What types of bacteria can the carbohydrate utilization test and MacConkey agar be used to differentiate?

Question

What would a positive and negative result look like for each test?

Answer 1

you are testing to see which sugars the organism ferments, and thus use this for your identification. macconkey agar is an example of this. the sugar present is lactose. a lactose fermenter (such as e.coli) would cause a color change in the indicator found in the agar, arising in colonies of a dark pink color. a non-fermenter (such as pseudomonas aeruginosa) would not cause the indicator to change color, and the colonies would thus be the same color as the agar (referred to as colorless).

one caveat: while a non-lactose fermenter can never be a lactose fermenter, a lactose fermenter can be found as a non-lactose fermenter. in this situation, e.coli would be colorless on the macconkey agar. then other differential chemical testing would need to be performed.

Answer 2

No, But i did try and many times to eat soup with a spoon, especially if a soup is thick (you can thicken the soup effectively by adding some flour). It takes more time, so I enjoy it longer