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This Concept Map, created with IHMC CmapTools, has information related to: LAB 8 - IDENTIFICATION OF BACTERIA THROUGH BIOCHEMICAL TESTING, skim milk agar detects casein hydrolysis, production of indole, production of hydrogen sulfide, and motility motility Non-motile bacteria only grow wher they are stabbed into the agar; motile bacteria swim away and grow out from the stab line., catalase test detects the breakdown of hydrogen peroxide into oxygen and water, An exoenzyme called a diastase hydrozies starch into glucose molecules. indicator Iodide is added to the plate after incubation. Iodine reacts with any remaining starch in the agar turning it dark brown. If starch is hydrolized, a clear zone appears arround the growth., production of indole, production of hydrogen sulfide, and motility chemical reaction for indole production The enzyme tryptophanase converts the amino acid tryptophan into molecules of indole, pyruvic acid and ammonia., A medium containing indicators or to which indicators are added that react specifically with the end product being tested, giving some form of visible reaction such as a color change. examples of differential media SIM medium, A medium containing indicators or to which indicators are added that react specifically with the end product being tested, giving some form of visible reaction such as a color change. examples of differential media phenol red carbohydrate broth with a Durham (gas) tube, catalase test procedure Add a few drops of 3% hydrogen peroxide to cultures of Staphylococcus aureus and Streptococcus lactis. Observe for foaming., the breakdown of hydrogen peroxide into oxygen and water chemical reaction If hydrogen peroxide is broken down into oxygen and water, the oxygen bubbles through the water causing foaming. If the hydrogen peroxide is not broken down, no foaming occurs., 1) Each different species of bacterium has a different molecule of DNA, i.e., DNA with a unique series of nucleotide bases. 2) Since DNA codes for protein synthesis, then different species of bacteria must, by way of their unique DNA, be able to synthesize different protein enzymes. 3) Enzymes catalyze all the various chemical reactions of which the organism is capable. This in turn means that different species of bacteria must carry out different and unique sets of biochemical reactions. 4) When identifying a suspected organism, you inoculate a series of differential media. After incubation, you then observe each medium to see if specific end products of metabolism are present. differential medium A medium containing indicators or to which indicators are added that react specifically with the end product being tested, giving some form of visible reaction such as a color change., production of indole, production of hydrogen sulfide, and motility chemical reaction for hydrogen sulfide production Sulfur containing amino acids (cystine, methionine) or inorganic sulfur-containing compounds such as sulfite, sulfate, or thiosulfate are reduced to hydrogen sulfide (H2S)., Sulfur containing amino acids (cystine, methionine) or inorganic sulfur-containing compounds such as sulfite, sulfate, or thiosulfate are reduced to hydrogen sulfide (H2S). indicator Hydrogen sulfide reacts with iron salts in the medium to produce ferric sulfide which turns the agar black; if the agar does not turn black, no hydrogen sulfide was produced., A medium containing indicators or to which indicators are added that react specifically with the end product being tested, giving some form of visible reaction such as a color change. examples of differential media catalase test, casein hydrolysis chemical reaction An exoenzyme called a protease hydrozies casein into amino acids., starch hydrolysis chemical reaction An exoenzyme called a diastase hydrozies starch into glucose molecules., If the particular carbohydrate is fermented, either acid alone or acid and gas end products are produced. indicators If acid is is produced, phenol red turns from red (neutral pH) to yellow or clear; if gas is produced, a substantial gas bubble appears in the Durham tube. No fermentation results in no acid and no gas production., phenol red carbohydrate broth with a Durham (gas) tube detects carbohydrate fermentation, carbohydrate fermentation chemical reaction If the particular carbohydrate is fermented, either acid alone or acid and gas end products are produced., A medium containing indicators or to which indicators are added that react specifically with the end product being tested, giving some form of visible reaction such as a color change. examples of differential media starch agar, The enzyme tryptophanase converts the amino acid tryptophan into molecules of indole, pyruvic acid and ammonia. indicator Kovac's reagent is added to the SIM medium. If the Kovac's reagent turns red, indole was produced; if the reagent remains yellow, no indole was produced.
