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Microbiology > Anatomy of the Bacterial Cell > Flashcards

Anatomy of the Bacterial Cell Flashcards

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1
Q

How would you describe a bacterial cell wall?

A

A complex, semi-rigid structure responsible for cell shape

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2
Q

The bacterial cell wall acts as an attachment point for the…

A

Flagella

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3
Q

The major component of bacterial cell walls is…

A

Peptidoglycan

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4
Q

How does the cell wall prevent the osmotic lysis of a bacterial cell?

A

The interior of the cell wall is at a higher pressure than it’s surrounding environment, without the cell wall the bacteria would pop. In a hypotonic solution, water moves into the cell. If the cell wall is strong, it contains the swelling. If the cell wall is weak or damaged, the cell bursts, osmotic lysis.

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5
Q

What two sugars is peptidoglycan composed of?

A

N-acetylglucosamine and N-acetylmuramic acid

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6
Q

What is an isotonic solution?

A

A medium in which the overall concentration of solutes equals that found inside the cell

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7
Q

What is a hypotonic solution?

A

A hypotonic solution outside the cell is a medium whose concentration of solutes is lower than that inside the cell

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8
Q

What is a hypertonic solution?

A

A hypertonic solution is a medium having a higher concentration of solutes than inside the cell has

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9
Q

How do N-acetylglucosamine and N-acetylmuramic acid make the cell wall?

A

The pair form repeating disaccharides which create a polymer

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10
Q

Name two amino acids that form cross links between the disaccharide polymer chains.

A

Lysine and diaminopimelic acid (DAP)

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11
Q

What is special with the amino acids that make up the cell wall?

A

They are alternating between the L- and D- forms

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12
Q

Why are alternating L- and D- amino acid forms unique?

A

Usually only the L-form of amino acids are used in proteins in nature

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13
Q

How are N-acetylglucosamine and N-acetylmuramic acid linked to each other?

A

By a beta, 1-4 linkage glycosidic bond

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14
Q

How does the enzyme lysozyme damage cell walls?

A

By breaking the beta 1-4 linkage connecting the disaccharide

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15
Q

How are the sugar chains cross linked?

A

By amino acids connecting N-acetylmuramic acid

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16
Q

The more cross linking, the greater the…

A

Rigidity

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17
Q

What is DAP?

A

An amino acid found in the peptide linkages between NAM and NAG. Stands for diaminopimelic acid

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18
Q

How much of the cell wall does peptidoglycan make up in gram positive bacteria?

A

Up to 25nm

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19
Q

How much of the cell wall does peptidoglycan make up in gram negative bacteria?

A

2-5nm

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20
Q

In gram negative bacteria, the NAG-NAM chains are…

A

Directly linked

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21
Q

In gram positive bacteria, the NAG-NAM peptide chains are…

A

Linked by a pentapeptide bridge

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22
Q

B lactam antibiotics inhibit…

A

Transpeptidase enzymes which catalyses the formation of the final bond between two peptide chains

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23
Q

Give two examples of B lactam antibiotics

A

Penicillin and cephalosporins

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24
Q

Staphylococcus is

A

Gram positive

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25
Q

Bacillus is

A

Gram positive

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26
Q

Clostridium is

A

Gram positive

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27
Q

Listeria is

A

Gram positive

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28
Q

Corynebacterium is

A

Gram positive

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29
Q

90% of the cell wall is made up of peptidoglycan in a…

A

Gram positive bacterium

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30
Q

Teichoic acids are found in…

A

Gram positive bacteria

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31
Q

What are the teichoic acids that span the whole cell wall and link to the plasma membrane called

A

Lipoteichoic acid

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32
Q

What are the teichoic acids associated with the peptidoglycan called

A

Wall teichoic acid

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33
Q

Teichoic acids usually bind to

A

Sugars and D-alanine

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34
Q

Teichoic acids are polymers of

A

Glycerophosphate or ribitol phosphate

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35
Q

Roles of teichoic acids include

A

May bind and regulate the movement of cations due to -ve charge from phosphate groups. Structural stability. Provide antigenic specificity.

