screening.pptx

screening

1. SCREENING

2. SCREENING Both isolating and detecting high yielding micro-organisms from natural sources such as soil, water etc. from heterogeneous population of microbes is called screening.

3. PRIMARY SCREENING Some elementary tests are done to detect and to isolate new microbial species with desired property. They serve to remove worthless micro-organisms. Most important spicies are isolated. Used in industries.

4. CROWED PLATE TECHNIQUE

5. CROWED PLATE TECHNIQUE

6. AUXANOGRAPHY This technique is largel employed for detecting micro-organisms able to produce growth factors. Two major steps oh the technique are:

7. AUXANOGRAPHY

8. AUXANOGRAPHY Agar in the first plate as prepared in step A is carefully lifted out with the help tweezers and a spatula and placed without inverting on the surface plate as prepared in step B. The growth factor produced by colonies present on the surface of the first layer of agar can diffuse into the lower layer of agar containing the test organism. The zones of stimulated growth of the test organism around the colonies is an indication that they produce growth factor. Productive colonies are sub cultured.

9. ENRICHMENT CULTURE TECHNIQUE This technique was designed by soil microbiologist BEIJERINCK to isolate the desired micro organisms from heterogeneous microbial population present in soil. Medium is adjusted to favor the growth of the desired micro-organisms. Unwanted micro-organisms are eliminated. This technique has become a valuable tool in many screening programmes meant for isolating industrially important strains.

10. USE OF AN INDICATOR DYE The pH indicating dyes may be employed in some screening methods for detecting micro-organisms capable of producing organic acids, since a pH indicating dye under goes colour changes according to its pH . Such dyes are neutral red in colour and is added to poorly buffered nutrient agar media.

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