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ANS 302: Veterinary Microbiology > Bacterial Cell Structure > Flashcards

Bacterial Cell Structure Flashcards

(127 cards)

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1
Q

What are the 3 ways bacteria are classified morphologically?

A
  1. Shape.
  2. Arrangement.
  3. Size.
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2
Q

What are the main shapes of bacteria (scientific terms)?

A
  1. Coccus.
  2. Coccobacillus.
  3. Bacillus.
  4. Vibrio.
  5. Spirillum.
  6. Spirochete.
  7. Pleomorphic.
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3
Q

In what 2 ways are the arrangement of bacteria described?

A
  1. Plane of division.
  2. Separation or not.
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4
Q

What is the shape of a coccus/cocci bacteria?

A

Sphere-shaped.

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5
Q

What is the shape of a streptococci bacteria?

A

Chain.

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6
Q

What is the shape of a staphylococci bacteria?

A

Grape-cluster.

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7
Q

What is the shape of a diplococcus/diplococci bacteria?

A

A pair.

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8
Q

What is the shape of a tetrad cocci bacteria?

A

4 in a square.

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9
Q

What is the shape of a sarcinae cocci bacteria?

A

Cubic configuration of 8.

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10
Q

What is the shape of a bacillus/bacilli bacteria?

A

Rod.

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11
Q

What is the shape of a coccobacillus bacteria?

A

Short rod.

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12
Q

What is the shape of a vibrio bacteria?

A

Comma-shaped.

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13
Q

What is the shape of a spirillum bacteria?

A

Rigid helix.

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14
Q

What is the shape of a spirochete bacteria?

A

Tight spiral.

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15
Q

What is the shape of mycelium?

A

Network of long, multinucleated filaments.

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16
Q

What is the shape of pleomorphic bacteria?

A

Variable in shape.

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17
Q

What is the smallest bacteria and what is its size?

A
  1. Mycoplasma.
  2. 0.3 um.
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18
Q

What is the size of an average rod bacteria?

A

1.1-1.5 um x 2-6 um.
ex: E.coli

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19
Q

What is a very large bacteria?

A

600-800 um.
ex: Epulopiscium fishelsoni

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20
Q

What is the protoplast?

A

The bacterial plasma membrane and everything within it.

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21
Q

What is the cytoplasm?

A

The gel material bound by the plasma membrane.

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22
Q

What is the cytosol?

A

The liquid portion of the cytoplasm.

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23
Q

What are inclusions?

A

Storage granules for organic or inorganic material for future use. Can provide the bacteria with metabolic abilities.
*Some are enclosed in a single-layer membrane.

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24
Q

What is the ribosome?

A

A complex protein/RNA structure that is the site of protein synthesis.

