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ANS 302: Veterinary Microbiology > Bacterial Cell Structure > Flashcards

Bacterial Cell Structure Flashcards

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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
Q

What is the nucleoid?

A

A non-membrane bound (w/exceptions) organelle where the chromosome and associated proteins are found in bacteria.

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26
Q

How is DNA stored in bacteria?

A

1 closed, circular, 2x stranded DNA molecule that is supercoiled.

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27
Q

What is a plasmid?

A

Extrachromosomal DNA found in archaea, bacteria, and some fungi.

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28
Q

What shape is a plasmid?

A

Small, closed, circular DNA molecule.

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29
Q

When are plasmids inherited?

A

During cell division.
*Exists and replicates independently of chromosome.

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30
Q

Why are plasmids important?

A

They normally give the host a selective advantage.

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31
Q

What is the one cell structure required for all living organisms?

A

A plasma membrane.

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32
Q

What are the functions of the plasma membrane?

A
  1. Act as a selectively permeable membrane.
  2. Encompass the cytoplasm.
  3. Interact with the external environment.
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33
Q

How does the plasma membrane interact with the external environment?

A
  1. Through receptors for detecting and responding to chemicals.
  2. Metabolic processes.
  3. Transport systems.
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34
Q

What is the plasma membrane made of?

A

A phospholipid bilayer intermingled with proteins.
*Compared to a mosaic.

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35
Q

What is unique about the phospholipid bilayer?

A

It is amphipathic due to having a hydrophilic head and a hydrophobic tail.

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36
Q

What are the 2 types of membrane proteins?

A
  1. Integral.
  2. Peripheral.
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37
Q

What are the characteristics of an integral protein?

A
  1. Amphipathic, due to being embedded in the membrane.
  2. Carry out important functions.
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38
Q

What are the characteristics of a peripheral protein?

A
  1. Easily removed.
  2. Loosely connected to the membrane.
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39
Q

What are the functions of the bacteria cell wall?

A
  1. Maintain shape of bacterium.
  2. Helps protect from toxic materials.
  3. Helps protect from osmotic lysis.
  4. May contribute to pathogenicity.
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40
Q

What is the structure of gram positive bacteria?

A
  1. Thick peptidoglycan cell wall.
  2. Plasma membrane.
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41
Q

What is the structure of a gram negative bacteria?

A
  1. Outer membrane.
  2. Thin peptidoglycan cell wall.
  3. Plasma membrane.
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42
Q

What is peptidoglycan?

A

A rigid structure composed of a mesh-like polymer of two alternating sugars that form long chains. Lies just outside the cell plasma membrane.

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43
Q

What is peptidoglycan a target for?

A

Antibiotics.

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44
Q

What are the 2 sugars in peptidoglycan?

A
  1. N-acetyl glucosamine (NAG).
  2. N-acetyl muramic acid (NAM).
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45
Q

What links NAM and NAG?

A
  1. The peptide L-Ala-D-Glu-L-Lys-D-Ala.
  2. Pentaglycine crosslinking.
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46
Q

What do peptidoglycan chains actually look like?

A

Tubes.

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47
Q

What color do Gram positive bacteria stain? Why?

A
  1. Blue or purple.
  2. When the thick peptidoglycan wall is dried out, the crystal violet-iodine complexes are trapped.
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48
Q

What color do Gram negative bacteria stain? Why?

A
  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.
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49
Q

Why is crystal violet readily absorbed into the bacteria?

A

Bacteria have a negative charge, while crystal violet has a positive charge.

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50
Q

What is the periplasmic space?

A

Space that lies between the plasma membrane and cell wall.
*Smaller in Gram positive bacteria.

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51
Q

What does the cell wall of Gram positive bacteria contain?

A
  1. Peptidoglycan.
  2. Teichoic acid.
  3. Lipoteichoic acid.
52
Q

What are the 3 functions of teichoic acid and lipoteichoic acid?

A
  1. Help maintain cell envelope.
  2. May bind to host cells.
  3. Protect cell from environmental substances.
53
Q

Where does teichoic acid end?

