Identification of bacteria can be a difficult process due to the fact that individual bacterial cells can possess similar structural morphology to other types of bacteria. As we have demonstrated in previous lab experiments there are key biological and chemical processes that are characteristic to different types of bacteria. Using various biochemical tests we can evaluate and detect these different processes to aid in our identification of unknown bacterial samples. The implications of these test results can be applied in the medical world when determining an agent responsible for an infection and the cause of disease. Use of an optimal decision tree to sort the results of biochemical tests helps to identify an organism while using as few
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The Lysine Iron Agar (LIA) black cap tube will be used to test decarbonation lysine, if positive for decarbonation it will have a purple slant and if negative it will be a darker red color. The LIA tube will also be used to test decarboxylate lysine, which will help us distinguish bacteria that will produce hydrogen sulfide from those who cannot. If positive for decarboxylate lysine it will have a purple butt, and if negative it will have a yellow butt. The Sulfide Indole Motility (SIM) blue cap tube is a semisolid agar and it is also used to determine sulfide production, indole formation and motility in Gram negative bacteria. We will be adding a couple of drops of Kovacs reagent following the incubation of the unknown organism. The indole combines with the reagent and if positive it produces a red layer on top of the medium. If the medium has a hazy growth throughout, then is positive for motility and if it produces Hydrogen Sulfide (H2S) a black precipitate is produced. Some bacteria can produce large amounts of stable acids and others produce a smaller amount. In order to know which ones produce more or less we will do the Methyl Red Test (MR) yellow cap tube. We will be adding Methyl Red to the broth after incubation to observe fermentation and it will turn red if pH is below 4.4 (positive result) and will remain yellow if ph is above 6.0 (negative result). The Triple Sugar Iron (TSI) red cap tube is a differential medium. If the organism is able to fermentate any of the three sugars the slant is purple and/or has a yellow butt (negative). If the black precipitate is present, then there was fermentation and H2S was produced. The ability to clear boxylate lysine will produce a purple butt (positive). If the fermentation produced gas the entire slant may be raised above the bottom of the tube. The Simmons citrate green cap tube tests the ability
The Lysine Iron Agar (LIA) black cap tube will be used to test decarbonation lysine, if positive for decarbonation it will have a purple slant and if negative it will be a darker red color. The LIA tube will also be used to test decarboxylate lysine, which will help us distinguish bacteria that will produce hydrogen sulfide from those who cannot. If positive for decarboxylate lysine it will have a purple butt, and if negative it will have a yellow butt. The Sulfide Indole Motility (SIM) blue cap tube is a semisolid agar and it is also used to determine sulfide production, indole formation and motility in Gram negative bacteria. We will be adding a couple of drops of Kovacs reagent following the incubation of the unknown organism. The indole combines with the reagent and if positive it produces a red layer on top of the medium. If the medium has a hazy growth throughout, then is positive for motility and if it produces Hydrogen Sulfide (H2S) a black precipitate is produced. Some bacteria can produce large amounts of stable acids and others produce a smaller amount. In order to know which ones produce more or less we will do the Methyl Red Test (MR) yellow cap tube. We will be adding Methyl Red to the broth after incubation to observe fermentation and it will turn red if pH is below 4.4 (positive result) and will remain yellow if ph is above 6.0 (negative result). The Triple Sugar Iron (TSI) red cap tube is a differential medium. If the organism is able to fermentate any of the three sugars the slant is purple and/or has a yellow butt (negative). If the black precipitate is present, then there was fermentation and H2S was produced. The ability to clear boxylate lysine will produce a purple butt (positive). If the fermentation produced gas the entire slant may be raised above the bottom of the tube. The Simmons citrate green cap tube tests the ability