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Oxolinic acid (1-ethyl-1,4-dihydro-6,7-methylenedioxy-4-oxo-3-quinolinecarboxylic acid) is an antimicrobial agent effective against a variety of gram-negative pathogens, including Proteus . With the exception of Staphylococcus aureus , oxolinic acid is inactive against gram-positive bacteria and against fungi. Our results suggest that oxolinic acid exerted its primary action on synthesis of deoxyribonucleic acid (DNA). The rate of thymidine- 2 - 14 C incorporation into DNA was significantly depressed in the presence of 0.1 μg of oxolinic acid per ml and was markedly inhibited at 1 μg/ml. No evidence of complexing with DNA was observed. Pulse labeling with radioactive precursors revealed that at levels approximating the minimal inhibitory concentration, oxolinic acid had no effect on rate of incorporation of 14 C-valine into protein, uracil- 2 - 14 C into ribonucleic acid, or sodium acetate- 1 - 14 C into lipid. Filamentous forms of P. vulgaris ATCC 881 were observed after in vitro exposure to subinhibitory levels of oxolinic acid. Concentrations of oxolinic acid in excess of the minimal inhibitory concentration (0.39 μg/ml) did not cause lysis of cells of P. vulgaris or leakage of cytoplasmic materials. Mg ++ ions diminished the in vitro activity of oxolinic acid, possibly through formation of Mg ++ chelates

Kronish, Donald P. (Warner-Lambert Research Institute, Morris Plains, N.J.), Raam R. Mohan, and Benjamin S. Schwartz . Distribution of radioactivity in autolyzed cell wall of Bacillus cereus during spheroplast formation. J. Bacteriol. 87: 581–587. 1964.—Spheroplasts of Bacillus cereus strain T were produced from cells grown in the presence of uniformly labeled C 14 -glucose. At regular intervals during spheroplast formation, enzymatically degraded cell wall was isolated by a new procedure. Radioactivity of solubilized cell wall in cell-free material increased from 2.5 to 42% of the total incorporated label during spheroplast formation. The rate of cell-wall degradation as measured by increase in radioactivity was biphasic with relative slopes of 2.0 and 5.0. During autolytic depolymerization of B. cereus cell wall, two major components were solubilized at different rates. Chemical fractionation revealed these to be a peptide and a mucopeptide. The possibility of two enzymes being involved in spheroplast formation and cell-wall degradation is discussed.