Indole signaling decreases biofilm formation and related virulence of Listeria monocytogenes

Abstract

Bacterial communication system known as quorum-sensing (QS) is a pivotal system for bacterial survival, adaptation and pathogenesis. Members in the multicellular community may synthesize or acquire a signaling molecule in order to elicit downstream cellular processes. Roles of indole and derivatives, a new class of quorum-sensing signal molecules, in various bacterial physiologies and virulence have been reported recently. Indole is normally found in mammal gastrointestinal tract as a metabolite of tryptophan metabolism by microbiota. Therefore, interspecies connection via indole signaling among commensal bacteria and enteric pathogens could be anticipated. Effects of indole exposure on the virulence of Listeria monocytogenes were investigated by phenotypic and molecular approaches. Results demonstrated that synthetic indole and indole-rich conditioned medium significantly diminished biofilm formation and related virulence of L. monocytogenes including motility, cell aggregation and exopolysaccharide (EPS) production. Transcript levels of virulence-associated (pssE, dltA, flaA, fliI, motB, agrA and hly) and regulatory-genes (codY, sigB, prfA and gmaR) were substantially down-regulated in indole-treated cells. Only mogR gene encoding for a repressor of motility genes was up-regulated after indole exposure. Our findings raise the possibility that L. monocytogenes may acquire indole signaling from gut microbiota for resource-effective adaptation upon transition to new environment.

Dose-Dependent Beneficial Effects of Tryptophan and Its Derived Metabolites on Akkermansia In Vitro: A Preliminary Prospective Study

“…This phenomenon indicated that indole might be an important signaling molecule in growth and adhesion of A. muciniphila . Furthermore, indole could decrease the biofilm and virulence of pathogenic bacteria, such as Listeria monocytogenes [ 33 ]. IAA can be produced by Bifidobacterium , which could lessen inflammatory responses in the liver caused by a high-fat diet, and these effects were dependent on the AHR pathway [ 34 ].…”

Counteracting Bacterial Motility: A Promising Strategy to Narrow Listeria monocytogenes Biofilm in Food Processing Industry

“…Recently, a new study reported the antibiofilm activity of synthetic indole. In fact, it has been shown that this molecule significantly diminished biofilm formation and related virulence of L. monocytogenes including motility, cell aggregation and exopolysaccharide production ( Rattanaphan et al, 2020 ).…”

The role of the microbiome in ovarian cancer: mechanistic insights into oncobiosis and to bacterial metabolite signaling

“…spermine, spermidine) are organic molecules with more than two amine groups. Polyamines support bacterial growth and biofilm formation and through these, in pathogenic species, polyamines are virulence factors (Michael et al 2018 ) and quorum sensing signals (Rattanaphan et al 2020 ; Inaba et al 2020 ). Some circulating polyamines may be of bacterial, human, and/or dietary origin (Ramos-Molina et al 2019 ).…”