Abstract
Colistin was observed to bind to eell wall preparations of colistin-producing Bacillus colistinus 11-4. The binding occurred at 0 and 30°C, and was much suppressed by divalent cations (Mg2+ and Ca2+), acidic pH and the cationic detergent, cetylpyridinium chloride, but not by the neutral detergent, Triton X-100. When the carboxyl groups in the cell wall preparations were chemically modified to neutralize their electrochemical charges through the formation of glycine ethyl ester, the modified wall showed extremely decreased binding capacity for colistin. The molar ratio of charged carboxyl groups in the wall and maximum binding to colistin was calculated to be 1:0.25. A large excess of the wall preparation protected the protoplasts of colistin-producing organisms from the action of colistin, but the modified wall did not.
