Construction and virulence evaluation of the virB1-89K gene knockout mutant of type IV-like secretion system of Streptococcus suis serotype 2

Abstract:

Abstract:［Objective］To construct the virB1-89K gene knockout mutant and its complementary strain of Streptococcus suis serotype 2 (SS2) highly virulent strain 05ZYH33 and evaluate the role of virB1-89K in the pathogenesis of SS2.［Methods］The virB1-89K gene was knocked out by homologous recombination，then multiple-PCR and sequence analysis were used to identify the knockout strain ΔvirB1-89K．The virB1-89K gene and its upstream promoter were cloned into the E．coli-S．suis shuttle vector pSET1，and the recombinant plasmid was electrotransformed into the ΔvirB1-89K mutant to generate the complementary strain CvirB1-89K．The effects of virB1-89K deletion on the basic biological characteristics and virulence of SS2 were then determined in this study．［Results］The isogenic mutant ΔvirB1-89K and its complementary strain CvirB1-89K were successfully constructed． No significant differences in biological characteristics were found among the three strains． However，the virulence of the ΔvirB1-89K mutant was reduced to 30% of the wildtype level and functional complementation of virB1-89K restored its pathogenicity．[Conclusion] The virB1-89K gene plays an important role in the pathogenesis of S．suis 2 infection．