Lab 2

Question 1

Firmicutes (gram stain and type of cell wall?)

Answer 1

Gram Positive and have one membrane (a thick peptidoglycan layer)

Question 2

Proteobacteria (gram stain and type of cell wall?)

Answer 2

Gram Negative and have two membranes (one thin PD layer and an outer layer of complex LPS)

Question 3

E. Coli (Morphology and gram stain)

Answer 3

Rods and gram negative

Question 4

S. Epidermitis (morphology and gram stain)

Answer 4

Cocci and gram positive

Question 5

what color do gram positive show on stain?

Answer 5

Blue

Question 6

What color do gram negatives show on stain?

Answer 6

Pink

Question 7

What is the first step in gram staining?

Answer 7

Fixation (killing cells and sticking them to slide)

Question 8

What is the purpose of crystal violet in gram staining?

Answer 8

It stains both gram - and gram +

Question 9

What is purpose of Iodine?

Answer 9

Stains gram + but can not get through 2nd membrane of gram -

Question 10

What is purpose of ethanol?

Answer 10

To wash away staining from gram negative surface

Question 11

Purpose of saffrin?

Answer 11

To stain the gram negative bacteria

Question 12

What problems could arise with clusters of cells during gram staining?

Answer 12

The cells would be resistant to decolorization and you could get a false positive

Question 13

Why could old cells get a false result of gram negative?

Answer 13

Because their PD layer has degraded allowing for saffrin staining