[52] Tong Y, Lighthart B.

The annual bacterial particle concentration and size distribution in the ambient atmosphere in a rural area of the Willamette Valley, Oregon

[J]. Aerosol Science and Technology, 2000, 32(5): 393-403.

DOI      URL      [本文引用: 5]     

[53] Wang C C, Fang G C, Lee L Y.

The study of ambient air bioaerosols during summer daytime and nighttime periods in Taichung, Central Taiwan

[J].Environmental Forensics, 2008, 9(1): 6-14.

DOI      URL      [本文引用: 1]     

[54] Lu Longfei, Zhang Rui, Xu Jie, et al.

Influence of virus upon the marine bacterial metabolism and its biogeochemical effects

[J]. Advances in Earth Science, 2018, 33(3): 225-235.

[本文引用: 1]     

[卢龙飞, 张锐, 徐杰, .

病毒对海洋细菌代谢的影响及其生物地球化学效应

[J]. 地球科学进展,2018,33(3): 225-235.]

[本文引用: 1]     

[55] Fahlgren C, Hagstrom A, Nilsson D,et al.

Annual variations in the diversity, viability, and origin of airborne bacteria

[J]. Applied and Environmental Microbiology, 2010, 76(9): 3 015-3 025.

DOI      URL      PMID      [本文引用: 3]      摘要

The presence of bacteria in aerosols has been known for centuries, but information on their identity and role in dispersing microbial traits is still limited. This study monitored the airborne bacterial community during an annual survey using samples collected from a 25-m tower near the Baltic Sea coast. The number of CFU was estimated using agar plates while the most probable number (MPN) of viable bacteria was estimated using dilution-to-extinction culturing assays (DCAs). The MPN and CFU values produced quantitatively similar results, displaying a pronounced seasonal pattern, with the highest numbers in winter. The most dominant bacteria growing in the DCAs all formed colonies on agar plates, were mostly pigmented (80%), and closely resembled (>97%) previously cultured bacteria based on their 16S rRNA gene sequences. 16S rRNA gene clone libraries were constructed on eight occasions during the survey; these revealed a highly diverse community with a few abundant operational taxonomic units (OTUs) and a long tail of rare OTUs. A majority of the cloned sequences (60%) were also most closely related to previously "cultured" bacteria. Thus, both culture-dependent and culture-independent techniques indicated that bacteria able to form colonies on agar plates predominate in the atmosphere. Both the DCAs and clone libraries indicated the dominance of bacteria belonging to the genera Sphingomonas sp. and Pseudomonas sp. on several sampling occasions. Potentially pathogenic strains as well as sequences closely resembling bacteria known to act as ice nuclei were found using both approaches. The origin of the sampled air mass was estimated using backward trajectories, indicating a predominant marine source.
[56] Xu C, Wei M, Chen J,et al.

Investigation of diverse bacteria in cloud water at Mt. Tai, China

[J]. Science of the Total Environment, 2017, 580: 258-265. DOI: 10.1016/j.scitotenv.2016.12.081.

URL      PMID      [本文引用: 3]      摘要

61Bacterial community in cloud water of Asian area was studied for the first time.61High throughput sequencing revealed diverse gram-negative bacteria mainly inhabiting in leaf-surface and cold environments.61Bacteria involved in the cloud condensation nuclei and ice nucleation process were observed.61SO2and O3distinctly contributed to the variations of species-environment relationship in different samples.
[57] Innocente E, Squizzato S, Visin F, et al.

Influence of seasonality. Influence of seasonality, air mass origin and particulate matter chemical composition on airborne bacterial community structure in the Po Valley, Italy

[J]. Science of the Total Environment, 2017, 593/594: 677-687. DOI: 10.1016/j.scitotenv.2017.03.199.

[本文引用: 2]     

[58] Kwak M J, Song J Y, Kim B K, et al.

Genome sequence of the agar-degrading marine bacterium Alteromonadaceae sp. strain G7

[J]. Journal of Bacteriology, 2012, 194(24): 6 961-6 962.

DOI      URL      PMID      [本文引用: 1]      摘要

Here, we present the high-quality draft genome sequence of the agar-degrading marine gammaproteobacterium Alteromonadaceae sp. strain G7, which was isolated from coastal seawater to be utilized as a bioresource for production of agar-derived biofuels. The 3.91-Mb genome contains a number of genes encoding algal polysaccharide-degrading enzymes such as agarases and sulfatases.
[59] Kourtev P S, Hill K A, Shepson P B, et al.

Atmospheric cloud water contains a diverse bacterial community

[J]. Atmospheric Environment, 2011, 45(30): 5 399-5 405.

