Lab 5: Gram Stain

Question 1

List the 3 steps of a simple stain

Answer 1

1) Select a dye and add to a heat-fixed sample, leave on for one minute
2) Rise slide with water
3) Blot dry

Question 2

How should you observe a simple or Gram stain?

Answer 2

Under 100x magnification with oil

Question 3

List the 4 steps of transferring a culture to a slide

Answer 3

1) Put a loopful of water onto the slide
2) Aseptically collect a small amount of bacteria from a slant, then deposit and spread into the water on the slide using circular motions
3) Allow to air dry
4) Heat fix by passing the slide through a flame 4 times

Question 4

List the 5 steps of performing a Gram stain

Answer 4

1) Primary Stain: Crystal violet for 1 minute; rinse with water
2) Mordant: Iodine for 1 minute; rinse with water
3) Decolorize: holding slide at a tilt for 4 seconds (until liquid is colorless); rinse with water immediately
4) Counterstain: Safranin for 1 minute; rinse with water
5) Blot slide with KimWipe

Question 5

What color is gram negative bacteria on a gram stain?

Answer 5

Pink

Question 6

What color is gram positive bacteria on a gram stain?

Answer 6

Purple

Question 7

Give an example of a gram negative bacteria

Answer 7

E. Coli