Chapter 4 Flashcards
(64 cards)
0
Q
What is the equation for Growth to be calculated?
A
Nt = No x 2^n
1
Q
Generation time
A
Time it takes for cell to double
2
Q
Nt
A
Number of cells in the population at time t
3
Q
No
A
Original number of cells in population
4
Q
n
A
Number of divisions
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
6
Q
What does the speed of generation time depend on?
A
The species & environmental conditions
7
Q
How do microorganisms survive in nature?
A
- cells sense changes & adjust to surroundings
- synthesize compounds useful for growth
- live in biofilms
8
Q
What are biofilms?
A
Polysaccharide encased communities
9
Q
5 stages of Biofilms
A
- Planktonic bacteria adhere to surface
- Bacteria multiply & produce EPS
- Other bacteria attach to EPS
- Cells communicate & create channels for nutrients/waste
- Cells detach & move to other surfaces to create new biofilm
10
Q
Pure Culture
A
Population of cells derived from a single cell
11
Q
Aseptic technique
A
How to obtain pure culture without contaminating it
12
Q
6 step Streak Plate method
A
- Sterilize loop
- Dip loop into culture
- Streak first area
- Sterilize loop
- Streak second area
- Sterilize loop
13
Q
Closed system
A
-nutrients are not renewed & waste is not removed
14
Q
Open system
A
- Nutrients added & waste is removed
- maintains continuous growth
15
Q
5 phases of Growth Curve
A
- Lag phase
- Log/Exponential Phase
- Stationary Phase
- Death Phase
- Phase of prolonged decline
16
Q
Lag Phase
A
- # of cells does not increase
- begin synthesizing enzymes for growth
18
Q
Stationary Phase
A
- nutrient levels too low to sustain growth
- # of cells remains constant
19
Q
Death Phase
A
-# of cells decrease
20
Q
Phase of Prolonged Decline
A
-some may survive but most die
21
Q
______ of colony has O2 nutrients
A
Edge
22
Q
_____ of colony has depleted O2 nutrients?
A
Center
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
24
Q
3 Species that rely on temperature requirements?
A
- Psychrotroph
- Mesophile
- Thermophile
25
Psychrotroph
20-30 degrees Celsius
Important in food spoilage
26
Mesophile
25-45 degrees Celsius
Pathogens
27
Thermophiles
45-70 degrees Celsius
Common in hot springs
28
5 species that rely on oxygen requirements:
1. Obligate aerobe
2. Obligate anaerobe
3. Facultative anaerobe
4. Microaerophile
5. Aerotolerant anaerobe
29
Obligate aerobe
- grows only when O2 is present
- requires O2 for respiration
- produces superoxide dismutase & catalase
30
Obligate anaerobe
- cannot grown when O2 is present
- does not require O2 for respiration
- does not produce superoxide dismutase or catalase
31
Facultative anaerobe
- grows best when O2 is present, but also grows without it
- uses O2 for respiration
- produces superoxide dismutase & catalase
32
Microaerophile
- grows only if small amounts of O2 are present
- requires O2 for respiration
- produces some superoxide dismutase & catalase
33
Aerotolerant anaerobe
- growth equally well with or without O2
- does not use O2 for respiration
- produces superoxide dismutase, but not catalase
34
Superoxide dismutase
- neutralizes superoxide O2 molecules
| - causes hydrogen peroxide to form
35
Catalase
Degrades hydrogen peroxide into O2+H2O
36
Water availability
- all microorganisms require water
- some require higher salt
Ex. Halotolerant & halophiles
37
4 Key Nutrient Factors that influence microbial growth:
1. Elements
2. Growth factors
3. Energy sources
4. Nutritional diversity
38
10 Required Elements:
1. Carbon
2. Oxygen
3. Hydrogen
4. Nitrogen
5. Sulfur
6. Phosphorous
7. Iron
8. Potassium
9. Magnesium
10. Calcium
39
Why are carbon, oxygen, & hydrogen important required elements?
-they make up amino acids, lipids, nucleic acids, & sugars.
40
Why is Nitrogen a required element?
-used to make amino acids and nucleic acids
41
Why are Iron and Phosphorous considered limiting?
Require more than there is available
42
Heterotrophs
- use organic carbon
| - take it from proteins which get it from the environment
43
Autotrophs
- use inorganic csrbon
| - get it straight from the environment (no protein needed)
44
Nitrogen fixation
Ability to take nitrogen right out of the environment and put it into a molecule
45
Why are Growth Factors important for microbial growth?
-some microbes cannot synthesize amino acids, vitamins, ect
46
Fastidious
Unable to synthesize certain molecules and therefore require them to be provided for them
47
Non-Fastidious
Can synthesize all molecules for itself
48
Name 2 species and how they get energy for growth:
1. phototrophs- obtain energy from sunlight (plants)
| 2. chemotrophs- extract energy from chemicals (fungi)
50
Environmental factors that influence microbial growth:
- temperature
- atmosphere
- pH
- water availability
- nutrients
51
Defined media
All compounds are measures out exactly
Ex. Glucose salts
52
Complex media
Not measured, just a bunch of components put together
Ex. Tsa
53
Selective media
Inhibits growth of certain species, but not all
54
Differential media
Contains substances that microbes change in identifiable ways
55
Candle jar method
- some bacteria grows best with excess CO2.
| - the candle takes oxygen and produces CO2
56
Direct Cell Count
- Counts total number (living and dead)
| - does not guarantee viable cell count
57
What is required for a cell to be viable?
-cell must be capable of multiplying
58
Plate counts
- keep diluting the sample until there are roughly 30-300 cells
- most accurate
- determines colony forming units
59
Membrane filtration
- Runs bacteria through a filter & they get stuck.
| - best way to get viable count with a dilute sample
60
Most probably number method
- estimates cell concentration through dilute series
| - place smaller tube inside larger one to collect the gasses
61
Spectrophotometer
- Measures the difference in how much light is absorbed, which helps determine the growth culture.
- more bacteria--> more absorbed
62
What methods are for viable cell counts?
- plate count
- membrane filtration
- most probably number
63
Anaerobic containers
Useful if microbes can tolerate brief O2 exposure. (Creates anaerobic environment)
64
Are escherichia & salmonella cocci or baccili??
bacillus- rod shaped
65
T/F: Microbes will only grow until the least represented (limiting) nutrient in the medium is used up?
True
