https://youtu.be/K3-BMFHrsVg On a blank white sheet of paper, sketch a dichotomy
ID: 101471 • Letter: H
Question
https://youtu.be/K3-BMFHrsVg
On a blank white sheet of paper, sketch a dichotomy chart as a flow chart walking through each of your experiments. The experiments were colony morphology, Gram stain, catalase test, MSA plates, penicillin susceptibility, and sheep blood agar plates. Scan or take a picture, and upload this to the Project Drawing Submission folder.
Orange track
In your dichotomy chart, list each experiment in chronological order. For each experiment, branch down to at least two possible results. Write out the possible results, and whether considered positive or negative when applicable. Then, provide at least one bacterial genus that is possible for each result. Lab exercise 9-2 has similar dichotomy charts that can be used for examples (lacking result descriptions though).
This will be graded based on providing the required information for each test, and having correct information. You can use a computer-drawn chart (non-hand drawn) if desired, but you must state that it is your original work.
Write out the discussion section and references (for this section) for these experiments. Write this as if it were part of the whole lab report in manuscript form. This should be at least three paragraphs and contain at least one additional citation/reference beyond the textbook and lab book for this course. Suggestions for the paragraphs:
1) State each of the results and the interpretation of each experiment.
2) Discuss how all the results fit together here or the first paragraph. Make a conclusion, and state why this is your conclusion (can be repetitive with your experimental results/interpretations). Based on your experimental results, how scientifically confident are you for the genus ID? Species ID?
3) Discuss any results/interpretations that are exceptionally clear and unclear/indeterminate. Are there any alternative conclusions that could be made? Discuss at least one other species that could be a conclusion, and why/why not this is a possibility. State at least one other additional test that could have been done in this series, and additionally how nucleic acid testing (genetic tests) OR serology could confirm the final ID.
Explanation / Answer
The tests in chronological order are,
Catalase test: This test determines the presence of enzyme catalase in the bacteria. This enzyme protects the bacteria from the bactericidal effects of hydrogen peroxide. Staphylococcus is catalase positive and Streptococcus is catalase negative.
Colony morphology:
In colonies, organisms may be arranged in chains or in clusters.
Gram staining: Ability of the organism to retain the primary dye. This is based on the characteristics of cell wall. Gram positive bacteria are staphylococcus, Streptococcus etc. Gram negative bacteria includes E.coli.
MSA plates: This is mannitol salt agar. It contains high concentration of salt (7.5% NaCl). This is used as a selective and differential medium for identification of staphylococcus.
Penicillin susceptibility: All gram positive bacteria are susceptible to penicillin.
Sheep blood agar plates: The ability of the bacteria to hemolyse the red blood corpuscles are determined by sheep blood agar plates. It is usually seen in Streptococcus.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.