Bacterial Soft Rot
The purpose of this project is to understand how bacteria use enzymes to affect a host, as well as to understand how temperature effects these enzymes. One may predict that bacteria will utilize many enzymes to break down high energy molecules and these enzymes will be negatively affected by temperatures outside their optimal range.
To perform this experiment you will need: potato (or carrot, or onion), knife, Erwinia carotovora ( a bacteria you get find if cut vegetables are left on the counter for a week or two), TSA plates, plastic bags, transfer loop (a tooth pick will suffice), bunsen burner (only if loop is being used), filter paper disks, petri dishes, and saran wrap.
Procedure (Day 1):
1. Wash the vegetables
2. Cut each vegetable into 1/4 inch slices
3. Put two sterile filter paper disks into a petri disk
4. Pour water into petri dish (about 1/8th in.)
5. Add 2 or 3 vegetable slices into petri disk
6. Put small cut in center of each slice (except 1 which will be the control)
7. Inoculate with Erwinia carotovora
8. Wrap plate in Saran wrap
9. Do this three more times for the same vegetable; incubate 1 plate in refrigerator, 1 at room temperature, 1 at 45 degrees C, and 1 at 26 degrees C.
Procedure (Day 2-5)
1. Check enzyme activity of each sample by running transfer loop over slice to detect maceration
2. Note the odor!
3. On day 5, try to isolate some of the Erwinia carotovora
Plate the bacteria on TSA plate (let's see is any contamination occured)
At the end of day 5, the vegetable slices should have become soft and rot should be evident. Erwinia carotovora should have been isolated from the sample, according to Koch's postulates. It should also become clear that vegetables will rot faster at higher temperatures, therefore it can be deduced that the ideal temperature for the enzymes of Ervinia carotovora is around 45 degrees C.