Welcome to Science Buddies! You are doing a great project and you have designed a very well controlled experiment. Thanks for posting the photograph; it is very helpful to see what happened.
You are correct about your controls. The agar plate with no bacteria added is the negative control that verifies that you did not have any unexpected contamination. The sample prepared with the kitchen sponge and no sanitizer is the positive control that you are using to compare with your samples.
All of the dots are probably bacteria colonies. The fuzzy colony is a mold.
I can understand your question about your results. It looks like you have more bacteria with the hand sanitizers compared to the control plate. You were expected to either see the same number of a fewer bacteria with the sanitizers.
I would say that your results are inconclusive at this point because the sanitizer samples contain more bacteria compared to the positive control. Here are possible explanations of the results.
1. There may have been something wrong with the plate used for the positive control; perhaps it had dried out.
2. There may be a lot of variation in the number of bacteria obtained when using the kitchen sponge as a source of bacteria. Perhaps the normal range is 2 or 3 colonies to several hundred colonies using the technique you described.
3. Perhaps something went wrong with the experiment that you were not aware of; maybe there was something on the sterile cotton used for the positive control that inhibited the bacteria; maybe you accidentally did not spread the bacteria around on the surface of the plate.
4. Maybe the sanitizers added bacteria to the samples. (This is unlikely, but a possibility considering your results).
Can you think of any other possibilities?
The resolution to the problem is to repeat the experiment exactly the same way again. Rather than using bacteria from other sources like the faucets and door knobs at school (which would add another variable), repeat the results with the kitchen sponge again. To ensure that you are starting with the same number of microorganisms for each plate, start with a very wet sponge, and squeeze the water out into a container and use exactly the same sample for each agar plate. If possible, set up two plates for the control and each sample.
This should help resolve the apparent discrepancy in your results. Since this is a science project, repeating the results and explaining what actually happens are important.
While you are waiting for the bacteria to grow again, you can start writing the sections for your display board. Here is the information from the Science Buddies website that includes the various sections. Your conclusion section for your display board is going to be very interesting with this project. You should double check your teacher’s written assignment to make sure you have included all of the required details.http://www.sciencebuddies.org/science-f ... oard.shtml
Here is a similar project from the Science Buddies website that should give you additional background information for your topic. http://www.sciencebuddies.org/science-f ... #procedure
One more note. How are you planning to discard your plates? Since you are working with unknown bacteria, you should tape the plates and not open then again after they are incubated. And, you should soak the plates in a bucket of diluted bleach for at least an hour before discarding them.
Good luck! Please post again in this topic if you have any other questions.