沙尘暴对北京市空气细菌多样性特征的影响

亚洲沙尘暴携带着各类污染物质,严重影响下风向地区大气过程及生态系统和相关人群的健康。然而,沙尘天气对中国华北地区空气细菌群落及多样性特征影响的研究较少。以北京市为例,系统研究了沙尘暴对城市空气细菌多样性特征的影响。2015年4月,通过定点采样连续收集了一次沙尘暴及其前后4天的空气颗粒物样本,DNA提取、PCR扩增后进行16S rRNA基因高通量测序。共获得169122条高质量序列,生物信息学分析表明,北京市空气细菌物种多样性较高,沙尘暴不能引起细菌OTU数目的增加,但沙尘暴天气下细菌群落Pielou、Shannon和Simpson指数显著增加。菌群分类分析发现,北京市空气细菌由35个细菌门构成,其中变形菌门(Proteobacteria)、放线菌门(Actinobacteria)、厚壁菌门(Firmicutes)和拟杆菌门(Bacteroidetes)相对丰度最高,分别占总序列的32.76%、28.09%、25.46%和6.32%;芽单胞菌门(Gemmatimonadetes)和酸杆菌门(Acidobacteria)次之,分别占序列总数的2.11%和1.81%,其他细菌门的相对丰度均低于1%。沙尘暴天气下,变形菌门(Proteobacteria)、拟杆菌门(Bacteroidetes)、芽单胞菌门(Gemmatimonadetes)和酸杆菌门(Acidobacteria)显著升高(P<0.05),分别由31.67%、5.74%、1.82%、1.51%升高至41.46%、10.98%、4.48%和4.26%;而放线菌门(Actinobacteria)、厚壁菌门(Firmicutes)显著降低(P <0.05),分别由28.84%、27.10%降低至22.13%和12.35%。冷杆菌属(Psychrobacter),纤维单胞菌属(Cellulomonas),不动杆菌属(Acinetobacter),假单胞菌属(Pseudomonas)和梭菌属(Clostridium)可能含有人类条件病原菌,其在沙尘暴天气中相对丰度下降,但绝对丰度会大幅增加。沙尘暴能降低人体免疫力,因此致病菌潜在健康风险可能显著增强。通过聚类分析和主成分分析发现,沙尘暴日与非沙尘暴日空气细菌群落差异较大,而沙尘暴前后群落结构差异较小。沙尘暴前后空气细菌群落α-多样性和β多样性均无显著差异,推测沙尘暴只能暂时影响空气细菌群落特征,不能显著改变其群落结构。本研究通过分析了沙尘暴侵袭下北京市空气细菌群落多样性特征及动态,为制定中国北方城市沙尘暴灾害预警措施和建立气传疾病的防控机制提供数据支持。     

麦积山石窟赋存环境中空气细菌的时空分布特征

【目的】空气微生物沉降及污染与文化遗产的微生物退化密切相关,本文对世界文化遗产地麦积山石窟赋存环境空气中细菌浓度和群落结构的季节性变化特征进行了系统研究,为石窟环境监测预警和文物预防性保护提供依据。【方法】利用生物气溶胶采样器,在2016年春、夏、秋和冬季分别采集空气样品;基于传统培养方法获得空气中细菌浓度及纯培养菌株;通过提取基因组DNA、扩增细菌16S rRNA、测序和系统发生树等分子技术研究细菌群落时空动态变化规律;结合环境监测数据,分析影响遗产地空气细菌变化的主要因素。【结果】监测期内,空气细菌浓度在(281.20–1409.20)CFU/m3之间,最高浓度出现在MJ4处的夏季,最低浓度出现在MJO处的春季;具有明显季节性变化特征,在空间层位分布上有所差异,但不显著(P0.05)。培养的细菌菌株经鉴定属于4个门11个属;芽孢杆菌属(Bacillus)、Paenarthrobacter、节杆菌属(Arthrobacter)、薄层菌属(Hymenobacter)和考克氏菌属(Kocuria)等为优势属。【结论】麦积山石窟空气细菌群落结构具有明显的季节性和空间分布动态变化特征;在石窟不同层位,空气中细菌群落分布与相对湿度、温度与降雨量相关;部分细菌种属如芽孢杆菌属、微球菌属(Micrococcus),为壁画及彩塑生物腐蚀的潜在病害菌;麦积山石窟及周边环境空气细菌的监测可为石窟保护和旅游开放管理提供重要参考。     

