. We have shown that firefly luciferase expressed in E.coli cells is a sensitive marker for studying of influence of mild heat stress on viability of living cells. Luciferase is produced in cells as a soluble and active form that allows measuring the luminescence of cells for a long time without essential decrease in intensity. We have compared the mechanisms of thermal inactivation of the firefly luciferase in living cells and of purified enzyme in buffer system and found that luciferase inactivation follows the first order kinetics independently on microenvironment. Kinetic and activation parameters of this process for both systems were identical. It is important the rates of thermal inactivation of the enzyme in cells were comparable to the rates of viability decrease of E.coli (CFU/ml). At the same time the ATP content as indicator of metabolic status of living cells (ATP) changed under more difficult law - it was observed the increasing of intracellular ATP in E.coli within the first 20 min of heating of cellular suspension.
firefly luciferase, bioluminescence, thermal inactivation, E.coli BL21, cell viability, heat stress
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