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What Is The Positive And Negative Results Of A Gram Negative Bacteria?

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After multiple differential tests, it was concluded that unknown #20 was Citrobacter freundii. After conducting the Gram stain to ascertain that the unknown bacterium was a Gram negative bacilli, the species were inoculated in multiple biochemical tests. The tests that led to the conclusion of a Gram Negative bacteria were Oxidase, lactose fermentation, MR, VP, Indole, and H2S production. For the oxidase test, there were two categories one was for positive and negative results of the test. The positive result had three different types of bacteria while the negative result was the Enterobacteriaceae family. If the result of the test was positive, then there would have been color reaction. However after the test was performed in the oxidase test it showed no color reaction which indicates that the test was negative fitting the Enterobacteriaceae classification. Following was lactose fermentation test to analyze if the bacterium was capable of fermenting sugar. If the test was negative the tube was stayed the phenol red and no gas would have been collected by the Durham tube. However, after being incubated with bacteria, it was observed that the phenol red turned yellow and gas was collected in the inverted tube, signifying the bacteria grew. The changing of the color demonstrated that the pH dropped and that the bacteria is able to ferment sugar. Due to the positive result of the test therefore it narrowed down to a small amount of bacteria. To further narrow the list of
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