Alkalophiles have much higher cytochrome contents than conventional bacteria and than their own non-alkalophilic mutant derivatives

The membranes of two alkalophilic bacilli contain extraordinarily high cytochrome heme contents, at least 5.5 nmoles/mg membrane protein. Membranes from the non-alkalophilic derivatives of these bacterial strains contain much lower heme concentrations, especially lower b- and c-type cytochromes. The respiratory rates of whole cells of the non-alkalophiles were, nevertheless, equal to or slightly greater than those of the alkalophiles at their respective optimal pHs. Moreover, although alkalophiles expend energy to keep their cytoplasmic pH below the external pH, their growth yields on L-malate are comparable to conventional bacteria. Perhaps, among the special bioenergetic properties of alkalophilic bacteria, there are characteristics of the respiratory chain which facilitate particularly efficient energy transduction.