河口细菌群落多样性及其控制因素:以切萨皮克湾为例

咸淡水的混合和重要营养盐与有机物的再循环,使得河口成为地球上生产力较高而动态变化明显的水生生态系统.一个典型的河口区断面中,细菌群落包含了一些从淡水到海洋的过渡类型:例如α-变形菌(Alphaproteobacteria)、p-变形菌(Betaproteobacteria)、γ-变形菌(Gammaproteobacteria)、蓝细菌(Cyanobactenia)[聚球藻(Synechococcus)]、拟杆菌(Bacteroidetes)、放线细菌(Actinobacteria)和疣微菌(Verrucomicrobia)等.此外,河口也包含其独特的细菌群落:SAR11组、玫瑰杆菌属(Roseobacter)、SAR86和放线细菌(Actinobacteria)的一些进化亚枝(subclades),表明海湾或者大型温带河口区细菌类群具有区域生态适应性.以研究较多的美国切萨皮克湾(Chesapeake Bay)为例,其细菌群落呈现出显著的季节性变化和周期性的年际变化特征;这些变化除了受水的滞留时间和细菌生长速度影响外,还可能受其他许多环境因子的影响.其中叶绿素a和水温变化的影响最大,其他环境因子如溶解氧、铵态氮、亚硝酸盐和硝酸盐以及病毒的丰度也有影响.近年来,基于群落水平的基因组学(genomics)和后基因组学(postgenomics)(转录组学和蛋白质组学)技术应用于研究自然条件下微生物群落错综复杂的基因多样性和表达,提供了揭示水环境中微生物群落组成和新功能基因的途径.     

洪潮江水库浮游细菌群落空间分布及其与环境因子的关系

【目的】为了解洪潮江水库浮游细菌群落组成、空间分布及其与环境因子的相互作用关系。【方法】基于16S rRNA基因高通量测序技术,对洪潮江水库浮游细菌群落结构与多样性进行了分析,同步对水体的理化指标进行检测。【结果】洪潮江水库共注释浮游细菌28门79纲168目243科325属85种。优势门为变形菌门、放线菌门、蓝细菌门、疣微菌门、拟杆菌门、浮霉菌门,分别占比21.95%、21.30%、17.98%、12.27%、11.72%、9.51%。基于Bray-Curtis距离的PCoA分析表明,洪潮江水库9个采样点可以被分为3组,细菌群落呈现沿上下游梯度变化的趋势。perMANOVA检验显示,各组差异显著,但是各组的多样性指数没有显著性差异。Mantel分析表明,透明度、浊度、总磷、亚硝酸盐氮、硝酸盐氮、叶绿素a、pH、溶解氧、氧化还原电位、比电导、总溶解固体以及营养状态会显著影响浮游细菌群落结构。【结论】洪潮江水库浮游细菌空间分布特征是自然环境理化因子和农业活动综合作用的结果。研究结果对了解浮游细菌群落空间格局及其对人类活动的响应,以及水库管理具有科学参考价值。     

Effect of Campsurus notatus on NH+4, DOC Fluxes,O2 Uptake and Bacterioplankton Production in Experimental Microcosms with Sediment‐Water Interface of an Amazonian Lake Impacted by Bauxite Tailings

The aim of this study was to evaluate the influence of Campusurus notatus Eaton 1868 (Ephemeroptera: Polimitarciydae) and the impact of bauxite tailings on ammonium (NH₄⁺) and dissolved organic carbon (DOC) fluxes, oxygen uptake and bacterioplankton production in the sediment‐water interface of Lake Batata, a shallow Amazonian floodplain lake. Mesocosms were constructed from natural and impacted areas of Lake Batata, to reproduce the sediment‐water interface. The cores were incubated with 0 to 2,388 ind m^–2 of Campsurus notatus nymphs, and the changes in NH₄⁺, DOC, O₂ concentration and bacterioplankton production in the overlying water column were measured. Ammonium efflux (F = 9.8, p < 0.05, multiple regression) and oxygen uptake (F = 11.8, p < 0.05) showed a significant correlation with the density of C. notatus in the cores with natural sediment. No differences on DOC release were observed in cores with natural or impacted sediment. In the cores incubated with natural sediment and nymphs of C. notatus, a significant increase (Two‐way ANOVA, p < 0.05) in bacterial production (0.44 μg C l^–1 h^–1) was observed after 3 hours of incubation. In cores incubated with sediment impacted by bauxite tailings, there was no difference in bacterial production with and without C. notatus. We conclude that C. notatus is an important bioturbator in Lake Batata, increasing the turnover rate of nitrogen (NH₄⁺) at the sediment‐water interface and bacterial production in cores incubated with natural sediment. It is also clear that bauxite tailings reduce the nutrients turnover rates in impacted regions of Lake Batata and influence bacterial production.     

