Once you have decided on a specific problem to study, it is very important to design your approach carefully and well. The success of a project is dependent upon the proper design and execution of that design. A number of factors may need to be considered at this point. Some that come to mind are:

1. Don’t try to skimp by doing the very minimum that will give you some answers to your problem. Generally it is an excellent idea to have one or more replications of each test that you run. For example, if you are testing the effects of different mouthwashes on a particular species of bacteria, it is well to do at least two identical tests for each different mouthwash so that you can demonstrate that your procedure and technique was acceptable (the results of each of the identical tests should be virtually the same). You should also run a control where everything is the same except that no mouthwash is present so that you prove any effects are due to the mouthwash and not from other unknown factors.

2. Most people are familiar with the use of pre-poured solid agar petri plates for growing microorganisms, but this approach has some serious limitations, especially if you wish to determine actual numbers of the microorganisms in/on a plate. The number of organisms growing on the agar surface of a plate is generally determined by counting the number of colony forming units (CFU) that are present. Each colony (small round growth spot) is considered to have originated from one original bacterium or spore or tiny chain or clump of the microorganism that is growing. Therefore, if you had spread 1 mL of water on the surface of the plate and you counted 100 colonies, you would conclude that there had been 100 living microoganisms in the original 1 mL of water that you spread on the plate. This spreading of samples on the surface and expecting to see nice, distinct and separate colonies generally does not work the way you visualize. More often there is a running together or clustering of growth or one or more colonies spreads over the entire surface of the agar so that it is impossible to make any accurate counts of organisms. However, people continue to try to use this approach because until recent years there was no easy-to-use alternative.

There is now available a better way to approach projects where you wish to know the actual numbers of microorganisms/unit of the test sample. This is by using the pour plate method with Easygel, a medium available from Micrology Laboratories (and many science supply houses such as Wards, Fisher, Connecticut Valley, VWR, Science and Boreal and others) which uses a temperature independent gelling agent instead of agar. Each Easygel test is provided as one small bottle of liquid medium and one specially pre-treated petri plate. To obtain a solid plate similar to a pre-poured agar plate, all you need to do is pour the contents of the bottle of liquid medium into the pre-treated petri plate, swirl to cover the bottom and let stand on a level surface for about 45 minutes to solidify. It can be then used the same as a pre-poured agar plate. However the best way to use Easygel when you want to determine the number of microoranisms in a sample is to add the sample directly into the bottle of liquid Easygel, swirl gently to mix, pour the Easygel/sample mixture into the pre-treated petri plate, allow to solidify and incubate. Following incubation, count the number of colonies growing throughout the medium. With this approach the colonies are locked throughout the solid medium instead of just growing and spreading on the surface, and a very accurate picture of the number of colonies is obtained as they do not spread or clump together as in the surface streak procedure. This approach works for either liquid or solid samples. Solid samples are normally measured out (eg-10 grams) and blended in a measured amount of sterile diluent (eg-90 mL of sterile water) and 1-5 mL of this diluted sample is added to the Easygel.

3. Another approach which may work well is the membrane filter (MF) method, where a liquid sample is passed through a fine pore filter and the filter containing the microorganisms is placed on a pad soaked with a nutrient medium and incubated. The microbes grow as individual colonies on the surface of the filter. This works particularly well when testing water quality and Micrology Laboratories is the exclusive source of patented media that identify coliforms and E. coli in liquid samples by the MF method.

4. Many persons are unsure of how to decide what type of nutrient medium should be used for their project. Most persons who have some familiarity with microbiology are aware of a general medium called "Nutrient agar or Nutrient Easygel" and think that it is the best one to use for general studies. Actually, nutrient agar will grow most non-picky microorganisms, but it is not as rich or good a medium as Total Count Easygel (also known as SPC for standard plate count) or Tryptone Soy medium. For general total population determinations we generally recommend Total Count Easygel. The microorganisms that grow on/in these media are generally colorless or white appearing. If one is not familiar with what colonies look like and wishes to make observation and counting easier, these media are available in what Micrology Laboratories calls their "T-salt" formulation, where a special reagent is incorporated in the pretreatment layer in the petri plate that causes the colonies to grow pink or red.

