Microbiology Unknown
You will be given a numbered culture. The object of this exercise is to characterize and
identify the bacterial species. A list of available organisms will be provided.
You will be required to write a prelimary flow-sheet (see below) and a list of proposed
tests based on your gram stain results and initial catalase and/or oxidase test results. In
addition, you will be required to write a full report with a table of reactions and a final
flow-sheet.
Special note: Spelling, improper or incorrect terminology, incorrect format as described
in “How to Write an Unknown Report in Microbiology” and failure to underline or
italicize genus and species of organisms will count off on your score. Each mistake of
this nature will result in a 1 point deduction from the 45 preliminary and 45 final points.
In other words, miss one and your score will be 89, miss 10 and your score will be 80.
Your unknown will be graded based on 3 criteria:
1. 45% - preliminary flow-sheet: Your flow sheet indicates how you will proceed to ID
your bug with the minimum number of tests based upon the Gram reaction, colonial and
cellular morphology, and catalase and/or oxidase reactions. It will reflect your
understanding of the process and will also serve as your media order form. Your
preliminary flow-sheet will be due 1week from the date that you receive your unknown.
At this time you must also have a TSA (or blood agar) plate with a pure culture of your
isolate for inspection. Be prepared to order the media and supplies needed. Bring 2 copies
of your flow-sheet to lab on the due date: one to turn in and one for you to mark up and
keep.
2. 45% - The final report and flow-sheet should be much like the preliminary flowsheet but should reflect any corrections that you made during the process. I should be
able to follow a path from the top of your sheet to the bottom where you have indicated
the identity of your organism by highlighting it. It would not be a bad idea to indicate the
entire path by highlighting the result that you got for each test performed. If you need to
include information that does not fit into the flow-sheet format include it at the bottom in
the discussion/conclusion. If you are concerned about some confusing results put it in
your discussion. The next best thing to being right is being aware of what may have gone
wrong. This shows that you know what was going on even if you got the ID wrong. At
the end include a concluding statement based on your results that specifically names your
identified organism.
Rules of the final unknown report
1. no plagiarism – cut and paste from web is plagiarism
2. typed and double spaced, good grammar, spelling, syntax and so forth
3. be clear and concise (no "BS")
4. follow the specified format & methods: list the tests one at a time and tell me
exactly what you used and how you performed them
5. Include a completed flow sheet. It should look a lot like your first flow-sheet with
corrections.
6. Clearly indicate your bug at the bottom.
7. Discussion: Tell me why you did what you did. It is not enough to have
performed the correct tests.
8. You must convince me that you know why. Discuss the implications of the
results. This is your opportunity to editorialize. Discuss sources of confusion and
problems. The next best thing to doing everything right is to understand what
went wrong - convince me. If everything went according to your expectations,
this can be a short section.
9. Finally, make a concluding statement such as: Based upon the
10. Results as described, the organism was identified as...
You will be graded on your logic or lack thereof. You should use the proper line of
reasoning, choose the proper tests, conduct them properly, and attempt to interpret tests
correctly so that I know you understand and worked hard. Anything less will be counted
against you. Even if your organism gives the wrong result, if you have documented your
work properly you may loose very few points, alternatively, sloppy work, little work, or
poor effort will loose points generously.
3. 10% - correct ID. Yes, it is possible to get it wrong and still make a 90. I am much
more concerned with your learning and understanding of the methods and concepts than
correct ID of the bugs.
Other stuff:
1. This is your responsibility. You are on your own and must work independently. You
should only ask questions concerning your unknowns during the lab period.
2. You will only be allowed to use media/supplies that were ordered on your flow sheet.
DO NOT get caught searching for plates, etc.
3. The labs are not commonly open after hours or on weekends. In these cases, lab access
must be arranged ahead of time as a group, otherwise labs will not be accessible.
4. Fresh cultures of organisms for Gram stain controls will be done if requested.