Tuesday, January 24, 2017

Science Fair Project - Growing Bacteria

The science fair at my 9 year old's school is quickly approaching and she once again is super excited to enter a project.  We looked through several possible ideas together and she settled on bacteria growth.  We found a cheap kit of petri dishes filled with agar that included cotton swaps.  All of these can be purchased individually but the price was very good so I went ahead and purchased it as a kit.

We collected bacteria samples from several locations, including my 6 year old's mouth, a doorknob, my cell phone screen, my laptop keyboard, the bathroom sink, and the floor.  We also collected a sample from my dirty cellphone screen but added anti-bacterial soap to the petri dish to see if this halts bacteria growth.  Then we cleaned my cell phone screen and took a sample to test bacteria growth from a cleaned cellphone screen.  We then setup the petri dishes in our homemade incubator.  The goal is to determine which household objects contain the most bacteria as well as to test how anti-bacterial cleaners kill bacteria.

We placed the petri dishes in a plastic container and set a lamp over them to increase the temperature to promote bacteria growth.  Not shown is a thermometer to monitor the temperature.  The kit we used stated temps should be between 85 and 100 F.  Temps over 100 F can kill bacteria so we'll use the thermometer to keep the temperature in that range.  I'll keep you updated.  Hopefully in a few hours we'll start to see some growth!


  1. What kind of lamp did you use? And was it just a clear container?

    1. We used a clear tub that you can buy at Target or any big box store. The lamp was a desk lamp that had a small halogen (I think) bulb inside. I would not use a LED or fluorescent bulb as they probably do not produce enough heat.