Abstract

Objective

The goal of the proposed project is to determine the microbial diversity present in one's immediate environment. Of the 100 million or so bacteria that are proposed to exist, how many distinct species can one identify? How can these different species be identified: By size, shape color, growth rate?

Introduction

Microorganisms are the most fundamental, diverse, and prevalent biological organisms that inhabit the earth today. Prokaryotic microorganisms, organisms without a nucleus, can be generally divided into three classes: bacteria, protozoa, and fungi. By far the most predominant of these three classes of organisms would include bacteria, single celled organisms which inhabit every type of environment on earth, and which have been in existence for greater than 3.5 billion years. Bacteria are ubiquitous, and are found in almost any environment. They thrive in the hot environments of deep sea sulfur vents, the frozen tundra of the Antarctic, the saline environments of the Dead Sea, and extremely acidic environments such as the stomachs of organisms.

Bacteria can be both pathogenic, responsible for a variety of diseases, and non-pathogenic, or harmless. Pathogenic bacteria are responsible for the outbreaks of cholera, tuberculosis, and gonorrhea, whereas non-pathogenic bacteria have many roles, which include the symbiotic residence in the stomachs and intestines of humans, the break down indigestible foods, and in return, producing necessary nutrients, such as Vitamin K. Moreover, a variety of naturally occurring antibiotics are synthesized from bacteria, such as streptomycin.

The non-pathogenic and ubiquitous E. coli bacterial strain, isolated from the guts of humans, is the most commonly grown laboratory organism. E. coli is used to produce drugs, such as insulin and human growth hormone, and is a commonly used organism in almost all biotechnology laboratories, producing a variety of reagents used by the typical scientific researcher.

Terms, Concepts, and Questions to Start Background Research

• Prokaryote vs. eukaryote
• Gram-negative vs. gram positive bacteria
• Pathogenic vs. non-pathogenic bacteria
• Bacterial motility
• Phototrophs vs. autotrophs vs. chemotrophs vs. heterotrophs
• Anaerobic vs. aerobic bacteria
• Symbiotic bacteria and their importance to higher organisms
• Bacteria, and E. coli, as scientific research tools

Bibliography

Virtual Museum of Bacteria

Introduction to Bacteria

A Compendium of Bacteria Links

Experimental Procedure

1. Obtain a pack of petri dishes (20 per pack) and fill half way with liquid LB agar. Let plates solidify.
2. Identify 9 different locations where you would like to assess biodiversity. Suggested sites could include the bathroom, kitchen, locations near heating vents, bedrooms, the refrigerator, the backyard, the garage, etc.
3. At each site, place 2 petri dishes per site. Leave dishes open and exposed for a period of 48 hours.
4. An additional two plates should be unopened and used as negative controls. In other words, you'll study what grows on these plates even though you never expose them to the air. (Hopefully, very little if anything will grow!)
5. At the end of 48 hours, seal plates with strapping or heavy duty scotch tape.
6. Allow the plates to incubate by placing all of them in one single location that has a fairly constant room temperature (about 22 degrees Celsius) for 1-3 weeks, until distinct bacterial colonies can be observed. (Don't forget to put the two, unopened control plates in this same location.)
7. Collect data over the course of the three weeks. Every other day, note the number of colonies, the color, the size.
8. After the end of the three week period, make various graphs of the data. Suggestions include, but are not limited to:
   1. Colony count on each plate.
   2. Colony count at each location (take an average of two plates).
   3. Different types of microorganisms, based upon:
      1. Size
      2. Color
      3. Shape
9. Keep the microbial plates during the duration of your project, and while you are writing up your paper. You will want to make many observations.
10. When you are completely done with the experimental write-up, decontaminate the plates by carefully opening, and pouring a generous amount of 10% bleach onto the agar surface. (You can make a 10% bleach solution by mixing one part of regular laundry bleach (e.g. Clorox) with 9 parts of water.)
11. The sterilized, decontaminated plates, can be disposed of in your regular household garbage, but ONLY after sterilization as described in the previous step.

Discussion Points to Consider When Writing up the Results

• Which environmental areas resulted in the most microbial growth?
  • What environmental features unique to those locations might facilitate microbial growth?
    • Moisture content?
    • Air circulation?
    • Cleanliness?
• Based upon your background reading, can you possibly identify any of the bacterial/microbial colonies based upon their morphological features?
  • Color?
  • Shape?
  • Size?
• If you had access to reagents in a common laboratory, how could you use more sophisticated methods to type, classify, and characterize the individual colonies?
• Based upon your background reading, what percentage of the microbial organisms that are present in your environment did you isolate and identify?

NOTE ON SAFETY

Bacteria are ubiquitous, and live within the human gut, and in every corner of our environment. We come in contact with bacteria on a daily basis. Handwashing is 99.9% effective at decontaminating ourselves from bacteria which may reside on the skin. Thus, when the proper safety precautions are taken, colonies of microorganisms can be safely isolated from homes, yards, gardens, etc. The majority of microorganisms are non-pathogenic, but bacterial cultures or petri plates containing any type of bacterial colonies should only be treated with general safety precautions. Household bleach at 10% strength, or general common household cleaning reagents (409, Fantastic, Lysol, etc.), are effective at decontaminating all bacteria, and should be used at the completion of the study. Keep in mind that this type of experiment is similar to the experiment that many of us performed in gradeschool, where different molds were cultured on moist pieces of bread!

Variations

• For more science project ideas in this area of science, see Microbiology Project Ideas.

Credits

Laurie Usinger, Bio-Rad Laboratories

Images from www.bio-rad.com

Last edit date: 2007-03-22 22:00:00