Culturing Bacteria
Activity #1

Bacterial Enrichment Using a Carrot Medium Be sure to read the General Safety Guidelines and the Microbiology Safety Guidelines before beginning this lab activity. Materials and Apparatus Carrots that have been cleaned, cut in half, then cut into pieces 5-8 cm in length Beaker Forceps Isopropyl alcohol Petri dish Filter paper Microscope Microscope slides Transfer needle or loop Test tube Test tube rack

Culturing Bacteria Menu Introduction Activity #1: Bacterial Enrichment Using a Carrot Medium Activity #2: Enrichment of Microbes Using a Milk Medium Appendix General Safety Guidelines Microbiology Safety Guidelines

Procedure

1. Obtain several carrots that have been cleaned, cut in half, then cut into pieces 5-8 cm in length.

2. Immerse the carrot pieces in a beaker of water and boil for 15 minutes.

3. Remove 2 carrot pieces with sterile forceps (the forceps are sterilized by dipping them in isopropyl alcohol, then burning off the alcohol). Place the carrot pieces in a petri dish that has a piece of wet filter paper, all of which has been previously sterilized.

4. Incubate at room temperature and observe after a few days.

5. To observe live microbes on the carrot, place a drop of water in the center of a clean slide.

6. Sterilize a transfer needle or loop by first placing the transfer device in a flame. Cool it by touching it against the wet filter paper in the petri dish that contains your carrot enrichment cultures.

7. Touch a growth area of the carrot with the sterile transfer needle and then mix the material in the water drop on the glass slide. DO NOT USE THE NEEDLE TO DIG OUT A SECTION OF THE GROWTH REGION—you will have too much material to see under the microscope! Less is more!

8. Flame the needle and replace it in its holder (a test tube in a rack).

9. Place a coverslip over the water drop and observe under high power of the microscope.

10. Record the appearance of the growth sample, making note of shape, color, size, and motility.