A protein important for antimicrobial peptide resistance, YdeI/OmdA, is in the periplasm and interacts with OmpD/NmpC

Area of Science:

• Microbiology
• Bacterial Physiology
• Host-Pathogen Interactions

Background:

• Antimicrobial peptides (AMPs) are crucial for innate immunity, killing microbes across diverse environments.
• Bacteria, like Salmonella enterica, possess sophisticated sensor-kinase systems (PhoP-PhoQ, PmrA-PmrB, RcsB-RcsC-RcsD) to detect and respond to AMPs.
• The ydeI gene product, an oligosaccharide/oligonucleotide binding-fold (OB-fold) protein, is known to confer resistance to polymyxin B and contribute to virulence.

Purpose of the Study:

• To investigate the regulatory networks controlling ydeI expression in response to AMPs.
• To elucidate the function of YdeI in bacterial resistance mechanisms beyond lipopolysaccharide (LPS) modification.
• To identify potential protein interactors of YdeI and their role in AMP resistance.

Main Methods:

• Gene expression analysis under AMP stress.
• Biochemical copurification assays to identify YdeI interacting partners.
• Genetic analysis of ompD and ydeI mutants for AMP resistance phenotypes.
• Subcellular localization studies of YdeI.

Main Results:

• ydeI is additionally regulated by the PhoP-PhoQ and PmrA-PmrB sensor-kinase systems.
• YdeI copurifies with the outer membrane porin OmpD/NmpC.
• Genetic evidence shows YdeI and OmpD are essential for resistance to cathelicidin antimicrobial peptide.
• YdeI localizes to the periplasm, suggesting interaction with OmpD.

Conclusions:

• Periplasmic OB-fold proteins, such as YdeI, can interact with outer membrane porins like OmpD to confer bacterial resistance to AMPs.
• This interaction represents a novel mechanism for bacterial defense against host-derived antimicrobial peptides.
• The findings expand our understanding of bacterial adaptation strategies in hostile environments.