The cytological effects of myxin on Escherichia coli

When actively growing cells of Escherichia coli 15T− were treated with the new antibiotic myxin, the effects produced by the antibiotic varied, depending on the concentration. With a concentration of 1 μg/ml, the action was bacteriostatic for the first 60 min exposure. Cell division was inhibited but there was no apparent effect on macromolecular synthesis as evidenced by the formation of filamentous cells. At higher concentrations (3 and 5 μg/ml), myxin was bactericidal although some cell elongation occurred at the 3 μg/ml level. Microscopic examination of cells treated with 3 and 5 μg/ml for 30–45 min indicated the presence of vacuolated areas which thin section studies revealed as intracellular ramifications of the plasma membrane. Protoplasts of cells grown in the presence of 5 μg/ml myxin were enlarged or rapidly lysed even after as little as 15 min exposure. Myxin has no effect on the cell surface of control protoplasts. No abnormal development of the plasma membrane was noted in the elongated cells formed in the presence of 1 μg/ml myxin. Except for the lack of septation during the first 60 min, the filamentous forms appeared normal with well-defined nuclear bodies distributed throughout the cell.