Exam 2 Objectives 1

Question 1

difference between fermentation and anaerobic respiration

Answer 1

fermentation
-no ETC=make less ATP (2), organic FEA (pyruvate)
-regeneration of NADH
anaerobic respiration
-FEA is not O2 but sulfate, carbonate, ETC=less ATP (15)

Question 2

Indicate the function of cytochrome c oxidase in a bacterial cell.

Answer 2

It is the last enzyme in the chain, Complex IV, and is so named because it makes the final electron transfer of the chain from cytochrome c, residing in the periplasm, to the oxygen inside the cell.

Question 3

Understand why all aerobic bacteria are not oxidase positive.

Answer 3

Some bacteria are capable of aerobic respiration but have a different terminal oxidase system and give a negative result for the oxidase test.

Question 4

the gain of electrons or a decrease in oxidation state by a molecule, atom, or ion.

Answer 4

reduction

Question 5

the loss of electrons or an increase in oxidation state by a molecule, atom, or ion.

Answer 5

oxidation

Question 6

any enzyme that catalyzes an oxidation-reduction reaction involving molecular oxygen (O2) as the electron acceptor. In these reactions, oxygen is reduced to water (H2O) or hydrogen peroxide (H2O2).

Answer 6

oxidase

Question 7

Enzyme that catalyzes the decomposition of hydrogen peroxide to water and oxygen.

Answer 7

catalase

Question 8

Peroxidases are the plant enzymes that use peroxide to break down bacteria and other harmful material. They are located in the granules of neutrophils.

Answer 8

peroxidase

Question 9

why aerotolerants would not use catalase

Answer 9

They do not use oxygen, so they have no need to use catalase to convert hydrogen peroxide into water and oxygen.

Question 10

Identify sources of error that might produce false positives in the oxidase test.

Answer 10

Once the vial has been opened, oxidase reagent will turn purple over time due to oxygen in the air. To avoid false positives, be sure to: 1) use oxidase reagent that is still clear and 2) to read your test quickly once you have performed it.

Question 11

Explain the function of zinc in the test for nitrate reduction

Answer 11

The addition of zinc dust is used to determine if the nitrates were reduced past nitrite stage. If a red color develops after the addition of zinc, the nitrates were not reduced to nitrites. If there is no color after the addition of zinc, the nitrates in the media were reduced beyond nitrites to ammonia or nitrogen gas.

Question 12

Understand the purpose of a durham tube in the nitrate test.

Answer 12

Tests for the presence of gas

Question 13

Understand why the presence of a bubble in the durham tube of a nitrate broth is not definitive for nitrate reduction when working with an organism capable of fermentation

Answer 13

The source of the gas is unknown

Question 14

Understand the relationship between the enzyme nitrate reductase and anaerobic respiration

Answer 14

anaerobic respiration involves the reduction of an inorganic molecule, something other than oxygen, as a final electron acceptor in the ETC. In this case, it is nitrogen that gets reduced and the nitrate reductase is what reduces nitrate to nitrite.

Question 15

a gram negative, aerobic or facultative anaerobic rod which produces gas from lactose within 48 hours. The presence of some coliforms indicate fecal contamination.

Answer 15

coliform

Question 16

Gram negative bacteria. Many live in the gut. They are facultative anaerobes, fermenting sugars to produce lactic acid and various other end products. Most also reduce nitrate to nitrite. Lack cytochrome c oxidase

Answer 16

Enterobacteriaceae

Question 17

Gut flora. They are rod-shaped gram-negative bacteria of the family Enterobacteriaceae; most occur normally or pathogenically in intestines of humans and other animals

Answer 17

enterics

Question 18

Identify the group of organisms which can be differentiated by the IMViC tests.

Answer 18

coliform

Question 19

Understand why itis necessary to repeatedly vortex the VP testover30 minutes before assigning a negative result.

Answer 19

to oxygenate it

Question 20

Know what IMViC stands for,

Answer 20

Indole test, Methyl red test, Voges-Proskauer test, Citrate utilization test

Question 21

Identify the two abilities required for an organism to be citrate-positive.

Answer 21

growth will be visible on the slant surface and the medium will be an intense Prussian blue. The alkaline carbonates and bicarbonates produced as by-products of citrate catabolism raise the pH of the medium to above 7.6, causing the bromothymol blue to change from the original green color to blue

Question 22

Identify the two enzymes that citrate positive organisms have that allow them to grow in this medium.(

Answer 22

citrate permease and citrate lyase

Question 23

why citrate negative organisms will not grow on Simmons Citrate medium.

Answer 23

bacteria that do not possess citrate permease will not grow on this medium

Question 24

Understand why a light inoculum is used for the citrate test.

Answer 24

to avoid confusion between actual growth and heavy inoculum, which may appear as growth

Question 25

understand why a citrate test in which the organism has grown, but has not changed color is still considered a positive test

Answer 25

in most cases, it is because it was not completely incubated
in the absence of color change, growth on the slant indicates that citrate is being utilized and is evidence of a positive reaction

Question 26

SIM medium is used to differentiate what group of organisms?

Answer 26

Enterobacteriaceae

Question 27

the 3 tests contained within SIM medium

Answer 27

sulfur reduction (S), indole production form tryptophan (I), and motility (M)

Question 28

Understand why indole is the preferred product to test for the presence of tryptophanase.

Answer 28

the formation of red color in the reagent layer indicates a positive reaction and the presence of tryptophanase; no red color is indole negative

Question 29

how the medium is designed to show motility

Answer 29

single stab in the medium; motile organisms are able to move about in the semisolid medium and can be detected by the radiating growth extending outward in all directions from the central stab line

Question 30

Understand how to differentiate true motility from movement of the needle during the stab.

Answer 30

growth that that radiates in ALL directions and appears slightly fuzzy throughout the tube is an indication of motility