Involvement of alkylhydroxybenzenes in the Escherichia coli response to the lethal effect of UV irradiation

摘要

This work is concerned with the role of alkylhydroxybenzenes (AHBs), chemical analogs of the autoregulatory microbial d _1 factors, on the development of the stress response of bacterial cells to UV irradiation, including SOS system induction, preservation of cell viability, and S → R phase transitions of the Escherichia coli test strain with the bioluminescence genes cloned under the control of the recA gene promoter. UV irradiation, a natural stress factor, and an increase in AHB concentrations were found to elicit uniform responses in bacteria, indicating that AHBs function as alarmones, i. e., alarm signals. It was revealed that preincubating bacteria with alkylhydroxybenzenes considerably enhanced their viability upon irradiation with lethal UV doses; this was accompanied by a relative decrease in the SOS response activity and a concomitant increase in the frequency of phase transitions. The efficiency of the protective action of AHBs increased with an increase in their hydrophobicity degree. The probable mechanism of the protective effect of AHBs is discussed, based on their capacity for the interaction with biopolymers, which results in changing their structural organization and conferring resistance to a broad spectrum of stress factors. Such a "passive" protective mechanism reduces the susceptibility of DNA to UV irradiation, causing a decrease in the parameters related to the SOS system induction that is responsible for the "active" protective mechanism in bacterial cells. As a result, viability retention under the lethal influence of UV irradiation is possible at minimal values of repair activity and is accompanied by an increase in the phenotypic variability of the surviving part of a bacterial population.