The ones that need review Flashcards
(47 cards)
Concerns in testing:
Bias (experimenter/subject), record of procedure, reproducibility, statistical significance, qualitative/quantitative, correlation/causation
Define: specificity
True pos result from true pos sample
Random error of pH meter:
Contamination, improper mixing, improper reading
Variables for effectiveness of heat killing:
Temp, time, conductance
Autoclave - how does it work? what are the temp/pressure standards?
As pressure is increased, boiling point increases.
As boiling point increases, temperature increases.
15 PSI = 121ºC
T and A equation:
A = log (1/T)
DNA from absorbance equation:
[DNA] = A * dilution factor * 50
Absorbance for bacteria:
595-600 nm
A260/A280 of protein? DNA?
0.55
2, but 1.8 is good
Biuret assay:
Indirect protein assay. Measurement of colour change when CuSO4 reacts with peptide bonds under alkaline solutions. Turns purple (540 nm). Useful to 10 mg/mL.
Thumbs down: takes 15 minutes.
Bradford assay:
Indirect protein assay. Measurement of colour change when Coomassie Blue binds protein. Unbound dye has a max abs of 465 nm; bound dye has a max abs of 595 nm.
Thumbs down: Reaction varies with AA sequence (likes basic ones) and protein function. Upper limit for detection is 1 mg/mL. Dye may precipitate with detergent.
Resolution equation:
R = 0.61 λ / NA NA = n sin θ θ = half the angle that light enters the lens n = refractive index of the medium between subject and lens
Morphologies:
Cocci, bacilli, vibrio, spirochetes, spirillas
Arrangements and groupings:
Pairs (diploboth)
Clusters (staphylococci)
Chains (streptoboth)
Gram pos:
Lots of pep layers.
Teichoic acid makes it negative.
Ex: pneumonia, s. aureus, botulism, anthrax
Gram neg:
One pep layer, one phospholipid layer.
Ex: e. coli, gonorrhea, flu, cholera
Stain: Gram
CV, iodine, acetone, safranin.
Stain: acid fast
For fatty cell walls that repel Gram stains. Primary dye is carbol-fuschin, which has a high affinity for waxy mycolic acids. Decolour with acid-alcohol. Counterstain with methylene blue.
Positive stains red, negative stains blue.
Ex: tuberculosis, leprosy
Glycocalyx:
Sugars and proteins. Increases pathogenicity. May produce biofilms, which can help bacteria stick to a surface.
Ex: S. mutans and plaque (calcified capsules)
Negative stain:
Allows visualization of the glycocalyx. Nigrosin dye is bulky and negative charged so it doesn’t stick to bacteria. Thin film prep without fixing cells. Additional staining (CV) needed to visualize bacteria.
Leifson stain:
For thickening the flagellum.
CV and a mordant.
WHICH BACTERIA MAKE ENDOSPORES?
Gram pos. Bacillus (anthrax, insecticides) and clostridium (tetanus, botulinum, gangrene)
Endospore stain:
Visualization of endospores. Malachite green is steamed into the endospores. Counterstain with safranin.
What do aerobes do with free radicals?
Detoxify them with catalase