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Help with identifying a Bacteria - (May/10/2007 )

Hello everybody!

In my microbiology practicum at university I must identify a unknown microorganism, but I don´t know how to handle this problem.

Here are some results I got from my experiments: It is a gram-negative bacillus; rod-shaped; it uses glucose, but not lactose und maltose; it uses citrat and it produces a violet pigment which is after a few days almost black. (see the picture below, in the next days I can post a better one)

Do somybody approximatly know what bacteria this could be or where I can get some good informations?

Thank you in advance and sorry for my bad English.



A wild guess, which you could confirm with Bergy's or (better) sequencing the 16S region -- Chromobacterium violaceum. If so, you might want to be careful, it can be pathogenic.


I don´t think it is very pathogenic. This is a microbiology practicum for beginners and the profs wouldn´t give us a dangerous microorganism.


What media did u use? do u have access to API20e or similar panel kits?


I don´t have access to API20e or similar panel kits sad.gif

I have used 3 different types of agars, here are the ingredients:

Agar 1(pH 7,2)

  • D(+)-Glucose 10,0 g
  • Meatextrakt 4,0 g
  • Pepton (Casein) 4 g
  • yeast extract 0,5 g
  • liver powder 0,5 g
  • Natriumchlorid 2,5 g
  • Agar 15,0 g
  • dest. water 1000 ml
Agar 2(pH ?)
  • Nährboullion(?) 10,0 g
  • Natriumchlorid 5,0 g
  • Agar 15,0 g
  • dest. water 1000 ml
Agar 3(pH 5,6)
  • Maltextract 30,0 g
  • Pepton (Casein) 3,0 g
  • Agar 15,0 g
  • dest. water 1000 ml
Unfortunately I neither know the pH nor the ingredients of the "Nährboullion" of Agar 2.

On agar 1, the microorganism growed best (seperate, konvex colonys and some completely overgrown regions). On agar 2 growed a "bacterial lawn" (very thin/flat, no seperate colonys) and on agar 3 the microorganismn didn´t grow.

Are many bacteriums (that produces violet pigments) known that could be my microorganismn?

And thank you all for your help smile.gif