Quiz 2

Question 1

Name 3 of the 5 sugar tests for fermentation in the enterotube test:

Answer 1

• glucose
• lactose
• arabinose
• adinotol
• sorbitol

Question 2

What is the color change in fermentation of sugars? What causes the color change?

Answer 2

• red(-) -> yellow (+)

- change in pH more acidic causes change in color

Question 3

Simple staining vs differential staining

Answer 3

• simple: helps differentiate a bacteria and the background

- differentiate : helps differentiate between a cell and other cells

Question 4

What are 2 results of gram staining? Be sure to give 2 characteristics of each result and explain why it occurs.

Answer 4

• Gram +: purple stain, thick peptidoglycan, cell wall retains primary stain of crystal violet
• gram -: red stain, thin peptidoglycan, cell wall does not retain primary stain of crystal violet but retains safaranin

Question 5

Why gram stain not methylene blue stain

Answer 5

-gram stain can differentiate between 2 types of cells and is retained by cell walls while methylene blue is not.

Question 6

gram positive vs gram negative

Answer 6

gram positive: purple, thick peptidoglycan

gram negative: pink, thin peptidoglycan

Question 7

What is the purpose of a capsule? When staining a bacteria with a capsule which part is stained?

Answer 7

A capsule: adheres to surfaces and is a protective coat

-staining is of the background AND CELLS but NOT the capsules

Question 8

Name the two major spore forming genera

Answer 8

Bacillus

Clostridium

Question 9

Explain the difference between differential and selective agar. Provide an example of selective-differential agar.

Answer 9

• selective: inhibits/supports growth of certain types of bacteria
• differential agar: shows an observable change with dye for specific biochemical reactions
  ex. MacConkey Agar

Question 10

Which of the 5 tests requires a reagent added to it after the incubation period? What molecule for this test yields a positive result?

Answer 10

• VP

- acetone

Question 11

What changes the citrate chamber from green to blue?

Answer 11

alkaline metabolites

Question 12

MacConkey agar supports what and inhibits what

Answer 12

supports gram (-) and inhibits gram (+)

Question 13

Define obligate anaerobe, obligate aerobe, and facultative organism?

Answer 13

• obligate anaerobe: organism only grows absence of O2
• obligate aerobe: organism only grows in presence of O2
• facultative: organism can grow in the presence or absence of O2

Question 14

What causes the change in color in an enterotube?

Answer 14

utilization of a substrate