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Genetic Diversity Study on Virulence Markers of Streptococcus Suis

Author: ZhuWeiFeng
Tutor: JinMeiLin
School: Huazhong Agricultural University
Course: Preventive Veterinary Medicine
Keywords: Streptococcus suis Virulence-associated factor Gene polymorphism Selection pressure Recombinant Horizontal transfer Niche
CLC: S852.611
Type: Master's thesis
Year: 2011
Downloads: 42
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Abstract


Streptococcus suis is a worldwide bacterial pathogens that endanger the pig industry. Streptococcus suis is an important man and beast comorbid infectious pathogen. In many countries of the world are dominant serotype serotype 2. Virulence factor is often used as a protein virulence indicates three: lysozyme released protein (MRP), extracellular protein factor (EF) and hemolysin (SLY). Although previous research has made us a deeper understanding of the Streptococcus suis, but these studies did not allow us to find an effective strategy for the prevention and control of Streptococcus suis. So we are ready through the study of a new perspective, that is, MRP, EF and SLY gene polymorphism, and then through these specific examples of research to examine the characteristics of the pan-genome of Streptococcus suis, Streptococcus suis ecological characteristics and evolutionary biology learn on the characteristics of the final expedition of Streptococcus suis research and prevention and control strategies. First virulence strains of Streptococcus suis type 2 instructions protein gene polymorphism. Let serotype 2 strain 180 pigs MRP, EF, the SLY corresponding chromosomal region sequencing and then describe the link between genotype and pathogenicity also detect a host for the three virulence instructions protein genes withstand the selection pressure. Found that some strains mrp and epf is lost in the form of performance. In these strains from three major genotypes of these proteins, although the genotype of the MRP have multiple, but SLY EF genotype can be considered only two: SLY EPF (sometimes sly epf *) and sly0epf0. These genotypes also echoes with the virulence and phylogenetic relationships of the isolates. After the detection of three virulence factor genes do not exist significant positive selection pressure. Compared to conventional PCR methods virulence instructions protein gene locus sequencing allows us to get more information on Streptococcus suis, especially information about the gene polymorphism of Streptococcus suis and Streptococcus suis and host interactions information. Next, we further studied in 50 different strains of Streptococcus suis serotype virulence instructions protein gene polymorphism. We found that the the MRP gene corresponding chromosomal sequence can be divided into 12 categories, the the EF gene corresponding chromosomal sequence can be divided into seven categories. Gene distribution and structural analysis of these gene variant is Streptococcus suis integrate exogenous genes results. We also found that the insert sequence and polyG, Streptococcus suis gene exchange ruins. Streptococcus suis different genotypes in Streptococcus suis phylogenetic distribution of tree with branches of the phylogenetic tree echoes turn the pig the streptococcal population can be divided into four groups. The findings also confirmed that in 90 clinical isolates of these groups and strains of the source of a significant correlation. This suggests mrp and epf different variants with Streptococcus suis different ecological phase contact. Taken together, our data suggest this conclusion can be drawn, heterogeneity is an important feature of the Streptococcus suis genome, the presence of genetic variants leading mrp and epf important reason we can not be detected in some strains. These gene variants are the result of integration of exogenous gene in Streptococcus suis, its integration mechanism may be diverse. The Streptococcus suis Get gene variant is not casual, but influenced by Streptococcus suis niche. Through these two specific studies we can find the Streptococcus suis pan genome having the general characteristics of the bacteria Pan genome, also found that the same gene may also have different variants, these variants are mainly Streptococcus suis integrate a result of the exogenous gene, and the mechanism may be varied, which increases the difficulty of the prevention and control of Streptococcus suis infection. But our research shows that the distribution of these gene variants is closely related contact with Streptococcus suis system development, in close contact with Streptococcus suis niche, so we recommend that after the Streptococcus suis population is divided into a systemic infection type the symbiosis type three ecotypes pneumonic and partial Lee were studied, and this will reduce the interference of Streptococcus suis genome heterogeneity. Our data also suggest the pathogenicity of Streptococcus suis may be shared by a variety of factors mediated decided, based on the general characteristics of the bacterial pan-genome - the adaptive key genes located in the the specialized subsidiary genome genome, we recommend determining the the containing genes the Streptococcus suis Laid genome, and then based on these genes to find these genes as the key point of the gene interaction network, and finally according to these interaction network to develop a final strategy to eliminate the hazard of Streptococcus suis.

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CLC: > Agricultural Sciences > Livestock, animal medicine,hunting,silkworm,bee > Animal Medicine ( Veterinary Medicine) > Basic Veterinary Science > Animal Microbiology ( Veterinary Microbiology, ) > Pathogenic bacteria > Cocci
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