Lab 5-Streak plate isolation and dilution series Flashcards
Microbial cultures prepared from body fluids and environmental samples all both considered
mixed cultures.
True / False
True
A pure culture must be obtained before a microbiologist is able to perform meaningfully
biochemical testing.
True / False
True
Since you are working with mixed cultures and attempting to isolate single colonies it is not
necessary to flame your inoculating loop when moving from quadrant 1 to 2, 2 to 3 and 3 to 4
while performing the streak plate method of colony isolation.
False
Ideally a single CFU would be derived from a single initial cell.
True
A dilution series may be used to determine the titer of a liquid bacterial mixed culture, such as a
clean-catch urine sample.
True
From class notes and reading exercise 1-4 in your lab manual; which of the following is not a
recommended method you might employ to isolate single colonies from a mixed culture?
Dilution series method
From your class notes, experience and reading of exercise 1-4 in your lab manual; which of these
methods did you utilize when inoculating agar slants while practicing sterile technique?
Zig-Zag streak method
A CFU may be derived from all of the following accept?
All of these may lead to CFU formation
- A single cell
- A pair of cells
- Clumps of cellular debris
- Chains or clusters of cells
Which of the following best describes the objective of streak plate isolation?
Spread the microbes over the surface of the agar using a pattern to decrease the density of
microbes until we obtain distinct colony forming units.
The sheep’s blood agar we used in class is an example of which kind of media?
Selective
When inoculating an agar plate using a cotton swab from a throat culture it is important to
remember to?
Roll the head of the swab so that you expose its entire surface to the agar.
I obtain a 2 milliliter blood sample and take 1 ml and dilute it into 9 mls of sterile saline. I then
take 1 ml of that saline and place it in another 9 mls of saline. Next, I repeat the saline dilution
step three more times. What is the final dilution of my sample?
1:100,000
Which of the following is not true about the serological pipettes we used in lab?
You draw the solution into the pipette barrel using the plunger on the pipette pump.
Which of the following describes the plating method used in our dilution series exercise.
Even, full-plate spread
An ideal plate to use to determine sample titer in the dilution technique would contain about
how many CFUs?
Fifty-one to three hundred