沙尘暴对北京市空气细菌多样性特征的影响

亚洲沙尘暴携带着各类污染物质,严重影响下风向地区大气过程及生态系统和相关人群的健康。然而,沙尘天气对中国华北地区空气细菌群落及多样性特征影响的研究较少。本文以北京市为例,系统研究了沙尘暴对城市空气细菌多样性特征的影响。2015年4月,通过定点采样连续收集了一次沙尘暴及其前后4天的空气颗粒物样本,DNA提取、PCR扩增后进行16S rRNA基因高通量测序。共获得169122条高质量序列,生物信息学分析表明,北京市空气细菌物种多样性较高,沙尘暴不能引起细菌OTU数目的增加,但沙尘暴天气下细菌群落Pielou、Shannon和Simpson指数显著增加。菌群分类分析发现,北京市空气细菌由35个细菌门构成,其中变形菌门(Proteobacteria)、放线菌门(Actinobacteria)、厚壁菌门(Firmicutes)和拟杆菌门(Bacteroidetes)相对丰度最高,分别占总序列的32.76%、28.09%、25.46%和6.32%;芽单胞菌门(Gemmatimonadetes)和酸杆菌门(Acidobacteria)次之,分别占序列总数的2.11%和1.81%,其他细菌门的相对丰度均低于1%。沙尘暴天气下,变形菌门(Proteobacteria)、拟杆菌门(Bacteroidetes)、芽单胞菌门(Gemmatimonadetes)和酸杆菌门(Acidobacteria)显著升高(P0.05),分别由31.67%、5.74%、1.82%、1.51%升高至41.46%、10.98%、4.48%和4.26%;而放线菌门(Actinobacteria)、厚壁菌门(Firmicutes)显著降低(P0.05),分别由28.84%、27.10%降低至22.13%和12.35%。冷杆菌属(Psychrobacter),纤维单胞菌属(Cellulomonas),不动杆菌属(Acinetobacter),假单胞菌属(Pseudomonas)和梭菌属(Clostridium)可能含有人类条件病原菌,其在沙尘暴天气中相对丰度下降,但绝对丰度会大幅增加。沙尘暴能降低人体免疫力,因此致病菌潜在健康风险可能显著增强。通过聚类分析和主成分分析发现,沙尘暴日与非沙尘暴日空气细菌群落差异较大,而沙尘暴前后群落结构差异较小。沙尘暴前后空气细菌群落α-多样性和β多样性均无显著差异,推测沙尘暴只能暂时影响空气细菌群落特征,不能显著改变其群落结构。本研究通过分析了沙尘暴侵袭下北京市空气细菌群落多样性特征及动态,为制定中国北方城市沙尘暴灾害预警措施和建立气传疾病的防控机制提供数据支持。     

天梯山石窟壁画保存环境中空气细菌的季节性变化

【背景】微生物侵蚀是古代壁画常见生物病害,影响壁画的长久保存和安全陈展。空气微生物作为壁画病害菌的主要来源,近年在文物赋存环境监测和预防性保护中引起广泛重视。【目的】对天梯山石窟壁画的2处保存地,即天梯山原址和武威西夏博物馆壁画保存环境中的空气细菌浓度、群落结构及其季节变化规律进行分析。【方法】利用生物气溶胶采样器,在2016年春、夏、秋、冬4季分别采集各位点空气样品;基于传统培养方法获得空气中细菌浓度及纯培养菌株;通过提取细菌基因组DNA、扩增其16S rRNA基因、测序和系统发生关系分析等技术研究不同位点细菌群落时空动态变化规律;结合环境监测数据,分析影响文化遗产地空气细菌群落变化的主要因素。【结果】空气可培养细菌的总浓度在16.7-1 451.8 CFU/m3范围内变动。原址第18窟和第13窟,各季节细菌浓度无显著性差异,且呈明显季节性变动规律,总体特征为夏秋季低,冬春季高。西夏博物馆外空气细菌浓度在各季节均高于库房内,冬季最高。本研究共鉴定出19个细菌属,隶属于4个门;其中不动杆菌属(Acinetobacter)、节杆菌属(Arthrobacter)、芽孢杆菌属(Bacillus)、考克氏菌属(Kocuria)、短波单胞菌属(Brevundimonas)、肉食杆菌属(Carnobacterium)、 Pseudoclavibacter和薄层菌属(Hymenobacter)为优势属。【结论】天梯山石窟空气细菌群落结构具有明显的时空分布特征;相对湿度、温度及季节性降水均会影响其变化;鉴定得到部分种属具备引起壁画生物腐蚀的潜势;本研究可为当地开展遗址和馆藏环境中文物预防性保护提供本底资料。     

