Résumé
Movement of water into or out of cells is a fundamental process of life found throughout nature. However the molecular pathway of this transport remained elusive until discovery of the aquaporins, a large family of water channel proteins. In bacteria, the osmotic movement of water across the cytoplasmic membrane is one of the mechanisms triggered to maintain the cell turgor, a function essential for growth and survival. The first known prokaryotic aquaporin water channel gene, aqpZ, has been reported in Escherichia coli (Calamita et al., 1995) and functionally characterized (Borgnia et al., 1999; Delamarche et al., 1999). This indicates that, in spite of the high surface-to-volume ratio characterizing bacteria, the simple diffusion of water through the membrane lipids could not be always sufficient to preserve turgor. Presently, several microbial members of the MIP family have been identified by sequence homology, but only few microbial MIPs have been functionally studied (Maurel et al., 1994).