Serratia marcescens not red? HELP NEEDED.

[yoonie2325]

Hello there everybody! I'm a student currently in Biology 11 doing a lab with the bacteria serratia marcescens. When our class swabbed the bacteria platter with the s.mar bacteria and swiped it on our own agar platter, the bacteria was clearly a reddish pigment, however, after putting the bacteria platter that we swiped the s.mar on in an incubator of 37°C for around 3 days, the s.mar bacteria on my platter turned into a clear bacteria without a hint of red, whilst (most of) the rest of my peers had red s.mar bacteria on theirs. I'm really worried I didn't do my lab correctly and confronted the teacher but she told me not to worry and to just be concerned about the amount of bacteria instead of the pigment of it. I had a few peers told me I might have messed it up and now I'm really stressed about it now.

I'm very certain I followed the procedure steps of the lab precisely but this is really strange.

Please help,
Thank you.

[PharmaMan]

Hello,

I'm not sure what to tell you, but I suppose a few things could have happened. Did you swab the plate well enough? Is the agar in the plate ok and not too dried out? Perhaps the bacteria is supposed to not retain the red color after some time. Your teacher didn't seem to be concerned. How are you going to analyze your experiments?

-Pharma

[DrJay]

I have seen references that state that S. mar is red at 25oC and white an 37oC. But I agree with the earlier reply on that if your teacher isn't concerned, not reason or you to be. Try putting a fresh plate of your white bacteria out at room temp for a couple for a couple of days and see if it turns red again.