Lab Study Guide for Midterm
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crystal violet dye, methylene blue, safranin. Used to stain transparent cytoplasm so they are more visible under a microscope
"alkaline" positively charged chromogen which forms an ionic bond w/ negatively charged bacterial cell, thus coloring the cell
identify positive vs. negative bacteria, first crystal voilet, second iodine, third alcohol, fourth safranin. Negative= red. Positive= purple
Schaeffer-Fulton method of identifying spore forming bacteria. First malachite green then steam bath for 10 minutes. Last safranin stain. Spores are green and vegetative and spore mother cells are red (REVERSE HOLLY leaf/berry)
Standard plate count
estimate population density in a liquid sample by plating a very dilute portion of that sample & counting the # of colonies it produces. V1D1=V2D2. End result is # of colony forming units
selective & differential. contains lactose, bile salts, neutral red and crystal violet. Red result=acidic/lactose fermenters.
EMB (Eosin Methylene Blue) lab
selective and differential. contains peptone, lactose, sucrose, eosin and methylene blue. Lactose fermenters turn dark purple/black. select for gram negative. E.coli=black accompanied by green metallic sheen.
Phenol red broth
differential. contains peptone and phenol red dye. Yellow result =acidic. Pink or magenta above ph of 7.4. Gas production = bubble in durham tube
Blood agar lab
B hemolysis= complete destruction of RBCs/hemoglobin ad results in a clearing of the medium around the colonies. A hemolysis= partial destruction of RBCs/hemoglobin and produces a green color around colonies
Mannitol salt plate
contains mannitol, 7.5% NaCl, phenol red. Yellow with yellow halo=acidic/able to ferment. Red around neutral pH. Pink=alkaline. Selective & Differential.
contains sodium citrate as sole carbon source and ammonium phosphate as sole nitrogen source and Bromthymol blue dye. As ph goes up the medium changes from green to blue. Test evaluates organism's ability to break down CARBON. Blue = positive for citrate
combinational media used for determination of sulfur reduction, indole production from tryptophan and motility. Black precipitate indicates bacteria are capable of reducing sulfur. Add Kovac's red, if shows red it is postive for Indole production. Positive motility=turbid.
combinational media containing peptone, glucose, and phosphate buffer. used to detect bacteria positive for mixed acid fermentation. Red= acidic (positive). Yellow= pH 6.2.
contains beef extract & soluble starch. bacteria that are positive for amylase and capable of digesting starch are surrounded by a halo of a clearing AFTER being "soaked" in iodine.
Positve for gelatinase appears liquid.
differential. contains urea, peptone, potassium phosphate, glucose and phenol red. Pink= urease-positive organism
Nitrate reductase lab
Gas in durham tube= denitrification. If no gas add Reagent A & B, if turns Red is positive for nitrate reduction to nitrite. If no change add zinc, if turns Red at this point it means nitrate was not reduced by organism therefore is negative for nitrate reductase. If no color change after addition of zinc it is positive for nitrate reductase.
identify bacteria with oxidase. positive will produce a purple-blue IMMEDIATELY
Catalase converts hydrogen peroxide into water and gaseous oxygen. Catalase positive bacteria bubbles immediately
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