Unknown Lab Report

Topics: Bacteria, Escherichia coli, Microbiology Pages: 4 (891 words) Published: July 8, 2011
Name: Danielle

Title: Unknown Lab Report

There are many reasons for identifying an unknown bacterium. The reasons range from medical purposes, such as determining if the unknown could cause ailments in living things or knowing what microorganisms are needed to make antibiotics. The experiment was done by applying methods in order to identify an unknown bacterium. An unknown bacterium was handed out by Dr. Honer. The appropriate tests were prepared and applied. The first procedure that was done was the gram stain. Under a microscope, if the gram stain is purple, the bacterium is gram positive, if the stain is red, it is gram negative. The next test was the fermentation tests for glucose, sucrose and lactose. If an organism is able to ferment the carbohydrate, there will be acid produced, which will turn the broth yellow. Homofermentation shows that only one product was produced-acid. Other organisms will carry out heterofermentation, the presence of acid and gas. If the organism is unable to ferment the sugar in the tube, there will be no change in the orange/red color of the broth and will be considered alkaline. The following tests that I performed were tests for methyl red and vogues proskauer in SIM media. A positive methyl red test indicates a mixed acid fermentation and would turn the organism’s broth red, if no color presents, it is negative. A positive vogues proskauer test indicates fermentation to neutral products and will turn the broth red, if no color presents, it is also negative. Stab inoculating the SIM media for these tests will also show if the organism produces sulfur or indole and if it is motile. If sulfur is present, then the medium will be black, if it produces indole, the medium will be red, and if it is motile, there will be growth throughout the tube. I also grew the organism on MacConkey agar. After inoculation, visible colonies may or may not be present.

The objective is to identify the...
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