| Streptococcus suis is an important pathogen which has been associated with a wide variety of infections in swine, such as meningitis, septicemia, arthritis, and pneumonia. This organism has also been isolated from humans with meningitis or endocarditis. There are currently 35 serotypes (type 1/2 and 1 through 34) of S. suis, among which type 2 is the most popular and pathogenic. S. suis type 2 produce virulence factors as capsular polysaccharide, muramidase-released cell-wall protein, extracellular protein factor, suilysin and glutamate dehydrogenase, etc. But virulence factors of S. suis type 2 are not well characterized. However, not all strains of S.sui type 2 are virulent, and there is variation in the virulence of those strains that are virulent.Compared proteome analysis has been successfully used to identify new virulence factors and reveal the pathogenic mechanism of pathogenic bacteria by numerous groups. But there were no reports about the proteomic analysis of S.suis type 2.The ability of pathogenic bacteria to cause disease in a susceptible host is determined by multiple factors acting individually or together at different stages of infection. The secretion of virulence factors is a common feature of many pathogenic bacteria, and thus it is important to generate extracellular proteomes to facilitate studies of bacterial pathogenesis. The DNA sequences of S. suis type 2 genomes were sequenced. Therefore, it is ideal organism for proteomic analysis.For this study, we used a proteomic approach to analyze and compare the extracellular proteomes (ECPs) of virulent and avirulent S. suis type 2 in order to give an integrated view of ECPs of virulent and avirulent S. suis type 2. A comparative proteomic analysis among the avirulent S. suis type 2 strain and the virulent S. suis type 2 strain revealed different proteins that are produced by the virulent S. suis type 2 strain. These proteomes are useful references for comparative analysis, laboratory diagnosis, and further molecular and functional studies, which will lead to a better understanding of S. suis type 2 pathogenesis.We use protein-free culture to culture S. suis type 2, an efficient recovery method for extracellular proteins at first, and two-dimensional gel electrophoresis followed by peptide mass fingerprinting for protein separation and identification. This study optimized some methods of 2-DE, namely, selecting the best application of sample method and and suitable quality of sample, building clear and high-resolution composite 2-DE map and picking out the staining method which is compatible with further PMF analysis, with less background staining and high sensitivity.We compared the 2-DE map of virulent and avirulent S. suis type 2. Good reproducibility and high comparability was achieved within three independent experiments. About 180±10 spots were detected both in the virulent and avirulent S. suis type 2 by Image Master6.01 software after manual correction. Correlation analysis was done using the %vol of matched spots from the two groups, which is a useful function offered by the software. We also found that there were about 50 protein spots exist in avirulent strain and out of the virulent strain and there were about 52 protein spots exist in virulent strain and out of the avirulent strain. We cut out 10 bad-matched spots after analysis by auto matching and manual correction. The ten protein spots have been idendified by MALDI-TOF-MS and/or MALDI-TOF/TOF- MS as six proteins definitely, they are dehydrogenase with different specificities (related to short-chain alcohol dehydrogenase), fructose/tagatose bisphosphate aldolase, L-lactate dehydrogenase, 3-oxoacyl- (acyl-carrier- protein) synthase,β-ketoacyl synthase and the homologous protein of flagellin.Among the protein spots of identified, there were five decomposition/anabolic effect enzymes and there was one homologous protein of flagellin .Whether these different proteins are related to pathogenicity of S.suis type 2 need further confirmation by molecular biology analysis. |
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