Week 6: Ex. 11--Bacterial Biochemistry (part 2, pp. 110-115, Amino Acid and Nitrogen Metabolism), practice Gram stains

  1. Vocabulary: carboxylic acid, decarboxylase, tryptophan, others on p. 112
  2. We're not doing the nitrate reduction section of this exercise, but we'll try the rest.
  3. Each group of 4 needs one set of four cultures: Escherichia coli, Bacillus subtilis, Pseudomonas aeruginosa, Proteus mirabilis
  4. Within the group, students should prepare Gram stains of a mixture of B. subtilis and any other organism. If they don't have time to look at the slides, they can come in outside of class.
  5. If you identify some microscopes that don’t work, label them clearly with the nature of the problem and leave on side bench. Tell Mary Rast. Tell students not to use the ones on the side bench and not to put good ones back there.
  6. Inoculations of media are basically those in the lab manual. Have the students use a copy of the inoculation chart in the lab manual.
  7. Be sure to talk about the significance of the tests, how to read the results of each one, how to add reagents to the tryptone broth.
  8. Please inoculate each kind of media on Monday or earlier so that you can add reagents in class and show them what the results should look like for each medium.
  9. Return their lab quizzes and talk a little about them if necessary. Don't forget to record grades!

Lab Orders for Week 6
Equipment:
scopes, Gram stain reagents, loops, needles, slides, test tube racks (one good plastic rack per group plus some extras), 6 cans or beakers for refrigerating gelatin tubes
sterile pipettes for mineral oil (Pasteur pipettes or others, depending on what's available)
Cultures:
one set of four organisms on NA slants per group: Escherichia coli, Bacillus subtilis, Proteus mirabilis, Pseudomonas aeruginosa
Media (consult Dr. Wilson before making media):
one set per group:
Reagents:
Kovac's reagent (for indole test, done on tryptone broth)
Sterile mineral oil in tubes, 1-2/group depending on size of tube