PerC and GrlA independently regulate Ler expression in enteropathogenic Escherichia coli

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• Ler is a key regulator of the locus of enterocyte effacement (LEE) in attaching and effacing (A/E) pathogens.
• Ler counteracts H-NS silencing to induce LEE gene expression, crucial for virulence.
• The role of PerC, encoded by the EAF plasmid in enteropathogenic Escherichia coli (EPEC), in virulence regulation was unclear.

Purpose of the Study:

• To elucidate the precise role of PerC in EPEC virulence gene regulation.
• To investigate the interplay between PerC, GrlA, and H-NS in controlling ler expression.
• To understand the evolutionary significance of regulatory mechanisms in EPEC colonization.

Main Methods:

• Investigated the independent and combined effects of PerC and GrlA on ler expression.
• Assessed the role of Integration Host Factor (IHF) in the regulatory network.
• Compared regulatory mechanisms in EPEC strains with and without the EAF plasmid.

Main Results:

• PerC and GrlA can independently activate ler expression and subsequent LEE gene expression.
• Both PerC and GrlA, with IHF assistance, counteract H-NS repression of ler.
• These regulators can also enhance ler activity beyond overcoming repression.

Conclusions:

• PerC and GrlA are key activators of ler expression in EPEC, with distinct roles depending on growth conditions.
• Convergent regulatory mechanisms involving PerC and GrlA likely evolved to coordinate virulence factor expression.
• These adaptations facilitate EPEC's successful colonization of the intestinal niche.