This project will use tools of molecular biology to approach a long-standing biological oceanographic problem. Its major goals are to (a) learn what kinds of bacteria dominate natural planktonic populations, (b) generate a bank of pure cultures of heterotrophic oligotrophs, and (c) determine which, if any, cultures are representative of major components of the natural populations. Until now, most of the naturally-occurring bacteria have not been phylogenetically characterized (or "identified") because they have resisted attempts to culture them, precluding conventional identification. This project will circumvent the problem with state-of-the-art techniques of RNA sequencing, and DNA cloning to characterize microorganisms. Such work can now be done on freshly collected material without culturing the microorganisms. This project will provide for (1) unambiguous identification of the dominant marine bacteria, in a way appropriate for comparing species compositions of both culturable and nonculturable populations, (2) selection of isolates that are most closely related to those dominating "real" marine populations, suitable for lab studies, (3) the development of molecular probes to define population distribu- tions in other locales and thus measure diversity within and between broadly different environments, (4) the possible use of these probes for single-cell hybridization studies for rapid microscopic identification of microorganisms in preserved samples from any marine environment.
