n-Dodecane as a substrate for nitrogen fixation by an alkane-utilizingAzospirillum sp.

Azospirillum sp. ANK-BI-11 was isolated from petroliferous soil. Glucose, nutrient broth, and sugar acids showed better growth thann-alkanes under aerobic conditions. The utilization of glucose was inhibited in the presence ofn-hexane. Microaerobically, succinic acid, pyruvic acid, and lactic acid were the best C-sources for acetylene reduction, whereas glucose was the best source for growth.n-Dodecane, a nonconventional C-source, also showed good response towards acetylene reduction, although growth was not so pronounced here as with glucose but was equal to that of Na-succinate. Optimum pH and temperature for acetylene reduction were between 7.0 and 8.0 and 30°C, respectively. Scanning electron microscopic studies revealed structural alteration in the shapes and sizes of the cells ofAzospirillum sp. when grown onn-hexane andn-dodecane compared with the cells grown on glucose.