INDUCTION OF BACTERIAL LYSIS BY PENICILLIN

Abstract

Exposure of exponentially growing Escherichia coli in salts-glycerol medium for 20-30 minute to 150 [mu]g/ ml penicillin G caused loss of colony forming ability. A search was made for alterations in the bacteria which under these conditions could result in death. Twenty minutes after addition of penicillin the RNA content of the bacteria decreased, and at 25 minutes syntheses of protein, RNA, DNA, and enzymes stopped. Leakage of large molecules and other indications of permeability changes occurred at 10 minutes. Similar observations were made with Bacillus megaterium. Inhibitors of protein synthesis largely prevented this leakage in E. coli; inhibitors were more effective the earlier they were added. It is supposed that penicillin causes formation of an enzyme which attacks the cell membrane allowing the cell contents escape. Fractions of extracts of penicillin-treated E. coli posses the ability to cause lysis of protoplasts made from B. megaterium; similar fractions of untreated E. coli or from bacteria exposed to penicillin in the presence of 5-methyltryptophan were ineffective. The results are discussed in terms of the mechanism of the action of penicillin.