Department of Biological Sciences, University of South Carolina, Columbia, South Carolina, United States of America.
PLoS One. 2020 Jan 28;15(1):e0227987. doi: 10.1371/journal.pone.0227987. eCollection 2020.
Bacteria can acquire new genes by incorporating environmental DNA into their genomes, yet genome sizes stay relatively constant. In nature, gene acquisition is a rare event so it is difficult to observe. However, the Caulobacter crescentus CB2A genome contains 114 insertions of genetic material from the closely-related NA1000 strain, providing a unique opportunity to analyze the horizontal transfer of genetic material. Analyses of these insertions led to a new model that involves preferential recombination at non-homologous regions that are flanked by regions of homology and does not involve any mutational processes. The net result is the replacement of segments of the recipient genome instead of the simple addition of genetic material during horizontal gene transfer. Analyses of the genomes of closely related strains of other bacterial and archaea genera, suggested that horizontal gene transfer occurs preferentially in non-homologous regions in these organisms as well. Thus, it appears to be a general phenomenon that prokaryotic horizontal gene transfer occurs preferentially at sites where the incoming DNA contains a non-homologous region that is flanked by regions of homology. Therefore, gene replacement is a common phenomenon during horizontal gene transfer.
细菌可以通过将环境 DNA 纳入其基因组来获得新的基因，但基因组大小保持相对恒定。在自然界中，基因获取是一个罕见的事件，因此很难观察到。然而，新月柄杆菌 CB2A 基因组包含了来自密切相关的 NA1000 菌株的 114 个遗传物质插入，为分析遗传物质的水平转移提供了独特的机会。对这些插入的分析导致了一个新的模型，该模型涉及在非同源区域的优先重组，这些区域由同源区域侧翼，不涉及任何突变过程。其净结果是在水平基因转移过程中，受体基因组的片段被替换，而不是简单地添加遗传物质。对其他细菌和古菌属密切相关菌株基因组的分析表明，水平基因转移也优先发生在这些生物的非同源区域。因此，原核生物的水平基因转移优先发生在进入的 DNA 含有非同源区域，该区域由同源区域侧翼，这似乎是一个普遍现象。因此，基因替换是水平基因转移过程中的一个常见现象。
