Functional identification of B739_RS03695 in Riemerella anatipestifer CH-1

Abstract:

[Background] Riemerella anatipestifer (RA) is a Gram-negative bacterium that causes infectious serositis in ducks. Despite the extensive studies about the iron transport system of this bacterium, little is known about the function of iron-sulfur cluster assembly gene. [Objective] Sequence analysis shows that B739_RS03695 encodes an iron sulfur binding protein in R. anatipestifer CH-1, while the function of this gene remains unknown. This study aims to reveal the role of gene B739_RS03695 in the strain resistance to oxidative stress and antibiotics. [Methods] We constructed the B739_RS03695-deleted strain and studied its response to oxidative stress by establishing the growth curve and conducting the oxidative stress assay. The role of the gene in antibiotic resistance was measured by the minimum inhibitory concentration (MIC) and time-dependent killing experiment. [Results] Compared with the parent strain, RA CH-1ΔB739_RS03695 presented unaffected growth in the GCB medium, inhibited growth in the iron-restricted medium, increased sensitivity to H₂O₂, and enhanced resistance to gentamicin. The real-time PCR results showed that compared with the control group, the transcription level of B739_RS03695 was significantly up-regulated under iron restriction and hydrogen peroxide stress conditions. [Conclusion] The deletion of B739_RS03695 impaired the growth of RA CH-1 in iron-restricted medium. B739_RS03695 was required for the resistance of RA CH-1 to H₂O₂ and the killing effect of gentamicin on RA CH-1.