Final answer:
Stuart's urea broth mainly consists of 8 M urea and 2 M thiourea along with a pH indicator and stabilizing agents that indicate a positive test for urease by turning deep pink.
Step-by-step explanation:
Stuart's urea broth is composed of several chemicals that work together to test for the presence of the enzyme urease in bacteria. The broth's main components include 8 M urea and 2 M thiourea, which serve as the substrates for the enzyme.
In the presence of urease, the urea is hydrolyzed, and ammonia is produced, raising the pH of the broth. This change in pH is indicated by a pH indicator that turns a deep pink color for a positive test result.
Other constituents of the broth may include 5% CHAPS, 2 mM tributyl-phosphine, 0.4% Ampholytes in the pH range of 3-10, and other additives such as 5% PVP 40 for stabilization and consistency.