Dinitrogen fixation (C2H2 reduction) by bacterial strains at various temperatures

Abstract

Acetylene-reducing activities (ARA) of strains ofEnterobacter agglomerans, Azospirillum brasilense, Azotobacter chroococcum, and Bacillus, isolated from temperate or tropical soils, were compared at different temperatures to study temperature adaptability. All Enterobacter strains and Bacillus strain C-11-25 reduced C2H2 at temperatures as low as 5°C. ARA by Enterobacter strains declined sharply above 30°C but ARA by Bacillus strain C-11-25 continued to increase with an increase in temperature.A. brasilense strain sp 245, isolated from wheat roots in Brazil, reduced more C2H2 at lower temperatures than strain Cd, isolated from a Californian soil. Similarly, the temperate strain ofA. chroococcum was a better N2 fixer than the tropicalA. chroococcum strain at lower temperatures. Tropical strains ofA. brasilense andA. chroococcum reduced more C2H2 than temperate strains at higher temperatures. Therefore, it appears that temperate and tropical N2-fixing organisms adapt themselves to their particular environment and should have more potential to benefit crops grown at the particular temperatures favorable to them.