Mixed unknown

The mixed unknown exercise has been modified for the online experience. You will be receiving PowerPoint images for “Day 1” of your unknown. These images include the Gram stains for both organisms, and isolated colonies on MacConkey’s (Gram-) and Columbia CNA (Gram+) agars. We have created individual Discussion Board threads in your Canvas site in which you will be able to find your PowerPoint images. The ultimate goal of this experiment is to determine the identity of the two bacterial species that you have been given, and writing them in proper binomial nomenclature.

Please find the Mixed Unknown Worksheet here Download here. On the day that the assignment window begins, you will be given your images. IN ORDER TO MAKE YOUR FINAL SPECIES IDENTIFICATION, YOU WILL NEED TO USE THE INFORMATION IN THOSE IMAGES TO ORDER ADDITIONAL TESTS. You will get two media test request deadlines that you can request a total of six (6) tests for each organism—for a total of twelve (12), split between the two submission deadlines. By the first deadline, you should order a few tests that you believe are indicated for your organism(s). Make sure to indicate if you are ordering the test for your Gram+ or Gram – organism. Your instructor will respond with your results for those tests, if indicated. Once you analyze the first set of tests, you may have one additional set of media requests that you believe will narrow down your specific organism. IF YOU DO NOT ORDER MEDIA BY THE FIRST DEADLINE, YOU WILL ONLY GET ONE CHANCE TO ORDER MEDIA.

When ordering media, you MUST use the correct name of the test requested (ex.: order ‘Skim Milk Agar’ test, not ‘casein’; order ‘Starch Agar’, not ‘amylase’, etc.). You will need to have all of the information on this sheet filled out before uploading it to your discussion board thread that has been created for you. Any portion not filled out when you turn it in, will result in no points for that section. You must include the genus and species of your organism, spelled out completely, in proper binomial nomenclature, to receive full credit. YOU MUST CORRECTLY IDENTIFY THE GENUS AND SPECIES OF BOTH ORGANISMS IN ORDER TO RECEIVE FULL CREDIT.

Since MacConkey’s and CNA are already provided, you do not need to order them in your ‘TEST MEDIA REQUESTED” section of the table, but you should interpret the results in the second table of your mixed unknown identification form. For tests that require several results (ex.: IMVIC, carbohydrate fermentation, etc.), please provide the results in such a way that they are easy to understand. For example:

• +/+/-/- could be a way to write your IMVIC results
• G: A/+, S: -/-, L: A/- could be a way to write your carbohydrate fermentation results

In order to help you in determine which test(s) to order, I have created a flowchart Download flowchart. You will have one Gram+ and one Gram- organism and they will be on this flowchart in red. Your job will be to correctly interpret the data and use deductive reasoning to order subsequent media. Keep in mind that some items on the flowchart are not what you should order, but would be shown by another test (ex.: glucose fermentation, sucrose fermentation, and lactose fermentation are the three results you'll receive when ordering carbohydrate fermentation; NaCl tolerance & mannitol fermentation are the two results you'll receive when ordering mannitol salt agar, etc.)

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