Salt tolerance of Azospirillum brasilense.

The effect of various salts on the growth and N2-ase activity of Azospirillum brasilense was tested. Bicarbonate was found to be the most toxic, followed by chlorides and sulphate. Tolerance of A. brasilense to these salts was comparable to that of many species of Rhizobium. SO4-- was stimulatory to growth and N2-ase activity up to 40 meq. The process of N2-fixation (N2-ase activity) was found to be more sensitive to all the salts tested as compared to growth.