It sounds like you are doing all the right things to get started. Here are some ideas that might help you identify a specific research question on biofilms that you could answer with a controlled experiment. Just read through and see if an idea appeals to you:
Here is a project on a microbial fuel cell from the Science Buddies website. The production of an electric current depends on the formation of a biofilm on the anode electrode of this device:http://www.sciencebuddies.org/science-f ... p026.shtml
Here is a basic project that explores how biofilms form on different surfaces. The bottles in the photographs are coated with algae.http://thehomeschoolscientist.com/biofilm-experiment/
Here is a website for the center for biofilm engineering, which gives a picture review of various topic on biofilm research, and it includes scientific references that you could reach to learn more about the experimental protocols. There are several interesting topics and there is also an e-mail address for the organization that you can write to for more information. One of the topics is mineral transformation, so maybe they would know where you could obtain a culture of Sporosarcina pasteurui.http://www.biofilm.montana.edu/files/CB ... oster4.pdf
Do an internet search for Google Scholar and then search for biofilms and other terms related to your topic. The results of the search will give you abstracts without the complete article, but this should be useful For example, here is a complete article on biocementation. I noticed that one references used Bacillus cereus instead of Sporosarcina.
There are a few hundred articles that might be of interest to you. Some of the references using algal biofilms for wastewater treatment and biofuel production look interesting. http://cdn.intechweb.org/pdfs/28663.pdf
And, finally, since you might have access to a spectrophotometer, you might be able to set up an assay to measure biofilms by staining the biofilm with crystal violet.
I recommend that you spend some more time doing background reading so you can identify the perfect topic for your science project. Let us know if you have more questions.