Study On The Metal-dependent Transcription Regulator (mtsR) In Streptococcus Suis

Streptococus suis is a gram-positive coccus that has been implicated as the cause agent of many forms of swine infection and was also recognized as a zoonotic agent causing human disease.35different serotypes of S. suis have been described based on this bacterium's polysaccharide capsular antigen. Of these, S.suis serotype2(SS2) has been shown to be the serotype most frequently involved in infectious diseases caused by S. suis. Outbreaks of S.suis serotype2in humans were reported in Jiangsu and Sichuan Provinces of China in1998and2005, and hundreds of people were infected with high mortality due to toxic shock syndrome and meningitis. SS2infection has become the focus of public health epidemic prevention.To date, molecular machineries of SS2pathogenicity have been partially disclosed. However, there are many questions on the pathogenesis of the infection need to answer. For example, how does S.suis2uptake the essential nutrients, such as iron? Also, the transport-regulate systems for the acquisition of iron employed by S.suis2was unknown.In this Master Degree Thesis we report the following research results:The isolated strains were obtained from diseased pigs with septicemia in sichuan Province in summer2010. The morphological observation, Gram stain indicated that the isolated bacteria belonged to genus Streptococcus and indentified to be above99%of homology to05ZYH33(streptococcus suis type2,SS2) using16S rDNA gene sequence analysis. Seven virulence factors were detected by PCR amplification, namely CPS, MRP, EF, Sly, GDH, FBPS and ORF2. The result showed the distribution of virulent factors of the isolated strain was basically same with the other S.suis2strain isolated from other area of China, the isolated strain SS86was not grown in THYB medium with250μM Dipyridyl(DPD), a metal chelator with high specificity for iron.1.5μM of Fe2+,1.OμM of Fe3+and30μM of hemoglobin was add to media contained1OOμM of DPD, respectively, growth of SS86was restored. The results showed that iron is required for colonization and survival of S.suis2. To investigate the mechanisms involved in absorbing and regulating iron of S.suis2in future, we constructing the deletion mtsR(a metal-dependent regulator) mutants in Streptococus suis SS86with a thermosensitive delivery vector system pJR700by electroperation method. RT-PCR was used to determine whether the metal-dependent regulator mtsR regulated the expression of the Streptococcal metal binding genes (fhuA, feoA,mutA,mtsA) of metal acquisition operons of Fhu,Feo,Mut and Mts and the regulator fur. The production by the mtsR mutant was compared to that by the wild-type strain in THYB medium. The results showed that the wild strain and the mtsR mutant has difference in the experssion of iron acquisition operon and regulator fur. This result demonstrated that regulator mtsR of S.suis influenced the experssion of iron acquisition operon and regulator.