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MIMM465: Bacterial Pathology > Reed Lectures > Flashcards

Reed Lectures Flashcards

1
Q

2 properties of a bacterial pathogen

A
  1. can colonize host
  2. causes disease
    Many bacteria in the environment don’t cause disease
    Not all strains of a pathogen will cause disease
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2
Q

Define virulence. Give a major determining factor for virulence

A

Ability to cause disease; host susceptibility

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3
Q

Define virulence factor, and give an example

A

Any strategy that promotes disease-causing properties/causes virulence
ex. toxins, secretion systems

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4
Q

T or F: infection always leads to disease

A

False. Asymptomatic ppl are called carriers (colonized by bacteria, but show no symptoms of disease)

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5
Q

Define bacterial pathogenesis

A

Mechanisms through which bacteria cause disease

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6
Q

Why is it important to study bac path?

A

To development prevention strategies (Vaccines) and treatments (Antibiotics)

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7
Q

3 bacteria that Robert Koch studied

A

B. anthracis
M. tuberculosis
V. cholerae

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8
Q

List Koch’s postulates

A
  1. Microbe must be associated with symptoms of disease and must be present at site of infection
  2. Microbe must be isolated from disease lesions and be grown in pure culture
  3. Inoculation of isolated bacteria into healthy host needs to generate the same disease
  4. The same microbe must be re-isolated from the inoculated host
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9
Q

Give limitations to Koch’s postulations

A
  1. Not all infections lead to clinical symptoms; host susceptibility determines virulence and whether disease develops or not
  2. Cannot grow many bacteria in pure culture due to complex nutritional/environmental needs for growth
  3. To test the 3rd postulate, you need a perfect animal model that perfectly replicates the disease seen in humans. Often, this is not the case. The strain of bacteria causing disease X in humans may not cause the same symptoms in mice. Therefore, may need to change the mouse (ex. mutant mice), or use another strain of bacteria to emulate similar symptoms
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10
Q

Give 2 molecular biology techniques that can be used to identify presence of microbes in carriers

A
  1. PCR - identifies bacterial DNA

2. IHC - identifies bacterial proteins

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11
Q

Who developed the molecular Koch postulates?

A

Stanley Falkow

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12
Q

List the molecular Koch postulates

A
  1. A suspected virulence factor (gene) should not be present in the avirulent strain.
  2. Disrupting the virulent gene should attenuate its virulence. Reintroducing WT gene should reconstitute virulence
  3. Putting putative virulent gene in non-virulent bacteria should cause it to become virulent
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13
Q

Give limitations to the molecular Koch postulates

A
  1. virulence may be multifactorial - requires multiple genes/a gene cassette for full virulence to occur
  2. disrupting bacterial metabolism/biochemical pathways can also attenuate virulence - are such housekeeping pathways virulence factors?
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14
Q

uropathogenic E. coli (UPEC) causes what infection?

A

UTI (urinary tract infection)

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15
Q

What cell type does UPEC infect?

A

bladder epithelium

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16
Q

Give 4 ways that UPEC can interact with host cells

A
  1. Attachment via pili
  2. rearrange host cell cytoskeleton by interacting with actin
  3. interact with host signalling pathways
  4. form microcolonies
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17
Q

T or F: coordinated expression of virulence facts is essential for full virulence and disease

A

T

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18
Q

UPEC expresses Type __ pili. It is required for what?

A

Type 1. Needed for colonization, invasion, persistence.

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19
Q

Where do IBCs form? nucleus, vesicles, or cytoplasm?

A

cytoplasm

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20
Q

What are IBCs

A

Intracellular bacterial colonies

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21
Q

Are filamentous bacterial cells (UPEC) proliferating or non-proliferating?

A

Proliferating - allows them to evade killing by neutrophils

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22
Q

What are quiescent intracellular reservoirs? (QIR) What type of host cell are they established in?

A

Non-replicating bacteria form QIR for long term survival. Established in transitional cells below uroepithelium.

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23
Q

Name 1 toxin that UPEC secretes for nutrient acquisition

A

alpha-haemosylin (HlyA) - lyses host cell to release nutrients
Also a way for UPEC to exit 1 cell and spread to another

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24
Q

T or F: UPEC doesn’t need coordinated expression of virulence factors to cause disease

A

F - expression of proteins/virulence factors needed to cause disease are organized into 3 main steps: entry, survival + proliferation in cell, exit.

