A novel type of mutant of Azotobacter vinelandii that fixes nitrogen in the presence of tungsten

We have isolated a novel type of mutant strain of Azotobacter vinelandii designated strain WN101 that does not fix nitrogen in the presence of molybdenum but in the presence of tungsten. WN101 produced about twice as much hydrogen as the wild-type strain OP but its production of ethylene from acetylene was less than ten percent of that by OP.