In the urea broth test, the pH indicator in the broth is phenol red. The initial colour of the broth (before any bacterial growth) is light orange. If the broth turns bright pink or fuchsia after bacterial growth, your unknown bacteria test positively. 1-1 What pH range turns phenol red into bright pink or fuchsia color? Acidic, neutral, or alkaline?
1-2: What compound is made by the bacteria that turns the pH?
1-3: Urea broth contains urea as part of its components. If the unknown bacteria turns the color of the broth to fuchsia, what exoenzyme is being produced by the bacteria?
1-4: What is the substrate for the enzyme in question 3? What are the products ofthis exozyme?
2. In a sulfide production test (part of SIM test), what is the color of a positive test? If the culture is positive, what substance the bacteria produce to generate the color?
3. Your unknown bacteria turn SIM agar to black in color. The bacteria are turning some substance in the SIM agar to make H2S, which combines with ferrous ion to make the black ppt. Please name two substances in the SIM agar that can be turned into H:S by your bacteria.
4. If a bacterium can use thiosulfate ion to make H:S, and thus is tested positive in SIM test, this bacterium must have which of the following metabolic pathway: fermentation, aerobic respiration, or anaerobic re spiration?