三种高盐苯胺废水对细菌群落结构的影响

采用PCR-DGGE技术分析了含有不同CODCr、盐、总磷、氨态氮、氯离子、苯胺浓度的3种高盐苯胺废水(1#、2#、3#)驯化的细菌群落结构变化,从分子水平阐明高盐苯胺废水对细菌群落结构的影响.结果表明,不同浓度高盐苯胺废水驯化过程中,2#废水随着浓度的升高,细菌群落多样性逐渐下降;1#废水驯化的细菌群落多样性指数以5%的废水最高,20%与40%的废水最低;3#废水驯化的细菌群落多样性指数以0%和5%的废水最高,20%的废水最低.不同废水对细菌群落多样性有不同的影响,表明适应和突变是驯化过程中细菌适应环境的一个重要作用力.3种不同高盐苯胺废水驯化的细菌群落多样性指数与CODCr、盐含量之间均存在显著负相关,但与氯离子和苯胺含量之间相关不显著.3种废水驯化的细菌的遗传多样性有较大差异,多态位点百分率、Shannon's信息指数和Nei's指数均以3#废水最高,1#废水次之,2#废水最低.但遗传多样性指标与CODCr、盐含量、氯离子和苯胺含量之间均相关不显著.可知细菌群落多样性的变化是由于废水中所含的污染物质的综合作用结果,而非单一的因素.3种废水的5种不同浓度驯化细菌之间的平均遗传距离分别为0.4724、0.4350和0.4902,其中3#废水驯化的细菌遗传变异最大.聚类分析表明,5种不同浓度高盐苯胺废水驯化细菌均可明显地分为两组.1#和2#废水均为0%、5%和10%废水驯化细菌聚成一组,而20%和40%废水驯化细菌聚成另一组; 3#废水为0%与5%废水驯化细菌聚成一组,而10%、20%和40%废水驯化细菌聚成另一组.不同的废水由于水质背景值不同,选择压力不同,导致细菌突变的阈值不同,使得诱导细菌变异程度不同,从而最终引起细菌群落结构的不同.驯化过程中微生物种群的变化使得整个微生物群落能够快速适应外部环境变化.     

华北落叶松树皮表面细菌群落多样性及其分布格局

附生在树皮表面的微生物,对于宿主植物的健康和环境适应性发挥重要作用,树皮微生境中微生物群落结构和多样性及其维持机制有待关注。【目的】本文对庞泉沟自然保护区不同海拔梯度的华北落叶松树干的背阴面与向阳面的树皮表面细菌群落的分布特征和适应机制进行了研究。【方法】通过PCR-DGGE和高通量测序技术研究细菌群落特征,对树皮表面细菌群落的空间分布特征进行了非度量多维尺度(NMDS)排序分析,通过冗余分析(RDA)研究细菌群落与树皮表面理化性质的关系,单因素方差分析(One-way ANOVA)比较树皮背阴面与向阳面细菌群落组成,基于零偏差分析研究背阴面与向阳面细菌群落构建的驱动因素。【结果】不同海拔梯度间的细菌群落结构有显著性差异(ANOSIM;P<0.05),树皮表面的微环境因子p H和总碳(TC)与群落结构显著相关(P<0.05);向阳面树皮表面的光合自养型细菌(隶属于蓝细菌门的未命名的目)的相对丰度显著高于背阴面,而根瘤菌目的相对丰度呈相反的趋势,光照可能是引起细菌群落结构发生变化的驱动因子;零偏差分析结果表明,华北落叶松树皮背阴面、向阳面细菌群落的多样性格局主要受环境过滤的影响。【结论】环境因子主导的确定性过程是驱动该地区华北落叶松树皮表面细菌群落结构和多样性的主导因素。     

