Last Quiz Flashcards
Is EMB considered selective, differential, or both?
Both
What components of this medium make it selective and what makes it differential? (EMB)
It is selective because it selects for the growth of gram-negative organisms. It is differential because the agar contains dyes which inhibit the growth of gram positive organisms and forms a precipitate at a low pH.
What can you determine about organisms that can grow on this medium? (EMB)
We can determine that the organism is a gram-negative bacteria
What could metallic green colonies indicate? (EMB)
Indicates a vigorous lactose and/or sucrose fermentation ability typical of fecal coliforms.
What are the components of the phenol red lactose broths medium?
beef extract, sodium chloride, lactose, phenol red, proteose peptone
What can this test (phenol red) tell you about an organism?
It can tell if the organism produces some kind of sugar or ferments. It can also help differentiate gram-negative bacteria by testing pH levels.
(phenol red) what do positive results look like compared to negative?
Positive: yellow
Negative: stays same color/pink/red
(Phenol red) what causes the difference in test result appearances?
If the organism can use carbohydrates, an acid by product is created, which then turns the media yellow
Know how to perform dilutions and explain their purpose
.9 mL of water in every tube. .1mL of dirt in original tube. then .1 mL of mixture from original into the next tube, and then from tube 2 to tube 3, and so on.
Why do we need to use water dilutions for the water project?
to lower the concentration
What is the purpose of the water project?
To create our own question and hypothesis to then test and experiment with
What types of bacteria are we testing for? describe them. (water project)
-gram isolated bacteria
-e. coli
-coliform (fecal bacteria)
what tests are being used for this lab
-microscope and slides
- gram stain reagents
-lactose broths
-agar plates
-emb plates