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25
Q

T or F: Knocking out 1 virulence factor may lead to avirulence, but it may still lead to full disease

A

F - full disease requires combined effects of each virulence factor. Ability for bacteria to cause disease may be attenuated if one virulence factor is missing/mutated/disrupted

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26
Q

Is a single virulence factor known to be essential for virulence sufficient to cause full disease?

A

NO. Full disease requires combined effects of each virulence factor

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27
Q

T or F: Sec and Tat secretion pathways are present in Gram negatives only

A

F. they are common to both Gram + and -

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28
Q

What does Tat stand for?

A

Twin arginine translocation

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29
Q

What are the Sec and Tat pathways?

A

General bacterial secretion pathways used to transport proteins across cytoplasmic membrane.

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30
Q

T or F: many proteins are secreted through the Sec and Tat pathways

A

T

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31
Q

T or F: many proteins secreted by Sec and Tat systems are secreted outside the cell

A

F. Most proteins secreted through these systems are destined for periplasm or cytoplasmic membrane

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32
Q

The _____ is required for proteins to be localized to a specific location

A

signal sequence

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33
Q

T or F: 2 step pathways are commonly required in Gram + bacteria to secrete proteins out of the cell

A

F. commonly required in Gram NEGATIVE bacteria. The first step often involves Sec or Tat, while the second step (secretion out of cell) involves another secretion system

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34
Q

Are Sec and Tat pathways active or passive transport systems?

A

Active

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35
Q

The general Sec pathway transports folded or unfolded proteins?

A

unfolded

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36
Q

The protein transported by Sec pathway often have a signal sequence at C or N terminal?

A

N

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37
Q

T or F: The general Sec pathway is not essential to gram + and - bacteria.

A

F - ESSENTIAL for survival bc most proteins are transported through this pathway

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38
Q

What provides the energy for active transport in Sec pathway?

A

SecA - an ATPase, and proton motive force

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39
Q

T or F: Tat pathway is a passive transport system.

A

F - ACTIVE

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40
Q

Tat pathway transports unfolded or fully folded proteins?

A

Fully folded; bound to cofactors

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41
Q

T or F: Tat pathway is present in all bacteria

A

F

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42
Q

Proteins that go through Tat pathway must have what signal?

A

twin-arginine motif on N terminus

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43
Q

T or F: Many proteins that enter general Sec pathway are bound to cofactors

A

F - many proteins entering TAT pathway are bound to cofactors

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44
Q

Energy to transport proteins in Tat pathway comes from where?

A

Proton motive force

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45
Q

List 4 Gram + secretion systems

A

General Sec Pathway (essential)
Injectosome
Sortase system (SrtA)
T7SS/ESX

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46
Q

The sortase system anchors proteins to the ___ of Gram+ bacteria

A

cell wall/precursor peptidoglycan

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47
Q

The sortase systems recognizes proteins coming through the ___ pathway with a ____ motif

A

Sec; LPxTG

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48
Q

T or F: The LPxTG motif is present at the N terminus of the protein.

A

F - present at C terminus. The N terminus contains the signal sequence

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49
Q

Which Gram + secretion system transports small proteins ~100 AA long?

A

T7SS/ESX

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50
Q

Which Gram + secretion systems transports proteins with WxG motif?

A

T7SS/ESX

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51
Q

T or F: T7SS-exported proteins often dimerize

A

T

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52
Q

Give a major pathogen that contain the T7SS

A

M. tuberculosis

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53
Q

Is the Sortase system in Gram + or -?

A

+

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54
Q

Is the ESX system in Gram + or -?

A

+

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55
Q

T or F: injectosome transports things across cell wall directly into host cell cytoplasm

A

T

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56
Q

T or F: T7SS forms a channel.

A

T

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57
Q

Give the functions of ESX-1, ESX-3, ESX-5

A

ESX1; pokes holes in phagosomes to transport bacterial proteins into cytoplasm; essential for bacterial survival in phagosomes
ESX3: Fe acquisition
ESX5: involved in host immune invasion; secretes mycobacteria specific PE and PPE protein families

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58
Q

Define exoproteins/exotoxins

A

Proteins secreted outside the bacterium and acts on host cell

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59
Q

Define effector proteins

A

Bacterial proteins secreted directly into host cell cytoplasm ; mediated by T3, 4, and 6 SS

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60
Q

T or F: Effector protein secretion is dependent on Sec pathway

A

F: independent

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61
Q

Are all Gram - secretion systems essential?

