Macguire Ashley E, Ching Meining Carly, Diamond Brett H, Kazakov Alexey, Novichkov Pavel, Godoy Veronica G
Department of Biology, Northeastern University, Boston, Massachusetts, USA.
Mol Microbiol. 2014 Apr;92(1):138-52. doi: 10.1111/mmi.12541. Epub 2014 Mar 3.
The multidrug-resistant, opportunistic pathogen, Acinetobacter baumannii, has spread swiftly through hospitals worldwide. Previously, we demonstrated that A. baumannii regulates the expression of various genes in response to DNA damage. Some of these regulated genes, especially those encoding the multiple error-prone DNA polymerases, can be implicated in induced mutagenesis, leading to antibiotic resistance. Here, we further explore the DNA damage-inducible system at the single cell level using chromosomal transcriptional reporters for selected DNA damage response genes. We found the genes examined respond in a bimodal fashion to ciprofloxacin treatment, forming two phenotypic subpopulations: induced and uninduced. This bimodal response to ciprofloxacin treatment in A. baumannii is unique and quite different than the Escherichia coli paradigm. The subpopulations are not genetically different, with each subpopulation returning to a starting state and differentiating with repeated treatment. We then identified a palindromic motif upstream of certain DNA damage response genes, and have shown alterations to this sequence to diminish the bimodal induction in response to DNA damaging treatment. Lastly, we are able to show a biological advantage for a bimodal response, finding that one subpopulation survives ciprofloxacin treatment better than the other.
多重耐药的机会致病菌鲍曼不动杆菌已在全球医院中迅速传播。此前，我们证明鲍曼不动杆菌会响应DNA损伤来调节各种基因的表达。其中一些受调控的基因，尤其是那些编码多种易出错DNA聚合酶的基因，可能与诱导突变有关，从而导致抗生素耐药性。在此，我们使用针对选定DNA损伤反应基因的染色体转录报告基因，在单细胞水平上进一步探索DNA损伤诱导系统。我们发现所检测的基因对环丙沙星治疗呈现双峰反应，形成两个表型亚群：诱导型和未诱导型。鲍曼不动杆菌对环丙沙星治疗的这种双峰反应是独特的，与大肠杆菌模式有很大不同。这些亚群在基因上并无差异，每个亚群在重复治疗后都会恢复到起始状态并发生分化。然后，我们在某些DNA损伤反应基因的上游鉴定出一个回文基序，并表明对该序列的改变会减少对DNA损伤治疗产生的双峰诱导。最后，我们能够证明双峰反应具有生物学优势，发现一个亚群在环丙沙星治疗下比另一个亚群存活得更好。
