Question

biol 2120 differential and selective media homework fill in the missing word(s) in each sentence. 21. emb agar contains the dyes __ and , which inhibit gram - positive organisms. 22. on mac agar, a colorless colony means the organism does not ferment . 23. hek agar uses salts to inhibit non - enteric bacteria. 24. a positive bile esculin reaction results in color change due to esculin hydrolysis. 25. msa differentiates organisms based on their ability to ferment . 26. staphylococcus aureus can be differentiated from s. epidermidis using msa because s. aureus ferments , causing a yellow color. 27. a green metallic sheen on emb suggests strong lactose fermentation typically by (genus and species). 28. on hek, black precipitate indicates the organism reduces . 29. organisms that grow on mac but do not turn pink are likely non - fermenters. 30. selective media help isolate organisms by __ the growth of others.

Explanation:

1. EMB agar contains eosin and methylene blue dyes which inhibit Gram - positive organisms.
2. On MAC agar, a colorless colony means the organism does not ferment lactose.
3. HEK agar uses bile salts to inhibit non - enteric bacteria.
4. A positive bile esculin reaction results in a black color change due to esculin hydrolysis.
5. MSA differentiates organisms based on their ability to ferment mannitol.
6. Staphylococcus aureus can be differentiated from S. epidermidis using MSA because S. aureus ferments mannitol, causing a yellow color.
7. A green metallic sheen on EMB suggests strong lactose fermentation typically by Escherichia coli.
8. On HEK, black precipitate indicates the organism reduces sulfur.
9. Organisms that grow on MAC but do not turn pink are likely non - lactose fermenters.
10. Selective media help isolate organisms by inhibiting the growth of others.

Answer:

1. eosin, methylene blue
2. lactose
3. bile
4. black
5. mannitol
6. mannitol
7. Escherichia coli
8. sulfur
9. lactose
10. inhibiting