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Proteobiotics are natural metabolites which are produced byfermentation process of specificprobiotic strains.[1][2] These small oligopeptides[3] were originally discovered in and isolated from culture media used to grow probiotic bacteria and may account for some of the health benefits of probiotics.
Several genera of probiotic bacteria are known to produce proteobiotics, includingLactococcus spp.,[3]Pediococcus spp.[3]Lactobacillus spp.[4] andBifidobacterium spp.[5]
Recent studies have explored mode of action of proteobiotics and their potential benefits in maintaining the ratio of beneficial bacteria, lowering bacterial imbalance, and improving gut function. However, any of the statements based on research have not been evaluated by the US Food and Drug Administration.
Unlike other molecules produced by probiotic bacteria, such as organic acids andbacteriocins, proteobiotics are natural metabolites which interfere withquorum sensing, the cell-to-cell communications which occur between bacterial cells, mainly by interfering with the LuxS quorum sensing system.[5][4][1] These quorum-sensing systems allow bacteria to respond to changes in their environment and play a role in the ability of pathogens to evade host defence mechanisms. By interfering with quorum sensing, proteobiotics inhibit the cascade of events leading to adhesion to, and invasion of, host cells. This is achieved through reduced expression of specific virulence genes (typically found onpathogenicity islands) that facilitate the infection process. Specifically, proteobiotics inhibit virulence genes involved intoxin production,[4][1]biofilm formation,[6]cell adhesion[5][7] and invasion.[8][3] In enterohemorrhagicE. coli andSalmonella spp., genes associated with Type 3 Secretion Systems seem to be the main targets.[9]
The degree to which proteobiotics can reduce virulence-gene expression depends on the pathogen and the source of the proteobiotics.Lactobacillus acidophilus-derived proteobiotics down-regulate virulence genes in enterohemorrhagicEscherichia coli,[4]Clostridioides difficile[1], Salmonella Typhimurium[3], Listeria monocytogenes[10] andCampylobacter jejuni[8]. Whereas those produced byBifidobacterium spp. have been shown to impact virulence gene expression inCampylobacter jejuni,[8] enterohemorrhagicEscherichia coli,[4]Clostridioides difficile,[1]Clostridium perfringens,[7] andSalmonella Typhimurium[9].