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Biology 111 > Lab Practical 2 > Flashcards

Lab Practical 2 Flashcards

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0
Q

Why do you want to count microbes only from a plate with 30-300 colonies?

A

Only numbers between 30-300 are considered statistically valid. If greater then 300, there is a probability of overcrowding and inhibits cell growth. Less then 30 involves sample error

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1
Q

Why are population counts important?

A

Allows one to see which organisms are alive and growing

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2
Q

What are the advantages of the standard plate count?

A

Easy to use
Can be used for a number of different organisms
Universally used

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3
Q

What are the disadvantages of standard plate count?

A

Can get artificial numbers, both dead and alive organisms are counted

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4
Q

Obligate (strict) aerobes

A

Require oxygen for growth because they carry out respiratory metabolism in which oxygen functions as a terminal electron acceptor.

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5
Q

Microaerophiles

A

Bacteria prefer to grow in oxygen concentrations of 5-10% rather then 20%
Example: helicobacter pylori

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6
Q

Facultative aerobes

A

Bacteria can grow either aerobic or anaerobic depending on culture conditions
Example: e. Coli

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7
Q

Aerotolerant anerobes

A

Can grow in the presence of oxygen and are not usually harmed by its presence in the environment. Metabolism doesn’t require oxygen but involves fermentation

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8
Q

Obligate (strict) anaerobes

A

Bacteria cannot tolerate oxygen and must be cultivated under conditions where oxygen is removed
Example: clostridium

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9
Q

Superoxide dismutase

A

Which converts superoxide to oxygen and hydrogen peroxide

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10
Q

Peroxidase

A

Detoxifying enzyme

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11
Q

Fluid thioglycollate medium (FTM)

A

Rich liquid that supports the growth of both aerobic and anaerobic bacteria. Contains a dye called resazurin

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12
Q

Resazurin

A

An indicator in the FTM for the presence of oxygen. The dye becomes pink if oxygen is present. The medium will become pink at the top and colorless in the middle and the bottom

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13
Q

Brewers anaerobic agar

A

Is a solid medium for culturing anaerobic bacteria in a Petri dish.

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14
Q

GasPak anaerobic jar

A

Provides an oxygen free incubation environment for the Petri dishes of anaerobic agar.. Hydrogen is generated in the jar which removes the oxygen by forming water. Palladium pellets catalyze the reaction at room temperature

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15
Q

In a purple Petri dish,Purple indicates?

A

Oxygen is present

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16
Q

In a Petri dish, if it is clear it indicates?

A

Oxygen is not present

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17
Q

Aerobic growth in a test tube

A

Located at the top of the tube

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18
Q

Microaerophillic growth in a test tube

A

Located in the middle of the test tube

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19
Q

Facultative growth in a test tube

A

Located throughout the entire tube

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20
Q

Anaerobic growth in a test tube

A

Located in the bottom of the test tube

21
Q

Cultivation and identification of anaerobes temp and for how long

A

32 degrees C

24-48 hours

22
Q

Effects on temperature on growth lab temp and for how long

A 
One incubator 37°C
Another incubator 55°C
Refrigerator 10°C
Room temperature 22°C
24-48 hours
23
Q

Psychrophile

A

Cold loving
Will grow in temperatures -5°C to 20°C
Not infectious to humans
Responsible for spoiling food and frozen foods

24
Q

Mesophiles

A

Middle loving
Grow in temperatures of 20°C to 50°C
Optimum temperatures for human pathogens are around 37°C

25
Q

Thermophiles

A

Heat loving
Will grow in temperatures 50°C to 80°C
Found in natural hot springs

26
Q

Hyperthermophiles

A

Extreme heat

Will grow in temperatures above 80°C

27
Q

Halo tolerant

A

Bacteria that can tolerate moderate concentrations of salt up to 10%

28
Q

Halophilis

A

Bacteria that require high levels of salt. 15-30% to live and grow

29
Q

Losmophiles

A

Bacteria that will grow in environments in high concentrations of sugar

30
Q

Sugar fermentation experiment temperature and length of incubation

A

37°C

48 hours

31
Q

Ferment manitol

A

Durham tube (upside down tube within a tube): indicates the presence of gas that was produced as a result of fermentation
Contains a phenol red pH indicator
**begins red
If no color change: no fermentation occurred
Color change to yellow: fermentation occurred

