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Isolation of Azotobacter from Soil Sample
To isolate azatobacter from soil sample by serial dilution technique.
Soil is the natural habitat of different microorganisms. The quality and quantity of microbes depends upon the physiochemical characteristics of soil profile.
According to Alexander, the values of viable plate count in the fertile soil have been reported as 10 to the power of 8 to 10 bacteria, 10 to the power of 6 to 8 Actinomycetes and 10 power 4 - 6 fungal spores/gm of dry soil. Plate count enumeration is based on selection of a particular class of organisms through the presence or absence of specific nutrients (or) inhibitors placed in the nutrient medium.
Soil sample, sterile distilled water, sterile pipettes, sterile petriplates , Ashaby's medium.
Ashbay's medium is prepared and sterilised in an autoclave. About 15-20 ml of Ashbay's medium is poured into each sterile petriplate under asceptic conditions and allowed to solidify. 10 fold serial dilution of the soil smaple is prepared by taking 1 gm of soil sample into 10 ml of sterile distilled water and mixed well to get soil suspension. 1ml of a soil suspension is diluted with 9ml of sterile distilled water asceptically to get 10 power -1 dilution. Further 1ml of suspension from 10 power -1 dilution is attained aseptically transferred to 9ml of sterile distilled water making the dilution 10 power -2. Similarly higher serial dilutions upto 10 power -8 are made separately for each soil sampel. 0.1 ml of soil suspension from 10 power -3 to 10 power -8 are inoculated into sterile nutrient medium plates. The samples are spread uniformly, throughout the petriplates and then inoculated petriplates are incubated at 37 degree celcius fro 24 hrs for the isolation of bacteria. Duplicates are also maintinaed fro each dilution.
Large raised mucoid colonies were observed.