DOI      URL      [本文引用: 1]      摘要

Atmospheric cloud water contains an active microbial community which can impact climate, human health and ecosystem processes in terrestrial and aquatic systems. Most studies on the composition of microbial communities in clouds have been performed with orographic clouds that are typically in direct contact with the ground. We collected water samples from cumulus clouds above the upper U.S. Midwest. The cloud water was analyzed for the diversity of bacterial phylotypes by denaturing gradient gel electrophoresis (DGGE) and sequencing of 16S rRNA gene amplicons. DGGE analyses of bacterial communities detected 17 21 bands per sample. Sequencing confirmed the presence of a diverse bacterial community; sequences from seven bacterial phyla were retrieved. Cloud water bacterial communities appeared to be dominated by members of the cyanobacteria, proteobacteria, actinobacteria and firmicutes.Highlights? We collected samples from warm, cumulus clouds over forested areas in Michigan. ? We determined bacterial diversity in cloud water using DGGE and DNA Sequencing. ? Cloud water contains a diverse bacterial community. ? We identified bacteria that can potentially act as condensation and ice nuclei.
[60] Latifi A, Ruiz M, Zhang C C.

Oxidative stress in cyanobacteria

[J]. FEMS Microbiology Reviews, 2009, 33(2): 258-278.

DOI      URL      [本文引用: 1]     

[61] Gao Huiwang, Yao Xiaohong, Guo Zhigang, et al.

Atmospheric deposition connected with marine primary production and nitrogen cycle: A review

[J]. Advances in Earth Science, 2014, 29(12): 1 325-1 332.

[本文引用: 1]     

[高会旺, 姚小红, 郭志刚,.

大气沉降对海洋初级生产过程与氮循环的影响研究进展

[J]. 地球科学进展, 2014, 29(12): 1 325-1 332.]

DOI      URL      [本文引用: 1]      摘要

大气沉降通过为海洋提供外源性氮、磷和铁等微量元素,可显著影响海洋氮、碳循环过程,并产生气候效应。一方面促进海洋初级生产和生物固氮,增强海洋吸收二氧化碳的能力;另一方面影响海洋氮、碳循环路径,增加海洋生物源气溶胶排放量,间接影响气候变化。由于大气沉降对海洋生态系统及气候变化的重要影响,相关科学问题已成为海洋科学与大气科学交叉研究的热点,被多个国际研究计划列为核心研究内容。在大气污染物排放持续增加与沙尘事件频发的背景下,大气沉降对我国东部陆架海(黄海、东海)及其邻近西北太平洋碳、氮循环过程的影响日趋增强,因此该海区已成为大气沉降及其气候影响研究的代表性海域。结合分子生物学和实验生态学手段理解大气沉降影响下的海洋初级生产过程,利用同位素示踪技术研究大气沉降对海洋氮循环的影响,以及获得大气沉降影响下海洋生物源气溶胶排放的观测证据将是未来研究的重点方向。
[62] Chen Ying, Zhuang Guoshun, Guo Zhigang.

Atmospheric desposition of nutrients and trace elements to the coastal oceans: A review

[J]. Advances in Earth Science, 2010, 25(7): 682-690.

Magsci      [本文引用: 1]     

[陈莹, 庄国顺, 郭志刚.

近海营养盐和微量元素的大气沉降

[J]. 地球科学进展, 2010,25(7): 682-690.]

DOI      URL      Magsci      [本文引用: 1]      摘要

<p>受气候变化和人类活动的影响,传输和沉降到全球近海的大气污染物急剧增加。1997年后对近海营养盐和微量元素大气沉降的众多研究表明,通过大气沉降至近海的氮和磷分别为13~73 mmol N /(m<sup>2</sup>&middot;a)和0.11~1.6 mmol P /(m<sup>2</sup>&middot;a),微量元素的沉降通量具有显著的时空变化特征,在不同海区最高可相差3个数量级。对于很多近海包括东海(East China Sea)和黄海(Yellow Sea),大气沉降的营养盐和部分微量元素可能超出了其河流输入量。大气沉降除了对近海富营养化有重要贡献之外,其事件性特征可使初级生产力在短期内大幅度增加,从而影响赤潮发生。微量元素沉降还可能抑制某些藻类生长,对初级生产力和生态系统结构产生更为复杂的影响。未来研究重点是准确估算近海各物质的大气沉降通量,了解其对浮游植物生长的影响机制。</p>
[63] Liu Qingchun, Qian Huaisui.

International geosphere biosphere program: Progress and prospect

[J]. Meteorological Technology and Science, 2005, 33(1):91-95.

[本文引用: 1]     

[刘清春, 千怀遂.

