Help! "Unknown Bacteria" I have no idea where to look =T

About microscopic forms of life, including Bacteria, Archea, protozoans, algae and fungi. Topics relating to viruses, viroids and prions also belong here.

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Joined: Mon Dec 03, 2012 4:26 am

Help! "Unknown Bacteria" I have no idea where to look =T

Post by stephanie1234 » Mon Dec 03, 2012 4:44 am

I have been having a hard time figuring out my unknown bacteria. I honestly thought all of my test results added up to Staphylococcus Aureus, but my oxidase test read positive. My results were:

1. Gram- +
2. Morph- Coccus, cluster
3. Lactose fermentation- acid, yellow +
4. Gelatin hydrolysis- -
5. Starch Hydrolysis- -
6. Catalase- +
7. Oxidase- +
8. MR/VP- MR + VP -
9. SIM- -, There may be motility I did not account for, but I did not see any

I tried to look in the direction of Micrococcus Luteus or Varians, but I did not have a positive gelatin hydrolysis result. I am at a complete loss of which direction to look as far as what my bacteria is. I asked my instructor if a facultative anaerobe could produce oxidase, and she told me "No, due to only certain aerobic bacteria produce cytochrome C." I am hoping you can send me in the right direction, thank you


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Joined: Tue Dec 04, 2012 4:44 am

Post by Smaguss » Tue Dec 04, 2012 5:00 am

Hello Stephanie,
M. Luteus does not always give a positive for Gelatin hydrolysis and to make matters worse it can return both results for casein hydrolysis as well.
As far as direction to point you in, A litmus milk test would really be the ideal way to get an answer. Your SIM is most likely non-motile but don't count it out I have been told to look for a "tornado" growth around immediate inoculation line or for a "hurricane" growth spread through out the media. Another test, although tricky to read, is the nitrate test. If TSIA slants are available I would run one of those as well.

going off of what you have provided the best ballpark I can give you is one of these three.

S. epidermidis
M. luteus
E. faecalis

Best of luck!

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