A novel antibacterial peptide derived from Crocodylus siamensis hemoglobin hydrolysate induces membrane permeabilisation causing iron dysregulation, oxidative stress and bacterial death.

A novel antibacterial peptide derived from Crocodylus siamensis hemoglobin hydrolysate induces membrane permeabilisation causing iron dysregulation, oxidative stress and bacterial death.

J Appl Microbiol. 2017 Jul 16;:

Authors: Lueangsakulthai J, Jangpromma N, Temsiripong T, McKendrick JE, Khunkitti W, Maddocks SE, Klaynongsruang S

Abstract
AIMS: A novel antibacterial peptide from Crocodylus siamensis hemoglobin hydrolysate (CHHs) was characterised for antimicrobial activity.
METHODS AND RESULTS: CHHs was hydrolysed for 2 h (2h-CHH), 4 h (4h-CHH), 6 h (6h-CHH) and 8 h (8h-CHH). 8h-CHH showed antibacterial activity against Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae and Pseudomonas aeruginosa at concentrations of 20, 20, 20 and 10 mg ml(-1) (w/v), respectively. Fluorescent microscopy revealed that 8h-CHH had bactericidal activity against E. coli and P. aeruginosa. β-galactosidase assay supported by RT-qPCR demonstrated that 8h-CHH resulted in differential expression of genes involved in iron homeostasis (ftnA and bfd) and oxidative stress (sodA, soxR and oxyR). Siderophore assay indicated that 8h-CHH also impaired siderophore production with diminished expression of pvdF. This pattern of gene expression suggests that 8h-CHH triggers the release of free ferric ions in the cytoplasm. However, decreased expression of genes associated with the SOS response (recA and lexA) in combination with neutral comet revealed that no DNA damage was caused by 8h-CHH. Membrane permeabilisation assay indicated that 8h-CHH caused membrane leakage thought to mediate the antibacterial and iron-stress responses observed, due to loss of regulated iron transport. The novel active peptide from 8h-CHH was determined as QAIIHNEKVQAHGKKVL (QL17), with 41% hydrophobicity and +2 net charge.
CONCLUSIONS: The QAIIHNEKVQAHGKKVL fragment of Crocodylus siamensis hemoglobin is antibacterial via a mechanism that likely relies on iron dysregulation and oxidative stress which results in bacterial death.
SIGNIFICANCE AND IMPACT OF THE STUDY: We have described for the first time, a novel peptide derived from Crocodylus siamensis hemoglobin hydrolysate, that has the potential to be developed as a novel antimicrobial peptide. This article is protected by copyright. All rights reserved.

PMID: 28712131 [PubMed - as supplied by publisher]

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