September 11

Question 1

Gram Staining Procedure

Answer 1

Primary: Crystal violet

Mordant: Gram’s Iodine

Decolorizer: EtoH

Counterstain: Safrinin

1. Add primary stain. Binds to peptidoglycan.
2. Mordant binds to dye and makes it less soluble, forms CV and mordant complex. Both G+ and G- are dark purple.
3. Decolorizer is added. Critical Step G+ peptidoglycan is dehyrdated by EtOH and complex does not wash off. EtOH penetrates G- outer membrane, and can wash away CV-I complex. G+ are now purple, and G- are colorless.
4. Secondary staining. (counterstain) G- are dyed pink.

Question 2

Archaean Cell Walls

Answer 2

Do not contain peptidoglycan

Usually no outer membrane

Contian Psuedomurein composed of NAG and NAT

Glycosidic bonds

S-layer: if present outer layer of cell, protein or glycoprotein, analogous to outer membrane of G-

Question 3

Capsules

Answer 3

Firmly attached

Helps evade immune system

Question 4

Slime Layer

Answer 4

Helps attach to surfaces

Biofilm formation

Helps cell resist dessication

Loosely attached

Question 5

Fimbriae

Answer 5

Filamentous

Protein

Aids in adhesion (velcro) and formation of pellicles

Not for locomotion

Question 6

Pili/Pilus

Answer 6

Hollow filamentous structure

Aids in attachement

Aids in conjugation (plasmid exchange)

Question 7

Gas Vesicles

Answer 7

Allow microbes to float on water

Ex. Cyanobacteria

Question 8

Endospores

Answer 8

Not produced by all prokaryotes

Produced by some G+ (Bacillus and Clostridium)

Not a reproductive structure

Allow microbes to protect genetic material in harsh environments (UV light, high temperatures, etc)

Very hardy and difficult to kill

May contain dipicolinic acid (heat resistance)

Small acid soluble proteins (SASPs) for UV resistance

Question 9

Endospore Formation in Vegetative Cells

Answer 9

Normal cell

Six Stages:

1. Asymmetric cell division (prespore)
2. Engulfment
3. Cortex formation (cell wall around endospore)
4. Coat (spore coat, Ca2+ uptake, SASPs, dipicolinic acid)
5. Maturation
6. Lysis

Question 10

Endospore Staining Process

Answer 10

Differential Technique

Primary Stain: Malachite Green

Mordant: Steam

Decolorizer: H2O

Counterstain: Safrinin

1. Cover smear with paper towel and place malachite green on paper towel.
2. Place over steam bath. Steam drives malachite green into endospore and vegetative cells, both are green.
3. Decolor. Water washed malachite green from vegetative cells, leaving green spores and colorless vegetative cells.
4. Counterstain with safrinin. Spores are left green and vegetative cells are pink.

Question 11

Flagella Arrangements

Answer 11

Peritrichous

Polar

Lophotrichous

Question 12

Peritrichous Flagella

Answer 12

Covered with flagella

Question 13

Polar Flagella

Answer 13

Located on one end of the cell

Question 14

Lophotrichous flagella

Answer 14

tuft at one end of the cell

Question 15

Bacteria that swarm on agar (examples)

Answer 15

• Proteus vulgaris*
• P. mirabilus*