Influence of osmotic and metal stresses on nitrogenase activity of cyanobacteria isolated from paddy fields

Abstract

Samples were collected from paddy fields in Corum-Turkiye. Nitrogen-free BG-11 medium was used for isolation of nitrogen fixing cyanobacteria. Acetylene reduction technique was used to determine the effects of different chemical agents on the nitrogenase activities of the cyanobacteria, which were identified at the genus level. Nostoc showed the highest nitrogenase activity (0.09 ethylene mu l/mg.h) at 50 mM salt concentration. At 60 mM sucrose concentration, Nostoc showed the highest nitrogenase activity (0.08 ethylene mu l/mg.h). The highest tolerances for the metals were present in Anabaena (0.006 ethylene mu l/mg.h) for iron (20 ppm), Nodularia 0.1 ethylene mu l/mg.h (for manganese 20 ppm) and Nostoc 0.96 ethylene mu l/mg.h (for zinc 5 ppm).