Antibiotics in Action

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    Biology Activity
    Name That Actinomycete
    Isolating Soil Organisms

    This lab could be used as a less involved activity than the lab exercise Medicine from Dirt: Isolating Actinomycetes that involves detecting the existence of antibiotic-producing actinomycetes in soil. The exercise illustrates the general procedures needed to isolate and test for potential antibiotic-producing soil organisms in the actinomycetes and fungal categories. The activity allows students to isolate soil organisms that have the ability to decompose polysaccharides such as cellulose and starch rather than producing an antibiotic. A simple chemical test is performed to detect this decomposition action by the soil microbe.
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      General Safety Guidelines
      Microbiology Safety Guidelines
      Major Concept
      Level and Expected Student Background
      Time
      Safety
      Materials and Apparatus
      Advance Preparation
      Relevant National Science
      Education Standards
      Relevant New Jersey State
      Science Education Standards

    Major Concept

    The specific chemical activity of certain soil organisms can be identified using some standard chemical tests.

    Level and Expected Student Background

    This activity can be done with all level of students who are familiar with basic lab equipment and have been instructed in sterile techniques for working with microorganisms.

    Time

    The setup for this lab can be done in one 45-minute class period if the starch agar plates are prepared in advance. A second class of 25 minutes will allow for observations and testing of the plates as well as clean up.

    Safety

    1. Wear safety goggles.

    2. Students should understand the basics of sterile techniques and working safely in a microbiology laboratory.

      General Safety Guidelines
      Microbiology Safety Guidelines

    Materials and Apparatus

    You will need the following for each team participating in the activity:

    • Balance with precision to 0.1 g
    • Source of soil samples (students bring to lab)
    • Sterile distilled water in sterile bottles with cap (capacity of 100 ml); could use small water bottles that have been sterilized using a 10% bleach solution, then rinsed once with isopropyl alcohol, allowed to dry in a low temperature oven with loose cotton plug. Cap after filling with sterilized water (sterilize cap in advance using the bottle sterilizing technique).
    • Starch agar (see recipe and procedure in the student version) on sterile petri dishes (2 minimum) plus lids.
    • Sterile pipettes (number depends on the number of soils to be tested); 1 ml capacity with 0.1 ml increments
    • Transfer bulb
    • Glass loop spreader
    • 95% ethanol
    • Bunsen burner or alcohol lamp
    • Gram's iodine stain (see recipe in the student version)

    Advance Preparation

    The following should be prepared ahead of time for the students:

    1. Starch agar plates

    2. Bottles of sterile distilled water

    3. Glass loop spreaders, if not purchased, made from either glass tubing (sealed) or glass rod, bent in the form of a V with a handle coming off one of the “arms” of the V in the same plane.

    4. Gram's stain

    Relevant National Science Education Standards

      Unifying Concepts and Processes — The activity is concerned with evidence, models, and explanations and also with change, constancy, and measurement.

      Science as Inquiry — The activity is concerned with the abilities necessary to do scientific inquiry and is also concerned with understandings about scientific inquiry.

      Physical Science — The activity is concerned with chemical reactions.

      Life Science — The activity is concerned with the behavior of organisms and is also concerned with matter, energy, and organization of living systems.

      Science and Technology — The activity is concerned with the science behind the technology of obtaining drugs from soil organisms.

      History and Nature of Science — The activity demonstrates the nature of scientific knowledge.

    Relevant New Jersey State Science Education Standards

      5.1 The activity involves conducting systematic observations, interpreting and analyzing data, drawing conclusions, and communicating results.
      5.4 The activity deals with the science behind the technology of obtaining drugs from soil organisms.
      5.5 The activity requires basic understanding of the basic characteristics of living organisms.
      5.6 The activity investigates the behavior of matter in biological systems.

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    References

    1. Conant, J.B., ed. Harvard Case Histories in Experimental Science. Cambridge, MA: Harvard University Press, 1957.

    2. Gabriel, M.L. and Fogel S., eds. Great Experiments in Biology. Englewood Cliffs, NJ: Prentice-Hall, 1955, pp. 105-118.

    3. Brock, T.D., ed. Milestones in Microbiology. Englewood Cliffs, NJ: Prentice-Hall, 1961.

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