-Saccharomyces cerevisiae(yeast)

-Bacillus cerreus (gram positive rod)

-Seratia marscescens(gram negative rod)

-Staphylococcus aureus(gram positive coccus)

I'm taking microbiology and studying for a lab exam. this question will more than likely be on the exa.

On the list, one is not a bacterium. And considering the selection I am wondering about the context of this question (as it does not make a lot of sense to me).

It is an unusual question, but I think an interesting one. I'll try to answer it scientifically:

 

Here are some facts we all know:

* B. cereus is a endospore forming bacteria.

* S. aureus has a natural yellowish-golden pigment (Staphyloxanthin).

* Some strains of S. mersescens have a redish-orange pigment (Prodigiosin).

* S. cerevisiae yeasts have a white pigment.

 

Bacterial endospores are highly resistant to the environmental conditions, such as: radiation, temperature, pH, humidity, etc. We all know that carotenoid pigments on animal and human skin protect them from UV. the same we can say about bacteria. Gram positive bacteria have thicker peptidoglycan cell wall than Gram negative bacteria. So if I had to answer the question, I'll probably place the organisms in the following order of sensitivity to UV:

 

(Less resistant) Saccharomyces cerevisiae>Seratia marscescens>Staphylococcus aureus>Bacillus cerreus (Most resistant).