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
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.
WangFanghui, ChenYing, WangBo, LiHaowen, ZhouShengqian. 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
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。
Abstract The spatial distribution of bacterial populations in marine bioaerosol samples was investigated during a cruise from the North Sea to the Baltic Sea via Skagerrak and Kattegat. The analysis of the sampled bacterial communities with a pyrosequencing approach revealed that the most abundant phyla were represented by the Proteobacteria (49.3%), Bacteroidetes (22.9%), Actinobacteria (16.3%), and Firmicutes (8.3%). Cyanobacteria were assigned to 1.5% of all bacterial reads. A core of 37 bacterial OTUs made up more than 75% of all bacterial sequences. The most abundant OTU was Sphingomonas sp. which comprised 17% of all bacterial sequences. The most abundant bacterial genera were attributed to distinctly different areas of origin, suggesting highly heterogeneous sources for bioaerosols of marine and coastal environments. Furthermore, the bacterial community was clearly affected by two environmental parameters temperature as a function of wind direction and the sampling location itself. However, a comparison of the wind directions during the sampling and calculated backward trajectories underlined the need for more detailed information on environmental parameters for bioaerosol investigations. The current findings support the assumption of a bacterial core community in the atmosphere. They may be emitted from strong aerosolizing sources, probably being mixed and dispersed over long distances.
[2]
Prospero JM, BladesE, MathisonG, et al.
Interhemispheric transport of viable fungi and bacteria from Africa to the Caribbean with soil dust
Poor air hygiene as a result of bioaerosol contamination has caused diverse forms of adverse health effects and diseases. In addition, global biosecurity is threatened by purposeful use of biowarfare agents and the vulnerability of people to the infectious agents. Accordingly, developments in high-volume biosampling, including aerosol-to-hydrosol techniques with low cut-off size, real-time bioaerosol detection, adequate biological quantification, and exposure control, as well as the investigation of the link between disease outcome and bioaerosol exposure, are current areas of bioaerosol research. Although milestone progress has been achieved both in bioaerosol sampling and analysis techniques since late 1800s, compared to atmospheric chemistry the bioaerosol field is still understudied. This is partially because of the lack of both bioaerosol scientists and multidisciplinary collaboration. It is becoming necessary to develop a pool of scientists with different expertise, e.g., bioaerosol scientists, environmental engineers, biomedical engineers, epidemiologists, microbiologists, chemists, physicists, as well as researchers in other engineering fields, in mitigating bioaerosol-related adverse health effects, eliminating diseases, and preventing and controlling epidemic outbreaks. This work is conducted to broadly review current state-of-the-art sciences and technologies in the bioaerosol field. In tackling the challenges ahead, the review also provides perspectives for bioaerosol research needs, and further reminds bioaerosol scientists of those existing technologies in other fields that can be leveraged. In view of the past, forward-looking hypotheses and revolutional perspectives are needed to be formed in order to allow the bioaerosol research have major impacts in the academic community in this new millennium.
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61Understanding the presence of airborne bacteria in the atmosphere.61Unravelling the roles airborne bacteria have on atmospheric process and health.61Exploring the underlying potential of airborne bacteria for various applications.
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Characterization of airborne ice-nucleation-active bacteria and bacterial fragments
61Wet deposition of ice nucleation active (INA)Pseudomonasstrains was observed.61Precipitation contained high density (199–48202L611) of submicron INA cell fragments.61INA cells either had a long-distance continental or a local origin.6112% of all cultivable bacteria carriedinagenes and were INA at ≤61702°C.61Isolated INA strains excreted INA outer membrane vesicles at low concentrations.
