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要旨:
Two new strains of marine purple bacteria, N1(T) and N2(T), were isolated from coastal sediment of the North Sea (Germany) with ferrous iron as the only electron donor for anoxygenic photosynthesis. The isolates are the first salt-dependent, ferrous-iron-oxidizing purple bacteria characterized so far. Analysis of 16S rRNA gene sequences revealed an affiliation with the genus Rhodovulum, which until now comprises only marine species. the sequence similarity of both strains was 95.2%, and their closest relative was Rhodovulum adriaticum, Like all known Rhodovulum species, the new strains had ovoid to rod-shaped cells, contained bacteriochlorophyll a and carotenoids of the spheroidene series, and were able to oxidize sulfide and thiosulfate. Like Rhodovulum adriaticum, both strains were unable to assimilate sulfate; for growth they needed a reduced sulfur source, e.g. thiosulfate. In contrast to the new strains, none of the known Rhodovulum species tested was able to oxidize ferrous iron or iron sulfide. In growth experiments, strains N1(T) and N2(T) oxidized 65 and 95%, respectively, of the ferrous iron supplied. Electron diffraction analysis revealed ferrihydrite as the main product of ferrous iron oxidation. In addition, traces of magnetite were formed. Strains N1(T) (= DSM 12328(T)) and N2(T)(= DSM 12329(T)) are described as Rhodovulum iodosum sp. nov, and Rhodovulum robiginosum sp, nov., respectively.
