Microscopy, Staining, and Classification

Question 1

Which infectious agents are the smallest? Which are the largest?

Answer 1

prions
full size hemiliths

Question 2

How do you calculate total magnification?

Answer 2

objective lens magnification multiplied by the ocular lens magnification

Question 3

What is the definition of resolution?

Answer 3

the ability to distinguish 2 seperate objects as 2 seperate objects. Expressed as the closest distance between two objects

Question 4

How does total magnification affect the field of view?

Answer 4

reduces the field of view

Question 5

how does the TM affect the amount of light that reaches the specimen?

Answer 5

higher the magnification the less light reaches the specimen

Question 6

How do you convert between meters, micrometers, and nanometers?

Answer 6

1 m=1,000,000 micrometers 10^-6
1m= 1,000,000,000 nanometers 10^-9
1 micrometer is 1000 nanometers

Question 7

What is contrast and how do we improve it?

Answer 7

Contrast is the difference between the subject and the background. Adjustments in the brightness of the light and through staining

Question 8

what is light refraction

Answer 8

air into water, it slows down, causing it to change direction slightly. This change of direction is called refraction

Question 9

why do we use immersion oil?

Answer 9

immersion oil has the same refractive index as glass and stops photons from escaping and directs them to the lens

Question 10

what are two difference between a light and an electron microscope

Answer 10

Differences in total magnification
what microbes can be viewed, light microscope can be alive
light vs electrons used to visualize specimen

Question 11

describe the use of fluorescent dyes

Answer 11

The dyes that are present and attached to the sample emit a
wavelength of light that is visible against a black background.

immunofluorescence a fluorescent dye is added to antibodies that are specific for a particular antigen

Question 12

Why must you “fix” a smear to a slide?

Answer 12

prevents the sample from washing away during the staining process

Question 13

What charge do basic dyes have?

Answer 13

Chromophore is positively charged and enters the cell

Question 14

what charge do acidic dyes have?

Answer 14

acidic dyes have a negative charge, stains the background of the smear

Question 15

How does the type of stain (basic or acidic) affect how a specimen is stained?

Answer 15

basic enters cell
acidic stains outside of cells

Question 16

What is negative staining and what is it good for?

Answer 16

Staining the area around the cells. Good for determining cell sizes

Question 17

what is a simple stain?

Answer 17

a single stain that stains structures to achieve contrast

Question 18

what is the function of a mordant in staining procedures? give examples

Answer 18

a mordant holds the stain the structure. Grams iodine or steam

Question 19

describe how to prepare a smear

Answer 19

Add 1-2 drops of distilled water to a clean slide
gently scoop some specimen with an inoculating loop and add it to the water
let the water air dry
fix the smear for 5-10 seconds over the flame
allow to cool before staining

Question 20

What cell structural difference are we distinguishing with the gram stain?

Answer 20

the difference in the peptidoglycan layer

Question 21

Why do gram stain negative lose the purple stain after decolorizing?

Answer 21

the decolorant removes their outer membrane which releases the dye

Question 22

What is an acid-fast stain, and what are the steps? What bacteria types is it used for?

Answer 22

primary stain carbol fushchin
decolorize
counter stain with methylene blue

mycobacterium and norccardia

Question 23

which genera (genus) of bacteria are acid fast and what are two diseases they cause?

Answer 23

Used for mycobacterium (TB and leprosy) and Nocardia and organisms with a waxy cell wall

Question 24

what cell structure is visualized in a capsule stain?

Answer 24

the glycocalyx

Question 25

Describe the color difference for the endospores and vegetative cells in an endospore stain?

Answer 25

Endospore is stained with malachite green and the vegetative cell is stained with safarin

Question 26

describe a flagella stain

Answer 26

stain is added to add thickness to flagella so that they can be easily viewed

Question 27

What are the three domains of life. Which organelle distinguishes the three domains?

Answer 27

Archea, bacteria, Eukaryotes

nucleus

Question 28

what is binomial nomenclature?

Answer 28

genus and species name

Question 29

What is the hierarchy of taxonomy? (8)

Answer 29

Domain, kingdom, class, order, phylum, family, genus, species

Question 30

How are microorganisms characterized by staining?

Answer 30

gram positive, gram negative, acid fast

Question 31

How are microorganisms characterized by serology?

Answer 31

Serological techniques look for antibodies or antigens in the
serum that are produced by microbes or their structures.

Question 32

How are microorganisms characterized by phage typing?

Answer 32

bacteriophage (a type of virus) are specific about the bacteria that they infect. Phage susceptibility patterns can be used to identify bacterial
strains.

Question 33

How are microorganisms characterized by the analysis of nucleic acids?

Answer 33

techniques look for the presence of particular sequences of DNA or RNA to identify and classify microbes