Antibacterial activity and mechanism of action of ε-poly-L-lysine.
ε-Poly-L-lysine (ε-PL)(2) is widely used as an antibacterial agent because of its broad antimicrobial spectrum. However, the mechanism of ε-PL against pathogens at the molecular level has not been elucidated. This study investigated the antibacterial activity and mechanism of ε-PL against Escherichia coli O157:H7 CMCC44828. Propidium monoazide-PCR test results indicated that the threshold condition of ε-PL for complete membrane lysis of E. coli O157:H7 was 10 μg/mL (90% mortality for 5 μg/mL). Further verification of the destructive effect of ε-PL on cell structure was performed by atomic force microscopy and transmission electron microscopy. Results showed a positive correlation between reactive oxygen species (ROS)(3) levels and ε-PL concentration in E. coli O157:H7 cells. Moreover, the mortality of E. coli O157:H7 was reduced when antioxidant N-acetylcysteine was added. Results from real-time quantitative PCR (RT-qPCR)(4) indicated that the expression levels of oxidative stress genes sodA and oxyR were up-regulated 4- and 16-fold, respectively, whereas virulence genes eaeA and espA were down-regulated after ε-PL treatment. Expression of DNA damage response (SOS response)(5) regulon genes recA and lexA were also affected by ε-PL. In conclusion, the antibacterial mechanism of ε-PL against E. coli O157:H7 may be attributed to disturbance on membrane integrity, oxidative stress by ROS, and effects on various gene expressions, such as regulation of oxidative stress, SOS response, and changes in virulence.
State Key Laboratory of Food Science and Technology, Nanchang University, Nanchang, PR China.
Ruosong
R
Ye
Hengyi
H
Xu
Cuixiang
C
Wan
Shanshan
S
Peng
Lijun
L
Wang
Hong
H
Xu
Zoraida P
ZP
Aguilar
Yonghua
Y
Xiong
Zheling
Z
Zeng
Hua
H
Wei
D000111:Acetylcysteine / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001386:Azides / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism; D004249:DNA Damage; D004305:Dose-Response Relationship, Drug; D019453:Escherichia coli O157 / Q000187:drug effects* / Q000378:metabolism; D005506:Food Contamination / Q000517:prevention & control; D005516:Food Microbiology; D015964:Gene Expression Regulation, Bacterial; D018625:Microscopy, Atomic Force; D046529:Microscopy, Electron, Transmission; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D011107:Polylysine / Q000494:pharmacology*; D011419:Propidium / Q000031:analogs & derivatives / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism
D000900:Anti-Bacterial Agents; D001386:Azides; D017382:Reactive Oxygen Species; C533957:propidium monoazide; D011107:Polylysine; D011419:Propidium; D000111:Acetylcysteine
Antibacterial mechanism; Escherichia coli O157:H7; Reactive oxygen species; Real-time quantitative PCR; ε-Poly-l-lysine