Question

The chart below describes the biochemical reactions of six different Gram-positive bacteria for the indicated tests. Following the example your instructor presented at the beginning of the lab period, construct a dichotomous key to identify the six bacteria listed below. IMPORTANT: do not start your key with the same test your instructor used to start the example in class. Draw your chart by hand on the next page titled “Dichotomous Key.” Your key should include all the tests needed to specifically identify each of the six bacteria shown below, meaning there should be only one bacterium remaining at the end point of each branch. You may abbreviate the genus name but not the species name. You will not need to use all the tests listed for each bacterium. You will not be running any actual biochemical tests for this exercise; it is intended to let you practice how to construct a key used for identification of microorganisms using biochemical tests. Turn in the second page only.

This is a two-step exercise. After you turn in your dichotomous key, your instructor will return this assignment to you with some test results added in a table format. First, interpret ALL the test results in the table, even if you did not use them for the identification of your organism. Then, use the applicable test results to identify the unknown organism assigned to you. Highlight the path at each step leading to the identified unknown organism using a highlighter before turning in this assignment the second time. You need to turn in this assignment for both steps on the indicated due dates to get full credit.

Identification Practice Learning Objectives: To become familiar with generation of a dichotomous key (identification key) used in identifying microorganisms based on their biochemical test results. Instructions: The chart below describes the biochemical reactions of six different Gram-positive bacteria for the indicated tests. Following the example your instructor presented at the beginning of the lab period, construct a dichotomous key to identify the six bacteria listed below. IMPORTANT: do not start your key with the same test your instructor used to start the example in class. Draw your chart by hand on the next page titled "Dichotomous Key." Your key should include all the tests needed to specifically identify each of the six bacteria shown below, meaning there should be only one bacterium remaining at the end point of each branch. You may abbreviate the genus name but not the species name. You will not need to use all the tests listed for each bacterium. You will not be running any actual biochemical tests for this exercise; it is intended to let you practice how to construct a key used for identification of microorganisms using biochemical tests. Turn in the second page only. This is a two-step exercise. After you turn in your dichotomous key, your instructor will return this assignment to you with some test results added in a table format. First, interpret ALL the test results in the table, even if you did not use them for the identification of your organism. Then, use the applicable test results to identify the unknown organism assigned to you. Highlight the path at each step leading to the identified unknown organism using a highlighter before turning in this assignment the second time. You need to turn in this assignment for both steps on the indicated due dates to get full credit. Bacillus cereus z Clostridium botulinum VgP Cat Nit Man End Lac H2S P P P NP N N N N P N P N N N P P N N V Ν ν Ν Ρ Ρ Ν P P N N N P P P P N Clostridium difficile az z – z Clostridium perfringens Listeria monocytogenes Staphylococcus aureus Dichotomous key format P=positive N=negative V=variable Test Symbols: Bacterium 1, Bacterium 2, Bacterium 3, Bacterium 4 Test 1 Bacterium 1 Bacterium 3 VgP=Voges-Proskauer Cat=catalase Nit=nitrate Man=mannitol End=endospore Lac=lactose H2S=hydrogen sulfide Bacterium 2. Bacterium 4 Test 3 Test 2 Bacterium 1 Bacterium 3 Bacterium 2 Bacterium 4

Answer 1

1. Bacillus cereus, 2. c. botulinum 3. C. difficile 2.C. Perfringens 5. L. monocytosenes b. S. aureus. 11,2,3,4,5,6) END 11,2,3,47 561 Man 12,3,4 7 16 15 H25 p N 13,4]