Construction And Characterization Of Cada And Cadb Deleted Mutant In Aeromonas Veronii TH0426

As a newly emerging human,animal and aquatic organism co-occurring pathogenic bacteria,Aeromonas veronii has received extensive attention in the medical and scientific communities.By analyzing the results of epidemiological surveys in recent years,it can be found that the virulence of A.veronii and its tolerance to drugs are increasing year by year,which makes more and more countries aware of the hazards of the pathogen and listed it as an important indicator of water quality testing.At present,most studies on A.veronii have focused on isolation and identification and drug susceptibility testing,and relatively few studies on its virulence factors and pathogenic mechanisms have limited the research progress on this pathogen.At the same time,more and more researchers have realized the importance of virulence factors research.Based on the previous research results of this subject,our study have screened the highly expressed protein-cadaverine reverse transporter cadB in the A.veronii.virulent strain TH0426,in the comparative analysis of the coding gene of cadB,we found that the lysine decarboxylase present in A.veronii is highly related to cadB;Furthermore,we used a highly efficient suicide plasmid-mediated homologous recombination method to delete the two coding gene cadA and cadB in A.veronii TH0426 to constructing the cadA and cadB gene deletion mutants of A.veronii TH0426.By detecting the biological characteristics of the missing strains,complementing strains and wild strains,we found that,compared to wild-type strains,the pathogenicity to zebrafish and the cytotoxicity to EPC of ? cadA deletion strain had decreased 33.1-fold and 4.1-fold,respectively,while the biofilm formation ability increased 1.6-fold;the pathogenicity to zebrafish and the cytotoxicity to EPC of ? cadB deletion strain had decreased 93.2-fold and 9.5-fold,respectively,while the biofilm formation ability increased 5.6-fold.The results showed that the virulence of A.veronii TH0426 was significantly decreased after the deletion of cadA and cadB genes,which is consistent with the expected results previously.In summary,this study established the deletion mutants strains of cadA and cadB genes,and compared the differences in biological characteristics between deletion mutants strains and wild-type strains.and explore the possible causes of changes in biological properties;Thus we predict that the cadherin decarboxylase and cadaverine reverse transporters encoded by cadA and cadB genes may closely related to the pathogenicity of A.veronii TH0426,and the results can provide a theoretical basis for the further research on A.veronii virulence factors.