Bacillus subtilis F0F1 ATPase: DNA sequence of the atp operon and characterization of atp mutants

Abstract

We cloned and sequenced an operon of nine genes coding for the subunits of the Bacillus subtilis F0F1 ATP synthase. The arrangement of these genes in the operon is identical to that of the atp operon from Escherichia coli and from three other Bacillus species. The deduced amino acid sequences of the nine subunits are very similar to their counterparts from other organisms. We constructed two B. subtilis strains from which different parts of the atp operon were deleted. These B. subtilis atp mutants were unable to grow with succinate as the sole carbon and energy source. ATP was synthesized in these strains only by substrate-level phosphorylation. The two mutants had a decreased growth yield (43 and 56% of the wild-type level) and a decreased growth rate (61 and 66% of the wild-type level), correlating with a twofold decrease of the intracellular ATP/ADP ratio. In the absence of oxidative phosphorylation, B. subtilis increased ATP synthesis through substrate-level phosphorylation, as shown by the twofold increase of by-product formation (mainly acetate). The increased turnover of glycolysis in the mutant strain presumably led to increased synthesis of NADH, which would account for the observed stimulation of the respiration rate associated with an increase in the expression of genes coding for respiratory enzymes. It therefore appears that B. subtilis and E. coli respond in similar ways to the absence of oxidative phosphorylation.