title: Quantitative measurement of the outer membrane permeability in Escherichia coli lpp and tol-pal mutants defines the significance of Tol-Pal function for maintaining drug resistance.
abstract: Ensuring the stability of the outer membrane permeability barrier is crucial for maintaining drug resistance in Gram-negative bacteria. Lpp protein and Tol-Pal complex are responsible for this function and are widely distributed among Gram-negative bacteria. Thus, these proteins are potential targets to permeabilize the outer membrane barrier. Although deleting these proteins is known to impair the outer membrane stability, the effect of the deletion on the outer membrane barrier property and on the drug resistance has not been fully characterized and evaluated in a quantitative manner. Here, we determined the outer membrane permeability of Escherichia coli Δlpp and Δtol-pal mutants by the assay using intact cells and liposomes reconstituted with the outer membrane proteins. We determined that there was 3- to 5-fold increase of the permeability in Δtol-pal mutants, but not in Δlpp mutant, compared with that in the parental strain. The permeability increase in Δtol-pal mutants occurred without affecting the function of outer membrane diffusion channels, and was most pronounced in the cells at exponential growth phase. The impact of tol-pal deletion on the drug resistance was revealed to be almost comparable with that of deletion of acrAB, a major multidrug efflux transporter of E. coli that makes a predominant contribution to drug resistance. Our observations highlight the importance of Tol-Pal as a possible target to combat multidrug-resistant Gram-negative bacteria.
authors.affiliation: Graduate School of Life Sciences, Tohoku University, Sendai, Japan.
authors.forename: Hikaru
authors.initials: H
authors.lastname: Kowata
authors.affiliation: Graduate School of Life Sciences, Tohoku University, Sendai, Japan.
authors.forename: Saeko
authors.initials: S
authors.lastname: Tochigi
authors.affiliation: Graduate School of Life Sciences, Tohoku University, Sendai, Japan.
authors.forename: Tomonobu
authors.initials: T
authors.lastname: Kusano
authors.affiliation: Graduate School of Life Sciences, Tohoku University, Sendai, Japan.|Frontier Research Institute for Interdisciplinary Sciences, Tohoku University, Sendai, Japan.
authors.forename: Seiji
authors.initials: S
authors.lastname: Kojima
mesh_terms: D000900:Anti-Bacterial Agents / Q000493:pharmacokinetics; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D002463:Cell Membrane Permeability; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics*; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism; D017353:Gene Deletion; D008826:Microbial Sensitivity Tests; D010400:Penicillin G / Q000493:pharmacokinetics
chemical_list: D000900:Anti-Bacterial Agents; D001425:Bacterial Outer Membrane Proteins; D029968:Escherichia coli Proteins; D010400:Penicillin G