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Homework Help: Need help creating flowchart for ID-ing microogranism

  1. Dec 15, 2016 #1
    1. The problem statement, all variables and given/known data

    I need help creating flowchart for ID-ing an "unknown" organism. Unknown in quotes because I already know ID of organism.

    2. Relevant equations

    gram + (purple) tetrads and cocci
    forms yellow colonies on NA plate
    catalase +
    coagulase -
    Nitrate +
    oxidase (weakly) +
    Bacitracin sensitive (+)
    Urease +

    3. The attempt at a solution

    This is for ID-ing an unknown organism which the professor decided to help us out and gave us the organism ID. The organism is Micrococcus luteus I know all the tests but I am confused about two main things:

    1.At what point in a flowchart can you say, yes, this is the organism? I'm guessing this has a lot to do with a presumptive ID, and then a confirmatory ID. But how does one know when you reach that point? Also we never went over the idea a "dichotomous key" but does a dichotomous key help out alot in flowchart creation?

    2.How do I know if I have the correct sequence in the flowchart I am creating, and also, which test is considered presumptive and which is confirmatory?

    I obviously started with the gram stain, which gave me purple tetrads. Then I did the catalase test; got bubbles = positive. Next I did the coagulase and it did not clot: = negative. But the next step is confusing me: there are multiple tests I could do, but which tests will differentiate the most?

    Also I know what each test is testing for and its implications for ID-ing (I think I do anyway) and I can provide details if that helps in answering question (so you know that I know I mean). This is undergrad intro to microbio, so the test are pretty common and not that techincal.

    Thanks for any help at all really appreciate it
  2. jcsd
  3. Dec 15, 2016 #2

    Fervent Freyja

    User Avatar
    Gold Member

    Why he didn't just give you the flowchart and ask for you to find it based off the results is beyond me. You need to perform all the tests in order to deduce the identify of your microbe. You can find the microbe using elimination of the other results, which species it could not be and what not. There is no point in creating a flow chart for one species of bacteria. You will have to redo your experiments. I would say he helped you all out too much, because the purpose of the exercise isn't clear after being given the answer. You will need to pretend you don't know the answer already, go through and find the microbe based upon the new results from the experiments. Is this an online course or something?

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