Construction And Biological Characteristics Analysis Of LppB And Lpp/lppB Mutants In Aeromonas Veronii JC529

Aeromonas veronii(A.veronii)is an important zoonotic pathogen belonging to the genus Aeromonas.A.veronii is ubiquitous in the natural environment with a broad host spectrum and significant pathogenicity,capable of infecting fish,amphibians and mammals including humans,poses a serious threat to the sustainability of aquaculture and to human health.In recent years,people have carried out a lot of research on the known virulence factors of A.veronii,while the research on new virulence factors is rarely reported.Therefore,further exploration of new virulence factors will help to reveal the pathogenicity of A.veronii mechanism.Bacterial lipoprotein(LPP),as an important virulence factor,is involved in a variety of pathogenic mechanisms such as bacterial colonization,invasion,evasion of host defense,and immune regulation.In this project,A.veronii JC529 was taken as the research object.Based on the results of the previous whole gene sequencing analysis of the research group and the successful construction of the lipoprotein Lpp deletion strain ?Lpp,the homologous recombination method was used to delete the lipoprotein Lpp B,thereby successfully constructing a Lpp B single deletion strain?Lpp B,and Lpp,Lpp B double gene deletion strain ?Lpp/Lpp B,and then successfully constructed complementary strains through gene complementation.The genetic stability of the above successfully constructed strains was tested,and the results showed good results,and then related biological characteristics of the deletion strain,complementary strain and wild strain were analyzed.The analysis results showed that compared with JC529,?Lpp/Lpp B and ?Lpp B had no significant change in colony morphology and growth,no difference in hemolytic activity,decreased biofilm formation ability,weakened swimming ability,partial shedding of flagella,decreased cell adhesion ability,and reduced pathogenicity in mice.Compared with ?Lpp B,?Lpp/Lpp B had lower biofilm formation ability,obvious flagella shedding,reduced cell adhesion ability,and weakened pathogenicity to mice.The biofilm-forming ability,swimming ability and flagellum number of c-LPPB and C-LPP /Lpp B were partially recovered,but not to the original level.The virulence of C-LPPB to mice returned to the original level,but c-LPP /Lpp B did not recover.In summary,through the comparative analysis of the changes in biological characteristics among the successfully constructed deletion strains,complementary strains and wild strains,it is speculated that the lipoproteins encoded by Lpp B and Lpp may be closely related to the pathogenicity of A.veronii JC529.The results of this research will lay the foundation for the subsequent research on the virulence factors of A.veronii,which is beneficial to the further research on the pathogenic mechanism of A.veronii.