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BIO 120.01 > Microbial Growth & Methods of Measuring Growth > Flashcards

Microbial Growth & Methods of Measuring Growth Flashcards

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Biology 101 flashcards
1
Q

List

Kinds of Cell Division

3

A
  1. Binary fission
  2. Budding
  3. Biofilm
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2
Q

List

Examples of fast growers & their generation times

3

A
  1. E. coli (15-18 mins)
  2. S. aureus (27-30 mins)
  3. Bacillus subtilis (26 mins)
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3
Q

List

Examples of slow growers & their generation times

2

A
  1. Leptospira (6-8 hr)
  2. Mycobacterium (18-24 hr)
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4
Q

Differentiate

Closed Culture System vs Open Culture System

A

Closed
* fixed amount of nutrient at the start
* leave for 18-24 hours
* no way to get rid of excess waste

Open
* keep adding fresh medium
* remove waste/excess
* mix for aeration

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5
Q

Identify

What is used to detect turbidity?

A

spectrophotometer

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6
Q

Define

viable count

Bonus: Where can you find it?

A
  • count of live cells
  • found in plates w/ media
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7
Q

List

Growth Phases

4

A
  1. Lag Phase
  2. Logarithmic/Exponential Phase
  3. Stationary Phase
  4. Death Phase
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8
Q

Identify

Plots different stages of (bacterial) life

A

Bacterial Growth Curve

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9
Q

phase with metabolic activity, but no growth

A

Lag Phase

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10
Q

List

What is the duration of the Lag Phase dependent on?

2

A
  1. Nutrients available
  2. Species
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11
Q
  • phase where there is a lot of growth
  • ↑ cell population, ↑ rate
  • generation time of organism can be determined
A

Logarithmic/Exponential Phase

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12
Q

Fill in the blank

To stay in the Logarithmic Phase, use an ____ culture system. This system is also called ____.

A

open, chemostat

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13
Q

Main components of chemostat

3

A
  1. inflow of new medium & air
  2. mixing of medium (aeration)
  3. outflow of waste
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14
Q

Factors that govern cell density

2

A
  1. Dilution rate
  2. Concentration of limiting nutrient
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15
Q

Why would you want to stay in the Logarithmic Phase?

A

For extraction purposes; you keep producing more cells & can extract more in a shorter amt of time

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16
Q

Phase where

  • Replication Rate = Death Rate
  • Limited Nutrients
  • ↑ Microbial waste
A

Stationary Phase

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17
Q

During the stationary phase, the environment becomes ____, with a [higher/lower] pH and a [higher/lower] oxygen level.

A

toxic, higher, lower

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18
Q

Phase with

  • little to no nutrients
  • ↑ toxic waste
  • Endospores form
A

Death Phase

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19
Q

What happens to cells during the death phase?
Why do they do that?

A

Involution: they change shape

  • ex. rod → spherical
  • to limit cell’s nutrient use
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20
Q

Why do endospores form during the Death Phase?

A

Endospores are how cells defend themselves in a toxic environment.

21
Q

Identify

  • process that helps reduce bacterial load
  • series of tubes with a diluent
A

Serial Dilution

22
Q

List

Methods of Measuring Bacterial Growth

7

A
  1. Serial Dilutions
  2. Viable Cell Count
  3. Direct Cell Count
  4. Most Probable Number Technique
  5. Most Probable Count
  6. Filtration
  7. Spectophotomoetry
23
Q

Why do we do serial dilation?

A

If you don’t, your sample might have too many colonies –> won’t be visible when trying to count them

24
Q

Kinds of diluent

A
  1. Normal Saline Solution (NSS): 0.85% saline solution
  2. Phosphate Buffer Solution (PBS)
25
Q

What happens when using a diluent & how do you use it?

A
  • Use it within 10-15 mins
  • Non-nutritious: cells don’t grow, but they also don’t die
26
Q

Explain

Serial Dilution Process

A
  1. E. coli (1 mL) in Test Tube 1 (9 mL diluent)
  2. Vortex (mix)
  3. Transfer 1 mL TT1 in TT 2 with 9 mL diluent
  4. Vortex
  5. Transfer 1 mL TT 2 in TT 2 with 9 mL diluent
  6. Repeat until 30-300 colonies
  7. Plate counting
27
Q

Why should the colony count be 30-300 when plate counting?
What do you declare when the colony count is outside that range?

