| The research presented focused on the isolation of bacteria from extreme environments and their characterization in terms of phenotype, phylogeny, photosynthetic function and ability to reduce heavy metalloids. Isolates from the meromictic Mahoney Lake and deep ocean hydrothermal vents were examined using classical techniques and several were described taxonomically. The Mahoney Lake strains represented diverse new members of the aerobic phototrophic and the purple non-sulfur bacteria, produced unusual pigment protein complexes and were adapted to the fluctuating levels of pH and salinity in a meromictic lake. The metalloid resistant isolates also tolerated fluctuating conditions, and reduced TeO32- or SeO32- accumulating elemental Te or Se.; Roseicyclus mahoneyensis gen. nov., sp. nov was proposed for ten vibrioid strains of aerobic phototrophic bacteria with an unusual monomodal light harvesting II complex (805-806 nm), and tolerance to high salinity. Four appendaged and budding bacteria were closely related to the genera Erythrobacter and Porphyrobacter. Although 16S rRNA phylogeny could not resolve the relationship between these two genera, the new isolates shared several phenotypic traits with the genus Porphyrobacter and thus were proposed as a new species, P. meromictius. Phylogenetic analysis of metalloid-reducing strains identified them as relatives of Pseudoalteromonas. However they had important differences from previously described species and thus were proposed as P. telluritireducens sp. nov. and P. spiralis sp. nov.; In order to determine the distribution of aerobic anoxygenic phototrophs in the ocean around black smokers the cultivable population was investigated, revealing that C. bathyomarinum can be found at depths of 500 m and below, but not at the surface. The pigment protein complexes of this species were capable of light induced e- transfer and thus C. bathyomarinum is photosynthetically competent and should be able to supplement its energy needs when light is available.; Photosynthetic e- transfer was investigated in P. meromictius, ML31 and R. mahoneyensis, ML6T. Photochemical activity in ML31 was observed aerobically, and the photosynthetic apparatus was not functional under anaerobic conditions. In ML6T low levels of photochemistry were measured anaerobically, however, electron transfer occurred optimally under low oxygen conditions, an interesting and unique case. |
