Temperature profile of oxygen activation and defense against oxygen toxicity in a psychrophilic member of the Bacteroidaceae

Abstract

The temperature profiles have been determined for O2 reduction by activating substrates for whole cells and cell extracts of the psychrophilic, obligately anaerobic bacterium, strain B6, belonging to the Bacteroidaceae. The profiles were similar whether the cells were grown at 15 or 1°C, and also for cells harvested in the exponential or stationary phase. The H2O producing pyruvate oxidase displayed in cell-free extracts a considerably higher activity than the H2O2 producing NADH and NADPH oxidases at all temperatures in the range 30–1°C, and characteristically makes up a larger proportion of the total O2 reduction capacity the lower the temperature. It thus seems that the O2 scavenging property of the pyruvate oxidase, postulated to be utilized in a defense mechanism against the detrimental effects of the H2O2 producing pyridine nucleotide oxidases, is particularly well adapted to function at the low temperatures of the Barents Sea, from which this obligately anaerobic organism originates.