What's the difference between bacteria that is yellow or pink on an agar plate?

I started this project for the Science Fair about bacteria. I had been testing what household surfaces had the most bacteria. When I had tested the toilet seat, some bacteria came out as yellow and others came out as a pink. Does this mean some colonies are on the verge of dying or are they a different type of species?

What's the difference between bacteria that is yellow or pink on an agar plate?
depends on what type of agar plate you are using (blood, maconkey, etc). yellow might be a staph aureus, pink could be serratia, or E.coli. It also depends on how it was incubated and at what temperature.
Reply:Keep in mind that bacteria is found everywhere, not only on surfaces native to a toilet seat, but also bacteria that might have come airbourne from other rooms or dirty pants you might be wearing. So, different colors are more likely to suggest that there are at least two different types of bacteria present on your culture plate (one yellow and one pink). The fact that you are seeing visible colonies on the agar plate makes it improbable that the bacteria are not dying, rather they are rapidly dividing and growing. A better way to test this theory is to analyze the colony sizes and textures (are they fuzzy or smooth) among other observable characteristics to further prove that they are more likely to be different colonies. Like mentioned earlier, its possible that there may be more than one type of bacteria with the same color. It's a good bet that you might be able to uncover that with this method.





Good luck on the Science Fair; I did one of my own back years ago and made it to state.