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Project Progress

Ecogenomics related activities in the Pace laboratory are focused mainly on a molecular analysis of the microbial constituents of hypersaline microbial mats, mainly at Guerrero Negro, Baja California. The goal of these studies is to understand the organismal makeup of these communities and how the individual kinds of organisms contribute to the support of this remarkable concentration of biomass. The results contribute to our knowledge of the diversity of life in extreme environments. Although substantial effort has been invested in the study of chemical aspects of the Guerrero Negro system, relatively little is known about the organisms that comprise these communities.

Most previous studies of the microbial biology of the Guerrero Negro and other hypersaline microbial mats have relied on direct microscopy or on development of cultures of microbes for laboratory studies. However, microscopy detects only morphologically conspicuous organisms, and not many microbes are culturable with standard techniques. Consequently, we are using molecular survey methods in which ribosomal ribonucleic acid (rRNA) genes are obtained directly from natural environmental deoxyribonucleic acid (DNA) by Polymerase Chain reaction and molecular cloning techniques. The studies of Guerrero Negro mats have only begun, but already promise to revolutionize our view of the makeup of such communities. Specifically, previous conclusions based on microscopy and culture have focused on cyanobacterial photosynthesis as the main source of primary productivity (conversion of carbon dioxide into biomass). We find, however, that cyanobacteria, while conspicuously present in these mats, are only one component, and generally a minor component, of the numerically dominant organisms. The generally more abundant organisms (rRNA genes) are representatives of the “Green Nonsulfur” phylogenetic division of bacteria. This was an unexpected result that changes fundamentally the way that the community needs to be modeled. The studies so far have discovered and molecularly described several hundred novel species of microorganisms.