American Society for Microbiology, Journal of Bacteriology, 14(181), p. 4193-4197, 1999
DOI: 10.1128/jb.181.14.4193-4197.1999
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ABSTRACT Transport of water across the plasma membrane is a fundamental process occurring in all living organisms. In bacteria, osmotic movement of water across the cytoplasmic membrane is needed to maintain cellular turgor; however, the molecular mechanisms of this process are poorly defined. Involvement of aquaporin water channels in bacterial water permeability was suggested by the recent discovery of the aquaporin gene, aqpZ , in Escherichia coli . By employing cryoelectron microscopy to compare E. coli cells containing (AqpZ + ) and lacking (AqpZ − ) aquaporin, we show that the AqpZ water channel rapidly mediates large water fluxes in response to sudden changes in extracellular osmolarity. These findings (i) demonstrate for the first time functional expression of a prokaryotic water channel, (ii) evidence the bidirectional water channel feature of AqpZ, (iii) document a role for AqpZ in bacterial osmoregulation, and (iv) define a suitable model for studying the physiology of prokaryotic water transport.