Department of Biological Sciences, University of South Carolina, Columbia, SC, 29208, USA.
Curr Microbiol. 2021 Aug;78(8):2899-2904. doi: 10.1007/s00284-021-02549-y. Epub 2021 May 28.
Toxin-antitoxin (TA) systems have been studied in many bacterial genera, but a clear understanding of the evolutionary trajectory of TA operons has not emerged. To address this issue, I identified 42 distinct TA operons in three genomes that represent the three branches of the Caulobacter phylogenetic tree. The location of each operon was then examined to determine if the operon was present in eight additional Caulobacter genomes. Most of the 42 TA operons were present at the same chromosomal location in genomes that represent at least two different branches of the Caulobacter phylogenetic tree. This result indicates that the chromosomal location of TA operons is conserved over evolutionary time scales. One the other hand, there were 177 instances where a TA operon was not present at an expected chromosomal location and four instances where only the antitoxin gene was present. Thus, the variable number of TA operons found in each genome appears to be due primarily to the loss of TA operons, and the addition of new TA operons to a genome was relatively rare. An additional feature of the TA operons was that they seemed to accumulate mutations faster than the adjacent genes.
毒素-抗毒素 (TA) 系统在许多细菌属中都有研究，但 TA 操纵子的进化轨迹还没有明确的认识。为了解决这个问题，我在三个代表柯氏菌进化树三个分支的基因组中鉴定了 42 个不同的 TA 操纵子。然后检查每个操纵子的位置，以确定在另外 8 个柯氏菌基因组中是否存在该操纵子。在代表柯氏菌进化树至少两个不同分支的基因组中，大多数 42 个 TA 操纵子都位于相同的染色体位置。这一结果表明，TA 操纵子的染色体位置在进化时间尺度上是保守的。另一方面，有 177 个 TA 操纵子不在预期的染色体位置，有 4 个只有抗毒素基因存在。因此，每个基因组中发现的 TA 操纵子数量的变化似乎主要是由于 TA 操纵子的缺失，而将新的 TA 操纵子添加到基因组中相对较少。TA 操纵子的另一个特征是，它们似乎比相邻基因积累突变更快。