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25
What is the nucleoid?
A non-membrane bound (w/exceptions) organelle where the chromosome and associated proteins are found in bacteria.
26
How is DNA stored in bacteria?
1 closed, circular, 2x stranded DNA molecule that is supercoiled.
27
What is a plasmid?
Extrachromosomal DNA found in archaea, bacteria, and some fungi.
28
What shape is a plasmid?
Small, closed, circular DNA molecule.
29
When are plasmids inherited?
During cell division. *Exists and replicates independently of chromosome.
30
Why are plasmids important?
They normally give the host a selective advantage.
31
What is the one cell structure required for all living organisms?
A plasma membrane.
32
What are the functions of the plasma membrane?
1. Act as a selectively permeable membrane. 2. Encompass the cytoplasm. 3. Interact with the external environment.
33
How does the plasma membrane interact with the external environment?
1. Through receptors for detecting and responding to chemicals. 2. Metabolic processes. 3. Transport systems.
34
What is the plasma membrane made of?
A phospholipid bilayer intermingled with proteins. *Compared to a mosaic.
35
What is unique about the phospholipid bilayer?
It is amphipathic due to having a hydrophilic head and a hydrophobic tail.
36
What are the 2 types of membrane proteins?
1. Integral. 2. Peripheral.
37
What are the characteristics of an integral protein?
1. Amphipathic, due to being embedded in the membrane. 2. Carry out important functions.
38
What are the characteristics of a peripheral protein?
1. Easily removed. 2. Loosely connected to the membrane.
39
What are the functions of the bacteria cell wall?
1. Maintain shape of bacterium. 2. Helps protect from toxic materials. 3. Helps protect from osmotic lysis. 4. May contribute to pathogenicity.
40
What is the structure of gram positive bacteria?
1. Thick peptidoglycan cell wall. 2. Plasma membrane.
41
What is the structure of a gram negative bacteria?
1. Outer membrane. 2. Thin peptidoglycan cell wall. 3. Plasma membrane.
42
What is peptidoglycan?
A rigid structure composed of a mesh-like polymer of two alternating sugars that form long chains. Lies just outside the cell plasma membrane.
43
What is peptidoglycan a target for?
Antibiotics.
44
What are the 2 sugars in peptidoglycan?
1. N-acetyl glucosamine (NAG). 2. N-acetyl muramic acid (NAM).
45
What links NAM and NAG?
1. The peptide L-Ala-D-Glu-L-Lys-D-Ala. 2. Pentaglycine crosslinking.
46
What do peptidoglycan chains actually look like?
Tubes.
47
What color do Gram positive bacteria stain? Why?
1. Blue or purple. 2. When the thick peptidoglycan wall is dried out, the crystal violet-iodine complexes are trapped.
48
What color do Gram negative bacteria stain? Why?
1. Pink or red. 2. Due to the outer membrane sitting above the thin peptidoglycan wall, when the peptidoglycan wall is dried out, crystal violet-iodine complex can be flushed out.
49
Why is crystal violet readily absorbed into the bacteria?
Bacteria have a negative charge, while crystal violet has a positive charge.
50
What is the periplasmic space?
Space that lies between the plasma membrane and cell wall. *Smaller in Gram positive bacteria.
51
What does the cell wall of Gram positive bacteria contain?
1. Peptidoglycan. 2. Teichoic acid. 3. Lipoteichoic acid.
52
What are the 3 functions of teichoic acid and lipoteichoic acid?
1. Help maintain cell envelope. 2. May bind to host cells. 3. Protect cell from environmental substances.
53
Where does teichoic acid end?
In the peptidoglycan.
54
Where does the lipoteichoic acid end?
In the plasma membrane.
55
What does the outer membrane of a Gram negative cell contain?
1. Lipids. 2. Lipopolysaccharide. 3. Braun's lipoprotein.
56
What is the function of Braun's lipoprotein?
Anchors the peptidoglycan to the outer membrane.
57
How much cell volume does the periplasmic space account for in Gram negative cells?
20-40%.
58
What does the periplasmic space contain?
Periplasm (hydrolytic enzymes, transport proteins, and other proteins).
59
What are the 3 parts of lipopolysaccharide (LPS)?
1. Lipid A. 2. Core polysaccharide. 3. O Side chain/O antigen.
60
Why is LPS important?
1. May contribute to biofilm formation. 2. May contribute to surface attachment. 3. Creates a permeability barrier.
61
What are the characteristics of lipid A?
1. Anchored in the outer membrane. 2. Acts as an endotoxin (not toxic to all hosts). 3. Helps stabilize the outer membrane structure.
62
What is the main characteristic of the core polysaccharide?
Contributes to negative charge on the cell surface.
63
What is the characteristics of the O Antigen?
1. Protection from host defense. 2. Allows for identification of the strain.
64
How can knowledge of cell wall structure help in future endeavors?
1. Knowing which antibiotics to use. 2. Being able to use the structure to your advantage.
65
What are the outermost layers of the cell envelope?
1. Capsule or slime layer. 2. S layer.
66
What is the function of the capsule or slime layer and the S layer?
Aid in attachment to solid surfaces. ex: Biofilms.
67
What are the characteristics of the capsule?
1. Tightly packed. 2. Thick glycocalyx. 3. Organized.
68
