Lecture 3 Microbial Growth 2.0 Flashcards
Prokaryotic cells divide by
Binary fission
What type of growth do prokaryotic cells divide by?
Exponential growth: population doubles each division
What is an example of exponential growth starting with 2?
2, 4, 8, 16, 32
What time does it take for the population to double?
Generation time
Microbial growth is defined as an _______ in the number of cells in a population
Increase
What is Nt?
Number of cells in a population at time, t
What is N0?
Initial number of cells
What is n?
Number of generations at that point?
Most bacteria attach to surfaces and live in polymer encased communities called _________
Biofilms
Step 1 of biofilm
Free cells adhere to surface and multiple
Step 2 of biofilm
Release polymers to which unrelated cells may attach and grow
Step 3 of biofilm
Extra polymeric substances (EPS) give slimy appearances
Step 4 of biofilm
Nutrients and wastes pass through characteristic channels
Step 5 of biofilm
Cells communicate with one another via chemical channels
Dental plaque is _______
leads to ______ and _____
Biofilm
Tooth decay, gum disease
Most _________ seem to involve biofilm
infection
Microbes within bioflims are often ______ to immune system and antibiotics
Resistant
What is the industrial concern of biofilms?
Accumulation in pipes, dranes
- hundreds of times more resistant to disinfectants
Biofilms are helpful for what?
Bioremediation, wastewater treatment
Microorganisms regularly grow in close association with many different _______
species
Strict anareobes can grow in mouth if others consume ______
O2
Metabolic waste can serve as ______ of other
Nutrient
Interactions of mixed microbial communities are
Competitive
Some gram negative bacteria ______ system to inject toxic compounds directly into competing bacteria
Type VI secretion system
What is pure culture?
Population of cells derived from a single cell
allows study of a single species
What is an enrichment culture?
Used to isolate organism present as only a SMALL fraction of mixed population
In enrichment cultures, relative concentration of target organism increases or decreases?
Increases
What is direct cell counts
Total number
Living + dead
What are cell counting instruments?
Coulter counter, flow cytometer
How is total cell count determined? (equation)
1/volume held in square (in mL)
Then multiple that by number of cells
What is viable cell count?
Cells capable of multiplying
What media is used for viable cell counts?
selective, differential
What is plate counts
Single cell gives rise to coony
What shows how many cells were in a sample?
Number of colonies
Plate gets diluted to obtain how many colonies to produce a countable plate?
30 to 300
What to plate counts determine?
Colony forming unites (CFUs)
What is membrane filtration?
Known volume is passed through a sterile filter
Filter is incubated on agar medium
What does membrane filtration do?
It captures and concentrates microbes by filtration
How do you measure biomass?
Measure cell mass instead of number of cells
Turbidity of microbial suspension is proportional to what?
Concentration of cells
What measures biomass?
Spectrophotometer
What does a spectrophotometer show?
more cells present = less light
spectrophotometer measurement is effective only for what?
High concentration of cells
How is pure culture obtained?
Aseptic technique
Cells grown on pure culture contain nutrients dissolved in water, can be _______ or _______
liquir broth or solid gel
In a pure culture, single cell will multiply to form a _______
colony (aprox. 1 million cells)
What is used to solidify medium?
Agar
What can enter in a petri dish?
air, excludes contaminants
What is the simplest, most common method for isolating
Streak-plate method
After incubation of a streak plate, what do separate cells form
distinct, isolated colonies
a pure culture can be maintained as what/
stock culture
How is a stock culture maintained?
Stored in fridge as agar slant
cells can be frozen at -70 degrees for long term
mized with glycerol to prevent ice crystal formation
Can be freeze fried
What is a closed system?
Culture in which nutrients are not added, nor waste is remoced
What does a closed system include
Microorganisms grown on agar plates or in tubes or flasks of broth
What curve is seen in closed broth culture?
Growth curve
in a lag phase, what happens to number of cells?
Does not increase
what do the cells begin doing in a lag phase?
synthesizing enzymes required for growth
in an expontential (Log) phase, what rate do cells divide at?
constant rate
What is measured in the log phase?
Generation time
What does the log phase produce?
primary metabolites
What is produced as nutrients are depleted and wastes accumulate?
Secondary metabolites
What happens in the stationary phase
- nutrient levels are_______
- total numbers are _______
- continue to produce _______
too low to sustain growth
remain constant
secondary metabolites
What happens in the death phase
- total number of cells _______
- cells die at a _______ rate
- grows _______ but slow
decrease
constant
exponential
Phase of prolonged decline
- some fraction _______
- adapted to tolerate _______ conditions
survive
worsened
position of a single cell in a colony determines its _______
environment
What does the edge of a colony mean?
Little competition for O2 and nutrients
What does the center of colony mean?
Depleted O2, accumulation of potentially toxic wastes
Cells at edge of colony may show _______ growth
Exponential
cells in the center of a colony are in the _______ phase
death
What is an open system?
Culture to which nutrients are continually added and waste products removed
What is a chemostat?
Provides an open system that can maintain continuous growth
in a chemostat
- nutrient content and speed of addition can be controlled to achieve _______ growth rate and cell density
- produces relatively _______ population to study response to different conditions
- can maintain cells in _______ phase of growth to harvest commercially valuable products
constant
uniform
log
What are extremophiles
Bacteria that live in harsh environments
What are most of extremophiles?
Archaea
What are the major factors that affect microbial growth?
