Cold 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.
