A marine photosynthetic bacterium (strain SH1) was isolated after enrichment under phototrophic conditions in media containing dimethylsulphide (DMS) and bicarbonate (HCO ) as potential carbon sources. Analysis of culture medium using nuclear magnetic resonance spectrometry showed that during phototrophic and chemotrophic growth of strain SH1 on DMS/HCO dimethylsulphoxide (DMSO) was produced from DMS. These results indicate that strain SH1 grew autotrophically with DMS serving as an electron donor in photosynthesis and respiration, but not as a carbon source. Biochemical characterization and 16S rRNA analysis indicated that the isolate was a strain of An assay for the enzyme catalysing the oxidation of DMS (DMS:acceptor oxidoreductase) was developed by measuring electron transfer from DMS to 2,6-dichlorophenolindophenol (DCPIP). This reaction was dependent on phenazine ethosulphate to mediate electron transfer from DMS:acceptor oxidoreductase to DCPIP. DMS:acceptor oxidoreductase was found to have a periplasmic location in strain SH1 as was a reduced methylviologen: DMSO oxidoreductase activity. Zymogram staining patterns of periplasmic fractions indicated that DMS: acceptor oxidoreductase and DMSO reductase were distinct enzymes. This was confirmed by resolution of the two activities by gel filtration.


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