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.