Dimethyl sulfoxide reductase activity by anaerobically grown Escherichia coli HB101

Abstract

E. coli grew anaerobically on a minimal medium with glycerol as the Ca and energy source and dimethyl sulfoxide (DMSO) as the terminal electron acceptor. DMSO reductase activity, measured with an artificial electron donor (reduced benzyl viologen), was preferentially associated with the membrane fraction (77 .+-. 10% total cellular activity). A Km for DMSO reduction of 170 .+-. 60 .mu.M was determined for the membrane-bound activity. Methyl viologen, FMNH2 and FADH2 also served as electron donors for DMSO reduction. Methionine sulfoxide, a DMSO analog, could substitute for DMSO in both the growth medium and in the benzyl viologen assay. DMSO reductase activity was present in cells grown anaerobically on DMSO but was repressed by the presence of nitrate or by aerobic growth. Anaerobic growth on DMSO coinduced nitrate, fumarate, and trimethylamine N-oxide reductase activities. The requirement of Mo cofactor for DMSO reduction was suggested by the inhibition of growth and a 60% reduction activity in the presence of 10 mM sodium tungstate. Chlorate-resistant mutants chlA, chlB, and chlE, and chlG were unable to grow anaerobically on DMSO. DMSO reduction appears to be under the contorl of the fnr gene.