Bacterial Contamination
Bacterial contamination is when harmful germs get into food, water, or surfaces and make them unsafe.
A single drop of muddy water falls into a clear glass of drinking water. The dark particles spread out through the whole glass, turning it cloudy and unsafe to drink. Even one drop can ruin the whole glass, just as a few germs can spread through food and make it harmful.
Explaining bacterial contamination by grade level
Think about a water bottle you drink from each day. If you do not wash it, tiny germs start to grow inside. You can not see them, but they are there. The more days you skip washing, the more germs build up.
Projects that explore bacterial contamination
Bacterial contamination happens when harmful germs get into water and make it unsafe to drink. In this project, you refill disposable water bottles for three days without washing them, then filter the water and count bacteria colonies on agar. One trial showed bacterial growth thousands of times above the control bottle.
Bacterial contamination happens when harmful germs get into food and make it unsafe. You cannot see these germs, but agar plates reveal them as visible colonies. In this project, chicken baby food produces larger colonies than pumpkin or apple across all conditions.
Harmful germs transfer from surfaces onto food and make it unsafe to eat — and wet food may pick up more than dry. You drop cucumber slices and cheese crackers onto four locations, including a kitchen sink, toilet floor, car porch, and garden grass, for 20 seconds each. After swabbing the food surfaces and transferring samples to agar Petri dishes, colony counts at three days show that cucumber slices collect more bacteria than crackers at every location.
Harmful germs can get into water that people drink — but does a cooler deliver cleaner water than a tap? You swab water from each source, rub each swab across agar in a petri dish, and leave it in a cool dark place for five days. The colony counts show which water source carries more germs.
Bacterial contamination happens when germs from raw chicken get onto surfaces and make them unsafe. In this project, you cut chicken on three plastic and three Microban chopping boards. You then wash the boards, swab each surface, and transfer samples to agar petri dishes. You count bacteria colonies every day for five days.