再生水补水对河道底泥细菌群落结构的影响

以北京市永定河麻峪湿地再生水补水口附近河道底泥为研究对象,应用末端限制性片段长度多态性(Terminal Restriction Fragment Length Polymorphism,T-RFLP)技术探究再生水补水口附近底泥细菌群落结构的空间差异特征以及环境因子所产生的影响,并借助典范对应分析(Canonical Correspondence Analysis,CCA)方法分析麻峪湿地底泥细菌群落结构空间差异特征的形成原因。分析结果表明:河道底泥微生物群落对再生水的净化主要发生在距补水口1200m的范围内,随着再生水与上游来水径向混合净化渐变过程,在补水口2000m处河道底泥微生物群落结构与河道再生水补水口上游趋于相似。基于样点聚类结果的群落结构多样性分析表明随着再生水净化过程的实现微生物综合多样性指数呈现下降的趋势,从均匀度指数的变化趋势看,再生水补水口具有最高均匀度指数,补水口下游1200米处由于非优势菌群所占相对丰度最低以及偶见菌群缺失,导致群落结构比较单一、群落多样性和均匀度指数都最低。CCA方面分析结果表明再生水补水口上游细菌群落与因累积效应形成的重金属有密切关系,补水口出口底泥细菌群落则主要受到总磷和总有机碳的影响较大,而再生水补水与上游来水汇水径向渐变过程可能与氨氮净化具密切关系。研究区的主要优势菌种为假单胞菌属、贪食菌属和芽孢杆菌属,是与再生水中有机碳、氮降解具有密切关系的菌属。     

16S rRNA gene analyses of bacterial community structures in the soils of evergreen broad-leaved forests in south-west China

Bacterial community structure was studied in humus and mineral soils of evergreen broad-leaved forests in Ailaoshan and Xishuangbanna, representing subtropical and tropical ecosystems, respectively, in south-west China using sequence analysis and terminal restriction fragment length polymorphism (T-RFLP) analysis of 16S rRNA genes. Clone sequences affiliated to Acidobacteria were retrieved as the predominant bacterial phylum in both forest soils, followed by those affiliated to members of the Proteobacteria, Planctomycete and Verrucomicrobia. Despite higher floristic richness at the Xishuangbanna forest than at the Ailaoshan forest, soil at Xishuangbanna harbored a distinctly high relative abundance of Acidobacteria-affiliated sequences (80% of the total clones), which led to a lower overall bacterial diversity than at Ailaoshan. Bacterial communities in humus and mineral soils of the two forests appeared to be well differentiated, based on 16S rRNA gene phylogeny, and correlations were found between the bacterial T-RFLP community patterns and the organic carbon and nutrient contents of the soil samples. The data reveal that Acidobacteria dominate soil bacterial communities in the evergreen broad-leaved forests studied here and suggest that bacterial diversity may be influenced by soil carbon and nutrient levels, but is not related to floristic richness along the climatic gradient from subtropical to tropical forests in south-west China.     

降水变化驱动下红松阔叶林土壤真菌多样性的分布格局

红松阔叶林生态系统是中国东北地区地带性顶极植被,具有重要的生态学意义,长白山是研究温带森林对大气降水变化正负反馈的理想地带.本文以长白山原始红松阔叶林为研究对象,基于末端限制性片段长度多态性分析技术,分析了降水控制样地(增、减30％)和对照样地的0 ～5 cm和5～ 10 cm表层土和红松根际土真菌多样性的空间异质性.结果表明:降水的增加和减少均能提高土壤真菌的多样性,但优势种群有所变化.表层土中,片段长度超过500 bp的T-RFs丰度随降水增加而提高,根际土中对降水变化响应的T-RFs分别为380、455和487 bp,且根际土的响应模式较表层土复杂.典范对应分析结果表明,土壤pH、有机碳含量、总氮和有效磷等对真菌群落组成影响显著.     

藻华爆发期太湖不同区域沉积物细菌多样性

本研究以藻华爆发期的太湖不同区域沉积物为对象, 测定氮、磷和生物量碳等理化性质, 并通过末端限制性酶切片断长度多态性分析(T-RFLP)的分子生态学手段, 鉴定不同富营养化湖区7个标准采样位点沉积物中细菌群落结构差异。结果表明, 总氮、总磷含量以6#、16#样品最高, 且各形态氮和各形态磷的趋势也与总氮、总磷趋势基本一致; 生物量碳为6#和16#明显高于其他位点, 其余各位点相近。T-RFLP结果显示, 各位点细菌多样性间存在差异, 其中16#样品的多样性指数最低, 6#、7#和1#较高; 在种群组成上各个位点无论是组分还是比例均有显著差异。另外, 所取7个沉积物样品中与氮、磷循环相关的α、β和γ-变形菌纲含量非常丰富, 且与硫、铁循环相关的δ-变形菌纲含量也很丰富。     

Possible interactions between bacterial diversity,microbial activity and supraglacial hydrology of cryoconite holes in Svalbard

The diversity of highly active bacterial communities in cryoconite holes on three Arctic glaciers in Svalbard was investigated using terminal restriction fragment length polymorphism (T-RFLP) of the 16S rRNA locus. Construction and sequencing of clone libraries allowed several members of these communities to be identified, with Proteobacteria being the dominant one, followed by Cyanobacteria and Bacteroidetes. T-RFLP data revealed significantly different communities in holes on the (cold) valley glacier Austre Brøggerbreen relative to two adjacent (polythermal) valley glaciers, Midtre Lovénbreen and Vestre Brøggerbreen. These population compositions correlate with differences in organic matter content, temperature and the metabolic activity of microbial communities concerned. No within-glacier spatial patterns were observed in the communities identified over the 2-year period and with the 1 km-spaced sampling. We infer that surface hydrology is an important factor in the development of cryoconite bacterial communities.     

