分枝杆菌属特定基因的破坏会损害其在体内的适应性。
Disruption of Mycobacterium avium subsp. paratuberculosis-specific genes impairs in vivo fitness.
机构信息
Department of Microbiology and Immunology, McGill University, 3775 University Street, Montreal, QC H3A 2B4, Canada.
出版信息
BMC Genomics. 2014 May 31;15(1):415. doi: 10.1186/1471-2164-15-415.
BACKGROUND
Mycobacterium avium subsp. paratuberculosis (MAP) is an obligate intracellular pathogen that infects many ruminant species. The acquisition of foreign genes via horizontal gene transfer has been postulated to contribute to its pathogenesis, as these genetic elements are absent from its putative ancestor, M. avium subsp. hominissuis (MAH), an environmental organism with lesser pathogenicity. In this study, high-throughput sequencing of MAP transposon libraries were analyzed to qualitatively and quantitatively determine the contribution of individual genes to bacterial survival during infection.
RESULTS
Out of 52384 TA dinucleotides present in the MAP K-10 genome, 12607 had a MycoMarT7 transposon in the input pool, interrupting 2443 of the 4350 genes in the MAP genome (56%). Of 96 genes situated in MAP-specific genomic islands, 82 were disrupted in the input pool, indicating that MAP-specific genomic regions are dispensable for in vitro growth (odds ratio = 0.21). Following 5 independent in vivo infections with this pool of mutants, the correlation between output pools was high for 4 of 5 (R = 0.49 to 0.61) enabling us to define genes whose disruption reproducibly reduced bacterial fitness in vivo. At three different thresholds for reduced fitness in vivo, MAP-specific genes were over-represented in the list of predicted essential genes. We also identified additional genes that were severely depleted after infection, and several of them have orthologues that are essential genes in M. tuberculosis.
CONCLUSIONS
This work indicates that the genetic elements required for the in vivo survival of MAP represent a combination of conserved mycobacterial virulence genes and MAP-specific genes acquired via horizontal gene transfer. In addition, the in vitro and in vivo essential genes identified in this study may be further characterized to offer a better understanding of MAP pathogenesis, and potentially contribute to the discovery of novel therapeutic and vaccine targets.
背景
禽分枝杆菌亚种副结核分枝杆菌（MAP）是一种专性细胞内病原体，感染许多反刍动物物种。通过水平基因转移获得的外源基因被认为有助于其发病机制，因为这些遗传元件不存在于其假定的祖先禽分枝杆菌亚种同源物（MAH）中，MAH 是一种致病性较低的环境生物体。在这项研究中，对 MAP 转座子文库的高通量测序进行了分析，以定性和定量地确定单个基因对细菌感染过程中存活的贡献。
结果
在 MAP K-10 基因组中存在的 52384 个 TA 二核苷酸中，有 12607 个在输入池中具有 MycoMarT7 转座子，中断了 MAP 基因组中的 4350 个基因中的 2443 个（56%）。在位于 MAP 特异性基因组岛中的 96 个基因中，有 82 个在输入池中被破坏，这表明 MAP 特异性基因组区域对于体外生长是可有可无的（优势比=0.21）。在对该突变体库进行 5 次独立的体内感染后，4 次中的 4 次输出池之间具有高相关性（R=0.49 至 0.61），这使我们能够确定那些破坏基因在体内重现性降低细菌适应性的基因。在体内适应性降低的 3 个不同阈值下，MAP 特异性基因在预测的必需基因列表中过度表达。我们还鉴定出了感染后严重耗竭的其他基因，其中一些基因在结核分枝杆菌中有同源必需基因。
结论
这项工作表明，MAP 体内存活所需的遗传元件代表了保守的分枝杆菌毒力基因和通过水平基因转移获得的 MAP 特异性基因的组合。此外，本研究中鉴定的体外和体内必需基因可能进一步得到表征，以更好地了解 MAP 发病机制，并可能有助于发现新的治疗和疫苗靶点。
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