Evidence for a specific regulation of recA gene transcription in Escherichia coli

Interaction of RecA mediated SOS response with bacterial persistence, biofilm formation, and host response

Antibiotics have a primary mode of actions, and most of them have a common secondary mode of action via reactive species (ROS and RNS) mediated DNA damage. Bacteria have been able to tolerate this DNA damage by SOS (Save-Our-Soul) response. RecA is the universal essential key protein of the DNA damage mediated SOS repair in various bacteria including ESKAPE pathogens. In addition, antibiotics also triggers activation of various other bacterial mechanisms such as biofilm formation, host dependent responses, persister subpopulation formation. These supporting the survival of bacteria in unfriendly natural conditions i.e. antibiotic presence. This review highlights the detailed mechanism of RecA mediated SOS response as well as role of RecA-LexA interaction in SOS response. The review also focuses on inter-connection between DNA damage repair pathway (like SOS response) with other survival mechanisms of bacteria such as host mediated RecA induction, persister-SOS interplay, and biofilm-SOS interplay. This understanding of inter-connection of SOS response with different other survival mechanisms will prove beneficial in targeting the SOS response for prevention and development of therapeutics against recalcitrant bacterial infections. The review also covers the significance of RecA as a promising potent therapeutic target for hindering bacterial SOS response in prevailing successful treatments of bacterial infections and enhancing the conventional antibiotic efficiency.

The expression of Escherichia coli SOS genes recA and uvrA is inducible by polyamines

Polyamines are polycationic compounds that have been implicated in a variety of cellular processes. We first report that the expression of recA and uvrA genes in Escherichia coli is inducible by polyamines. The recA and uvrA genes were effectively inducible by spermine (tetra-amine) and less effectively inducible by spermidine (tri-amine). On the other hand, both genes were not significantly inducible by putrescine (diamine) and divalent cation Mg(2+). The expression of both genes was dependent on the charge of the polyamine in the order of spermine (+4), spermidine (+3), and putrescine (+2). The induction of recA and uvrA genes by polyamines showed a dose-dependent relationship and no synergistic effects. Introduction of gyrA mutation conferring DNA relaxation increased the basal expression of recA gene about 2.5-fold compared to the wild type, but did not significantly affect the polyamine-dependent induction ratios of the recA gene. The basal and the polyamine-dependent expression of uvrA gene are not dependent on gyrA mutation. These results suggest that the polyamine-dependent expression of recA and uvrA genes may be regulated in a different way. Our results indicated that polyamines are involved in the SOS induction of recA and uvrA genes at transcriptional levels in E. coli.

Identification of genetic factors altering the SOS induction of DNA damage-inducible yebG gene in Escherichia coli

The yebG gene of Escherichia coli is a novel SOS regulon gene, but details of its regulation mechanism and biological function are not yet known. To characterize the regulation of yebG gene as a SOS gene, we identified the genetic factors affecting the SOS induction of yebG gene using yebG-lacZ operon fusion plasmid. We found that the SOS induction of yebG occurs as the cells enter into the stationary growth phase, but its induction is not observed in LB medium in the presence of 1% glucose. A stationary phase SOS induction of the yebG gene does not require the global regulator of stationary phase-specific genes, rpoS, or gyrA functions, but requires cya encoding the adenylate cyclase and hns encoding the histone-like protein H-NS functions. Our results demonstrated that the induction of a DNA damage-inducible yebG gene of E. coli is dependent on cyclic AMP and H-NS.