Gutierrez M Cristina, Brisse Sylvain, Brosch Roland, Fabre Michel, Omaïs Bahia, Marmiesse Magali, Supply Philip, Vincent Veronique
Laboratoire de Référence des Mycobactéries, Institut Pasteur, Paris, France.
PLoS Pathog. 2005 Sep;1(1):e5. doi: 10.1371/journal.ppat.0010005. Epub 2005 Aug 19.
The highly successful human pathogen Mycobacterium tuberculosis has an extremely low level of genetic variation, which suggests that the entire population resulted from clonal expansion following an evolutionary bottleneck around 35,000 y ago. Here, we show that this population constitutes just the visible tip of a much broader progenitor species, whose extant representatives are human isolates of tubercle bacilli from East Africa. In these isolates, we detected incongruence among gene phylogenies as well as mosaic gene sequences, whose individual elements are retrieved in classical M. tuberculosis. Therefore, despite its apparent homogeneity, the M. tuberculosis genome appears to be a composite assembly resulting from horizontal gene transfer events predating clonal expansion. The amount of synonymous nucleotide variation in housekeeping genes suggests that tubercle bacilli were contemporaneous with early hominids in East Africa, and have thus been coevolving with their human host much longer than previously thought. These results open novel perspectives for unraveling the molecular bases of M. tuberculosis evolutionary success.
极具致病性的人类病原菌结核分枝杆菌的遗传变异水平极低，这表明其整个种群是约35000年前经历进化瓶颈后通过克隆扩增产生的。在此，我们表明该种群仅仅是一个更为广泛的祖系物种中可见的一小部分，其现存代表是来自东非的结核杆菌人类分离株。在这些分离株中，我们检测到基因系统发育之间的不一致以及镶嵌基因序列，其单个元件可在经典的结核分枝杆菌中找到。因此，尽管结核分枝杆菌基因组表面上具有同质性，但它似乎是由早于克隆扩增的水平基因转移事件所导致的复合组装体。管家基因中同义核苷酸变异的数量表明，结核杆菌与东非早期人类同时存在，因此与人类宿主共同进化的时间比之前认为的要长得多。这些结果为揭示结核分枝杆菌进化成功的分子基础开辟了新的视角。
