Abstract
Puroindolines are small, amphipathic, wheat proteins that determine the hardness of the wheat kernel and protect crops from different pathogens. Puroindoline A (PinA) and puroindoline B (PinB) are two major isoforms of puroindolines. These proteins have antibacterial and antifungal properties mainly attributed to their characteristic tryptophan-rich domains (TRDs). In this in vitro study, we investigated the antimicrobial effect of PinA and PinB synthetic peptides against the growth and biofilm formation of Campylobacter jejuni. C. jejuni is an important microaerobic, foodborne pathogen that causes gastrointestinal and neurological diseases in humans. Our results showed that: (1) PinA, but not PinB, has strong antimicrobial activity against C. jejuni clinical strains 81-176 and F38011, Escherichia coli O157:H7, methicillin-resistant Staphylococcus aureus, Salmonella enterica serovar Typhimurium, and Listeria monocytogenes; (2) The substitution of two tryptophan residues to glycine (W→G) in the TRD of PinA abolishes its antimicrobial activity against these microorganisms; (3) PinA functions additively with two common antibiotics (ciprofloxacin and erythromycin) to inhibit or inactivate C. jejuni strains; (4) PinA damages the C. jejuni cellular membrane, (5) PinA is cytotoxic to human INT 407 cells at high concentrations; and (6) PinA inhibits C. jejuni biofilm formation. In summary, this study demonstrates the antimicrobial activity of PinA against C. jejuni growth and biofilm formation and further confirms the potential use of PinA as a therapeutic agent in health care or as preservatives in the agri-food industry.
Highlights
Microorganisms, including commensals and pathogens, have developed antimicrobial resistance to existing drugs (Prestinaci et al, 2015; Nji et al, 2021)
The antimicrobial activity of Puroindoline A (PinA)-linker-puroindoline B (PinB), PinBlinker-PinA, and the combination of PinA and PinB peptides together were tested against C. jejuni strains 81-176 and F38011 (Supplementary Figures 1A,B)
When PinA and PinB peptides were used at a 1:1 concentration, the inhibition was greater than the effect seen with two individual linker peptides
Summary
Microorganisms, including commensals and pathogens, have developed antimicrobial resistance to existing drugs (Prestinaci et al, 2015; Nji et al, 2021). Antimicrobial peptides (AMPs) from natural sources such as plants, insects, and other organisms are considered as potential alternatives to conventional antibiotics due to their broad-spectrum antimicrobial activities and the low chance of microbial resistance development (Tam et al, 2015; Lei et al, 2019). Bacteria are more prone to the effect of AMPs from natural sources than to synthetic drugs, as AMPs often act non- on one or more target(s) that the bacteria cannot restore; e.g., most bacteria are unable to restore the damage to the cell membrane caused by AMPs (Cole and Nizet, 2016). The search for AMPs from natural sources as well as acquiring information on the antimicrobial activities of already known AMPs against a wider range of organisms is crucial to finding suitable natural alternatives to existing drugs
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