环境因素对东平湖沉积物细菌群落结构的影响

【目的】探讨环境因素对东平湖沉积物细菌群落结构的影响。【方法】应用T-RFLP(Terminal RestrictionFragment Length Polymorphism)技术分析和比较了6个不同位置的东平湖沉积物在丰水期和枯水期的细菌多样性,并结合不同样品环境因子的差异,采用主成分分析(PCA)和典型对应分析(CCA),探讨了环境因子对细菌多样性的影响。【结果】不同沉积物样品的T-RFLP图谱具有较高的相似性。除2号样品外,所有枯水期样品的细菌群落具有较高的丰富度、多样性、均匀度和较低的优势度。CCA结果表明,558bp T-RF的丰度与总磷、总氮、总有机碳、铵态氮和硝态氮含量呈负相关而与碳氮比和水深呈正相关;64.5、164、509和543bp T-RFs的丰度与总氮、总有机碳、铵态氮、硝态氮、碳氮比和水深呈正相关;而其它14种主要的T-RFs在不同样品间分布较为稳定受环境因子影响不大。90、136.5、138和488bp等T-RFs可能代表了东平湖沉积物中占优势地位的土著菌群。通过Phylogenetic Assignment Tool在线分析结果推测,东平湖沉积物中的优势菌群可能属于Firmicutes和Proteobacteria门。【结论】环境因素对东平湖沉积物的细菌多样性产生显著影响,但对其土著菌群的影响不大。     

Soil parent material is a key determinant of the bacterial community structure in arable soils

The bacterial community composition in soil and rhizosphere taken from arable field sites, differing in soil parent material and soil texture, was analyzed using terminal restriction fragment length polymorphism (T-RFLP) of 16S rRNA genes. Nine sandy to silty soils from North-East Germany could clearly be distinguished from each other, with a relatively low heterogeneity in the community structure within the field replicates. There was a relationship between the soil parent material, i.e. different glacial and aeolian sediments, and the clustering of the profiles from different sites. A site-specific grouping of T-RFLP profiles was also found for the rhizosphere samples of the same field sites that were planted with potatoes. The branching of the rhizosphere profiles corresponded partly with the soil parent material, whereas the effect of the plant genotype was negligible. Selected terminal restriction fragments differing in their relative abundance within the nine soils were analyzed based on the cloning of the 16S rRNA genes of one soil sample. A high phylogenetic diversity observed to include Acidobacteria, Betaproteobacteria, Bacteroidetes, Verrucomicrobia, and Gemmatimonadetes. The assignment of three out of the seven selected terminal restriction fragments to members of Acidobacteria suggested that this group seems to participate frequently in the shifting of community structures that result from soil property changes.     

Linking denitrifier community structure and prevalent biogeochemical parameters in the pelagial of the central Baltic Proper (Baltic Sea)

The oxic-anoxic interface of the water column of the Gotland Basin (central Baltic Sea) is characterised by defined biogeochemical gradients and is hypothesised to be a zone of pronounced denitrification. Our aim was to analyse the composition and distribution of pelagic denitrifying microorganisms in relation to the physico-chemical gradients in the water column. PCR-amplified nirS genes--coding for dissimilatory nitrite reductase--were analysed as functional markers by terminal restriction fragment length polymorphism and cloning. The overall nirS diversity was low, with the lowest levels found at the oxic-anoxic interface. Only a few terminal restriction fragments dominated the denitrifier communities throughout the water column, and these could be assigned to several new Baltic Sea clusters that were revealed by phylogenetic analysis. The novel clusters were separated in two groups corresponding to the oxygen concentrations within specific layers of the water column. Gradients of prevalent biogeochemical parameters (H(2)S, NH(4) (+), NO(3) (-) and O(2)) largely determined the composition of the nirS-type denitrifier communities within the water column of the Gotland Basin.     

Detection of Microcystis in Lake Sediment using Molecular Genetic Techniques

Summary Microcystis, which are toxic microcystin-producing cyanobacteria, normally bloom in summer and drop in numbers during the winter season in Senba Lake, Japan. Recently, this lake has been treated by ultrasonic radiation and jet circulation which were integrated with flushing with river water. This treatment was most likely sufficient for the destruction of cyanobacterial gas vacuoles. In order to confirm whether Microcystis viridis was still present, a molecular genetic monitoring technique on the basis of DNA direct extraction from the sediment was applied. Three primer sets were used for polymerase chain reaction (PCR) based on rRNA intergenic spacer analysis (RISA), the DNA dependent RNA polymerase (rpoC1) and a Microcystis sp.-specific rpoC1 fragment. The results from each primer were demonstrated on the basis of single strand conformation polymorphisms (SSCP). Using the RISA primer showed different results from the rpoC1 and Microcystis sp.-specific rpoC1 fragment; meanwhile, the rpoC1 Microcystis sp.-specific fragment was more specific than the RISA primer. Therefore, the Microcystis sp.-specific rpoC1 fragment was further analysed by denaturing gradient gel electrophoresis (DGGE). The DNA pattern representing M. viridis could not be detected in any of the sediment samples. However, the results were confirmed with another technique, terminal restriction fragment length polymorphisms (T-RFLP). Although T-RFLP patterns of 16S rDNA in sediment at 91 bp and 477 bp lengths were matched with the T-RFLP of M. viridis (HhaI and MspI endonuclease digestion, respectively), the T-RFLP pattern of 75 bp length was not matched with M. viridis (both of HhaI and MspI endonuclease digestion) which were the major T-RFLP pattern of M. viridis. Therefore, the results most likely indicated that M. viridis seems to have disappeared because of the addition of the ultrasonic radiation and jet circulation to the flushing treatment.