Micro

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. Enrichedmedia

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support the growthof most organisms without fastidious growth requirements. (eg. Bloodagar, Chocolate agar, Mueller-Hinton agar, Thioglycolate broth, Sabourauddextrose agar)

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Selective media

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A selective medium hasagents added which will inhibit the growth of one group of organisms whilepermitting the growth of another. For example, Columbia CNA agar has the antibiotics colistin and nalidixic acid added which inhibit the growth of Gram-negative bacteria but not the growth ofGram-positives. It is, therefore, said to be selective for Gram-positiveorganisms, and would be useful in separating a mixture of Gram-positive andGram-negative bacteria.

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Differential media

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A differential medium contains additives that cause an observable color change in themedium when a particular chemical reaction occurs. They are usefulin differentiating bacteria according to some biochemical characteristic. In other words, theyindicate whether or not a certain organism can carry out a specific biochemicalreaction during its normal metabolism. Many such media will be used infuture labs to aid in the identification of microorganisms.r}ԋCl

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Selective + Differntial media

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. Combination of selective and differentialmediaA combination selective and differential medium permits the growth ofone group of organisms while inhibiting the growth of another. In addition,it differentiates those organisms that grow based on whether they can carryout particular chemical reactions. (eg. MacConkeyagar, Mannitol Salt agar)

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Differential stain

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The Gramstain is the most widely used staining procedure in bacteriology. It is calleda differential stain since it differentiates between Gram-positive andGram-negative bacteria. Bacteriawhich stain purple with the Gram staining procedure are termed Gram-positive;those which stain pink are said to be Gram-negative.}ԜVl