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10 Cards in this Set
- Front
- Back
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What is MacConkey's Agar? |
It is a specialized Bacterial medium which is both selective and differential. Designed to differentiate enterics. |
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Why selective? |
Because it allows growth of gram negative bacteria and inhibits gram positive bacteria. |
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How? |
It contains Crystal violet and bile salts that inhibit the growth of gram positive bacteria. |
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Why differential? |
Because it differentiate between lactose fermenters as pink and non fermenters as colorless colonies. |
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How? |
It contains neutral red which turns pink at pH below 6.8 and colorless at pH above 6.8 |
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What causes the pH changes? |
Lactose fermenters utilize lactose and produce acid which lowers the pH, hence pink. Lactose non-fermenters utilize peptone and produce ammonia which increases the pH, hence colorless. |
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Eg. of lactose fermenters? |
E.coli, Enterobacter, Klebsiella. |
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Eg. of lactose non-fermenters? |
Salmonella, Proteus, Pseudomonas aeruginosa, Shigella. |
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A quick composition? |
Sure, why not. It contains peptone, proteose peptone, lactose, bile salts, sodium chloride, crystal violet, neutral red and of course water and agar. |
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Any last note? |
Yeah, do visit my site http://microamaze.blogspot.in/ for similar flash cards if you found this helpful. |
