RecA protein mediates fitness, virulence and DNA damage response (SOS response) in Riemerella anatipestifer

Abstract

Background: DNA damage response (SOS response) refers to an important protective mechanism for bacteria to cope with genomic DNA damage. The RecA protein plays a key regulatory role in the induction of SOS responses in many bacteria, and its homologous proteins are widely present in various organisms. However, the biological functions of RecA protein of Riemerella anatipestifer have never been explored.In this work, we constructed the deletion strain RA-GDΔRecA and complemented strain RA-GD△RecA pCPRA::RecA, and the growth ability, drug sensitivity, virulence and SOS response of the parental RA-GD, RA-GDΔRecA and RA-GD△RecA pCPRA::RecA strains were detected. Results: The results showed that the RecA protein reduced the fitness of RA-GD strain, and decreased the resistance of cells to three antibiotics (tetracycline, oxytetracycline and gentamicin sulfate) and the virulence of the strain to ducklings. Within a certain range of ultraviolet irradiation (UV), the transcription level of RecA gene increased significantly with the prolongation of UV time. Furthermore, the deletion of RecA gene reduced significantly the integrity of genomic DNA of RA-GD, indicating that the RecA gene may play a positive regulate role in the SOS response of R. anatipestifer. However, Western blotting showed that the levels of RecA protein in parent strain had no significant change under the condition of UV treatment. Conclusion: This experiment demonstrated for the first time that RecA gene participated in the fitness, resistance, virulence and DNA SOS response in R. anatipestifer.