Study On The Function Of SSU0448 Gene In N - Acetylgalactosamine And Galactosamine Metabolic Pathway Of Streptococcus Suis Type

Streptococcus suis, regarded as an critical infectious disease agent in the swine industry, could be classified into 35 serotypes according to the differentiation of capsule antigen. Generally, Streptococcus suis serotype 2 (SS2) is considered to be the most virulent, often most frequently isolated from the clinically-diseased piglets and most spread worldwide. The clinical features caused by SS2 could be characterized with meningitis, endocarditis, septicemia, pneumonia and even death Notably, the clinical symptoms of two outbreaks are characterized with high infection rates, deep tissue infection, and especially the streptococcus toxic shock syndrome (STSS), which have never been reported. The sporadic human infection of SS2 happens worldwide while the mechanism of pathogenic ity needs to be clarified.According to the bioinformatics analysis, we predicted that the SSU0448 gene was the transcriptional regulation factor of the GalNAc/GalN pathway. Basing on the principle of homologous recombination, the gene knockout mutant △ 0448 of the highly pathogenic wild type 05ZYH33 was successfully constructed and screened. Then,The basic biological characteristics of mutant △ 0448、the wild type 05ZYH33 and the complementary strain C △ 0448 were conpared, and the changes of mRNA expression level associated with the GalNAc/GalN pathway; meanwhile, the mice were infected with these strains to evaluate the virulence. Gram staining showed that the mutant △ 0448 grow much shorter chains than that of the wild type 05ZYH33, interestingly the mutant △ 0448 growed faster to reach the stationary phase while no obvious differences have been found among other morphological examinations. Unfortunately, deletion of the SSU0448 gene in SS2 did not obviously lower the virulence in the mice infection assays, while it might delay the proceeding of patho genes is.Generally, basing on the present results, we suggest that the deficiency of SSU0448 gene obviously influence the length of the chain, while no significant changes in morphology of Streptococcus suis serotype 2; we observed that the mutant △　0448 has no significant effect of virulence comparing to 05ZYH33 strain in the mice infection model while it might delay the proceeding of patho genes is. Our study provides foundametal knowledge for the mechanism of SS2 patho genesis.