Guangdong Laboratory for Lingnan Modern Agriculture, South China Agricultural University, Guangzhou 510642, China.
College of Plant Protection, Integrative Microbiology Research Center, South China Agricultural University, Guangzhou, 510642, China.
J Antimicrob Chemother. 2023 Sep 5;78(9):2162-2169. doi: 10.1093/jac/dkad207.
RNA polymerase (RNAP) is highly conserved and essential for prokaryotic housekeeping activities, making it an important target for the development of new antibiotics. The rpoB gene, encoding a β-subunit of bacterial RNAP, has a well-known association with rifampicin resistance. However, the roles of other RNAP component genes such as rpoA, encoding an α-subunit of RNAP, in antibiotic resistance remain unexplored.
To characterize the antibiotic resistance-related role of RpoA.
We measured the expression of the MexEF-OprN efflux pump in an RpoA mutant using a transcriptional reporter. The MICs of various antibiotics for this RpoA mutant were determined.
We uncover a novel role of antibiotic susceptibility for an RpoA mutant in Pseudomonas aeruginosa. We found that a single amino acid substitution in RpoA resulted in reduced activity of the MexEF-OprN efflux pump, which is responsible for the exportation of various antibiotics, including ciprofloxacin, chloramphenicol, ofloxacin and norfloxacin. This attenuated efflux pump activity, caused by the RpoA mutation, conferred the bacteria further susceptibility to antibiotics regulated by MexEF-OprN. Our work further revealed that certain clinical P. aeruginosa isolates also contained the same RpoA mutation, providing clinical relevance to our findings. Our results elucidate why this new antibiotic-susceptible function of RpoA mutants would have remained undetected in conventional screens for mutants involving antibiotic resistance.
The discovery of antibiotic susceptibility in an RpoA mutant implicates a new therapeutic approach for treating clinical isolates of P. aeruginosa with RpoA mutations, using specific antibiotics regulated by MexEF-OprN. More generally, our work suggests that RpoA could serve as a promising candidate target for anti-pathogen therapeutic purposes.
RNA 聚合酶（RNAP）高度保守，是原核生物维持基本生命活动所必需的，因此成为开发新型抗生素的重要靶点。rpoB 基因编码细菌 RNAP 的β亚基，与利福平耐药性密切相关。然而，其他 RNAP 成分基因（如编码 RNAPα亚基的 rpoA 基因）在抗生素耐药性中的作用仍未被探索。
描述 RpoA 与抗生素耐药性的关系。
我们使用转录报告基因测定法检测 rpoA 突变体中 MexEF-OprN 外排泵的表达。测定该 rpoA 突变体对各种抗生素的 MIC 值。
我们揭示了铜绿假单胞菌中 rpoA 突变体对抗生素敏感性的新作用。我们发现，RpoA 中的一个氨基酸取代导致 MexEF-OprN 外排泵的活性降低，该泵负责将各种抗生素（包括环丙沙星、氯霉素、氧氟沙星和诺氟沙星）排出细胞外。这种由 RpoA 突变引起的减弱的外排泵活性，使细菌对 MexEF-OprN 调控的抗生素更加敏感。我们的工作进一步表明，某些临床分离的铜绿假单胞菌也含有相同的 RpoA 突变，这为我们的发现提供了临床相关性。我们的结果解释了为什么在涉及抗生素耐药性的突变体常规筛选中，rpoA 突变体的这种新的抗生素敏感性功能一直未被发现。
rpoA 突变体的抗生素敏感性发现提示了一种新的治疗方法，可用于治疗含有 RpoA 突变的铜绿假单胞菌临床分离株，使用特定的 MexEF-OprN 调控的抗生素。更普遍地说，我们的工作表明 RpoA 可能成为抗病原体治疗的有前途的候选靶标。
