Nitrogen-fixation by non-heterocystous cyanobacteria in an Antarctic ecosystem

Abstract

Unicellular, non-heterocystous, diazotrophic cyanobacteria Gloeocapsa sp. isolated from Schirmacher Oasis, Antarctica, showed N2-fixation (C2H2-reduction) which was comparable to that of Gloeocapsa sp. isolated from a tropical rice field. The optimum temperature of the Antarctic isolate for nitrogenase activity was 20°C, whereas the tropical isolate expressed its maximum activity at 30°C. Sucrose supported the nitrogenase activity of both the isolates in darkness. The results indicated that the Antarctic isolate behaved differently with respect to temperature compared to the tropical isolate.