A New Species of Azotobacter producing Heavy Slime and Acid

Abstract

IN the course of an investigation on the geographical distribution of the Azotobacteriaceae¹ in various types of soil in India, a nitrogen-fixing organism has been isolated from a sample of red soil from Pattambi (Madras) by Winogradsky's silica-gel plate technique and purified by dilution platings. This new bacterium differs in certain morphological and physiological characteristics from known species of Azotobacter (including Beijerinckia)¹. The cells are oval in shape, occur mostly in pairs and packets and sometimes singly, measuring on an average 1.2–2.2µ × 2.3–4.6µ (Fig. 1). The cells do not change their shape even on prolonged incubation in Ashby's nitrogen-free liquid medium with different carbohydrates. The bacterium encysts after 30 days incubation at 30° C. in the solid mannitol medium without calcium carbonate. The optimum temperature for growth was found to be about 30° C.