Metagenomic studies of the diversity and function of chemosynthetic microbial communities at oceanic spreading zones

了解洛加切夫喷口等热液地点的生物和非生物因素的相互作用，对于了解大洋中部扩张轴处的微生物群落以及从地幔向海洋的能量和物质转移具有重要意义。为此，提出了一种新发展起来的分子生物学方法--元基因组学。元基因组被定义为在一个确定的位置，例如，从特定的喷口或渗漏释放的流体中发现的基因组的总和。将与地质学家、流体地球化学家和微生物学家合作，选择具有特色的采样点。将收集生物质并提取高相对分子质量的环境DNA。将产生包含约40kb插入片段的大型融合体库，并筛选系统发育标记16SRRNA和参与a)二氧化碳和氮气固定以及b)海洋微生物化学合成的两种最常见底物甲烷和硫化物转化的功能基因。这些研究将首次深入了解采样点主要微生物群落成员的基因组设备、他们的代谢和生化潜力以及他们的进化。这些结果将与培养和基于PCR的序列检索获得的数据进行比较，并与流体化学和物理学相关联。将检索有关生物地球化学反应的微生物催化的详细信息。

Understanding the interaction of biotic and abiotic factors at hydrothermal locations such as the Logatchev vent area is of fundamental importance for understanding of microbial communities at the mid-oceanic spreading axes and the transfer of energy and material from the mantle to the ocean. Thereforea recently developed molecular biological approach, metagenomics, is proposed. The metagenome is defined as the sum of genomes found in a defined site, e.g., in the fluid released from a particular vent or seep. In collaboration with geologists, fluid geochemists, and microbiologists, charateristic sampling sites will be chosen. Biomass will be collected and high molecular weight environmental DNA will be extracted. Large fosmid libraries containing inserts of approximately 40 kb will be produced and screened for the phylogenetic marker 16S rRNA and for funtional genes involved in a) CO2 and N2 fixation, and b) the transformation of the two most common substrates of marine microbial chemosynthesis, methane and sulfide. The studies will offer first insights into the genomic equipment of the main microbial community members at the sampling sites, their metabolic and biochemical potential, and their evolution. These results will be compard to data obtained by cultivation and PCR-based sequence retrieval, and correlated to fluid chemistry and physics. Detailed information on the microbial catalysis of relevant biogeochemical reactions will be retrieved.