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Name: Evelyn
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What is the significance of S. marcescens,M.luteus, S.epidermidis, and E. Coli? Which of these are gram-positive and gram-negative, and where can these be found? Also, what problems can they cause? When we culture these bacteria, we used four methods: plates, broth, slants, and pour plates. The media was made of TSB, TSA, NAP, and NAD. What is significant about these culturing methods?

I could give you the answer to that question but it is more informative, and fun, to find out yourself. Start with the NCBI library online ( and do a query with the species name, and 'virulence' if you want to know what they're doing to us. Have a look at the taxonomy devision to see how they are related. To find out if they're gram-pos or neg you should do a gram stain if you can. Otherwise you'll find that information in any bacteriology determination guide. Your question about the media is not specific enough so I can't answer it.

Bacteria are a fascinating field of microbiology. Take some time to find out and you'll enjoy it. Have a look at to get the feeling.
Have fun,

Trudy Wassenaar

These questions sound like questions at the end of a lab exercise. In other words, they are questions your instructor wants you to find on your own. The organisms you are using are generally non-pathogenic, except E. coli which can be pathogenic in certain strains. You can find out which are gram-positive or gram negative in any microbiology text book. Or you can go to: or

Van Hoeck

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