Enterobacter aerogenes OmpX, a cation-selective channel mar- and osmo-regulated

Area of Science:

• Microbiology
• Molecular Biology
• Biophysics

Background:

• Enterobacter aerogenes possesses major porins (Omp36, Omp35) that influence antibiotic permeability.
• Outer membrane protein X (OmpX) is a protein found in the outer membrane of Gram-negative bacteria.
• The role of OmpX in E. aerogenes, particularly its impact on porin expression and antibiotic resistance, requires further elucidation.

Purpose of the Study:

• To clone and characterize the ompX gene in Enterobacter aerogenes.
• To investigate the functional properties of the OmpX protein, including its channel activity.
• To determine the regulatory mechanisms influencing OmpX synthesis and its relationship with major porins and beta-lactam resistance.

Main Methods:

• Cloning and overexpression of the ompX gene in E. aerogenes.
• Analysis of outer membrane protein composition using techniques like SDS-PAGE.
• Reconstitution of purified OmpX into artificial lipid bilayers for electrophysiological studies.
• Gene expression analysis under varying conditions (MarA induction, high osmolarity).

Main Results:

• Overexpression of ompX led to decreased production of the major porin Omp36, correlating with increased beta-lactam resistance.
• Purified OmpX formed cation-selective ion channels with a conductance of 20 pS in 1 M NaCl.
• OmpX synthesis was upregulated by both MarA expression and high osmolarity, occurring concurrently with decreased expression of Omp35/Omp36.

Conclusions:

• OmpX plays a significant role in modulating the outer membrane permeability of E. aerogenes.
• The formation of ion channels by OmpX and its regulatory interplay with major porins contribute to beta-lactam resistance.
• OmpX synthesis is under complex regulation, influenced by both stress conditions and specific regulatory proteins like MarA.