Escherichia coli OmpC Mutants Are Sensitive to Ethylenediaminetetraacetic acid and Sodium Dodecyl Sulfate Treatment Whereas Double OmpC and OmpF Mutants Are Not

The Mla pathway is hypothesized to be an ATP binding cassette transport system in Escherichia coli that maintains outer membrane asymmetry. Outer membrane proteins C (OmpC) and F (OmpF) have been shown to interact with MlaA, a key lipoprotein in the Mla pathway. Escherichia coli ompC mutants in strain MC4100 have previously been shown to be more sensitive to treatment with ethylenediaminetetraacetic acid (EDTA) and sodium dodecyl sulfate (SDS) which disrupt lipids stability and solubilizes the outer membrane. Sensitivity to these agents has been used as an indicator for maintenance of outer membrane asymmetry. In this study we sought to test additional strains of E. coli bearing ompC mutations to further characterize this phenotype. We acquired several strains of E. coli bearing mutations in either ompC or both ompC and ompF. We adapted a broth dilution minimal inhibitory concentration assay to compare resistance of E. coli as a proxy for membrane asymmetry. Our data are consistent with previous reports showing EDTA/SDS sensitivity in ompC mutants to treatment with EDTA / SDS. Surprisingly, ompC and ompF double mutants showed a similar level of sensitivity to EDTA/SDS as the isogenic wild type strain of E. coli. This observation may suggest a relationship between OmpC, OmpF, and MlaA in the Mla pathway.