Bacterial Hand Lab

Introduction: Bacteria belong to the Kingdom Monera. They are the smallest independently living cells, with most ranging from 0.25 to 3.0 (m in diameter and 1 to 20 (m in length. There are thousands of different species but three general shapes: spherical (coccus), rod-shaped or cylindrical (bacillus), and curved or helical (spirilla).

Purpose: To find out how bacteria spreads on a human beings hand.

Hypothesis: If a person rolls their finger on agar that is a Petri plate, then we can find out how bacteria spreads on a humans hand, because we will physically be able to see the bacteria spread.

Materials:

Petri plate
Sterile nutrient agar
Permanent marker
Human digit
Soap
Water

Procedures:

1) Gather materials listed above in the materials section and return to your lab station. 2) Determine the top and bottom of the Petri plate. The top piece sits on the bottom that contains the nutrient agar. 3) Label your name, period number, and team on the edge of the Petri plate on the bottom without opening the container (there is bacteria in the air). 4) Turn the Petri plate upside down. Draw a vertical line through the center of the plate and then a horizontal line through the center. The result will be four equal quadrants. Label the quadrants on the side one through four. 5) Wash your hands for three minutes using soap and water. 6) The independent variable is the digit each time it is washed and rolled onto the agar. 7) Begin with quadrant number one. Roll an identified digit in area number one. Be gentle, the agar is like Jell-O. 8) Wash your hands for one minute and roll the same digit in area two. 9) Wash your hands for one minute and roll the same digit in area three. 10) Wash your hands for one minute and roll the same digit in area four. 11) Set your Petri plate in the area described by the faculty. 12) Clean your lab station, wipe off counters, and return materials. 13) Check your results as requested by faculty. 14) The dependent variable is the number, type, and color of bacterial colonies that grow on the agar in each area. 15) Draw pictures and write narratives of your observations. 16) Respond to the analysis questions and complete a conclusion. 17) Prepare yourself to readily explain your results to others.

Analysis:

1. Explain the concentrations of bacteria colonies observed on the Petri plate that you prepared based on each quadrant. (Yes, count and describe them!)

2. What color colonies grew in each quadrant?

In quadrant one the bacteria was yellow. In quadrant two the bacteria was like a darker yellowish type color. In quadrant three the bacteria was white, not like a bright white but like a dull white. In quadrant four the bacteria was a reddish burgundy color.

3. Develop a possible explanation for the growth of bacteria in quadrant four.

The growth in quadrant four was kind of weird. It grew pretty rapidly but had a reddish color like it started yellow then turned red.

4. Based on this experiment, does soap reduce bacterial concentration?

No, soap does not reduce bacterial contraction because the bacteria will always spread. It may kill some of the bacteria but the bacteria will always come back. A bacterium reproduces every 20 minutes.

5. Prepare a mathematical model that represents the rate of growth for the Petri plate that you prepared. Use evidence from this lab to support your model and explain your reasoning.

2(pi) (0.25mm) = 400 bacteria 1.57mm area 125.7 (50.9) x 400 =20,380 80mm 80 32,000 bacteria 1.57 2pi (20mm) 6. Describe the Petri plates of each member of your lab team. Discuss all observed similarities or