Week 5: Ex. 11--Bacterial Biochemistry (part 1, pp. 107-110, Carbohydrate Metabolism), practice Gram stains
- Vocabulary: enzyme, substrate, product, aerobic, anaerobic, pH indicator, Durham tube, fermentation
- Each group of 4 needs one set of four cultures:
Escherichia coli, Bacillus subtilis, Pseudomonas aeruginosa, Serratia marcescens
- Remind students where the incubator is and where their tub is (again, even if you already did). Be sure
students understand that it is their responsibility to come in to observe results on plated and/or
tubed media outside of class. Tell them that cultures should not leave the direct path between the incubator
and the lab (certainly they should not ever take cultures off the 3rd floor.)
- Students should observe their results on Wednesday or Thursday (Tuesday labs) or Friday (Thursday labs).
They can work out among themselves who is going to look at what when, but the results should not be discarded
until everyone in the group has had an opportunity to see them.
- Explain how to read the results for each medium, and what the results mean about the organism's metabolism. Encourage
them to read the pages in the lab manual!
- Within the group, students should prepare Gram stains of each organism and everyone should make a mixed gram stain
from B. subtilis and one other culture (all are Gram negative except Bacillus).
If they don't have time to look at the slides, they can come in outside of class.
- Inoculations of media are basically those in the lab manual. Have the students make a copy (by hand is ok)
of the inoculation chart in the lab manual on p. 108 and use it to record their results.
- Please inoculate a demonstration set of each kind of media on Monday or earlier so that you can show them what the results should look
like for each medium.
- Lab Quiz 2! Covers weeks 3 and 4: Gram stains, simple and differential staining, streak plates).
(not necessarily too much on what they actually saw for results for the latter, unless you are sure that the results were as expected)
Lab Orders for Week 5
Make materials for 36 groups plus extras.
- Equipment:
- scopes, Gram stain reagents, loops, needles, slides, good plastic test tube racks (1/group plus extras)
- Cultures:
- one set of four organisms on NA slants per group: Escherichia coli, Pseudomonas aeruginosa, Serratia marcescens, Bacillus subtilis
- (Note: TA's will need NA slants to make cultures the weekend before this lab meets.)
- Media (consult Dr. Wilson before making media):
- one set per group:
- 4 phenol red glucose broths with Durham tubes
- 4 phenol red lactose broths with Durham tubes
- 6 tubes OF basal medium (oxidation-fermentation medium)
- 4 tubes Simmon's citrate slants
- Reagents:
- Gram stain reagents
- Sterile mineral oil