Dps Protects Enterohemorrhagic Escherichia coli against Acid-Induced Antimicrobial Peptide Killing

Abstract

Dps, a DNA-binding protein from starved cells in Escherichia coli, is part of the bacterial defense system that protects DNA against various cellular stresses. Our lab previously demonstrated that a novel antimicrobial peptide, WRWYCR, enhances acid-induced killing of enterohemorrhagic Escherichia coli (EHEC) and ameliorates infection in a Citrobacter rodentium mouse model of EHEC infection. WRWYCR has previously been shown to compromise DNA damage repair and to increase chelatable iron within the cell. These findings, combined with the effects of peptide and acid stress on DNA damage, suggest a key defense role for Dps in peptide-induced killing of EHEC. The goal of this study is to evaluate the role of Dps in peptide-induced killing of EHEC through survival assays and flow cytometric analyses of DNA damage and hydroxyl radical formation. Our results demonstrate that disruption of the dps gene in stationary-phase EHEC O157:H7 cells, but not in exponential-phase cells, enhances acid-, peptide-, and peptide-acid-induced killing relative to that of wild-type (WT) EHEC. Using flow cytometric analysis, we have also demonstrated increased levels of hydroxyl radicals in peptide-treated wild-type EHEC relative to those in the untreated control. Disruption of the dps gene further increases this. These findings indicate that peptide treatment of EHEC enhances the formation of hydroxyl radicals, likely through the Fenton reaction, thereby contributing to the killing action of the peptide, and that dps protects against peptide killing of EHEC. This study provides important insights into peptide WRWYCR-mediated killing of EHEC, which could be exploited in the development of more effective antimicrobials. IMPORTANCE The research presented in this paper explores the role of the DNA-binding protein Dps as a key defense mechanism of enterohemorrhagic Escherichia coli (EHEC) strains in protecting against killing by the novel antimicrobial peptide WRWYCR. Our results demonstrate that Dps protects against peptide-induced killing of EHEC through direct protection against acid stress and hydroxyl radical formation, both of which are mechanisms targeted by the antimicrobial peptide. This study provides important insights into peptide WRWYCR-mediated killing of EHEC, which could be exploited in the development of more effective antimicrobials through specific targeting of Dps in order to allow a more potent response to the antimicrobial WRWYCR.

Transcriptional analysis reveals specific niche factors and response to environmental stresses of enterohemorrhagic Escherichia coli O157:H7 in bovine digestive contents

“…The catalase KatG and the alkyl hydroperoxide-NADPH oxidoreductase AhpCF are involved in the degradation of endogenous peroxide [49]. Dps can directly bind DNA to form a highly stable complex resistant to acid, base and oxidative stresses, and together with YaaA can sequester intracellular unincorporated iron [50][51][52]. The Suf proteins are also required by E. coli for rebuilding iron-sulfur clusters that have been oxidatively damaged [49,53].…”

DNA-Binding Protein Dps Protects Escherichia coli Cells against Multiple Stresses during Desiccation

“…DNA-binding protein Dps is involved in the protection of bacterial cells from various types of stresses, primarily oxidative and starvation stress, as a result of which the protein copy synthesis increases to 150–200 thousand [ 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ]. It has been shown that it protects bacteria from heat and alkaline shocks, high pressure, toxic effects of heavy metals, UV and gamma radiation, and other types of negative effects [ 13 , 15 , 18 , 23 , 24 , 25 , 26 , 27 , 28 ].…”