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36
Q

Five major parts of a gram positive bacterial cell wall:

A

Wall associated protein, wall teichoic acid, lipoteichoic acids, peptidoglycan and cytoplasmic membrane

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37
Q

What is the overall structure of a gram negative cell wall?

A

Outer membrane, periplasm and cytoplasmic membrane

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38
Q

Where is the peptidoglycan located in gram negative bacteria?

A

In the periplasmic space between the outer membrane and cytoplasmic membrane

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39
Q

Are there any teichoic acids in gram negative bacteria?

A

No homie!

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40
Q

How wide is the periplasm layer?

A

15nm

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41
Q

What does the periplasm contain?

A

Digestive enzymes and transporter proteins

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42
Q

The outer membrane is a…

A

Bilayer

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43
Q

What is the complement system?

A

The complement system consists of a number of small proteins found in the blood. The complement system is a part of the immune system that enhances (complements) the ability of antibodies and phagocytic cells to clear pathogens from an organism.

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44
Q

The outer membrane aids in evading…

A

Phagocytosis and complement

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45
Q

The outer membrane acts as a barrier to…

A

Certain antibiotics, penicillin, digestive enzymes

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46
Q

The outer membrane prevents molecules from the periplasm from being…

A

Lost

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47
Q

What are porins and where are they found?

A

Transporter proteins found in the outer membrane

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48
Q

What does LPS stand for?

A

Lipopolysaccharide

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49
Q

Where are lipopolysaccharides found?

A

In the outer membrane of a gram negative bacterium

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50
Q

What do lipopolysaccharides consist of?

A

Lipid A, the core polysaccharide and the O-polysaccharide

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51
Q

Three roles of the lipopolysaccharides present?

A

Stabilise the outer membrane
Increase the -ve charge
Protect from chemical attack

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52
Q

What is lipid A made of?

A

Phosphorylated glucosamine disaccharides decorated with multiple fatty acids

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53
Q

One of the main functions of LPS?

A

An endotoxin

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54
Q

An endotoxin is released when the bacteria dies and can cause symptoms to arise, such as..

A

Fever and vomitting

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55
Q

Does the gram negative bacteria have to be pathogenic to release endotoxins?

A

No

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56
Q

What is O-polysaccharide/O-antigen made of?

A

It’s a sugar polymer

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57
Q

What is the long O-polysaccharide chains in some gram negative outer membrane of the cell wall called?

A

Smooth LPS

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58
Q

What is the short O-antigen chain called?

A

Rough LPS

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59
Q

Some bacteria with a rough LPS are ____ suseptible to hydrophobic drugs

A

more

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60
Q

The O-polysaccharide functions as an

A

Antigen

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61
Q

The O-polysaccharide is useful for distinguishing between

A

different bacterial species and strains

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62
Q

What does E.coli O157:H7 cause?

A

Enterohemorrphagic fever

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63
Q

List the main components of a gram negative cell wall?

A

Outer membrane including proteins, the lipopolysaccharide - O-antigen, core polysaccharide and Lipid A. The periplasm layer which has the peptidoglycan and then the cytoplasmic membrane

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64
Q

Escherichia is…

A

Gram negative

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65
Q

Salmonella is

A

Gram negative

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66
Q

Pseudomonas is

A

Gram negative

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67
Q

Legionella is

A

Gram negative

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68
Q

Wolbachia is

A

Gram negative

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69
Q

Serratia is

A

Gram negative

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70
Q

Helicobacter is

A

Gram negative

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71
Q

Neisseria is

A

Gram negative

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72
Q

Klebsiella is

A

Gram negative

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73
Q

Who came up with gram positive/gram negative staining method?

