Isolation, characterization and morphological study of Azotobacter isolates

Abstract

Among the diazotrops, great attention has been paid to the genus Azotobacter and its role in increasing the growth and health of plants. In the present study, forty two strains of Azotobacter were isolated from soil. These strains were purified and characterized through microscopical and biochemical test for cell shape, pigmentation, colony size, Gram reaction and catalase activity were identified as Azotobacter sp These strains showed wide variability to these characters. Among 42 isolates, 7 were single cocci, 7 coccidal chain and 4 were cocci in clumps. Majority of isolates i.e. 24, were small, medium and large rod shaped. Thirty two isolates were Gram -ve, catalase positive and 10 were Gram +ve, catalase negative. Finally from these isolates, twenty two were confirmed as Azotobacter strains on cyst formation. The carbon-source utilization pattern revealed that out of 22 strains that 16 strains resembled the characters of A. chroococcum, 3 matched with A. vinelandii and 3 with A. beijerinckii. All 22 isolates were analyzed for its nitrogen fixing ability by using Microkjeldhal method. The highest amount of N 2 (18.88 mg g -1 sucrose) was fixed by Azo-SBT 72 while lowest (6.04 mg g -1 sucrose) by Azo-SUR 25 strain. However, injudicious and hazardous use of chemical fertilizers have degraded the soil health and there is need of ecofriendly management of soil by screening and hunting of potential nitrogen fixing strains to protect the soil environment and health. In this context, biofertilizers hunting natural environment is the need of soil to ensure better health of future generations.

Isolation and screening of Azotobacter Spp. for plant growth promoting properties and its survival under different environmental stress conditions

“…The isolates were studied for their carbon source utilization. These results confirm that these isolates belong to the genus Azotobacter [15].…”

Phenetic and Molecular Diversity of Nitrogen Fixating Plant Growth Promoting Azotobacter Isolated from Semiarid Regions of India

“…The highest amount of N 2 was fixed by Azo1 while the lowest by Azo22. Upadhyay et al [13] reported the amounts of N 2 fixed by different Azotobacter strains ranged from 18.88 to 6.04 mg g -1 sucrose and is in close agreement with the results of N 2 fixation in the present study.…”

“…Isolation of Azotobacter sp. from rhizospheric soils was done by the procedure described by Upadhyay et al [13]. The rhizospheric soil samples collected from the districts of Rajasthan viz.…”

Role and perspective of Azotobacter in crops production

“…The cell morphology is pleomorphic (Upadhyay, Kumar, Singh, & Singh, 2015), usually straight Bacilli with rounded ends becoming more ellipsoidal or coccus (Figure 1). Azotobacter is a chemo-organo heterotrophic organism that forms cysts in under drought stress and produced capsules (Mukhtar, Bashir, & Nawaz, 2018) which structurally consisted of polysaccharide hence the name become exopolysaccharide (Gauri, Mandal, & Pati, 2012).…”