MIDTERM 2 Acid and Gas Production from Sugar Fermentation Flashcards
What is the most effective way to detect acid production?
using acid-base pH indicators
What is contained in the sugar fermentation medium?
- A single sugar as the only source of carbon
- a pH indicator to indicator any acid production
- Durham tube
What pH indicator is used for Sugar Fermentation? and what are the certain pH numbers in which the colors are exhibited?
Phenol red
Red above pH of 8.5
Yellow at pH below 6.9
Why doesnt it require a lot of acid to bring the pH below 6.9 in the sugar fermentation medium?
The pH of the autoclaved broth is only slightly alkaline at pH 7.4
Since the transitional colors are difficult to differentiate, what must we use in sugar fermentation?
we have to use standard diagnostic procedures to dictate that a test should be positive only upon complete color change and any partial color change is scored as negative
What is the Durham tube used for?
detection of gas production
How does a Durham tube work?
a microbe produces gas as a result of fermentation, and it will dissolve in the medium until saturation is reached. Once the medium is saturated and gas can no longer dissolve, itll rise into the durham tube.
How to determine gas production test?
Any bubbles in the durham is positive no matter the amounts
Why is it important to check for bubbles in durham tube before you innoculate
because if there is bubbles, it can be accounted for as a false positive
True or false: its possible for your organism to score positive for acid production but negative for gas production in the fermentation test. Why?
True, Acid can be produced but the gas may be produced in such small amounts that it did not saturate the medium enough for the gas to be insoluble.
True or False: its possible for your organism to score positive for gas production but negative for acid production. If false, Why
False, its very unlikely because production of gas means the organism is a fermenter. and if its a fermenter, it will 100% produce acid.