安徽省某酸性矿山废水坑湖中细菌群落的垂向分布特征及其影响因素

【目的】探究酸性矿山废水(acid mine drainage,AMD)坑湖中细菌群落沿垂向不同水深的分布规律及与环境因子之间的相互作用。【方法】采用16SrRNA基因高通量测序技术,对安徽省某AMD坑湖中6条采样垂线不同水深深度的细菌群落进行调查,同时测定水质理化指标,使用统计学软件分析细菌和地化参数间的联系。【结果】AMD坑湖中水质特征及细菌群落结构出现明显分层现象,自上而下溶解氧降低而pH和多种金属离子浓度增加,微生物群落结构发生变化,多样性和部分物种的丰度增大。细菌群落组成上,表层水域以Proteobacteria (Alpha、Gammaproteobacteria)和Acidobacteria占据主导地位;中下层水域则由Firmicutes、Acidobacteria、Actinobacteria、Gammaproteobacteria和Patescibacteria等共同主导。统计分析结果表明,TN、DO、ORP、pH、Fe、Mn、Al和Zn与嗜酸细菌丰度显著相关,是细菌空间分布的主要限制因素。【结论】AMD坑湖中水质理化特征和细菌群落分布在垂向空间上存在显著差异,群落的...     

施肥和土壤管理对土壤微生物生物量碳、氮和群落结构的影响

以中国科学院沈阳生态试验站的长期定位试验为平台,研究了不同施肥和土壤管理对潮棕壤微生物生物量碳、氮和群落结构的影响。结果表明,裸地和农田处理的微生物生物量碳、氮较低,但是农田处理下施肥增加了微生物生物量,其中NPK+M效果最明显。DGGE图谱显示,处理间细菌条带分布较相似,其中裸地的细菌多样性最高;长期施肥和土壤管理改变了土壤真菌群落结构,施肥增加了真菌多样性,且有机肥的影响大于化肥;不同处理间氨氧化细菌群落结构差异显著,NPK+M显著增加了氨氧化细菌多样性,且无机肥和有机肥对氨氧化细菌群落影响不同。施肥和土壤管理对细菌影响较小,但显著改变了真菌和氨氧化细菌的群落结构。聚类分析结果显示,土壤管理措施较施肥对细菌、真菌和氨氧化细菌群落的影响更为显著。     

象山港电厂温排水增温对浮游细菌群落空间分布的影响

沿海电厂产生的温排水已造成了较严重的环境问题,如生物病害和赤潮暴发频率增加。现有研究多关注温排水增温对浮游动、植物多样性的影响,而缺乏在物质能量循环过程起核心纽带作用的微生物对增温的响应和反馈。考虑到生态系统对增温的反馈取决于浮游植物的初级生产力和微生物异养呼吸之间的平衡,利用Illumina测序技术结合水体理化性质研究了象山港电厂温排水增温梯度下浮游细菌的空间分布特征。温排水预期的海水增温显著地增加了水体中硝氮(P=0.041,单因素方差分析)、化学需氧量(P0.001)、油污(P=0.004)和余氯(P=0.003)的浓度;但降低了溶解氧(P=0.034)和叶绿素a(P=0.045)的含量。此外,相似性分析发现温排水增温显著地(r=0.338;P=0.042)改变了浮游细菌群落结构,空间分布遵循空间距离-群落相似性衰减(r=-0.582;P=0.026)模型,周转速率为0.0013。细菌多样性主要受水体溶解氧、化学需要量和叶绿素a的影响,分别控制了34.6%、20.1%和10.0%的多样性变异。冗余分析(RDA)群落变异主要受环境因子(包括温度、油污、溶解氧和叶绿素a)的影响,一共解释了55.6%的群落变异;增温仅解释了4.8%的群落变异。因此,浮游细菌群落结构主要受环境因子的影响,这种各因子对群落变异相对贡献比例的特征与增温主要通过改变水质和浮游植物特征,以间接作用影响细菌群落组成的观念一致。此外,细菌多样性和群落组成受不同环境因子的驱动。相比而言,空间距离只控制了较小比例的群落变异(7.1%)。此外,筛选到11个细菌科,这些科的相对丰度与增温幅度显著相关,变化特征与各科已知的生态功能相吻合,如海洋螺菌科(Oceanospirillaceae)中有些菌株能够降解石油污染物,其相对丰度在高油污浓度站点增加(油污浓度与增温幅度正相关,r=0.558;P=0.030);嗜温的弧菌科相对丰度与增温幅度正相关。综上,研究结果初步明确了浮游细菌群落对电厂温排水增温的响应特征,并筛选到敏感的细菌科来指示和预测增温对生态功能的潜在影响。     

