Bacterial stimulus perception and signal transduction: response to osmotic stress.
When exposed to osmotic stress from the environment, bacteria act to maintain cell turgor and hydration by responding both on the level of gene transcription and protein activity. Upon a sudden decrease in external osmolality, internal solutes are released by the action of membrane embedded mechanosensitive channels. In response to an osmotic upshift, the concentration of osmolytes in the cytoplasm is increased both by de novo synthesis and by active uptake. In order to coordinate these processes of osmoregulation, cells are equipped with systems and mechanisms of sensing physical stimuli correlated to changes in the external osmolality (osmosensing), with pathways to transduce these stimuli into useful signals which can be processed in the cell (signal transduction), and mechanisms of regulating proper responses in the cell to recover from the environmental stress and to maintain all necessary physiological functions (osmoregulation). These processes will be described by a number of representative examples, mainly of osmoreactive transport systems with a focus on available data of their molecular mechanism.
Krämer
Reinhard
R
Institute of Biochemistry, University of Cologne, Zülpicher Str. 47, 50674 Cologne, Germany. r.kraemer@uni-koeln.de
D001419:Bacteria / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism; D001692:Biological Transport; D009997:Osmotic Pressure; D015398:Signal Transduction
D001426:Bacterial Proteins