A

No - this makes them good targets for antibiotics bc they’re not under pressure to mutate to survive the drug

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62
Q

Flagella is used in which types of bacterial motility?

A

Swarming and swimming

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63
Q

What is a peritrichous bacterium?

A

Bacterium with several flagella all over its body

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64
Q

T or F: The flagella is a simple structure

A

F

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65
Q

T or F: All genes involved in structure, regulation, and function of flagella are considered virulence factors

A

T

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66
Q

T or F: T5SS are thought to have evolved from flagellar systems

A

F: T3SS

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67
Q

Motile bacterial cells run or tumble more frequently when they are moving towards chemoattractants?

A

Run

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68
Q

T or F: flagella expression can be regulated

A

T. Also, flagella can switch from polar states to peritrichous states.

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69
Q

Primary lesions are associated with latent or active TB?

A

Latent

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70
Q

The greatest number of Mtb bacteria are found in which structure? Why?

A

Cavitary lesions; lots of oxygen

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71
Q

List the main factor that induces Mtb dormancy in latent TB:

A

Availability of oxygen

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72
Q

Granulomas contains lots/little oxygen? What is the word for lacking oxygen?

A

Very little; granulomas are hypoxic

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73
Q

Does Mtb require oxygen for growth?

74
Q

What evidence showed that Mtb needs a period of adaption to adapt their metabolism to anaerobic conditions?

A

Putting Mtb into anaerobic chamber with rapid depletion of O2 caused Mtb death

75
Q

What does the plateau on a bacterial growth chart mean for Mtb?

A

Oxygen and nutrients have been depleted

76
Q

T or F: ATP synthesis levels go down to 0 in dormant, non-growing Mtb

77
Q

T or F: MTb can regulate their expression of ATP synthase (the protein complex)

78
Q

Are dormant Mtb still metabolically active?

A

Yes - they still produce ATP, but at low levels

79
Q

What was being searched for in a whole cell screening assay?

A

Compounds with antimycobacterial activity

80
Q

What does Bedaquilline do?

A

Inhibits ATP synthesis in Mycobacteria

81
Q

How was Bedaquilline discovered?

A

Whole cell screening assay

82
Q

Why is INH (drug) ineffective at killing latent Mtb?

A

It targets glycolic acid synthesis. Glycolic acid synthesis is the main component in cell wall, and synthesis is only active when bacteria are replicating (ie. not in dormant state)

83
Q

Humans also have ATP synthase, so why is BDQ safe to use in humans? Wouldn’t BDQ also target human ATP synthase?

A

There are AA differences in binding site between human and Mycobacterial ATP synthase. The binding site on human ATP synthase is not correct, therefore BDQ has low affinity for it.

84
Q

Genes related to ________ are highly induced in Mtb inside macrophages

A

lipid catabolism

85
Q

The upregulated genes for lipid catabolism are commonly found in which pathways?

A

Beta oxidation pathway

Glyoxylate cycle

86
Q

Which enzyme that is part of the glyoxylate cycle is highly upregulated in Mtb that have infected macrophages?

A

isocitrate lyase (ICL)

87
Q

What is the name of the process that breaks down fatty acids?

A

Beta oxidation

88
Q

What is the product of beta oxidation?

A

Acetyl-CoA

89
Q

What is the ultimate result of beta oxidation?

A

ATP synthesis

90
Q

List the basic steps in generating ATP from beta oxidation

A
  1. FA and lipids are catabollized via beta oxidation to produce acetyl-coA
  2. Acetyl-coA enters TCA cycle and is oxidized to CO2
  3. NADH and ATP are generated during TCA cycle; NADH enters ETC to produce more ATP
91
Q

What is important about the glyoxylate cycle that allows Mtb to use FA as their only source of E?

A

No carbons are wasted/oxidized to CO2, therefore C can be redirected to making biosynthetic precursors needed for making AA, etc.

92
Q

Why is the glyoxylate cycle attractive as a drug candidate to target Mtc?

A

Glyoxylate cycle doesn’t occur in humans

93
Q

Which opern encodes a major cholesterol import system in Mtb?

94
Q

Will knocking out mce4 operon prevent Mtb from infecting people?

95
Q

How does Mtb induce a foamy macrophage phenotype?

A

By altering the signalling and transcriptional regulation in macrophages

96
Q

What is a foamy macrophage phenotype?

