Preliminary Study On Iron Acquisition System Of Duck Riemerella Anatipestifer

Riemerella anatipestifer disease is caused by Riemerella anatipestifer?RA?and is more common in meat ducks.Pathological changes in fibrinous pericarditis,hepatic pericarditis,and airsacculitis are presently occurring.One of the most dangerous bacterial diseases.Studies have shown that the iron acquisition system of bacteria plays an important role in the infected host and pathogenic process.The study was conducted in order to understand the iron acquisition system of R.anatipestifer.In this study,2-2'-dipyridyl?DIP?was used to chelate iron in TSB medium.The growth of R.anatipestifer strains in the iron-limited TSB medium supplemented with different concentrations of FeSO4 and FeCl3 as exogenous iron was compared.The results showed that the concentration of DIP which could completely inhibited bacterial growth was 100?M for strains HXb₂ and NJ-1,150?M for strain Th₄,200?M for strain Yb₂,250?M for strain SX,and 300?M for strain CH₃.When 200?M FeCl₃ and FeSO₄ were added into the iron-limited TSB medium as exogenous iron,except for the slow growth of HXb₂ and NJ-1strains,the other four strains grew faster.In addition,all tested strains were found to grow faster when FeSO₄ as exogenous iron than that FeCl₃ as exogenous iron.The level of secreted siderophore of strains HXb₂,CH₃ and Yb₂ was measured bymodified CAS method.Eight RA strains were found to produced orange transparent halos secret siderophore on CAS solid plates.However the ability of each strain to synthesize siderophore was different.In order to further study the iron acquisition genes of R.anatipestifer,the total RNA of strains CH3 and HXb2 in TSB and TSB+DIP?iron-limited?were extracted with kit for transcriptomic sequencing analysis.The results showed that there were significant changes in the expression of 31 genes in the CH₃ strain,of which 8 genes were significantly down-regulated and 23 genes were up-regulated.However,there were significant changes in the expression of 15 genes in the HXb₂ strain,of which 3 genes were significantly down-regulated and 12 genes were up-regulated.By comparison,it was found that the genes of CH3 and HXb2 strains were up-regulated or down-regulated during iron-limited culture were different.In summary,in this experiment,the addition of exogenous iron?FeSO4 and FeCl3?in theiron-limited TSB medium promoted the growth of different strains.The modified CAS method using the siderophore of R.anatipestifer detected different levels of siderophore and the test results were very intuitive.The culture of TSB and iron-limited TSB had an effects on the expression of genes of CH3 and HXb2 strains,which laid the foundation for studying the iron acquisition system and molecular pathogenic mechanisms of R.anatipestifer.