Diversity, Vertical Distribution, and Metabolic Activities of Inorganic Sulfur-Cycling Prokaryotes in Lake Fryxell, Antarctica

寒冷环境占地球生物圈的90%以上，但对嗜冷(嗜冷)微生物的多样性、生理学、系统发育和代谢活动知之甚少。这项研究的重点是硫磺中涉及的细菌。这项研究是在弗莱克塞尔湖进行的，这是一个在水柱中含有大量硫化物的混交湖。这项研究将采取多阶段方法，包括现场生物多样性研究、分离和实验室培养，以及代谢活动的分子分析。这些目标中的每一个都将使用传统研究策略和新的实验技术相结合来实现，主要目标是剖析弗莱克塞尔湖在0摄氏度发生的硫循环的微生物学和微生态。工作重点将放在变形杆菌上，生物多样性研究将使用代谢基因而不是核糖体RNA基因作为分子目标。靶基因包括pufM、csoS1和DSR。分离和培养每个主要硫循环原核生物群体的关键代表将使用一系列方法，包括灭绝稀释法、高通量微滴定板和古生物靶标富集法。现场代谢活性的分子测量将与这些生物多样性和实验室培养结果相结合。总的来说，拟议的研究成果将：(1)首次揭示在永久低温下活跃在重要营养循环中的硫循环原核生物的生物多样性；(2)为基础研究和生物技术开发提供嗜冷光养生物、硫化学营养生物和硫酸盐还原细菌等新的遗传资源；(3)揭示弗莱克塞尔湖最具生态意义的硫循环原核生物，并确定有待培养的代谢重要生物。除了促进对微生物硫循环的了解外，拟议的研究结果将对认识和培养地球以外的微生物生命的努力产生积极影响，并应揭示地球上微生物硫循环发生的低温限制。

Cold environments comprise more than ninety percent of the earth's biosphere yet relatively little is known about the diversity, physiology, phylogeny, and metabolic activities of cold-loving (psychrophilic) microorganisms. This research focuses on bacteria involved in the sulfur. The study is Lake Fryxell, a meromictic lake that contains significant levels of sulfide in the water column. The research will take a polyphasic approach that includes in situ biodiversity studies, isolation and laboratory culture, and molecular analysis of metabolic activity. Each of these objectives will be pursued using a combination of traditional research strategies coupled with novel experimental techniques, the prime objective being to dissect the microbiology and microbial ecology of sulfur-cycling that occurs at 0 degree C in Lake Fryxell. Work will focus on Proteobacteria with the biodiversity studies using metabolic genes rather than ribosomal RNA genes as molecular targets. Targeted genes include pufM, csoS1, and dsr. Isolation and culture of key representatives of each major group of sulfur-cycling prokaryotes will be pursued using a combination of methods, including extincting dilution, high-throughput microtiter plate, and archaeal-targeted enrichments. Molecular measurements of metabolic activity in situ will be combined with these biodiversity and laboratory culture results. Collectively, the results of the proposed research will: (1) reveal for the first time the biodiversity of sulfur-cycling prokaryotes active in an important nutrient cycle at permanently cold temperatures; (2) make available new genetic resources of psychrophilic phototrophs, sulfur chemolithotrophs, and sulfate-reducing bacteria for basic research and for biotechnological exploitation; and (3) reveal the most ecologically significant sulfur-cycling prokaryotes in Lake Fryxell and identify metabolically important organisms that remain to be cultured. In addition to advancing an understanding of the microbial sulfur cycle, the results of the proposed research will positively impact efforts to recognize and culture microbial life outside planet Earth, and should reveal the limits, in terms of low temperature, to which microbial sulfur-cycling can occur on Earth.