Resolution of Nitrogenase of Mycobacterium flavum 301 into Two Components and Cross Reaction with Nitrogenase Components from Other Bacteria

Nitrogenase from the aerobe Mycobacterium flavum 301 was resolved into two protein fractions resembling those obtained from other nitrogen‐fixing bacteria as regards reduction of N 2 , C 2 ,H 2 , cyanide and methyl isocyanide. Fraction 1 contained iron and molybdenum (about 9:1); fraction 2 contained iron only, was rapidly inactivated by oxygen and was cold‐labile. Neither fraction was detected in ammonia‐grown organisms. The optimum ratio of fraction 1 to fraction 2 for acetylene reduction was about 3:1; that for cyanide or methyl isocyanide was greater than 6.5:1. Fractions from M. flavum 301 reduced acetylene in combination with nitrogenase fractions from Bacillus polymyxa, Klebsiella pneumoniae and Rhodospirillum rubrum , weakly with Azotobacter chroococcum , not at all with Clostridium pasteurianum. Fraction 1 from R. rubrum , reduced acetylene with fraction 2 from M. flavum 301, K. pneumonie, B. polymyxa and A. chroococcum , but not C. pasteurianum .