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Microbiology > Lab Exam 2: Ex. 5-1; 5-2; 5-3 > Flashcards

Lab Exam 2: Ex. 5-1; 5-2; 5-3 Flashcards

1
Q

What are acids that contain the carboxyl functional group called?

A

carboxylic acids

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2
Q

metabolism

A

the sum of chemical reactions within a cell

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3
Q

What do catabolic reactions result in?

A

a decrease in the reactant molecule’s complexity

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4
Q

What do anabolic reactions result in?

A

the product becoming more complex than the reactant.

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5
Q

entropy

A

the measure of disorder that order devolves to.

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6
Q

free energy

A

the potential energy of the bonds within a biochemical

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7
Q

what is a redox reaction? How does it work?

A

an oxidation reaction paired with a reduction reaction.
Reduction occurs when a molecule (called an oxidant) gains one or more electrons, which requires oxidation of another molecule (called reductant) to provide those electrons.

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8
Q

reduction potential

A

the tendency of a molecule to donate electrons, measured in volts

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9
Q

What two ways do heterotrophic bacteria obtain their energy? What type of systems are they?

A

Respiration or fermentation using ingested molecules.
They are both catabolic systems which oxidize the organic molecules and transfer their chemical energy into high-energy bonds in ATP.

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10
Q

What does ATP stand for?

A

adenosine triphosphate

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11
Q

How do respiration and fermentation differ?

A

They differ principally in what final electron acceptor (FEA), which acts as an oxidant, is used; the presence or absence of an electron transport chaing (ETC); and in their ATP yeild.

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12
Q

Which system is characterized by the absence of an ETC (electron transport chain) and use an organic compound as the FEA (final electron acceptor)?

A

Fermentations

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13
Q

Which system uses an inorganic compound and possesses an ETC (electron transport chain)?

A

Respirations

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14
Q

What serves as the FEA (final electron acceptor) in aerobic respiration?

A

oxygen

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15
Q

What serves as the FEA (final electron acceptor) in anaerobic respiration?

A

inorganic compounds such as NO3 or SO4

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16
Q

What process does all fermentation pathways use to make ATP? Where does the energy come from?

A

substrate-level phosphorylation - energy for adding the phosphate comes directly from breaking a bond in a biochemical.

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17
Q

What three pathways are used to make ATP in the respiration process?

A
  1. glycolysis
  2. citric acid cycle (aka krebs cycle)
  3. electronic transport chain which performs oxidative phosphorylation
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18
Q

What does O-F stand for and what is the O-F Test?

A

Oxidation-Fermentation Test

It is a test designed to differentiate bacteria on the basis of fermentative or oxidative metabolism of carbohydrates.

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19
Q

In this medium, what do oxidative organisms oxidize the carbohydrates to?

A

CO2, H2O, and energy

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20
Q

In what order does the O-F Test oxidize carbohydrates?

A

glycolysis, oxidation of pyruvate, citric acid cycle, and finally the electron transport chain (ETC) with oxygen (the FEA) being reduced to H2O

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21
Q

Why does the O-F test include a high sugar-to-peptone ratio?

A

to reduce the possibility that alkaline products from the peptone utilization will neutralize weak acids produced by oxidation of the carbohydrate.

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22
Q

What is the Bromothylmol blue dye for? What colors will it show?

A

it is added as a pH indicator.
yellow at pH 6.0
green at pH 7.1
blue at pH 7.6

23
Q

What type of medium is O-F and what does this allow for?

A

semisolid medium - allows determination of motility

24
Q

What is the medium prepared with?

A

glucose, lactose, sucrose, maltose, mannitol, or xylose (is not slanted)

25
Q

During the O-F test, two tubes are inoculated but one is sealed with a layer of sterile mineral oil. Why? What does it do?

A

To promote anaerobic growth and fermentation - the mineral oil creates an environment unsuitable for oxidation because it prevents diffusion of oxygen from the air into the medium.

26
Q

During the O-F test, two tubes are inoculated, one is sealed with mineral oil and one is not. Why is the one tube left unsealed?

A

to allow aerobic growth and oxidation

27
Q

In the end result of the O-F test, organisms that are able to ferment the carbohydrate ONLY or ferment AND oxidize the carbohydrate will turn the sealed and unsealed media what color?

A

yellow throughout

28
Q

In the end result of the O-F test, organisms that are able to oxidize ONLY will turn the unsealed medium what color? sealed medium?

A

unsealed - yellow (or partially yellow)

sealed - green or blue

29
Q

In the end result of the O-F test, slow or weak fermenters will turn both sealed and unsealed tubes what color?

A

slighty yellow at the top

30
Q

In the end result of the O-F test, organisms that are not able to metabolize the sugar will turn what color?

A

they will either produce no color change or turn the medium blue because of alkaline products from amino acid degradation (deamination)

31
Q

What is the O-F test used for?

A

to differentiate bacteria based on their ability to oxidize or ferment specific sugars.
- it allows presumptive separation of the fermentative enterobacteriaceae from the oxidative Pseudomonas and Bordetella, and the nonreactive Alcaligenes and Moraxella

32
Q

What three microbes did we use for the O-F test? What were the results?

