IF so, which type of micrococcus can? From what I know m. luteus forms yellow colonies but not sure about M.varians, I think it's white colonies. But can any type of Micrococci form black color (possibly be H2S) on media? The reason I ask is because all the tests I've done so far point to my gram positive organism being micrococcus BUT all the plates and media I used (whether it was agars, tubes, slants, or whatever) all turned black. Only my PEA agar didn't turn fully black but was slightly discolored. Everything else did though so that really confuses me. I've done the tests many times and always get the same results. So what kind can? I cant find anything on this...
My unknown organism I am trying to figure out is Gram positive cocci (it was in "tiny" purple clusters when I observed it under microscope). So far I've done the following tests below. Which bacteria or microorganism would match the following:
- Gram positive cocci, in clusters
- Catalase positive (+) (meaning that it forms bubbles/gas on catalase test)
- Mannitol negative (-) (on MSA-mannitol salt agar- it doesn't grow or ferment salts)
and -Fructose negative (-) (So, that means it doesn't ferment fructose)
-- I also want to mention that from my agar plates I used all turned to a black/brownish coloration but I'm unsure if this would indicate it's due to H2S (hydrogen sulfide) and that's the main thing that throwing me off. However I've done the streaking sevral times, and seem to have a pure culture according to my gram stains so I don't know if that shoudl be happening. THe gram stains came out fine, mainy in 1 color.
Here are some other details about the media I used:
--Also, the colonies for my gram positive are mostly little, grayish/clear dots. I used blood agar (which had really dark black color around the tiny colonies), chocolate agar and Macconkey agar. Only my PEA agar didn't come out with the black color but all the other ones did. I find it strange my Mac agar came with the color since I looked it up and have been told that too.
Does this sound right? Could my organism still be a micrococccus or staph (since my tests point to those) even with the black color on my plates? And if so what type would produce the H2S or black pigmentation??
Also, from these tests I know that the organism is a type of Staph (or it may be a Micrococcus?), but it isn't Staph aureus since it doesn't ferment mannitol, but am not sure what else it could be or narrowed down to. There was absolutely NO growth at all on my MSA plate so that makes me unsure if it could be Staph epidermidis since I read that grows on MSA but doesn't ferment the manitol so wouldn't be yellow like S. aureus would be. But what type of Staph wouldn't grow at all on MSA?? IS it taht my organism actually isn't a Staph? (all my tests seem to point that it is though so I don't know.) What about Micrococcus species-do those not grow at all on MSA?
That confuses me since isn't staph supposed to be halophiles, that is, salt loving organisms? that's what I always thought anyways :/
Please explain your answer or if you used a link if you could put it in your answer. Sorry for all these questions. am just confused about my results especially the black color. This is for my unknown lab project by the way. I've been looking this up but am having hard time finding what it is. Thanks for all answers!!