Record your results after incubation in the table. Why is it important to limit

Question

Record your results after incubation in the table. Why is it important to limit the available types of nutrients in this broth? _________________ The case file gives an example of a digestive system infection caused by a urease-positive organism. What other system or systems could commonly be colonized by urease-positive bacteria? Why? _________________ Urea broth indirectly identifies urease activity by the change in medium pH. How else could urease activity be monitored (consider the case file and the enzyme reaction pathway shown by the equation)? _________________

Explanation / Answer

1. It is important to limit the avilable type of nutrients in the urea broth to allow growth of only urease producing microorganism because urea act as primary source of carbon.

Urea broth is a differential medium that is used to test the organism that produce urease, an enzyme that hydrolyzes urea to ammonia and CO2. The broth contain two pH buffer, urea, phenol red and small amount of nurient for bacteria. Limited nutrients promote growth of only desired micoorganism not the other.

2. Urinary tract other than digestive tract colonized by the urease producing bacteria. Presence of urea, a byproduct of amino acid catabolism, in the urinary tract caused a colonization of urease positive bacteria. Urea is present in urine, a principle nitrogenous waste.

3. Urease activity can be monitered by introducing radiolabeled urea in the broth so when urea hydrolyzed to carbondioxide and ammonia, it contain radiolableled carbon which indicates presence of urease activity.

Proteus vulgaris - Urease positive organism. Pink Colour

E.coli. - urease negative organism. Yellow

Urease test is used to diffrentiate rapid urease positive microorganism to other urease negative or slower urease activity microorganism.

Phenol red is a pH indicator that change in the colour according to medium pH. Intial the broth is yellow in colour , when ammonia is produce from urea , the pH is increase and it gives pink colour. Rapid urease positive microorganism gives bright pink colour whereas slow urease positive microorganism produce partial pink colour.

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