Part 4: Coliform Bacteria

Note: This test requires 48 hours of incubation time.

1. Put on a new pair of gloves.
2. Disinfect your gloves by pouring some isopropyl alcohol in the palm of one gloved hand before rubbing the gloves together to cover all surfaces of the gloves with alcohol.
3. Wipe down the surface you are working on with alcohol and a paper towel.
4. Rinse each 2 cc snap top vial and the DW pipet with alcohol.
5. Allow the vials and pipet to dry on the disinfected work surface before closing the tops on the vials.
6. Unwrap the coliform bacteria test kit tube and label it “Water body.”
7. Label one snap top vial “Bottled water” and the other “Tap water.”
8. Use the DW pipet to add 3 mL of distilled water to the Water body test tube.
9. Replace the lid on the tube and shake until the powdered media dissolves.
10. Use the DW pipet to transfer 1 mL of the dissolved media to each of the snap top vials.

Note: The Water body test tube, Bottled water snap top vial, and Tap water snap top vial should each have approximately 1 mL dissolved media solution.

1. Use the Water body pipet to add approximately 1 mL of the water body sample to the Water body media test tube and close the lid.
2. Repeat Step 49 for the tap water and bottled water samples using the appropriately labeled pipets and snap top vials.
3. Store the coliform test containers upright for 48 hours in a warm (70–90°F), undisturbed area without light.
4. After 48 hours, take a photo of the three coliform test containers on a sheet of paper displaying your name and date.
5. Upload the image into Photo 4.
6. Observe the color of the liquid in each container, without opening it, and record along with the interpretation in Data Table 2.
   1. PURPLE COLOR: Negative result (No coliform bacteria were detected).
   2. YELLOW COLOR: Positive Result (Coliform bacteria are present).