MICROBIOLOGY LAB 3
I.
II.
III.
IV.
V.
VI.
Spore staining (Exercise 10 pgs. 59- 64 background only)
a. Make a smear of Bacillus cereus.
b. Place slide in a petri dish on the slide warmer with heat turned up as far as
possible. Add malachite green and let sit for 10 minutes. If slide dries out
add another drop of malachite. After 10 minutes, rinse slide well with
water to remove all of the green that is on the surface of the slide. Add
safranin for 1 minute, rinse, dry, and then view.
c. Make a drawing of Bacillus cereus and have slide checked by instructor.
Acid Fasting staining (Exercise 9 pgs. 53-58 background only)
a. Read and make notes on principles of acid fast staining
b. Make a drawing from a prepared slide of Mycobacterium smegmatis.
Capsular staining (Exercise 11 pgs. 65-70 – background only)
a. Examine and draw from a prepared capsule slide.
Motility (Exercise 2 pgs. 15-18)
a. Hanging drop
i. Follow procedure on page 16 using hay infusion.
ii. Step 2 – use Pasteur pipette instead of loop
iii. Step 4 – examine under low power and high dry only using phase
contrast (read Exercise 4 pgs. 23-25).
b. Tube method (page 151, 4th paragraph)
i. Take a tube of motility agar
ii. Work in pairs
1. One partner make a stab using Escherichia coli.
2. One partner make a stab using Staphylococcus aureus
iii. Take a small sample of the bacteria using an inoculating needle.
Transfer the bacteria to the motility agar by stabbing it about 2/3 of
the depth into the agar. Do not move needle back and forth!
iv. Incubate at room temperature until next lab period.
Review all slides. Measure organisms. Note sizes in journal and redraw
organisms in proportion to each other according to their sizes as needed.
Color drawings and have drawings checked by instructor before leaving lab.
Journal objectives
a. Spore stain
i. Answer questions 3 and 5 from page 64.
ii. Draw the spore forming organism
b. Acid Fast stain
i. What chemical is responsible for the acid fast property of
mycobacterium?
ii. Why is it better to use an older organism for acid fast staining?
iii. Draw the acid fast organism
c. Capsule stain
i. Answer questions 1, 2, and 7 from page 70.
ii. Draw the encapsulated organism.
d. Motility
i. When do you think the tube method would be used over the
hanging drop method?
ii. After viewing the results of the tube method, make a drawing of a
motile and a non-motile result.
Last modified7/18/07 blt