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lab practical Flashcards

(79 cards)

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1
Q

parts of a microscope

A 
ocular lens
nosepiece
objectives
stage
slide holder
condenser 
diaphragm
light source
lock screw
coarse and fine adjustment
mechanical stage control
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2
Q

what function does the condenser have?

A

focuses light onto the specimen

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3
Q

what function does the diaphragm have?

A

changes the intensity of the light

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4
Q

equation for resolution

A

wavelength of light / (2 x numerical aperture)

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5
Q

define numerical aperture

A

how far away they need to be from each other to be able to see 2 separate things (want the smallest number)

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6
Q

why do we use oil immersion?

A

in order to capture all the light and not let it escape

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7
Q

how do you get maximum resolution for a lens system?

A

correct alignment & adjusted to focus & oil

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8
Q

cleaning tissue used for microscope

A

lens paper

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9
Q

solvent used on a microscope

A

alcohol

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10
Q

how can you extend lamp life?

A

keeping oil out

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11
Q

brightfield microscopy

A

live & preserved stained specimens
specimen is dark, field is white
provides for cellular detail

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12
Q

dark field microscopy

A

live unstained specimens
specimen bright, field black
provides outline of specimen with reduced internal cellular detail

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13
Q

phase contrast microscopy

A

live specimens
contrasted against gray background
internal cellular detail

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14
Q

fluorescence microscopy

A

illuminates specimen
antibodies with fluorescent dyes emit visible light only if antibody recognizes and binds to cell
diagnostic tool

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15
Q

transmission electron microscopy

A

best resolution
to view internal structure of cells and viruses
for small specimens

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16
Q

scanning electron microscopy

A

produce 3d image
surface of cell
for small specimens

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17
Q

smear prep

A

heatfix, in order to ensure microorganisms are attached to slide and will not wash off during staining. cells are also killed in the process.
problem- may distort cells

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18
Q

simple staining (positive)

A

chromophore is positively charged, on inside of cell
requires heat fixing
need oil
distorted

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19
Q

negative staining

A

chromophore is negatively charged, on outside of cell
requires NO heat fixing
no oil
better shape

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20
Q

how does a smear prep of cells from a liquid medium differ from prep of cells from a solid medium?

A

must add a drop of water to slide before adding solid medium

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21
Q

what causes a stain to adhere to bacterial cells?

A

charge attraction

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22
Q

what is the difference between basic and acidic dyes?

A

Basic dyes have a positive charge and acidic dyes have a negative charge.

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23
Q

what are chromophores?

