Two unrelated alkaliphilic Bacillus species possess identical deviations in sequence from those of other prokaryotes in regions of F0 proposed to be involved in proton translocation through the ATP synthase.

The a and c subunits of two unrelated alkaliphilic Bacillus species contain unusual motifs in regions previously implicated by others in H(+)-coupled oxidative phosphorylation. The facultative alkaliphile B. firmus OF4 apparently does not contain genes encoding an alternative F0, supporting other evidence that a single species of proton-translocating F1F0-ATPase catalyses oxidative phosphorylation both at low and high pH. The unusual F0 sequence motifs may be part of the adaptation of the extreme alkaliphiles to growth at very high pH.