Nitrogen fixation, ammonium transport and glutamine synthetase activity in an antarctic cyanobacterium Anabaena sp.: Influence of temperature

Thermal responses of three physiological processes, viz. nitrogen fixation, ammonium assimilation and ammonium uptake were studied in Antarctic and tropical isolates of a diazotrophic cyanobacterium Anabaena sp. under influence of various temperatures (5°C to 40°C). Observations revealed: (i) Antarctic isolate exhibited the above mentioned activities at low temperature (5°C), at which tropical isolate remained inactive, (ii) Optimum temperatures for the above physiological processes differed in two isolates and (iii) Energy of activation (Ea) for all of the three physiological processes differed in both of the isolates. This study provides base line data for a little-investigated area of the physiological response of Antarctic cyanobacteria under simulated laboratory conditions.