OXYGEN-CONSUMPTION BY DESULFOVIBRIO STRAINS WITH AND WITHOUT POLYGLUCOSE

The kinetics of oxygen reduction by Desulfovibrio salexigens Mast1 and the role of polyglucose in this activity were examined and compared w ith those of strains of D. desulfuricans and D. gigas. Oxidation rates were highest at air saturation (up to 40 nmol of O-2 min(-1) mg of pr otein(-1)) and declined with decreasing oxygen concentrations, Studies with cell extracts (CE) indicated that NADH oxidase was entirely resp onsible for the oxygen reduction in strain Mast1, In D. desulfuricans CSN, at least three independent systems appeared to reduce oxygen, Two were active at all oxygen concentrations (NADH oxidase and NADPH oxid ase), and one was maximally active at less than 10 mu M oxygen, In con trast to D. gigas and D. salexigens strains, the D. desulfuricans stra ins also contained NADH peroxidase and NADPH peroxidase activities and did not accumulate polyglucose under nonlimiting growth conditions, A t air saturation, initial activities of the oxidases and peroxidases o f cells harvested at the end of the log phase were on the order of 20 to 140 nmol of O-2 min(-1) mg of protein(-1). In all strains, these en zymes were relatively stable but were susceptible to inactivation as s oon as substrates were added to the assay mixture, Under those conditi ons, all oxidation activity disappeared after ca, 1 h of incubation, T he same finding was observed with whole cells of D. desulfuricans CSN and D. desulfuricans ATCC 27774, but inactivation was less pronounced with cells of D. salexigens Mast1, It appeared that the presence of po lyglucose in the whole cells retarded the process of inactivation of N ADH oxidase, but this property was lost in crude CE, In spite of the e ffect of polyglucose on the oxidative potential, oxygen-dependent grow th of D. salexigens Mast1 could be demonstrated neither in batch nor i n continuous culture.