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MicroBiology Lab > Quiz 3 > Flashcards

Quiz 3 Flashcards

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1
Q

What is extracellular degradation? How does it work? What classes of enzymes are
involved?

A
  • Extracellular degradation - The breakdown of large molecules for necessary nutrients to enter the cell
  • Extracellular enzymes make and release enzymes into the surrounding medium.
  • Hydrolytic enzymes break up large molecules (polymers)
  • Classes of enzymes - Esterases (Break fats and lipids), Glycosidases (Break up polysaccharides) , and Proteinases (Break apart proteins)
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2
Q

What is translocation ?

A

Movement of molecules across the membrane

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3
Q

What is a polysaccharide? How is it degraded?

A
  • Carbohydrates: Compounds of carbon, hydrogen, and oxygen.
  • hydrolytic enzymes are a way polysaccharides are degraded
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4
Q

Types of carbohydrates

A
  • Monosaccharides, Oligosaccharides, and Polysaccharides
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5
Q

Structural Classification VS Nutrient Classification

A
  • Structural- Cellulose, pectin, hyaluronic acids
  • Nutrient - Glycogen and starch
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6
Q

What is starch made from?

A

A chain of glucose molecules. Formed through larger chains called polysaccharides

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7
Q

Types of starch

A

Amylose and Amylopectin

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8
Q

Amylase

A

Enzymes that break down starch into simple sugars such as maltose and glucose

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9
Q

What molecule is formed as starch is degraded?

A

Maltose and smaller amounts of glucose

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10
Q

How can we evaluate if degradation occurs (technique employed)? What is the purpose
of iodine in this experiment? (Degradation of starch)

A
  • Use starch agar. Zone of hydrolysis results from the enzymatic breakdown of the insoluble starch
  • Iodine reacts with starch to create a dark color on the plate. Hydrolysis of starch can’t be seen and iodine makes the starch visible

Amylose (gives a deep deep-blue color when it reacts with iodine).

Amylopectins (Gives a red to brown color when they react with iodine)

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11
Q

What do positive/negative reactions look like? (When looking at the degradation of polysaccharides starch)

A

Positive result: clear, colorless zone surrounds growth of colony or streak.

Negative result: Entire plate stains deep blue or red-brown with no clear, colorless zones.

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12
Q

What is a protein? How is it degraded? Which protein is in milk?

A

Protein - Long complex folded chains of amino acids that are linked through peptide bonds

  • Proteins are degraded through Proteinases. Proteinases break down proteins through hydrolytic cleavage of the protein molecule outside the cell.
  • Casein proteins are found in milk
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13
Q

Peptidases

A

Enzymes that degrade peptides

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14
Q

Rancidity

A

Food spoilage in which unpleasant odors and flavors develop due to the release of free fatty acids from triglycerides

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14
Q

Casein

A
  • When casein binds to calcium it forms calcium caseinate (Water-insoluble)
  • Casein being insoluble makes it a good indicator of a reaction
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15
Q

Gelatin

A
  • Formed by boiling collagen in water or acid solution.
  • It liquefies at temperatures above 28 Celsius
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16
Q

How can we evaluate if degradation occurs? How do the casein and gelatin tests differ?

A

Casein - To study the degradation of casein we use a milk plate. If bacteria can digest casein, clearing will appear around the growth

Gelatin - To study the degradation of gelatin we are using gelatin deeps. If bacteria is able to digest gelatin, the deep will no longer be a solid, it will liquify

  • The difference between casein and gelatin tests is that casein is not temperature dependent like the gelatin is
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17
Q

What do positive/negative reactions look like? (Degradation of proteins Casein and Gelatin)

A

Casin
- Negative will look like nothing and have no clear zone (Doesn’t produce casein)

  • Positive will have a clear area around the site (Produce proteases to degrade casein)

Gelatin
- Positive gelatin will liquify at the top. Gelatin was degraded

  • Negative gelatin will remain solid at the top. Gelatin wasn’t graded
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18
Q

What is a lipid? How is it degraded?

A
  • Lipids are organic compounds that are mostly insoluble in water. Composed of fats and oils
  • Lipases are used to degrade lipids
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19
Q

Triglycerides

A

Glycerol with three fatty acid chains

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20
Q

Lipases

A

Enzymes that hydrolyze glycerol by separating the ester linkages between glycerol and the fatty acid molecules

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21
Q

Phospholipids

A

hydrophilic (polar head) and Hydrophobic (Non-polar) tail

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22
Q

How can we evaluate if degradation occurs? How do the lipid and phospholipid tests
differ?