A

High in cholesterol, lipid vesicles

97
Q

Name 2 key virulence traits

A
  1. motility via flagella

2. metabolic shifts/adapting metabolism

98
Q

What is the major source of energy and Carbon molecules for Mtb inside the host?

A

Fatty acids

99
Q

What are the 3 essential components of a T1SS

A
  1. ATP binding cassette (ABC) transporter protein
  2. Membrane fusion protein
  3. Outer membrane factor
100
Q

Where is the ABC transporter protein located?

A

Inner membrane of Gram negatives

101
Q

What does the membrane fusion protein do?

A

Bridges IM to OM

102
Q

Give an example of a outer membrane factor

103
Q

What does TolC do?

A

Multipurpose pore-forming protein

104
Q

What does the T1SS do?

A

transports substrates in one step across inner and outer membrane of the Gram negative bacteria

105
Q

What does the T2SS do?

A

Translocates proteins from periplasm to extracellular space (transport across outer membrane)

106
Q

Which Gram - secretion system transports proteins across the outer membrane?

107
Q

Which Gram - secretion system transports proteins across both IM and OM?

108
Q

Which systems bring proteins into the periplasm?

A

General Sec or Tat pathways

109
Q

T or F: T2SS transports unfolded proteins across the OM

A

F - transports folded proteins

110
Q

What type of proteins are generally secreted by T2SS?

111
Q

Give a classic example of a T2SS substrate

A

Cholera toxin (in V. cholerae)

112
Q

The T2SS secretion apparatatus consists of 12-15 ___ proteins, the genes of which are organized into __ operon

113
Q

What are the 4 main components of a T2SS?

A
  1. OM channel aka secretin
  2. IM platform
  3. Secretion ATPase
  4. Pseudopilus
114
Q

The T2SS transports exoproteins or effector proteins?

A

Exoproteins

115
Q

Where are the genes for structural components of T3SS usually encoded on?

A

Plasmids and pathogenicity islands

116
Q

T or F: T3SS can be horizontally acquired. Explain

A

T - genes coding for T3SS structural components are on plasmids, which can be horizontally transferred

117
Q

T or F: evolutionarily distinct bacteria can have similar T3SS

A

T, due to horizontal transfer of T3SS genes

118
Q

What are the 3 components of a T3SS?

A
  1. base complex/basal body
  2. needle component
  3. translocon
119
Q

T or F: the translocon is essential for secretion of exoproteins

A

F - but it is essential for passage of effector proteins through host membrane

120
Q

Are T3SS always intact on the bacterial membrane?

A

No. Assembly is regulated - is only formed when bacteria comes in contact with host cell

121
Q

T or F: folded proteins are secreted through needle of T3SS

A

F - the proteins are unfolded, and are also unfolded in bacterial cytoplasm

122
Q

How do unfolded proteins (transported by T3SS) stay as indvl proteins and not aggregate together?

A

They are bound to chaperones

123
Q

What do T3SS effector proteins do in the host cell?

A

Modulate host signalling pathways to promote bacterial survival and establish an infection

124
Q

In T3SS, what causes bacteria to sense whether or not is has contacted a host cell

A

Tip complex

125
Q

List 2 functions of the tip complex

A
  1. senses whether bacteria is near host cell

2. regulates transport of effector proteins

126
Q

What is the significance of eukaryotic-like domains in T3SS effector proteins?

A

They modulate host signalling pathways

127
Q

Which Gram neg secretion system is structurally similar to conjugative DNA transfer apparatus?

128
Q

T5SS substrates have what type of domain?

A

beta-barrel domain

129
Q

T6SS evolved from the structure of which microbe?

A

Contractile tail of bacteriophage

130
Q

What are the 3 components of T6SS?

A
  1. Outer tube - VipA/VipB
  2. Inner tube - HcP
  3. puncturing device - VgrG
131
Q

What induces the T6SS to puncture target cell?

A

Contact with target cell

132
Q

Name a Gram neg bacteria that has the T6SS

A

P. aeruginosa

133
Q

What happened if Tse2 is injected into a cell lacking Tsi2?

A

The cell lacking Tsi2 dies bc Tsi2 protein confers immunity against Tse2 toxin

134
Q

List the 4 domains of T5SS substrates. Which domain is not present in all substrates?

