Adaptation for fast growth on glucose by differential expression of central carbon metabolism and gal regulon genes in an Escherichia coli strain lacking the phosphoenolpyruvate:carbohydrate phosphotransferase system.

Phosphoenolpyruvate (PEP) is a key intermediate of cellular metabolism and a precursor of commercially relevant products. In Escherichia coli 50% of the glucose-derived PEP is consumed by the PEP:carbohydrate phosphotransferase system (PTS) for glucose transport. PTS, encoded by the ptsHIcrr operon, was deleted from JM101 to generate strain PB11 (PTS-Glc-). PB12, a mutant derived from PB11, grows faster than the parental strain on glucose (PTS-Glc+ phenotype). This strain can redirect some of the PEP not utilized by PTS into the high yield synthesis of aromatic compounds from glucose. Here, we report a comparative transcription analysis among these strains of more than 100 genes involved in central carbon metabolism during growth on glucose. It was found that in the PTS- strains that have reduced glucose transport capacities, several genes encoding proteins with functions related to carbon transport and metabolism were upregulated. Therefore, it could be inferred that these strains synthesize autoinducers of these genes when sensing very low internal glucose concentrations, probably for scavenging purposes. This condition that is permanently present in the PTS- strains even when growing in high glucose concentrations allowed the simultaneous utilization of glucose and acetate as carbon sources. It was found that the gal operon is upregulated in these strains, as well as the aceBAK, poxB and acs genes among others. In PB12, glk, pgi, the TCA cycle and certain respiratory genes are also upregulated. A mutation in arcB in PB12 is apparently responsible for the upregulation of the TCA cycle and certain respiratory genes.