Choose betwenn selective or differential 1 An agar that uses

Choose betwenn selective or differential

1. An agar that uses a high salt concentration to limit the growth of one type of bacteria over another would be considered selective. 2. If an agar contains a dye or pH indicator in the presence of a sugar, it is generally considered selective for those bacteria that may ferment the sugar over those that cannot. 3. An agar that uses the dye in crystal violet agar suppresses the growth of Gram-positive bacteria. This agar would be considered differential. 4. The selective aspect of MacConkey agar allows for the determination of which bacteria are lactose fermenters and which are not. 5. A blood agar plate contains sheep red blood cells and allows for the determination of hemolytic capabilities for all bacteria that grow on the agar. This would make this type of agar differential. 6. EMB agar uses lactose and two dyes that allow it to be differential between the blue-black colonies of E. coli and the pinkish colonies of all other enteric bacteria. 7. Bile salts in MacConkey agar allow for the agar to be selective for the growth of enteric Gram-negative bacteria over Gram-positive bacteria. 8. An agar that allows for the distinction of bacteria based on metabolism would be considered differential.

Solution

1. An agar that uses a high salt concentration to limit the growth of one type of bacteria over another would be considered selective. 2. If an agar contains a dye or pH indicator in the presence of a sugar, it is generally considered differential for those bacteria that may ferment the sugar over those that cannot. 3. An agar that uses the dye in crystal violet agar suppresses the growth of Gram-positive bacteria. This agar would be considered selective. 4. The differential aspect of MacConkey agar allows for the determination of which bacteria are lactose fermenters and which are not. 5. A blood agar plate contains sheep red blood cells and allows for the determination of hemolytic capabilities for all bacteria that grow on the agar. This would make this type of agar differential. 6. EMB agar uses lactose and two dyes that allow it to be differential between the blue-black colonies of E. coli and the pinkish colonies of all other enteric bacteria. 7. Bile salts in MacConkey agar allow for the agar to be selective for the growth of enteric Gram-negative bacteria over Gram-positive bacteria. 8. An agar that allows for the distinction of bacteria based on metabolism would be considered differential.

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