Mutant Strains of Aerobacter aerogenes which Require both Methionine and Lysine for Aerobic Growth

Abstract

SUMMARY Two types of mutants of Aerobacter aerogenes were obtained which grow anaerobically in a minimal medium with glucose as sole carbon source, but which require either succinate or methionine + lysine for aerobic growth in this medium. Only one type of mutant grew in minimal medium with succinate as sole carbon source. This type accumulated pyruvate and α-oxoglutarate during growth in minimal medium with glucose and succinate. It is apparently blocked in the oxidation of α-oxoacids. The other type of mutants accumulated only α-oxoglutarate during growth in minimal medium with glucose and succinate. Cell-free extracts of this type of mutant did not contain α-oxoglutarate dehydrogenase and washed organisms were unable to oxidize acetate. The aerobic molar growth yield of the mutant in minimal medium with glucose, methionine and lysine was much smaller than that of the wild type. Anaerobic growth of these mutants was strongly inhibited by nitrate; this inhibition was prevented by the addition of succinate.