Abstract
Antimicrobial peptides are a fundamental component of mollusks’ defense systems, though they remain a thinly investigated subject. Here, infection by Vibrio parahemolyticus triggered a significant increase in antimicrobial activity in oyster plasma. By using PBS-challenged oysters as a control, plasma peptides from immunologically challenged oysters were subjected to peptidomic profiling and in silico data mining to identify bioactive peptides. Thirty-five identified plasma peptides were up-regulated post infection, among which, six up-regulated peptides (URPs) showed a relatively high positive charge. URP20 was validated with significant antibacterial activity. Virtually, URP20 triggered aggregation of bacterial cells, accompanied by their membrane permeabilization. Interestingly, URP20 was found to be active against Gram-positive and Gram-negative foodborne pathogens as well as Candida albicans, with no cytotoxicity to mammalian cells and mice. Our study provides the first large-scale plasma peptidomic dataset that identifies novel bioactive peptides in marine mollusks. Further exploration of peptide diversity in marine invertebrates should prove a fruitful pursuit for designing novel AMPs with broad applications.
Highlights
Introduction iationsOverconsumption of antibiotics has led to the rapid emergence and dissemination of antimicrobial resistance in multidrug-resistant pathogens against virtually all classes of existing antimicrobials [1], which threatens to jeopardize the sustainable development of clinical medicine, animal husbandry, aquaculture, and the food industry [2,3]
Oyster plasma contains various soluble factors secreted by hemocytes and other cells, which were separated from the haemolymph and collected for antibacterial activity assays
Plasma was collected after V. parahaemolyticus injection, with PBS injection being set as a control
Summary
Introduction iationsOverconsumption of antibiotics has led to the rapid emergence and dissemination of antimicrobial resistance in multidrug-resistant pathogens against virtually all classes of existing antimicrobials [1], which threatens to jeopardize the sustainable development of clinical medicine, animal husbandry, aquaculture, and the food industry [2,3]. Over 3200 AMPs from various kingdoms (11% from plants, 11% from bacteria, 0.6% from fungi, 74% from animals), along with a more modest inventory of synthetic peptides, have been described. Among those from natural sources, only 2% of the peptides were identified from mollusks [9]. Mollusks are the second largest phylum of invertebrate animals, comprising 23% of all named marine organisms These sessile marine organisms lack adaptive immunity, and instead depend heavily on the innate immune system including cell-mediated and humoral components for recognition and elimination of invading microbes [10]. Previous works have focused on the purification and characterization of defensins in other mollusk species, such as oyster defensin from gill extracts of the American oyster (Crassostrea virginica) [17], the Pacific oyster (Crassostrea gigas) [18], and two defensins from H. discus discus [19], whereas the pharmaceutical potential of AMPs from marine mollusks remains scarcely explored
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