Micrology Laboratories also has other special media available that will aid in the differentiation and identification of specific types of microorganisms. For example, our Potato Dextrose Antibiotic medium allows only molds and yeasts to grow and not bacteria. And our Coliscan Easygel or MF media differentiate E. coli as dark blue-purple colonies and General coliforms as pink colonies. Our ECA Check membrane filter medium differentiates E. coli as dark blue/purple colonies, Coliforms as lighter blue -blue grey colonies, Salmonella spp. as green colonies, and Aeromonas spp. as pink colonies. It is a bit more difficult to interpret than the Coliscan for the inexperienced beginner. The Coliscan and ECA Check media are ideal for the determination of water quality as they indicate the level of the fecal bacterium E. coli as well as other closely related bacteria. These media are being widely used by water monitoring groups and laboratories because they are so simple to use, but give the most accurate results of any method currently available at a low cost per test. Click on the "FAQ" on our home page for a lot more information on these chromogenic media and also for more general information about our technology.

5. Many persons worry that working with microoganisms is dangerous and unsafe. This attitude is basically due to inexperience and ignorance. Our media are provided in sterile form, contain no harmful ingredients, and the microbes that grow on them have generally come from the environment. All microbes should be treated with respect as many can cause illness if handled carelessly so that they are smeared on body surfaces or ingested. However, if one is careful not to spill or directly touch the living colonies with your hands there is very little danger of bacterial colonies leaving the petri plates in which they are growing. Some basic precautions are recommended. First, you can clean your hands with a paper towel moistened with rubbing alcohol (available at any drug store). This effectively eliminates most microbes. Second, you can use scotch tape to tape the petri dish shut so that the lid will not be inadvertently removed and direct contact with the microbes made possible. Third, incubate solid plates upside down (after they have been given 1-2 hours to completely harden) so that excess water will not form in the plate and be spilled. Fourth, for disposal, a teaspoon of straight household bleach (Clorox, Purex or generic) can be added to cover the medium-microbe layer in the plate. This will kill virtually all microbes within minutes and the plates can then be disposed of. Also, alternatively, plates can be put in an oven-proof bag, sealed and placed in a 300 F. oven for an hour which will kill all microbes.

6. Micrology Laboratories offers a 41 page manual titled Microbiology for Everyone authored by longtime microbiology teacher Dr. Jonathan Roth which explains many basic principles and background items about microbiology and also gives explicit instructions and ideas for many interesting and easy to do projects. It comes in looseleaf form and may be purchased for only $6.00 + S & H. Teachers and students alike have given it excellent reviews.

The technologically oriented world of today is most fascinating. The environment is one of our most treasured and important resources and microorganisms are involved with virtually all of the natural processes on earth. To have a better understanding of the microbial world is to take a step toward better health, cleaner environment and a better world. Microbiology need no longer be considered a difficult, scary and inaccessible biological specialty. With the materials and methods offered by Micrology Laboratories, it is truly Microbiology for Everyone.

Suggestions for preparation of samples with Easygel Media

1. Liquid Samples: If the material you wish to test is in liquid form, such as water, milk or juice, no special preparation of the sample is necessary. All you need to do is to add the sample (1-5 mL) directly into the small bottle of liquid Easygel medium, swirl gently to mix with the Easygel, pour the mix into a pretreated plate, swirl to cover the bottom of the plate, let stand on a level surface for about 45 minutes until the Easygel is solid and incubate.

It is important that you know how much volume of liquid sample you have poured into the Easygel so that you can determine the number of organisms in a given volume of the material you are testing.

If you have so many organisms in your material that adding 1 mL to the Easygel would result in an uncountable number of colonies (over 1000), you may need to dilute your original sample by adding a measured amount of it to a measured amount of sterile diluent. For example, if you add 1 mL of your sample to 99 mL of a sterile diluent and shake it well to mix, and then take 1 mL of this sample/diluent mixture and add it to a bottle of Easygel and pour into a pretreated plate, the number of colonies that grow must be multiplied times the dilution factor to determine the number or organisms/mL. (If you counted 100 colonies in such a plate, you would multiply times the dilution factor of 100 to determine that the actual number of organisms in your original 1 mL sample of test material was 10,000.)

The diluent that is most commonly used is a sterile 0.1% peptone water. That is, 1 gm of peptone is mixed with 1000 mL of deionized water and sterilized to make 1 liter of diluent. Just plain deionized or distilled water which has been boiled and cooled will generally work OK.

