Swaminath Sharmada, Pradhan Atul, Nair Rashmi Ravindran, Ajitkumar Parthasarathi
Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore 560012, Karnataka, India.
Department of Biology, University of San Diego, San Diego, CA, USA.
Curr Res Microb Sci. 2022 May 31;3:100142. doi: 10.1016/j.crmicr.2022.100142. eCollection 2022.
The physiological role of mono-ADP-ribosyl transferase (Arr) of , which inactivates rifampicin, remains unclear. An earlier study reported increased expression of during oxidative stress and DNA damage. This suggested a role for Arr in the oxidative status of the cell and its associated effect on DNA damage. Since reactive oxygen species (ROS) influence oxidative status, we investigated whether Arr affected ROS levels in . Significantly elevated levels of superoxide and hydroxyl radical were found in the mid-log phase (MLP) cultures of the knockout strain (-KO) as compared those in the wild-type strain (WT). Complementation of -KO with expression from genomically integrated under its native promoter restored the levels of ROS equivalent to that in WT. Due to the inherently high ROS levels in the actively growing KO, rifampicin resisters with mutations could be selected at 0 hr of exposure itself against rifampicin, unlike in the WT where the resisters emerged at 12 hr of rifampicin exposure. Microarray analysis of the actively growing cultures of -KO revealed significantly high levels of expression of genes from succinate dehydrogenase I and NADH dehydrogenase I operons, which would have contributed to the increased superoxide levels. In parallel, expression of specific DNA repair genes was significantly decreased, favouring retention of the mutations inflicted by the ROS. Expression of several metabolic pathway genes also was significantly altered. These observations revealed that Arr was required for maintaining a gene expression profile that would provide optimum levels of ROS and DNA repair system in the actively growing .
可使利福平失活的单磷酸腺苷核糖基转移酶（Arr）的生理作用仍不清楚。一项早期研究报告称，在氧化应激和DNA损伤期间，其表达增加。这表明Arr在细胞的氧化状态及其对DNA损伤的相关影响中发挥作用。由于活性氧（ROS）会影响氧化状态，我们研究了Arr是否会影响[具体研究对象]中的ROS水平。与野生型菌株（WT）相比，在[具体研究对象]基因敲除菌株（-KO）的对数中期（MLP）培养物中发现超氧化物和羟基自由基水平显著升高。用其天然启动子下基因组整合的[具体基因名称]表达对-KO进行互补，可使ROS水平恢复到与WT相当的水平。由于在活跃生长的-KO中ROS水平本来就很高，与WT中利福平抗性菌株在利福平暴露12小时后才出现不同，在-KO中，在暴露0小时时就能筛选出具有[具体突变类型]突变的利福平抗性菌株。对活跃生长的-KO培养物进行微阵列分析发现，琥珀酸脱氢酶I和NADH脱氢酶I操纵子的基因表达水平显著升高，这可能导致了超氧化物水平的增加。同时，特定DNA修复基因的表达显著降低，有利于保留由ROS造成的突变。几种代谢途径基因的表达也发生了显著改变。这些观察结果表明，Arr是维持基因表达谱所必需的，该基因表达谱能在活跃生长的[具体研究对象]中提供最佳水平的ROS和DNA修复系统。
