African Journal of Biotechnology Vol. 6 (15), pp. 1828-1832, 6 August 2007   

ISSN 1684–5315 © 2007 Academic Journals        

Full Length Research Paper

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

Gulten OKMEN (Kurucuoglu)¹*, Gonul DONMEZ² and Sedat DONMEZ³

¹Muğla University, Faculty of Science and Arts, Department of Biology, Mugla, Turkıye.

²Ankara University, Faculty of Science, Department of Biology, Ankara, Turkıye.

³Ankara University, Faculty of Engineering, Department of Food Engineering, Ankara, Turkıye.

*Corresponding author. E-mail: gultenokmen@gmail.com.

Accepted 27 March, 2007

Samples were collected from paddy fields in Corum-Turkıye. 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 µl/mg.h) at 50 mM salt concentration. At 60 mM sucrose concentration, Nostoc showed the highest nitrogenase activity (0.08 ethylene µl/mg.h). The highest tolerances for the metals were present in Anabaena (0.006 ethylene µl/mg.h) for iron (20 ppm), Nodularia 0.1 ethylene µl/mg.h (for manganese 20 ppm)  and Nostoc 0.96 ethylene µl/mg.h (for zinc 5 ppm) .

Key words: Cyanobacteria, nitrogenase activity, isolation, environmental factors.