Studies on the effects of oxygen on acetylene reduction (nitrogen fixation) in Gloeothece sp. ATCC 27152

Abstract

Cultures of Gloeothece sp. ATCC 27152 did not reduce acetylene when exposed to O2 concentrations greater than 0.7 atm. However, following exposure to 1 atm O2 for up to 12 h or to 0.8 atm O2 for up to 14 d, the ability to reduce acetylene recovered rapidly when cultures were returned to air. Complete recovery required active protein synthesis, probably for de novo synthesis of nitrogenase. Respiratory O2 consumption by cultures of Gloeothece was stimulated under elevated concentrations of O2. This respiration may contribute to the protection of nitrogenase from inactivation by O2 at concentrations up to 0.4 atm. The role of Ca2+ in nitrogen fixation may be related to respiratory protection.