OSMOADAPTATION OF THIOCAPSA-ROSEOPERSICINA OP-1 IN BATCH AND CONTINUOUS-CULTURE - ACCUMULATION OF K-STRESS( AND SUCROSE IN RESPONSE TO OSMOTIC)

Increasing growth medium NaCl concentration inhibited the growth of Th iocapsa roseopersicina OP-1 due to both an increase in the lag phase o f the growth cycle and a reduction in specific growth rate. Addition o f 0.050% w/v acetate to the growth medium stimulated growth at all NaC l concentrations, but this stimulation was greatest at supra-optimal N aCl concentrations. Optimal growth under all conditions tested in both batch and continuous culture was recorded at a salt concentration of 0.3 M NaCl. The intracellular concentrations of both K+ and sucrose in creased linearly with increasing growth medium NaCl concentration indi cating an osmoregulatory role for these solutes. Time courses of osmoa daptation in batch culture demonstrated a biphasic response to osmotic stress. The initial phase consisted of a rapid accumulation (within 3 0 min) of K+ from the growth medium. This was followed by a slower syn thesis of sucrose which partially replaced intracellular K+ during the second phase of osmoadaptation.