Antimicrobial activity of a 14-residue peptide against Escherichia coli O157:H7

摘要

An amphiphilic, cationic peptide composed of eight leucines and six lysines was synthesized by solid phase peptide synthesis (SPPS). The synthetic peptide was bactericidal within 10 min at concentrations as low as 3 #mu#g ml~(-1) against mid-exponential Escherichia coli O157-H7 suspended in buffer. Concentrations of 25 #mu#g ml~(-1) caused up to 7 log_(10) cfu ml~(-1) reductions. When tested against E. coli O157-H7 grown in TSB, the peptide was bactericidal and bacteriostatic at concentrations of 50 and 25 #mu#g ml~(-1), respectively. An inhibitory effect was also observed against stationary phase cells. The synthetic peptide caused the release of u.v.-absorbing materials from the E. coli O157-H7 as well as an increase in its O.D._(600 nm). Intracellular K~+ and ATP depletion were also observed. These results suggest that the peptide increased the cell membrane permeability but it did not lyse the cells.