Construction and virulence analysis of the SSU0448 gene knockout mutant in Streptococcus suis serotype 2

Abstract:

[Objective] Gene knockout mutant Δ0448 and the functional complementary strain CΔ0448 were constructed to investigate the role of SSU0448 gene on Streptococcus suis serotype 2 (SS2) morphology and virulence. [Methods] Based on the principle of homologous recombination, the SSU0448 gene was knocked out in SS2 virulent strain 05ZYH33. PCR analysis was carried out to identify the mutant, then screened the functional complementary strain CΔ0448 containing the SSU0448 gene expressing plasmid. The morphology and virulence of the established strains were examined. [Results] PCR analysis and DNA sequencing identified the knockout mutant Δ0448 and the SSU0448 gene was completely replaced by the spcr cassette. The functional complementary strain CΔ0448 was also successfully constructed. Gram staining showed that the mutant Δ0448 grew much shorter than the wild type 05ZYH33 and faster to reach the plateau phase. Deletion of the SSU0448 gene did not change the virulence of SS2 in mice infection assays. [Conclusion] Knockout of SSU0448 gene obviously influenced the chain ability of Streptococcus suis serotype 2, and its deficiency has no significant effect on the virulence in the mice model while it may delay the pathogenesis.