Role ofrpoSin the Development of Cell Envelope Resilience and Pressure Resistance in Stationary-Phase Escherichia coli

Author:

Charoenwong Duangkamol,Andrews Simon,Mackey Bernard

Abstract

ABSTRACTThis work investigated the role ofrpoSin the development of increased cell envelope resilience and enhanced pressure resistance in stationary-phase cells ofEscherichia coli. Loss of both colony-forming ability and membrane integrity, measured as uptake of propidium iodide (PI), occurred at lower pressures inE. coliBW3709 (rpoS) than in the parental strain (BW2952). TherpoSmutant also released much higher concentrations of protein under pressure than the parent. We propose that RpoS-regulated functions are responsible for the increase in membrane resilience as cells enter stationary phase and that this plays a major role in the development of pressure resistance. Strains from the Keio collection with mutations in two RpoS-regulated genes,cfa(cyclopropane fatty acyl phospholipid synthase) andosmB(outer membrane lipoprotein), were significantly more pressure sensitive and took up more PI than the parent strain, withcfahaving the greatest effect. Mutations in thebolAmorphogene and other RpoS-regulated lipoprotein genes (osmC,osmE,osmY, andybaY) had no effect on pressure resistance. The cytoplasmic membranes of therpoSmutant failed to reseal after pressure treatment, and strains with mutations inosmBandnlpI(new lipoprotein) were also somewhat impaired in the ability to reseal their membranes. Thecfamutant, though pressure sensitive, was unaffected in membrane resealing, implying that the initial transient permeabilization event is critical for loss of viability rather than the failure to reseal. The enhanced pressure sensitivity ofpolA,recA, andxthAmutants suggested that DNA may be a target of oxidative stress in pressure-treated cells.

Publisher

American Society for Microbiology

Subject

Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology

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