A

Lipids - To study lipases we are using spirit blue agar. Spirit blue agar shows the release of fatty acids as the medium contains a pH indicator and the fatty acid release will change the pH

Phospholipases - Egg yolk agar is used. The agar will become opalescent when the fatty acids are broken down due to the accumulation of water-insoluble fatty acids

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23
Q

What do positive/negative reactions look like? (Phospolipids and Lipids)

A

For the lipid test, positive results will turn the agar a pale lavender or deep blue color. For the phospholipids test, positive results will be an oily surface film that appears opalescent.

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24
Q

How is citrate used in bacterial metabolism? How do we test if it is used?

A
  • Citrate is used as a carbon source within metabolism.
  • Simmons citrate agar is used through slants for differentiating gram-negative bacteria based on citrate utilization.
25
Q

Aerogenes vs Coli

A

Aerogenes - Can use citric acid as a sole carbon source

Coli - Cannot use citric acid as a sole carbon source

26
Q

What is the role of bromothymol blue in this media?

A

Bromothymol blue is used as a pH indicator. Green under acidic conditions and blue under alkaline (basic) conditions.

27
Q

What does a positive/negative result look like? What does this tell us about the bacterial
metabolism? (Citrate experiment)

A

Positive - Blue
Negative - Green

  • The aerogenes group can use citric acid as a sole carbon source but the coli group cannot. The aerogenes group can remove the citric acid and excrete alkaline waste products
28
Q

What are enteric bacteria?

A
  • Large group of gram-negative bacteria found within the intestines within animals and humans
29
Q

What is fermentation?

A

the catabolic process in which
sugars are partially degraded to
produce ATP (energy)

30
Q

How can we observe fermentation ?

A

For a positive reaction - Turn the phenol red indicator yellow (pH at or below 6.9). Gas bubbles occur

For negative reaction - Growth occurs, but media remains the same color or yellow only in the Durham tube and/or in the bottom of the culture tube. Growth occurs but no bubbles on top of the test tubes

31
Q

What is respiration ?

A

complete oxidation of organic
compounds to produce ATP
(energy)

32
Q

Anaerobic

A

occur in the absence of O2

33
Q

Electron deficient

A

Lacks the electron transport chain

34
Q

Inefficient

A

Less energetically favorable than respiration

35
Q

Excretion

A

Releases fermentation end products

36
Q

Homolactic Acid bacteria

A

Primarily excrete lactic acid (Lactobacillus and Streptococcus)

37
Q

Heterolactic Acid Bacteria

A

Excrete acetic acid, ethanol, glycerol, along with lactic acid (Lactobacillus and Leuconostoc)

38
Q

What is a pH indicator and how does it work?

A
  • Used to detect and study acid production
  • A pH indicator is a chemical compound added in small amounts to a solution so the pH of the solution can be determined visually by gradually changing color over a range of pH levels.
  • pH indicators detect the presence of H+ and OH-.
39
Q

How do we evaluate growth, acid production, and gas production?

A

Positive Reaction: Acid: turns phenol red indicator yellow in the entire tube (pH at or below 6.9). Gas bubbles.

Negative Reaction: Growth occurs, but media remains the same color or yellow only at the bottom of the culture tube. no bubbles on the top of the tubes.

40
Q

What types of bacteria do these tests differentiate? (The Methyl Red and Voges-Proskauer Tests )

A
  • Differentiation two major types of anaerobic enteric bacteria
41
Q

What is the difference between mixed acid and butylene glycol fermentation?

A
  • In the Mixed acid type equal amounts of CO2 and H2 are created.Large amounts of lactate are formed
  • In butylene glycol fermentation it produces more than twice the amount of CO2. A little amount of lactate produced
42
Q

What do negative/positive results look like and what do they tell you about bacterial
metabolism? (The Methyl Red and Voges-Proskauer Tests)

A
  • In the MR test, Red indicates lots of acid via mixed acid fermentation which drives down the pH. Yellow indicates that there is no acid production
  • In the VP test, Red indicates acetoin can be produced via butylene glycol fermentation. Copper indicates that the organism cannot produce acetoin
43
Q

What is catabolite repression? How does it work?

A
  • Catabolite repression is where sugar shuts down tryptophan use
  • Glucose inhibits indole production. Cells get more energy from respiration with glucose than respiration with tryptophan
44
Q

What do negative/positive results look like and what do they tell you about bacterial (indole Production from the Amino Acid Tryptophan and Catabolite Repression)

A

pink layer indicates the presence of indole, the absence of color means that it was not produced

45
Q

What is tryptophan and how does it relate to indole?

