Lab Exercise 6A (Indirect Staining and Motility)

Question 1

Know how to prepare a smear
Why do you do this?

Answer 1

Drop of water on slide then add cells, air dry, heat fix (pass X3 )
Kills and glues cells

Question 2

What are the advantages and disadvantages to staining?

Answer 2

Increase contrast (color cell vs. color background)
makes structures visible
kills cells (they don’t move; can’t infect)

Question 3

How do stains work?
What are they? Why do they stick to cells?

Question 4

What’s the difference between a simple stain and a differential stain?

Answer 4

Simple Stain- one step, all cell types will be the same color
kk
Differential Stain- multiple steps, different cells will appear different even though they were all treated the same

Question 5

What’s the difference between a direct stain and an indirect stain?

Answer 5

Direct Stain: stains the cells, white background / basic dye(alkaline) + ion (cation) is colored

Indirect Stain: Stains the background cells are white/ acidic dye - ion (anion) is colored

Question 6

What are the 3 cell shapes and there arrangements

Answer 6

1) Cocci= Spherical
Diplococci (pairs)/ Streptococci (chains)/ Tetrad (four)
Staphylococcus (clusters)/ Sarcinae (cubical packet)/
Single cells
2) Bacilli= Rod-like or cylindrica
Diplobacilli (pairs)/ Streptobacilli (chains)/
Palisading (side-by-side)/ V-shaped/ Single Cells/
Coccobacilli (short rods)
3) Vibrio and Spirilla= curved
Vibrio (One- half spiral turn: Moon like)
Spirilla (full spiral turn)

Question 7

Know how bacterial motility can be determined with laboratory methods.

Answer 7

DATA: Running & tumbling RESULT: + CONCLUSION: motile
No running & tumbling RESULT: - CONCLU. : not motile