Microbiology Lab Report

MBK – Lab Report Name: Adalberto Pereira Moya

Section: Module 05

Carbohydrate Fermentation Testing

Preparation of Bacterial Cultures:

Incubate the tubes at 35°C - 37°C for 12 hours. Record your observations. Do not let the cultures incubate for more than 24 hours as you may not get an accurate result!

Questions:

A. What is fermentation?

Fermentation is a process of energy production for cells under anaerobic conditions.

B. Why it is important not to incubate the fermentation tubes beyond 24 hours?

To avoid the risk of having inaccurate results. With more that 24hrs the color might change and we may have a false negative.

C. Why phenol red is added to the fermentation tubes?

Phenol red functions as a pH indicator.

D. Why do bacteria have differences in the carbohydrates they can ferment?

Not all bacteria can ferment all fermentable carbohydrates. The type of carbohydrate a bacterium can ferment depends on the presence of enzymes needed for that particular carbohydrate.

E. Why does the formation of yellow color indicate fermentation?

Phenol red pH indicator will turn yellow below pH 6.8 (there was acid production)

F. What information can be gained by running a fermentation series on a particular microbe?

According to the lab book, in a fermentation series, each medium has a single fermentable carbohydrate added to a peptone broth. By running a fermentation series, the ability of certain bacteria to use carbohydrates as a carbon source can be tested.

G. What does a dark pink or red color indicate?

Dark pink color indicates an alkaline o basic metabolic product. In this case, the bacterium utilized the peptone instead of the sugar. The result is interpreted as a negative fermentation.

H. What is the source of the air bubble that may form in the Durham tube?

Gas produced as a result of the fermentation process.

I. Based on your results, what is the carbohydrate...