Enterococcus faecalis pCF10‐encoded surface proteins PrgA, PrgB (aggregation substance) and PrgC contribute to plasmid transfer, biofilm formation and virulence

Abstract

SUMMARY Enterococcus faecalis pCF10 transfers at high frequencies upon pheromone induction of the prgQ transfer operon. This operon codes for three cell-wall-anchored proteins - PrgA, PrgB (aggregation substance), and PrgC - and a type IV secretion system through which the plasmid is delivered to recipient cells. Here, we defined the contributions of the Prg surface proteins to plasmid transfer, biofilm formation, and virulence using the Caenorhabditis elegans infection model. We report that a combination of PrgB and extracellular DNA (eDNA), but not PrgA or PrgC, was required for extensive cellular aggregation and pCF10 transfer at wild-type frequencies. In addition to PrgB and eDNA, production of PrgA was necessary for extensive binding of enterococci to abiotic surfaces and development of robust biofilms. However, although PrgB is a known virulence factor in mammalian infection models, we determined that PrgA and PrgC, but not PrgB, were required for efficient killing in the worm infection model. We propose that the pheromone-responsive, conjugative plasmids of E. faecalis have retained Prg-like surface functions over evolutionary time for attachment, colonization and robust biofilm development. In natural settings, these biofilms are polymicrobial in composition and constitute optimal environments for signal exchange, mating pair formation, and widespread lateral gene transfer.

Multiple Roles for Enterococcus faecalis Glycosyltransferases in Biofilm-Associated Antibiotic Resistance, Cell Envelope Integrity, and Conjugative Transfer

“…Waters et al (67) demonstrated that AS directly binds LTA in vitro but LTA is not sufficient for bacterial aggregation. A more complex scenario, in which PrgB mediates interactions with extracellular DNA to enhance aggregation, was recently proposed by Bhatty et al (68). Our findings suggest that EpaI contributes to the formation of EBS, implying that the Epa polysaccharide may be a component of EBS.…”

Antigen I/II encoded by integrative and conjugative elements of Streptococcus agalactiae and role in biofilm formation

“…PrgA could play a role in PrgB processing and form an adhesion complex with PrgB [18]. Furthermore, the same authors showed that other proteins (the cell-wall hydrolase and the VirB4-like ATPase) encoded by the plasmid could also play a role in biofilm formation [18]. …”

“…ICE_515_tRNA Lys , which also encodes a new CAMP factor conferring hemolytic properties recently reported that co-synthesis of PrgA and PrgB of pCF10 is required for robust biofilm development [18]. PrgA could play a role in PrgB processing and form an adhesion complex with PrgB [18].…”

Examination of Enterococcus faecalis Toxin-Antitoxin System Toxin Fst Function Utilizing a Pheromone-Inducible Expression Vector with Tight Repression and Broad Dynamic Range

“…As demonstrated above, in the presence of the coresident gene for the PrgX negative regulator, the P Q promoter is tightly repressed, responds to nanogram-per-milliliter concentrations of the innocuous cCF10 peptide pheromone, and has a large expression range over a fairly narrow inducer concentration range (roughly 1 to 20 ng of cCF10 per ml). While the experiments reported here all employed M9YEG medium, cCF10 pheromone-inducible heterologous gene expression also can be used in more complex media such as brain heart infusion or tryptic soy broth, with appropriate adjustments of inducing concentrations of cCF10 (33). Adjustments may also be required for induction under conditions other than exponential phase.…”