Experimenting with Bacteria
Integrated Science 2
Name
Per:
 Introduction
Bacteria are prokaryotic organisms that play important roles in the living world. Some bacteria are harmful pathogens that cause
disease in humans, while others are helpful organisms that provide benefits for both humans and the environment. In this activity
you will design and conduct an experiment using bacteria and then write a formal Laboratory Report describing the experiment.
 Procedures
DAY 1 (Monday): Sampling and Spreading Bacteria/ Designing your Bacterial Growth Experiment
Tasks: 1. Remembering that bacteria needs food, acidity, temperature, time, oxygen, and moisture to live. Design an
experiment that tests how bacteria respond to different conditions (think! You can experiment on what would make
bacteria grow best or what would best kill bacteria…this is YOUR experiment!). Obtain teacher approval for your IV
and DVs before you move forward.
2. Collect and spread bacteria according your experiment’s needs (three dishes per group). Incubate overnight at 37℃.
3. Begin your Introduction. It should relate to both your group’s IV and your DV. Use your Pathogens RQs and
additional sources to create a well-researched Introduction. (use a minimum of 3 sources and use at least 5 citations)
Items Due on Day 2: rough draft design outline. (It’s recommended that you start your Introduction…it is due Day 3)
DAY 2 (Tuesday): Observing Growth/Conducting Experiment
Tasks: 1. Observe the bacterial growth on your Petri dishes.
2. Create a Laboratory Notebook Entry on a separate sheet of paper using the format below.
“Observations” should include color, texture, shape, and thickness of the bacterial colonies.
3. Carry out specific procedures related to your group’s chosen IV.
4. Begin Procedures/Materials for your chosen experiment
5. Assign one member of your group to come in and take photos of your dishes on your off-Block Day.
Title of Laboratory Experiment: Experimenting with Bacteria– (state daily activity here)
Date: What is today’s date?
Time: What time of day did you complete this portion of the experiment?
Environmental Conditions: What is the temperature? Are you inside or outside? Is it sunny? windy? etc.
Task(s): What did you, the experimenter, do today in reference to this experiment?
Observations: What did you, the experimenter, observe today in this experiment? Use descriptive words and drawings.
Items Due on Day 3: Laboratory notebook entry, “A”, “B”, and “C” from Laboratory Report Format (typed)
DAY 3 (Wednesday/Thursday): Observing Bacterial Growth/Death
Task:
1. Create a Laboratory Notebook Entry (one entry for 1 st and 3rd periods, two entries for 2nd period)
2. Create data tables to use to record your final results
Items Due on Day 4: Laboratory Notebook Entry, “D” from Laboratory Report Format (typed), blank data tables (hand-drawn
with a ruler or done on a computer)
DAY 4: Observe bacterial growth and record results.
Tasks: 1. Record final data about your Petri dishes on the Data tables you constructed. Data should also include drawings that
illustrate the correct size and position of the colonies as you observed them on the Petri dish.
2. Create a Laboratory Notebook Entry (one entry for 2nd period, two entries for 1st and 3rd periods).
3. Continue work on all remaining portions of Formal Lab Report
Final Draft Lab Report Due Tuesday, May 6
Experimenting with Bacteria
 Petri dish guidelines
1. Preparing the Petri Dish
NEVER OPEN A STERILE PETRI DISH UNLESS ABSOLUTLEY NECESSARY (AS IN PART OF AN EXPERIMENTAL
PROTOCOL) – OTHERWISE STERILITY MAY BE COMPROMISED
2. Inoculating the Petri Dish
Agar (food for bacteria) was poured and hardened to cover the entire bottom of the petri dish. Using a sharpie,
carefully divide the outside of the bottom of a closed petri dish into four sections and number them one through four,
as shown on the right. Do this for all 3 of your petri dishes (with these 4 sections, each level of your experiment can
have 4 trials). Label the side of your dishes with your first names and class period to keep a clear view of the agar.
Keep lid on dish whenever possible to avoid contamination.
3. Incubation
• Place the dish upside down (to avoid water accumulation on the agar) in an area designated by
1 2
3 4
your experiment. The dish is incubated upside down so that any liquid/toxins that collects will drip
down onto the cover and not collect on the surface of the agar.
 Design Outline
Title:
Hypothesis:
Independent Variable:
 Continuous or  Discontinuous
Levels of the I.V.
(indicate control)
# of trials you will
conduct for each level
Dependent Variables
Quantitative Measurements (include units):
Qualitative Measurements:
Constants:
2
Experimenting with Bacteria