Quiz 1

Question 1

List 5 types of microscopes + 1 advantage of using it

Answer 1

1. Brightfield: can view both living and stained samples
2. Darkfield: can more clearly delineate living (unstained) samples
3. Flourescence: dye allows staining of specific large molecules or structures.
4. Electron: far greater magnificatino and resolution
5. Phase-contrast: enhances contrast; excellent for living samples.

Question 2

Brightfield microscopy

Answer 2

Able to view both living and stained samples

Question 3

Darkfield microscopy

Answer 3

Able to more clearly delineate living samples

Question 4

Flourescence microscopy

Answer 4

Dye allows for staining of specific large molecules or structures

Question 5

Electron microscopy

Answer 5

Far greater magnification and resolution

Question 6

Phase-contrast microscopy

Answer 6

Enhances contrast. Excellent for living samples

Question 7

Why must you always use oil with 1000x objectives?

Answer 7

Because IMMERSION OIL keeps light from bending so that is able to enter the objective lens

Question 8

Parfocal

Answer 8

Multifocused. When one objective lens is in focus, all obejctive lens are near focus

Question 9

Heat fixation

Answer 9

Smears are heated to attach microbes to slide and kill bacteria. Basically frying bacteria onto a plate.

Question 10

What do you do if there is insufficient light to view a specimen?

Answer 10

DECREASE magnification, allowing more light to pass through the objective lens.
Hence, Increasing magnification allows for less light to pass.

Question 11

What do you do where you move from 400x to 1000x but the specimen is no longer in teh field?

Answer 11

You go back to 400x and re-center the specimen. It may have been out of focus

Question 12

What criteria can you use to distinguish artifact from bacteria?

Answer 12

Artifacts are large and different shapes/sizes, while bacteria are small.

Question 13

How do you calculate total magnification?

Answer 13

Objective lens x Ocular lens

ie. Scan lens (objective) = 4x, Ocular lens = 10x, thus total magnification = 40x

Question 14

Ubiquitous

Answer 14

Everywhere around us. Used to describe bacteria

Question 15

Tubidity

Answer 15

Cloudy. Used to describe liquids

Question 16

What does it mean about a broth culture if it is turbid?

Answer 16

Means that bacterial growth is present

Question 17

Explain the difference between a complex and an enriched media

Answer 17

Complex media contains components in unknown exact amounts

Enriched media contains components in exact known amounts.

Question 18

Subculturing

Answer 18

Transferring microbes from one medium to another

Question 19

Source culturing

Answer 19

Where the cultured microbes are obtained from

Question 20

What criteria do you use to know that your loop/needle is sterile?

Answer 20

Flame inoculate the loop/needle.

-Heat until red/glowing along the entire length, then cool for 10-20 seconds (without waving or setting it down)

Question 21

Why do you flame the opening of the test tube and keep the opening at an angle when tube caps are removed during subculturing?

Answer 21

Because this prevents contaminants in the air from falling in

Question 22

Advange of using slant media

Answer 22

Easy to store

Question 23

Advantage of using plate media

Answer 23

able to isolate colonies

Question 24

Advantage of broth media

Answer 24

Able to observe bacteria in their natural arrangment

Question 25

Advantage of deep media

Answer 25

Can grow bacteria to test motility and oxygen requirments

Question 26

Pure culture

Answer 26

Contains only one type of organism

Question 27

Colony

Answer 27

Genetically idential group of organisms

Question 28

Why do you never cross your tracks or re-enter sector 1 when streaking a plate to isolate colonies?

Answer 28

Because the point of streaking is to reduce, but if you cross your tracks or re-enter sector 1, you end up picking up more microbes, making the technique ineffective.

Question 29

Acidic Stains

Answer 29

Anionic Dyes. Used to stain the SLIDES that bacteria are on. Repels acidic negative stains

Question 30

Basic Stains

Answer 30

Cationic Dyes. Used to stain teh bacterial cells. Attracts the basic positive stains.

Question 31

Why must the smear on the slide be completely dry before heat fixed?

Answer 31

Because boiling water destroys normal sturctures.

Question 32

2 Reasons why bacterial smears are heat fixed

Answer 32

1. keeps microbes on the slide

2. Kills microbes

Question 33

Advantage of Simple Stain

Answer 33

Easy to use

Question 34

Advantage of DIfferential Stain

Answer 34

Able to see specialized structures and distinguish between different structures.

Question 35

When you do the capsule stain, why must you counterstain with crystal violet?

Answer 35

Because counterstain provides contrasting color to the primary stain, allowing you to confirm is bacteria is present.

Question 36

Primary Stain

Answer 36

Stains peptidoglycan in all cells purple using Crystal violet

Question 37

Mordant

Answer 37

Increases cell’s affinity for primary stains and intensifies the purple color in all cells using Gram’s Iodine

Question 38

Decolorizing Agent

Answer 38

Removes the crystal violet using 95% ethyl alcohol. The gram positive will remain purple, while the gram negative will become colorless

Question 39

Counterstain

Answer 39

stains the decolorizing gram negative cells red so that they can actually be seen using Safranin. All the gram positive cells will be dark purple/blue.

Question 40

5 Reasons a gram positive organism might appear red after gram staining

Answer 40

1. Its an old bacteria culture
2. Damaged by heat fixation
3. Its a Bacillus sp culture (esp an older one)
4. Over decolorization
5. Primary stain was not left on long enough

Question 41

Why do you heat the primary stain in an endosport stain?

Answer 41

To damage the spore coat so it will take up the stain

Question 42

Under what conditions do organisms form spores?

Answer 42

Spores form when cultures become old and growth conditions worsen. It accumulates waste and lacks nutrients

Question 43

2 genera of bacteria that form spores

Answer 43

1. Bacillus sp

2. Clostridium sp