Survey of Prokaryotic Marine Plankton

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9401110 Fuhrman Although prokaryotes are ubiquitous and immensely important in numerous biological processes, the diversity of naturally occurring marine populations is poorly known. The reasons for this include a general lack of recognizable morphological differences, difficulties in culturability required for standard identification, and questions about proper classification. This proposed renewal project will survey planktonic prokaryotes in diverse U.S. and remote ocean locations, classifying them by means of 16S rRNA gene sequences. This approach has provided a valuable and extremely broad phylogenetic framework of classification, and is the only one at this time that can be done without culturing the organisms. The results are in the form of readily distributed sequence data, and interpretation within the context of a large existing database is via phylogenetic analysis computer programs. Previous work (in our lab and others) has successfully applied this approach to about 15 marine samples, and major new taxa have already been discovered (e.g. 3 major groups of archaebacteria, a few potentially phylum or class level eubacterial groups). The novel archaebacteria dominate the deep-sea clones from the 4 deep Atlantic and Pacific samples examined so far, and may be the most abundant group of organisms on Earth. Results suggest that it is highly likely that other novel major taxa, as well as additional members of better-characterized ones, are awaiting discovery in regions not yet studied. This proposal is to extend the global coverage of these studies to surface and deep waters of South Australia (SE Indian Ocean), the Greenland Sea, the North Polar Ocean, the Northwestern Pacific and Western Tropical Pacific (coral reef), the Arabian Sean (NW Indian Ocean), the Antarctic, and Gulf of Mexico, all remote from locations that have previously been examined by such approaches. Cost-effective remote sampling will be done by colleagues already studying these areas for their own work. Also proposed is repeated sampling from different seasons in California coastal waters, to cover temporal shifts in local microbial composition. The results can be used in tests of hypotheses in ecology, biogeography, and phylogeny, but primarily will serve as framework for future such studies.