GROWTH OF CORYNEBACTERIUM-GLUTAMICUM IN AMMONIUM AND POTASSIUM LIMITED CONTINUOUS CULTURES UNDER HIGH OSMOTIC-PRESSURE

In order to determine the possible effect of nutrient limitations on t he response of Corynebacterium glutamicum to a saline osmotic up-shock , the bacteria were grown in continuous cultures, at osmotic pressures of 0.4 osmol/kg and 1.2 osmol/kg, under ammonia and potassium limitat ion. At the low osmolality of 0.4 osmol/kg, the glutamate and proline levels of 15 mg/g and 5 mg/g dry weight respectively were lower than p reviously reported in glucose-limited continuous cultures (50 mg/g and 10 mg/g dry weight respectively). On the other hand, the internal tre halose pool was much higher at 40 mg/g dry weight. When the medium osm olality was increased to 1.2 osmol/kg by NaCl addition, under ammonia limitation, the proline content rose from 5 mg/g to 20 mg/g dry weight and the trehalose content from 40 mg/g to 70 mg/g dry weight, whereas the intracellular pool of glutamate remained essentially constant. An increase in the internal sodium content was also observed. Similar re sults were found for the internal pool of glutamate, proline and treha lose when C. glutamicum was grown under potassium limitations at an os molality of 1.2 osmol/kg. There were also higher levels of sodium ions , glutamine and alanine. According to the present results, whereas pro line was previously reported to be the dominantly accumulated osmoprot ectant in C. glutamicum grown under glucose limitations, under ammonia and potassium limitations trehalose represented the dominantly synthe sized metabolite.