STAPHYLOCOCCUS-HAEMOLYTICUS CONTAINS 2 D-GLUTAMIC ACID BIOSYNTHETIC ACTIVITIES, A GLUTAMATE RACEMASE AND A D-AMINO-ACID TRANSAMINASE

Two D-glutamic acid biosynthetic activities, glutamate racemase and D- amino acid transaminase, have been described previously for bacteria. To date, no bacterial species has been reported to possess both activi ties. Genetic complementation studies using Escherichia coli WM335, a D-glutamic acid auxotroph, and cloned chromosomal DNA fragments from S taphylococcus haemolyticus revealed two distinct DNA fragments contain ing open reading frames which, when present, allowed growth on medium without exogenous D-glutamic acid. Amino acid sequences of the two ope n reading frames derived from the DNA nucleotide sequences indicated e xtensive identity with the amino acid sequence of Pediococcus pentosac eous glutamate racemase in one ease and with that of the D-amino acid transaminase of Bacillus spp. in the second case. Enzymatic assays of lysates of E. coli WM335 strains containing either the cloned staphylo coccal racemase or transaminase verified the identities of these activ ities. Subsequent DNA hybridization experiments indicated that Staphyl ococcus aureus, in addition to S. haemolyticus, contained homologous c hromosomal DNA for each of these genes. These data suggest that S. hae molyticus, and probably S. aureus, contains genes for two D-glutamic a cid biosynthetic activities, a glutamate racemase (dga gene) and a D-a mino acid transaminase (dat gene).