Final answer:
The broth turning pink in a urease test indicates urea has been hydrolyzed, showing a positive test for urease-producing bacteria. This process involves the breakdown of urea into ammonia and carbon dioxide, raising the medium's pH, which is then detected by the pH indicator phenol red.
Step-by-step explanation:
The statement 'The broth will change to pink indicating urea has been hydrolysed' refers to the urease test, a biochemical test used in microbiology to differentiate organisms based on their ability to hydrolyze urea using the enzyme urease. When organisms that produce urease are inoculated into a medium containing urea, such as urease broth, and incubated, they hydrolyze the urea into ammonia and carbon dioxide. The release of ammonia increases the pH of the medium, which is detected by the pH indicator phenol red. A significant pH increase will turn the broth pink, indicating a positive urease test result.
This test is essential for identifying bacteria, especially those belonging to the genus Helicobacter and Proteus, and it also has clinical implications in diagnosing infections caused by these organisms. Urease activity can affect the kidney by promoting the formation of ammonia, which can increase the pH of urine as well. If urease-producing bacteria are present in the urinary system, they can contribute to the formation of struvite kidney stones.
The presence of phenol red in the broth serves as an acid-base indicator which changes color according to the pH of the solution. Similar to phenolphthalein, these indicators provide a visible cue that can indicate the enzymatic activity and the corresponding pH change in the medium.