Proteobiotics are natural metabolites which are produced by

fermentation process Fermentation is a type of anaerobic metabolism which harnesses the redox potential of the reactants to make adenosine triphosphate (ATP) and organic end products. Organic molecules, such as glucose or other sugars, are catabolized and reduced ...

of specific

probiotic Probiotics are live microorganisms that provide health benefits when consumed, generally by improving or restoring the microbiota in the gut. Probiotics are considered generally safe to consume, but may cause bacteria– host interactions ...

strains. These small oligopeptidesTessema, Akalate. "Lactic Acid Bacteria and Culture Media for the Production of Potential Antivirulence Peptides against ''Salmonella Typhimurium''." M.Sc. Thesis. University of Guelph, 2015. 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, including ''

Lactococcus ''Lactococcus'', from Latin 'lac', meaning "milk", and Ancient Greek κόκκος (''kókkos''), meaning "sphere", is a genus of lactic acid bacteria that were formerly included in the genus ''Streptococcus'' Group N1. They are known as homoferme ...

'' spp., ''

Pediococcus ''Pediococcus'' is a genus of gram-positive lactic acid bacteria, placed within the family of Lactobacillaceae. They usually occur in pairs or tetrads, and divide along two planes of symmetry, as do the other lactic acid cocci genera '' Aerococc ...

'' spp. ''

Lactobacillus ''Lactobacillus'' is a genus of gram-positive, aerotolerant anaerobes or microaerophilic, rod-shaped, non-spore-forming bacteria. Until 2020, the genus ''Lactobacillus'' comprised over 260 phylogenetically, ecologically, and metabolically div ...

'' spp. and ''

Bifidobacterium ''Bifidobacterium'' is a genus of gram-positive, nonmotile, often branched anaerobic bacteria. They are ubiquitous inhabitants of the gastrointestinal tract though strains have been isolated from the vagina and mouth ('' B. dentium'') of mamma ...

'' spp. __TOC__

Mode of action

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 and

bacteriocin Bacteriocins are proteinaceous or peptide, peptidic toxins produced by bacteria to inhibit the growth of similar or closely related bacterial strain(s). They are similar to yeast and paramecium killing factors, and are structurally, functionally ...

s, proteobiotics are natural metabolites which interfere with

quorum sensing In biology, quorum sensing or quorum signaling (QS) is the process of cell-to-cell communication that allows bacteria to detect and respond to cell population density by gene regulation, typically as a means of acclimating to environmental disadv ...

, the cell-to-cell communications which occur between bacterial cells, mainly by interfering with the LuxS quorum sensing system. 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 on

pathogenicity island Pathogenicity islands (PAIs), as termed in 1990, are a distinct class of genomic islands acquired by microorganisms through horizontal gene transfer. Pathogenicity islands are found in both animal and plant pathogens. Additionally, PAIs are found i ...

s) that facilitate the infection process. Specifically, proteobiotics inhibit virulence genes involved in toxin production,

biofilm formation A biofilm is a syntrophic community of microorganisms in which cells stick to each other and often also to a surface. These adherent cells become embedded within a slimy extracellular matrix that is composed of extracellular polymeri ...

cell adhesion Cell adhesion is the process by which cells interact and attach to neighbouring cells through specialised molecules of the cell surface. This process can occur either through direct contact between cell surfaces such as Cell_junction, cell junc ...

Troll, Marie-Luise. "Investigating the Anti-Virulent Activity of Probiotic Bioactives on ''Clostridium Perfringens''." M.Sc. Thesis. Universitat Autònoma de Barcelona, 2014. and invasion. In enterohemorrhagic ''E. coli'' and ''Salmonella'' spp., genes associated with Type 3 Secretion Systems seem to be the main targets. 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 enterohemorrhagic ''Escherichia coli'', ''Clostridioides difficile'''', Salmonella'' Typhimurium'', Listeria monocytogenes''Delcenserie, V.; Griffiths, M.W. "Mitigation of the Effects of ''Listeria monocytogenes'' using probiotics." Presentation at OMAF 2013 Food Safety Research Forum, May 9, 2013, Guelph, ON. and ''Campylobacter jejuni''''.'' Whereas those produced by ''Bifidobacterium'' spp. have been shown to impact virulence gene expression in ''Campylobacter jejuni'', enterohemorrhagic ''Escherichia coli'', ''Clostridioides difficile'', ''Clostridium perfringens'', and ''Salmonella'' Typhimurium''.'' ----

References

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