Roles of the TonB1 and TonB2 proteins in haemin iron acquisition and virulence in Riemerella anatipestifer

Abstract

Two TonB systems in Riemerella anatipestifer were found and characterized as ExbB1-ExbD1-TonB1 and ExbB2-ExbD2-ExbD29-TonB2, but the significance of two sets of TonB complexes in R. anatipestifer is not clear. In this study, by deleting the tonB1 or tonB2 gene of R. anatipestifer strain CH3, we investigated the roles of the TonB1 and TonB2 proteins in iron acquisition and virulence. The results showed that strain CH3 could utilize haemin as the sole iron source in the presence of L-cysteine, but haemin iron acquisition was defective in the CH3DtonB1 mutant, and the deletion of either tonB1 or tonB2 significantly reduced adhesion to and invasion of Vero cells. Animal experiments indicated that the LD 50 of the CH3DtonB1 and CH3DtonB2 mutants in ducklings was ,224-and ,87-fold, respectively, higher than that of the WT CH3 strain. Additional analysis indicated that blood bacterial loading of ducklings infected with CH3DtonB1 or CH3DtonB2 decreased significantly compared with that found for WT CH3-infected ducklings. Thus, our results indicated that the TonB1, but not TonB2 protein, is involved in haemin iron acquisition and that both TonB proteins are necessary for optimal bacterial virulence.

New Perspectives on Galleria mellonella Larvae as a Host Model Using Riemerella anatipestifer as a Proof of Concept

“…Since it had been demonstrated that R. anatipestifer was able to obtain iron but not a heme source from G. mellonella larva infection, we wondered whether the G. mellonella larva model could be used to evaluate virulence genes related to heme uptake. As a proof of concept, we evaluated the virulence of the tonB1 mutant, tonB2 mutant, and tonB1 tonB2 mutant in the G. mellonella larva model since it has been shown that both tonB1 and tonB2 are involved in heme transport (36) and virulence (37) in ducklings. In the duckling model, consistent with a previous report (37), injection with 10 9 CFU of the tonB1 mutant, tonB2 mutant, and tonB1 tonB2 mutant resulted in no death within 7 days after injection (Fig.…”

“…As a proof of concept, we evaluated the virulence of the tonB1 mutant, tonB2 mutant, and tonB1 tonB2 mutant in the G. mellonella larva model since it has been shown that both tonB1 and tonB2 are involved in heme transport (36) and virulence (37) in ducklings. In the duckling model, consistent with a previous report (37), injection with 10 9 CFU of the tonB1 mutant, tonB2 mutant, and tonB1 tonB2 mutant resulted in no death within 7 days after injection (Fig. S4A); parallel injection with the wild-type strain resulted in a mortality rate of 78% for ducklings 7 days after injection (P Ͻ 0.05) (Fig.…”

First Report of Integrative Conjugative Elements in Riemerella anatipestifer Isolates From Ducks in China

“…R.anatipestifer can infect various types of avian species, such as ducks, geese, turkeys, and some wild birds. R.anatipestifer infection is a contagious disease, that causes enormous economic losses to the poultry industry worldwide (8).…”

Development of a markerless gene deletion strategy using rpsL as a counterselectable marker and characterization of the function of RA0C_1534 in Riemerella anatipestifer ATCC11845 using this strategy

“…Currently, OmpA [10]; TonB, which is involved in heme transportation [11–13]; the TonB-dependent receptors B739_1208 and B739_1343 [14, 15]; the wza -like gene, which is involved in capsule biosynthesis [16]; and AS87_04050, M949_1556 and M949_RS01915, which are involved in lipopolysaccharide biosynthesis [17–19] have been identified as potential virulence factors. In these studies, the functions of these genes were identified via gene deletion using an antibiotic cassette for replacement.…”