Pulsed high-field gradient in vivo NMR spectroscopy to measure diffusionalwater permeability in Corynebacterium glutamicum

Pulsed high-field gradient in vivo NMR spectroscopy was used to measure dif fusional water permeability in cell suspensions of the Gram-positive bacter ium Corynebacterium glutamicum. Two different regions of H2O mobility were detected. One was characterized by the apparent coefficient of self-diffusi on, D-1app = (4.6-12.7) x 10(-8) cm(2) s(-1), depending on the observation time t. The other region was characterized by D-2 = 1.4 x 10(-5) cm(2) s(-1 ). The value of D-2 was similar to the diffusion coefficient of H2O in free water and in extracellular biological fluids. Restricted diffusion could b e demonstrated for the slower process (D-1). It was attributed to the cytop lasm of the cells. The membrane permeability, P-d H2O, for C. glutamicum wa s (4.8 +/- 0.4) x 10(-3) cm s(-1). It compared favorably with values report ed for human erythrocytes and was higher by a factor of about 100 compared to the diffusional permeability for ethanol, P-d (ethanol), in Zymomonas mo bilis. Addition of HgCl2, a water channel inhibitor in eukaryotes, decrease d P-d (H2O) in C. glutamicum by a factor of similar to 8. To our knowledge, these are the first functional studies of water transport in prokaryotes t hat yielded quantitative data, viz., transmembrane water permeability expre ssed through D-H2O and P-d (H2O). (C) 2000 Academic Press.