Lab quiz 6

  1. Lysine and Ornithine decarboxylase test:

    Bacterial decarboxylation is the
    removal of the carboxyl group
  2. Lysine and Ornithine decarboxylase test:

    the test will be removing the carboxyl group of the amino acid
  3. Bacterial decarboxy of lysine (an amino acid) results in
    the formation of an alkaline end product
  4. Lysine and Ornithine decarboxylase test:

    pH indicator
    Bromcresol purple
  5. negative and positive reaction
    Purple at alkaline pH - positive reaction

    Yellow at acidic pH - negative reaction
  6. Lysine and Ornithine decarboxylase test:

    broths uses
    • Moeller's Lysine broth
    • Moeller's Ornithine broth
  7. Lysine and Ornithine decarboxylase test:

    add to broth
    1 ml of sterile mineral oil to the top - to promote fermentation by locking out oxygen, and it also prevents false alkalinization at the surface of the medium

    tighten screw caps to create anaerobic environment
  8. Results
    • S. marcescens + +
    • P. vulgaris - -

    P. vularis does not have decarboxylase activity
  9. Phenylalanine Deaminase Test

    Bacteria that produce the enzyme phenylalanine
    • Proteus
    • Morganella
    • Providencia
  10. the enzyme phenylalanine deaminase removes
    the amino (NH2) group from the amino acid phenylalanine to produce phenylpyruvic acid (PPA)
  11. Phenylalanine Deaminase Test

    organisms from other genera of the Enterobacteriaceae
  12. Detection of phenylpyruvic acid is achieved by the addition of
    acidified ferric chloride (FeCl3) to the surface of the medium
  13. Phenylalanine Deaminase Test

    positive negative
    green - positive

    yellow - negative
  14. Phenylalanine Deaminase Test

    P. vulgaris - positive

    S. marcescens - negative
  15. Phenylalanine Deaminase Test

    phenylalanine deaminase agar
  16. Effects of ultraviolet radiation:

    ultraviolet light consists of
    short nonionizing waveslengths of radiation that can be used to kill microbes on surfaces and air
  17. mechanism by which uv light affects microbes
    is through the formation of thymine dimers
  18. thymine dimers form when
    two adjacent thymines on the DNA strand bind to each other, resulting in incorrect base pairing during DNA replication thus cell death
  19. UV radiation is most germicidal at a wavelength of
    260nm - this is the specific wavelength at which DNA maximally absorbs UV light
  20. the killing properties of UV light depend on various factors including
    time of exposure as well as the presence of any materials that may block the radiation from penetrating the cells
  21. Effects of ultraviolet radiation:

    bacteria used
    s. marcescens
  22. Fungi/Yeast

    Fungi are
    a large group of eukaryotic organisms that can exist as unicellular or multicellular
  23. Fungi are divided into three main types
    • yeasts
    • molds
    • mushrooms
  24. Yeast are
    • unicellular
    • facultative anaerobes
    • may from multicellular structures called pseudohyphae (asexual)

    used in many industrial fermentation processes: bread, wine and beer
  25. Mushrooms are
    aerobic with organized multicellular filaments 

    form large fruiting bodies above the ground and mycelium below the ground
  26. molds are
    aerobic with non-organized multicellular filaments called hyphae

    mycelium - a group of hyphae (visible mold)
  27. molds
    heterotrophic: feed on preformed organic matter by producing exoenzymes to digest food into small molecules that can be absorbed by the fungus. "Digest then ingest"
  28. vegetative hyphae
    absorb nutrietns
  29. aerial hyphae
    spores produced by hyphae that extend away from food source
  30. spores have two morphologies
    sporangiospore: spore enclosed within a sac

    conidiospore: not enclosed by sac
  31. we grow fungi on
    Potato dextrose agar 

    it is selective for the growth of fungi over bacteria
  32. Potato dextrose agar
    selective properties: slightly lower pH of 6.5 and high osmotic pressure due to excess dextrose
  33. At acidic pH
    fungi are able to grow faster than bacteria allowing for their selective cultivation
  34. yeast cultures used:
    Saccharomyces cervisiae

    Rhodotorula rubra
  35. Fungi used
    Rhizopus stolonifer - sporangiospore

    Aspergillus niger - conidiospores

    Penicillium notatum - conidiospores
  36. Aerobic plate count technique

    useful for
    measuring the number of viable bacteria in samples
  37. Aerobic plate count technique

    detecting the number of bacteria in a sample is based on
    counting the colonies
  38. Aerobic plate count technique

    desired range
    30 - 300 colonies 

    it is necessary to dilute the sample
  39. Aerobic plate count technique

    sterile tubes are called
  40. after the sample has been diluted several times
    then 1 ml of each dilution is placed into sterile petri dishes. nutrient agar is poured into each dish and mixed thoroughly

    incubate at 35 degrees
  41. the number of bacteria is determined by
    multiplying the colony count by the dilution factor of the counted plate
  42. rod 
    • s. marcescens
    • p. vulgaris
Card Set
Lab quiz 6
Lab quiz 6