ACTION OF CYCLOSERINE ON A SPECIES OF ERWINIA WITH REFERENCE TO CELL DIVISION

D-Cycloserine not only strongly inhibited growth of an Erwinia species, but, at levels allowing some growth, inhibited cell division. The resulting long cells often showed thickening or swelling. Several agents were able to prevent this effect. D-Alanine, at a level that overcame growth inhibition completely, still allowed considerable elongation to take place. To overcome division inhibition completely required an approximately 300-fold higher concentration than that completely overcoming growth inhibition under the conditions used. Similar results were obtained with L-alanine, but at a given concentration it was less effective than D-alanine. Pantoyl lactone partially overcame growth inhibition, and, at higher levels which reduced growth, completely overcame division inhibition. Pyridoxal overcame growth inhibition to a large extent, but increased elongation and damage to cells. Pantoyl lactone and L-alanine showed a high degree of synergism in overcoming both growth and division inhibition by D-cycloserine. Pantoyl lactone plus D-alanine, or pyridoxal plus either D- or L-alanine also showed such a synergism, but to a lesser extent. The significance of these findings with regard to known enzyme inhibitions of D-cycloserine is discussed.

BIOCHEMICAL EFFECTS OF NOVOBIOCIN ON STAPHYLOCOCCUS AUREUS

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.