Important! What kind of bacteria is this? contains a red color?

For a biology experiment we took samples from the bottom of pool. We put the petri dish then in the incubator for 24 hours, and found some bacteria colonies. They looked like white and yellow spots. Then we put the petri dished in the refrigerator and looked again after 4 days. Some collonies had grown onto each othere and most collonies had become wider. However, some collonies had a red color which we didn't expect. Some of these bacteria also had a ring/donut-shape. We would like to know what kind of bacteria it is, because it could make our experiment more accurate. Does anyone know what bacteria this could be? Please answer.

Important! What kind of bacteria is this? contains a red color?
I agree with the first poster. It sounds like Serratia marcescens. Serratia is a very common bacteria found in the environment, especially in soil, and it is known for its vivid red color. If you have red colonies and they were isolated from outdoors, its a pretty good bet that its Serratia.





Serratia is a rod-shaped bacteria, and it prefers damp environments. It can grow from 4-40 degrees celcius, so that makes sense that you found it growing after refrigeration.





I'm not sure about Serratia growing in pools specifically, but I did find that the EPA (Environmental Protection Agency) requires pool disinfectants to be effective at killing Serratia, so it is plausible that it would be growing in the muck at the bottom of a swimming pool.





Serratia can also cause respiratory infections like pneumonia, so handle with care.





Good luck!
Reply:I am guessing Serratia marcescens. I know they have a red pigmentation but I am not sure about the donut shape.
Reply:Yupp.. it must be serratia... it have red pigmentation.. but it might be contaminated.. who knows.. that the hardest part when doing microbiology experiment.. proper aceptic techniques... as for the ring and donut shape, you must find it colony characteristic..

frangipni