The potassium transporter KdpA affects persister formation by regulating ATP levels in Mycobacterium marinum

ABSTRACT

Mycobacterial persistence mechanisms remain to be fully characterized. Screening a transposon insertion library of Mycobacterium marinum identified kdpA, whose inactivation reduced the fraction of persisters after exposure to rifampicin. kdpA encodes a transmembrane protein that is part of the Kdp-ATPase, an ATP-dependent high-affinity potassium (K⁺) transport system. We found that kdpA is induced under low K⁺ conditions and is required for pH homeostasis and growth in media with low concentrations of K⁺. The inactivation of the Kdp system in a kdpA insertion mutant caused hyperpolarization of the cross-membrane potential, increased proton motive force (PMF) and elevated levels of intracellular ATP. The KdpA mutant phenotype could be complemented with a functional kdpA gene or supplementation with high K⁺ concentrations. Taken together, our results suggest that the Kdp system is required for ATP homeostasis and persister formation. The results also confirm that ATP-mediated regulation of persister formation is a general mechanism in bacteria, and suggest that K⁺ transporters could play a role in the regulation of ATP levels and persistence. These findings could have implications for the development of new drugs that could either target persisters or reduce their presence.

KEYWORDS:

• Persister
• Mycobacterium marinum
• potassium
• ATP
• rifampicin

Acknowledgements

We thank Jun Liu, Department of Molecular Genetics, University of Toronto, for M. marinum M strain. We also thank E. J. Rubin, Harvard University, for providing the MycoMarT7 mariner transposon phage and D. B. Young, Imperial College London, for plasmid pSMT3L.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by Natural Science Foundation of China [81661128043, 81871625 to Q.G., 81761148027 to C.W. and 31830002 to L.L.] National Science and Technology Major Project of China [2017ZX10201302-006], the Outstanding Youth Training Program of Shanghai Municipal Health Commission [2018YQ54], Shanghai Sailing Program [18YF1420400].