The Water Relations of Gas-Vacuolate Prokaryotes

摘要: Gas vesicles can be used to provide an instantaneous measurement of the hydrostatic pressure that exists inside cells prokaryotic organisms possess them. Such measurements, carried out on blue-green alga Anabaena flos-aquae, have been determine its cell--water relations. The cell turgor is determined as difference between mean critical required collapse gas in suspended hypertonic sucrose solution and for water. falls slightly are collapsed because volume contents decreases. relation described by volumetric elastic modulus, $\epsilon $, which measuring solutions increasing concentration. As external osmotic increased, pressure, stretches wall, shrinks losing water calculated from internal equal sum pressure. modulus A. flos-aquae quite low, about 11 bar, constant over a range pressures down 1.3 bar. When cells, suddenly drops, but it partially recovers enters restore balance. rate entry computed time course vesicle held under moderate pressures, this hydraulic conductivity, L$_{\text{p}}$, wall membrane calculated; estimated 0.14 $\mu $m s$^{-1}$ bar$^{-1}$ flosaquae, with assumption there no errors owing delay contraction wall. permeability, k, various solutes following recovery penetrate 0.15 osm Two methods rise monitored collapse, one slowly penetrating (e.g., mannitol) rapidly glycerol). Passive uptake indicated exponential kinetics initial value water, sugar alcohols; active results exceeding value, observed K$^{+}$ glycine--betaine. biological significance relations gas-vacuolate discussed.