The Screening Of STSLS Related Streptococcus Suis Transcription Factors,and Its Regulatory Mechanism

Streptococcus suis?S.suis?is an important pathogeny to cause zoonotic disease.It is mainly distributed in Asia and Europe,and sometimes were repoted in another continent.The bacterium currently has 29 serotypes in serum type,in which the S.suis serotype 2?SS2?were reported as the mainly serotype associated with diseases in pigs and human worldwide.Since it's been reported,S.suis has infected thousands of people across the globe,leaving survivors with multiple sequelae.It is also the main bacterial pathogen causing meningitis in Southeast Asia,which poses a great threat to human public health.What's more,there have been two outbreaks in SS2 in China,with extremely high mortality and accompanying streptococcus toxic shock like syndrome?STSLS?that have attracted worldwide attention.Duiring the process of pathogen invading the host,its virulence factor can change with the change of environment,and It all depends on transcription factors.In this study,we screen one of the transcription factors in 89 K which related to STSLS,and studied its regulation mechanism.The main results are as follows: 1.Screened a transcription factor that affects streptococcus suir to cause STSLS With inducing the bacteria in vivo,we found that most of the eight transcriptional factors in the candidate were raised.Each one was knoco-out and confirmed in mice,and found that the absence of one of the transcription factors called tstS reduced the pathogenicity of SS2 significantly.As it is on the 89 K PAI,we examined knock-out strain ability to stimulation the on the inflammatory cytokines of mouse macrophages,and found it's significantly dropped.The number of bacteria in the blood of mice and the content of inflammatory factors in serum were confirmed,without tstS the strain was easy to be clear by immune system and can't stimulate high level of cytokines.However,duiring the early infection period,the mutant can lead to high inflammatory and be cleared soon.We use the European standard strain P1/7 as the parent strain which does not contain the tstS to construct the overexpression strain.The results show that with tstS the P1/7 strain also has the ability to inspire high level of inflammatory cytokines.The results showed that the presence of tstS could improve the ability of the bacterial strain to infect the acute stage of infection,which plays an important role in STSLS.2.Discover the regulatory mechanism of tstS affecting SS2 To study the mechanism of tstS impact on SS2 to STSLS,we screened the differential genes between the mutant strains and wild strains with gene chips.Through GO analysis,we found most of the differential genes were contributed to metabolism.In addition,Sspep,Fhb,Fhbp,SSU05₂103 which have been confirmed as the surface virulence factors of Streptococcus suis were found in it.We imitated the difference environment of culture,the expression of tstS were up-regulated when glucose is scarce.With the help of EMSA,we confirmed the tstS were regulated by CcpA.Combined with previous research in our laboratory,we hypothesized that there is a certain relationship between TstS,Fhbp and Ccp A.The Ccp A binding sequence of tstS promoter was inserted into the Fhbp promoter region of tstS knock-out strain.We found its ability to uptake the glucose was restored and its pathogenicity were increased.Therefore,we confirm that TstS has feedback regulation with Ccp A through Fhbp.This is also the new mechanism of Ccp A regulation,which provides a new insight for understanding the ingenuity regulation of CcpA.