The Leaderless Bacteriocin Enterocin K1 Is Highly Potent against Enterococcus faecium: A Study on Structure, Target...

Area of Science:

• Microbiology and Molecular Biology
• Bacteriocin Research
• Antimicrobial Resistance Mechanisms

Background:

• Leaderless bacteriocins like Enterocin K1 (EntK1) and Enterocin EJ97 (EntEJ97) exhibit broad-spectrum antimicrobial activity, including against multidrug-resistant Enterococcus faecium.
• Understanding bacteriocin-receptor interactions is crucial for developing novel antimicrobial strategies.
• The stress response protease RseP is implicated in bacterial defense mechanisms.

Purpose of the Study:

• To elucidate the mechanism of resistance to bacteriocins EntK1 and EntEJ97 in enterococci.
• To identify the specific bacterial component involved in bacteriocin recognition and uptake.
• To explore the potential of a combined bacteriocin-heat stress strategy for bacterial control.

Main Methods:

• Isolation and characterization of bacteriocin-resistant enterococcal mutants.
• Genetic analysis to identify mutations in resistant strains, focusing on the rseP gene.
• Heterologous expression of enterococcal rseP in Streptococcus pneumoniae to assess sensitivity.
• Site-directed mutagenesis of the conserved active site residues in RseP.
• Growth assays of wild-type and mutant strains under varying temperature conditions.

Main Results:

• Mutations in the rseP gene conferred high-level resistance to EntK1 and EntEJ97.
• Heterologous expression of enterococcal rseP restored sensitivity to EntK1 and EntEJ97 in resistant S. pneumoniae.
• The proteolytic active site of RseP is partially required for bacteriocin activity, indicating a receptor function.
• Mutants with rseP mutations exhibited impaired growth at elevated temperatures (45°C).

Conclusions:

• RseP functions as a receptor for bacteriocins EntK1 and EntEJ97.
• The proteolytic activity of RseP plays a role in mediating bacteriocin sensitivity.
• A hurdle strategy combining bacteriocins with heat stress effectively eliminates sensitive bacteria and prevents resistance development.