Biochemical Methods Of A Microorganism s Function

To test the capability of a microorganism’s function, microbiologists have designed many different biochemical methods/tests. There were seven biochemical tests that were used to determine the identification of a gram negative unknown. The seven biochemical tests that were tested for in this experiment were: Sulfur Indole Motility (SIM), Gelatin, Methyl Red (MR), Voges-Proskauer (VP), Citrate, Triple Sugar Iron Agar (TSIA), and Urease. These tests were inoculated and put inside a hot room of 37ââ€" ¦ C for different lengths of times; 24 hours, 48 hours, or eight days. Using these tests, allowed for determining whether the unknown bacterium had the ability to produce H2S, gas, ferment alcohol or acids, the ability to be motile, and the ability†¦show more content†¦The two categories are gram positive and gram negative. The cell walls of gram positive bacteria are composed of several layers of peptidoglycan; within these peptidoglycan sheets, lays the teichoic acids. I n comparison to the Gram positives, the Gram negatives possess a thin peptidoglycan layer with a porous lipopolysaccharide outer membrane. To determine whether a bacterium is gram negative or positive, microbiologists can stain them. The majority of bacteria have no pigment. In the beginning of the process, they are almost all clear. If a bacterium is stained with crystal violet, it will turn a dark purple color. Once the ethanol is added, the gram positive bacterium will retain the purple color, due to its thicker peptidoglycan layer, which can capture this dye in the teichoic acids. However, the Gram negative bacterium will ultimately lose the color and in the end turn a pink hue, once the safranin is added. The makes the very porous lipopolysaccharide layer in the Gram negative bacterium, even more porous, causing it to lose the purple color. (Madigan et al, 25-27). The Sulfur Indole Motility (SIM) is used to test for sulfur reduction, motility, and indole production. The casein and animal tissue that SIM has, functions as the amino acids, wheras the thiosulfate that acts as the iron and sulfur component. When the enzyme cysteine desulfurase catabolizes, Sulfur