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目的分析2型猪链球菌89K致病岛的结构特征,探索其进化历程。方法通过BLAST比对,获取89K致病岛的同源序列,构建其同源序列数据库;分析89K致病岛的碱基组成特征,寻找重组热点区域,并对89K进行分区;对各ORF进行功能预测,划分功能模块;对89K致病岛与其同源序列进行系统发育分析及共线性分析,推测其可能的进化历程。结果 89K致病岛可分为4个保守区,4个主要的非保守区及一段Tn916转座子,呈现多个异源序列相嵌合的结构特征。功能分析发现保守区基因主要参与致病岛的横向转移及其在宿主菌基因组中的稳定,保守区的基因呈现出进化上的一致性,且在某些菌株中保守区以连续状态存在。结论保守区在祖先状态时是一个连续整体,不同来源的非保守区经过多次水平转移和重组事件插入到保守区之间,形成了89K致病岛的嵌合结构。
Objective To analyze the structural characteristics of 89K pathogenicity island of Streptococcus suis type 2 and to explore its evolutionary history. Methods The homologous sequences of 89K pathogenicity island were obtained by BLAST alignment, and their homology sequence databases were constructed. The base composition characteristics of 89K pathogenicity island were analyzed to find the recombination hotspot region, and the 89K was partitioned. The function of each ORF Predict and classify functional modules. Phylogenetic analysis and collinearity analysis of the 89K pathogenic island and its homologous sequences were carried out to speculate the possible evolutionary process. Results The 89K pathogenicity island could be divided into four conserved regions, four major non-conserved regions and a Tn916 transposon, showing the structural features of multiple heterologous sequences. Functional analysis found that the conserved region genes are mainly involved in the lateral metastasis of pathogenic island and its stability in the host bacterial genome. The genes of the conserved regions show evolutionary consistency, and in some strains, the conserved regions exist in a continuous manner. Conclusions The conserved regions are a continuous whole in the ancestral state. The non-conserved regions of different origins are inserted into the conserved regions through multiple horizontal transplants and recombination events, forming the chimeric structure of the 89K pathogenic island.