Microbial Growth Part II Flashcards
Measurement of Microbial Growth can measure changes in 2 things:
number of cells in a population
mass of population
what are the 3 direct cell counts
counting chambers
electronic counters – flow cytometry
on membrane filters
describe counting chambers (3)
Easy, inexpensive, and quick
Useful for counting both eukaryotes and prokaryotes
Cannot distinguish living from dead cells
describe direct counts on membrane filters (4)
- Cells filtered through special membrane that provides dark background for observing cells
- Cells are stained with fluorescent dyes
- Useful for counting bacteria
- With certain dyes, can distinguish living from dead cells
describe direct counts for flow cytometry (4)
- Microbial suspension forced through small orifice with a laser light beam
- Movement of microbe through orifice impacts electric current that flows through orifice
- Instances of disruption of current are counted
- Specific antibodies can be used to determine size and internal complexity
is whether or not a cell is alive or dead always clear cut in microbiology? describe
No it is not always clear cut.
-Cells can exist in a variety of states between ‘fully viable’ and ‘actually dead’
Viable counting methods allows ________ of viable cells
enumeration
describe Spread and pour plate techniques in regards to viable counting methods(3)
- ) diluted sample of bacteria is spread over solid agar surface or mixed with agar and poured into Petri plate
- ) after incubation the numbers of organisms are determined by counting the number of colonies multiplied by the dilution factor
- ) results expressed as colony forming units (CFU); each CFU comes from 1 viable cell
describe Membrane filter technique in regards to viable counting methods (4)
1.) bacteria from aquatic samples are trapped on membranes
2.) membrane soaked in culture media
3.) colonies grow on membrane
4.) colony count determines # of bacteria in sample
(slides 8 and 9 have helpful pictures)
in regards to viable counting methods, if a microbe cannot be cultured on plate media what 2 things can be done?
- ) dilutions are made and added to suitable liquid media (slide 10)
- ) turbidity determined to yield the most probable number (MPN)
describe turbidity/terbidometric measures
12-16
Definitely look at and memorize
describe The Continuous Culture of Microorganisms (3)
- ) Growth in an open system
- continual provision of nutrients
- continual removal of wastes and cells - ) Maintains cells in log phase at a constant biomass concentration for extended periods
- ) Achieved using a continuous culture system
What are 3 Importances of Continuous Culture Methods?
- ) Study of microbial growth at very low nutrient concentrations, close to those present in natural environment
- ) Study of interactions of microbes under conditions resembling those in aquatic environments
- ) Food and industrial microbiology
The Device for continuous cultures is called what? describe this (2)
Chemostat
-Rate of incoming medium = rate of removal of medium from vessel (with wastes and cells)
-An essential nutrient is in limiting quantities
(picture on slide 19)
Most microorganisms grow in fairly moderate environmental conditions. However, some grow under harsh conditions that would kill most other organisms. What are these organisms called?
Extremophiles
slide 21
Table
slide 22-23
READ THIS
Osmosis stuff
a lot of information
what are Halophiles? (2)
- extremely adapted microbe
- grow optimally in the presence of NaCl or other salts at a concentration in range of grater than 0.2M (2-10 %)
what are extreme halophiles? (4)
-extremely adapted microbe
-require salt concentrations of 2M and 6.2M (15- 30 %)
-extremely high concentrations of potassium
-cell wall, proteins, and plasma membrane require high salt to maintain stability and activity
(slide 25)
what is pH? (2)
- measure of the relative acidity of a solution; measure of [H+]
- negative logarithm of the hydrogen ion concentration
what are acidophiles? (2)
- Microorganisms that growth optimum between pH 0 and pH 5.5
- Mostly prokaryotes; many Archaea
what are neutrophils? (2)
- most microorganisms
- growth optimum between pH 5.5 and pH 7
Alkaliphiles (basophiles)? (2)
- Microorganisms growth optimum between pH 8.5 and pH 11.5
- Mostly prokaryotes
- ) Most microorganisms maintain an internal pH near _____ because_______________
- ) can do this by:
- ) neutrality, pH extremes can denature proteins and nucleic acids and kill cells
- ) -the plasma membrane is impermeable to protons
- exchange potassium for protons (H+)
- buffers
describe acidic tolerance response (2)
- pump protons out of the cell
- some synthesize acid and heat shock proteins that protect proteins
Many microorganisms change the pH of their micro habitat by ________________________
producing acidic or basic waste products
Microorganisms are ___________ and cannot regulate their internal temperature
ambitherms
slides 30-32
:)
Microorganisms can be classified into groups by their growth temperature ____
optima
describe the Psychrophile growth temperature optima (2)
- low temperature (optimum temperature below 15ºC and max of 20ºC or below) (range=0-20)
- the most extreme representatives inhabit permanently cold environments
describe the Mesophile growth temperature optima (5)
- Midrange temperature (optimum between 15ºC and 45ºC)
- Warm-blooded animals
- Terrestrial (soil) and aquatic environments
- Temperate and tropical latitudes
- Most microorganisms are mesophiles
describe the thermophile growth temperature optima
high temperature (optimum above 45ºC) ((range=45-85)
describe the hyperthermophile growth temperature optima (2)
-Very high temperature (optimum above 85ºC)
-Inhabit hot environments including boiling hot springs and seafloor hydrothermal vents that can have temperatures in excess of 100ºC
(slides 44 and 45)
what are Psychrotolerant Mesophiles? (2)
