Exam 1 Objectives Flashcards
What are some examples of aseptic techniques?
Flamming your loop/test tubes
Washing hands, wearing lab coat, wiping bench
Why do we use aseptic technique?
To make sure our samples are not contaminated.
What is the proper way to innoculate a streak plate?
Flame loop, dip in isolated colony.
Then do the 4 quadrant technique.
What is the proper way to innoculate a pour plate?
Obtain sample, put in test tube of hot agar.
Pour in empty Petri dish.
Let cool.
How can we transfer bacteria from one culture to another aseptically?
Always flame your loop/needle.
Never let the test tube top touch the bench.
Flame the test tube.
Always cover streak plate.
What are some advantages of viable plate count to other methods to count cells?
Materials are inexpensive
Only counts live cells
What are some disadvantages of viable plate count to other methods to count cells?
Overnight incubation (lots of time).
For a viable cell count how many cells should be in the sample?
Between 30-300 cells.
What can we do to make a viable count?
Dilute the sample.
How do we calculate dilutions?
The number of mL pipetted/the total amount of mL in the tube.
Multiple these fractions together.
How do you innoculate a spread plate?
Used in dilutions, needed amount pipetted onto Petri dish.
Use glass hockey stick to spread bacteria around.
How do we calculate the original cell density (OCD) of a culture?
number of colonies/mL plated * 1/dilution
Why do we express our OCD in colony forming units (CFUs)?
Each of the colonies is presumed to have arisen from only one cell, although this may not be true if pairs, chains, or groups of cells are not completely broken apart before planting.
For this reason, the results of a viable plate count are given in units of colony forming units (cfu)/mL, rather than cells/mL.
How do we improve contrast on a microscope?
Staining- kills cells
Dim the light
How do we improve resolution on a microscope?
Use shorter wavelengths of light
Use oil and immersion lens
