Chapter 4 Flashcards
can be found growing many conditions, including extreme ones:
Prokaryotes
Prokaryotic cells divide by
binary fission
population doubles
each division
Exponential growth
is time it takes for the
population to double in number
Generation time
how to calculate growth
take pic of slide 4
number of cells in population at time t
N of t
initial number of cells
N of 0
number of generations at that point
n
pathogen in potato salad at picnic in sun
- Assume 10 cells with 20 minute generation time
- N0 =
- n =
- Nt =
- N0 = 10 cells in original population
- n = 12 (3 divisions per hour for 4 hours)
- Nt = N0 x 2n = 10 x 212
- Nt = 10 x 4,096
- Nt =
sense changes, adjust to surroundings
Cells
Most live in polymer-
encased communities
termed
biofilms
Cause slipperiness of rocks
in stream bed, slimy “gunk”
in sink drains, scum in toilet
bowls, dental plaque
biofilms
Biofilm formation
- Free cells adhere to surface and multiply
- Release polymers to which unrelated cells may attach and grow
- Extra polymeric substances (EPS) give slimy appearance
- Nutrients and wastes pass through characteristic channels
Cells communicate by
synthesizing chemical signals
shields microbes growing within
Biofilm structure
regularly grow in close association
Prokaryotes
use type IV secretion system to
inject toxic compounds into competitors
Gram negative bacteria
defined as population of cells derived from a single cell
Pure culture
Pure culture obtained using
aseptic technique
Minimizes potential contamination
aseptic technique
Contains nutrients dissolved in water
culture medium
Cells grown on
culture medium
what can culture medium be
broth (liquid) or solid gel
Growing Microorganisms on Solid Medium
Need culture medium, container, aseptic conditions,
method to separate individual cells
what temp agar is sterilized
(Liquid > 95°C; solid < 45°C)
Petri dish
plate
Simplest plate method, most commonly used method for isolating
Streak-plate method
Spreads out cells to separate
Streak-plate method
Streak-plate method obtain colonies from
single cells
Visible colonies contain how many cells
1 million cells or more
Pure cultures maintained as
stock culture
Prokaryotes grow on
agar plates
in tubes or
flasks of broth
what kind is systems are these: agar plates, in tubes or flasks of broth
closed systems
Yields characteristic growth curve
batch cultures
another name for closed system
batch cultures
Growth curve
don’t need to know all mediums in slide 38
how cells divide in log phase
Cells divide at constant rate
what is measured during log phase
generation time
which phase is Most sensitive to antibiotics
log phase
what does log phase produce
Production of primary metabolites for growth
Secondary metabolites production occurs as nutrients are depleted and wastes accumulate
what phase is transferred to new medium
lag phase
how do cells increase in lag phase
Number of cells does not increase – no division yet
what phase Begin synthesizing enzymes required for growth
lag phase
what phase has Nutrient levels too low to sustain growth
Stationary phase
how do cells multiply in Stationary phase
•Total numbers remain constant
•Some die; others grow
does the secondary phase produce anything
secondary metabolites
what happens to cell numbers in Death phase
Total number of viable cells decrease
Cells die at constant rate
in what phase does Some fraction may survive at first - Adapted to tolerate worsened conditions.
Phase of prolonged decline
number of cells in Phase of prolonged decline
Eventually, most die except a few (survival of the fittest).
