title: Cadaverine inhibition of porin plays a role in cell survival at acidic pH.
abstract: When grown at acidic pH, Escherichia coli cells secrete cadaverine, a polyamine known to inhibit porin-mediated outer membrane permeability. In order to understand the physiological significance of cadaverine excretion and the inhibition of porins, we isolated an OmpC mutant that showed resistance to spermine during growth and polyamine-resistant porin-mediated fluxes. Here, we show that the addition of exogenous cadaverine allows wild-type cells to survive a 30-min exposure to pH 3.6 better than cells expressing the cadaverine-insensitive OmpC porin. Competition experiments between strains expressing either wild-type or mutant OmpC showed that the lack of sensitivity of the porin to cadaverine confers a survival disadvantage to the mutant cells at reduced pH. On the basis of these results, we propose that the inhibition of porins by excreted cadaverine represents a novel mechanism that provides bacterial cells with the ability to survive acid stress.
authors.affiliation: Department of Biology and Biochemistry, University of Houston, Houston, TX 77204, USA.
authors.forename: Hrissi
authors.initials: H
authors.lastname: Samartzidou
authors.forename: Mahsa
authors.initials: M
authors.lastname: Mehrazin
authors.forename: Zhaohui
authors.initials: Z
authors.lastname: Xu
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Benedik
authors.forename: Anne H
authors.initials: AH
authors.lastname: Delcour
mesh_terms: D002103:Cadaverine / Q000494:pharmacology*; D002463:Cell Membrane Permeability / Q000187:drug effects; D003470:Culture Media; D024881:Drug Resistance, Bacterial; D004926:Escherichia coli / Q000235:genetics / Q000254:growth & development* / Q000502:physiology; D015964:Gene Expression Regulation, Bacterial; D006863:Hydrogen-Ion Concentration; D009154:Mutation; D018272:Porins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D013096:Spermine / Q000494:pharmacology
chemical_list: D003470:Culture Media; C113724:OmpC protein; D018272:Porins; D013096:Spermine; D002103:Cadaverine