CHLOROFLEXUS-LIKE ORGANISMS FROM MARINE AND HYPERSALINE ENVIRONMENTS - DISTRIBUTION AND DIVERSITY

We report the presence of a diverse number of Chloroflexus-like organi sms in intertidal marine and submerged hypersaline microbial mats usin g light, infrared fluorescence, and electron microscopy. The intertida l organisms appear morphologically very similar to thermophilic C. aur antiacus while the 2 hypersaline strains are larger and have a more co mplex ultrastructure composed of chlorosome-bearing internal membranes that appear to arise as invaginations of the cell membrane. By compar ing spectroradiometry of microbial mat layers with microscopic observa tions, we have confirmed that the Chloroflexus-like organisms are majo r constituents of the hypersaline microbial mat communities. In situ s tudies on mat layers dominated by Chloroflexus-like organisms showed t hat sulfide-dependent photoautotrophic activity sustained by near infr ared radiation prevailed. Autoradiographic analyses revealed that auto trophy was sustained in the filaments by 750 nm radiation. Three morph ologically distinct strains are now maintained in mixed culture. One o f these appears to be growing photoautotrophically.