A

color bearing ions

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24
Q

shape of: bacillus

A

rod

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25
shape of: coccus
spherical
26
shape of: spirochetes
spring
27
shape of: spirilla
cork screw
28
shape of: coccobacillus
short rods
29
shape of: vibrios
curved rod
30
arrangement of: strepto
chains
31
arrangement of: staphylo
clusters
32
arrangement of: tetrads
packets of 4
33
arrangement of: sarcinae
packets of 8, 16, 32
34
arrangement of: palisade
ununiformed clusters
35
advantages and disadvantages to a negative stain
not kiling cells | cant differentiate between cells
36
advantages and disadvantages to a positive stain
can use oil immersion | kill cell
37
``` Gram stain colors: postive crystal violet gram's iodine ethyl alcohol safranin ```
crystal violet: purple gram's iodine: purple ethyl alcohol: purple safranin: purple
38
``` Gram stain colors: negative crystal violet gram's iodine ethyl alcohol safranin ```
crystal violet: purple gram's iodine: purple ethyl alcohol: white safranin: pink
39
gram positive
coccus
40
gram negative
rod, more disease because thinner peptidoglycan layer
41
why is the gram strain considered a differential stain?
differentiates between two kinds of bacterial cells based on their cell wall structure and composition
42
how do gram positive and gram negative bacteria differ in cellular structure? how does this contribute to their differential staining properties?
a gram positive cell- has a thick cell wall, retains the crystal violet dye better in the presence of a decolorizer gram negative cell- which has a thin wall
43
How does the age of a culture affect the Gram stain reaction? What is an optimum culture age for a valid Gram reaction?
old cultures of gram positive cells may not retain stain as well as younger cultures and could give false negative results. 16-18 hours are best
44
Which step in the Gram stain procedure is most prone to error? If done incorrectly, how might that step affect the end result?
The decolorizer step is very important because it is the step in which the cells become differentiated (gram-positive cells are purple and gram-negative cells are colorless). If too much decolorizer is used, gram-positive cells will lose the primary stain and be counterstained pink. If too little decolorizer is used, gram-negative cells will not lose the primary stain and will remain purple after counterstaining.
45
In what type of cell, gram positive or gram negative, would you find lipopolysaccharides in its cell wall?
gram negative
46
what is the function of a mordant? and which reagant serves this purpose in the gram stain procedure?
it causes the primary stain to adhere better or be taken up by the cell so that it is not removed during the decolorizing step. Gram's Iodine
47
if you omit the mordant step while gram-staining Staphylococcus areus, what color will it stain?
pink
48
if you omit the decolorizing step while gram-staining Escherichia coli, what color will it stain?
purple
49
What are the functions of endospores in bacteria?
Endospores are resting stages that allow bacteria to survive conditions unfavorable for growth.
50
what is the mordant in the spore stain?
boiling, It causes the endospore to expand allowing stain to penetrate the structure
51
what unique chemical compound is important in the heat resisitance of endospores?
calcium dipicolinate is found only in endospores and not in vegetative cells. it is associated with heat resisitance
52
what conditions are necessary to destroy endospores? in what device are these conditions achieved?
endospores must be exposed to 121 degrees C, 15 pounds of pressure for at least 15-20 mins. these conditions are achieved in the autoclave
53
identify some spore-forming bacteria that may be responsible for disease
Clostridium, Bacillus | clostridium tetani, Bacillus anthracis
54
Escherichia coli
gram reaction: gram negative shape: bacillus arrangement- none
55
Staphylococcus epidermidis
gram reaction: gram postive shape: cocci arrangment- staphylo
56
advantages and disadvantages to standard plate count
can see living cells | time consuming
57
equation for calculating the number of cells in culture tube
number of bacteria per ml = number of colonies X dilution factor
58
equation for total number of cells in original culture tube
total number of cells in original culture = number of bacteria / ml X volume of broth in culture tube
59
advantages and disadvantages to turbidity
quick | see both living and dead cells
60
methylene blue
simple stains/ postive
61
malachite green
spore
62
crystal violet
gram stain
63
india ink
negative staining
64
if forget mordant
pink
65
Staphylococcus aureus (gram type, shape)
gram-positive, coccus
66
sugar fermentation reactions
- can the organism break down certain sugars - does it produce acid and/or gas - phenol red - fermentation tubes catch gas - positive: yellow (orange- slow) - negative: red or pink
67
mixed acid fermentation
- determines if mixed acids are produced in the presence of glucose - methyl red - MR-VP test tube - positive: red - negative: remain yellow
68
Voges Proskauer test
- determines if butanediol (acetylmethylcarbinol or acetoin) is produced by the fermentation of glucose - MR-VP tube &broth - reagent A&B - positive: red within 5 mins - negative:
69
Simmons Citrate test
- determines if bacteria can use citrate as sole source of energy and carbon - citrate agar slant (bromothymol blue) - positive: blue - negative: green
70
catalase test
- indicates the presence of catalase in an organism (enzyme) - dribble H2O2 down slant of agar to see bubbling (reagent) - positive: bubble (gas produced) - negative: no bubbling
71
nitrate reduction
- determines if bacteria can reduce nitrate to nitrite or other nitrogenous compounds - A & B reagent - reduced: pink/red - add reagent C (Zn dust) if no color develops - negative: pink/red, clear: positive
72
urea hydrolysis
- detect the presence of enzyme urease (degrades urea to ammonia) - phenol red (reagent) - positive: pink - negative: orange
73
tryptophan degradation
- determines presence of enzyme tryphtophanase (converts tryptophan into indole and pyruvic acid) - reagent: Kovac's reagent - positive: red layer at top
74
gelatin
- detects presence of gelatinase (degrade gelatin from solid to liquid) - positive: liquid after ice bath - negative: solid
75
O2 requirements
- thyglycolate test - obligate aerobes: growth at top - obligate anaerobes: growth at bottom - facultative anaerobes: heavy growth at top, throughout - aerotolerant anaerobes: equal growth - microaerophiles: growth in middle
76
motility
- determines if bacteria is motile - wet mount: look for movement under microscope - stab method: use needle and stab agar - motile: swim away from stab line - non-motile: only grow along stab line
77
oxidase test
- indicates the presence of cytochrome oxidase (enzyme) - Tryptic soy agar plate - Becton Dickinson (oxidase reagent dropper) - positive: purple under 30 seconds
78
mannitol salt agar
- selective and differential - if significant growth- Staphylococcus because it can handle high salt (gram-positive) - plate from red to yellow
79
levine EMB agar
- selective and differential - purple: bacteria can ferment sucrose and lactose - non-fermenters: normal colored colonies - positive: dark red/brown-green - gram-negative

Microbiology (3 decks)

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