Sodium Dodecyl Sulfate-Eethylenediaminetetraacetic Acid Sensitive Phenotype Associated with ompC Deficient Escherichia coli Strains is Observed Primarily in Cells Growing in Stationary Phase and Less So in Cells Growing in Log Phase

The highly conserved, multi-component Mla inter-membrane lipid trafficking system is proposed to be involved in maintaining outer membrane lipid asymmetry. It has been shown that MlaA interacts with both the OmpC and OmpF porins. OmpC deficient strains have been shown to accumulate phospholipids in the outer membrane outer leaflet during stationary phase, indicating a role in lipid asymmetry maintenance during stationary phase. ΔompC cells are known to have outer membrane permeability defects and show increased sensitivity to sodium dodecyl sulfate (SDS) and ethylenediaminetetraacetic acid (EDTA) treatment. In this study, we investigated the importance of OmpC in maintaining lipid asymmetry using an adapted minimum inhibitory concentration assay (MIC). Previous studies have tested the sensitivity of ΔompC mutant strains of Escherichia coli. We hypothesized that complementing ompC using a plasmid would restore a SDS-EDTA resistant phenotype to these strains. Previous studies have shown that ΔompC cells are affected in stationary phase. We looked at SDS-EDTA sensitivity of
ΔompC mutant JW2203 and the importance of the porin during both stationary and log-phase growth of E. coli. Growth phase experiments suggest that JW2203 ΔompC mutants are more sensitive to the effects of SDS-EDTA during stationary phase than log phase, and this observation is consistent with previous studies. Overall, our data suggests that growth phase may impact the SDS-EDTA sensitivity of E. coli strain JW2203.