BIOL 200: Chapter 12
34 Cards in this Set
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Associations w/ other species
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Symbiotic: organisms live in close nutritional relationships, required by on or both members
Mutualism
Commensalism
Parasitism
Non symbiotic: organisms are free-living, relationships not required for survival
Synergism
Antagonism
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Mutualism
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obligatory dependent
both members benefit
termites & protozoa/bacteria
deep sea worms & chemoautotrophic bacteria
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Commensalism
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the commensal benefits
other member not harmed
staphylococcus aureus
haemophilus satellite colonies
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Synergism
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members cooperate and share nutrients
ex: soil bacteria
azotobacter: Nitrogen fixer
Cellulomonas: cellulose degrader
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Antagonism
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some members are inhibited or destroyed by others
bacteria inhibiting growth of another or anything = antibiosis
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Gas requirements
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Chemical composition of atmosphere
78% N
20% O
.04% CO2
Oxygen processing is importante!
some microbes need
others = toxic
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Oxygen Metabolism
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Molecular Oxygen = somewhat toxic
can be partially reduced to form reactive oxygen species (ROS)
Love --> hate
aerobe
facultative aerobe
microaerophile
anaerobe
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Aerobe
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can use oxygen in metabolism
Obligate aerobe: requires oxygen
ex: people
Ex: pseudomonas aeruginosa
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Facultative aerobe
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doesn't require oxygen but can use it
staphylococcus aureus
escherichia coli
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microaerophile
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metabolic processes with low levels of oxygen (1-15%)
doesn't grow well in air b/c there's too much oxygen
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anaerobe
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can't use oxygen to perform metabolic processes
obligate anaerobe: can't survive in presence of oxygen
ex: clostridium butyricum
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Defenses against toxic effects of Oxygen Metabolism
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Aerobes generally have defenses against toxic effects
Antioxidants
absorb oxygen radicals so they can't damage other molecules
Glutathione, vitamin C, A, E (ROS use O2 to live)
Ex: enzymes - superoxide dismutase, catalase
Convert ROS to less toxic forms
converts into molecular O2, w…
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Carbon Dioxide Metabolism
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all organisms generally require some amount of CO2
some prefer more amounts than normal (3-10%)
Capnophiles: several different types of pathogens
Candle Jars
Gas Pad
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Environmental factors influence microbial growth rates
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every species has optimal conditions where it grows best
every species has tolerances
minimum required
maximum tolerated
temperature = large contributing factor: controls molecular motion, bacteria can't regulate temp only environment can
can't grow effectively @ all temps
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Measuring Growth
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Growth takes place on 2 levels
individually: cell synthesizes new cell components and increases in size
metabolism
population growth: # of cells in the population increases
based on binary fission
* not always growing as fast as can: nutrients available = huge influence
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Exponential growth
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replication to produce new bacteria
after n generations: 2^n cells
5 generations: 1 - 2 - 4 - 8 - 16 - 32 = 2^5
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Generation time
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how long it takes to divide
doubling time
find from growth curves
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Logarithmic Scale
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straight line relationship between growth and time
makes it easier to read
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Phase 1: lag phase
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Bacteria are preparing to grow
not exponentially growing
fresh food or new environment = takes awhile
adjusting to the new influx of nutrients
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Phase 2: Log Phase
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bacteria grow exponentially
let the good times roll
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Stationary Phase
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nutrients run out and waste products build up
everyone dying
waste building
no replication
over extended time will die
PARTY'S OVER!
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Death Phase
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bacteria death occurs @ an exponential rate
most bacteria die off
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Long Term Stationary Phase
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The # of bacteria begins to decline very slowly
dormant/survival state
not a lot of nutrients needed
dead bacteria release nutrients
some adapt/survive low nutrient conditions
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Growth Curves
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account for different stages of infections
takes time to adjust
replicate like crazy
immune response
fight
we win
they die off
some infections = persistant
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Indirect Growth Measurements
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As bacteria grow turbidity increases
Measure how 'cloudy' a liquid is
OD 600
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OD 600
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Indirect measure
use a spectrophotometer to read how much light is blocked @ 600 nm
light source thru sample into detector, light measured
no bacteria = clear, light
more bacteria = light blocked
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Direct Measurements
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Viable plate counts
CFUs
Hemocytometer
Cell counters
Coulter Counter
Flow Cytometer
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Viable Plate Count - CFUs
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CFU = colony forming units
bacteria formed colony on plate of auger
seeing # of CFUs on plate
detects living cells
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Hemocytometers
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a bit of culture on a glass slide etched w/ grid
look under microscope & count how many there are
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Cell Counters
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Coulter Counters
when light is blocked counts bacteria
Flow cytometer
detectors, lasers looking @ fluorescent molecules
suspend in liquid detector counts & tells about size/shape/gram type!
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Characteristics of microbial Populations
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Biofilm formation
Quorum sensing
Human body is a rich habitat for symbiotic bacteria, fungi, and some protozoa = normal microbial flora
Biofilms
form when organisms attach to a substrate by some form of extracellular matrix that binds them together in complex organized layers
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Biofilms
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almost all species of microorganisms can make them
not only bacteria but archaea, algae, etc.
will form on basically every stable moist surface on earth
cover structure of most natural environments
many medical implants
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Biofilms & Quorum Sensing
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Bacteria have way to sense/communicate w/ other bacteria
way to coordinate expression of genes based on population density
communicate and cooperate in the formation & function of biofilms
Quorum sensing
the release or sensing of molecules correlated to population density
signaling…
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Biofilms & Quorum sensing cont.
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find unoccupied substrate
stick together
replicate to threshold
inducers
sensed by bacteria & cause changes in transcription/translation of chromosomes
control proteins being made
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BIOL 200: Chapter 11