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This Concept Map, created with IHMC CmapTools, has information related to: LAB 8 - IDENTIFICATION OF BACTERIA THROUGH BIOCHEMICAL TESTING, casein hydrolysis casein The principle protein in milk; causes milk to appear white and opaque., production of indole, production of hydrogen sulfide, and motility procedure Stab tubes of SIM medium with Proteus mirabilis, Escherichia coli, and Enterobacter cloacae. Incubate at 37C., 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., 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., carbohydrate fermentation fermentation An anaerobic breakdown of carbohydrates in order to obtain energy., carbohydrate fermentation chemical reaction If the particular carbohydrate is fermented, either acid alone or acid and gas end products are produced., An exoenzyme called a protease hydrozies casein into amino acids. indicator Casein appears white and opaque. If the agar remains white and opaque, casein is still present. If casein is hydrolized, a clear zone appears arround the growth., casein hydrolysis chemical reaction An exoenzyme called a protease hydrozies casein into amino acids., 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)., Using biochemical testing to identify bacteria concept 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., carbohydrate fermentation carbohydrate Molecules composed of carbon, hydrogen, and oxygen with hydrogen and oxygen being in the same ratio as water, e.g., sugars and starches., 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., 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., catalase test detects the breakdown of hydrogen peroxide into oxygen and water, 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., 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., starch agar detects starch hydrolysis, skim milk agar procedure Streak Escherichia coli on one half of a skim milk agar plate and Bacillus subtilis on the other. Incubate at 37C.
