法英等国研究人员近日在新一期《自然遗传学》杂志网络版上报告说，他们探明了引起结核病的结核分枝杆菌的起源，这一成果有助于开发防止结核病的新方法。

　　结核分枝杆菌是引起结核病的元凶，虽然还有一些种类的分枝杆菌也可能使人患上结核病，但结核分枝杆菌是其中传播最广泛、致病能力最强的病菌。

　　法国巴斯德研究所领导的研究小组对不同分枝杆菌的基因组进行分析比较后发现，结核分枝杆菌与卡式分枝杆菌的基因组总体结构极为相似，应该是由同一古老菌种进化而来。

　　此外，研究人员还发现了结核分枝杆菌进化出较强传染性与致病性的若干基因机制。研究人员认为这些发现有助于研发防止结核病的新方法，帮助医卫部门实现控制结核病的目标。

　　结核病是世界上传播最广泛的疾病之一，影响到世界上三分之一的人口。据世界卫生组织统计，2011年约有140万人死于结核病。

　　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.