Introduction to Microbiology

Where do Microorganisms come from? EVERYWHERE!!!! They are all around us, in this lab we will examine various microorganisms in the environment around us.

Part I-Test Tube Obtain a test tube Fill 1/4 full with soil Add water to test tube until it is about 1/3 full. Cap test tube and shake. Place your names on the label.

Part I- Petri Dish Obtain a petri dish and place your names on the label. Pour a layer of hot, melted agar into the petri dish. Fill your petri dish about 1/4th full. Recover your petri dish. Allow the agar to harden for about 5 minutes.

Locate a sterile transfer loop. Place the plate in front of you. Dip the loop end of the transfer loop into the soil water and transfer the soil water to the agar plate. Gently rub the surface of the agar with loop. Don’t push too hard. Transfer two more loopsful of soil water in the same manner. Observe your plate and make a drawing of what you see.

Part II- Fungi Obtain another petri plate, and put a label with your names. Add a thin layer of tomato soup to the bottom of the plate. Grind up a small sample of dirt in your fingers. Sprinkle a few specks of dirt on the soup and cover the plate. Observe your plate and make a drawing of what you see.

Part III- Yeast test tube Obtain a culture tube, and label with your names. Add yeast growth medium to the tube until it is 2/3 full. Locate the packet of dry yeast. Add one of the small particles of yeast to the tube. Shake the tube with the top on until you can’t see the particles of yeast any longer.

Part III- Yeast Slide Obtain a sterile loop. Dip the end of the loop into the yeast liquid in the tube. Transfer a small amount of liquid onto a clean glass slide. Repeat this 4 more times so you have a drop of the yeast growth medium on the slide. Add a cover slip and observe the yeast under high power on a microscope. Count the number of cells you see in the field.

Part IV- Algae and Protozoa Locate the large plastic bottle filled with pond water. Obtain a clear glass slide and a cover slip. Place a drop of pond water on the slide using a pipette. Place cover slip on slide. Observe under low and medium power. Make drawings.

Part V- Soil Culture Obtain your original tube containing the soil and water after about 4 days. Obtain a clear glass slide, a cover slip, and the bottle of methylene blue stain. Transfer a drop of soil water to the slide. Spread the water around on the slide. After the water has dried, add a drop of the methylene blue stain, and let it dry for 1 minute on the slide. Carefully blot the slide dry with a paper towel. Observe the slide under high and low power. Make drawings of what you see.