Biochemical: Escherichia Coli & Salmonella Typhimurium

The first step in the identification process is generally obtaining isolation. A usual isolation technique for isolation is the streak plate. With this method a small droplet of burnish is spread over the surface of the medium in a pattern that gradually thins the sample let on and separates the prison cells spatially over the sections of the plate. Streaking is substance ab apply to seclude single cells in order to separate different types of bacteria in a mixed sample. The plates apply ar sterile and provide nutrients to sustain growth. Grams Stain is a widely used method of staining bacteria as an aid to identification.It is used to encounter the personal individualism of a sample. Gram staining is used to differentiate bacterial species into two large groups Gram-positive and Gram- ostracise ground on the chemical and physical properties of their cell walls. Grams stain differentiates between two major cell wall types. Bacterial species with walls containing small amo unts of peptidoglycan and lipopolysaccharide, are Gram-negative and bacteria with walls containing relatively large amounts of peptidoglycan and no lipopolysaccharide are Gram-positive.The Gram stain also allows for cell size, shape, and arrangement to be determined. Biochemical testing also helps to post organisms. One type of biochemical test is fermentation tests. Fermentation is the formation of gas, acid, and other products by the transaction of bacteria on pyruvic acid. PR Glucose, PR Lactose, and PR Sucrose fermentation detection can be seen as broth color falsify and the presence or absence of a bubble. Making use of a mannitol salt agar growth can help determine and/or isolate gram positive cocci, interpretations are made by growth and color results.Citrate and Malonate tests are based on differentiating organisms based on ability to grow when an essential nutrient is available in a limited number of forms. The results are interpreted based on color change and growth, wi th any change resulting as positive which means citrate is utilized. Malonate is utilized and positive if the liquid changes to dark blue. Hydrolytic enzymes that are used in reactions that use water to split complex molecules, these enzymes are detected by the Urease and Bile Esculin tests, which explicate identifiable color changes in the medium. A positive Bile Esculin test esults when the medium is darkened,a nd negative when there is no color change. A positive Urease test occurs when the medium is pink and means a strong urease production and orange/yellow is negative with no production of urease. The catalase test detects an organisms ability to produce catalase, an enzyme that that detoxifies hydrogen peroxide. When catalase is present the reaction is positive and bubbles are formed, absence of catalase is negative and with no bubbles. SIM is a combination media, which includes core tests to differentiate members of a specific bacteria and can be used to replace a sequence of individual tests.SIM tests for sulfur reduction and indole production. Sulfur is reduced when the media is black(+) and sulfur is non reduced when the medium is not black(-). Indole is formed from Tryptophan when there is red in the alchol layer of Kovacs agent and not formed when the reagents color is unchanged. Making use of biochemical test, Grams staining, and streak plate isolation are tools that can be utilized in order to determine the identity of bacteria. Using changes in media to confirm an organism. Each organism has its own characteristics that makes it differ from others, thus the identity can be found.