Microbio lab report body Essay example

2625 Words11 Pages
Maura Gongora
12th December, 2014
MCB 3020L- Section 018
Unknown #16

This report contains the background information on gram positive and gram negative bacteria, which will aid in understanding the use of specific laboratory experiments to distinguish between the two types of bacteria. Included are the materials and methods used to identify the gram positive and gram negative bacteria and methods which also differentiate between microbes of each group. The implications of the methods of identification used are also described in this report to give an explanation as to why a certain route was taken in carrying out experiment 14. The results of the experiment carried out for the identification of three unknowns are tabulated
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Bacteria that can tolerate the high concentration of salt in the media are from the Staphylococcus genus. A sample of unknown A was also used to stab a gelatin test tube, which contains the gelatinase enzyme that breaks down the gelatin and changes the media from solid to liquid. A sample of the same unknown along with a sample of unknown B was then used to stab a citrate test tube each. The citrate test is used to determine whether the bacteria utilizes citrate as a carbon source. If the bacteria used the citrate, the color of the media turns green, but if the citrate was not used, the media remains blue. The color change in the media is due to the presence of the pH indicator bromothymol blue. Afterwards, a sample of both unknown B and unknown C were used to make single line inoculations on both an Eosin Methylene Blue (EMB) and a Salmonella Shigella (SS) plate. Each plate was divided by a a line in half so that unknown B was inoculated on one side and unknown C was inoculated on the opposite side. The EMB plate contains lactose and dyes eosin and methylene blue. The media is used to differentiate between lactose and non-lactose fermenters. The SS plate also contains lactose in addition to bile salts and brilliant green (dye) to select for species of Salmonella & Shigella. The media also contains some

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