actinobacterium SCGC AAA027-J17 Genome sequencing and assembly. actinobacterium SCGC AAA027-J17

Lakes and other freshwaters play a crucial role in the global cycling of carbon and associated elements and also provide water for consumption and technical use to society. The microorganisms that inhabit these ecosystems are the key drivers of freshwater biogeochemical processes but our understanding of how individual microbes and microbial groups evolve and contribute to diversity and specific ecosystem functions is incomplete. To help close this knowledge gap we propose sequencing of single-cell amplified genomes (SAGs) from two of the most abundant, yet uncultured, lineages of freshwater bacteria: the Alphaproteobacteria LD12, better known as the freshwater sister group to SAR11, and the Actinobacteria ac1 clade. Both groups are globally distributed and are believed to play major roles in regulating the flux and transformation of carbon and nutrients in lake ecosystems, but the lack of representative genome sequences limits our understanding of these groups. By sequencing multiple representative cells from the ac1 and LD12 clades, including cells collected from geographically separate systems, we can reconstruct the metabolic properties of some of the most successful organisms in freshwater ecosystems. We will also be able us probe the extent of genomic diversification among the LD12 and ac1 groups and increase our understanding of how aquatic bacteria evolve in response to environmental change. Finally, the draft genomes generated from these clades will provide the crucial, but presently missing, ?anchors? for metagenomic analyses of freshwater systems that are currently underway.

湖泊及其他淡水水体在全球碳循环及相关元素循环中发挥关键作用，同时为人类社会提供生活与生产用水。栖息于此类生态系统中的微生物是淡水生物地球化学过程的核心驱动因子，但当前我们对单个微生物及微生物类群的演化机制，以及它们如何推动群落多样性形成与特定生态系统功能实现的认知仍存在缺口。为填补这一认知缺口，本研究拟对两类丰度极高但尚未获得纯培养的淡水细菌谱系开展单细胞扩增基因组（SAGs）测序：一是α-变形菌门（Alphaproteobacteria）LD12类群，其作为淡水生态系统中与SAR11互为姊妹群的类群广为人知；二是放线菌门（Actinobacteria）ac1进化枝。这两类类群均呈全球分布，被认为在湖泊生态系统的碳与营养盐通量调控及转化过程中发挥核心作用，但目前缺乏代表性基因组序列，限制了我们对这些类群的深入理解。通过对ac1与LD12进化枝的多株代表性细胞（包括从不同地理区域的淡水生境中采集的样本细胞）进行测序，我们能够重构淡水生态系统中部分优势类群的代谢特性。此外，本研究还可探究LD12与ac1类群间的基因组分化程度，并加深我们对水生细菌如何响应环境变化而演化的认知。最终，从这两类进化枝获得的草图基因组，将为当前正在开展的淡水生态系统宏基因组分析提供此前缺失的关键“锚点”。