Characterization of Escherichia coli K12 mutants that can use glycine as sole source of carbon and energy

Mutant strains of Escherichia coli K12 were isolated that are able to use glycine as their sole source of carbon and energy. These were designated GOG. The parent strain of the GOG strains is the pleiotropic mutant KEC9 (ssd) that has high levels of L-serine deaminase and can grow on L-serine as the sole carbon source. Results indicate the GOG strains utilize glycine by way of serine hydroxymethyltransferase, encoded by the glyA gene, and L-serine deaminase. Four GOG strains studied had high levels of serine hydroxymethyl-transferase activity. The selected mutations of three of the GOG strains mapped to the glyA locus; the mutation of the remaining GOG strain mapped roughly to 17 minutes. The GOG strains are unable to grow on glycine as sole carbon source when compounds known to decrease glyA transcription (purines and methionine) are present. Derivatives were selected that overcame this inhibition. Analysis showed that at least some of these strains may be of use for L-serine production.