Thermoresistance of azotobacter vinelandii ATCC 12837 in defined and dialysed soil media: filtrable forms.

Thermoresistance of Azotobacter vinelandii ATCC 12837 in nitrogen-free (defined) medium and dialysed soil medium was established. These microorganisms showed thermoresistance in the defined medium, but in the dialysed soil medium they were very sensitive to heat. Thermosensitivity in the dialysed soils medium was due to the production of germinal cells (filtrable forms) and not to the presence of any kind of cytoplasmic inclusions such as poly-beta-hydroxybutyric acid, metachromatic, glycogen or unstaining granules.