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What kind of organism could this be?

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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What kind of organism could this be?

Postby SweetSarah » Sun Feb 26, 2012 7:44 am

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)

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. 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!!
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Re: What kind of organism could this be?

Postby JorgeLobo » Sun Feb 26, 2012 2:42 pm

You are probably on the right track in cosnidering micrococci. There is one additonal test that should clarify and that should be obvious if you look in Bergey's.
Growth on MSA doesn't establish a bug as a halophile per se, just that it can grow in presence of higher salt concentrations (halotolerant). So staph may be halotolerant but are hardly halophiles.
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Re: What kind of organism could this be?

Postby SweetSarah » Mon Feb 27, 2012 3:27 am

JorgeLobo wrote:You are probably on the right track in cosnidering micrococci. There is one additonal test that should clarify and that should be obvious if you look in Bergey's.
Growth on MSA doesn't establish a bug as a halophile per se, just that it can grow in presence of higher salt concentrations (halotolerant). So staph may be halotolerant but are hardly halophiles.


hey Jorge, thanks for answering so quickly. I was hoping someone would answer me soon. Though I always thought staph were halophiles? that's anyways what I learned in my class...or are you just saying they can be halophiles but usually arent? sorry that just kinda threw me off.
Though am glad you mentioned I was probably on the right track with the micrococcus. I will look up the Bergey's like you said though I don't have the book. I assume it's somewhere I can find online. (For my class my teacher didn't even mention that book and just told us to use our lab books that has many exercises so yeah that's why it's kind of more confusing for me. But will try to look it up) Do you by any chance remember the test or what page it would be on? I wonder if it could be Coagulase test maybe? I haven't performed that one yet but I know it's for Staph, though is it also for micrococci? or could it be something else...hmmmm....
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