Characterization、Identification、Bacteriostatic Of Epitope And Surface Molecule Binding Peptide From The SS2、SS7、SS9with Phage Display

Streptococcus suis, which belongs to gram-positive bacterium, is an important infectious pathogen to harm pig industry.In recent years, damages caused by this disease was sharply extending in our country. It not only caused great losses to aquaculture, but also brought serious threat to public health security. Recently,the antibiotic is the mainly way to prevent and treat SS. But due to long-term abuse of antibiotics, the proportion of resistant strains is increasing and the effective prevention and control of the disease is becoming more and more serious. In order to take full control of the disease, it need to identify the isolated bacterias of SS. The streptococcus suis serotypes2,7,9type were served as research objects in this experiment; and their Surface molecules binding peptides were studied by using phage display technology. In order to provide the basis with exploration of new methods of SS classification and identification. The main experiment were as follows:The first experiment screened the same SMBPs of the SS2, SS7and SS9(the same SMBPs between each two serotypes were screened at the same time) by phage display technology. After two rounds of specificity screening, five positive phage clones which came from144phage clones were obtained by phage capture ELISA and bacteria capture ELISA. Those clones corresponded to the common SMBPs of three types which were SS2and SS7, SS2and SS9, SS2and SS7and SS9. From the NCBI, We also found that some of SMBP may be the surface receptor proteins of host cell; some of them may be the enzymes which were secreted from host cell or bacteria itself; some of them may be the surface regulatory factors of host cell; Hence, we deprived SMBP which indicated that the surface molecular of this bacteria may have the interaction with host and can analysis pathogenesis of the disease.The purpose of second experiment was to provide theoretical basis for the development of new drugs to control pig streptococcus disease. Our study Subtraction method together with package-centrifugal-package mode were used to screened the specific SMBP of SS2, SS7and SS9, five positive clones were obtained after screening. Among those clones, two were the specific SMBPs of SS2and an independent peptide VHFAPSPLTMLG was found after sequencing; the specific SMBPs of SS9got three different polypeptide, these SMBPs turned to have a high homology after homology comparison. After verification the specificity of five positive phage clones, the results show their specificity is strong. But no specific SMBPs of SS7was found in our study.The third experiment was to provide theoretical basis for the development of new drugs to control pig streptococcus disease. To screening peptides which inhibit the growth of the SS2,398phage clones were picked to test by ELISA. Seven positive clones which have inhibitory effect on SS2were found and four independent sequence were obtained after sequencing. Comparing the sequence in the NCBI web site by BLAST, we found that those positive peptides have high homology with antibacterial proteins, such as Penicillin binding protein transpeptidase domain-containing, lytic transglycosylase, glycosyl transferase, partial cell wall hydrolase/autolysin, cell division protein FtsK, and so on. These information can help for further research on test results.