[Effect of antibiotic AL-87 on the growth and ultrastructure of staphylococci]

The effect of antibiotic Al-87 on the ultrastructure of staphylococcal cells was studied. The cells of a control culture of a sensitive strain of S. aureus, 209P at the early exponential growth phase were characterized by thin walls (20-22 nm) and septa (30 nm). In the presence of the subbacteriostatic concentration of antibiotic AL-87 (0.02 microgram/ml) the thickness of the cell walls and septa increased up to 80-90 and 150 nm, respectively. Segregation of the septa was retarded and 4 cell conglomerates formed. The cell division appeared to be highly active: the septa were detected in 80-90 per cent of the sections against 40 per cent in the control. Therefore, antibiotic AL-87 induced significant thickening of the cell walls and impairment of the cell division regulation. Investigation of the staphylococcal variant resistant to the antibiotic showed that there were no significant differences between the cells grown in the absence and presence of antibiotic AL-87 (in a concentration of 200 micrograms/ml). In both the experiments there were detected cells in their majority with thinner walls, L-form-like structures, protoplasts and single conglomerates of the cells with thicker walls and anomalous division and the cells at the moment of lysis. It suggested that the effect of antibiotic AL-87 on the cell wall structure was not direct i. e. by inhibition of protein synthesis but mediated i. e. due to shifts in lipid synthesis inducing changes in lipid-dependent synthesis of the cell wall polymers.