国际地圈—生物圈计划研究进展和展望

[J]. 气象科技, 2005, 33(1): 91-95.]

[本文引用: 1]     

[64] Sorooshian A, MacDonald A B, Dadashazar H, et al.

A multi-year data set on aerosol-cloud-precipitation-meteorology interactions for marine stratocumulus clouds

[J]. Scientific Data, 2018, 5: 180026. DOI: 10.1038/sdata.2018.26.

URL      [本文引用: 1]     

[65] Brodie E L, DeSantis T Z, Parker J P, et al.

Urban aerosols harbor diverse and dynamic bacterial populations

[J]. Proceedings of the National Academy of Sciences of the United States of America, 2007, 104(1): 299-304.

DOI      URL      PMID      [本文引用: 2]      摘要

Considering the importance of its potential implications for human health, agricultural productivity, and ecosystem stability, surprisingly little is known regarding the composition or dynamics of the atmosphere's microbial inhabitants. Using a custom high-density DNA microarray, we detected and monitored bacterial populations in two U.S. cities over 17 weeks. These urban aerosols contained at least 1,800 diverse bacterial types, a richness approaching that of some soil bacterial communities. We also reveal the consistent presence of bacterial families with pathogenic members including environmental relatives of select agents of bioterrorism significance. Finally, using multivariate regression techniques, we demonstrate that temporal and meteorological influences can be stronger factors than location in shaping the biological composition of the air we breathe.
[66] Amato P, Parazols M, Sancelme M, et al.

An important oceanic source of micro-organisms for cloud water at the Puy de Dôme (France)

[J]. Atmospheric Environment, 2007, 41(37): 8 253-8 263.

DOI      URL      [本文引用: 1]      摘要

A description of the microbial content of cloud water based on samples collected along an almost 2-year-period is presented. Cloud water from 14 events was sampled at the Puy de D00me summit (1465 m a.s.l.). Total bacterial and fungal cells were about, respectively, 8.1×10 4 and 5.9×10 3 mL 611, with more than 10% of the fungi but <1% of bacteria recovered by cultivation at 15 or 27 °C. However, ATP concentration of about 0.40 pmol mL 611 shows that a large majority of these cells are likely viable but not cultivable and remain alive in clouds. A high variability is noticed in the microbial content, and local meteorological variations are not involved. A seasonal effect is shown, with a general increase in the concentrations of cultivable micro-organism and of total fungal cells during summer and autumn. Moreover, psychrotolerant micro-organisms, with respect to those growing only at 27 °C, are more numerous during winter. The concentrations of micro-organisms (total and cultivable) were clearly linked to the chemical composition of cloud water: an increase with increasing oceanic contribution is pointed, and bacteria concentration decreases with increasing anthropic influence. A preferential integration of micro-organisms emitted by the ocean into cloud droplets, compared to micro-organisms from other sources, is likely to occur, making the ocean a major source of micro-organisms for cloud water. It also suggests that the toxicity of polluted cloud water could disturb an eventual multiplication of cells in atmospheric droplets.
[67] Spracklen D V, Arnold S R, Sciare J, et al.

Globally significant oceanic source of organic carbon aerosol

[J]. Geophysical Research Letters, 2008, 35(12): L12811. DOI: 10.1029/2008GL033359.

URL      [本文引用: 1]      摘要

Significant concentrations of organic carbon (OC) aerosol are observed at three oceanic surface sites (Amsterdam Island, Azores and Mace Head). Two global chemical transport models (CTMs) underpredict OC concentrations at these sites (normalised mean bias of -67% and -58%). During periods of high biological activity monthly mean concentrations are underpredicted by a factor of 5-20. At Amsterdam Island and Mace Head, observed OC correlates well (R= 0.61-0.77) with back-trajectory weighted chlorophyll-a, suggesting an oceanic OC source driven by biological activity. We use a combination of remote sensed chlorophyll-a, back trajectories and observed OC to derive an empirical relation between chlorophyll-a and the total oceanic OC emission flux. Using the GEOS-chem CTM we show a global oceanic OC emission, from primary and secondary sources, of ~8 Tg/year matches observations. This emission is comparable in magnitude to the fossil fuel OC source and increases the simulated global OC burden by 20%.
[68] O'dowd C D, Facchini M C, Cavalli F, et al.

Biogenically driven organic contribution to marine aerosol

[J]. Nature, 2004, 431(7 009): 676.

DOI      URL      [本文引用: 1]     

[69] Meskhidze N, Nenes A.

Phytoplankton and cloudiness in the Southern Ocean

[J]. Science, 2006, 314(5 804): 1 419-1 423.

