Biology 207 > Lab Exam 1 > Flashcards

Lab Exam 1 Flashcards

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1
Q

Phase contrast microscopy

A

Used to produce high-contrast images of transparent/colorless specimens (40x)

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2
Q

Oil immersion

A

Used to enhance the resolution of the specimen with 100x. The increased refractive index of the oil increases the numerical aperture of the microscope giving a better image

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3
Q

How long should you wait for the loop to cool after sterilizing?

A

20 seonds

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4
Q

What does smearing and staining do for cells that are small?

A

Cells that are too small to be observed at high power are smeared and stained. It immobilizes the cells so they can be viewed properly with oil immersion

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5
Q

What type of solution did we use for the pepper infusion?

A

Saline

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6
Q

What were the two growth methods for pepper bacteria?

A

Incubation
Agar plating

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7
Q

Which cell layer is thicker in gram positive cells than gram negative cells?

A

Peptidoglycan

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8
Q

What are the two types of acid that connect peptidoglycan layers?

A

Teichoic acid
Lipoteichoic acid

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9
Q

What layer is below the peptidoglycan layer in gram-positive cells?

A

Periplasmic space

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10
Q

What layer is below the periplasmic space in gram-positive cells?

A

Plasma membrane and integral membrane proteins

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11
Q

What is the upper most layer of gram negative cells?

A

O-specific side chains

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12
Q

What part of the cell do O-specific side chains connect to in gram-negative cells?

A

The lipopolysaccharide layer of the outer membrane

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13
Q

What are porins?

A

Transmembrane proteins that connect the periplasmic space to the outer membrane and lipopolysaccharide layer

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14
Q

Where is the peptidoglycan located in gram negative cells?

A

Periplasmic space

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15
Q

Where are Broun’s lipoproteins located in gram-negative cells?

A

Between peptidoglycan and the lower layer of the outer membrane

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16
Q

How long do we stain with crystal violet?

A

60 seconds, then rinse with DI water

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17
Q

Chemical properties of crystal violet stain

A

CV in aqueous solution is CV+ and Cl- ions. The CV+ ions penetrate the bacterial cell wall of + and - cells through its interaction with positively charged ions of d-side chains of teichoic acid in peptidoglycan

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18
Q

How long do we stain with iodine?

A

45 seconds, then rinse with DI water

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19
Q

Chemical properties of iodine stain

A

I- or I3- interacts with the CV+ ions that have penetrated the cell walls, forming large CVI complexes.

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20
Q

How long do we stain with decolorizing 95% ethanol?

A

5-10 seconds, then rinse with DI water

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21
Q

Chemical properties of decolorizing 95% ethanol

A

Ethanol interactions with + and - lipids in the outer membrane.
+: the thick peptidoglycan layer becomes dehydrated, trapping the CVI complex in the membrane
-: the outer membrane is lost. The thin peptidoglycan layer becomes leaky and loses the CVI complex

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22
Q

How long do we stain with safranin?

A

60 seconds, then rinse with DI water

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23
Q

Chemical properties of safranin

A

Positively charged safranin acts as the counter stain that colors only the de-stained gram-negative cells

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24
Q

What happens to non-viable gram-positive cells?

A

They are in late stationary phase, so they will also stain pink. The peptidoglycan layer begins to thin out or decompose