保安湖水体细菌群落结构时空变化特征及驱动因子

为了探究保安湖水体细菌群落结构时空变化特征及驱动因子,研究于2019年春、夏、秋、冬四季采集保安湖水样,使用宏基因组测序技术对保安湖水体细菌群落的组成及多样性变化进行了研究。结果表明:(1)保安湖不同湖区细菌群落组成无显著差异(P>0.05);夏、秋季细菌丰富度、均匀度、香农及辛普森多样性指数均显著高于春、冬季(P<0.05),夏、秋季优势类群为变形菌门(Proteobacteria)、放线菌门(Actinobactetiota)、蓝藻门(Cyanobacteria),而春、冬季变形菌门(Proteobacteria)和放线菌门(Actinobactetiota)占主导地位;(2)温度、透明度、pH、溶解氧、高锰酸盐指数、叶绿素a及总磷等因素是保安湖水体细菌群落结构变化的重要驱动因子;(3)保安湖细菌群落构建过程在春、夏、秋季由随机性过程主导,在冬季由确定性过程主导;(4)保安湖细菌网络互作具有明显的季节特征,从春季到冬季,保安湖细菌种间相互作用逐渐紧密复杂。综上所述,保安湖水体细菌群落结构具有明显的季节变化特征,温度、透明度、pH、溶解氧、高锰酸盐指数等因素具有驱动水体细...     

Sources of bacteria in outdoor air across cities in the midwestern United States

Bacteria are abundant in the atmosphere, where they often represent a major portion of the organic aerosols. Potential pathogens of plants and livestock are commonly dispersed through the atmosphere, and airborne bacteria can have important effects on human health as pathogens or triggers of allergic asthma and seasonal allergies. Despite their importance, the diversity and biogeography of airborne microorganisms remain poorly understood. We used high-throughput pyrosequencing to analyze bacterial communities present in the aerosol fraction containing fine particulate matter of ≤2.5 μm from 96 near-surface atmospheric samples collected from cities throughout the midwestern United States and found that the communities are surprisingly diverse and strongly affected by the season. We also directly compared the airborne communities to those found in hundreds of samples representing potential source environments. We show that, in addition to the more predictable sources (soils and leaf surfaces), fecal material, most likely dog feces, often represents an unexpected source of bacteria in the atmosphere at more urbanized locations during the winter. Airborne bacteria are clearly an important, but understudied, component of air quality that needs to be better integrated into efforts to measure and model pollutants in the atmosphere.     

Human occupancy as a source of indoor airborne bacteria

Exposure to specific airborne bacteria indoors is linked to infectious and noninfectious adverse health outcomes. However, the sources and origins of bacteria suspended in indoor air are not well understood. This study presents evidence for elevated concentrations of indoor airborne bacteria due to human occupancy, and investigates the sources of these bacteria. Samples were collected in a university classroom while occupied and when vacant. The total particle mass concentration, bacterial genome concentration, and bacterial phylogenetic populations were characterized in indoor, outdoor, and ventilation duct supply air, as well as in the dust of ventilation system filters and in floor dust. Occupancy increased the total aerosol mass and bacterial genome concentration in indoor air PM(10) and PM(2.5) size fractions, with an increase of nearly two orders of magnitude in airborne bacterial genome concentration in PM(10). On a per mass basis, floor dust was enriched in bacterial genomes compared to airborne particles. Quantitative comparisons between bacterial populations in indoor air and potential sources suggest that resuspended floor dust is an important contributor to bacterial aerosol populations during occupancy. Experiments that controlled for resuspension from the floor implies that direct human shedding may also significantly impact the concentration of indoor airborne particles. The high content of bacteria specific to the skin, nostrils, and hair of humans found in indoor air and in floor dust indicates that floors are an important reservoir of human-associated bacteria, and that the direct particle shedding of desquamated skin cells and their subsequent resuspension strongly influenced the airborne bacteria population structure in this human-occupied environment. Inhalation exposure to microbes shed by other current or previous human occupants may occur in communal indoor environments.     