A

Christian Gram in 1884

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74
Q

What stain is used first to treat the heat fixed cells?

A

Crystal violet

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75
Q

The primary stain is washed off and smear treated with a mordant. The mordant stain used is

A

Iodine

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76
Q

After primary stain and the mordant stain is added, the cells are washed with a de-colourising agent. The de-colourising agent is

A

Alcohol

77
Q

After the cells have been de-colourised. The smear is counterstained using

A

Safranin

78
Q

Mycobacterium cell walls are different in what way?

A

They contain a thin layer of peptidoglycan with a layer of mycolic acid

79
Q

What is a layer of mycolic acid?

A

Consists of a hydrophobic waxy lipid

80
Q

Why does gram stain not work for mycobacterium?

A

The dyes can not get through the waxy myolic acid layer

81
Q

What method is used to stain mycobacterium?

A

Acid-fast - carbonfuchsin binds to components in cystol

High affinity mycolic acids found in their cell membranes

82
Q

What are wall-less bacteria called?

A

Mollicutes such as mycoplasma

83
Q

What can mycoplasma cause?

A

Mycoplasma pneumonia

84
Q

What do mollicutes have that is unique?

A

They contain sterols in their plasma membrane

85
Q

What is the glycocalyx?

A

A viscous gelatinous polymer that surrounds the cell, secreted by most bacteria

86
Q

What is the glycocalyx composed of?

A

Polysaccharides and/or protein

87
Q

One type of glycocalyx is well organised and firmly attached to the cell. This is called

A

A capsule

88
Q

One type of glycocalyx is unorganised and loosely attached to the cell wall. This is called

A

A slime layer

89
Q

Capsules can be visualised. How?

A

By using negative staining

90
Q

How can the glycocalyx assist in the formation of biofilms?

A

They assist with attachment

91
Q

Steptococcus mutans can

A

adhere to teeth

92
Q

Vibrio cholera can

A

adhere to the small intestine

93
Q

Klebsiella can adhere/colonise

A

the respiratory tract

94
Q

What does Bacillus anthracis cause?

A

Anthrax

95
Q

What does Streptococcus pneumoniae cause?

A

Pneumonia

96
Q

How can capsules aid in the evasion of the immune system?

A

Capsule prevents phagocytosis

97
Q

What are fimbriae?

A

Short, hair like, proteinaceous appendage

98
Q

What protein makes fimbriae?

A

Curlin protein

99
Q

What type of bacteria have fimbriae?

A

Mostly gram negative, very few gram positive bacteria have fimbriae

100
Q

Where are fimbriae found?

A

At poles or along the entire length

101
Q

Fimbriae have a tendency to stick to…

A

each other as well as to surfaces

102
Q

How are fimbriae involved in biofilm formation?

A

Help bacteria adhere to epithelial surfaces of the body.

103
Q

E.coli when fimbriated adhere to the lining of the small intestine. What happens when fimbriae are absent?

A

Colonisation does not occur

104
Q

What are pili?

A

Hair like, proteinaceous appendages

105
Q

How do they differ from fimbriae?

A

Typically longer and only one/two found per cell

106
Q

What do sex pili do?

A

Facilitate genetic exchange between cells - conjugation

107
Q

What are the pili that are associated with motility called?

A

Type IV pili

108
Q

How do motility pili work?

A

Involves synthesis of pili until it reaches a surface then retraction of pili as it is dismantled

109
Q

There are two types of motility by the type iv pili, what are these called?

A

Twitching motility and gliding motility

110
Q

Describe twitching motion.

A

Short, jerky, intermittent motion

111
Q

Describe gliding motion

A

Smooth, continuous motion

112
Q

Give an example of a bacteria that uses gliding motion from its pilus.

A

Myxococcus

113
Q

What is the flagella?

A

A tail-like appendage

114
Q

Where is the flagella found? Gram pos or gram negative

A

It is found in both

115
Q

What is the main function of the flagella?