Candidatus Abditibacter,a novel genus within the Cryomorphaceae,thriving in the North Sea

Coastal phytoplankton blooms are frequently followed by successive blooms of heterotrophic bacterial clades. The class Flavobacteriia within the Bacteroidetes has been shown to play an important role in the degradation of high molecular weight substrates that become available in the later stages of such blooms. One of the flavobacterial clades repeatedly observed over the course of several years during phytoplankton blooms off the coast of Helgoland, North Sea, is Vis6. This genus-level clade belongs to the family Cryomorphaceae and has been resistant to cultivation to date. Based on metagenome assembled genomes, comparative 16S rRNA gene sequence analyses and fluorescence in situ hybridization, we here propose a novel candidate genus Abditibacter, comprising three novel species Candidatus Abditibacter vernus, Candidatus Abditibacter forsetii and Candidatus Abditibacter autumni. While the small genomes of the three novel photoheterotrophic species encode highly similar gene repertoires, including genes for degradation of proteins and algal storage polysaccharides such as laminarin, two of them – Ca. A. vernus and Ca. A. forsetii – seem to have a preference for spring blooms, while Ca. A. autumni almost exclusively occurs in late summer and autumn.     

南黄海潮汐锋对浮游细菌生物量分布的影响

2 0 0 1年 5月 16～ 2 3日、6月 10～ 2 4日和 2 0 0 2年 6月 5～ 12日 ,利用“北斗号”船只对南黄海鱼产卵场进行了 3次专项调查。研究了潮汐锋断面叶绿素 a浓度、浮游细菌生物量的分布 ,目的是阐明潮汐锋的存在对浮游细菌生物量分布的影响。3个航次中的叶绿素 a浓度变化范围分别是 0 .0 6～ 2 .34mg/ m3(2 0 0 1- 0 5 )、0 .0 8～ 0 .9mg/ m3(2 0 0 1- 0 6 )、0 .14～ 3.0 4 mg/ m3(2 0 0 2 - 0 6 )。 3航次的聚球藻 (Synechococcus spp.)蓝细菌生物量变化范围分别为 7.6 2～ 2 2 .0 6 mg C/ m3(2 0 0 1- 0 5 )、8.5 3～2 7.5 2 mg C/ m3(2 0 0 1- 0 6 )、0 .6 9～ 5 5 .90 m g C/ m3(2 0 0 1- 0 6 )。异养细菌生物量变化范围分别为 7.5 6～ 5 1.82 mg C/ m3(2 0 0 1-0 5 )、8.5 4～ 2 4 .77mg C/ m3(2 0 0 1- 0 6 )、3.12～ 10 .0 5 mg C/ m3(2 0 0 2 - 0 6 )。而聚球藻蓝细菌对浮游植物总生物量的贡献 (CB:PB)平均值分别为 :5 8% (2 0 0 1- 0 5 )、77% (2 0 0 1- 0 6 )、31% (2 0 0 2 - 0 6 )。结果表明 :南黄海鱼产卵场在春末夏初 (5～ 6月份 ) ,叶绿素 a浓度最大值及次大值主要分布在锋区及其邻近的层化区2 0 m以浅位置 ;聚球藻蓝细菌生物量最大值主要分布于锋区及层化区表层和水体中层 ;异养     

Effective isolation of bacterioplankton genus Polynucleobacter from freshwater environments grown on photochemically degraded dissolved organic matter

