Rhodocyclus purpureus gen. nov. and sp. nov., a Ring-Shaped, Vitamin B12-Requiring Member of the Family Rhodospirillaceae

Abstract

The dominant phototrophic bacterium in a water sample from a purplish red waste-water lagoon was isolated in pure culture. The individual cells of this organism were half-ring-shaped and ring-shaped before cell division; the half-rings were 0.6 to 0.7 μm wide and 2.5 to 3.0 μm long. Open or compact coils of variable length were also formed. Acetate, pyruvate, and cyclohexane carboxylate were the carbon sources best utilized by this organism; vitamin B12, p-aminobenzoic acid, and biotin were required as growth factors. The photosynthetic pigments produced by the organism are bacteriochlorophyll αp and carotenoids of the rhodopinal series. The new bacterium was facultatively aerobic and was unable to photooxidize sulfide or thiosulfate to sulfur or sulfate. It belongs to the family Rhodospirillaceae and is described herein as a member of a new genus, Rhodocyclus. The name proposed for this new species is Rhodocyclus purpureus. The type strain of R. purpureus is “Ames” 6770 (= DSM 168).