B.cereus and S. marcscens

zmike

I was doing a UV exposure experiment and after 15 min of uv light B.cereus and than S. marcscens both survived and grew.

This doesn't make sense to me b/c I thought that than S. marcscens shouldn't have any UV resistance??
B.cereus is able to make spores which I am not sure if it would protect it from UV light?

Help? or maybe point me in the direction of a reliable source?

thanks

Ouabache

A reliable source would be your textbook and more microbio books at your library. You are right that Bacillus cereus has some protection from UV radiation by means of an endospore Serratia marcescens is very sensitive to UV radiation (as you suspected). I would double check the culture you started S. marcescens from, was pure and not contaminated. If you have the opportunity, I would start from a fresh culture from a lyophilized vial. Once satisfied, you are starting with a pure culture, I would repeat this experiment.

iansmith

The equipment might be at fault rather than the culture. The germicidal power of UV lamps decrease over time and its usages. How old is the UV lamp?

Also, how do you expose your bacteria? For example, when I used to TA student expose petri dishes but often forgot to remove the plastic lid. The plastic would block the UVs.