Comparative antimicrobial activity and mechanism of action of bovine lactoferricin-derived synthetic peptides |
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Authors: | Yifan Liu Feifei Han Yonggang Xie Yizhen Wang |
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Institution: | (1) National Engineering Laboratory of Biological Feed Safety and Pollution Prevention and Control, The Key Laboratory of Molecular Animal Nutrition of Ministry of Education, The Key Laboratory of Feed and Animal Nutrition of Zhejiang Province, Institute of Feed Science, Zhejiang University, Hangzhou, 310029, People’s Republic of China; |
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Abstract: | Lactoferricin B (LfcinB), a 25 residue peptide derived from the N-terminal of bovine lactoferrin (bLF), causes depolarization
of the cytoplasmic membrane in susceptible bacteria. Its mechanism of action, however, still needs to be elucidated. In the
present study, synthetic LfcinB (without a disulfide bridge) and LfcinB (C–C; with a disulfide bridge) as well as three derivatives
with 15-, 11- and 9-residue peptides were prepared to investigate their antimicrobial nature and mechanisms. The antimicrobial
properties were measured via minimum inhibitory concentration (MIC) determinations, killing kinetics assays and synergy testing,
and hemolytic activities were assessed by hemoglobin release. Finally, the morphology of peptide-treated bacteria was determined
by atomic force microscopy (AFM). We found that there was no difference in MICs between LfcinB and LfcinB (C–C). Among the
derivatives, only LfcinB15 maintained nearly the same level as LfcinB, in the MIC range of 16–128 μg/ml, and the MICs of LfcinB11
(64–256 μg/ml) were 4 times more than LfcinB, while LfcinB9 exhibited the lowest antimicrobial activity. When treated at MIC
for 1 h, many blebs were formed and holes of various sizes appeared on the cell surface, but the cell still maintained its
integrity. This suggested that LfcinB had a major permeability effect on the cytoplasmic membrane of both Gram-positive and
Gram-negative bacteria, which also indicated it may be a possible intracellular target. Among the tested antibiotics, aureomycin
increased the bactericidal activity of LfcinB against E. coli, S. aureus and P. aeruginosa, but neomycin did not have such an effect. We also found that the combination of cecropin A and LfcinB had synergistic effects
against E. coli. |
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