Question

Microbiology

Q1

One organism that is positive for citrate is

Q2

Q3

Answer 1

Question 1

Answer: Citrate test is used to determine the ability of an organism to utilize citrate as sole source of energy and carbon. Klebsiella pneumonia is a bacteria that is positive for citrate.

Question 2

Answer: Methyl Red test is used to determine the ability of an organisms to ferment glucose and produce stable acid products end products such as lactic acid and acetic acid. Production of acid lowers the pH of the medium. The organisms are first incubated in glucose media. Later, methyl red is added to the media. If stable acidic end products are produced and the pH remains at around 4.6, the broth remains red. Hence, the broth that contain methyl red positive organisms remain red. Organisms that do not produces stable acid products increases the pH of the media to 6.2. This leads to change in the color of the methyl red from red to yellow. Hence, the broth that contain methyl red negative organisms will appear negative.