Contribution of horizontally acquired genomic islands to the evolution of the tubercle bacilli
Contribution of horizontally acquired genomic islands to the evolution of the tubercle bacilli
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DOI：
10.1093/molbev/msm111
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发表时间：
2007-08-01
影响因子：
10.7
通讯作者：
Deschavanne, Patrick
中科院分区：
文献类型：
--
作者：
Becq, Jennifer;Gutierrez, Maria Cristina;Deschavanne, Patrick
水平基因转移(HGT)对结核分枝杆菌--人类结核病的主要致病因子--以及结核分枝杆菌复合体中密切相关成员的进化的贡献仍然知之甚少。利用全基因组参数分析的组合，我们已经识别出48个具有非典型特征的结核分枝杆菌染色体区域，可能是由于HGT。这些特定区域占基因组(199kb)的4.5%，包括256个基因。许多细菌显示了其他细菌中发现的基因组岛的典型特征，包括来自可移动遗传元件的残留物、侧翼直接重复序列、插入在tRNA序列附近的基因，以及具有推测或已知毒力功能的基因。对这48个区域中的9个区域进行的Southern blotting分析证实，它们存在于“原结核分枝杆菌”中，这是结核分支杆菌复合体的祖先物种。最后，我们的结果有力地表明，结核杆菌的祖先是一种环境杆菌，它与其他细菌物种交换遗传物质，特别是包括存在于其周围的变形杆菌。本研究描述了一种寻找分枝杆菌毒力基因的合理方法，并强调了解剖基因转移网络对提高我们对分枝杆菌致病和进化的理解的重要性。
The contribution of horizontal gene transfer (HGT) to the evolution of Mycobacterium tuberculosis - the main causal agent of tuberculosis in humans - and closely related members of the M. tuberculosis complex remains poorly understood. Using a combination of genome-wide parametric analyses, we have identified 48 M. tuberculosis chromosomal regions with atypical characteristics, potentially due to HGT. These specific regions account for 4.5% of the genome (199 kb) and include 256 genes. Many display features typical of the genomic islands found in other bacteria, including residual material from mobile genetic elements, flanking direct repeats, insertion in the vicinity of tRNA sequences, and genes with putative or documented virulence functions. Southern blotting analysis of nine of these 48 regions confirmed their presence in "Mycobacterium prototuberculosis," the ancestral species of the M. tuberculosis complex. Finally, our results strongly suggest that the ancestor of the tubercle bacilli was an environmental bacillus that exchanged genetic material with other bacterial species, including Proteobacteria in particular, present in its surroundings. This study describes a rational approach to searching for mycobacterial virulence genes, and highlights the importance of dissecting gene transfer networks to improve our understanding of mycobacterial pathogenicity and evolution.