I did some tests to a bacteria colony and I observed the following:

First of all let's start from the shape and after that we move on to the chemical tests that I did to them:

  • Form: Circular
  • Colour: Yellow-to-white (something like pale yellow)
  • Margin: Entire
  • Elevation: Flat

Chemical results:

  • Gram: Negative
  • Catalase: Positive
  • Oxidase: Positive

After some research to the databases, I figured out that it might be:

If it belongs to the family of Pseudomonas:

  • Chryseomonas luteola OR Pseudomonas luteola group Ve-1 with a chance of 48.21%
  • Flavimonas oryzihabitans group Ve-2 with a chance of 48.21%
  • Xanthomonas maltophilia OR Pseudomonas-like spp, with a extremely low possibility of 1.34%.

So, my question has 3 parts:

  • Can someone please tell me if my hypothesis is right?

  • And if it is possible which bacteria from the above is the correct?

  • If you manage to find the correct type of bacteria can someone tell me the ideal enviroment to study them better? (agar plates, temperature, time needed, etc.) Thank you for all the efforts made!

Important notice: I have used a blood agar plate with a concentration of 5–10%. It contains as far I know, mammalian blood maybe from sheep or horse. I forgot to check the temperature, but I don't think that it is very important.

  • $\begingroup$ Sounds a bit like homework/course work to me... I don't have an answer for you immediately, but if your observation that the cells are circular (coccoid) is correct, it can't be Xantho/Pseudomonas. If the results are to be trusted, that they are G- cocci, there aren't very many options, just Veillionella, Moraxella and Neisseria, pretty much rx.osumc.edu/asp2/microbiology/gramNegOrganisms.pdf. Try Bergey's Manual of Systematic Bacteriology (I can't find an online copy though). Your use of media and temperature can be very important. How was it incubated? Anaerobically? $\endgroup$
    – Joe Healey
    Commented Aug 5, 2017 at 14:37
  • $\begingroup$ @JoeHealey 30 degrees, aerobically. I will check now the Systematic Bacteriology, thanks for that guide! $\endgroup$ Commented Aug 5, 2017 at 14:42
  • $\begingroup$ Aerobically would rule out Veillonella, but I haven't checked whether Moraxella/Neisseria are Catalase/Oxidase positive or capable of growing on blood agar. $\endgroup$
    – Joe Healey
    Commented Aug 5, 2017 at 14:44
  • $\begingroup$ Well I will let you do your research.. When done post the results to the answer. Thanks! $\endgroup$ Commented Aug 5, 2017 at 14:45

1 Answer 1


Consolidating my comments, and taking all the results at face value (though microbiology can be very tricky), the most likely candidates are Moraxella, or Neisseria spp.

Gram negative cocci (spherical cells) rules out a large number of possibilities, leaving just the above 2 and Veillonella as candidates.

enter image description here

The OP said that the culturing was done under aerobic conditions at 30˚C. Veillonella is an obligate anaerobe, and so wouldn't survive this. Both Moraxella and Neisseria are happiest at 37˚C but would no doubt grow at 30. Both are cultivable on blood agar. Neisseria is best cultured in a 5% CO2 atmosphere, so is probably somewhat less likely. Both appear as pale-whitish colonies on plates. The OP's observation of yellowish colouring could be artifactual of the plate colouring, I'm not 100% sure.

Both are positive for oxidase and catalase.

Neisseria on blood agar:

enter image description here

Moraxella on blood agar:

enter image description here

One final comment: both of these are pathogens, so continue with all due caution.

Moraxella, in particular, is a respiratory pathogen, so I would advise working in a biosafety cabinet. I'll assume you already have the relevant paperwork/permission to be handling > BSL1 organisms...

  • $\begingroup$ Lovely answer, covers me 100%. And of course I have permission to work on pathogens... besides thats my future job! Pathologist....(still studing and experimenting but ok) $\endgroup$ Commented Aug 5, 2017 at 15:08
  • $\begingroup$ Great, that's good - thought I'd check. If it was a school experiment or something, they may not have had the relevant safety frameworks, so thought it best! $\endgroup$
    – Joe Healey
    Commented Aug 5, 2017 at 15:13
  • $\begingroup$ University experiment in special labs... and tutors-personnel that are always watching us. $\endgroup$ Commented Aug 5, 2017 at 15:17

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