The objectives of this project are: (1) to understand the ecology of anoxygenic phototrophs in microbial mats and in particular, the causes of the sequence of layers of anoxygenic phototrophic bacteria in complex multi-layered microbial mat communities; (2) to isolate and characterize the ubiquitous filamentous phototroph, Chloroflexus, from intertidal and hypersaline mats; (3) to isolate and characterize the previously undescribed filimentous bacteriochlorophyll a - containing phototrophs from translucent thermal mats. These prokaryotic communities found in extreme environments are modern analogs of extensive stromatolitic communities that dominated the biosphere during the Precambrian. An understanding of the physiology and ecology of the phototrophs comprising these modern mat communities gives us insight into the nature of the environmental conditions and the microorganisms that comprised the ancient mats that existed on earth from 0.5 to 3.5 billion years ago. These objectives will be met by conducting field studies on thermal and intertidal mats where multi-layered communities exist. The effects of oxygen, sulfide, and light on layering sequences will be determined by comparing oxygen, sulfide, and light microprofiles in adjacent mats that exhibit different layering sequences. Direct isolation, gradient culture, and selective enrichment techniques will be used to isolate the marine Chloroflexus and undescribed thermophilic filamentous phototroph. Characterization of these isolates will be done to determine their relationship to known strains and their significance as descendents of ancient stromatolite-forming phototrophs.
