Absence of Microbe Challenge

Challenge: Sample an Environment where no Microbes are Found

Goal: Get your own personal environmental sample to analyze for the rest of the semester

Sampling Procedure (Day 1):

1. We will generally follow the procedure laid out in Laboratory Module 6—the Ubiquity of Micro-Organisms. Laboratory Modules 2-3 serve as background on culture media, although in this class we will not ever have to prepare our own media (thankfully, the lab techs do that for us all semester long and deserve all the praise we can heap on them!!).
2. Before beginning this exercise, be sure you understand the concepts behind sterile technique (Read Laboratory Module 7 on “Aseptic Transfer” for some background on this). Use the concept of sterile technique to guide a logical approach to sampling and maintaining your sample free from contamination
3. Each student will sample from two environments. Try to sample from one environment that you believe will have a high diversity of micro-organisms and one environment where you believe microbes will be absent.
4. Each table group should get a soil sample.
5. Leave your microbes to incubate (at 22 degrees or 36 degrees—why?)

Observations, Analysis, Choosing your Environmental Isolate for the rest of the semester (Day 2)

1. Draw and describe the colonies of bacteria that have grown up in each of your environmental samples. Use Laboratory Module 13 on “Cultural Characteristics of Bacteria” to help with this. Be sure to describe colony size, shape, color, etc.
2. Gather together with your table-mates as a group to choose your own environmental isolate to analyze over the rest of the semester. Keep the following in mind:
1. It is best to choose a clearly isolated single colony that you can easily remove from the plate with a wire loop.
2. Try to have each person at the table choose a colony with different characteristics.

3. Circle and label the colony you will use for the rest of the semester. Please store the plates with these colonies with easy access in the refrigerator, clearly labeled in a plate-holder for your table. The other plates can be stored apart at the back of the refrigerator.
4. Next week we will learn how to transfer this colony, streak it out for isolation, and keep a stock culture going all semester long. Learn to love this microbe because it will be your constant companion for most of the laboratory exercise we will do for the rest of the semester.
5. The hope is that by the end of the semester, we might have some idea as to what kind of bacteria you isolated from the environment, if not a good guess at a Genus or species!!