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49 Cards in this Set
- Front
- Back
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General plating methods
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-measure number of viable cells
-population size is expresed as colony forming units (CFU) dilutions of populations are plated on suitable solid medium-->count # of colonies-->calc # of cells in population |
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If there are 68 colonies on the 10^3 dilution plate of a serial diultin, what is the concentration of viable cells in the original specimen?
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68 colonies=68 cell/0.10mL=680 colonies/mL X 10^3--> 6.80 X 10^5 cells/mL in the original specimen
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If there are 6.80X10^5 cell/mL in the original specimen, approximately how many colonies will there be on the 10^3 dilution plate?
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Viable counting methods
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-spread and pour plate techniques
-results expressed as colony forming units (CFU) |
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Advantages and disadvantages to plating methods?
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Measurement of cell mass
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Describe the setup for the continuous culture of bacteria
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In what state of growth are cells in a continuous culture system?
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How can the growth rate in a continuous culture system be controlled?
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Dilution rate
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Rate at which medium flows through vessel relative to vessel size
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Turbidostat
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regulates the flow rate of media through vessel to maintain a predetermined turbidity of cell density. No limiting nutrient. Operates best at high dilution rates.
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Importantce of continuous culture methods
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Extremophiles
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Grow under harsh conditions that would kill most other organisms
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Grwoth limitation by environmental factors (2)
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-Leibig's law of the minimum
-Shelford's law of tolerance |
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Leibig's law of the minimum
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Totla biomass of organism determined by nutrient present at lowest concentration
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Shelford's law of tolerance
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Above or below certain environmental limits, a microorganism will not grow, regardless of the nutrient supply
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____ is absolutely required for microbial growth
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Water
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Water activity (aw)
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How do microorganisms maintain osmotolerance?
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Halophiles
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Grow optimally at >0.2M
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Extreme halophiles
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Require >2M
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Acidophiles
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Growth optimum between pH 0 and pH 5.5
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Neutrophiles
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Growth optimum between pH 5.5 and pH 7
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Alkalophiles
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Growth optimum between pH 8.5 and pH 11.5
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pH
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Cardinal growth temperatures
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-minamal
-maximal -optimal |
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Adaptations of thermophiles (3)
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(1) protein structure stabilized by a variety of means
(2) histone-like proteins stabilze DNA (3) membrane stabilized by variety of means |
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Adaptations
-Protein strucutre stabilized by a variety of means |
-more H bonds
-more proline -chaperones |
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Adaptations
-Membrane stabilized by variety of means |
-more saturated ,more branched and higher molecular weight lipids
-ether linkages (archael membranes) |
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What are the five relations to oxygen?
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(1) obligate aerobe
(2) facultative anaerobe (3) aerotolerant anaerobe (4) strict anaerobe (5) microaerophile |
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What are microorgansism sensitive to oxygen and how do they protect themselves?
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*oxygen easily reduced to toxic products -superoxide radical -hydrogen peroxide -hydroxyl radical *aerobes produce protective enzymes -superoxide dismutase (SOD) -catalase |
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Barotolerant organisms
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Adversely affected by increased pressure, but not as severely as nontolerant organisms
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Barophilic organsims
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Require or grow more rapidly in the presence of increased pressure
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Ionizing radiation
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-x rays & gamma rays
-mutations =death -disrupts chemical structure of many moleculs, including DNA |
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Radiation Damage:
Ultraviolet (UV) radiation |
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Photoreactivation
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dimers split in presence of light
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Dark reactivation
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dimers excised and replaced in absence of light
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Radiation Damage:
Visible light |
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Carotenoid pigments
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Protect many light-exposed microorganisms from photooxidation
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How do miroorganisms cope with survival in the natural environment?
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Microbial environments are comlpex, constantly changing and may expose micro's to overlapping gradients of nutrients and environmental factors. Micro's uniquely adapt to changing themselves.
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How do Leibig's Law and Shefford's Law apply to microorganisms?
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What is meant by viable but non-culturable? Why is this important?
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Stressed micro's can temporarily lose ability to grow using normal cultivation methods. Microscopic and isotopic methods for counting viable but noncult. cells have been developed.
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What is quorum sensing?
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Microbial communication and cooperation. Involves secretion and detection of chemical signals.
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Responses to low nutrient levels
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-oligotrophic envrionments
-morphological changes to increase SA and ability to absord nutrients -biofilm surfaces conc. nutrients (bottle effect) -mech to sequester certain nutrients |
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Processes sensitive to quorum sensing: gram negative bacteria
Provide example for each |
-bioluminescence; Vibrio fischeri
-synthesis and relase of virulence factors; Psedudomonas aeruginosa -conjugation; Agrobacterium tumefaciens -antibiotic production; Erwinia carotovora, Pseudomonas aureofaciens -biofilm production; P. aeruginosa |
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Processes sensitive to quorum sensing: gram positive bacteria
Often meidated by? Provide example for each |
Often mediated by oligopeptide pheromone
-mating (Enterococcus faecalis) -transformation competence (Streptococcus pneumoniae) -sporulation (Bacillus subtillis) -production of virulent factors (Staphylococcus aureus) -development of aerial mycelis (Streptomyces griseus) -antibiotic production (S. griseus) |
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What is a biofilm?
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Complex, slime enclosed colonies attached to surfaces
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Why are biofilms important?
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Can be formed on any conditioned surface. When form on medical devices such as implants, often lead to illness.
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How does a biofilm form?
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Microbes reversibly attach to conditioned surace and release polysaccharides, proteins, and DNA. Additional polymers are produces as biofilm matures. Interactions occur among the attached organisms.
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