A

Ec (Escherichia coli) - Sealed and unsealed both yellow (oxidation and fermentation or fermentation only.
Af (Alcaligenes faecalis) - Green to blue (No sugar metabolism; organism is nonsaccharolytic)
Kr (Kocuria rosea) - Green to blue (No sugar metabolism; organism is nonsaccharolytic)

33
Q

What is a lactose fermenter?

A

an organism that splits the disaccharide lactose into the monosaccharides glucose and galactose and then ferments the monosaccharides.

34
Q

What is Phenol Red Fermentation Broth?

A

it is a differential fermentation medium composed of standard ingredients (the “base broth”) to which a single carbohydrate is added.

35
Q

In Phenol Red Fermentation what can be determined after inoculation and incubation?

A

an organism’s ability to ferment a particular carbohydrate can be determined, as can the end products of its fermentation.

36
Q

What is included in the Phenol Red medium?

A

peptone, a pH indicator phenol red, and an inverted Durham tube is added to each tube as in indicator of gas production.

37
Q

What colors does the Phenol red produce based on pH?

A

yellow below pH 6.8
pink to magenta above pH 7.4
red in between
(during preparation the pH is adjusted to about 7.3 so it appears red)

38
Q

In Phenol Red Fermentation what causes the medium to turn yellow?

A

acid production form fermentation of the carbohydrates lowers the pH below the neutral range of the indicator

39
Q

How does the Durham tube indicate gas production?

A

Gas production (also called fermentation) is indicated by a bubble, or pocket, in the Durham tube where the broth has been displaced.

40
Q

What causes the pink color result in a Phenol Red Fermentation test?

A

Deamination of amino acids supplied by casein (milk protein) results in an alkaline reaction from the ammonia that is produced. The Ammonia raises the pH and turns the broth pink if no acid is produced or if acid production has ceased due to consumption of the carbohydrate.

41
Q

What microbes did we use in the Phenol Red Fermentation Broth? What was the results?

A

Af (Alcaligenes faecalis) - yellow no bubble (Fermentation of the specific carbohydrate with acid end products; no gas produced, or gas produced in undetectable amounts)
Ec (Escherichia coli) - yellow with bubble (fermentation of the specific carbohydrate with acid and gas end products)
Ps (Providencia stuartii) - yellow no bubble (Fermentation of the specific carbohydrate with acid end products; no gas produced, or gas produced in undetectable amounts)

42
Q

In Phenol Red Fermentation what would the interpretation of the results be if the broth was red with no bubble?

A

no fermentation of the specific carbohydrate or products are not made in detectable amounts.

43
Q

In Phenol Red Fermentation what would the interpretation of the results be if the broth was pink with no bubble?

A

degradation of peptone; alkaline end products

44
Q

What is the Phenol Red Broth (PR broth) used for?

A

to differentiate members of Enterobacteriaceae and to distinguish them from other Gram-negative rods. It also is used to distinguish between Gram-positive fermenters, such as Streptococcus and Lactobacillus species.

45
Q

What does MR-VP stand for?

A

Methyl Red and Voges-Proskauer Tests

46
Q

What is the MR (Methyl Red) test used for?

A

to detect organisms capable of performing a mixed acid fermentation, which overcomes the phosphate buffer in the medium and lowers the pH. (it identifies organisms that perform a mixed acid fermentation and produce stable acid end products.)

47
Q

What do MR-positive organisms do?

A

lower the broth’s pH permanently

48
Q

What is the VP (Voges-Proskauer) test used for?

A

to identify organisms that are able to ferment glucose, with the production of acetoin and 2,3-butanediol, which have a neutral pH. (used to identify organisms that perfomr a 2,3-butanediol fermentation)

49
Q

What do VP-positive organisms do?

A

they initially produce lactic acid and temporarily lower the pH, but the lowered pH activates the 2,3-butanediol fermentaion pathway. Accumulation of its neutral end products raises the pH by the completion of the test.

50
Q

What is contained in the MR-VP solution and what does each ingredient do?

A

It is a simple solution containing only peptone, glucose, and a phosphate buffer.
Peptone and glucose - provide protein and fermentable carbohydrate.
Potassium phosphate resists pH changes in the medium

51
Q

In the MR-VP test, what does the Methyl red do? What colors does it produce and why? What do these results tell you?

A

It is an indicator dye which verifies mixed acid fermentation following incubation.

  • Red at pH 4.4 (only true indication of a positive result)
  • Yellow at pH 6.2 (negative)
  • Various shades of orange between those two pH values (negative or inconclusive)
52
Q

What does adding VP reagents to the MR-VP medium do? What colors does it produce and what do these results mean?

A

oxidizes the acetoin to diacetyl, which in turn reacts with guanidine nuclei from peptone to produce a red color.
Red - positive
No color (or development of copper color) after the addtion of reagents - negative

53
Q

How do you avoid conflicting results between the MR and the VP color results when running this test?

A

To avoid conflict two 1 mL volumes are transferred from the MR-VP broth to separate test tubes after incubation. Methy lred indicator reagent is added to one tube, and VP reagents are added to the other. color changes then are observed and documented.

54
Q

What microbes did we use in our MR-VP lab and what were the results?

A

Ea (Enterococcus aerogenes) - MR negative/VP positive

Ec (Escherichia coli) - MR positive/VP positive

Microbiology (21 decks)

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