Identification of Azotobacter Species by Fluorescence and Cell Analysis

Summary: Eight strains of Azotobacter agile and A. vinelandii were studied for their ability to elaborate water soluble compounds with a fluorescence that would characterize each when observed under ultraviolet light of 3600 A. It was found that the material produced by A. agile fluoresced white, whereas that produced by A. vinelandii fluoresced green. Additional studies with iron and molybdenum showed that molybdenum enhanced synthesis of fluorescent material in both species and iron appeared to quench the fluorescence. A pH/fluorescence curve for the fluorescent material of each species showed that, although similarities were evident, sufficient difference existed to permit recognition of each. Analyses of dried cell material revealed a much higher protein content in A. agile than in A. vinelandii, but the amount of one of their amino acids, lysine, was essentially the same, on the basis of protein, for each species.