A
  • Tryptophan is an essential α-amino acid that is used in the biosynthesis of proteins and cannot be produced by the body.
  • Tryptophan is translocated from outside of the cell inside and broken down into indole and pyruvate. Indole is excreted and pyruvate oxidized for energy (aerobic bacteria)
46
Q

Durham Tubes

A
  • Allows us to study gas production
  • Inverted vials place broth filed test tube prior to sterilization
  • Gas produced during fermentation is trapped and produced a bubble
47
Q

How is sulfate used in bacterial metabolism? How can this be detected in the laboratory?

A
  • Sulfate can serve as an electron acceptor in anaerobic respiration and can also be reduced for the formation of organic compounds.
48
Q

Hydrogen Sulfide (H2S)

A
  • Gas that is water soluble
  • The product of sulfate used in bacteria. Smells like rotten eggs and when bonded to iron, turns to a black substance
49
Q

What do negative/positive results look like and what do they tell you about bacterial
metabolism?

A

When H2S gas reacts with ferrous ions (iron, Fe+), it forms a ferrous sulfide, which is a black precipitate. The black precipitate is only present in iron-containing media in which growing microbes produce hydrogen sulfide.

50
Q

What is the role of peptone in the agar?

A

It provides nutrients like carbon and nitrogen to bacteria

51
Q

How does the litmus milk test work? What are the possible outcomes?

A
  • Litmus is a substance obtained from lichens, as well as a pH indicator. In the litmus reduction, a change in color of litmus from light blue/gray to white (total lack of color), is caused by a lack of oxygen.
  • Possible outcomes
  • No change (Color remains light blue-purple).
  • Acid ( Change in color of litmus).
  • Litmus reduction ( Change of color from light blue-purple to white)
  • Curd (Change in milk from fluid to solid)
  • Proteolysis - Results in bluish brown to amber colored fluid
52
Q

What do these outcomes of the litmus tell you about bacterial metabolism?

A
  • Change in pH - Due to excretion of acid or basic fermentation products. Red color - Acidic conditions. Blue/Purple color - Basic conditions
  • Change in O/R - Potential from oxygen depletion
  • Curdling - Large quantities of excreted acid
  • Proteolysis - Resulting from the action of excreted extracellular enzymes.
53
Q

How does the oxidase test work? What does it tell you about bacterial metabolism?

A
  • This test can differentiate enteric bacteria which are negative for this test.
  • Test for Cytochrome C oxidase (Used in aerobic respiration for metabolizing compounds like sugars for energy)
54
Q

How does the catalase test work? What does it tell you about bacterial metabolism?

A
  • Identifies bacteria that produce the enzyme catalase

-Positive results show us that the bacteria produces catalase and can break down hydrogen peroxide; bubbles form. A negative result shows us that the bacteria doesn’t produce catalase and may not need to detoxify hydrogen peroxide ; no bubbles form

55
Q

What do positive/ negative results look like for these tests? (est for Cytochrome C (Oxidase) and Catalase Activities)

A
  • Oxidase
  • Positive - Dark purple/Blue color
  • Negative - No color change
  • Catalase
    -Positive - Rapid bubbling
  • Negative - No bubbling
56
Q

What is the process for isolating an unknown organism? (you should know what primary
and secondary streaks are and why they are used)

A

Primary streaks - Used to separate individual bacteria from a mixed sample to form isolated colonies.

Secondary Streaks - Used to ensure the purity of the isolated colony by obtaining a pure culture.

57
Q

What species are active and contribute to the different stages of yogurt production?

A
  • The first stage favors the growth of heat-tolerant organisms. Streptococcus thermophilus. Milk contains lactose and the bacteria converts lactose to lactic acid through homolactic fermentation

The second stage of yogurt production is carried out at a moderate temperature. Lactobacillus Bulgaricus. The bacteria ferments the remaining lactose and gives yogurt its flavor and aroma.

58
Q

What happens to lactose and casein during the fermentation process?

A
  • Lactose gets hydrolyzed into glucose and galactose. Ferments into lactic acid lowers pH and contributes to sour flavor.
  • Casein gets broken down into peptides and amino acids by proteolytic enzymes. Metabolized into compounds that contribute to flavor aroma, and texture.
59
Q

How is this experiment linked to the litmus milk test ?

A

Both deal with lactose fermentation. In both yogurt production and the litmus milk test, lactose fermentation by lactic acid bacteria produces lactic acid.

MicroBiology Lab (5 decks)

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