C. Prosperi et al., INFLUENCE OF PH, LIGHT-INTENSITY AND OXYGEN ON THE SHORT-TERM EFFECT OF AMMONIUM ON NITROGENASE ACTIVITY OF CYANOBACTERIA FROM RICE FIELDS, Environmental and experimental botany, 33(4), 1993, pp. 545-552
The influence of pH, light intensity and anaerobiosis on the short-ter
m effect of ammonium on nitrogenase activity was investigated in four
cyanobacteria (Nostoc punctiforme UAM 205, Anabaena variabilis UAM 202
, Calohhrix marchica UAM 214 and Nodularia spumigena UAM 204) isolated
from rice fields in Valencia, Spain. A fast switch-off of nitrogenase
activity by ammonium was observed only when cells were incubated in t
he light in the presence of oxygen at pH 10. A stabilizing effect of c
arbohydrates, which was evident at pH 7, was not effective at pH 10. U
nder these conditions ammonium caused a light-dependent oxygen uptake
insensitive to cyanide, which could be related to inactivation of nitr
ogenase.