Nitrate and ammonium utilization in cell suspension of the acidophilic thermophilic non-vacuolate alga Cyanidium caldarium and the related pH variations in the external medium, were measured using ion specific electrodes. Nitrate absorption and pH variations were also monitored. The acidophilic C. caldarium allowed experimentation under acidic conditions where CO2 exchange did not affect pH measurements. Both ammonium and nitrate assimilation occured in dark and light conditions; however, the rate of assimilation was higher in the light than in the dark. The presence of oxygen was an absolute requirement. It is suggested that the uptake of both nitrate and ammonium are mediated by active mechanisms dependent on the energy charge of the cell. The assimilation of nitrate and ammonium was accompanied by an increase and a decrease, respectively, of the external medium pH. Under steady-state conditions, for each equivalent of ammonium incorporated there were 0.8-1 equiv. of protons released into the external medium and for each equivalent of nitrate absorbed there were 1-1.2 equiv. of protons absorbed from the external medium. © 1981.
Nitrate and ammonium assimilation in algal cell-suspensions and related pH variations in the external medium, monitored by electrodes
FUGGI, Amodio;
1981
Abstract
Nitrate and ammonium utilization in cell suspension of the acidophilic thermophilic non-vacuolate alga Cyanidium caldarium and the related pH variations in the external medium, were measured using ion specific electrodes. Nitrate absorption and pH variations were also monitored. The acidophilic C. caldarium allowed experimentation under acidic conditions where CO2 exchange did not affect pH measurements. Both ammonium and nitrate assimilation occured in dark and light conditions; however, the rate of assimilation was higher in the light than in the dark. The presence of oxygen was an absolute requirement. It is suggested that the uptake of both nitrate and ammonium are mediated by active mechanisms dependent on the energy charge of the cell. The assimilation of nitrate and ammonium was accompanied by an increase and a decrease, respectively, of the external medium pH. Under steady-state conditions, for each equivalent of ammonium incorporated there were 0.8-1 equiv. of protons released into the external medium and for each equivalent of nitrate absorbed there were 1-1.2 equiv. of protons absorbed from the external medium. © 1981.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
