Role for Outer Membrane Cytochromes OmcA and OmcB of Shewanella putrefaciens MR-1 in Reduction of Manganese Dioxide

Abstract
Several natural isolates of Escherichia coliO157:H7 have previously been shown to exhibit stationary-phase-dependent variation in their resistance to inactivation by high hydrostatic pressure. In this report we demonstrate that loss of the stationary-phase-inducible sigma factor RpoS resulted in decreased resistance to pressure inE. coli O157:H7 and in a commensal strain. Furthermore, variation in the RpoS activity of the natural isolates of O157:H7 correlated with the pressure resistance of those strains. Heterogeneity was noted in the rpoS alleles of the natural isolates that may explain the differences in RpoS activity. These results are consistent with a role for rpoS in mediating resistance to high hydrostatic pressure in E. coliO157:H7.