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25
Gram-variable cells
Some bacteria (rare) have cells wall composition that changes based on the host environment, making identifying them with a gram stain challenging
26
3 examples of gram-variable cells
Mycobacterium Bacillus Colostridium
27
3 types of nutritional media
Natural, chemically defined, complex (semi-synthetic)
28
Definition, pros, cons of chemically defined media
Defined composition (fractions) of nutrients Best nutrient consistency between batches Difficult to make, need to know nutrient requirements of microbe
29
Definition, pros, cons of natural media
Natural source of microbes (niche) Best chance for microbe to grow Hard to attain
30
Definition, pros, cons of complex (semi-synthetic) media
Mix of natural and defined chemicals Inexpensive, nutrient rich, little knowledge needed Unknown chemical composition
31
3 consistencies of medias
Liquid, solid, semi-solid
32
Form, use, and disadvantages of liquid media
broth cultures growing a large number of microbial units can't separate individual cells
33
Form, use, and disadvantages of solid medias
agar plates, plates to get single, unified colonies, to identify species in mixed cultures limited surface area for growth
34
Form, use, and disadvantages of semi-solid media
plates, slants, deep to observe motility or grow microbes in a gradient of oxygen hard to see specific observation
35
3 types of usage types for media
selection, enrichment, differentiation
36
purpose, pro/con of selection media
only allows certain organisms to growth with the rest struggle or die due to strict nutrient requirements idea for growing organisms with a selectable trait
37
purpose, pro/con of enrichment media
multiple organisms can grow but some have greater advantage isolate rare microbes in a mix more common in number, used when selection isn't possible
38
purpose, pro/con of differentiation media
organisms that can grow will demonstrate a phenotype based on metabolic activity allows for the selection of microbes that have desired traits
39
3 types of sterilization and disposal
Autoclave, filtration, irradiation
40
Usage of autoclaves
media contains heat stable amino acids
41
Usage of filtration
Media contains heat sensitive amino acids (ex. phenylalanine)
42
Usage of irradiation
Large quantities of heat-sensitive media need to be sterilized, good for sterilizing working areas like laminar hoods
43
What specific type of bacteria was the Winogradsky column designed to study?
Chemoautotrophs (CO2 fixing bacteria)
44
What are the four components of a Winogradsky column?
Mud, sulfate, salt, cellulose Grown under UV light
45
Layers of Winogradsky column from top to bottom
Air Liquid with cyanobacteria and algae Solid: non-sulfur photosynthetic bacteria, purple photosynthetic bacteria, green photosynthetic bacteria, mud
46
What kind of growth is promoted when incubating the Winogradsky column at room temperature in foil?
Anaerobic growth
47
Pathway of air from Bunsen burner in aseptic technique
Goes up and then down in circles parallel to the burner
48
Settings of pasteurization for pepper infusion
65 C water bath for 10 minutes
49
What kind of growth does Tryptic Soy Agar promote?
Prokaryotes Used for pepper infusion
50
What is an endospore?
Non-reproductive structures released by bacteria when under stress (nutrient deprivation, overpopulation) to ensure the survival of the bacterium
51
Contents of spores
DNA, ribosome, cytoplasmic content from the cell
52
What is dormant about endospores?
Metabolism
53
What are endospores very resistant to?
Heat, desiccation, UV light, chemical disinfectants
54
What happens to the bacterial cell after it releases its endospore?
It dies
55
Spore staining method
Put on malachite green and steam for 7 minutes Washing with water decolorizes the cell but the endospore remains green Counterstain with safranin for 30 seconds Use oil immersion on 100x
56
What is the purpose of steaming the malachite green dye?
Heat/steam loosens the endospore coat and allows the stain to permeate
57
What is microbial motility?
The use of metabolic energy (ATP) which allows the cell to move independently
58
Structure and function of rotary flagella
10 micro m from cell surface, hook connects to the outer membrane of the cell Prokaryotes that are motile move around using rotary flagella
59
Monotrichous flagellum
1 flagellum
60
Amphitrichous flagellum
2 flagella on opposite ends
61
Lophotrichous flagellum
Multiple flagella grouped together in one group
62
Peritrichous flagellum
Many flagella scattered on the surface of the cell
63
Water movement
Bacterial cells moving in the drop all at once in the same directions (waves, not motility)
64
Brownian motion
Random and erratic movement of cells in the droplet fluid caused by bombardment with other particles (spinning, not motility)
65
Motility
Not random but directional movement of a cell (often slow)
66
What does the ratio of endospores to exospores tell us?
Cells only release endospores when they die, so cells closer to the edge (younger) will have endospores and cells closer to the center (older) will have exospores
67
What is chemotaxis?
The movement of microorganisms towards a favorable enviornment
68
Explain how a Mot protein workds
Found at the base of the cytoplasmic membrane of bacteria with flagella, has two parts that generate torque that changes the direction of the flagella so the cell can move
Biology 207
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