Abstract
Summary
Calcium ion requirements of strains representing 5 species of the Azotobacteriace have been studied. Quantitative differences in growth response on molecular nitrogen and on urea-N were readily detected with strains of A. vinelandii and A. chroococum and less definitely with A. beijerinckii and possibly A. macrocytogenes. No specific requirement for calcium was detected with strains of A. agilis, and the ion inhibited growth of A. indicus on either source of nitrogen. Acetate and ethanol replaced the calcium required for nitrogen fixation by 3 strains of A. vinelandii tested.
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