THE CYTOCHROME COMPOSITION OF THE MEAT SPOILAGE BACTERIUM BROCHOTHRIX-THERMOSPHACTA - IDENTIFICATION OF CYTOCHROME A3-TYPE AND D-TYPE TERMINAL OXIDASES UNDER VARIOUS CONDITIONS

Brochothrix thermosphacta, grown in batch culture in a yeast-dextrose broth, at temperatures from 30-degrees-C to 10-degrees-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-degrees-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-degrees-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.