Osmoadaptation of Thiocapsa roseopersicina OP‐1 in batch and continuous culture: Accumulation of K + and sucrose in response to osmotic stress

Increasing growth medium NaCl concentration inhibited the growth of Thiocapsa roseopersicina OP‐1 due to both an increase in the lag phase of the growth cycle and a reduction in specific growth rate. Addition of 0.05% w/v acetate to the growth medium stimulated growth at all NaCl concentrations, but this stimulation was greatest at supra‐optimal NaCl 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 increased linearly with increasing growth medium NaCl concentration indicating as osmoregulatory role for these solutes. Time courses of osmoadaptation in batch culture demonstrated a biphasic response to osmotic stress. The initial phase consisted of a rapid accumulation (within 30 min) of K + from the growth medium. This was followed by a slower synthesis of sucrose which partially replaced intracellular K + during the second phase of osmoadaptation.