Science Buddies: "Ask an Expert"

Hello! I'm doing a project about bacteria growing around school. I have to identify bacteria and I am wondering where is the best source of photos that will help me identify bacteria. Also where is the best place to order supplies for my project. Thank you!

Hi,

Identifying the exact species of bacterium from a colony on agar is only possible for a couple of kinds that have colonies with distinctive colors or forms. Here are some good sources for studying bacteria on agar plates:

https://www.sciencebuddies.org/science- ... p007.shtml
https://www.sciencebuddies.org/science- ... ates.shtml
http://www.stevespanglerscience.com/lab ... g-bacteria

You will probably be using nutrient agar which is a rich medium containing protein and meat extracts along with salts and glucose. Many bacteria and fungi will grow on nutrient agar and some of them are harmful or even deadly to humans, so you need to be very careful when growing bugs that you collect from the environment. Once you swab the plates, attach the lids to the bottoms with some tape so they can’t come off accidentally. https://www.sciencebuddies.org/science- ... fety.shtml

This should help you get started. Let us know when you have more questions.

Good luck!

Sybee

Hi,

To identify Gram Positive bacteria, you can also perform biochemical tests using catalase, starch hydrolysis, and coagulase. To identify Gram Negative bacteria, you can perform biochemical tests using glucose, urease, and oxidase.

Hi,

Just for the sake of scientific accuracy, I wanted to clarify a couple of things. First of all, biochemical tests such as the catalase test, coagulase test, etc. could be used to identify Gram positive bacteria. However, it's much more involved than just doing those simple tests and concluding right away that those bacteria are Gram positive. It requires the use of additional tests and most probably the help of the clinical microbiology lab to clearly identify a species. Just because a bacteria is catalase-positive, for example, does not necessarily mean that it's Gram positive. There are, in fact, Gram negative bacteria that are also catalase-positive. Same things go for the biochemical tests mentioned for Gram negative bacteria. For the sake of simplicity, I would suggest looking into the links that SciB has provided for you. However, if you are able to get people in a clinical microbiology lab to help you, then you can make use of those biochemical tests mentioned above, in addition to others, to more clearly identify certain species. It may be worth it to try to contact a clinical lab to see if anyone is willing to help you out!

Let us know if you have any other questions.

Connie