Science Buddies: "Ask an Expert"

Greetings, I am helping my son with his science fair project which begins this school year and finishes next school year.

He picked the “germ invasion” project and we are having trouble figuring out a valid hypothesis. We understand the “If...Then” but we are having an issue of pinpointing what it should be. We are only using three locations rather than the 7 in the experiment. Bathroom, refrigerator, and kitchen counter. We turned in the outline of the whole experiment and he needs to fix the hypothesis and the problem. Our hypothesis was: If the agar plates are located in hotter environments, then there will be more bacterial growth. Our problem statement revolves around what kind of bacteria. So this kinda has to do with the next issue.

The second issue is we need to know which bacteria we are searching for. We will be ordering the kit for the experiment with the agar plates. Does the kit come with instructions on how to identify specific bacteria? How will we know which bacteria is actually growing? Would we need a microscope? Do I need to send it to a lab for testing? Sorry, just trying to get a little clarification.

Hi there and welcome to Science Buddies!!

This sounds like an awesome experiment, it's going to be a lot of fun!!
Thank you for providing us with details about your experiment, it helps us to give you a full answer!

I see what the potential issue could be with the hypothesis and problem... What sort of materials do you have access to?
If you're doing the experiment at home, then I would definitely recommend shifting the focus of the "problem" to something simpler to measure at home.
When you focus on what KIND of bacteria, this would mean you'd have to determine whether the cultures are gram-negative or gram-positive. This essentially means you'd be determining whether the bacteria is pathogenic or non pathogenic. To do this, a laboratory procedure known as Gram Staining is carried out, and it involves several reagents and materials that a home lab wouldn't have. If you're interested in purchasing a gram staining kit to do this, you certainly can, but in order to keep your project as easy and hassle-free as possible (especially considering the fact that it would require a microscope, sterile conditions, etc....) I'd recommend just pivoting the essential question or "problem" as well as the hypothesis


When you're swabbing different areas of your home, what would the pressing question in your mind be? Personally, I'd be thinking "hmm... what part of the house has the MOST bacterial growth?"
Your question could be along the lines of: Which location in the house has the most amount of bacterial growth?

I would also expand the areas you're swabbing to include more diverse areas, such as places that are cleaned often and places that are considered "high-touch" and are not cleaned often. For example, you might consider swabbing the kitchen counter (which might be cleaned every so often), the toilet seat (gross right? You'll get some neat results!), the light-switches (high-touch), and the refrigerator. Make sure to label your agar plates so you know which is which!!

For the hypothesis, here you would predict what area would have the most bacterial growth. For this, you should directly state the location, as well as include part of the question.
Ex. If different parts of the house are swabbed and grown on an agar plate for 24h, then the (toilet seat, fridge, counter, pick one!!) will have the most amount of bacterial growth.

This simplifies things for you, as it'll allow you to use a technique called "colony-counting" which will let you count the number of bacterial colonies that have grown on each plate, make a table with each location's number of colonies, and figure out easily which location had the most bacteria.


I hope this helps! To summarize, your problem should be centered around which location has the most bacteria, and your hypothesis should pick one area where you predict the most growth will occur.

Please let us know if you'd like us to clarify anything or if you have any other questions at all!
Best of luck and happy sciencing!

Stay nerdy,
lmp1341