SUMMARY: Megacin however highly bactericidal for sensitive organisms was not adsorbed by them. Its bactericidal action was markedly dependent on temperature. The viability of organisms exposed to megacin at 0° was not affected. When megacin was added to exponentially growing there was cessation of growth followed by a gradual decrease in turbidity of the culture. The decrease in turbidity was, however, not associated with a total lysis of individual organisms; rather it. was the consequence of the escape of the dense intracellular material from the organisms. Intracellular components, i.e. substances which absorbed in the ultraviolet region escaped from the bacteria into the medium while cell wall remained essentially intact. When suspended in a medium containing lactose was exposed to megacin, β-galactosidase appeared on the surface of bacteria.

Protoplast preparations made from and (both sensitive to megacin) were converted into ghost-like structures on the addition of megacin. On the other hand, protoplasts made from insensitive species resisted megacin. Observations indicate that megacin causes a radical change in the osmotic barrier of sensitive organisms by attacking the cytoplasmic membrane. Data available suggest that megacin is either an enzyme which breaks down the osmotic barrier of sensitive cells, or is a substance capable of activating the intrinsic enzymes of cells which lead to an autolysis of cytoplasm.


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