Bacterial Growth Flashcards
- Growth: colony & species
- Reproduction: binary fission
- Responsiveness: environmental situations
- Metabolism
Processes of life
Bacterial growth curve
- Lag phase: preparing for growth, flat slope
- Log phase: growth happening quickly, steep curve
- Stationary phase: leveling off, waste build up, no nutrients, endospore formation
- Death phase: cells begin to die, unless the formed endospores
Microbial growth: direct methods
Viable plate counts
Membrane filtration
Microscopic counts
Serial dilution to get plates that are countable
Between 25 and 250 colonies
Direct
Viable plate count
Filter large quantities of liquid/solution through a filter (membrane), press membrane to plate and count # of colonies
Direct
Membrane filtration
Use a grid and section on grid to count bacteria
Not accurate- not able to tell if bacteria is alive or dead
Microscopic counts
Microbial growth:indirect method
Metabolic activity
Dry weight
Turbidity
Indirect method: metabolic actitivty
Indirect
Measure amount of by product (waste) to estimate the # of bacteria
Ex: measure decease in pH
Remove media & take weight of bacteria divided by the approximate weight of once cell to estimate the amount of
Indirect
Dry weight
Measure cloudiness of the culture using a spectrophotometer
Turbidity
Microbial growth requirements
- Nutrition
- O2
- Temperature
- pH
- Osmotic pressure
Chemical analysis of microbial cytoplasm can indicate
Nutritional requirements
Compounds a microbe cannot make itself but must gather from immediate environment
Essential nutrients
Elements everything living thing needs
Carbon
Nitrogen
Phosphorus
Hydrogen
Oxygen
Sulfur
Minerals
Magnesium
Iron
Postassium
Trace elements
Cobalt
Copper
Manganese
Nickel
Zinc
Molybdenum
Nutrients: sources of carbon
Autotrophs
Heterotrophs
Use inorganic source of carbon to make organic compounds inside their cells
Autotrophs
Catabolism organic molecules(proteins, carbs, amino acids) to make organic compounds
Heterotrophs
Nutrients: source of energy
Phototrophs
Chemotrophs
Extract energy from absorption of light
Photographs
Extract energy from oxidation-reduction reactions that remove electrons from high energy compounds to produce lower energy compounds
Chemotrophs
Get energy from rocks/soul components
“Eat rocks”
Lithotripsy
Eat organic macromolecules
•proteins, carbs, lipids and nucleic acids
Organotrophy
O2 requirements
O2 is essential for obligate aerobes(final electron acceptor in ETC)
O2 is deadly for obligate anaerobes
Steal electrons from anywhere in the cell if it doesn’t bond with e- & H
Enzymes convert to safer compounds:
1. Superoxide dismutase: takes free O2, converts it to hydrogen peroxide
2. Catalase- remove an O2 to give us H2O and O2
Superoxide radicals
Use O2 in the ETC and have oxygen detoxifying enzymes
Obligate aerobes
No O2 and no oxygen detoxifying enzymes
Obligate anaerobes
Use O2 in the ETC, fermentation, and have oxygen detoxifying enzymes
Facultative anaerobes
No O2 for the ETC and have O2 detoxifying enzymes
Aerotolerant anaerobes
Use O2 for the ETC and produce low concentrations for O2 detoxifying enzymes
Microaerophiles
Microbial growth: temperature
Microbes cannot control their temperature
It affects rate of motion, membrane fluidity, nutrient transport
Psychrophiles
Like cold temperatures
Mesophiles
Human body temperature (most pathogens)
Overlap with psychrophiles
Thermophiles
Like higher temperatures.
Pathogens don’t grow here
Hyperthermophiles
Like very hot temperatures (gysers & hot springs)
No pathogens
The measure of how acidic or basic a solution is.
Influences growth by alternating protein shape = changes in protein activity
Acids release hydrogen ions
Bases release hydroxide ions
Microbial growth: pH
Types of pH
Acidophiles
Neurtalophiles : typical pathogens
Alkaliphiles
Physical effects of water: microbes require water to dissolve enzymes & nutrients required in metabolism
Water is important reactant in many metabolic reactions
Microbial growth: water pressure
Osmotic pressure: pressure on the feel d/t water moving in or out according to concentration gradient
Hydrostatic pressure: pressure that water exerts on a cell from outside
Typers of physical effects on water
Microbial growth: salt
Species that evolved to require high salt concentrations are known as : halophiles
Symbiosis is any type of a close & long term biological interaction between 2 different organisms
Symbiotic relationships
Types of symbiotic relationships
Mutualism- both species benefit
Commensalism- ones species benefit & other is not affected
Parasitism- one species benefit & other is harmed
2 organisms that do not have interdependent relationships
Nomsymbiotic relationships
Synergism- both species benefit each other but can grow independently of each other
Antagonism- both species are going to restrict each other growth
Types of non symbiotic relationships
Types of culture media
Defined/synthetic medium
Complex/natural medium
Enriched medium
Comments added in precise amounts
H2O, salts, carbon, nitrogen & energy sources
Defined/synthetic medium
Nutrient-rich, but poorly defined
Concentration & composition unknown
Complex/natural medium
Specialized for one special organism/fastidious organisms
Enriched medium
Favor growth of one organism over another
Selective media
Expose biochemical differences between 2 species that grow equally well
Differential media
