[Succinate dehydrogenase activity of Escherichia coli cells after heat stress and during the reparative process]

The resting cells of different E. coli cells remained viable after their heating at 48 degrees C for 30 min. The activity of their succinate dehydrogenase (SDH) (EC 1.3.99.1) was not more than 50% of the control one. When the cells were inoculated after a heat stress into a peptone medium, they started to grow at a high rate. However, their maximal specific growth rate mu and the overall biomass yield were less than in the control. The SDH activity of the cells reached the original level by the end of the logarithmic growth phase. This did not happen when the cells were incubated in 0.14 M NaCl for a time necessary for the culture to reach the end of the logarithmic growth phase. The SDH activity (in absolute values) of cell-free extracts was not greater than 35% of the cell SDH activity. The SDH activity of the cell-free extracts did not change after their heating at 48 degrees C. The SDH activity of E. coli cells is recommended to be used as a parameter indicative of their stress state.