determines its environment
Position of single cell in colony
where in the cell colony has O2, nutrients
the edge
has depleted O2 and nutrients, more wastes (potentially toxic)
center
Colony may range from exponential growth at what to death phase in what
edges
center
another name for open system
continuous culture
required to maintain continuous growth
Open system
Nutrients added, wastes removed continuously
Open system
can maintain continuous growth
chemostats
Continually drips fresh medium into culture in chamber
chemostats
chemostats maintain cells in what phase
log phase of growth to harvest commercially valuable products
extremophiles
live in harsh environments
Major conditions that influence growth
Temperature
•Atmosphere
•pH
•Water availability
optimum growth : –5° to 15°C
Psychrophiles
temp requirements
15° to 30°C
•Important in food spoilage
Psychrotrophs
25° to 45°C
Mesophiles
type of Mesophiles
Pathogens 35° to 40°C
45° to 70°C
Thermophiles
70° to 110°C
•Usually members of Archaea
•Found in hydrothermal vents
Hyperthermophiles
Proteins of thermophiles resist
denaturing
slows spoilage by limiting growth
Refrigeration (~4°C)
preserves food; not effective at killing microbes
Freezing
where is leprosy most common
coolest regions (ears, hands, feet, fingers)
growth characteristics: grows only when oxygen is available
use of oxygen: requires oxygen for respiration
protection mechanisms:dismutase and catalase
growth characteristics: grows best with oxygen but can without it
use of oxygen: respiration
protection mechanisms: dismutase and catalase
growth characteristics: can’t grow with oxygen present
use of oxygen: no use
protection mechanisms: does not dismutase and catalase
growth characteristics: grows only if small amount of oxygen is present
use of oxygen: respiration
protection mechanisms: dismutase and catalase
y
growth characteristics: grows equally well with or without oxygen
use of oxygen: does not use
protection mechanisms: dismutase
Harmful by-products of using O2 in aerobic respiration
Reactive oxygen species (ROS)
Almost all organisms growing in presence of oxygen produce enzyme
superoxide dismutase
Almost all Reactive oxygen species (ROS) produce what
catalase
catalase
Convert H2O2 to O2 and H2O
Most bacteria maintain constant internal pH, typically near
neutral
Pump protons out to
increase pH
Pump protons into
decrease pH
Range of pH 5 to 8; optimum near pH 7
neutrophiles
grow optimally at pH below 5.5
Acidophiles
grow optimally at pH above 8.5
Alkaliphiles
make water unavailable to cell
Dissolved salts, sugars
used to preserve food
Salt, sugar
withstand up to 10% salt concentration
Halotolerant
require high salt concentrations
Halophiles
Major elements examples
carbon, oxygen, hydrogen, nitrogen, sulfur,
phosphorus, potassium, magnesium, calcium, and iron
Trace elements examples
cobalt, zinc, copper, molybdenum, mang
Component of amino acids, lipids, nucleic acids,
and sugars
Carbon, oxygen, and
hydrogen
Component of amino acids and nucleic acids
Nitrogen
Component of some amino acids
Sulfur
Component of nucleic acids, membrane lipids, and ATP
Phosphorus
Required for the functioning of certain enzymes; additional
functions as well
Potassium, magnesium,
and calcium
Part of certain enzymes
Iron
use organic carbon
Heterotrophs
use inorganic carbon as CO2
Autotrophs
what is the process of using inorganic carbon as CO2
(carbon fixation)
N2 to ammonia
Nitrogen fixation
Organic molecules that an organism cannot synthesize;
must be present in the environment examples
Amino acids, vitamins, purines, pyrimidines
Only grow if these growth factors are available
Amino acids, vitamins, purines, pyrimidines
have complicated nutritional
requirements
fastidious
Energy sources
Sunlight, chemical compound
obtain energy from sunlight
Phototrophs
extract energy from chemicals (ex:
Sugars, amino acids, fatty acids)
Chemotrophs
inorganic chemicals examples
hydrogen sulfide, hydrogen gas
energy from sunlight
carbon from CO2
Photoautotrophs:
energy from sunlight
carbon from organic compounds
Photoheterotrophs
energy from inorganic compound
carbon from CO2
Chemolithoautotrophs
or
chemoautotrophs,
or
chemolithotrophs
energy and carbon from organic compounds
Chemoorganoheterotrophs
or
chemoheterotrophs,
or
chemoorganotrophs
contain a variety of ingredients
Complex media
examples of Complex media
meat juices, digest, peptones
composed of exact amounts of
pure chemicals
Chemically defined media
can grow in complex media or chemically defined
media
E. coli
inhibit growth of
certain species in a mixed sample
Selective media
contain substance that microbes
change in identifiable way
Differential media
not selective or differential
Routine medium
incubated in air (~20% O2)
Aerobic
Require lower O2 concentrations than achieved by
candle jar
Chemical reaction reduces O2 to 5–15%
Microaerophilic
obligate anaerobes sensitive to O2
Anaerobic:
useful if microbe can tolerate brief
O2 exposures
Anaerobic containers
provides more stringent approach
Anaerobic chamber
used to isolate organism that
constitutes small fraction of mixed population
- Provide conditions promoting growth of particular species
- Relative concentration of target organism increases
Enrichment cultures
couting cell total numbers (living plus dead)
Direct cell counts
Direct cell counts instruments
Coulter counter, flow cytometer
counts only cells capable of multiplying
Can use selective, differential media for particular species
Viable cell counts
type of Viable cell counts
Plate counts
single cell gives rise to colony
Plate counts
number of cells you ideally want in Plate out dilution series
30–300 colonies ideal
Plate counts determine
colony-forming units (CFUs)
- Concentrates microbes by filtration
- Filter is incubated on appropriate agar medium
Membrane filtration
is proportional to concentration of cells
Turbidity
how is biomass measured
spectrophotometer
Total weight can be measured
only used for filamentous organisms that do not
readily separate into individual cells for valid plate counts
- Cells in liquid culture centrifuged; pellet is weighed
- Dry weight can be determined by heating pellet in oven
Total weight of biomass
