Mutation of the ptsC gene results in increased production of succinate in fermentation of glucose by Escherichia coli

Escherichia coli NZN111 is blocked in the ability to grow fermentatively on glucose but gave rise spontaneously to a mutant that had this ability. The mutant carries out a balanced fermentation of glucose to give approximatel y 1 mol of succinate, 0.5 mol of acetate, and 0.5 mol of ethanol per mol of glucose. The causative mutation was mapped to the ptsG gene, which encodes the membrane-hound, glucose-specific permease of the phosphotransferase sy stem, protein EIICBglc. Replacement of the chromosomal ptsG gene with an in sertionally inactivated form also restored growth on glucose and resulted i n the same distribution of fermentation products. The physiological charact eristics of the spontaneous and null mutants were consistent with loss of f unction of the ptsG gene product; the mutants possessed greatly reduced glu cose phosphotransferase activity and lacked normal glucose repression. Intr oduction of the null mutant into strains not blocked in the ability to ferm ent glucose also increased succinate production in those strains. This phen omenon was widespread, occurring in different lineages off. coli, including E. coli B.