Effects of polyene macrolide antibiotics on normal and protoplast type L-form cells of Escherichia coli W1655F+.

The action of the polyene macrolide antibiotics mycotrienin, pimaricin, lucensomycin, tetramycin, rimocidin, nystatin, filipin, lagosin, pentaene antibiotic 2814P, flavomycoin, flavofungin, hexaene antibiotic 5001P, and candicidin, including perhydro derivatives of them, on wall-less stable protoplast type L-form and normal rod form cells of E. coli W1655F+ was studied. No inhibition of the normal rod form cells was detected. In contrast to these results the growth of the L-form cells was inhibited by all of the substances tested, with the exception of pimaricin. Further experiments have shown that the differences in sensitivity of normal and L-form cells cannot be explained by differences in sterol content, the target site of polyene antibiotics in sensitive eukaryotic cells. According to our results it is obvious that the cell wall of the normal cells functions as a penetration barrier to polyene antibiotics.