OCTOBER 20, 2011

Today in class, we completed page 33 in the UP, pages 12-15 in the notes, and finised the bacteria lab.

Page 33: Analyse the diagram provided in the UP and answer the subsequent questions. Correct answers to the questions posted below.

1. Which of the antibiotics would you use to prevent the growth of B. subtilis?

Neomycin is the best antibiotic for inhibiting B. subtilis growth. Aureomycin and erythromycin also work.

2. Which of the antibiotics would you use to prevent the growth of E. coli?

Tetracycline is the best antibiotic for inhibiting E. coli growth. Aureomycin also works.

3. Are both organisms equally sensitive to antibiotics? Explain.

No. More antibiotics inhibit one organism, with greater effect, than the other.

4. Which of the two organisms are more sensitive to antibiotics in general?

B. Subtilis

5. If you wanted to inhibit both organisms with one antibiotic, which would you use?

Aureomycin

6. If E. coli is beneficial and B. subtilis is harmful and you were infected with both, which antibiotic would you use?

Neomycin would inhibit the growth of both bacteria best. Erythromycin would also work.

7. In general, what can you conclude about bacteria and antibiotics from this experiment?

Antibiotics are not as specific as enzymes, and may inhibit the growth of multiple strains of bacteria. Different bacteria are sensitive to different antibiotics with different degrees of sensitivity.

8. What features does this experiment lack that it should have?

A control group

9. How would you correct this omission?

Add a paper disk.

Notes:

Bacteria Lab:

Surface Lab:

1. Find your petri dish. DO NOT open it! Possibly dangerous bacteria could be growing in it.

2. Observe the petri dish. You should see bacteria colonies (they look like little circular clumps). Count the number of colonies present on the surface of the agar. Do not confuse bacteria colonies with fungus, which also may have grown. Fungus will have little "arms." Don't count it!

3. Record the number of colonie in each quadrant.

4. Safely dispose of the petri dish.

Antibiotic lab:

1. Find your petri dish and a metric ruler.

2. Find the zones of inhibition around each antibiotic, if any. They should look like clear, bacteria free circular "halos' around the antibiotic disk.

3. Measure the diameter of each zone of inhibition in millimeters. If the circle of the zone of inhibition is not complete or fully measurable, measure the radius and multiply it by two.

4. Record the diameter of each zone of inhibition for each antibiotic.

5. Safely dispose of the petri dish.

Results of these labs varied between groups. If you were absent today and unable to recive results from your group, here is a sample of some of the results collected today:

Surface Lab:

Control: 12 colonies

Doorknob: 145 colonies

Faucet Handle: 78 colonies

Desk: 178 colonies

Antibiotic Lab:

Control: 0 mm

Streptomycin: 24 mm

Penicillin: 13 mm

Neomycin: 15 mm

Homework: Continue working on reasearch/ scripts for disease project, finish pp. 31-32 in UP for tomorrow, and begin spice lab (pp. 37-41 in UP)

NEXT....Emma