Microbiology Task 4

Microbiology Lab

August 5, 2013

WGU Microbiology

When there is no oxygen present fermentation occurs and this is the production of ATP. During this

experiment S. cerevisiae and S epidermis were used. My S cerevisiae fermented all 3 carbohydrates

used.

Glucose (AG)

Fructose (AG)

Mannitol (-)

My S. epidermis

Glucose (AG)

Fructose (AG)

Mannitol (A)

If you incubate longer than the 24 hours, the samples could possibly change color and you would have

altering results for your experiment. For instance it could show a positive result when it was really a

negative result in the beginning.

When we add phenyl red to our tubes it functions as a pH indicator. So it will turn a pink color if it is

alkaline . Meaning the pH solution is 7.4 or higher, and yellow coloring if it is acidic with a pH of 6.8 or

lower. It can also be used as a medium to show results of gram negative enteric bacteria. If you get a

solution that is yellow it is telling you that an acid end product was formed and the bacterium used the

carbohydrate. If it did not use the carbohydrate the end product will be ammonia and the solution will

be yellow.

Several carbohydrates can be fermented