Biodiversity and Biogeochemistry of Antarctic Photosynthetic Bacteria

低温环境（平均温度5摄氏度或更低）占地球生物圈的90%以上，但对适应寒冷的微生物，特别是光合微生物的多样性和生态活动知之甚少。拟议的研究将探索永久寒冷的南极栖息地，以寻找适应寒冷的无氧光合细菌的生物多样性。该研究对生物多样性采取了分阶段的方法，包括南极光合细菌培养物的富集和分离，其主要生理、生化和遗传特征的实验室表征，以及这些生物自然种群进行的生物地球化学反应的原位研究。使用特殊的，非传统的富集方法，易于培养的冷适应光合细菌物种将在纯培养中分离出来。所采用的分离方法不是基于传统的液体富集，而是采用灭绝稀释，以确保获得丰富和稀有的可培养物种。富集方法的变化将用于分离具有特别发达的特殊代谢的冷适应物种，例如自养二氧化碳固定，氮固定和芳香化合物的光分解代谢。将从在不同温度和生长速率测量下建立的一系列富集培养物中获得分离物，并将用于评估在一定温度范围内生长的能力，以确定哪些只是嗜冷（耐寒）或实际上嗜冷（嗜冷）。分离株将通过16s rRNA测序进行系统发育鉴定。实地研究将包括从麦克默多干谷的分层南极湖泊中分离新文化。研究结果将加强对光合作用多样性的认识，为农业和生物技术应用以及低温下光合作用和相关过程的研究提供新的生物，并扩大已知的嗜冷和嗜冷原核生物的多样性，为外空生物学的研究提供相关模式。

MadiganCold environments (average temperature 5 degrees Celsius or lower) make up greater than 90% of the earth's biosphere, yet relatively little is known about the diversity and ecological activities of cold-adapted microorganisms, in particular, photosynthetic microorganisms. The proposed research will explore permanently cold Antarctic habitats for their biodiversity of cold-adapted anoxygenic photosynthetic bacteria. The research takes a phased approach to biodiversity including the enrichment and isolation of cultures of Antarctic photosynthetic bacteria, laboratory characterization of their major physiological, biochemical, and genetic features, and in situ study of biogeochemical reactions carried out by natural populations of these organisms. Using specific, nontraditional enrichment approaches, readily cultivable species of cold-adapted photosynthetic bacteria will be isolated in pure culture. The isolation methods to be used are not based on classical liquid enrichment but instead employ extincting dilution to ensure that both abundant as well as rare cultivable species are obtained. Variations in the enrichment approach will be used to isolate cold-adapted species with particularly well developed specialized metabolisms, such as autotrophic carbon dioxide fixation, nitrogen fixation and the photocatabolism of aromatic compounds. Isolates will be obtained from a series of enrichment cultures established at different temperatures and growth rate measurements and will be used to assess the ability to grow over a range of temperatures in order to determine which is merely psychrotrophic (cold tolerant) or actually psychrophilic (cold loving). Isolates will be phylogenetically characterized by 16s rRNA sequencing. Field research will include isolation of new cultures from stratified Antarctic lakes in the McMurdo Dry Valleys. The results of the research will strengthen the knowledge of photosynthetic diversity, yield novel organisms for agricultural and biotechnological use and for study of photosynthesis and related processes at low temperatures,and broaden the diversity of known psychrophilic and psychrotrophic prokaryotes, relevant modals for the study of exobiology.