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Primary biological aerosol particles in the atmosphere: A review
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 (1465m 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 3.3×103 to 2.5×105 total bacteria mL611, but up to 41% of the 8.9×102 to 3.2×104 fungal cells mL611. 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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Abstract The amount of ice present in clouds can affect cloud lifetime, precipitation and radiative properties. The formation of ice in clouds is facilitated by the presence of airborne ice-nucleating particles. Sea spray is one of the major global sources of atmospheric particles, but it is unclear to what extent these particles are capable of nucleating ice. Sea-spray aerosol contains large amounts of organic material that is ejected into the atmosphere during bubble bursting at the organically enriched sea-air interface or sea surface microlayer. Here we show that organic material in the sea surface microlayer nucleates ice under conditions relevant for mixed-phase cloud and high-altitude ice cloud formation. The ice-nucleating material is probably biogenic and less than approximately 0.2 micrometres in size. We find that exudates separated from cells of the marine diatom Thalassiosira pseudonana nucleate ice, and propose that organic material associated with phytoplankton cell exudates is a likely candidate for the observed ice-nucleating ability of the microlayer samples. Global model simulations of marine organic aerosol, in combination with our measurements, suggest that marine organic material may be an important source of ice-nucleating particles in remote marine environments such as the Southern Ocean, North Pacific Ocean and North Atlantic Ocean.
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MöhlerO, DeMottP, ValiG, et al.
Microbiology and atmospheric processes: The role of biological particles in cloud physics
As part of a series of papers on the sources, distribution and potential impact of biological particles in the atmosphere, this paper introduces and summarizes the potential role of biological particles in atmospheric clouds. Biological particles like bacteria or pollen may be active as both cloud condensation nuclei (CCN) and heterogeneous ice nuclei (IN) and thereby can contribute to the initial cloud formation stages and the development of precipitation through giant CCN and IN processes. The paper gives an introduction to aerosol-cloud processes involving CCN and IN in general and provides a short summary of previous laboratory, field and modelling work which investigated the CCN and IN activity of bacterial cells and pollen. Recent measurements of atmospheric ice nuclei with a continuous flow diffusion chamber (CFDC) and of the heterogeneous ice nucleation efficiency of bacterial cells are also briefly discussed. As a main result of this overview paper we conclude that a proper assessment of the impact of biological particles on tropospheric clouds needs new laboratory, field and modelling work on the abundance of biological particles in the atmosphere and their CCN and heterogeneous IN properties.
[15]
MayolE, Arrieta JM, Jiménez MA, et al.
Long-range transport of airborne microbes over the global tropical and subtropical ocean
The atmosphere plays a fundamental role in the transport of microbes across the planet but it is often neglected as a microbial habitat. Although the ocean represents two thirds of the Earth’s surface, there is little information on the atmospheric microbial load over the open ocean. Here we provide a global estimate of microbial loads and air-sea exchanges over the tropical and subtropical oceans based on the data collected along the Malaspina 2010 Circumnavigation Expedition. Total loads of airborne prokaryotes and eukaryotes were estimated at 2.265×651021and 2.165×651021cells, respectively. Overall 33–68% of these microorganisms could be traced to a marine origin, being transported thousands of kilometres before re-entering the ocean. Moreover, our results show a substantial load of terrestrial microbes transported over the oceans, with abundances declining exponentially with distance from land and indicate that islands may act as stepping stones facilitating the transoceanic transport of terrestrial microbes. The extent to which the ocean acts as a sink and source of airborne particles to the atmosphere is unresolved. Here, the authors report high microbial loads over the tropical Atlantic, Pacific and Indian oceans and propose islands as stepping stones for the transoceanic transport of terrestrial microbes..
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Aller JY, Kuznetsova MR, Jahns CJ, et al.
The sea surface microlayer as a source of viral and bacterial enrichment in marine aerosols
Marine aerosols are formed primarily by the eruption of rising bubbles through the sea-surface microlayer (SML), and aerosol formation is the main vector for transport of bacteria and viruses across the air–sea interface. The processes by which materials are transported to and through the SML to the atmosphere results in an enrichment in the SML of microbial and other organisms. We evaluated concentrations of marine bacteria and viruses in natural aerosols and in those simulated by bubbling sea sprays and compared them to the concentrations in SML (200– 400 μ m thick) and in subsurface water. Association of microorganisms with transparent gel-like organic particles and physiological status of bacteria were also assessed. We found a 15–25-fold enrichment in bacteria and viruses during transport from subsurface waters to the SML, and then into the atmosphere. The majority of microorganisms in aerosols were found embedded in the organic particles. Large portions of microorganisms in the SML were also associated with the particles, while in subsurface waters most of them were free-living. A larger percentage of damaged and less active bacterial cells occur in the microlayer than in subsurface waters, and preliminary data suggest that an even greater percentage occurs in aerosols. Our data support the idea that the SML in a major source of microorganisms entering the atmosphere from water bodies. Aerosolization is potentially an important long-distance dispersal mechanism and may account for observed cosmopolitan distributions of some bacteria.