2. Solid Samples: If the material that you wish to test is a solid like soil, cheese, spices, ground meat, etc., it is necessary to blend it with a diluent if you wish to determine the number of microorganisms in it. Generally, you should weigh out a given amount of the material (like 10 grams) and homogenate it in sterile diluent in a clean blender for 2 minutes. For example, if you blended 10 grams of ground meat in 990 mL of diluent and then added 1 mL of this mix to a bottle of Easygel, poured it into a pretreated plate, allowed to solidify and 20 colonies grew in the plate, you would multiply times the dilution factor of 100 to determine the number of organisms/gram of your original solid test material. (You had one gram of ground meat in 100 mL of the meat/diluent mix, so you had a dilution factor of 100X). This means that the ground meat had 2000 organisms/gram or 2000X453(# gm/lb)=906,000 organisms in one pound of the ground meat.3. Swabbing surfaces: If you are interested in determining the numbers of microoganisms on a solid surface such as a doorknob, countertop or skin, the best way is to swab a given area of the surface and transfer the organisms collected on the swab into Easygel medium. The procedure for accomplishing this is very simple. You will need a sterile swab, a bottle of Easygel and a pretreated petri plate. (Q-tips are a good alternative to sterile, individually packed swabs as they are generally packed sterile in the box.) Take a sterile swab, open the bottle of Easygel and insert the swab to moisten it with the liquid Easygel, wring out the excess Easygel on the inside of the bottle wall as you remove the swab from the bottle, and reclose the Easygel bottle. Using the moistened swab, wipe the surface to be tested (measure a given area to standardize your test–for example, swab 1 sq. inch of surface) and then open the Easygel bottle, insert the swab and twirl it against the inside bottle wall in the liquid Easygel to transfer the collected material on the swab into the Easygel. Wring out the swab on the inside bottle wall as you remove it. Throw away the swab and pour the Easygel containing the material from the swab into the pretreated petri plate, allow to solidify, incubate and count the number of colonies that grow. This approach works much better than streaking the swab on the surface of a hard agar plate or pressing your fingerprints onto the surface of a hardened plate because the organisms are spread throughout the medium in the Easygel so that you can easily count the numbers of colonies, while fingerprints on the surface of a prehardened plate may result in a fine film of hundreds of colonies that are each so tiny that you may think nothing is present.

3. Air Quality: If you wish to know what is floating around in your air space, just pour an Easygel plate, let it harden and then place it in the test area with the lid removed for a given time such as 1-2 hours. At the end of the time, replace the lid, incubate and count the numbers of colonies that appear on the surface of the Easygel.

Ideas for interesting science fair projects

The basic concept of science fair is to encourage students to find a problem to which they do not know the answers and to develop a protocol to follow so that the answers will be forthcoming. Generally there will be a well defined purpose for doing the project and the student may have certain hypotheses that he/she expects to be proven or disproven. Judges look for originality and uniqueness of ideas and design, and how well the student carried out the theme of the project. Following are some suggestions for project themes that could be developed into very impressive studies. The depth of the studies is limited only by the abilities and time that the student and his/her advisor are willing to invest.

1. Environmental Water Quality

       --populations of coliform, fecal coliform, and general bacteria in a local waterway

2. Soil Microorganisms
       --isolate antibiotic producing organisms, grow in pure culture and produce the antibiotics
         in concentrated form.
       --test soils containing differing amounts of organic material or pH for microbial populations
         and determine effects on productivity.

3. Swabbing to determine relative populations of microbes
       --swab skin, kitchen counters, toilet areas, etc. and find the cleanest and dirtiest areas in
         a defined target. Determine if any special treatments will reduce populations and by how
         much.

4. Effects of microwaving on populations in kitchen sponges or wash cloths.

       --try different exposure times on naturally or artificially contaminated test materials.

5. Test used toothbrushes for bacterial populations

       --can soaking in peroxide or mouthwash lower bacteria?

6. Food and Dairy Product Populations

       --raw vs pasteurized milk

       --ground meat

       --juices raw vs pasteurized

       --spices

       --levels of bacteria in precut, packaged salad materials

       --can treatments be devised to reduce microbes without damaging the food?

7. Effects of Temperature on Microorganisms

       --broth cultures of different types placed for different times in boiling water

       --use of high temperature to isolate spore forming bacteria from mixtures

8. Are bacteria present in commercial bottled water?

9. Do Pets Carry Microbes?

      --aquarium water

      --reptile body surfaces

      --cats, dogs