Vishnu Udayakumar S, Sankarasubramanian Jagadesan, Sridhar Jayavel, Gunasekaran Paramasamy, Rajendhran Jeyaprakash
Department of Genetics, School of Biological Sciences, Madurai Kamaraj University, Madurai, Tamil Nadu 625021 India.
Indian J Microbiol. 2015 Dec;55(4):384-91. doi: 10.1007/s12088-015-0545-5. Epub 2015 Jul 29.
Brucella is a facultative intracellular bacterium belongs to the class alpha proteobacteria. It causes zoonotic disease brucellosis to wide range of animals. Brucella species are highly conserved in nucleotide level. Here, we employed a comparative genomics approach to examine the role of homologous recombination and positive selection in the evolution of Brucella. For the analysis, we have selected 19 complete genomes from 8 species of Brucella. Among the 1599 core genome predicted, 24 genes were showing signals of recombination but no significant breakpoint was found. The analysis revealed that recombination events are less frequent and the impact of recombination occurred is negligible on the evolution of Brucella. This leads to the view that Brucella is clonally evolved. On other hand, 56 genes (3.5 % of core genome) were showing signals of positive selection. Results suggest that natural selection plays an important role in the evolution of Brucella. Some of the genes that are responsible for the pathogenesis of Brucella were found positively selected, presumably due to their role in avoidance of the host immune system.
布鲁氏菌是一种兼性胞内细菌，属于α-变形菌纲。它会导致多种动物感染人畜共患疾病布鲁氏菌病。布鲁氏菌属在核苷酸水平上高度保守。在此，我们采用比较基因组学方法来研究同源重组和正选择在布鲁氏菌进化中的作用。为进行分析，我们从8种布鲁氏菌中选取了19个完整基因组。在预测的1599个核心基因组中，有24个基因显示出重组信号，但未发现明显的断点。分析表明，重组事件较少发生，且重组对布鲁氏菌进化的影响可忽略不计。这导致一种观点认为布鲁氏菌是通过克隆进化的。另一方面，56个基因（占核心基因组的3.5%）显示出正选择信号。结果表明，自然选择在布鲁氏菌的进化中起着重要作用。一些与布鲁氏菌致病机制相关的基因被发现受到正选择，推测是由于它们在逃避宿主免疫系统方面的作用。
