NITROGEN FIXATION IN A MUTANT OF AZOTOBACTER VINELANDII

Abstract

Ultraviolet irradiation of A. vinelandii gave a mutant with a metabolic block in its glucose-utilizing system that caused a marked change in the nitrogen-fixing properties of the organism. The mutant was unable to grow on N2 with sucrose or glucose as the C source, but was readily able to do so when given pyruvate, lactate or various Kreb''s cycle acids. The mutant would grow on any of these C sources when supplied with ammonia. Accordingly, the defect in the mutant affected a reaction associated with N fixation rather than with ammonia utilization, and an experimental approach has been opened for identifying the metabolic reaction or reactions that drive N fixation in the Azotobacter.