A

Locomotion - they are said to be motile and swim

116
Q

What is the shape of the flagella?

A

Helical

117
Q

What is the difference between flagella and fimbria/pilli?

A

The flagella is longer and thicker

118
Q

What are bacteria without a flagella called?

A

Atrichous

119
Q

Bacteria with flagella all over the surface are called?

A

Peritrichous

120
Q

If the flagella has only one flagella at one pole of the bacterium, it is said to be…

A

Monotrichous

121
Q

If there are multiple flagella at a pole it is said to be…

A

Lophotrichous

122
Q

If a bacteria is polar and has flagella at both ends it is known to be

A

Amphitrichous

123
Q

The flagella consists of which three parts?

A

The filament, the hook and the basal body

124
Q

The filament of a flagellum is composed of…

A

Flagellin (globular protein)

125
Q

The flagellin is unique to the bacteria, how is this an advantage?

A

Useful in identifying the bacteria

126
Q

The flagellin is arranged as…

A

Chains, they interwine to form a hollow tube

127
Q

The filament of a flagellum is not generally covered with a membrane, why is this key?

A

Because eukaryotic flagella are covered with a membrane

128
Q

What is the hook in a flagella?

A

The hook is the connecting region between the filament and the basal body

129
Q

The hook acts as an…

A

Universal joint

130
Q

The basal body of the flagella serves what purpose?

A

Anchors the flagella to the cell wall and plasma membrane

131
Q

How does the basal body allow the flagella to move?

A

It serves as the motor allowing the flagella to move

132
Q

Describe the structure of the basal body of a flagella in a gram negative bacterium.

A

Gram negative bacteria have two pairs of rings. The outer pair is anchored to the cell wall. The inner pair anchored to the plasma membrane.

133
Q

Describe the structure of the basal body of a flagella in a gram positive bacteria.

A

Gram positive bacteria only have the inner pair of rings anchored to the plasma membrane

134
Q

The flagella can rotate clockwise and anticlockwise. True or false?

A

True

135
Q

The speed of flagella rotation can be altered between?

A

200-17,000 rpm

136
Q

Runs by flagella are interrupted by changes in directions called…

A

Tumbles

137
Q

Flagella with a polar arrangement can have two types of flagella, one being reversible flagella, the other being…

A

Unidirectional flagella where they move rapidly and typically spin around

138
Q

Cells can move toward a favourable or away from an adverse environment by their flagella, what is this called?

A

Taxis

139
Q

What are two types of stimuli and what would the movement be?

A

Chemical and light. Chemotaxis and phototaxis

140
Q

Describe the motion of a bacterium when near a positive stimulus

A

Many runs and few tumbles

141
Q

Describe the motion of a bacterium when near a negative stimulus

A

Frequency of tumbles increase

142
Q

What is the axial filament?

A

Wraps around the cells of spirochete bacteria

143
Q

Two examples of spirochete bacteria

A

Treponema pallidum that causes syphilis and Borrelia burgdoferi that causes Lyme disease

144
Q

How is Lyme disease transmitted?

A

Through the bites of infected ticks

145
Q

How is Syphilis transmitted?

A

Sexually transmitted

146
Q

Where is the axial filament?

A

Enclosed in the space between the outersheath and the cell wall

147
Q

The rotation of the axial filament causes what type of movement for spirochete bacteria?

A

Corkscrew-type movement

148
Q

What advantage do spirochete bacteria have?

A

Most live in bodily fluids, The axial filament can allow them to swim through mucus - propel through

149
Q

Size of plasma membrane?

A

7nm

150
Q

Function of the plasma membrane

A

Separate cytoplasm from the env, selective permeability enables movement

151
Q

The phospholipid bilayer contains hydrophobic and hydrophilic components, what makes the hydrophobic environment?

