Microbial nutrition and growth Flashcards
Microbial environment used to be completely anoxic, what is anoxic
Without oxygen
What bacteria caused change in oxygen levels
Cynobacteria
More oxic
More photosynthetic
What are examples of energy sources for microbes
Carbon
Nitrogen
What do chemoorganotrophs make and why is this useful
Hydrogen used by chemolithotrophs
What is a phototroph
Photosynthetic microbes
What is a chemotroph
Obtain energy from chemicals
What do chemoorganotrophs use
Organic compounds
What do chemolithotrophs use
Inorganic compounds
What has oxygen as it’s terminal electron acceptor
Aerobe
What is an autotroph
Uses carbon dioxide as sole carbon source
What is a heterotroph
Uses carbon from complex compounds
What examples are there of nutrient types
Macronutrients Micronutrients Trace metals Growth factos Vitamins
What are examples of macronutrients
Carbon
Hydrogen
Oxygen
Nitrogen
What are the possible sources of carbon
Carbon dioxide (not all photosynthetic) From complex compounds
What are the possible sources of nitrogen
Gaseous N2 e.g. nitrogen fixing bacteria
Inorganic N e.g. denitrifying bacteria
How can other nutrients be taken up into cell
Taken up as trace elements dissolved in water
Some as gases
Some as nutrients actively transported into cell
What are the essentials for microorganism growth
Nutrient source Water Temperature pH Atmospheric conditions
Why is water needed in microorganism growth
Most microorganisms can only absorb soluble chemicals
Rigid cell wall prevents cell bursting
What does hypertonic media cause
Cell loses water and shrinks
What does hypotonic media cause
Cell swells
What (water) environment do most microbes live in
Slightly hypotonic
What is an extreme thermophile
Extreme heat loving
What is a thermophile
Heat loving
What is a mesophile
Middle temperature range
What is a psychrophile
Cold loving
What is the normal pH range for eubacteria
6-8
What is the minimum pH for microbial growth
4
What is the maximum pH for microbial growth
9
What must the intracellular pH be
Maintained within 2 pH units of neutral (7)
How do bacteria survive in low pH
They adjust their intracellular pH in response to changes in extracellular pH
What does the cytoplasmic pH have to be
Stay close to neutral
What is an obligate aerobe
Requires oxygen
What is a facultative aerobe
Doesn’t need oxygen, but will use it if there
What is a microaerophile
Requires lowered oxygen levels
What is an aerotolerant anaerobe
Grows best without oxygen but can tolerate its presence
What is a strict anaerobe
Can’t tolerate oxygen
What are the laboratory conditions for growth
Correct media containing all nutrients and solute concentration
Correct incubation temperature
Correct atmospheric conditions
How is the growth of bacteria and cell division described in a graph
Rate of increase is an exponential function
What is binary fission
Transfer of genetic material before septum formation or will not be viable cells
What is the lag phase in batch culture growth
Cells initiate growth
Try acclimatise to new environment
What is the exponential phase in batch culture growth
Cell number doubles in minimum time
What is the stationary phase in batch culture growth
Cell growth slows and eventually stops
What is the death phase in batch culture growth
Number of viable cells slowly declines
When does growth in batch culture stop
When nutrients limited or a by-product of growth becomes toxic
What processes use continuous cultures
Basis of fermentation
- making antibiotics
- nutrients continually replaced
- cell numbers kept constant
- toxic metabolic products washed out
