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BIO150 > Lab 2 Exam > Flashcards

Lab 2 Exam Flashcards

1
Q

What are the colors of the following blood agar test results?

  • Gamma Hemolysis
  • Alpha Hemolysis
  • Beta Hemolysis
A
  • Gamma Hemolysis - red “no hemolysis”
  • Alpha Hemolysis - black/green (kinda brown)
  • Beta Hemolysis - clear spots (kinda yellow)
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2
Q

Positive Phenol Red Broth

A
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3
Q

Negative Phenol Red Broth

A

No gas

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4
Q

Three sugars of TSA/Kliger Iron test?

A
  1. Glucose
  2. Lactose
  3. Sucrose
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5
Q

Positive Salmonella TSA/Kliger Iron test

A
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6
Q

Positive and Negative Citrate test

A

Positive: Blue (Example: Salmonella)

Negative: Green (Example: E. coli)

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7
Q

Psychrophiles

A

Organisms that only grow -15 to 25° C

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8
Q

Organisms that only grow -15 to 25° C

A

Pyschrophiles

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9
Q

Mesophile

A

Organisms that only grow between 25 and 40° C

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10
Q

Organisms that only grow between 25 and 40° C

A

Mesophiles

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11
Q

Thermophiles

A

Organisms that grow between 40 and 60° C

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12
Q

Organisms that grow between 40 and 60° C

A

Thermophiles

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13
Q

Hyperthermophiles

A

Organisms that only grow in temperatures >70° C, but no greater than 120° C

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14
Q

Organisms that only grow in temperatures >70° C, but no greater than 120° C

A

Hyperthermophiles

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15
Q

What temperature category would human microbiota and human pathogens fall under?

A

Mesophiles

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16
Q

What is the optimum temperature of growth for E. coli?

A

37° C

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17
Q

What are the optimal growth temperatures for E. coli and S. marcescens?

A
  • E. coli*: 37° C
  • S. marcescens*: 30° C
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18
Q

In what way(s) could you adjust incubation temperature to grow an organism at less than its optimal growth rate?

A

You could lower or raise the temperature

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19
Q

Why do different temperatures produce different growth rates?

A

Different microorganisms function at different temerature levels; while some microorganisms can function at colder temperatures (psychrophiles) if another organisms (a mesophile) was put in that environment their proteins and functions would stop.

20
Q

What is OD?

A

Optical Density:

The measure of the amount of light absorbed by a suspension of bacterial cells or a solution of an organic molecule with the use of a colourimeter or spectrophotometer. (http://www.biology-online.org/dictionary/Optical_density)

21
Q

What is the purpose of the Snyder test?

A

To detect dental carries or dental carries causing bacteria

22
Q

What is the pH of the Snyder test medium? Which organisms show a positive test result?

A

The pH of the Snyder medium is 4.8. Lactobacilli and oral streptococci can survive these harsh conditions, fermenting the glucose/carbohydrates of the medium and lower the pH even further. The color indicator used is bromcresol freen; there is a reaction showing bacterial growth the culture will turn yellow.

23
Q

What is the color of a positive Snyder test? Of a negative result?

A
24
Q

What are the ingredients of the Snyder test (7 total)? Besides lactobacillus species fermenting the glucose, what other metabolic functions might the test indicate?

A
  • Ingredients:
    • pancreatic digest of casein
    • yeast extract
    • dextrose
    • sodium chloride
    • agar
    • bromcresol green
    • distilled or dionized water
  • Also indicates:
    • Pancreatic or digestive bacterias
    • other fermenting bacteria
    • Other bacteria that lower the pH?
25
Q

Considering the ingredients of the Snyder test, what kinds of dietary items would likely increase the number of lactobacilli in saliva?

A

Dairy products which contain lactobacilli and foods which have fermentation (pickles, beer, cider, animal feed)

26
Q

Why isn’t the Snyder test agar allowed to solidify as a slant?

A

because the bacteria will only react in an anaerobic environment; a slant creates too much surface area exposed to oxygen

27
Q

Is UV light ioninzing or non-ionizing? Short or long wavelengths?

