DESULFOBULBUS RHABDOFORMIS SP. NOV., A SULFATE REDUCER FROM A WATER-OIL SEPARATION SYSTEM

A mesophilic, Gram-negative, rod-shaped, marine, propionate-oxidizing sulfate reducer (strain M16(T)) was isolated from a water-oil separati on system on a North Sea oil platform. The optimum conditions for grow th were 31 degrees C, pH 6.8-7.2 and 1.5-2.0%(w/v) NaCl and 0.1-0.3% ( w/v) MgCl2 . 6H(2)O in the medium. The growth yield with sulfate was 4 .6 g cell biomass (mol propionate oxidized)(-1). Strain M16(T) is nutr itionally related to members of the genus Desulfobulbus, but differs i n that it has no vitamin requirement and is able to utilize fumarate a nd malate as carbon and energy sources. Hydrogenase activity measured as hydrogen uptake was mainly membrane-bound and varied with the growt h substrate. Highest activity [28 mu mol min(-1) (mg protein)(-1)] was found in cells grown with hydrogen and lowest [50 nmol min(-1) (mg pr otein)(-1)] in cells grown with propionate as electron donors for sulf ate reduction. Desulforubidin, menaquinone-5(H-2) and cytochromes of t he c- and b-type were present. The fatty acid pattern was similar to t hat found for Desulfobulbus propionicus, The DNA base composition was 50.6 mol% G+C. Strain M16(T) is equidistantly related to D. propionicu s and Desulfobulbus elongatus with 96.1% 16S rDNA similarity. On the b asis of differences in genotypic, phenotypic and immunological charact eristics, strain M16(T) (= DSM 8777(T)) is proposed as the type strain of a new species, Desulfobulbus rhabdoformis.