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



Students will measure and observe the growth of bacteria colonies in two different temperatures.



Students will be able to:


Vocabulary: Observation, inferences, hypothesis



  1. Bacterial agrose in petri dishes 1 per student
  2. Flat toothpicks (with dull end so agrose is not punctured) or Q-tips
  3. Trays
  4. Bleach cleaning spray and paper towels for thorough clean-up
  5. Parafilm (or as an alternative clear tape)
  6. Refrigerator (or two locations with >20 degree C temperature difference)



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.


  1. Divide students into pairs; each pair receives 2 petri dishes with bacterial agrose.
  2. Using Flat toothpicks, students decide one 1 location in the school/classroom to “swab” for bacteria onto both dishes. 
  3. Seal a clean Petri dish with agrose so students have a basis for comparison.
  4. 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.
  5. Close the Petri dishes, and seal the edges with parafilm or clear tape.
  6. 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.
  7. 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).
  8. 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.
  9. Allow the first 10 minutes of class for the next 4 days for observation.
  10. 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:

  1. How did the growth of the bacterial colonies in the two different temperature environments compare?
  2. What do you think would have happened to the colonies if you left them to grow for another week?
  3. 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