lab 6

Question 1

Different microorganisms are capable of different processes: What are some of those processes

Answer 1

Some are fermenters
Some can use photosynthesis
Some are capable of degrading non-organic material
Some ingest smaller microorganisms

Question 2

How are we are able to differentiate microorganisms?

Answer 2

We are able to differentiate microorganisms based on their ability to perform different biochemical processes

Question 3

Carbohydrate fermentation:Some microorganisms ferment carbohydrates
Give examples:

Answer 3

Remember: MacConkey agar and EMB agar

Question 4

Carbohydrate fermentation: Common fermentable sugars are

Answer 4

Sucrose
Dextrose (D-glucose)
Lactose

Question 5

How do microorganisms breakdown carbohydrates and what is produced? What happens with the product?
The ability to ferment sugar is helpful in what?

Answer 5

• Microorganisms breakdown carbohydrates through glycolysis in order to make ATP
• They then recycle electron carriers using fermentation

-Some microorganisms are very picky about what sugars they use to ferment

-We can use the ability to ferment certain sugars to help identify microorganisms

Question 6

How is a carbohydrate fermentation test performed?

Answer 6

1. Culture microorganisms in medium containing phenol red (a pH indicator) and Sucrose, Dextrose, or Lactose
2. Incubate overnight at 37° C

3.Organisms that can ferment carbohydrates will produce acid, turning the medium yellow

4. Some microorganisms will also produce gas as a byproduct of fermentation. This will cause an air bubble in the tube

Question 7

Positive carbohydrate test is what color?

Answer 7

Yellow

Question 8

Hydrolysis Tests: Some bacteria produce enzymes that can digest extracellular materials.
These materials are usually common barriers to other cells, such as

Answer 8

Casein
Gelatin
Starch
Lipids

Question 9

In a hydrolysis test, when enzymes break down macromolecules, what is produced? What does this determine?

Answer 9

Water

Thus, we can determine whether a microorganism produces these enzymes by whether or not they are able to liquefy media solidified using these macromolecules

Question 10

What are the steps to the starch hydrolysis test?

Answer 10

1. Culture sample on a starch-agar plate with your microorganism

2.Incubate overnight at 37° C

3.Flood plate with Gram’s iodine for 30 seconds. Pour off excess

4. Examine cultures. Cultures which can digest starch will appear clear around the streak. This is because iodine dyes starch.

Question 11

Steps to the gelatin hydrolysis test

Answer 11

1. Make a stab culture in nutrient gelatin tube
2. Incubate overnight at 37° C
3. Examine cultures. Cultures which can digest gelatin will have liquified the media.

Question 12

What does the Triple Salt-Iron Agar test for/differentiates between?

Answer 12

This test differentiates between different types Enterobacteriaceae

Enterobacteriaceae are gram-negative bacilli that can ferment glucose

Differentiation between them is possible by examining differences in carbohydrate fermentation patterns and sulfide production

TSI medium contains 3 carbohydrate sugars (dextrose, sucrose, and lactose), sodium thiosulfate, and phenol red

Question 13

What does TSI medium contains?

Answer 13

TSI medium contains 3 carbohydrate sugars (dextrose, sucrose, and lactose), sodium thiosulfate, and phenol red

Question 14

Red slant, yellow butt, + or – gas production
TSI

Answer 14

Only glucose fermentation occurred

Question 15

Yellow slant, red butt, + or – gas production
TSI

Answer 15

Sucrose and/or lactose fermentation occurred

Question 16

Red slant, red butt, no gas
TSI

Answer 16

No carbohydrate fermentation has occurred.

Question 17

Black butt
TSI

Answer 17

Organism can use sulfur.
Result of H2S production reacting with iron in thiosulfate