Drexel-SDP GK-12 ACTIVITY
Bacteria Growth
Subject Area(s)
Biology, Life Science
Associated Unit
Associated Lesson
Activity Title Bacteria Growth
Grade Level 7 (7-9)
Time Required 2 days minimum
Group Size variable, dependent upon the number of Petri dishes available
Expendable Cost per Group US$ 2
Summary
This activity is designed to reinforce the concept of the presence of bacteria and other
microorganism despite their small size. Students collect and culture bacteria in Petri dishes. The
dishes are incubated and then observed under a microscope.
Engineering Connection
Environmental engineers use science and engineering to study and improve the environment.
They investigate air, water, and land to ensure they remain pollution free and conduct studies to
detect the presence or absence of microorganisms or pollutants. Many of the substances they test
for are invisible to the naked eye. In these instances environmental engineers employ techniques
such as culturing samples to determine the presence of pollutants. In this activity students collect
samples from their environment and grow them to determine if bacteria is present.
Keywords
Bacteria, Cells
PA Educational Standards
• Science:
o 3.2.7 Inquiry and Design
o 3.3.7 Biological Sciences
Pre-Requisite Knowledge
Students should be familiar with basic structure of cells.
Learning Objectives
After this activity, students should be able to:
• Understand how to use microscopes to view small objects
•
Understand that organisms are around them even though they are invisible to the naked eye.
Materials List
Each group needs:
• 1 microscope
• Petri Dish with agar
• 4 Sterile swaps
Each student needs:
• Dust mask
• Sterile gloves
To share with the entire class
• Sterile water
Introduction / Motivation
Environmental engineers search for microorganisms or other pollutants as part of their job. Often
they can’t see the microorganisms with their naked eyes because they are too small. When this is
the case they collect samples and “grow” them in labs so they are more easily seen. This
“growing” process is known as incubation. To determine if microorganisms are present in an
environment, such as water, the engineer will rub the agar in a Petri dish with a swap that has
been dipped in the water. The dish is then placed in a warm incubator for several hours to give
the organisms a chance to grow. If they are present they will feed on the agar and grow. When
the dish comes out of the incubator the engineer will be able to see with the naked eye if the
organisms have grown.
Vocabulary / Definitions
Word
Definition
Bacteria
Single celled microorganisms
Cell
The basic structural and functional unit of all organisms
Microscope An instrument for view objects that are too small to be seen by the naked eye
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Procedure
1) Determine where to collect the samples. Have students wear sterile gloves to prevent
contamination of the Petri due to handling.
2) If the location is dry, such as a wall or floor, wet a sterile swap with sterile water. Rub the
moistened swap on 1 quadrant of the Petri dish. Repeat with a new moistened swap for each of
the remaining 3 quadrants.
3) Close the Petri dish and mark the location and date on the outside of the lid.
4) Place the dishes in an incubator for a minimum of 1 day.
5) After 24 hours examine the dishes to see if there is bacteria growth. If there is no growth
leave the dishes in the incubator for additional time. If there is growth, remove the dishes from
the incubator.
6) Prior to handling the cultured dishes have students put on sterile gloves and facemasks.
7) Ask students to write down their observations, color, smell, size, etc., of the cultured dish.
8) Place dish under microscope and view bacteria up close.
9) Ask students to draw what they see under the microscope.
Assessment
Post-Activity Assessment
• Discuss their observations of the bacteria.
• Discuss whether or not there was a lot of bacteria present depending upon their sample
location. Some area’s may contain less bacteria than students had predicted.
Owner
Drexel University GK-12 Program
Contributors
Quincy Brown, Computer Science Department, Drexel University
Copyright
Copyright 2009 Drexel University GK12 Program. Reproduction permission is granted for nonprofit educational use
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Bacteria Growth Worksheet
Name______________________________________________________________________
Date________________________________________________________________________
Question: Are bacteria all around us even if we can’t see them with our naked eyes?
Hypothesis:
Observation 1 – Drawing of Petri Dish
Observation 2 – Drawing of bacteria under the microscope
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