LEARN NC

CareerStart lessons: Grade eight

5.5 Microbiology: Bacteria in our environment

By Tammy Johnson and Martha Tedrow

Provided by CareerStart

Essential question: What are the physical and functional characteristics of bacteria?

Learning outcomes

Students will gain an understanding of microbiology and how bacterial colonies grow.

Teacher planning

Materials needed

  • 15 small clear plastic eggs or gelatin capsules (which can be purchased from any health food store.)
  • String
  • Student handouts:
    • Bacteria information sheet (may also be copied as a transparency)
    • Microbiology lab handout
    • “Diseases: Who Can Help?” handout
  • Lab materials:
    • Petri dishes
    • Agar
    • Inoculating loops (or sterile cotton swabs)
    • Microwave
    • Cardboard box
    • Sponge
    • Bowl with 20 mL of water
    • Safety goggles
    • Thermometer

Time required for lesson

One class period (55 minutes), plus follow-up days to watch incubation of bacterial colonies.

Pre-activities

Prior to the experiment, the petri dishes and incubation box must be prepared.

  1. Prepare agar and pour into petri dishes.
  2. Tape the dishes shut and let them cool upside down on the shelf overnight.
  3. Construct incubation box: Place a sponge into a dish with 20 mL of water inside the cardboard box. The inoculated petri dishes will be placed upside down inside of the box to provide a favorable environment for bacteria growth. Put the box on top of a refrigerator. The compressor inside of the refrigerator will help to maintain constant humidity. Check temperature inside of box periodically with a thermometer. Maintain 23 degrees Celsius to keep agar from drying out.

Activities

  1. Introduction: Distribute (or project) and read the bacteria information sheet.
  2. Compare and contrast eukaryote and prokaryote cells using a Venn diagram on the board. For comparisons between the two, see the following:
  3. Making a bacterial cell: Have the students wind string to represent chromosomal material and put the string inside of a small plastic egg or gelatin capsule to model the bacterial cell.
  4. Discuss the structure and function of a bacterial cell (prokaryotic cell).
  5. Discuss health care careers and the struggle with the pathogens caused by bacterial infections. (See “Career Information” below.)
  6. Student investigation: Have students complete the bacterial growth lab. (See instructions below and on the student handout.)
  7. Follow-up: Have students complete the worksheet “Diseases: Who Can Help?”

Student lab instructions

Note: Student lab instructions are also on the lab handout.

  1. Pick up your petri dish and open the top carefully. (Do not touch the inside.)
  2. Move to your selected location in the school (or classroom).
  3. Using the inoculating loop (or cotton swab), swab the area that you will be testing and in a Z pattern spread the specimen over the surface of the nutrient agar in the dish. (Be careful not to dig into the agar!)
  4. Tape the top back to the bottom and flip it over.
  5. Label the bottom of the container with:
    • Your name and partner’s name
    • Period #
    • Location of specimen
  6. Place the petri dishes upside-down in the incubation box.
  7. Make sure the sponge is sitting in water and that it is inside of the box to keep the air humid.
  8. Place the box back on top of the counter.
  9. Check the temperature of the box to make sure it remains at 23 degrees Celsius. (This ensures that the agar will not dry out during the culturing process.)
  10. Close the box and the teacher will place the box on top of a refrigerator. (The compressor produces a constant warm temperature and the height ensures the cultures will not be disturbed.)
  11. Remove the box after 24, 48, 72 hours and 1 week. Record colony growth.(Count using significant colony growth.)

Career information

Career information comes from the Bureau of Labor Statistics’ Occupational Outlook Handbook.

Medical scientists
Research human diseases to improve human health. Most medical scientists conduct biomedical research and development to advance knowledge of life processes and living organisms, including viruses, bacteria, and other infectious agents. Past research has resulted in advances in diagnosis, treatment, and prevention of many diseases. Basic medical research continues to build the foundation for new vaccines, drugs, and treatment procedures. Medical scientists engage in laboratory research, clinical investigation, technical writing, drug application review, and related activities.
Epidemiologists
Investigate and describe the causes and spread of disease and develops the means for prevention or control. Epidemiologists may study many different illnesses, often focusing on major infectious diseases such as influenza or cholera.
Physicians and surgeons
Diagnose illnesses and prescribe and administer treatment for people suffering from injury or disease. Physicians examine patients, obtain medical histories, and order, perform, and interpret diagnostic tests. They counsel patients on diet, hygiene, and preventive health care.
Registered nurses
Treat patients, educate patients and the public about various medical conditions, and provide advice and emotional support to patients’ family members. RNs record patients’ medical histories and symptoms, help perform diagnostic tests and analyze results, operate medical machinery, administer treatment and medications, and help with patient follow-up and rehabilitation.
Pharmacists
Distribute prescription drugs to people. They also advise their patients, as well as physicians and other health practitioners, on the selection, dosages, interactions, and side effects of medications. Pharmacists monitor the health and progress of patients to ensure the safe and effective use of medication.
Pharmacy technicians
Help licensed pharmacists provide medication and other health care products to patients. Technicians usually perform routine tasks to help prepare prescribed medication, such as counting tablets and labeling bottles. They also perform administrative duties, such as answering phones, stocking shelves, and operating cash registers.

North Carolina Curriculum Alignment

Science (2005)

Grade 8

  • Goal 7: The learner will conduct investigations, use models, simulations, and appropriate technologies and information systems to build an understanding of microbiology.
    • Objective 7.02: Describe diseases caused by microscopic biological hazards including:
      • Viruses.
      • Bacteria.
      • Parasites.
      • Contagions.
      • Mutagens.