The effect of temperature on the sensitivity of nitrogenase to oxygen in the cyanobacteria Anabaena cylindrica (Lemmermann) and Gloeothece (Nägeli).

Transient exposure to elevated temperature (37-40 °C) inhibited N fixation (acetylene reduction) in cultures of the heterocystous cyanobacterium Anabaena cylindrica (Lemmermann) ATCC 27899 and the unicellular, non-heterocystous cyanobacterium Gloeothece sp. (Nägeli) ATCC 27152. In neither organism was inhibition of N fixation due to thermal inactivation of nitrogenase. Rather, inactivation of N fixation at elevated temperature was a consequence of increased sensitivity to inhibition by O In A. cylindrica, thermally induced inactivation of N fixation by O could be correlated with inhibition of uptake hydrogenase. However, in Gloeothece, inhibition of carbon-supported respiratory O consumption by elevated temperature was the probable cause of the increased sensitivity of N fixation to O .