Abstract：
The Insertion Sequence 711 (IS711) is linked to the Brucella genus. Mapping the genomic distribution of IS711 can help understand this insertion element\'s biological and evolutionary role. This work aimed to delineate the genomic distribution of the IS711 element and to study its association with Brucella evolution. A total of 124 genomes representing 9 Brucella species were searched using BLASTn sequence alignment tool to identify complete and truncated copies of IS711. Based on the genomic context, each IS711 locus was assigned a code using the initial letters of its neighboring genes. Various tools were used to annotate the neighboring genes and determine the shared synteny around orthologous IS711 loci. The tool Islandviewer 4 was used to scan for genomic islands. The Codon Tree method was used to build phylogenetic trees of B. melitensis, B. abortus, and B. suis genomes. The phylogenetic trees of the three species were analyzed, taking into account the genomic distribution patterns of IS711. The result of IS711 frequency analysis showed a relatively conserved number of copies/genome for the different species and for some biovars. The analysis showed that Brucella species with a relatively low IS711 copy number (4-8 copies/genome) are linked to domestic animals as primary hosts and have potential for zoonotic transmission. However, species with a relatively higher copy number (12-30 copies/genome) are less zoonotic and tend to be linked with wild animals as primary hosts. Analyzing the genomic distribution map of IS711 loci showed several unique patterns of IS711 distribution that are correlated with the evolution of Brucella species and biovars. The results also showed that 46.2% of the conserved IS711 elements are located within genomic islands. Based on our results and previous data, we postulate a model explaining the IS711 role in Brucella evolution. We assume that during the transition from a free-living to an intracellular lifestyle, a descendant of the Brucella genus had acquired a progenitor sequence of the IS711. Subsequently, a burst in IS711 transposition occurred. This parasitic expansion can be deleterious and has to be counteracted by evolutionary forces to prevent lineage extension and to promote adaptation to host. Similar to other plasmid-free pathogenic α-Proteobacteria bacteria, the balance of expansion and reduction of insertion elements could be one of the mechanisms to control genome reduction and streamlining. We hypothesize that the IS711-mediated genomic changes and other small sequence nucleotide changes in specific orthologous genes could significantly contribute to Brucella\'s evolution and adaptation to different animal hosts.
摘要：
插入序列711(IS711)与布鲁氏菌属相连。绘制IS711的基因组分布图有助于理解这种插入元件的生物学和进化作用。这项工作旨在描述IS711元件的基因组分布，并研究其与布鲁氏菌进化的关系。使用BLASTn序列比对工具搜索了代表9个布鲁氏菌物种的总共124个基因组，以鉴定IS711的完整和截短拷贝。根据基因组背景，每个IS711基因座使用其相邻基因的起始字母分配了一个代码.使用各种工具来注释相邻基因并确定直系同源IS711基因座周围的共享同系物。工具Islandviewer4用于扫描基因组岛。密码子树方法用于建立B.melitensis的系统发育树，B.流产，和B.suis基因组。分析了这三个物种的系统发育树，考虑到IS711的基因组分布模式。IS711频率分析的结果表明，对于不同物种和某些生物变体，拷贝数/基因组相对保守。分析表明，具有相对较低的IS711拷贝数（4-8个拷贝/基因组）的布鲁氏菌物种与作为主要宿主的家畜有关，并具有人畜共患传播的潜力。然而,拷贝数相对较高（12-30个拷贝/基因组）的物种人畜共患病较少，并且倾向于与作为主要宿主的野生动物相关。分析IS711基因座的基因组分布图显示了IS711分布的几种独特模式，这些模式与布鲁氏菌物种和生物进化有关。结果还显示46.2%的保守IS711元件位于基因组岛内。根据我们的结果和以前的数据，我们假设一个模型解释了IS711在布鲁氏菌进化中的作用。我们假设在从自由生活向细胞内生活方式转变的过程中，布鲁氏菌属的后代获得了IS711的祖先序列。随后，在IS711转座中发生了突发。这种寄生扩展可能是有害的，必须通过进化力量来抵消，以防止谱系扩展并促进对宿主的适应。与其他无质粒致病性α-变形杆菌细菌相似，插入元件扩增和减少的平衡可能是控制基因组减少和精简的机制之一.我们假设，IS711介导的基因组变化和特定直系同源基因中的其他小序列核苷酸变化可以显着促进布鲁氏菌的进化和对不同动物宿主的适应。
