E. coli mutant NR71 grows on succinate in the absence of an F₁ ATPase

Over 50 years ago, two E. coli ATPase mutants were isolated and characterized. The first, NR70, was later shown to contain a 21-base deletion in the gene for the gamma subunit of the F₁F₀ ATPase, rendering it incapable of growth on the nonfermentable carbon source succinate. The second, NR71, was derived from NR70 by selection for growth on succinate. We show that NR71 contains a stop codon near the middle of the gene for the alpha subunit, making it unable to synthesize a full-length alpha subunit. We further show that we could not detect the alpha, beta, or gamma subunits in membranes isolated from this strain. Strain NR71 can grow on succinate despite the absence of an intact F₁ ATPase and therefore carry out succinate-dependent ATP synthesis by an unknown process.

An E. coli strain lacking an ATPase can nonetheless grow on a non-fermentable carbon source, indicating that this mutant has an unknown mechanism for synthesizing ATP from the oxidation of succinate.