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