Temperature, atmosphere, pH, water availability
Degree of psychrophiles
-5 to 15
degree of psychotrophs
15 to 30
degree of mesophiles
25 to 45
degree of thermophiles
45 to 70
degree of hyperthermophiles
70>
Where are psychotrophiles found?
arctic and antarctic regions
What is psychrotrophs important for?
spoilage of refrigerated foods
Thermophiles are common where?
hot springs, compost heaps
Hypertherophiles are usually _______
found _______
Archaea
hydrothermal vents
Solidified agar _______ gas diffusion
Slows
In solidified agar,
- top is _______
- bottom is _______
Aerobic
Anaerobic
What does the position of growth indicate?
O2 requirements
obligate aerobes O2 requirement
Requires O2
Facultative aerobes O2 requirement
Use O2 but don’t require it
Obligate anaerobes O2 requirements
Cannot use O2
Microaerophiles O2 requirement
Require small amounts of O2 only
Aertolerant anaerobes (obligate fermenters)
Can grow O2 but don’t use it
What are Reactive Oxygen Species
Harmful by-products of using O2 in aerobic respiration
What are the two reactive oxygen species?
O2 and H2O2
What is the affect of ROS?
Damages cellular components
What bacteria don’t have the protective mechanisms against ROS?
obligate anaerobes
Almost all organisms growing in presence of oxygen produce which enzyme?
Superoxide dismutase
What does superoxide dismutase do?
Inactivates superoxide by converting it to O2 and H2O2
What does catalse do?
Converts H2O2 —> O2 and H2O
What is the exception to catalase?
Aerotolerant anaerobes
Most bacteria have what pH?
neutral
What do bacteria do if they are in an acidic environment?
Pump out protons H
What do bacteria do if they are in an alkaline environment?
Bring in protons H
Most microbes are
Neutrophiles
What is the pH range of neutrophiles
5-8, optimum is 7
Food can be preserved by increasing
Acidity
What bacteria grows in stomach and produces urease to split urea into CO2 and ammonia?
H. pylori
What does H. pylori do to the acidity of the surroundings?
Decreases
What bacteria grow optimally at pH below 5.5
Acidophiles
Which bacteria has an optimum pH of less than 1
Picrophilus oshimae
What bacteria grow optimally at pH above 8.5
Alkaliphiles
All organisms require what for growth?
water
If solute concentration is higher outside of the cell, what happens?
Water diffuses out, osmosis
Halotolerant
Withstands up to 10% sald
What type of bacteria is staphylococcus in regards to salt tolerance?
Halotolerant
What is halophiles
Requires high salt levels
What are the major nutritional elements for prokaryotes
carbon, oxygen, hydrogen, nitrogen, sulfur, phosphorus, potassium, magnesium, calcium, iron
What type of carbon to heterotrophs use?
Organic carbon
What type of carbon to autotrophs use
inorganic carbon
What is carbon fication
Converts inorganic carbon to organic carbon
What is nitrogen required for?
Amino acids, nucleic acids
What is nitrogen fixation?
Converts N2 gas to ammonia and incorporates into organic compounds
Most organisms use what nitrogen?
ammonia or aminonitrogen
Phospohrus and iron are _______ nutrients
Limiting
What are growth factors
Organic molecules that an organism cannot synthesize
What is fastidious
requires specific and many growth factors to survive
What are phototrophs
obtain energy from sunlight
What are chemotrophs
Extract energy from chemicals
Photoautotrophs
Energy from sunlight, carbon from CO2
Photoheterotrophs
Energy from sunlight, carbon from organic compounds
Chemolithoautotrophs
Energy from inorganic compounds, carbon fro CO2
Chemoorganoheterotrophs
Energy and carbon from organic compounds
What is complex media
Contains variety of ingredients, exact composition is highly variable
What is chemically defined media?
Composed of exact amounts of pure chemicals
is chemically defined media or complex media faster?
Complex media… Chemically defined is slower as cells must synthesize components
What can grow in complex and chemically defined media?
E. coli
What is selective media
Inhibits growth of certain species in a mixed sample, allows growth of species of interest
MacConkey agar is selective for what/
Gram negative rods
MacConkey agar is differential for what?
Lactose fermentation
What is selective media made up of?
Crystal violet that inhibits gram positive bacteria
bile salts that inhibit non-intestinal bacteria
What is differential media?
Contains substance that microbes change in identifiable way
What type of media is blood agar?
Differential
in blood agar, what does beta hemolysis do?
produces clear zone
In blood agar, what does alpha hemolysis do?
Produces zone of greenish partial clearing
REFER TO SLIDE 38 for pictures
Which one could be MacConkey?
THIS IS ON EXAM…. MUST REVIEW
Differential
Where can aerobes and facultative anaerobes be incubated?
in air, 20% O2
Where do medically important bacteria (aerobes) grow best in?
Increased CO2
Some medically important aerobes are
Capnophiles…REQUIRE increased CO2
What method is used to incubate capnophiles?
Candle jar
What does the microaerophilic require?
Lower O2 concentration achieved by candle jar
How do you give optimal growth for microaerophilic bacteria?
Gas tight contain with chemical packet
Obligate anaerobes are sensitive to
O2
Anearobes are put into anaerobic containers if they can tolerate
Brief O2 exposure
What are ways to detect cell products?
pH indicators, Durham tubes (inverted tubes to trap gas), CO2 productions
