CHARACTERIZATION AND MORPHOLOGICAL STUDY OF AZOTOBACTER SP. STRAIN
YANA EVSTATIEVA
Department of Biotechnology, Faculty of Biology, Sofia University St. Kliment Ohridski, Sofia, Bulgaria
*Corresponding author: y.evstatieva@biofac.uni-sofia.bg
Keywords: Azotobacter vinelandii, cultivation media, plant growth promoting activity, antifungal activity
Abstract: Plant growth promoting rhizobacteria (PGPR) are a group of free-living bacteria that colonize the rhizosphere and contribute to increase growth and yield of crop plants. PGPR possess many traits that make them well suited as biofertilizers and biocontrol agents, such as: rapid growth and utilization of seed and root exudates, colonization as well as multiplication in the rhizosphere. Among the PGPR group, Azotobacter is a free-living N2- fixer diazotroph that has several beneficial effects on the crop growth and yield. It helps in the synthesis of growth regulating hormones like auxins, cytokinin and giberellic acid (GA) and also stimulates rhizospheric microbes, protects the plants from phytopathogens and improves boost up nutrient assimilation.
Strain morphology and cultivation characteristics were investigated with a modification of Ashby’s, Azotobacter and Jensen’s media. Colony forming units per ml were used as main control parameter in the process of cultivation and were measured on Jensen media with bromophenol blue addition. The biochemical profile of Azotobacter sp. strain was determined by API 20NE and API ZYM systems (BioMericux, France). Protease, lipase, amylase productions and phosphate solubilization were investigated of the Azotobacter sp. strain to prove its plant growth promoting activity (PGP-activity). The strain was identified as Azotobacter vinelandii by molecular technique and the antagonistic effect was investigated on fungal phytopathogens Fusarium, Aspergillus, Rhizopus and Penicillium.