Lab 5-3 Phenol Red

What are the possible end products of fermentation? Which ones are we detecting in this experiment?

Acid, Gas or Alcohol. For this experiment we are looking for an acid environment and gas production indicating fermentation occurred.

What is the major benefit for an organism to be able to perform this metabolic process, fermentation ?

Bacteria can live in an oxygen free environment, and they will not die. No oxygen is needed for fermentation to occur

What are the three bacterias we inoculated?

E.coli, S. epidermidis, P. aeruginosa

Explain what fermentation is.

Fermentation is a catabolic pathway used for bacteria to make ATP. First the bacteria hydrolyze disaccharides into monosaccharides (glucose). After glucose is broken down by the process called glycolysis. In glycolysis contains two phases to make the end product of fermentation. In the energy investment phase, glucose is broken down into pyruvate. The next phase is the energy payout phase, in the process of glycolysis, the electrons released from glucose are picked up by electrons carriers which then transport them into pyruvate. Pyruvate is then metabolized making the end-product acid, gas, alcohol and 2 NADH.

What enzymes do the bacteria produce to hydrolyze lactose? and what are they hydrolyzed too?

Galactosidase and the enzyme hydrolyzes lactose into Glucose & Galactose.

All members of the Enterobacteriaceae family are known for their ability to ferment the carbohydrate:

Glucose

What is the driving force of fermentation?

Glycolysis

RESULTS: Explain what occurs if your media turns pink in color. Is this a + or - result?

If the media turns pink, then it's indicating a basic environment. The only thing that happened is organism digest casein and produced ammonia waste. That concludes it's a negative result for fermentation.

What is the purpose of the uninoculated control in this test (we use a plain Lactose Broth)?

In this lab, we get multiple colors in our tube. The control color is a light red color. We use the control to compare the color of the other test tubes if we are not sure what color result was received in the inoculated tubes.

RESULTS: Explain what occurs if your media turns Yellow in color and air bubble present. Is this a + or - result?

It is positive for fermentation. Bacteria was able to ferment it quickly. REMEMBER: Yellow and air bubble (gas) is what we want to see for positive results.

What two ingredients are used as indicators for lab 5-3? What are they detecting?

Phenol Red is the pH indicator (yellow/acid) and gas bubble in the Durham tube is our second indicators for this experiment. Both are detecting if fermentation occurred.

RESULTS: Explain what may have occurred if your media turns orange in color. Is this a + or- result?

Slow fermentation or Cellular Respiration occurred if an orange color is present. If we Incubate the media longer, we could confirm if fermentation really happened. Since our indicator is yellow for positive result, I conclude it is negative for fermentation even though it could possibly be slow fermentation occurring.

What enzymes do the bacteria produce to hydrolyze sucrose? and what are they hydrolyzed too?

Sucrase and the enzyme hydrolyzes sucrose into glucose & fructose.

What ingredients are we using for phenol red?

Sugar ( Glucose, lactose and sucrose), Phenol red (pH indicator) and Casein Digest (digestive protein/peptone)

What is the purpose of adding a Durham tube to your culture? Does the Durham tube make this experiment selective or differential.

The purpose of adding the durham tube is to see if fermentation occurred. The Durham tube make the experiment differential because we visually see an air bubble trapped in the durham tube. Gas is one of the end-products of fermentation.

What is the purpose of phenol red experiment?

To test if bacteria are capable of fermenting the carbohydrates glucose, lactose and/or sucrose.

What would be problematic not having enough carbohydrate in the broth?

Yes, it would be problematic because sugars are one of the most important components for fermentation to occur. If not enough carbohydrates present then less production of ATP can occur or fermentation can occur at a very slow rate or we wouldn't be able to see the gas nor fermentation.

What is glycolysis?

breakdown of glucose into pyruvate

Glycolysis two phases are

energy investment phase and energy payoff phase

Which monosaccharides are found in lactose?

galactose and glucose.

Which monosaccharides are found in sucrose?

glucose and fructose.

Fermentation definition

partial oxidation of a sugar which results in the end product acid, alcohol, gas and 2 NADH