DENTIEYING AN UNKNOWN CULTURE (7 pts) Hypothetically: You are given an unknown b
ID: 198718 • Letter: D
Question
DENTIEYING AN UNKNOWN CULTURE (7 pts) Hypothetically: You are given an unknown bacterial broth with the following three options as your unknown identity--Escherichia coli, Micrococcus luteus, or Pseudomonas aeruginosa. From your research, you know that your hypothetical E.coli strain is motile while the other two organisms are not. You also find that the E.coli is lactose positive and mannitol negative while M. luteus is lactose negative and mannitol positive, and P. aeruginosa is negative for both sugars. E.coli and P. aeruginosa are facultative anaerobes while M. luteus is aerobic. And finally, from previous knowledge (aka your notes), you know the Gram stain, cell and culture morphology of the three organisms. After testing your unknown culture using category I-IV tests, you find the following results-you had growth of circular colonies on NA with no visible pigmentation, Gram negative bacilli, motility was indistinguishable because the needle was slanted when you inoculated, lactose and mannitol negative, and facultatively aerobic growth in an FTM tube. 1.) What bacterial culture did your lab instructor give you? (2 pts) (There is only ONE correct answer for this and it is one of the three listed above) 2.) Give three reasons justifying your above answer. (3 pts) (Understand that justification of your unknown identity is an important part of your final paper, so give three reasonable answers that leave no room for counterarguments) 3.) Give one good reason why there may have been no colony pigmentation. (1 pt) 4.) Name one thing you would repeat or do over again given limited time and resources and WHY you would want to do this. (1 pt)Explanation / Answer
In this question, the given culture is E. coli.
It is gram negative and no pigmentation on nutrient agar, hence, micrococcus leutus is ruled out. As it give circular colonies on nutrient agar where as pseudomona aerugenosa is giving irregular colonies, hence, it is E. coli.
Among the given culture only Micrococcus leuteus form pigments.
For identification lactose fermenting test will give more clear result. So we should repeat this test again.
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