Gram-negative quorum sensing signalling enhances biofilm formation and virulence traits in gram-positive pathogen Enterococcus faecalis

• Published in: Journal of oral microbiology 2023, Vol.15 (1), p.2208901-2208901
• Main Authors: Parga, Ana, Manoil, Daniel, Brundin, Malin, Otero, Ana, Belibasakis, Georgios N.
• Format: Article
• Language: English
• Subjects: acyl-homoserine lactones; Adhesins; Bacteria; biofilm formation; Biofilms; cell-to-cell communication; Cellular stress response; Confocal microscopy; Dental roots; endodontic infection; Enterococcus faecalis; Fsrc; Gene expression; Genes; Gentian violet; Glycosyltransferase; Gram-negative bacteria; Lactones; Original; Quorum sensing; reverse-transcription quantitative PCR; Strains (organisms); Virulence
• ISSN: 2000-2297; 2000-2297
• DOI: 10.1080/20002297.2023.2208901

Acyl-homoserine lactones (AHLs) are typical quorum-sensing molecules of gram-negative bacteria. Recent evidence suggests that AHLs may also affect gram-positives, although knowledge of these interactions remains scarce. Here, we assessed the effect of AHLs on biofilm formation and transcriptional regulations in the gram-positive Enterococcus faecalis. Five E. faecalis strains were investigated herein. Crystal violet was employed to quantify the biomass formed, and confocal microscopy in combination with SYTO9/PI allowed the visualisation of biofilms' structure. The differential expression of 10 genes involved in quorum-sensing, biofilm formation and stress responses was evaluated using reverse-transcription-qPCR. The AHL exposure significantly increased biofilm production in strain ATCC 29212 and two isolates from infected dental roots, UmID4 and UmID5. In strains ATCC 29212 and UmID7, AHLs up-regulated the quorum-sensing genes (fsrC, cylA), the adhesins ace, efaA and asa1, together with the glycosyltransferase epaQ. In strain UmID7, AHL exposure additionally up-regulated two membrane-stress response genes (σ V , groEL) associated with increased stress-tolerance and virulence. Altogether, our results demonstrate that AHLs promote biofilm formation and up-regulate a transcriptional network involved in virulence and stress tolerance in several E. faecalis strains. These data provide yet-unreported insights into E. faecalis biofilm responses to AHLs, a family of molecules long-considered the monopole of gram-negative signalling.