Benzylpenicillin-induced filament formation of Clostridium perfringens

Growth of Clostridium perfringens with low concentrations of benzylpenicillin inhibited septum formation and division of the organisms. This resulted in continued growth of the organisms as aseptate filaments. The effect was reversed on removal of the antibiotic. The composition of walls isolated from organisms grown with the antibiotic was similar to that of walls from untreated bacteria. In addition, both contained non-N-acetylated glucosamine residues in their peptidoglycan. No differences were detected in the degree of cross-linkage of peptidoglycan. Clostridium perfringens contains six membrane-associated penicillin-binding proteins (PBPs) which have different affinities for [3H]benzylpenicillin. Concentrations of the antibiotic which were sufficient to cause filamentation of apparently all organisms in a culture caused almost complete saturation of PBPs 3, 4, 5 and 6. At these concentrations there was no measurable interaction with PBPs 1 and 2. Thus interaction of the antibiotic with the lower molecular weight PBPs is correlated with the inhibition of septum formation in C. perfringens.