Microbiology Lab

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Author:
Sandrayang
ID:
38781
Filename:
Microbiology Lab
Updated:
2010-10-08 00:15:41
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Bacterial Metabolic Activities
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Description:
Bacterial Metabolic Activities
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  1. Bacterial Metabolic Activities
    • observing certain metabolic activities of an organism allows the microbiologist to identify its genus and species
    • 3 types: Carbohydrate Fermentation/Oxidation, SIM agar, and Citrate utilization
  2. SIM agar
    • production of H2S, Indole and Motility
    • SIM agar is semi-solid agar that can be inoculated with an organism and observed for production of H2S and indole
    • it also can be observed for motility
  3. H2S
    • the SIM agar medium contains cysteine (an amino acid with sulfur) and iron (metallic ion)
    • some organism can metabolize cysteine producing hydrogen sulfide gas (H2S)
    • H2S combines with iron to form a black metal sulfide

  4. Indole
    • the SIM agar also contain an amino acid called tryptophan
    • some organism can metabolize tryptophan producing indole as a by-product
  5. Motility
    the SIM agar can also be observed for motility
  6. Citrate Utilization of Sodium Citrate
    • to determine the ability of an organism to use citrate as the sole source of carbon for metabolism and growth
    • the medium contains bromthymol blue indicator that turns green to blue if citrate is broken down producing alkaline byproducts
    • if stays green, then it is Citrate negative
  7. Bacterial metabolic activities
    • observing metabolic activities allows the microbiologist determine Genus and species
    • some bacteria ferment or oxidize carbohydrates and the end product is lactic acid
    • when in a OF Glucose Media, organisms that use glucose are classified into 2 groups: Strict oxidizer or fermenter
  8. Strict Oxidizer
    • 2 OF Media tubes are inoculated
    • 1 will have mineral oil to cut off the oxygen called fermentation tube, the other does not called oxidation tube
    • if after incubation, the oxidized tube turns yellow and fermentation tube turns green then it is called the Strict Oxidizer
  9. Fermenter
    • 2 OF Media tubes are inoculated
    • 1 will have mineral oil to cut off the oxygen called fermentation tube, the other does not called oxidation tube
    • if after incubation, the oxidized tube turns yellow and fermentation tube turns yellow then it is called the Fermenter
  10. Indole +
    is always Escherichia coli
  11. Indole +/-
    can be from Pseudomonas
  12. spot indole
    is when it is described as Gram negative rod, indole positive

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