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Journal of Bacteriology, May 2009, p. 2944-2952, Vol. 191, No. 9
0021-9193/09/$08.00+0     doi:10.1128/JB.00074-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Potassium Transport in Corynebacterium glutamicum Is Facilitated by the Putative Channel Protein CglK, Which Is Essential for pH Homeostasis and Growth at Acidic pH{triangledown}

Martin Follmann,# Markus Becker,# Ines Ochrombel, Vera Ott, Reinhard Krämer,* and Kay Marin*

Institute of Biochemistry, University of Cologne, 50674 Köln, Germany

Received 24 February 2009/ Accepted 25 February 2009

We studied the requirement for potassium and for potassium transport activity for the biotechnologically important bacterium Corynebacterium glutamicum, which is used for large-scale production of amino acids. Different from many other bacteria, at alkaline or neutral pH, C. glutamicum is able to grow without the addition of potassium, resulting in very low cytoplasmic potassium concentrations. In contrast, at acidic pH, the ability for growth was found to depend on the presence of K+. For the first time, we provide experimental evidence that a potential potassium channel (CglK) acts as the major potassium uptake system in a bacterium and proved CglK's function directly in its natural membrane environment. A full-length CglK protein and a separate soluble protein harboring the RCK domain can be translated from the cglK gene, and both are essential for full CglK functionality. As a reason for potassium-dependent growth limitation at acidic pH, we identified the impaired capacity for internal pH homeostasis, which depends on the availability and internal accumulation of potassium. Potassium uptake via CglK was found to be relevant for major physiological processes, like the activity of the respiratory chain, and to be crucial for maintenance of the internal pH, as well as for the adjustment of the membrane potential in C. glutamicum.

* Corresponding author. Mailing address: Institute of Biochemistry, University of Cologne, 50674 Köln, Germany. Phone and fax for Kay Marin: 49 (0)221 470 6476. E-mail: kay.marin{at}uni-koeln.de. Phone and fax for Reinhard Kramer: 49 (0)221 470 6461. E-mail: r.kraemer{at}uni-koeln.de

{triangledown} Published ahead of print on 6 March 2009.

# These authors contributed equally to this work.

Journal of Bacteriology, May 2009, p. 2944-2952, Vol. 191, No. 9
0021-9193/09/$08.00+0     doi:10.1128/JB.00074-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Youn, J.-W., Jolkver, E., Kramer, R., Marin, K., Wendisch, V. F. (2009). Characterization of the Dicarboxylate Transporter DctA in Corynebacterium glutamicum. J. Bacteriol. 191: 5480-5488 [Abstract] [Full Text]  


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