A

Non-ionizing; long

28
Q

Which is more germicidal, short or long wavelengths?

A

Short

29
Q

Which wavelength of light is most germicidal: a, b, c? Why?

A

C, because it is the shortest wavelength.

30
Q

How does UV light cause death to microbes?

A

Creates thymine (pyrimidine) dimers

31
Q

What limited protection do cells have against damagine effects of UB radiation?

A

Nucleotide excision repair and photolyases

32
Q

How are endospores protected fromt eh harmful effects of UV light?

A

They have a thick outerlayer with diclolinic acid which is heat resistant and light resistant

33
Q

What result was observed when the Petri dish was kept covered during exposure to UV light? Why was such a result observed?

A

The areas that were covered and not directly exposed to UV light continued to have bacterial growth. UV light is not very penetrating so even a thin sheet of paper could prevent damage of microorganisms.

34
Q

Which B. megaterium culture, logarithmic or stationary phase, would show the best survival following exposure to UV radiation?

A

The stationary phase would show the best survival because there would be endospores with a thicker, light resistant, coat protecting them from the UV radiation.

35
Q

Define the three major types of hemolysis that can be seen on blood agar.

A
  1. β-hemolysis: complete destruction of RBCs and hemoglobin
  2. α-hemolysis: is the partial destruction of RBCs and produces a greenish discoloration of the agar around the colonies
  3. γ-hemolysis: nonhemolysis and appears as simple growth with no change to the medium
36
Q

What is the exotoxin produced by gram-positive cocci that can cause breakdown of RBCs.

A

Streptolysin

One kind, called streptolysin O (SLO), is so named because it is inactivated by atmospheric oxygen. Another kind of streptolysin is called streptolysin S (SLS) because it is stable in an oxygen environment. Both streptolysins can cause lysis not only of red blood cells, but also of white blood cells (whose function is to kill the streptococci) and other body cells.

37
Q

What type of hemolysis is produced by Streptococcus pyogenes, the causative agent of strep throat?

A

Beta-hemolytic streptococci A useful basis for classifying some streptococci is their colonial appearance when grown on blood agar. The beta-hemolytic species produce a hemolysin that forms a clear zone of hemolysis on blood agar (see Figure 6.9 on page 161). This group includes the principal pathogen of the streptococci, Streptococcus pyogenes (pī-AH-jen-ēz), also known as the beta-hemolytic group A streptococcus. Group A represents one of an antigenic group (A through G) within the hemolytic streptococci.

38
Q

What type of hemolysis is produced by Streptococcus pneumoniae?

A

Alpha-hemolytic

When alpha hemolysis (α-hemolysis) is present, the agar under the colony is dark and greenish. Streptococcus pneumoniae and a group of oral streptococci (Streptococcus viridans or viridans streptococci) display alpha hemolysis. This is sometimes called green hemolysis because of the color change in the agar. Other synonymous terms are incomplete hemolysis and partial hemolysis. Alpha hemolysis is caused by hydrogen peroxide produced by the bacterium, oxidizing hemoglobin to green methemoglobin.

39
Q

In regards to the hemolysin lab experiment, why is it important to cover and tape the plates?

A

As most of the samples are from student’s throats it is likely a student could laugh or breath onto the cultures and contaminate them.

40
Q

What is another name of the filter paper disk method?

A

Kirby Bauer

41
Q

What is the purpose of the Kirby Bauer test?

A

To test the effectiveness of antimicroboticsagainst pathogenic microorganisms

42
Q

What medium is used for the Kirby Bauer test?

A

Mueller-Hinton II Agar

  • Beef extract
  • Acid hydrolysate of casein
  • Starch
  • Agar
  • Distilled or deionized water
43
Q

Antiseptic

Disinfectant

Anything used as both?

A

destroy harmful microorganisms on living organisms

destroy harmful bacteria on nonliving

alcohol

44
Q

What do sanitizers do

A

Lower the load of microrganims

45
Q
A

BIO150 (15 decks)

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