Print Options

Card layout: ?

← Back to notecard set|Easy Notecards home page

Instructions for Side by Side Printing
  1. Print the notecards
  2. Fold each page in half along the solid vertical line
  3. Cut out the notecards by cutting along each horizontal dotted line
  4. Optional: Glue, tape or staple the ends of each notecard together
  1. Verify Front of pages is selected for Viewing and print the front of the notecards
  2. Select Back of pages for Viewing and print the back of the notecards
    NOTE: Since the back of the pages are printed in reverse order (last page is printed first), keep the pages in the same order as they were after Step 1. Also, be sure to feed the pages in the same direction as you did in Step 1.
  3. Cut out the notecards by cutting along each horizontal and vertical dotted line
To print: Ctrl+PPrint as a list

30 notecards = 8 pages (4 cards per page)

Viewing:

Laboratory Experiments in Microbiology-Exercise 7

front 1

What is the Gram stain useful for?

back 1

It is a differential stain that allows you to classify bacteria as either gram negative or gram positive.

front 2

Who discovered the gram staining technique?

back 2

Hans Christian Gram

front 3

What are the gram staining techniques?

back 3

1.Apply primary stain- (crystal violet) all bacteria are stained purple by this basic dye
2. Apply mordant Gram's iodine- the iodine combines with the crystal violet in the cell to form a crystal violet-iodine (CV-1 complex)
3. Apply decolorizing agent (ethanol). The primary stain is washed out of some bacteria (decolorized) and some are unaffected.
4. Apply secondary stain or counterstain (safranin) this basic dye stains the decolorized bacteria red

front 4

What is the most important determining factor in the procedure of Gram staining?

back 4

bacteria differ in their rate of decolorization

front 5

The bacteria that decolorize easily are called?

back 5

gram-negative

front 6

The bacteria that decolorize slowly and retain stain are?

back 6

Gram-positive

front 7

Why do bacteria stain differently?

back 7

Chemical and physical differences in their cell walls

front 8

Bacterial cell walls are complex lattice structures composed of layers of ______.

back 8

peptidoglycans

front 9

Gram-positive cell walls contain multiple layers of peptidoglycans making them __________.

back 9

thick

front 10

Gram-negative bacterial cell walls contain a__________ layer of peptidoglycans surrounded by an outer layer of lipoproteins, phospholipids and lipopolysaccharides.

back 10

thin

front 11

Crystal violet is picked up by the __________.

back 11

cell

front 12

Iodine react with the dye in the ___________to form CV-1 that is ________ than the crystal violet that entered the cell.

back 12

cytoplasm
larger

front 13

The alcohol decolorizing agent ________________ the cell wall of the ___________ cells.

back 13

dehydrates
gram-positive bacteria

front 14

True or false. The CV-I cannot be washed out of the gram-positive bacteria.

back 14

true

front 15

Safranin stains the decolorized bacteria __________.

back 15

red

front 16

Gram stain is most consistent when used on young cultures less than _______________.

back 16

24 hours old

front 17

Why are cells less than 24 hours better?

back 17

because when the bacteria dies their cell walls degrade and may not retain the primary stain- which would give inaccurate results.

front 18

What are the gram staining reagents?

back 18

Crystal violet
Gram's iodine
Ethanol
Safranin

front 19

What do you rinse the stain with?

back 19

distilled water

front 20

Preparation of Gram staining:

back 20

prepare slide with circle on back of each slide
label the slides for each culture
smear with the inoculated loop
air dry smear
fix the slides

front 21

Gram staining procedure:

back 21

1. starting with fixed smear cover the smear with crystal violet for 1 minute
2. gently wash off crystal violet with water until it runs clear
3.cover the smear with Gram's iodine for 30 seconds
4.gently wash smear with water
5. decolorize with ethanol
6.gently wash off ethanol
7.cover the smear with safranin for 1 minute
8. wash the smear with water
9. blot it dry

front 22

What are some common sources of Gram staining error?

back 22

a. loop too hot
b. excessive heat during heat fixing
c. the decolorizing agent (ethanol) left on too long
d. the culture was too old
e. the smear was too thick

front 23

What color will a gram-negative cell turn?

back 23

pink

front 24

A gram positive cell?

back 24

purple

front 25

Which organism is a coccus?

back 25

staphylococcus

front 26

Bacteria: Staphylococcus epidermidis
name the morphology and arrangement and gram stain result

back 26

coccus
staphylo
purple

front 27

Bacillus subtilis

back 27

rod
single
purple

front 28

Escherichia coli

back 28

single cell
bacillus
pink

front 29

Can iodine be added before primary stain in gram stain?

back 29

yes

front 30

Considering you can't identify bacteria from a Gram stain, why might a physician perform a Gram stain on a sample before prescribing an antibiotic?

back 30

To identify which type of antibiotics to use. There are antibiotics that are gram specific and there are broad spectrum antibiotics that are effective against both gram negative and gram positive