A

In the peptidoglycan.

54
Q

Where does the lipoteichoic acid end?

A

In the plasma membrane.

55
Q

What does the outer membrane of a Gram negative cell contain?

A
  1. Lipids.
  2. Lipopolysaccharide.
  3. Braun’s lipoprotein.
56
Q

What is the function of Braun’s lipoprotein?

A

Anchors the peptidoglycan to the outer membrane.

57
Q

How much cell volume does the periplasmic space account for in Gram negative cells?

A

20-40%.

58
Q

What does the periplasmic space contain?

A

Periplasm (hydrolytic enzymes, transport proteins, and other proteins).

59
Q

What are the 3 parts of lipopolysaccharide (LPS)?

A
  1. Lipid A.
  2. Core polysaccharide.
  3. O Side chain/O antigen.
60
Q

Why is LPS important?

A
  1. May contribute to biofilm formation.
  2. May contribute to surface attachment.
  3. Creates a permeability barrier.
61
Q

What are the characteristics of lipid A?

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
Q

What is the main characteristic of the core polysaccharide?

A

Contributes to negative charge on the cell surface.

63
Q

What is the characteristics of the O Antigen?

A
  1. Protection from host defense.
  2. Allows for identification of the strain.
64
Q

How can knowledge of cell wall structure help in future endeavors?

A
  1. Knowing which antibiotics to use.
  2. Being able to use the structure to your advantage.
65
Q

What are the outermost layers of the cell envelope?

A
  1. Capsule or slime layer.
  2. S layer.
66
Q

What is the function of the capsule or slime layer and the S layer?

A

Aid in attachment to solid surfaces.
ex: Biofilms.

67
Q

What are the characteristics of the capsule?

A
  1. Tightly packed.
  2. Thick glycocalyx.
  3. Organized.
68
Q

What does the capsule protect bacteria from?

A
  1. Desiccation.
  2. Viruses.
  3. Detergents.
  4. Phagocytosis.
69
Q

What does the capsule contribute to?

A

Contributes to virulence.

70
Q

What are the characteristics of the slime layer?

A
  1. Loose.
  2. Thin glycocalyx.
  3. Unorganized.
71
Q

What does the slime layer promote?

A

Adherence to surfaces.

72
Q

What does the slime layer protect cells from?

A

Drying out. Also traps nutrients.

73
Q

What is the slime layer important in?

A

Biofilm production.

74
Q

What is the S layer (crystalline bacterial cell surface layer)?

A

Regularly structured layers of protein or glycoprotein that spontaneously self-assembles.
*Potential use in nanotechnology.

75
Q

How does the S-layer form in Gram negative bacteria?

A

Adheres to outer membrane.

76
Q

How does the S-layer form in Gram positive bacteria?

A

Associated with the peptidoglycan surface.

77
Q

What does the S-layer protect the bacteria from?

A
  1. Ion fluctuations.
  2. pH fluctuations.
  3. Predation.
  4. Osmotic stress.
  5. Enzymes.
78
Q

What does the S-layer help maintain?

A

Rigidity and shape.

79
Q

What does the S-layer protect against?

A

Host defenses.

80
Q

What does the S-layer promote?

A

Adhesion to surfaces.

81
Q

What is the function of structures that extend beyond the cell envelope?

A
  1. Protection.
  2. Attachment to surfaces.
  3. Cell movement.
  4. Horizontal gene transfer.
82
Q

What are the characteristics of fimbriae/pili?

A
  1. Thin.
  2. Short.
  3. Hairlike.
  4. Proteinaceous.
83
Q

How many fimbriae/pili can exist on one cell?

A

Up to 1,000.

84
Q

What is the function of fimbriae/pili?

A

To mediate attachment to surfaces.
*Some are involved in movement.

85
Q

What are the characteristics of sex pili?

A
  1. Long.
  2. Thick.
86
Q

How many sex pili can exist on one cell?

A

1-10.

