Function Researches For VirB9 Of P.mirabilis

On the preliminary researches,our group firstly discovered Proteus mirabilis(P.mirabilis)C02011 strain obtained T4 SS with strong diarrhea-causing ability.It is similar to VirB of type IV secretion system(T4SS)of Escherichia coli and Klebsiella pneumoniae.According to foreign and domestic reports,we described VirB9 gene as the channel subunit of T4 SS.It is worth mentioning that VirB9 is vital to the pathogenicity of P.mirabilis.So,following our studies,we will pay our attention on the researches of VirB9,which is located on T4 SS pathogenic island.So,we constructed VirB9 knockout strain and its retro-compensation strain of P.mirabilis C02011.By the below experimental results,we explored the function of VirB9 virulence factor for the bacteria C02011.In vitro experiments: we firstly selected three common intestinal cell lines(Caco-2,Lovo,HT-29)for the adhesion and invasion experiments of P.mirabilis C02011,and we had got the most sensitive cell model of Caco-2 with the best multiplicity of infection(MOI)value and infectious duration.Next,we compared morphological and physiological features between wild strain and mutant strain by use of gram staining,growth curve comparison and so on.Finally,with the help of the above cell model,we can easily get the distinction between different strains(T4SS,no T4 SS,?VirB9 and its retro-compensation and so on).In vivo experiments: by comparison among the three groups(C02011 with containing T4SS),B02005 without containing T4 SS and normal saline control),using fecal water content,colon length,pathological section and score as evaluation index,we constructed successfully sensitive Balb/c mice model of P.mirabilis diarrhea.Then,we used the diarrhea animal model for P.mirabilis C02011,?VirB9/C02011 and retro-compensation ?Vir B9/C02011 to carry out a preliminary research on level of inflammatory factors,our results were in line with our expectations(C02011>retro-compensation ?VirB9/C02011>?VirB9/C02011).Through the results of above experiments,we confirmed T4 SS pathogenicity Island had the function of enhancing the virulence of P.mirabilis,and the VirB9 gene in the T4 SS played a key role on the T4 SS function.