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Help - Unknown Microbe project - E.coli colony description

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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Help - Unknown Microbe project - E.coli colony description

Postby StacyF » Sun Dec 02, 2007 12:03 am

Hello, everyone. I need help! I am currently taking Microbiology, and have the Unknown microbe project. I have identified my microbe as E.coli. My problem is that I forgot to get all of my information from my streak plate to describe my colony. All that I wrote down was that I thought it was circular, with an entire edge, smooth, and raised. Also I have that it looked translucent and white. I wasn't too confident that I described it properly, and have been trying to find a description for E.coli so that I could compare it to what I wrote down. Does anyone have this information, or a link to a website where I can find it? I have searched and can not find anything. My professor wants us to list the pigmentation, opacity, form, margin, surface, and elevation. I would greatly appreciate the help!
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Postby mith » Sun Dec 02, 2007 12:12 am

You're trying to make up data to fit your conclusion?
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Postby StacyF » Sun Dec 02, 2007 12:55 am

No, I am not trying to make up data. I already have the conclusion. I simply want to find out if my description of my colony matches what it should be. I no longer have my streak plate, and I am curious to see if my description is correct. If it is not, at this point there is nothing I can do about it - I just want to know if what I saw is correct. My professor has already advised me that I am correct in my findings, that it is E.coli. Our lab manual just does not have a description of the colonies, and I am not 100% sure of how to tell if what I thought the colony was is correct. In our lab we only did descriptions of the colonies once, and I am just not sure if I looked at this one properly. Regardless, E.coli is not a microbe that you could identify by a Streak Plate only, so why would you think making up data for a streak plate would match my conclusion? I simply want to know if what I noticed was correct or not - I am not trying to "make up" any data.
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Postby StacyF » Sun Dec 02, 2007 1:17 am

Maybe I should re-phrase this. So as not to be accused of "making up data" - rather than giving me a link to any information, I have already provided my findings in my first post, which were:

Pigmentation: white
Opacity: translucent
Form: circular
Margin: entire
Surface: smooth
Elevation: raised

Can someone simply advise me if my description is correct for E.coli? I just want to know if I was able to properly describe my colony. I already have positive tests in other areas that have 100% determined my microbe as E.coli. I know my other tests are correct - I simply want to know if I described my colony correctly. I have only had to describe one other colony in my lab, and quite honestly – while this should be an easy thing to do, I seem to lack confidence in this area. For me, the hardest part is telling elevation while looking at the Petri dish. Color, opacity, and margin I get. I’m not sure I understand how to tell surface or not. Elevation is hard for me to see, and form is sometimes hard for me to tell as well, although that I believe I can figure out. This is my first micro class, and the first time I’ve had to do these things. I was simply wondering if I was correct. If no one wants to advise me of that, then I will certainly just wait to see what my professor says, and that is fine. Thanks, anyway.
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colony morphology

Postby BDeis » Sun Dec 02, 2007 1:42 pm

You are correct some strains of E. coli are smooth, circular and raised. (Some E.coli is iregular and rough). White and opaque also sound right but I can't be 100% positive.

Do you retain your isolate on a slant or in the freezer? An new plate would grow colonies in 24 hours. Then you could be certian.

Good Luck!!!
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Postby StacyF » Sun Dec 02, 2007 2:04 pm

BDeis - thanks so much for your reply. I do still have my unknown sample - so I could go and do another streak plate on Monday, just to be certain. Our professor keeps our unknowns in tubes in the refridgerator (as a broth). I believe I could get enough growth on the plate by Tuesday, if I place it in an incubator instead of doing it at room temperature only. I believe that I saw it correctly - but I was just a little uncertain. I truly appreciate your response. I also hadn't thought about the fact that it would only take me 24 hours to do another streak plate - so I will try that as well. THANKS!!!
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Postby mith » Sun Dec 02, 2007 3:48 pm

The species I've worked with are white and opaque, except the blue ones that transformed x-gal.
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Postby StacyF » Sun Dec 02, 2007 10:09 pm

I was able to partially see through mine, when I held it up to the light - which is why I put translucent. Opaque means that I wouldn't be able to see through it at all, right?
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Postby mith » Mon Dec 03, 2007 3:17 am

oh you're right, translucent is probably the word.
Living one day at a time;
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Re: Help - Unknown Microbe project - E.coli colony description

Postby playdo » Sun Oct 18, 2009 9:29 pm

Just did this in lab with my prof. My specimen of E.coli had: circular form, filamentous margin (I had a hard time seeing this), raised elevation. We used an antiquated-looking piece of equipment called a "disecting microscope" that magnifies to 200x. So as far as the color? It's unpigmented ("white") and perhaps b/c of this scope that really, the light source was basically an unattached lamp that you had to tilt to get better lighting... to me the E.coli looked a little darker than transluscent. I could not see through the center, but I could kind of through the edge.
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Re: Help - Unknown Microbe project - E.coli colony description

Postby dinarh » Sun May 13, 2012 5:50 pm

can someone tell me the meaning of "existence" in identifying microbes? and what existence does E. coli?
Thank you :)
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Postby dinarh » Sun May 13, 2012 5:52 pm

emm... one more question: what are the characteristics of colony morphology of B. subtillis and isolated-milk-bacteria?
thank you
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