Answer :
Final answer:
If E. coli cells are streaked onto skim milk agar plates and incubated for 24 hours, they would likely produce a white precipitate around the colonies. This is because E. coli can break down casein, a protein in milk, forming a white precipitate.
Explanation:
Streaking E. coli cells onto skim milk agar plates and incubating them for 24 hours would likely result in the formation of a white precipitate around the colonies. Skim milk agar contains casein, a protein found in milk which certain bacteria, including E. coli, can break down by proteolysis, resulting in a white precipitate.
Moreover, these colonies provide visible evidence to confirm the presence of E. coli cultures. The colors of the colonies, in this case, white, vary in accordance with the type of bacteria and their metabolizing capabilities. The white colonies specify E. coli's metabolic activity involving the digestion of milk proteins present in the agar.
Thus in your scenario, we would expect the E. coli bacteria to provide a white precipitate around the bacterial colonies on the skim milk agar plate.
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Final answer:
No, because E. coli does not produce the enzyme caseinase to break down casein in skim milk agar.
Explanation:
If E. coli cells were streaked onto skim milk agar plates and incubated for 24 hours, you would not expect to find a white precipitate in the medium around the cells.
Skim milk agar is a differential medium commonly used in microbiology to detect the presence of the enzyme caseinase, which allows bacteria to break down casein protein present in milk.
E. coli does not produce caseinase, so it would not be able to break down the casein in the skim milk agar, resulting in no white precipitate.
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