A

[< 30] - TFTC (Too Few to Count)

  • statistically insignificant

[> 300] - TNTC (Too Numerous to Count)

  • won’t see individual colonies, too many layers
28
Q

Fill in the Blank

The Most Probable Number Technique is used for samples with a [high/low] amount of bacteria

A

low

29
Q

Identify

when a microorganism thrives in environments with small amounts of oxygen

A

microaerophilic

30
Q

Differentiate

Spread-plate method vs Pour-plate method

A

Spread-Plate

  • sample is spread on agar → surface colonies

Pour-plate
* sample is added first., then medium is added & mixed → colonies grow in agar & on top of agar

31
Q

where sample is placed for direct cell count

A

Petroff-Hauser counting chamber / haemocytometer

32
Q

Explain

The Great Plate Count Anomaly

A
  • no. from direct cell counts > no. from viable plate counts
  • Direct cell count: counts both live and dead cells
  • Viable plate count: “forgets” non-culturable cells (impossible for all kinds of cells to grow in 1 specific condition)
33
Q

What are solutions to the Great Plate Count Anomaly?

A
  1. Use more more selective/general medium (to target less organisms)
  2. Vary culture conditions
  3. Alter experiment
34
Q

Technique usually used on water (bottled water), food, air samples

A

Most Probable Number Technique

35
Q

What are the bases for positive reults in MPNT?

2

A
  1. turbidity
  2. gas production
36
Q

Describe the setup used in the Most Probable Number Technique.

A

1) x sets of test tubes, with x tubes per set

  • Set 1: 10 mL of sample
  • Set 2: 1 mL of sample
  • Set 3: 0.1 mL of sample

2) Incubate tubes (37ºC, 24 hr)
3) Compare the number of positive test tubes with what is on MPN table

37
Q

T/F [Bonus: If false, what is wrong?]

MPN Technique is usually part of a bigger experiment.

A

T

38
Q

What are phases of the “bigger experiment” that uses the MPN Technique? Why do we do each phase?

A
  1. Presumptive Phase - to observe gas production
  2. Confirmatory Phase - to confirm whether or not the colonies are fecal and/or harmful
  3. Completed Phase - identifies actual organism
39
Q

What other item is used in the presumptive phase, and why do we use it?

A

Durham tube

  • hard to observe gas production without it
  • a bubble can be found inside it
40
Q

Incubation Conditions for Presumptive phase & Confirmatory Phase

A

Presumptive: 37℃ for 24 hours
Confirmatory: 45 ℃ for 24 hours

41
Q

T/F

Getting a negative result in the Presumptive Phase requires you to proceed to the Confirmatory Phase

A

F

you are not required

42
Q

How long does the Confirmatory Phase take?
What kind of results do you need to proceed to Completed Phase?

A

2 weeks
positive tubes (in terms of turbidity)

43
Q

What broth/agar is used in each phase of the MPN Technique?

A
  1. Lauryl Sulfate Tryptone Broth (LSTB) - Presumptive phase
  2. Brilliant Green Lactose Bile Broth (BGLB) - Confirmatory Phase
  3. Eosine Methyl Blue (EMB) Agar - Completed Phase
44
Q

What is the size of the filter in a membrane filter? Why do we use that size

A

0.5 micrometers, so that the target organisms pass through the filter

45
Q

Explain

Filtration Method

A
  1. Use membrane filter
  2. Place filter on agar
  3. Leave for 24 hours
46
Q

measures amount of light unscattered aka light absorbed

A

Optical Density (OD)

47
Q

Fill in the blank

[↑/↓] light absorbed = [↑/↓] OD

Spectrophotometry

A

↑ light absorbed = ↑ OD

48
Q

[↑/↓] turbidity = [↑/↓] OD

A

↑ turbidity = ↑ OD

49
Q

What are the advantages & disadvantages of Spectrophotometry?

A

Advantage: fast (~10 mins)
Disadvantage: counts dead cells

BIO 120.01 (12 decks)

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