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Modulators of Enterococcus faecalis Cell Envelope Integrity and Antimicrobial Resistance Influence Stable
Ismael L Banla1,2, Sushma Kommineni2, Michael Hayward2
1Department of Microbiology and Immunology, Medical College of Wisconsin, Milwaukee, Wisconsin, USA.
Abstract:
The Gram-positive bacterium Enterococcus faecalis is both a colonizer of the gastrointestinal tract (GIT) and an agent of serious nosocomial infections. Although it is typically required for pathogenesis, GIT colonization by E. faecalis is poorly understood. E. faecalis tolerates high concentrations of GIT antimicrobials, like cholate and lysozyme, leading us to hypothesize that resistance to intestinal antimicrobials is essential for long-term GIT colonization. Analyses of E. faecalis mutants exhibiting defects in antimicrobial resistance revealed that IreK, a determinant of envelope integrity and antimicrobial resistance, is required for long-term GIT colonization. IreK is a member of the PASTA kinase protein family, bacterial transmembrane signaling proteins implicated in the regulation of cell wall homeostasis. Among several determinants of cholate and lysozyme resistance in E. faecalis, IreK was the only one found to be required for intestinal colonization, emphasizing the importance of this protein to enterococcal adaptation to the GIT. By studying ΔireK suppressor mutants that recovered the ability to colonize the GIT, we identified two conserved enterococcal proteins (OG1RF_11271 and OG1RF_11272) that function antagonistically to IreK and interfere with cell envelope integrity, antimicrobial resistance, and GIT colonization. Our data suggest that IreK, through its kinase activity, inhibits the actions of these proteins. IreK, OG1RF_11271, and OG1RF_11272 are found in all enterococci, suggesting that their effect on GIT colonization is universal across enterococci. Thus, we have defined conserved genes in the enterococcal core genome that influence GIT colonization through their effect on enterococcal envelope integrity and antimicrobial resistance.
Insights
Enterococcus faecalis colonization of the gut requires resistance to intestinal antimicrobials. The IreK protein is essential for this resistance and gut colonization, inhibiting other proteins that disrupt cell envelope integrity.
Area of Science:
- Microbiology
- Bacterial Pathogenesis
- Gastrointestinal Microbiology
Background:
- Enterococcus faecalis colonizes the gastrointestinal tract (GIT) and causes nosocomial infections.
- Mechanisms of E. faecalis GIT colonization, particularly antimicrobial resistance, are poorly understood.
Purpose of the Study:
- To investigate the role of antimicrobial resistance in E. faecalis GIT colonization.
- To identify specific genes and proteins involved in enterococcal adaptation to the intestinal environment.
Main Methods:
- Analysis of E. faecalis mutants with defects in antimicrobial resistance.
- Identification and characterization of suppressor mutants.
- Investigating the function of conserved enterococcal proteins (OG1RF_11271 and OG1RF_11272).
Main Results:
- The IreK protein, a PASTA kinase, is crucial for E. faecalis long-term GIT colonization.
- IreK is essential for resistance to intestinal antimicrobials like cholate and lysozyme.
- Two conserved proteins, OG1RF_11271 and OG1RF_11272, antagonize IreK, impairing cell envelope integrity and colonization.
Conclusions:
- IreK's kinase activity inhibits antagonistic proteins, promoting cell envelope integrity and GIT colonization.
- IreK, OG1RF_11271, and OG1RF_11272 are conserved in all enterococci, suggesting a universal role in GIT colonization.
- These findings define core enterococcal genes influencing GIT adaptation via envelope integrity and antimicrobial resistance.