Physiological responses of Escherichia coli exposed to different heat-stress kinetics

Abstract

The effects of heat-stress kinetics on the viability of Escherichia coli were investigated. Cells were exposed to heat-stress treatments extending from 30 to 50 degrees C, with either a slope (40 min) or a shock (10 s), both followed by a 1-h plateau at 50 degrees C in nutritive medium. A higher survival rate was observed after the slope than after the shock, when both were followed by a plateau, so the heat slope induced a certain degree of thermotolerance. This tolerance was partly (i) linked to de novo protein synthesis during the subsequent plateau phase, and (ii) abolished after rapid cooling from 50 to 30 degrees C, which means that cellular components with rapidly reversible thermal properties are involved in this type of thermotolerance. The heat-slope-induced thermotolerance was chiefly linked to the maintenance of the plasma membrane integrity (preservation of structure, fluidity, and permeability), and not to GroEL or DnaK overexpression. Moreover, the high level of cell mortality induced by the heat shock could be related to changes in the membrane integrity.

Solute Transport Proteins and the Outer Membrane Protein NmpC Contribute to Heat Resistance of Escherichia coli AW1.7

“…E. coli GGG10 harboring pYFP-nmpC exhibited substantially improved survival at 60°C. The increase in heat resistance observed upon the expression of NmpC in E. coli GGG10 was greater than the increase observed upon the induction of a heat shock response (20,43), starvation (45), or overexpression of evgA, which encodes a transcriptional regulator (15). However, E. coli GGG10 harboring pYFP-nmpC was substantially less heat resistant than E. coli AW1.7.…”

“…Homoviscous adaptation of the cytoplasmic membrane through alteration of membrane lipid composition maintains bacterial membranes in a functional, liquid crystalline state during heat stress (5,20,39). To determine whether an altered profile of membrane lipids contributes to the heat resistance of E. coli AW1.7, the membrane fatty acid composition of late-exponential-phase and heat-stressed cultures was compared to that of E. coli GGG10 ( Table 2).…”

“…However, the heat resistance of E. coli is highly variable among different strains and individual strains exhibit D 60 values of up to 6.5 min (8,21,25,37). The heat resistance of individual strains of E. coli relates to their ability adapt to heat stress by the homoviscous adaptation of the plasma membrane, as well as the synthesis of heat shock proteins (20,43). The 32 -induced expression of heat shock proteins after sublethal thermal stress increases resistance to lethal heat treatment (43; for a review, see reference 6).…”

Carbon Capture and Sequestration: Biological Technologies

“…These results demonstrate that the engineered bacterial cell with periplasmic ngCA can successfully serve as an efficient biocatalyst for CO 2 sequestration. The mechanisms may also include protection by heat shock proteins or an increase in ion permeability caused by the elevated temperature (Guyot et al 2010). In this study, they expect that finding or engineering a thermostable CA would synergistically improve the thermal stability of the periplasmic whole-cell system for practical application to post combustion capture of industrial CO 2 .…”

Engineered Escherichia coli with Periplasmic Carbonic Anhydrase as a Biocatalyst for CO2Sequestration

“…Immobilization of ngCA in the periplasm, a hypothetic reason for the resistance to periplasmic release by osmotic shock, may be the responsible factor contributing to the enhanced thermal stability. The mechanisms may also include protection by heat shock proteins (54) or an increase in ion permeability caused by the elevated temperature (55). We expect that finding or engineering a thermostable CA would synergistically improve the thermal stability of the periplasmic whole-cell system for practical application to postcombustion capture of industrial CO 2 .…”