Functional role and ecotype divergence in freshwater ultramicrobacteria

淡水生境中的原核微生物主要参与碳循环过程，但各个微生物种群在各自的代谢和生态特征上存在很大差异。淡水系统的远洋区通常以自由悬浮的超微生物为主。该项目将研究淡水超微生物的三个单系类群（P. necessarius， Ac1分支的放线菌和LD12分支的α变形菌）的功能差异和相似性。它将进一步研究生理和基因典型的不同生态型的分类在每个群体内的特定栖息地。单细胞方法将结合（元）基因组学和转录组学分析，对实验研究中可用的分离物和未培养的超微生物进行分析，并在不同栖息地进行比较原位调查，并评估功能基因（例如细菌视紫红质）的多样性和表达。拟议项目中设想的不同层次的相互作用和共同活动将首次使人们能够对淡水超微细菌的功能作用和系统地理分布模式有一个概貌的看法，否则是无法做到的。它还为欧洲科学家提供了一个机会，通过协调一致地开发和应用新的功能基因组研究工具，在淡水微生物学方面发挥领导作用。

Prokaryotic microorganisms in freshwater habitats are centrally involved in carbon turnover processes, yet individual microbial populations greatly differ in their respective metabolic and ecological features. The pelagic zone of freshwater systems is typically dominated by freely suspended ultramicrobacteria. The proposed project will study the functional differences and similarities of three monophyletic groups of freshwater ultramicrobacteria (P. necessarius, actinobacteria from the Ac1 clade and alphaproteobacteria affiliated with the LD12 lineage). It will furthermore investigate the sorting of physiologically and genotypically distinct ecotypes within each group by their specific habitats. Single-cell approaches will be combined with (meta)genomic and transcriptomic analyses both on available isolates and on uncultured ultramicrobacteria in experimental studies and comparative in situ investigations in different habitats, and the diversity and expression of functional genes (e.g., bacterial rhodopsins) will be assessed. The different levels of interactions and common activities envisaged in the proposed project will for the first time allow a synoptic view of the functional roles and phylogeographic distribution patterns of freshwater ultramicrobacteria that could not be achieved otherwise. It also offers a chance to European scientists to take a leading role in freshwater microbiology through the concerted development and application of novel functional genomic research tools.