Rhodospira trueperi gen. nov., spec. nov., a new phototrophic Proteobacterium of the alpha group

A new phototrophic purple bacterium was isolated from a flat, laminated microbial mat in a salt marsh near Woods Hole, Mass., USA. The spiral-shaped bacterium was highly motile and had bipolar tufts of flagella and intracytoplasmic membranes of the vesicular type. The major photosynthetic pigments were identified as the carotenoid tetrahydrospirilloxanthin and bacteriochlorophyll b. The long wavelength in vivo absorption maximum of the bacteriochlorophyll was at 986 nm. The marine bacterium showed optimal growth in the presence of 2% NaCl. It utilized a number of organic substrates as carbon and energy sources and required vitamins and sulfide as a reduced sulfur source for growth. In the presence of sulfide, elemental sulfur globules were formed outside the cells. Elemental sulfur was not further oxidized to sulfate. The new isolate had a unique lipid and fatty acid composition, and according to the 16S rRNA gene sequence, it is most similar to Rhodospirillum rubrum. It is described as a new species and assigned to a new genus with the proposed name Rhodospira trueperi.