Colicin M inhibits peptidoglycan biosynthesis by interfering with lipid carrier recycling.

Colicin M is unique among the colicins in that it causes lysis of cells. Synthesis of peptidoglycan was inhibited before colicin-induced cell lysis occurred. This suggested that inhibition of peptidoglycan synthesis was the primary effect of the colicin which was followed by cell lysis. Following colicin M treatment, soluble peptidoglycan nucleotide precursors accumulated, and radioactivity associated with the membrane-bound carrier lipid almost disappeared. Further metabolism of radiolabeled intermediates bound to the lipid carrier (lipid intermediates) was not inhibited by colicin M. The two lipid intermediates decreased to a level where equal amounts of both were present. The data indicated that translocation of nucleotide precursors to the lipid carrier was not inhibited. In vitro peptidoglycan synthesis agreed with the in vivo results. It is concluded that colicin M inhibits peptidoglycan biosynthesis by preventing regeneration of the lipid carrier.