87
Q

What are the functions of sex pili?

A
  1. Sharing of genetic information.
  2. Conjugation.
88
Q

What are the characteristics of flagella?

A
  1. Threadlike.
  2. Rigid.
89
Q

Where are the genes for the formation of sex pili found?

A

On plasmids.

90
Q

What are the functions of flagella?

A
  1. Attachment to surfaces.
  2. Motility and swarming behavior.
    *May contribute to virulence.
91
Q

What are the 3 parts of the ultrastructure of the flagella?

A
  1. Filament.
  2. Hook.
  3. Basal body.
92
Q

What is the function of the filament?

A

To act as the guide (tail portion).

93
Q

What is the function of the hook?

A

Turning.

94
Q

What is the function of the basal body?

A

Attachment to the cell wall.

95
Q

Which bacteria has a more complex flagellar attachment?

A

Gram negative. More points of attachment due to structure of cell membrane.

96
Q

What is monotrichous flagella distribution?

A

One flagellum.

97
Q

What is amphitricous flagella distribution?

A

One flagellum at each end.

98
Q

What is lophotrichous flagella distribution?

A

Cluster of flagella at one or both ends.

99
Q

What is peritrichous flagella distribution?

A

Spread over the entire surface of the cell.

100
Q

What are the types of motility?

A
  1. Gliding motility.
  2. Twitching motility.
  3. Spirochete motility.
  4. Flagellar motility.
101
Q

What is chemotaxis?

A

Moving towards chemical attractants, such as nutrients, or away from harmful substances.

102
Q

What other stimuli do bacteria move in response to?

A
  1. Gravity.
  2. Light.
  3. Oxygen.
  4. Temperature.
  5. Osmotic pressure.
103
Q

What are flagella compared to?

A

Propellers, due to the way they rotate.

104
Q

How many revolutions per second does a flagella turn at?

A

Up to 1100.

105
Q

What does counterclockwise (CCW) rotation cause?

A

Forward motion/run.

106
Q

What does clockwise (CW) rotation cause?

A

The cell to stop and tumble.

107
Q

How is spirochete bacteria motility unique?

A

Multiple flagella form an axial fibril that winds around the cell.

108
Q

Where is the flagella located on spirochete bacteria?

A

In the periplasmic space, inside the outer sheath.

109
Q

What kind of motion does the corkscrew shape of spirochete bacteria allow for?

A

Jittery flexing and spinning.

110
Q

What cellular structure is involved in twitching motions?

A

Pili on the ends of cells.

111
Q

How is twitching motion described?

A

Intermittent, short, jerky.

112
Q

When is twitching employed?

A

When cells are in contact with surfaces and each other.

113
Q

What cell covering is used during the gliding motion?

A

Slime layer.

114
Q

How is gliding motion described?

A

Smooth.

115
Q

What is an endospore?

A

A complex, dormant structure that is formed by some bacteria.

116
Q

What triggers endospore formation?

A
  1. Heat.
  2. Desiccation.
  3. Nutrient lack.
  4. Radiation.
  5. Chemicals.
117
Q

Why are endospores formed?

A

To guarantee the survival of the bacteria.

118
Q

How long do the endospores normally last?

A

50-100 years, sometimes longer.

119
Q

What is the outermost layer of the endospore?

A

A thin layer called the endosporium.

120
Q

What is the thickest layer of an endospore?

A

The spore coat.

121
Q

What is the cortex composed of?

A

The peptidoglycan.
*Beneath the coat.

122
Q

What does the core contain?

A

The nucleoid and the ribosome.

123
Q

What is sporulation?

A

The process of endospore formation.

124
Q

How rapidly does sporulation occur?

A

In hours, up to 10 hours.

125
Q

What happens once the environment is safe?

A

Germination.

126
Q

What kind of bacteria undergo sporulation?

A

Gram positive.

127
Q

What 2 species of bacteria most commonly undergo sporulation?

A
  1. Bacillus.
  2. Clostridium.

ANS 302: Veterinary Microbiology (4 decks)

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