Pocket Culturing
An idea for a demonstration to be done by instructor to set up motivation for aseptic technique, pointing out that we are normally surrounded by bacteria, and the role of phage in our environment (in regulating bacterial numbers).
A section of a dollar bill was lightly pressed against a plate's LB-agarose for 90 s.
The dollar is then washed and dried and the plate examined after a day or more.
The plate edge should be wrapped in parafilm, not opened (do not expose yourself or others to amplified numbers of unknown bacteria), and then autoclaved when finished.
$1 on a plate
One Day Later
Two Days Later
One Week Later, Stored at 4 C
After two days it was stored for the remainder of the week at 4 C. Incubating overnight then storing at 4 C until the following class day would probably work well in a classroom.
Notes
I also tried wiping a cell phone with a kimwipe and plating that but it didn't show any colonies.
Label plates with bench number, denomination, year printed, and date. Also write this in your lab notebook.
Students could work on forming predictive hypotheses.
- Write down the denomination of the bill.
- Write the year the bill was printed.
- Score the physical condition of the bill from 1 (crisp, clean, intact, "new" looking) to 5 (worn, torn, creased, stained).
Do you expect any of these factors to be correlated with the number of colonies?
Instructor: Put the plates in 37 C overnight then, wrap with parafilm and keep at room temperature until the next class (not more than a week or move to 4 C).
When you get your plate back do not open it. Count how many colonies you can see. If there are so many as to be uncountable then write this down instead. How many different types of colonies to you see. Write a brief description of each type (but not necessarily every colony): size, color, texture (smooth, fuzzy, etc.).
If you also streaked plates with the host bacteria do any of the bill colonies look similar to contaminants on your plates?
What Links Here
- SEA-PHAGES (← links)
