DELETION OF THE RBO GENE INCREASES THE OXYGEN SENSITIVITY OF THE SULFATE-REDUCING BACTERIUM DESULFOVIBRIO-VULGARIS HILDENBOROUGH

The rbo gene of Desulfovibrio vulgaris Hildenborough encodes rubredoxi n oxidoreductase (Rbo), a 14-kDa iron sulfur protein; forms an operon with the gene for rubredoxin; and is preceded by the gene for the oxyg en-sensing protein DcrA, We have deleted the rbo gene from D. vulgaris with the sacB mutagenesis procedure developed previously (R. Fu and G . Voordouw, Microbiology 143:1815-1826, 1997). The absence of the rbo- gene in the resulting mutant, D, vulgaris L2, was confirmed by PCR and protein blotting with Rbo-specific polyclonal antibodies. D. vulgaris L2 grows like the wild type under anaerobic conditions. Exposure to a ir for 24 h caused a 100-fold drop in CFU of L2 relative to the wild t ype. The lag times of liquid cultures of inocula exposed to air were o n average also greater for L2 than for the wild type. These results de monstrate that Rbo, which is not homologous with superoxide dismutase or catalase, acts as an oxygen defense protein in the anaerobic, sulfa te-reducing bacterium D. vulgaris Hildenborough 1 and likely also in o ther sulfate-reducing bacteria and anaerobic archaea in which it has b een found.