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J. Bacteriol. doi:10.1128/JB.00986-07
Copyright (c) 2007, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Osmolality, temperature and membrane lipid composition modulate the activity of betaine transporter BetP in Corynebacterium glutamicum

Institute of Biochemistry, University of Köln, Zülpicher Str. 47, 50674 Köln, Germany, Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany, FB Biologie/Chemie, University of Osnabrück, Barbarastr. 11, 49069 Osnabrück, Germany

	Abstract

The gram-positive soil bacterium Corynebacterium glutamicum, a major amino acid producing microorganism in biotechnology, is equipped with several osmoregulated uptake systems for compatible solutes, relevant for the physiological response to osmotic stress. The most significant carrier, BetP, is instantly activated in response to increasing cytoplasmic K. Importantly, it is also activated by chill stress independently of osmotic stress. We now show that the activation of BetP both by osmotic and chill stress is altered in C. glutamicum cells grown at and adapted to low temperatures. BetP from cold-adapted cells is less sensitive to osmotic stress. In order to become susceptible for chill activation, cold-adapted cells in addition needed a certain extent of osmotic stimulation, indicating a crosstalk of these two types of stimuli at the level of BetP activity. We further correlated the change of BetP regulation properties in cells grown at different temperatures to changes in the lipid composition of the plasma membrane. For this purpose, the glycerophospholipidome of C. glutamicum grown at different temperatures was analysed by mass spectrometry using quantitative multiple precursor ion scanning. The molecular composition of glycerophospholipids was strongly affected by the growth temperature. The modulatory influence of membrane lipid composition on BetP function was further corroborated by studying the influence of artificial modulation of membrane dynamics by local anesthetics and exclusion of a possible influence of internally accumulated betaine on BetP activity.