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

Abstract

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 irradi ation, 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 pro moter. UV irradiation, a natural stress factor, and an increase in AHB concentrations were found to elicit uni form 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 concom itant 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 struc tural 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.

Effect of alkylresorcinols on thermal denaturation and refolding of bacterial luciferase and synthesis of heat shock proteins revealed in the luminescent molecular and cellular test systems

“…Another newly discovered effect of ARs, and also a dose dependent one, is moderate induction of HSP synthesis by long chain homologues C 11 , C 12 , and C 18 AR, which resulted in a 2.7 to 4 fold stimulation of cell luminescence at concentrations of 10 -4 M. These results agree with the previously demonstrated effect of long chain ARs as alarm signals activating the expression of stress genes (SOS response and rpoS reg ulon) in E. coli [10,13]. The effect of long chain ARs on HSP synthesis has not been previously demon strated; it adds to their effects as stress imitators.…”

“…Many years of research into the nature of this phenomenon made it possible to associate the protective effects of ARs with two major mechanisms; the first is direct protection of bacterial cells from the damaging factors and the second is an alarm signal to mobilize resources for protection. While the alarm signal function of ARs is mediated through control of stress regulon expres sion [10,13], their protective effect develops via struc tural modification of a wide range of cell biopolymers, of which enzymes are of particular importance [9].…”

“…In this study, we used synthetic analogues of micro bial AHBs, including the commercially available agents C 7 AR, C 11 AR, and C 12 AR (Sigma, United States) and C 9 AR and C 18 AR synthesized by the company Enamine (Ukraine), all 99.9% pure [13].…”

“…Studies of AR functions in generation of bacterial stress response demonstrated that various extreme factors (for example, heat shock) stimulated AR biosynthesis [21], while elevated AR levels affected cell stability [8,22,23] by means of increased func tional and operational stability of the enzymes [9,20,24] on the one hand, and activation of stress gene expression, on the other [10,13]. It was therefore log ical to assume that changes in AR concentration in a microbial culture can affect the induction of heat shock protein synthesis, in particular, syntesis of the IbpA chaperone [6].…”