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　　法英等國研究人員近日在新一期《自然遺傳學》雜志網絡版上報告說，他們探明了引起結核病的結核分枝桿菌的起源，這一成果有助于開發防止結核病的新方法。

　　結核分枝桿菌是引起結核病的元兇，雖然還有一些種類的分枝桿菌也可能使人患上結核病，但結核分枝桿菌是其中傳播最廣泛、致病能力最強的病菌。

　　法國巴斯德研究所領導的研究小組對不同分枝桿菌的基因組進行分析比較后發現，結核分枝桿菌與卡式分枝桿菌的基因組總體結構極為相似，應該是由同一古老菌種進化而來。

　　此外，研究人員還發現了結核分枝桿菌進化出較強傳染性與致病性的若干基因機制。研究人員認為這些發現有助于研發防止結核病的新方法，幫助醫衛部門實現控制結核病的目標。

　　結核病是世界上傳播最廣泛的疾病之一，影響到世界上三分之一的人口。據世界衛生組織統計，2011年約有140萬人死于結核病。

　　Genomic analysis of smooth tubercle bacilli provides insights into ancestry and pathoadaptation of Mycobacterium tuberculosis

　　ABSTRACT

　　Global spread and limited genetic variation are hallmarks of M. tuberculosis, the agent of human tuberculosis. In contrast, Mycobacterium canettii and related tubercle bacilli that also cause human tuberculosis and exhibit unusual smooth colony morphology are restricted to East Africa. Here, we sequenced and analyzed the whole genomes of five representative strains of smooth tubercle bacilli (STB) using Sanger (4–5× coverage), 454/Roche (13–18× coverage) and/or Illumina DNA sequencing (45–105× coverage). We show that STB isolates are highly recombinogenic and evolutionarily early branching, with larger genome sizes, higher rates of genetic variation, fewer molecular scars and distinct CRISPR-Cas systems relative to M. tuberculosis. Despite the differences, all tuberculosis-causing mycobacteria share a highly conserved core genome. Mouse infection experiments showed that STB strains are less persistent and virulent than M. tuberculosis. We conclude that M. tuberculosis emerged from an ancestral STB-like pool of mycobacteria by gain of persistence and virulence mechanisms, and we provide insights into the molecular events involved.