The cytochrome composition of the meat spoilage bacterium Brochothrix thermosphacta: identification of cytochrome a 3- and d-type terminal oxidases under various conditions

Brochothrix thermosphacta, grown in batch culture in a yeast-dextrose broth, at temperatures from 30 °C to 10 °C, contained diverse membrane-bound respiratory cytochromes. Under conditions of moderate aeration, cytochromes of the a-, b- and d-type were detected at all growth temperatures, but the proportions changed as a function of temperature, with the spectra of cells grown at 10 or 15 °C being dominated by a-type cytochrome(s). Cytochrome a₃ was detected by its reactions with CO and cyanide in cells from all growth conditions. An additional cytochrome a, which was not cyanide-reactive, was also detected, suggesting the presence of an aa₃ oxidase complex. Cytochrome d was cyanide- and CO-reactive, but not detectable in photodissociation spectra, presumably because of the very rapid recombination of CO at the sub-zero temperatures used. Decreasing the oxygen transfer rates to batch cultures resulted in enhanced expression of cytochrome d and changed the proportion of the aa₃-type oxidase that could be attributed to ligand-binding cytochrome a₃; at the lowest oxygen transfer rates, no cytochrome a was detected, suggesting the presence of a cytochrome ba₃ terminal oxidase complex. Intact cells showed no evidence of a c-type cytochrome and no haem C was detected in membrane preparations. After growth at 10°C, the cytochrome composition of B. campestris was essentially identical to that of B. thermosphacta. The multiplicity of putative terminal oxidases in B. thermosphacta is discussed.