A

The fatty acids - they point inwards

152
Q

The glycerophosphate heads exposed to the external environment or the cytoplasm are

A

Hydrophilic

153
Q

Proteins found on the surface of the bilayer of the plasma membrane are called

A

Peripheral proteins

154
Q

Proteins found in the bilayer of the plasma membrane are called

A

Integral proteins

155
Q

Proteins that go through the bilayer of the plasma membrane are called

A

Transmembrane proteins

156
Q

The plasma membrane is described to be _________ permeable

A

Selectively

157
Q

Is simple diffusion across a plasma membrane a passive or an active process?

A

Passive

158
Q

Facilitated diffusion involves

A

Transmembrane proteins

159
Q

Active transport involves movement

A

against a concentration gradient

160
Q

Does the bacterial cytoplasm contain a cytoskeleton?

A

No babes

161
Q

What is the nucleoid in a bacterial cell?

A

The region containing the bacterial chromosome

162
Q

The site of protein synthesis and there are 10,000+ of these per cell…

A

Ribosomes

163
Q

In a bacterial cell, the ribosomes are composed of two subunits, what are these

A

A small subunit of 30S and a large subunit of 50S to make a 70S ribosome

164
Q

The function of inclusion bodies is

A

To act as energy reserves or reservoirs of structural building blocks

165
Q

Can inclusion bodies be observed?

A

Yes by light microscopy after staining

166
Q

What are metachromatic granules?

A

They contain inorganic phosphate and a reserve of high energy phosphate

167
Q

Polysaccharide granules (starch/glycogen) contain

A

a reserve carbon and energy source

168
Q

Lipid inclusions…

A

reserve carbon and energy source

169
Q

Sulphur granules as a

A

energy reserve

170
Q

Gas vacuoles

A

for buoyancy

171
Q

Carboysome inclusion bodies

A

for co2 fixation

172
Q

Magnetosomes iron oxide inclusion bodies for

A

orienting and migrating along geo-magnetic field lines

173
Q

Endospores are

A

An endospore is a dormant, tough, and non-reproductive structure produced by certain bacteria

174
Q

Endospores work because they are

A

resistant to heat, harsh chemicals and radiation

175
Q

Endospores are produced in the ______ stage of a bacterial life cycle

A

Dormant

176
Q

They are usually produced by gram negative or gram positive bacteria?

A

Gram positive such as bacillus and clostridium

177
Q

Define sporulation

A

Endospore formation

178
Q

Define germination

A

Returning to vegetative state

179
Q

When does sporulation begin and how long does it take?

A

When a key nutrient becomes scarce, it takes several hours long

180
Q

What happens in the first stage of endospore sporulation?

A

The newly replicated bacterial chromosome and a small portion of the cytoplasm become isolated by the ingrowth of the plasma membrane (spore septum)

181
Q

What happens in the second stage of endospore sporulation?

A

The mother cell engulfs the spore leading to a double layered membrane that surrounds the chromosome and cytoplasm -> forespore

182
Q

What happens in the third stage of endospore sporulation?

A

A thick layer of peptidoglycan is laid down between the two membanes

183
Q

What happens in the fourth stage of endospore sporulation?

A

The spore coat is laid down around the outer membrane - endospore

184
Q

What happens in the fifth and final stage of sporulation?

A

The original cell ruptures releasing the spore

185
Q

There are different types of spores, what are the three?

A

Terminal, subterminal and central spores

186
Q

What are the three distinct phases of endospore germination?

A

Activation, germination and outgrowth

187
Q

What causes the activation of the germination stage?

A

Heating, for example the cytoplasm may activate at 100 degrees

188
Q

What happens in the germination stage of endospore germination?

A

In the presence of nutrients and amino acids, the spore becomes metabolically active

189
Q

What happens in the outgrowth stage of endospore germination?

A

Uptake of water. RNA, DNA protein synthesis begins and the vegetative cell emerges

Microbiology (18 decks)

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