The Effect of Antibiotics on Synthesis of Mucopeptide and Teichoic Acid by Pediococcus cerevisiae and by a Substrain that Requires Methicillin for Growth

SUMMARY Mucopeptide synthesis by Pediococcus cerevisiae ATCC 808 I and P. cerevisiae CRD (a methicillin-requiring substrain) was measured by incorporation of radioactivity from l4C-label1ed-alanine, -glutamate, -1ysine and -aspartate into the muco- peptide fraction of organisms incubated in a solution inadequate to support growth. Teichoic acid synthesis was measured by incorporation of (32P)H3P04 into a hot trichloroacetic acid soluble fraction from isolated walls. Mucopeptide synthesis by both strains (as measured by incorporation of ( ~-~*C)glutamic acid) was unaffected by chloramphenicol but was sensitive to benzylpenicillin. The incorporation was resistant to methicillin in strain CRD (2 mg/ml gave 50 % inhibition) but not in parent organisms (120 pg/ml gave 50 % inhibition). Strain CRD incorporated twenty times less (32P)H3P04 into teichoic acid than did the parent strain. With either strain, benzylpenicillin (25 pg/ml) and D-CyClO- serine (200 ,ug/ml) inhibited this synthesis, but methicillin (500 and 1000 pg/ml) did not. Electron micrographs of strain CRD incubated for four hours with methicillin showed large deposits of wall material around septa; these were not seen in parent organisms.