Which food is most prone to bacteria?

This project is to test and inform which foods would grow the most bacteria when dropped on the ground for 30 seconds. I used agar, different type of food, and petri dishes. The agar was used to make the gel while the petri dish held the gel.
Maria Al-aych
Grade 8


No video provided


During this experiment I realized that there should be different types of food from different category types. To  make the experiment more reliable I tried using a dairy product, a vegetable, a fruit, and a wheat product. The carrot being the vegetable I believe that after 20 seconds on the ground the carrot will have less bacteria growth then the others. This is because a carrot isn’t as juicy and messy as a grape or cheese and less attracted to bacteria. Same for the bread (the wheat product.) Overall, I think that the grape and the cheese will be the most attracted to bacteria and the bread and carrot being the least.


How is bacteria formed?

Bacteria is formed by reproduction of binary fission. A bacterium, which is a single cell, divides into two daughter cells.


What conditions are necessary for bacteria growth?

  • Food 
  • Water 
  • Air 
  • Temperature 


What are the most common types of bacteria (indoor)?

Micrococcus, Staphylococcus, Bacillus, and Pseudomonas



The six most common variables are dependant,independent, intervening, moderator, control, and extraneous. Dependant variable is dependent on an independent variable. If the independent changes so does the dependendent. Intervening variable is also known as a mediating variable. It explains the relation between the dependent and independent variable. It is also a hypothetical variable which means you can't actually see it. A moderator is a variable that affects the strength of the relation between the independant and dependant variable. Extraneous variables are known as confounding variables. They aren't the independent variable but can change the dependants. The independent variable in my experiment, which foods are most prone to bacteria, is the food dropped. The controlled variable is the gel because the gel for each food is the same and uses the same procedure.



  1. Get around 10 grams of agar powder and 330mL of room temperature water
  2. Stir the solution for about a minute
  3. Once the solution is fully mixed put it into the microwave for 4 minutes (Make sure the bowl is microwavable) 
  4. Take out the mixture once it starts boiling and let it cool for 2-3 minutes
  5. Slowly pour the mixture into the petri dishes (fill up to the middle or less)
  6. Let the solution solidify for about an hour
  7. An hour later the solution will be a gel
  8. Cut any type of food (in my case) and drop it for a certain amount of time and certain height off the ground
  9. Take a Q-tip or cotton and rub it against the food that you dropped 
  10. Very lightly rub the Q-tip onto the gel in lines or zig zags 
  11. Close the dish ad but it in a warm and dark area
  12. Do NOT open the petri dishes while bacteria is growing this could make you sick and ruin the growth
  13. After a week you have the results 



By observing the petri dish I saw that some bacteria a grown on the lid of the petri dish. In the inside of the dish had many colonies of bacteria. On the very side there is a very visible circle coming outwards. There were also some bubbles forming on the bottom.


The growth of bacteria was very visible in grapes. There is a thick zigzag line with many visible dots.  The bubbles on the bottom are larger and are more above the bottom. The lid have some bacteria on the very edges.


Of all the food I’ve experimented with the bread had the least bacteria growth. There was no bacteria on the lid of the petri dish. The inside only had a couple of colonies. The bubbles are much more risen then the others. There is a circle in the centre in which I believe that was the foundation for other bacteria to be grown.


Just with a quick glance you can see lots of bacteria on the lid all around. The inside has visible lines and has smaller but more bacteria. 



The growth of bacteria is proliferation of bacteria is made into two daughter cells that are identical to the original cell. This process is also called binary fission. 

Bacteria can be measured just by observing the colonies of bacteria. Another way that you could measure the colonies of bacteria very accurately is by using a microscope. The microscope will help zoom in a humans vision allowing them to see smaller objects bigger.  FAT TOM is an acronym for all the conditions necessary for bacteria to grow. The six conditions are food, audacity, time, temperature, oxygen, and moisture. 



  Overall, the cheese was the most prone to bacteria and the bread was the least. My hypothesis wasn’t all right but not all wrong I did say that the cheese was the most prone to bacteria. 


This experiment had many hard parts to it but many pats I enjoyed. It was difficult to find the agar. It took me awhile to find the right type of gel to use and I had countless fails. There are many things I would change in my experiment now that I reflect back If I could do this experiment again I would definitely do each food 3 times so I get a more accurate result,. Although this experiment was difficult at times I enjoyed the experience. In conclusion, I enjoyed the experience and this experiment really made me more informed.



  • The purpose of this experiment is to test which foods are the fastest or the most prone to bacteria. 
  • This would also test if the five second rule was true or wether bacteria wouldn’t be caught on in 5 seconds. 
  • Not only will people be informed if the five second rule was true but so that they know how much bacteria is on your food.
  • You must be cautious and informed if you were to drop a piece of food onto the ground.


Sources Of Error






Thank you to Slides Go! For a template for slides, including pictures and icons.

And thank you to Hafsah Altaf for helping to edit my slides!