DOI      URL      PMID      [本文引用: 1]      摘要

The effect of ocean biological productivity on marine clouds is explored over a large phytoplankton bloom in the Southern Ocean with the use of remotely sensed data. Cloud droplet number concentration over the bloom was twice what it was away from the bloom, and cloud effective radius was reduced by 30%. The resulting change in the short-wave radiative flux at the top of the atmosphere was -15 watts per square meter, comparable to the aerosol indirect effect over highly polluted regions. This observed impact of phytoplankton on clouds is attributed to changes in the size distribution and chemical composition of cloud condensation nuclei. We propose that secondary organic aerosol, formed from the oxidation of phytoplankton-produced isoprene, can affect chemical composition of marine cloud condensation nuclei and influence cloud droplet number. Model simulations support this hypothesis, indicating that 100% of the observed changes in cloud properties can be attributed to the isoprene secondary organic aerosol.
[70] Vaitilingom M, Amato P, Sancelme M, et al.

Contribution of microbial activity to carbon chemistry in clouds

[J]. Applied and Environmental Microbiology, 2010, 76(1): 23-29.

DOI      URL      PMID      [本文引用: 1]      摘要

The biodegradation of the most abundant atmospheric organic C1 to C4 compounds (formate, acetate, lactate, succinate) by five selected representative microbial strains (three Pseudomonas strains, one Sphingomonas strain, and one yeast strain) isolated from cloud water at the puy de D么me has been studied. Experiments were first conducted under model conditions and consisted of a pure strain incubated in the presence of a single organic compound. Kinetics showed the ability of the isolates to degrade atmospheric compounds at temperatures representative of low-altitude clouds (5 degrees C and 17 degrees C). Then, to provide data that can be extrapolated to real situations, microcosm experiments were developed. A solution that chemically mimicked the composition of cloud water was used as an incubation medium for microbial strains. Under these conditions, we determined that microbial activity would significantly contribute to the degradation of formate, acetate, and succinate in cloud water at 5 degrees C and 17 degrees C, with lifetimes of 0.4 to 69.1 days. Compared with the reactivity involving free radicals, our results suggest that biological activity drives the oxidation of carbonaceous compounds during the night (90 to 99%), while its contribution accounts for 2 to 37% of the reactivity during the day, competing with photochemistry.
[71] Kawahara H.

The structures and functions of ice crystal-controlling proteins from bacteria

[J]. Journal of Bioscience and Bioengineering, 2002, 94(6): 492-496.

DOI      URL      PMID      [本文引用: 1]      摘要

Many organisms have evolved into unique mechanisms which minimize freezing injury due to extracellular ice formation. Specifically, certain bacteria have produced a few proteins each with different functions. For example, the ice nucleation protein acts as a template for ice formation, which is responsible for imparting ice nucleating activity. The anti-nucleating protein inhibits the fluctuation of ice nucleus formation by a foreign particle in the water drop. Also, the antifreeze proteins depress the freezing temperature, modify or suppress ice crystal growth, inhibit ice recystallization, and protect the cell membrane from cold-induced damage. In this article, a review on the current knowledge of the structure and the function of these three types of proteins, which are capable of interacting with ice itself or its nuclei from bacteria.
[72] Gandolfi I, Bertolini V, Bestetti G,et al.

Spatio-temporal variability of airborne bacterial communities and their correlation with particulate matter chemical composition across two urban areas

[J]. Applied Microbiology and Biotechnology, 2015, 99(11): 4 867-4 877.

DOI      URL      [本文引用: 1]     

[73] Mbareche H, Brisebois E, Veillette M,et al.

Bioaerosol sampling and detection methods based on molecular approaches: No pain no gain

[J]. Science of the Total Environment, 2017, (599/600): 2 095-2 104. DOI: 10.1016/j.scitotenv.2017.05.076.

URL      PMID      [本文引用: 1]      摘要

Bioaerosols are among the less studied particles in the environment. The lack of standardization in sampling procedures, difficulties related to the effect of sampling processes on the integrity of microorganisms, and challenges associated with the application of environmental microbiology analyses and molecular and culture methods frighten many young scientists. Every microorganism has its own particularities and acts differently when aerosolized in various conditions. Because the air is an extremely biologically diluted environment, it is necessary to concentrate its content before any analysis is performed. Challenges faced when applying molecular methods to air samples reveal the need for a better standardization of approaches for cell and nucleic acid recovery, the choice of genetic markers, and interpretation of data. This paper presents a few of the limits and difficulties tackled when molecular methods are applied to bioaerosols, suggests some improvements by specifying the critical stages that should be considered when studying the microbial ecology of bioaerosols, and provides thoughtful insights on how to overcome the challenges encountered.

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