Abstract
Objectives: It is not fully understood why inhibiting ATP synthesis in Mycobacterium species leads to death in non-replicating cells. We investigated the bactericidal mode of action of the anti-tubercular F1Fo-ATP synthase inhibitor bedaquiline (Sirturo™) in order to further understand the lethality of ATP synthase inhibition. Methods: Mycobacterium smegmatis strains were used for all the experiments. Growth and survival during a bedaquiline challenge were performed in multiple media types. A time-course microarray was performed during initial bedaquiline challenge in minimal medium. Oxygen consumption and proton-motive force measurements were performed on whole cells and inverted membrane vesicles, respectively. Results: A killing of 3 log.10 cfu/mL was achieved 4-fold more quickly in minimal medium (a glycerol carbon source) versus rich medium (LB with Tween 80) during bedaquiline challenge. Assessing the accelerated killing condition, we identified a transcriptional remodelling of metabolism that was consistent with respiratory dysfunction but inconsistent with ATP depletion. In glycerol-energized cell suspensions, bedaquiline caused an immediate 2.3-fold increase in oxygen consumption. Bedaquiline collapsed the transmembrane pH gradient, but not the membrane potential, in a dose-dependent manner. Both these effects were dependent on binding to the F.1F.o-ATP synthase. Conclusions: Challenge with bedaquiline results in an electroneutral uncoupling of respiration-driven ATP synthesis. This may be a determinant of the bactericidal effects of bedaquiline, while ATP depletion may be a determinant of its delayed onset of killing. We propose that bedaquiline binds to and perturbs the a-c subunit interface of the Fo, leading to futile proton cycling, which is known to be lethal to mycobacteria.
Original language | English (US) |
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Article number | dkv054 |
Pages (from-to) | 2028-2037 |
Number of pages | 10 |
Journal | Journal of Antimicrobial Chemotherapy |
Volume | 70 |
Issue number | 7 |
DOIs | |
State | Published - Dec 6 2015 |
Keywords
- Antimycobacterial agents
- FF-ATP synthase
- Mycobacteria
- R207910
- TMC207
ASJC Scopus subject areas
- Pharmacology
- Microbiology (medical)
- Infectious Diseases
- Pharmacology (medical)