Particle size distribution of cultivable airborne microbes and inhalable particulate matter in a wastewater treatment plant facility

A field study was performed to identify the size distribution characteristics of viable, cultivable airborne microorganisms (heterotrophic bacteria, fungi, and total coliforms) at a municipal wastewater treatment facility, and their association with inhalable particulate matter (PM₁, PM_2.5, and PM₁₀), as well as hydrogen sulfide concentrations and ambient meteorological parameters. The highest concentrations of cultivable, airborne heterotrophic bacteria, total coliforms, mass and number concentration of particulate matter, as well as hydrogen sulfide were observed at the aerated grit removal chambers at the pretreatment stage (3 to 2030 times higher than the values of the background ambient air). In contrast, the mean concentrations of cultivable, airborne mesophilic fungi at the aerated grit chambers were 0.6 time lower than the background site, where fungi presented the most abundant taxonomic group in the ambient air. Although the highest concentrations of the airborne fungi were determined at aerodynamic diameters between 2.1 and 3.3 μm, a nearly equal distribution of the mean concentrations of the cultivable, airborne heterotrophic bacteria were observed in the six different size fractions at the primary settling tanks and in the ambient air. Interestingly, their size distribution profiles at the aerated grit chambers were different and showed a maximum aerodynamic diameter at the size range from 3.3 to 4.7 μm, similar to that of the cultivable, airborne total coliforms. In general, low positive or no significant linear relationships could be found between the cultivable airborne heterotrophic bacteria, total coliforms, or fungi at the two wastewater treatment stages and the ambient background microbial community.     

Architectural design influences the diversity and structure of the built environment microbiome

Buildings are complex ecosystems that house trillions of microorganisms interacting with each other, with humans and with their environment. Understanding the ecological and evolutionary processes that determine the diversity and composition of the built environment microbiome—the community of microorganisms that live indoors—is important for understanding the relationship between building design, biodiversity and human health. In this study, we used high-throughput sequencing of the bacterial 16S rRNA gene to quantify relationships between building attributes and airborne bacterial communities at a health-care facility. We quantified airborne bacterial community structure and environmental conditions in patient rooms exposed to mechanical or window ventilation and in outdoor air. The phylogenetic diversity of airborne bacterial communities was lower indoors than outdoors, and mechanically ventilated rooms contained less diverse microbial communities than did window-ventilated rooms. Bacterial communities in indoor environments contained many taxa that are absent or rare outdoors, including taxa closely related to potential human pathogens. Building attributes, specifically the source of ventilation air, airflow rates, relative humidity and temperature, were correlated with the diversity and composition of indoor bacterial communities. The relative abundance of bacteria closely related to human pathogens was higher indoors than outdoors, and higher in rooms with lower airflow rates and lower relative humidity. The observed relationship between building design and airborne bacterial diversity suggests that we can manage indoor environments, altering through building design and operation the community of microbial species that potentially colonize the human microbiome during our time indoors.     

Abundance and Diversity of Glacial Bacteria on the Tibetan Plateau with Environment

The relation of glacial microorganism and their living environment is concerned but less understood for both glaciologists and microbiologists. Here we present the results about glacial snow bacteria from 3 glaciers on the Tibetan Plateau. The concentrations and diversity of bacteria collected from snow pit samples of East Rongbuk, Laohugou and Hailuogou glaciers on the Tibetan Plateau were investigated by epifluorescence microscope, denaturing gradient gel electrophoresis and Shannon-Weaver index. Concentrations and community diversity of bacteria in the East Rongbuk glacier with lower concentration and smaller size of microparticle were lower than in the Laohugou with higher concentration and larger size of microparticle. Bacterial concentration in East Rongbuk Glacier was close to that in polar regions, suggesting that Mt. Everest is a bacterial background for remote regions away from direct influence of anthropogenic sources. In addition, altitude difference was another factor for higher concentrations and community diversity of bacteria in Hailuogou and Laohugou glaciers than in East Rongbuk Glacier. The highest concentrations and community diversity of bacteria in Hailuogou Glacier were attributed to its most diverse atmospheric circulations and highest temperature among the 3 glaciers. We suggest a complicated correlation between glacial bacteria and their regional living environments.     