Effective isolation of freshwater bacterioplankton belonging to genus Polynucleobacter from a shallow eutrophic lake and its tributary was achieved by size-selective filtration with a 0.7-μm pore filter and cultivation on R2A agar medium. Partial 16S rRNA gene analysis showed that over 80% of all the strains were highly similar to the Polynucleobacter cluster. Essential medium components for effective cultivation are pyruvate, yeast extract and peptone, whereas soluble starch and glucose are not necessary. Isolate KF001 (affiliated with Polynucleobacter subcluster D) has a strict requirement for organic acids as carbon sources, and we hypothesize that the Polynucleobacter cluster of bacteria could utilize compounds formed via photochemically dissolved organic matter (DOM) degradation for growth. Because organic acids form from solar radiation of DOM in aquatic environments, carbon sources that are typical products of DOM photochemical degradation were added to the medium. These compounds were readily utilized by KF001 in this study. Finally, we observed the stimulation of strain KF001 activity by photochemical degradation of natural lake water. Our findings suggest a carbon flow of DOM photoproducts to Polynucleobacter in the freshwater microbial loop.     

Seasonal and spatial distribution of bacterial production and biomass along a salinity gradient (Northern Adriatic Sea)

The Adriatic Sea is a semi-enclosed ecosystem that receives in itsshallow part, the northern basin, significant freshwater inputs whichmarkedly increase its productivity with respect to the oligotrophic featuresof the Mediterranean sea. In this area, especially on the western coastwhere river plumes diffuse, high physical (density) and chemical (nutrients)gradients occur on a small scale, both horizontal and vertical. Results ofbacterial production as ³H-thymidine incorporation, bacterialabundance as DAPI direct count, autotrophic biomass as chlorophyll a andtotal biomass as ATP from three areas in the Northern Adriatic Sea arereported. The three sites, differently influenced by the river waterdiffusion, were sampled seasonally over two days, every 24 h, in foursurveys from April 1995 to January 1996. Bacterioplankton production,strongly correlated with primary production, was extremely high near thecoast in low-salinity, high-nutrient waters, mostly as an indirectconsequence of riverine inputs causing an increase in phytoplanktonproduction stimulated by physically driven nutrient inputs. In the warmmonths bacterial activity was higher than in cold months. While bacteriaabundance did not appear related to the salinity gradients, bacterialproduction (from 0.6 to 372 pM ³H-thymidine h^™1incorporated, corresponding to 0.01–8.2 μg C l^™1h^™1) and the relative generation times (from 0.2 to 35 days)showed a high range of values, representing a variety of situations, fromestuaries to the ocean. The resulting role of the bacterial community in thecarbon cycle is very consistent, processing amounts of carbon which havebeen estimated as high as the 80% and the 260% of thosesynthesized by autotrophs in summer and winter, respectively. This revised version was published online in July 2006 with corrections to the Cover Date.     

Temporal plankton dynamics in an oligotrophic maritime Antarctic lake

• 1 The population density, diversity and productivity of the microbial plankton in an oligotrophic maritime Antarctic lake were studied for a 15‐month period between December 1994 and February 1996.
• 2 In the lake, concentrations of nutrients and dissolved organic carbon were uniformly low, temperature varied over a small annual range of 0.1–3 °C, and the surface was ice‐covered except during a period of approximately 6 weeks in summer.
• 3 The total of 57 morphotypes of protozoa observed during the study is a higher taxonomic diversity than previously reported from continental Antarctic lakes, but lower than that found in more eutrophic maritime Antarctic lakes. Likewise, planktonic abundance and productivity were lower than has been reported in other lakes on Signy Island, but generally higher than those of lakes on the Antarctic continent.
• 4 There were marked seasonal and interannual variations in planktonic population density.
• 5 Chlorophyll a concentrations ranged from undetectable to 4.2 µg L^‐1 and the greatest rate of primary productivity measured was 4.5 mg C m^‐3 h^‐1. The phytoplankton was dominated by small chlorophytes and chrysophytes, with phototrophic nanoflagellate abundance ranging from 1.1 × 10³ to 1.2 × 10⁷ L^‐1.
• 6 Bacterial densities of 3.6 × 10⁸ to 1.9 × 10¹⁰ L^‐1 were recorded and bacterial productivity reached a peak of 0.36 µg C L^‐1 h^‐1. Numbers of heterotrophic nanoflagellates between 5.0 × 10⁴ and 1.8 × 10⁷ L^‐1, and of ciliates from undetectable to 1.1 × 10⁴ L^‐1 were observed. Naked amoebae were usually rare, but occasionally reached peaks of up to 1.5 × 10³ L^‐1.