Exam 2 Objectives 1 Flashcards
difference between fermentation and anaerobic respiration
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)
Indicate the function of cytochrome c oxidase in a bacterial cell.
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.
Understand why all aerobic bacteria are not oxidase positive.
Some bacteria are capable of aerobic respiration but have a different terminal oxidase system and give a negative result for the oxidase test.
the gain of electrons or a decrease in oxidation state by a molecule, atom, or ion.
reduction
the loss of electrons or an increase in oxidation state by a molecule, atom, or ion.
oxidation
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).
oxidase
Enzyme that catalyzes the decomposition of hydrogen peroxide to water and oxygen.
catalase
Peroxidases are the plant enzymes that use peroxide to break down bacteria and other harmful material. They are located in the granules of neutrophils.
peroxidase
why aerotolerants would not use catalase
They do not use oxygen, so they have no need to use catalase to convert hydrogen peroxide into water and oxygen.
Identify sources of error that might produce false positives in the oxidase test.
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.
Explain the function of zinc in the test for nitrate reduction
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.
Understand the purpose of a durham tube in the nitrate test.
Tests for the presence of gas
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
The source of the gas is unknown
Understand the relationship between the enzyme nitrate reductase and anaerobic respiration
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.
a gram negative, aerobic or facultative anaerobic rod which produces gas from lactose within 48 hours. The presence of some coliforms indicate fecal contamination.
coliform
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
Enterobacteriaceae
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
enterics
Identify the group of organisms which can be differentiated by the IMViC tests.
coliform
Understand why itis necessary to repeatedly vortex the VP testover30 minutes before assigning a negative result.
to oxygenate it
Know what IMViC stands for,
Indole test, Methyl red test, Voges-Proskauer test, Citrate utilization test
Identify the two abilities required for an organism to be citrate-positive.
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
Identify the two enzymes that citrate positive organisms have that allow them to grow in this medium.(
citrate permease and citrate lyase
why citrate negative organisms will not grow on Simmons Citrate medium.
bacteria that do not possess citrate permease will not grow on this medium
Understand why a light inoculum is used for the citrate test.
to avoid confusion between actual growth and heavy inoculum, which may appear as growth
understand why a citrate test in which the organism has grown, but has not changed color is still considered a positive test
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
SIM medium is used to differentiate what group of organisms?
Enterobacteriaceae
the 3 tests contained within SIM medium
sulfur reduction (S), indole production form tryptophan (I), and motility (M)
Understand why indole is the preferred product to test for the presence of tryptophanase.
the formation of red color in the reagent layer indicates a positive reaction and the presence of tryptophanase; no red color is indole negative
how the medium is designed to show motility
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
Understand how to differentiate true motility from movement of the needle during the stab.
growth that that radiates in ALL directions and appears slightly fuzzy throughout the tube is an indication of motility