北京城市空气细菌群落结构与动态变化特征

在北京市选择3个典型的功能区,通过定点系统取样,运用BIOLOG鉴定技术,着重研究了北京城市空气细菌的群落结构与动态变化特征。结果表明:北京市空气中革兰氏阳性菌明显多于革兰氏阴性菌,约占80%~85%,其中阳性球菌占总数的50%~55%。不同功能区共发现47属空气细菌,其中革兰氏阳性菌31属,革兰氏阴性菌16属。优势菌属依次为微球菌属(Micrococcus)、葡萄球菌属(Staphylococcus)、芽孢杆菌属(Bacillus)、棒杆菌属(Corynebacterium)和假单胞菌属(Pseudomonas),它们总和约占50%。在优势菌属中,微球菌属约占总数的20%~30%,是北京市空气中比例最大的菌属,假单胞菌属约占2.5%~5.0%。文教区和交通干线细菌浓度明显高于公园绿地(P<0.01);并且文教区和交通干线空气细菌浓度四季变化特征显著,夏季和秋季较高,春季和冬季较低,公园绿地空气细菌浓度四季没有显著差异;3个功能区13:00时的细菌浓度明显低于9:00时和17:00。     

Unravelling the bacterial diversity in the atmosphere

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.     

Differing growth responses of major phylogenetic groups of marine bacteria to natural phytoplankton blooms in the western North Pacific Ocean

Growth and productivity of phytoplankton substantially change organic matter characteristics, which affect bacterial abundance, productivity, and community structure in aquatic ecosystems. We analyzed bacterial community structures and measured activities inside and outside phytoplankton blooms in the western North Pacific Ocean by using bromodeoxyuridine immunocytochemistry and fluorescence in situ hybridization (BIC-FISH). Roseobacter/Rhodobacter, SAR11, Betaproteobacteria, Alteromonas, SAR86, and Bacteroidetes responded differently to changes in organic matter supply. Roseobacter/Rhodobacter bacteria remained widespread, active, and proliferating despite large fluctuations in organic matter and chlorophyll a (Chl-a) concentrations. The relative contribution of Bacteroidetes to total bacterial production was consistently high. Furthermore, we documented the unexpectedly large contribution of Alteromonas to total bacterial production in the bloom. Bacterial abundance, productivity, and growth potential (the proportion of growing cells in a population) were significantly correlated with Chl-a and particulate organic carbon concentrations. Canonical correspondence analysis showed that organic matter supply was critical for determining bacterial community structures. The growth potential of each bacterial group as a function of Chl-a concentration showed a bell-shaped distribution, indicating an optimal organic matter concentration to promote growth. The growth of Alteromonas and Betaproteobacteria was especially strongly correlated with organic matter supply. These data elucidate the distinctive ecological role of major bacterial taxa in organic matter cycling during open ocean phytoplankton blooms.     

The contribution of marine aggregate‐associated bacteria to the accumulation of pathogenic bacteria in oysters: an agent‐based model

Bivalves process large volumes of water, leading to their accumulation of bacteria, including potential human pathogens (e.g., vibrios). These bacteria are captured at low efficiencies when freely suspended in the water column, but they also attach to marine aggregates, which are captured with near 100% efficiency. For this reason, and because they are often enriched with heterotrophic bacteria, marine aggregates have been hypothesized to function as important transporters of bacteria into bivalves. The relative contribution of aggregates and unattached bacteria to the accumulation of these cells, however, is unknown. We developed an agent‐based model to simulate accumulation of vibrio‐type bacteria in oysters. Simulations were conducted over a realistic range of concentrations of bacteria and aggregates and incorporated the dependence of pseudofeces production on particulate matter. The model shows that the contribution of aggregate‐attached bacteria depends strongly on the unattached bacteria, which form the colonization pool for aggregates and are directly captured by the simulated oysters. The concentration of aggregates is also important, but its effect depends on the concentration of unattached bacteria. At high bacterial concentrations, aggregates contribute the majority of bacteria in the oysters. At low concentrations of unattached bacteria, aggregates have a neutral or even a slightly negative effect on bacterial accumulation. These results provide the first evidence suggesting that the concentration of aggregates could influence uptake of pathogenic bacteria in bivalves and show that the tendency of a bacterial species to remain attached to aggregates is a key factor for understanding species‐specific accumulation.