alpha proteobacterium SCGC AAA280-P20 Genome sequencing and assembly. alpha proteobacterium SCGC AAA280-P20

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.

湖泊及其他淡水生态系统在全球碳循环及相关元素循环中发挥着至关重要的作用，同时可为人类社会提供生活用水与工业技术用水。栖息于这些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者，但目前我们对单个微生物及微生物类群如何演化、并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不足。为填补这一认知空白，我们计划对两类丰度极高但尚未获得纯培养的淡水细菌类群的单细胞扩增基因组（single-cell amplified genomes, SAGs）进行测序：一类是α-变形菌门（Alphaproteobacteria）LD12类群，其作为SAR11类群的淡水姊妹群而广为人知；另一类是放线菌门（Actinobacteria）ac1进化枝（ac1 clade）。这两类类群均具有全球分布特征，被认为在湖泊生态系统的碳与营养物质通量调控及转化过程中发挥着关键作用，但由于缺乏代表性基因组序列，我们对这些类群的认知仍受到极大限制。通过对ac1进化枝与LD12类群的多个代表性单细胞进行测序（包括从不同地理区域的淡水生态系统中采集的样本），我们将能够重构淡水生态系统中部分最优势物种的代谢特性。此外，我们还可探究LD12类群与ac1进化枝内的基因组分化程度，加深对水生细菌如何响应环境变化而演化的认知。最终，从这两类类群中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（metagenomic analyses）提供至关重要且目前尚缺失的“锚点”。