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Biogeography in the air: Fungal diversity over land and oceans
Biogenic aerosols are relevant for the Earth system, climate, and public health on local, regional, and global scales. Up to now, however, little is known about the diversity and biogeography of airborne microorganisms. We present the first DNA-based analysis of airborne fungi on global scales, showing pronounced geographic patterns and boundaries. In particular we find that the ratio of species richness between Basidiomycota and Ascomycota is much higher in continental air than in marine air. This may be an important difference between the "blue ocean" and "green ocean" regimes in the formation of clouds and precipitation, for which fungal spores can act as nuclei. Our findings also suggest that air flow patterns and the global atmospheric circulation are important for the understanding of global changes in biodiversity.
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Assessment of composition and origin of airborne bacteria in the free troposphere over Japan
61Aerosol samples were collected at high altitudes using an aircraft and a balloon.61During four sampling periods, the air masses came from the Gobi Desert and North Asia.61Airborne bacterial species were investigated using a 16S rDNA clone library technique.61Bacterial species at high altitudes varied by the direction of free tropospheric winds.
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High bacterial 16S rRNA gene diversity above the atmospheric boundary layer
Abstract to 1.802×021002m air and colony-forming units of 0–602bacteria m air. 16S rRNA gene libraries constructed from samples collected above the Baltic Sea coast revealed a highly diverse bacterial community dominated by species belonging to the genera Sphingomonas and Pseudomonas. Bacterial species known to carry ice-nucleating proteins were found in several samples. Modeled back trajectories suggested the potential sources of the sampled bacteria to be diverse geographic regions, including both marine and terrestrial environments in the northern hemisphere. Several samples contained 16S rRNA genes from plant chloroplasts, confirming a terrestrial contribution to these samples. Interestingly, the airborne bacterial community displayed an apparent seasonal succession that we tentatively ascribe to in situ succession in the atmosphere.
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Vertical distribution of airborne bacterial communities in an Asian-dust downwind area, Noto Peninsula
Dust storms include particulate matter that is transported over land and sea with biota that could impact downwind ecosystems. In addition to the physico-chemical compositions, organismal diversities of dust from two storm events in southern Israel, December 2012 (Ev12) and January 2013 (Ev13), were determined by pyro-sequencing using primers universal to 16S and 18S rRNA genes and compared. The bio-assemblages in the collected dust samples were affiliated with scores of different taxa. Distinct patterns of richness and diversity of the two events were influenced by the origins of the air masses: Ev13 was rich with reads affiliated to Betaproteobacteria and Embryophyta, consistent with a European origin. Ev12, originated in north-Africa, contained significantly more of the Actinobacteria and fungi, without conifers. The abundance of bacterial and eukaryotic reads demonstrates dissemination of biological material in dust that may impose health hazards of pathogens and allergens, and influence vegetation migration throughout the world.
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Origin-dependent variations in the atmospheric microbiome community in eastern Mediterranean dust storms
The study of airborne biological particles ('bioaerosols') has gained interest in recent years, due to an increasing amount of evidence suggesting that this fraction of airborne particulate matter may play a critical role in the negative effects of aerosols on biological systems. Pioneer investigations demonstrated that bacteria do exist in the atmosphere and can be metabolically active, although studies have not proved whether they actually form ecological communities or are merely assemblages of organisms passively transported from different sources. For a long time, cultivation-based methods have been the gold standard to describe and quantify airborne microorganisms. However, the use of culture-independent techniques and, more recently, of the next-generation sequencing-based methods, has improved the ability of the scientific community to investigate bioaerosols in detail and to address further research questions, such as the temporal and spatial variability of airborne bacterial assemblages, the environmental factors affecting this variability and the potential sources of atmospheric bacteria. This paper provides a systematic review of the state-of-the-art methodologies used in the study of airborne bacteria to achieve each of the aforementioned research objectives, as well as the main results obtained so far. Critical evaluations of the current state of the knowledge and suggestions for further researches are provided.