What does the capsule protect bacteria from?
1. Desiccation. 2. Viruses. 3. Detergents. 4. Phagocytosis.
69
What does the capsule contribute to?
Contributes to virulence.
70
What are the characteristics of the slime layer?
1. Loose. 2. Thin glycocalyx. 3. Unorganized.
71
What does the slime layer promote?
Adherence to surfaces.
72
What does the slime layer protect cells from?
Drying out. Also traps nutrients.
73
What is the slime layer important in?
Biofilm production.
74
What is the S layer (crystalline bacterial cell surface layer)?
Regularly structured layers of protein or glycoprotein that spontaneously self-assembles. *Potential use in nanotechnology.
75
How does the S-layer form in Gram negative bacteria?
Adheres to outer membrane.
76
How does the S-layer form in Gram positive bacteria?
Associated with the peptidoglycan surface.
77
What does the S-layer protect the bacteria from?
1. Ion fluctuations. 2. pH fluctuations. 3. Predation. 4. Osmotic stress. 5. Enzymes.
78
What does the S-layer help maintain?
Rigidity and shape.
79
What does the S-layer protect against?
Host defenses.
80
What does the S-layer promote?
Adhesion to surfaces.
81
What is the function of structures that extend beyond the cell envelope?
1. Protection. 2. Attachment to surfaces. 3. Cell movement. 4. Horizontal gene transfer.
82
What are the characteristics of fimbriae/pili?
1. Thin. 2. Short. 3. Hairlike. 4. Proteinaceous.
83
How many fimbriae/pili can exist on one cell?
Up to 1,000.
84
What is the function of fimbriae/pili?
To mediate attachment to surfaces. *Some are involved in movement.
85
What are the characteristics of sex pili?
1. Long. 2. Thick.
86
How many sex pili can exist on one cell?
1-10.
87
What are the functions of sex pili?
1. Sharing of genetic information. 2. Conjugation.
88
What are the characteristics of flagella?
1. Threadlike. 2. Rigid.
89
Where are the genes for the formation of sex pili found?
On plasmids.
90
What are the functions of flagella?
1. Attachment to surfaces. 2. Motility and swarming behavior. *May contribute to virulence.
91
What are the 3 parts of the ultrastructure of the flagella?
1. Filament. 2. Hook. 3. Basal body.
92
What is the function of the filament?
To act as the guide (tail portion).
93
What is the function of the hook?
Turning.
94
What is the function of the basal body?
Attachment to the cell wall.
95
Which bacteria has a more complex flagellar attachment?
Gram negative. More points of attachment due to structure of cell membrane.
96
What is monotrichous flagella distribution?
One flagellum.
97
What is amphitricous flagella distribution?
One flagellum at each end.
98
What is lophotrichous flagella distribution?
Cluster of flagella at one or both ends.
99
What is peritrichous flagella distribution?
Spread over the entire surface of the cell.
100
What are the types of motility?
1. Gliding motility. 2. Twitching motility. 3. Spirochete motility. 4. Flagellar motility.
101
What is chemotaxis?
Moving towards chemical attractants, such as nutrients, or away from harmful substances.
102
What other stimuli do bacteria move in response to?
1. Gravity. 2. Light. 3. Oxygen. 4. Temperature. 5. Osmotic pressure.
103
What are flagella compared to?
Propellers, due to the way they rotate.
104
How many revolutions per second does a flagella turn at?
Up to 1100.
105
What does counterclockwise (CCW) rotation cause?
Forward motion/run.
106
What does clockwise (CW) rotation cause?
The cell to stop and tumble.
107
How is spirochete bacteria motility unique?
Multiple flagella form an axial fibril that winds around the cell.
108
Where is the flagella located on spirochete bacteria?
In the periplasmic space, inside the outer sheath.
109
What kind of motion does the corkscrew shape of spirochete bacteria allow for?
Jittery flexing and spinning.
110
What cellular structure is involved in twitching motions?
Pili on the ends of cells.
111
How is twitching motion described?
Intermittent, short, jerky.
112
When is twitching employed?
When cells are in contact with surfaces and each other.
113
What cell covering is used during the gliding motion?
Slime layer.
114
How is gliding motion described?
Smooth.
115
What is an endospore?
A complex, dormant structure that is formed by some bacteria.
116
What triggers endospore formation?
1. Heat. 2. Desiccation. 3. Nutrient lack. 4. Radiation. 5. Chemicals.
117
Why are endospores formed?
To guarantee the survival of the bacteria.
118
How long do the endospores normally last?
50-100 years, sometimes longer.
119
What is the outermost layer of the endospore?
A thin layer called the endosporium.
120
What is the thickest layer of an endospore?
The spore coat.
121
What is the cortex composed of?
The peptidoglycan. *Beneath the coat.
122
What does the core contain?
The nucleoid and the ribosome.
123
What is sporulation?
The process of endospore formation.
124
How rapidly does sporulation occur?
In hours, up to 10 hours.
125
What happens once the environment is safe?
Germination.
126
What kind of bacteria undergo sporulation?
Gram positive.
127
What 2 species of bacteria most commonly undergo sporulation?
1. Bacillus. 2. Clostridium.

ANS 302: Veterinary Microbiology (16 decks)

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