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Microbiology > Chapter 4 > Flashcards

Chapter 4 Flashcards

0
Q

What is the equation for Growth to be calculated?

A

Nt = No x 2^n

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1
Q

Generation time

A

Time it takes for cell to double

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2
Q

Nt

A

Number of cells in the population at time t

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3
Q

No

A

Original number of cells in population

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4
Q

n

A

Number of divisions

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5
Q

Example:

E.Coli has 20min generation time. How many generation time decisions will occur in one hour?

A 
1hr = 60min
60min/20min = 3 generation times
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6
Q

What does the speed of generation time depend on?

A

The species & environmental conditions

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7
Q

How do microorganisms survive in nature?

A
  • cells sense changes & adjust to surroundings
  • synthesize compounds useful for growth
  • live in biofilms
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8
Q

What are biofilms?

A

Polysaccharide encased communities

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9
Q

5 stages of Biofilms

A
  1. Planktonic bacteria adhere to surface
  2. Bacteria multiply & produce EPS
  3. Other bacteria attach to EPS
  4. Cells communicate & create channels for nutrients/waste
  5. Cells detach & move to other surfaces to create new biofilm
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10
Q

Pure Culture

A

Population of cells derived from a single cell

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11
Q

Aseptic technique

A

How to obtain pure culture without contaminating it

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12
Q

6 step Streak Plate method

A
  1. Sterilize loop
  2. Dip loop into culture
  3. Streak first area
  4. Sterilize loop
  5. Streak second area
  6. Sterilize loop
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13
Q

Closed system

A

-nutrients are not renewed & waste is not removed

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14
Q

Open system

A
  • Nutrients added & waste is removed

- maintains continuous growth

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15
Q

5 phases of Growth Curve

A
  1. Lag phase
  2. Log/Exponential Phase
  3. Stationary Phase
  4. Death Phase
  5. Phase of prolonged decline
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16
Q

Lag Phase

A
  • # of cells does not increase

- begin synthesizing enzymes for growth

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18
Q

Stationary Phase

A
  • nutrient levels too low to sustain growth

- # of cells remains constant

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19
Q

Death Phase

A

-# of cells decrease

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20
Q

Phase of Prolonged Decline

A

-some may survive but most die

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21
Q

______ of colony has O2 nutrients

A

Edge

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22
Q

_____ of colony has depleted O2 nutrients?

A

Center

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23
Q

Log/Exponential Phase:

A
  • cells decide at a constant rate
  • metabolism can make a lot of stuff such as proteins/insulin
  • gene splicing is commonly done at this point
  • 2 degree metabolite antibiotics Re produced by bacteria
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24
Q

3 Species that rely on temperature requirements?

A
  1. Psychrotroph
  2. Mesophile
  3. Thermophile
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25
Q

Psychrotroph

A

20-30 degrees Celsius

Important in food spoilage

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26
Q

Mesophile

A

25-45 degrees Celsius

Pathogens

27
Q

Thermophiles

A

45-70 degrees Celsius

Common in hot springs

28
Q

5 species that rely on oxygen requirements:

A
  1. Obligate aerobe
  2. Obligate anaerobe
  3. Facultative anaerobe
  4. Microaerophile
  5. Aerotolerant anaerobe
29
Q

Obligate aerobe

A
  • grows only when O2 is present
  • requires O2 for respiration
  • produces superoxide dismutase & catalase
30
Q

Obligate anaerobe

A
  • cannot grown when O2 is present
  • does not require O2 for respiration
  • does not produce superoxide dismutase or catalase
31
Q

Facultative anaerobe

A
  • grows best when O2 is present, but also grows without it
  • uses O2 for respiration
  • produces superoxide dismutase & catalase
32
Q

Microaerophile

A
  • grows only if small amounts of O2 are present
  • requires O2 for respiration
  • produces some superoxide dismutase & catalase
33
Q

Aerotolerant anaerobe

A
  • growth equally well with or without O2
  • does not use O2 for respiration
  • produces superoxide dismutase, but not catalase
34
Q

Superoxide dismutase

A
  • neutralizes superoxide O2 molecules

- causes hydrogen peroxide to form

35
Q

Catalase

A

Degrades hydrogen peroxide into O2+H2O

36
Q

Water availability

A
  • all microorganisms require water
  • some require higher salt

Ex. Halotolerant & halophiles

37
Q

4 Key Nutrient Factors that influence microbial growth:

A
  1. Elements
  2. Growth factors
  3. Energy sources
  4. Nutritional diversity
38
Q

10 Required Elements:

A
  1. Carbon
  2. Oxygen
  3. Hydrogen
  4. Nitrogen
  5. Sulfur
  6. Phosphorous
  7. Iron
  8. Potassium
  9. Magnesium
  10. Calcium
39
Q

Why are carbon, oxygen, & hydrogen important required elements?

A

-they make up amino acids, lipids, nucleic acids, & sugars.

40
Q

Why is Nitrogen a required element?

A

-used to make amino acids and nucleic acids

41
Q

Why are Iron and Phosphorous considered limiting?

A

Require more than there is available

42
Q

Heterotrophs

A
  • use organic carbon

- take it from proteins which get it from the environment

43
Q

Autotrophs

A
  • use inorganic csrbon

- get it straight from the environment (no protein needed)

44
Q

Nitrogen fixation

A

Ability to take nitrogen right out of the environment and put it into a molecule

45
Q

Why are Growth Factors important for microbial growth?

A

-some microbes cannot synthesize amino acids, vitamins, ect

46
Q

Fastidious

A

Unable to synthesize certain molecules and therefore require them to be provided for them

47
Q

Non-Fastidious

A

Can synthesize all molecules for itself

48
Q

Name 2 species and how they get energy for growth:

A
  1. phototrophs- obtain energy from sunlight (plants)

2. chemotrophs- extract energy from chemicals (fungi)

50
Q

Environmental factors that influence microbial growth:

A
  • temperature
  • atmosphere
  • pH
  • water availability
  • nutrients
51
Q

Defined media

A

All compounds are measures out exactly

Ex. Glucose salts

52
Q

Complex media

A

Not measured, just a bunch of components put together

Ex. Tsa

53
Q

Selective media

A

Inhibits growth of certain species, but not all

54
Q

Differential media

A

Contains substances that microbes change in identifiable ways

55
Q

Candle jar method

A
  • some bacteria grows best with excess CO2.

- the candle takes oxygen and produces CO2

56
Q

Direct Cell Count

A
  • Counts total number (living and dead)

- does not guarantee viable cell count

57
Q

What is required for a cell to be viable?

A

-cell must be capable of multiplying

58
Q

Plate counts

A
  • keep diluting the sample until there are roughly 30-300 cells
  • most accurate
  • determines colony forming units
59
Q

Membrane filtration

A
  • Runs bacteria through a filter & they get stuck.

- best way to get viable count with a dilute sample

60
Q

Most probably number method

A
  • estimates cell concentration through dilute series

- place smaller tube inside larger one to collect the gasses

61
Q

Spectrophotometer

A
  • Measures the difference in how much light is absorbed, which helps determine the growth culture.
  • more bacteria–> more absorbed
62
Q

What methods are for viable cell counts?

A
  • plate count
  • membrane filtration
  • most probably number
63
Q

Anaerobic containers

A

Useful if microbes can tolerate brief O2 exposure. (Creates anaerobic environment)

64
Q

Are escherichia & salmonella cocci or baccili??

A

bacillus- rod shaped

65
Q

T/F: Microbes will only grow until the least represented (limiting) nutrient in the medium is used up?

A

True

Microbiology (10 decks)

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