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Inhibition of d-alanine carboxypeptidase in Bacillus subtilis by 95% caused no measurable change in the degree of cross-linking of the peptidoglycan.

Wishnow, Rodney M. (Washington University School of Medicine, St. Louis, Mo.), Jack L. Strominger, Claire H. Birge, and Robert H. Threnn. Biochemical effects of novobiocin on Staphylococcus aureus. J. Bacteriol. 89:1117-1123. 1965.-Novobiocin induced accumulation in Staphylococcus aureus of uridine nucleotide precursors of the cell-wall glycopeptide, of a cytidine nucleotide precursor of the teichoic acid in the cell wall, and of a large number of other ultraviolet-absorbing materials. These substances accumulated promptly on addition of the antibiotic at levels near the growth-inhibitory concentration. Isotopic experiments showed that, in addition to inhibiting cell-wall synthesis, novobiocin also inhibited both protein and nucleic acid synthesis. The lack of selectivity in the action of novobiocin is similar to that previously observed with gentian violet, and is quite different from the selective inhibition of cell-wall synthesis observed with penicillin or with d-cycloserine. Although inhibition of cell-wall synthesis is not excluded as one of the primary lethal effects of novobiocin, it is also possible that all of the observed phenomena are secondary to some other primary metabolic lesion.

The staphylolytic enzyme recently isolated from cultures of a Chalaropsis species by Hash is shown to be an acetylmurainidase that cleaves all the glycosidic linkages of N-acetylmuramic acid and N,O-diacetylmuramic acid in the cell wall of Staphylococcus aureus strain Copenhagen. It is similar in specificity to the "32 enzyme" from Streptomyces albus but it differs from egg-white lysozyme whose activity is inhibited by the presence of O-acetyl groups.

Cell walls of Arthrobacter crystallopoietes grown as spheres and as rods were solubilized by treatment with the B enzyme from Chalaropsis, an N-acetylmuramidase. The neutral glycopeptides were then isolated by chromatography on ECTEOLA cellulose. The glycopeptides, consisting of disaccharide-peptide units interlinked by peptide cross-bridges, were fractionated by gel filtration on Sephadex columns into oligomers of various sizes. The size distribution ranged from monomers with no cross-bridges to polymers with a high degree of polymerization, but did not differ significantly between cell walls from cells grown as spheres or rods. Some small differences in the distribution of C- and N-terminal amino acids were found. Analyses revealed that all the peptide bridges in the glycopeptide fractions from rod cell walls were formed by one l-alanine residue. In sphere cell walls, l-alanine was also found, but, in addition, higher oligomers of the glycopeptide contained glycine in their cross-bridges. These results were confirmed by determinations of C- and N-terminal amino acids released after lysostaphin and AL-1 enzyme digestions and by Edman degradations. Models representing the structures of the sphere and rod cell walls are presented. These structures indicate that the sphere cell wall is probably a more loosely knit macromolecule than is the rod cell wall.

Evidence is presented for the appearance of muramic lactam during the late stages of sporulation at about the same time dipicolinic acid synthesis occurs.

Antisera, prepared against formalin-killed cells of Staphylococcus aureus, strain Copenhagen, agglutinated the cell walls of this strain. The agglutination was inhibited by the teichoic acid from the cell wall of this strain, by any degradation product of this teichoic acid which contained the alpha-acetylglucosaminyl-ribitol unit, by alpha-phenyl-acetylglucosaminide, and by N-acetylglucosamine, but not by a large number of other haptens related to the cell wall. In quantitative experiments, however, only 40 to 50 per cent of antibody adsorption to cell wall could be inhibited by teichoic acid or by N-acetylglucosamine. The alpha-acetylglucosaminyl-ribitol unit in the teichoic acid is, therefore, an important immunological determinant in the cell wall of this strain, although other immunological specificities may also exist. The cell walls were also agglutinated by heterologous antisera prepared against streptococcal Group A carbohydrate or against horse serum azophenyl-beta-acetylglucosaminide. The heterologous agglutination, however, was specific for the beta-acetylglucosaminyl-ribitol units in the teichoic acid.

Cell walls of Arthrobacter crystallopoietes were prepared from cells grown as spheres and from peptone- and succinate-induced rod stage cells. Undegraded polysaccharide backbones of the peptidoglycans were isolated from myxobacter AL-1 protease digests by ECTEOLA cellulose and Sephadex G-50 chromatography. The polysaccharide backbones of the sphere cell wall peptidoglycan are heterogeneous in their size, and average less than 40 hexosamines per chain. Those of the rod cell walls are homogeneous in size and average 114 to 135 hexosamines per chain.