Bacteria - A Survey
Laboratory Investigation

  • to gain an appreciation of the diversity of organisms that are called bacteria
  • to note some similarities and differences between the Eubacteria and the Archaebacteria
  • to learn the various characteristics of the fungal groups
  • to recognize the role fungi play in our global and local lives
  • to sample various areas of your environment to determine the types of organisms present
  • Introduction

    Part I
    Organisms today are classified into three Domains. Two of these Domains are prokaryotic: the Archae and the Bacteria (sometimes called the Eubacteria). Organisms in the Archae Domain appear like bacteria but have a very different biochemical, and thus genetic, makeup. The Archae live in extreme anaerobic environments and have been called the Extremophiles. Some of the major categories the Archae have been divided into are the heat-loving Thermophiles, the salt-loving Halophiles, the acid-loving Acidophiles and the methane-producing Methanogens. The following link will provide general information and graphics for the Archae.

    Eubacteria consist of the bacteria and cyanobacteria. The typical prokaryotic organization lacks membrane-limited organelles such as nucleus, mitochondria, and lysosomes. They have a cell wall of peptidoglycan, a unique amino acid and simple sugar combination. Reproduction is simple splitting or binary fission and may occur, in some species, within 12-15 minutes under optimum conditions.

    Bacterial shape, while genetically determined, is influenced by environmental factors. Shape is round or coccal shape, rod-shaped or bacillus shape or spiral or spirillum shaped. A variety of views are available in the links below. The following link will provide general Information and graphics for the Eubacteria. Use the links below to get a closer view of the organisms.

    The cyanobacteria, originally called the blue-green algae, are photosynthetic prokaryotes. Their cells are generally larger than the bacteria and are covered or surrounded by a gelatinous covering or sheath. Cyanobacteria come in all the colors of the rainbow and some contain a swollen or enlarged region of specialized cells called a Heterocyst. The heterocyst contains the enzymes necessary to carry out the process of nitrogen fixation where atmospheric N2 is converted into other forms usable by plants.

    Use the links below to get a closer view of the organisms.

    In the absence of microscopes and slides, use the embedded links below to learn about the various organisms.

    See also pages 25-28 in A Photographic Atlas for the Biology Laboratory, 4th Edition.


    Bacillus subtilis
    Staphylococcus aureusRhodospirillum rubrum
    Clostridium botulinum
    note endospores
    Bacillus anthracisStreptococcus pyogenes
    pus former
    Helicobacter - ulcer organismCapsule
    Pseudomonas aeruginosaClusters of CocciBorrelia - cause of
    Lyme Disease
    All three types
    Escherichia coliStreptococcus - SEM imageVibrio choleraecheeky bacteria


    Gleocapsa and
    two algae
    Gleocapsa & friendsAnabaenaNostocOscillatoria
    GleocapsaAnabaenaNostoc at 400xOscillatoria
    Green fried eggsNote HeterocystA different viewSegmented green "worms"

    Part II Sampling Your Environment
    The purpose of this section is to sample your environment for various microorganisms. Almost anywhere you go at home, at work, or at school, you will find microorganisms.

    If you have access to a school lab and can procure petri dishes with nutrient or tryptic soy agar then please use one of them. If you would like to try being a microbiologist (and cook) at home then follow the instructions below.

    Making a Microbiological Medium (used by permission of the developer, Pamela P. Tabery with modification by dse)

    You can use a disposable foil muffin tin or the bottom one inch of a 24 oz. water bottle as your petri dish. Either can be covered with aluminum foil to prevent contamination and moisture loss. A very simple medium could be made from unflavored Knox gelatin all by itself but it contains only protein and would not support the growth of many organisms.

    This will make enough for one culture. Adjust the size of the recipe by multiplying each ingredient and the water by the number of dishes you are attempting to fill. Pour the following into a container and mix: 1 teaspoon (Knox) unflavored gelatin, 1/2 teaspoon sugar, and 1/2 teaspoon instant beef-flavored bouillon. Pour 1/4 cup boiling water into the bowl and mix. Pour this mixture into your muffin tin or substitute petri dish. It should solidify at room temperature. If the solution does not seem to be solidifying in a reasonable time, then add more gelatin next time.

    Use a cotton Q-tip as your swab. You could sample the microbes on your skin also by swabbing the skin surface or by placing your finger directly on the surface of the medium. Only your imagination limits the types of sampling you could do. Cover the dishes after you have gently swabbed the surface. Swab a dish without a sample on the Q-tip to serve as a control and see what is on the Q-tip. Dispose of the plates by adding a little bleach or Lysol type product to the surface and placing everything in a plastic bag.

    Compare the types of organisms you find with the areas you sampled.

    Additional Resources

    Cyanobacteria Gallery of Pictures