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Concentration and size distribution of fungi aerosol over oceans along a cruise path during the fourth chinese arctic research expedition
Total (as opposed to culturable) bacterial number counts are reported for four sites in the United Kingdom measured during campaigns over four separate seasons. These are interpreted in relation to simple climatic factors, i.e. temperature, wind speed and wind direction. Temperature has a marked effect at all four sites with data for a rural coastal site conforming best to a simple exponential model. Data for the other rural and urban locations show a baseline similar to that determined at the coastal rural location, but with some very significant positive excursions. The temperature dependence of bacterial number is found to conform to that typical of bacterial growth rates. At the coastal rural location, bacterial numbers normalised for temperature show no dependence on wind speed whilst at the inland sites there is a decrease with increasing wind speed of the form expected for a large area source. Only one site appeared to show a systematic relationship of bacterial concentrations to wind direction that being a site in the suburbs of Birmingham with highest number concentrations observed on a wind sector approaching from the city centre. PCR techniques have been used to identify predominant types of bacteria and results are presented which show that Bacillus was the dominant genus observed at the three inland sites during the winter and summer seasons. Pseudomonas appeared with comparable frequency at certain sites and seasons. There was in general a greater diversity of bacteria at the coastal site than at the inland sites.
[30]
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Variations in the structure of airborne bacterial communities in a downwind area during an Asian dust (Kosa) event
61Flow cytometry (FCM) combined with Calcofluor White stain is a rapid and sensitive method for detecting and quantifying fungal spores in the atmosphere.61The FCM results had significant positive correlation with the concentrations of the fungal tracers.61This study revealed a high abundance of fungal spores in the urban area of Beijing, China.61Meteorological conditions were shown to have complex effects on the ambient concentrations of fungal spores.
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OuF, McGoverinC, SwiftS,et al.
Absolute bacterial cell enumeration using flow cytometry
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 HW, Li DF, Tam NF, et al.
BIPES, a cost-effective high-throughput method for assessing microbial diversity
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 DW, Westphal DL, Gray MA.
Airborne microorganisms in the African desert dust corridor over the mid-Atlantic ridge, Ocean Drilling Program, Leg 209
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 MC, RinaldiM, DecesariS, et al.
Primary submicron marine aerosol dominated by insoluble organic colloids and aggregates
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 CD, LangmannB, VargheseS, et al.
A combined organic-inorganic sea-spray source function
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
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CeburnisD, O'DowdC D, JenningsG S, et al.
Marine aerosol chemistry gradients: Elucidating primary and secondary processes and fluxes
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 CD, de LeeuwG.
Marine aerosol production: A review of the current knowledge
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]
TongY, LighthartB.
The annual bacterial particle concentration and size distribution in the ambient atmosphere in a rural area of the Willamette Valley, Oregon
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]
XuC, WeiM, ChenJ,et al.
Investigation of diverse bacteria in cloud water at Mt. Tai, China
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]
InnocenteE, SquizzatoS, VisinF, 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
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 PS, Hill KA, Shepson PB, et al.
Atmospheric cloud water contains a diverse bacterial community
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.
<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>·a)和0.11~1.6 mmol P /(m<sup>2</sup>·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]
LiuQingchun, QianHuaisui.
International geosphere biosphere program: Progress and prospect
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]
AmatoP, ParazolsM, SancelmeM, et al.
An important oceanic source of micro-organisms for cloud water at the Puy de Dôme (France)
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 DV, Arnold SR, SciareJ, et al.
Globally significant oceanic source of organic carbon aerosol
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 CD, Facchini MC, CavalliF, et al.
Biogenically driven organic contribution to marine aerosol
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]
VaitilingomM, AmatoP, SancelmeM, et al.
Contribution of microbial activity to carbon chemistry in clouds
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]
KawaharaH.
The structures and functions of ice crystal-controlling proteins from bacteria
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]
GandolfiI, BertoliniV, BestettiG,et al.
Spatio-temporal variability of airborne bacterial communities and their correlation with particulate matter chemical composition across two urban areas
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.
Spatial distribution of marine airborne bacterial communities
Influence of seasonality. Influence of seasonality, air mass origin and particulate matter chemical composition on airborne bacterial community structure in the Po Valley, Italy
Spatio-temporal variability of airborne bacterial communities and their correlation with particulate matter chemical composition across two urban areas