32
Q

MR-VP (methyl-red vogues proskauer) test

A

Broth
Results: 2 tubes, the original and one with the 1ml of broth
In the original tube: add methyl red indicator, will turn red if pH dropped below 5
(Red= mixed fermentation)

Tube with 1ml broth: add VP solution A and VP
If it turns pink/red alcohol fermentation occurred

**always a +MR/-VP or -MR/+VP result

33
Q

Catalase production experiment

A

37°C for 48hours
Use an agar plate
Drop hydrogen peroxide on plate if bubbling occurs then it is positive for catalase

34
Q

Citrate utilization experiment

A

Uses Simmons agar slant (starts dark green)
If a positive change occurs it will change to a blue
Negative- remains green

35
Q

Starch hydrolysis

A

Determines if bacteria have enzyme called amylase that breaks down starch to sugar

Results: flood starch agar plate with grams iodine (IKI), IKI turns starch to blue or a dark color

After 2 minutes if the zone is clearing (zone of clearing) turns to a lighter color around the colonies then it is positive

36
Q

Urea hydrolysis

A

Determines if bacteria has the enzyme urease that breaks down urea into ammonia.

Results:
The tube contains phenol red pH indicators (nothing added)
*positive: broth turns red/purple, presence of urea
*negative: no color change

37
Q

Tryptophan hydrolysis

A

Determines if bacteria have enzyme called tryptophanase that break down the amino acid tryptophan into insole and pyruvate
Add indole reagent to tryptophan broth

Results:
Positive: indole is present if red layer is at the top of the tube

38
Q

Kilger’s iron agar

A

Experiment that determines if bacteria are capable of conducting acidic fermentation with glucose and lactose and if they produce sulfide gas from amino acid cysteine

39
Q

Results for Kilger’s iron agar

A
  • bottom: yellow, top: red then glucose was used during fermentation. If it is split apart then gas was produced
  • Entire tube is yellow: glucose and lactose were both used during acidic fermentation . If the solid material is split then it gas was produced
  • tube turns black: bacteria can degrade the amino acid cysteine into pyruvic acid, ammonia and hydrogen sulfide
40
Q

Dichotomous key

A

The key always has two answers for each question asked, determines the next question or test

41
Q

Why is UV light lethal to bacteria?

A

.

42
Q

Is UV light harmful to humans?

A

.

43
Q

Covered vs. uncovered Petri dishes

A

The card or the lid blocks the UV light which allows more bacteria to grow

44
Q

What is thermal death time?

A

The time required to kill a suspension of cells or spores at a given temp

45
Q

What is thermal death point?

A

Temp at which an organism is killed in 10 minutes or when the microorganisms start to die

46
Q

Why is a control plate used?

A

Use the control to compare the results of the tests

47
Q

What does “use dilution” refer to?

A

Moving away from the source

In this experiment, the drug moving away from the disk, and affecting the growth/death of bacteria

48
Q

Is the “use dilution” or “paper disc” method more accurate?

A

The “use dilution” method is more accurate

49
Q

What is the zone of inhibition?

A

The area around the disk with no bacteria

50
Q

Which antibiotic is most effective? Against what bacteria? And how can you tell?

A

Iodine

51
Q

Drugs used in the antibiotic evaluation experiment

A

Erythromycin: narrow spectrum, difficulty entering gram negative
Streptomycin: narrow spectrum, prevents formation of cell walls in gram positive cells
Sulfonamides: competitive inhibitor, must be used in high concentrations to be truly effective
Tetracycline: disrupts protein synthesis, very broad spectrum

Biology 111 (6 decks)

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