Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA.
Infect Genet Evol. 2012 Mar;12(2):274-7. doi: 10.1016/j.meegid.2011.11.004. Epub 2011 Dec 3.
Rates of nonsynonymous substitution (dN) significantly higher than rates of synonymous substitution (dS) have been used as evidence of positive selection for the fixation of advantageous point mutations. It has been suggested that positive selection contributes to the evolution of virulence factors and certain functional categories in bacterial pathogens. The genus Streptococcus contains a number of important human and agricultural pathogens. Here we assessed positive selection across 13 Streptococcus species, and their relationship with virulence factors and functional categories. We found that known virulence genes were subject to positive selection pressure as much as other genes. After false discovery rate correction for multiple comparisons, no functional categories were significantly over- or under-represented in positively selected genes relative to other genes. Our results suggest that within the genus Streptococcus positive selection based on dN/dS ratios is not distributed with bias across biological functions.
非同义替换率（dN）明显高于同义替换率（dS），这被用作有利点突变固定的正选择证据。有人认为，正选择有助于细菌病原体毒力因子和某些功能类别的进化。链球菌属包含许多重要的人类和农业病原体。在这里，我们评估了 13 种链球菌种的正选择，并研究了它们与毒力因子和功能类别的关系。我们发现，已知的毒力基因与其他基因一样受到正选择压力的影响。在对多次比较进行错误发现率校正后，相对于其他基因，没有功能类别在正选择基因中显著过多或过少。我们的研究结果表明，在链球菌属中，基于 dN/dS 比值的正选择在生物学功能上没有偏向性分布。
