Physiological responses of Escherichia coli exposed to different heat-stress kinetics.
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.
Guyot
Stéphane
S
Laboratoire de Génie des Procédés Microbiologiques et Alimentaires-AgroSup Dijon, Université de Bourgogne, 1 Esplanade Erasme, 21000 Dijon, France.
Pottier
Laurence
L
Ferret
Eric
E
Gal
Laurent
L
Gervais
Patrick
P
D002462:Cell Membrane / Q000502:physiology; D002463:Cell Membrane Permeability; D004926:Escherichia coli / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000096:biosynthesis*; D018840:HSP70 Heat-Shock Proteins / Q000096:biosynthesis*; D018869:Heat-Shock Response; D006358:Hot Temperature; D050296:Microbial Viability
D029968:Escherichia coli Proteins; D018840:HSP70 Heat-Shock Proteins; C063842:dnaK protein, E coli