Grow Bacteria, Grow!
Lauren Mangione
MS 282 Park
Slope Middle School, Brooklyn
Summer Research
Program for Science Teachers
August 2011
Subject:
General Science
Grade Level:
6 - 8
Unit 3:
Diversity of Life
Time Required:
1 - 50 minute class, 10 minutes at
the beginning of each class for 4 days
Purpose:
Students will measure and
observe the growth of bacteria colonies in two different temperatures.
Objectives:
Students will be able to:
-
Identify bacterial colonies on Petri
dishes
-
Graph bacterial growth through
daily observation
-
Predict the continued growth
of bacterial colonies given different parameters
Vocabulary:
Observation, inferences, hypothesis
Materials:
-
Bacterial
agrose in petri dishes 1 per student
-
Flat toothpicks (with
dull end so agrose is not punctured) or Q-tips
-
Trays
-
Bleach cleaning spray and paper towels for thorough clean-up
-
Parafilm (or as an alternative clear tape)
-
Refrigerator (or two locations with >20 degree C
temperature difference)
Introduction:
By growing bacterial colonies in two
different temperature environments, students will see the effect of temperature
on growth, and can begin to form their own ideas about what environments may or
may not aid bacterial growth.
Procedure:
- Divide students
into pairs; each pair receives 2 petri dishes with bacterial agrose.
- Using
Flat toothpicks,
students decide one 1 location in the school/classroom to “swab” for
bacteria onto both dishes.
- Seal
a clean Petri dish
with agrose so students have a basis for comparison.
- With
soft “S” shaped
motions, students drag their swab onto both Petri dishes. Make sure students
have taken 4 or 5 swabs from their location.
- Close
the Petri dishes, and
seal the edges with parafilm or clear tape.
- Clearly
label the petri dish
with the students initials, date and swab location (eg “doorknob”). Make
sure to label along the edge of the petri dish and not the center, so the
colonies can be clearly counted and are not obscured by the writing.
- Take
pictures of the petri
dishes or have students make drawings in their science notebooks of their
bacterial colonies (Day 1 will have no growth).
- Place
one of the petri
dishes in a warm location (windowsill) and the other in a refrigerator, or
in an area that stays relatively cool.
- Allow
the first 10 minutes
of class for the next 4 days for observation.
- Students
graph results on a
two-coordinate line graph, where “day” is on the x axis and “number of
colonies” is the category on the y axis.
Extension Questions:
- How
did the growth of the
bacterial colonies in the two different temperature environments compare?
What do you think would have happened to
the colonies if you left them to grow for another week?
What
other variables might
you test to aid or inhibit the growth of bacterial colonies?
New York City Science Standards:
Living Environment 1.1a-c