Lab Exam 1 Review

Front 1

Resolution

Back 1

The shortest distance between two points in a microscope's field of view that can be distinguished.

Front 2

Parfocal

Back 2

When moving from a lower to a higher magnification, the image of the specimen is close to being in focus.

Front 3

Total magnification

Back 3

Magnification by objective lens x magnification of the ocular lens.

Front 4

Hanging drop

Back 4

Drop of water and broth are placed on a cover slip which is then placed on a depression slide with a Vaseline surrounded depression.

Front 5

Wet mount

Back 5

A drop of water is added to the slide. Bacteria is then inoculated into drop of water. The edge of the cover slip on the slide touching the edge of the water. Cover slip is slowly lowered to prevent the formation of air bubbles.

Front 6

Simple staining

Back 6

Heat fix smear. Add stain for 1 minute. Rinse with water. Add iodine for 1 minute. Rinse with water. Blot dry.

Front 7

Negative staining

Back 7

Inoculate slide with drop of bacteria. Add a drop of Nigrosin. Use the edge of another slide to drag the dye across the slide. Let air dry and heat fix.

Front 8

Gram staining

Back 8

Inoculate slide and let air dry. Heat fix. Apply crystal violet for one minute. Rinse with water. Apply iodine for 1 minute. Rinse with alcohol. Rinse with water. Apply Safranin for 1 minute. Rinse with water and blot dry.

Front 9

Acid–fast procedure

Back 9

Inoculate slide and air dry. Heat fix. Apply Carbolfuchsin for 3 minutes. Rinse with water. Rinse with alcohol. Rinse with water. Add methylene blue for one minute. Rinse with water and air dry.

Front 10

Endospore stain procedure

Back 10

Inoculate slide and air dry. Heat fix. Apply Malachite Green on napkin on slide. Leave over steam bath for 15 minutes. Remove napkin. rinse with water. Apply safranin for 2 minutes. Rinse slide and blot dry.

Front 11

Capsule stain procedure

Back 11

Add a drop of Congo red stain to the slide. inoculate Congo red with bacteria. Take a second slide, place the edge against the drop and slide back over slide. Air dry. Cover with Maneval's satin for a minute. Rinse with water.

Front 12

Broth Characteristics

Back 12

Turbidity, pigmentation of organism, pellicle, flocullant, sediment, smell

Front 13

Turbidity

Back 13

Cloudy growth in the broth

Front 14

Pellicle

Back 14

floating layer of particles at top of broth

Front 15

Flocullant

Back 15

Small masses floating around in broth

Front 16

Sediment

Back 16

layer of particles concentrated at the bottom of the broth

Front 17

Before starting any work with microorganisms, what is the one thing that needs to be done?

Back 17

Decontaminate the work station using disinfectant

Front 18

How long should a inoculating loop or needle be heated?

Back 18

Until it is glowing red (without making it red hot)

Front 19

Which inoculating instrument is used for a stab culture?

Back 19

A inoculating needle

Front 20

Why is it necessary to incubate plates face down?

Back 20

To prevent the build up of condensation

Front 21

Where should petri plates be labeled?

Back 21

The bottom

Front 22

Describe 5 essential actions to aseptic technique when transferring a broth culture to another broth?

Back 22

1) Cap is removed from sterile broth and tube of mouth is flamed
2) Cooled loop is inserted into the broth
3) Loop is removed from broth and tube mouth is flamed
4) Tube is closed with its lid
5) Loop is flamed and ready to use again

Front 23

Describe 5 actions essential to aseptic techniques when transferring culture from plate to a slant?

Back 23

1) Inoculating loop is heated until red hot
2) Raise the lid of the petri plate just enough to access a colony to pick up a loopful of organisms
3) After flaming the mouth of a sterile slant, streak its surface
4) Flame the mouth of the tube and recap the tube
5) Flame the inoculating loop and return to receptacle

Front 24

One reason for preparing streak-plate?

Back 24

To isolate pure colonies

Front 25

Principle behind Simple/Basic stain

Back 25

Because the dye is positively charged it binds to the negatively charged bacteria staining it.

Front 26

Principle behind Negative/Acidic stain

Back 26

Because the dye is negatively charged, it is repelled by the negative cell surface. this allows slide to be stained but not the bacteria. Bacteria is then visible against background.

Front 27

Principle behind making a smear and fixing it

Back 27

To prevent the sample from being lost during the staining procedure.

Front 28

Principle behind Gram staining

Back 28

Because gram negative cells have thin peptidoglycan, ethanol washes away CV-I. Because gram positive cells have thick peptidoglycan walls, the CV-I is trapped in the cell.

Front 29

Principle behind Acid-fast staining

Back 29

Because acid fast cells contain mycolic acid, when the dye is washed away with acid alcohol, cells do not decolorize.

Front 30

Principle behind endospore stain

Back 30

Malachite green dye is heated because endospores are dye resistant. heating acts as a mordant. Safranin is used to colorize vegetative cells.

Front 31

Principle behind flagella stain

Back 31

Because flagella is thin, flagella stain contains a mordant which allows dye to be piled on flagella making it more visible.

Front 32

Principle behind Capsule staining

Back 32

Because the capsule has a negative charge, a positive dye is added to stain the background. A negative dye is used to stain the cell wall, but leaves the capsule unstained and visible against the background.

Front 33

PEA (Phenylethyl Alcohol) Agar

Back 33

Selective: Inhibits growth of gram negative bacteria.

Front 34

EMB (Eosin Methylene Blue) Agar

Back 34

Selective: Inhibits growth of gram positive bacteria.

Differential: Turns green when lactose is produced.

Front 35

MSA (Mannitol Salt Agar)

Back 35

Selective: High tolerating bacteria grow.

Differential: Turns yellow if bacteria can ferment mannitol.

Front 36

BAP (Blood agar plate)

Back 36

Differential: Alpha hemolysis turns green, beta hemolysis turns clear, Gamma hemolysis has no clearing.

Front 37

MAC (MacConkey Agar)

Back 37

Selective: Inhibits growth of gram positive bacteria.

Differential: Lactose fermentation turns it pink.

Front 38

Hektoen Enteric Agar

Back 38

Selective: Inhibit growth of gram positive bacteria.

Differential: Fermenting colonies turn yellowish color. Non-fermenting colonies turn blue-green. Colonies that turn sulfur into hydrogen sulfide turn black.