Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan.
PLoS One. 2024 Apr 26;19(4):e0300634. doi: 10.1371/journal.pone.0300634. eCollection 2024.
The flagellar motor proteins, MotA and MotB, form a complex that rotates the flagella by utilizing the proton motive force (PMF) at the bacterial cell membrane. Although PMF affects the susceptibility to aminoglycosides, the effect of flagellar motor proteins on the susceptibility to aminoglycosides has not been investigated. Here, we found that MotB overexpression increased susceptibility to aminoglycosides, such as kanamycin and gentamicin, in Bacillus subtilis without affecting swimming motility. MotB overexpression did not affect susceptibility to ribosome-targeting antibiotics other than aminoglycosides, cell wall-targeting antibiotics, DNA synthesis-inhibiting antibiotics, or antibiotics inhibiting RNA synthesis. Meanwhile, MotB overexpression increased the susceptibility to aminoglycosides even in the motA-deletion mutant, which lacks swimming motility. Overexpression of the MotB mutant protein carrying an amino acid substitution at the proton-binding site (D24A) resulted in the loss of the enhanced aminoglycoside-sensitive phenotype. These results suggested that MotB overexpression sensitizes B. subtilis to aminoglycosides in a motility-independent manner. Notably, the aminoglycoside-sensitive phenotype induced by MotB requires the proton-binding site but not the MotA/MotB complex formation.
鞭毛马达蛋白 MotA 和 MotB 形成一个复合物，通过利用细菌细胞膜上的质子动力势（PMF）来旋转鞭毛。尽管 PMF 会影响对氨基糖苷类药物的敏感性，但鞭毛马达蛋白对氨基糖苷类药物敏感性的影响尚未得到研究。在这里，我们发现枯草芽孢杆菌中 MotB 的过表达增加了对氨基糖苷类药物（如卡那霉素和庆大霉素）的敏感性，而不影响泳动运动性。MotB 的过表达不影响除氨基糖苷类药物以外的其他针对核糖体的抗生素、针对细胞壁的抗生素、抑制 DNA 合成的抗生素或抑制 RNA 合成的抗生素的敏感性。同时，即使在缺乏泳动运动性的 motA 缺失突变体中，MotB 的过表达也增加了对氨基糖苷类药物的敏感性。在质子结合位点（D24A）发生氨基酸取代的 MotB 突变蛋白的过表达导致增强的氨基糖苷类药物敏感表型丧失。这些结果表明，MotB 的过表达以一种不依赖于运动的方式使枯草芽孢杆菌对氨基糖苷类药物敏感。值得注意的是，由 MotB 诱导的氨基糖苷类药物敏感表型需要质子结合位点，但不需要 MotA/MotB 复合物的形成。