- Organisms that can grow at 0ºC but have optima of 20ºC to 40ºC
- More widely distributed in nature than psychrophiles
describe Psychrophile adaptions
slide 41 and 42
Above ~__°C only prokaryotic life forms exist; no eukaryotes
65
describe Thermophile adaptions
slide 46
__________ is the final electron acceptor in the ______________ used in ________________.
Molecular oxygen (O2); electron transport chain; aerobic cellular respiration
All organisms that use aerobic cellular respiration as its only (or one of several ) energy yielding metabolism requires __________________
molecular oxygen (O2)
describe strict aerobes
- usually lives at 20/21% oxygen and will die in the absence of oxygen
- can only do aerobic cellular respiration
describe Microaerophiles (2)
- strict aerobes (will die in absence of oxygen), but can use oxygen only when it is present at levels reduced from that in air
- live in environments with reduced oxygen content (2-10%)
(i. e., in bodies of water)
what are anaerobes?
organisms do not do aerobic cellular respiration, but use some other method of energy metabolism, (thus, they do not require(O2) oxygen and may even be killed by exposure)
what are Aerotolerant anaerobes?
can tolerate some oxygen and grow in its presence (at some level, but usually not 21 % O2) even though they cannot use it
what are strict anaerobes? (2)
- organisms that will die in the presence of any oxygen (live deep in bodies of water and deep in the soil)
- All strict anaerobic microorganisms lack or have very low quantities of superoxide dismutase and catalase
what are Facultative anaerobes (aerobes)? (3)
- organisms that can live in the presence or absence of oxygen
- they do aerobic cellular respiration when oxygen(O2) is present, and some other energy metabolism when oxygen is absent
- Nearly all prokaryotes & fungi are in this category
slide 51 and 52
charts and graphs showing the different types of oxygen using organisms and such; make sure to look at slightly
Several toxic forms of oxygen can be formed in the cell. They include: (4)
Singlet oxygen (O-) Superoxide anion (O2-) Hydrogen peroxide (H2O2) Hydroxyl radical (-OH)
Toxic forms of oxygen can damage _____ and ______. They can lead to ______ and cause _______ when they get up above a certain threshold of protection and repair.
proteins nucleic acids mutations cell death (slide 54)
describe how different organisms deal with toxic forms of Oxygen
-In all cells living in environments with oxygen, enzymes are present to neutralize most of these toxic oxygen species
-Aerobes and facultative aerobes have the most detoxifying enzymes.
-Microaerophiles and aerotolerant anaerobes have less but have some.
-Strict anaerobes – have no detoxifying enzymes
(slide 56)
Anaerobes must be grown without O2. What are the 2 ways in which this can be done?
1.) work station with incubator
2.) gaspak anaerobic system
(slides 58-60)
Microbes that live on land and water surface live at _ atmosphere (atm)
1
*Some Bacteria and Archaea live in deep sea with very high hydrostatic pressures
what does Barotolerant mean?
adversely affected by increased pressure, but not as severely as nontolerant organisms
describe Barophilic (peizophilic) organisms (2)
- require presence of increased pressure to grow
- change membrane fatty acids to adapt to high pressures
describe ionizing radiation (4)
- X-rays and gamma rays
- Can cause mutations at low doses and death at higher doses (sterilization)
- Disrupts chemical structure of many molecules, including DNA
- damage may be repaired by DNA repair mechanisms if small dose
what is a microorganism that is extremely resistant to DNA damage?
Deinococcus radiodurans
describe UV radiation damage(5)
- wavelength most effectively absorbed by DNA is 260 nm
- can cause mutations (low dose) –>death (higher dose)
- causes formation of thymine dimers in DNA
- requires direct exposure on microbial surface
- DNA damage can be repaired by several repair mechanisms
describe visible light radiation damage (2)
-at high intensities generates singlet oxygen (1O2)
(powerful oxidizing agent)
-carotenoid pigments
(protect many light-exposed microorganisms from photooxidation)
Microbial environments are… (3)
- complex
- constantly changing
- often contain low nutrient concentrations (oligotrophic environment)
microbes that grow attached to surfaces are called what? These attached microbes are members of complex, slime enclosed communities called a _____
sessile; biofilm
microbes that grow free floating are called what?
planktonic
Biofilms are _______ in nature in water and can be formed on any ___________
ubiquitous; conditioned surface
describe biofilm formation (2)
- Microbes reversibly attach to conditioned surface and -release polysaccharides, proteins, and DNA to form the extracellular polymeric substance (EPS)
- Additional polymers are produced as microbes reproduce and biofilm matures
describe biofilms (3)
-A mature biofilm is a complex, dynamic community of microorganisms
-Heterogeneity is differences in metabolic activity and locations of microbes
-Interactions occur among the attached organisms
(exchanges take place metabolically, DNA uptake and communication)
slide 72
Last slide :)
