Types of Tests/Experiments Flashcards
exoenzyme production
uses starch, triglyceride, and casein as substrates to show if clearing occurs (+). If clearing occurs, it is positive for that substrate and the specific end product will be in that organism. Uses gelatin as a substrate to show if liquefication (+) occurs, if it does not occur it stays solid.
exoenzymes because they secrete digestive enzymes outside of the cell to digest the macromolecular nutrients surrounding.
Carbohydrate Fermentation
uses sucrose, glucose, and lactose as substrates. organisms are placed in test tube with durham tube. if negative, the tube will be purple. if it is an acid only, it will be yellow. if it is an acid with gas, it will be yellow with gas inside durham tube.
Identification of staph species by using catalase test, mannitol salt agar (MSA), and coagulase test
Catalase test: hydrogen peroxide is used to see if bubbles are formed (+) for an organism. if bubbles form, it can either be staph. or micrococcus. if negative and no bubbles form, it is a strep.
MSA: If (+) for catalase test, place the organism on an MSA plate to see if agar color change occurs. if the plate turns yellow, it is positive for mannitol fermentation and suggests that it is staph aureus.If the plate stays red, it does not fermentate mannitol, so it suggests it is a different kind of staph.
Coagulase test: this confirms that it is either staph. aureus or a different kind of staph. The organism is placed in rabbit plasma, and if positive (solidifies) and confirms staph aureus. only staph aureus can coagulate.
Differentiation of strep species
organisms placed on blood agar
gamma - no clearing and cannot lyse RBCs, found in group D
alpha - incomplete clearing or greening, found in group D, tests for strep. pneumonia and is sensitive to p disk
beta - complete clearing, found in group A, sensitive to a disk, also found in group B, tests for strep. pyogenes
cytochrome oxidase test
the organism is placed on dry slide paper and rubbed with reagent, if positive there will be a color change from pink to purple to black within 60 seconds. this is used to identify Neisseria
SIM medium
Sulfur-indole-motility, allows the determination of H2S production by blackening (FeS) indicator. can use thiosulfate and cysteine as substrates. cloudiness results in motility. black throughout means motility and H2S production. cloudy only in stab line means no motility. black in stab line means no motility but H2S production.
Triple sugar iron agar reactions (TSIA)
differentiates within the butt color, slant color, bubbles, and blackening.
butt color - yellow, if glucose was fermented
slant color - if sucrose/lactose were fermented, the slant will be yellow, if red they were not fermented
bubbles or pushed-up agar - fermentation produced gas and acids
blackening - H2S production
tests for gr (-) rods
IMViC reactions
Indole-methyl red-VP-citrate. tests for e.coli or enterobacter.
indole - uses kovac reagent to test for indole, positive test results in cherry red color change
methyl red - uses methyl red reagent to test for mixed acid producers, tests for pH of 4, positive if it is red
VP test - uses vp reagents to test for acetylmethylcarbinol, positive test results in red color change
citrate test - if citrate can be used by organism, blue color change will occur if positive
litmus test
- tests for lactose fermentation, positive if a pink color
- tests for gas formation, positive if fissures present
- tests for acid curd formation, positive if curding occurs with whey (clear liquid) present as well
- tests for litmus reduction, uses litmus as e- chain acceptor, positive if a color change to white occurs
- tests for casein hydrolysis, proteolysis occurs if cannot fermentate lactose but can hydrolyze it, positive if blue/purple (alkaline)
water testing
qualitative - uses specific amounts of water to test for e. coli, tested by MPN
quantitative - tests for the presence of e. coli. yes, if gas and yellow is present.
food analysis
determines number of bacteria present in original sample. dilutions of sample make it easier to test and get a predictive number. only plates between 30 and 300 can be counted. TFTC or TNTC.
ex. 10 g of food takes up 10ml of volume. if mixed with 90 ml of water, the solution is now 10/100, or 1/10, or 10^-1. if taking 1ml (1/10) and putting it into a 1/100 dilution (.01ml) it would be 1/1000 or 10^-3 dilution.
cheese curding
- hard curd - romano (italy), jarlsberg (switzerland), sharper and harder
- semi-hard curd - gouda (holland), havarti (denmark), coated with wax and have holes (CO2 bubbles) milk scalded first for stretchiness
- semi-soft curd - munster (Germany), ripened from outside in by red smear, strong tastes
- soft curd - brie (France), mold ripened from outside in, longer curing
bacterial transformation
organisms testing for resistance to antibiotics, if transformation did not take place then the organism would not be resistant to the drug so it needs to have the resistance gene in the genome for there to be growth on the plate with the drug.