A
  1. Translocator
  2. Linker
  3. Passenger
  4. Protease - not present in all substrates
135
Q

What is twitching powered by?

A

Type IV pili

136
Q

What is swarming powered by?

A

rotating flagella

137
Q

What is swimming powered by?

A

rotating flagella

138
Q

If flagella is turning in CW motion, is the cell running or tumbling?

139
Q

If flagella is turning in CCW motion, is the cell running or tumbling?

140
Q

What are the 3 substructures of the flagella?

A
  1. Basal body
  2. filament
  3. hook
141
Q

What is the basal body and what does it do?

A

A series of protein rings

Anchors flagella to cell envelope

142
Q

What is the filament and what does it do?

A

Polymerized flagellin subunit that acts as propeller

143
Q

What is the hook and what does it do?

A

Connects basal body to filament and serves as a joint

144
Q

Where does the energy for flagellar motion come from?

A

Proton gradient across the cytoplasmic membrane

145
Q

Which secretion system is crucial for assembling the components of the flagella that lie outside the cytoplasmic membrane?

146
Q

CheY alters its binding affinity for ___

A

FLiM = flagellar motor switch protein

147
Q

If CheY is not phosphorylated, is the cell running or tumbling?

A

CCW - running

148
Q

If CheY is phosphorylated and bound to flagellar motor switch protein, is the cell running or tumbling?

A

CW - tumbling

149
Q

What are the chemoreceptors in bacteria that regulate flagella motion called?

A

methyl-accepting chemotaxis proteins

150
Q

What does the MCP do?

A

Binds chemoattractants and is methylated or demethylated by CheA or CheB, depending on the concentration of chemoattractants

151
Q

What is the autokinase part of the MCP called?

A

CheA histidine kinase

152
Q

When is the CheA histidine autokinase turned on?

A

When there is high concentration of repellent

153
Q

What happens where there is a high concentration of chemorepellent?

A

CheA histidine autokinase turns to ON conformation
Autokinase phosphorylates MCP
P group transferred to CheY
CheY-P induces CW motion of rotor –> tumbles

154
Q

What happens when there is a high concentration of chemoattractant?

A

CheA histidine autokinase is OFF
MCP is not phosphorylated
CheY is not phosphorylated
CheY induces CCW motion of rotor –> runs

155
Q

If flagellins are antigenic, how do they escape detection by host’s immune system?

A

Flagella expression is regulated so they’re not expressed once inside host

156
Q

Flagella biosynthesis is regulated by ___

A

phase variation/antigenic variation

157
Q

FljA is a repressor of ___ in which bacteria?

A

FliC, Salmonella

158
Q

List 2 properties of Chlamydiae

A
  1. Gram negative

2. obligate intracellular pathogens

159
Q

How many species in the Chlamydiaceae family are pathogenic to humans and animals?

160
Q

What are the 2 major species of Chlamydia that infect humans?

A

C. penumoniae

C. trachomatis

161
Q

What are the 2 serovars of C. trachomatis?

A
  1. ocular –> trachoma

2. genital –> STD

162
Q

The 2 C. trachomatis serovars are _____-trophic pathogens that infect ocular and genital ___

A

epithelium, mucosa

163
Q

Is trachoma a preventable infection?

164
Q

Which regions of the world do ocular serovar C. trachomatis infections occur? Why?

A

Developing countries; lack of sanitation and clean running water

165
Q

Are people infected with C. trachomatis gential serovar often symtpomatic or asymptomatic?

A

Asymptomatic

166
Q

Are there antibiotics available for C. trachomatis infections?

A

Yes - azithromycin, doxycycline, eythromycin

167
Q

T or F: Chlamydia genomes are large with manygenes encoding for metabolic enzymes

A

F - small and lacking many metabolic enzymes, which is why their obligate intracellular pathogens - reliant on host for metabolic requirements

168
Q

Chlamydia codes for which secretion systems?

A

T5SS, T3SS, T2SS

169
Q

The Chlamydia life cycle is ____

170
Q

What is the infectious form of Chlamydia called?

A

Elementary body

171
Q

List 3 properties of the elementary body

A

extracellular
metabolically inert
infectious

172
Q

What is the non-infectious form of Chlamydia called?

A

reticulate body

173
Q

What are 3 properties of the reticulate body

A

non-infectious
metabolically active
intracellular

174
Q

How does the reticulate body replicate?

A

Binary fission

175
Q

What happens after the reticulate body replicates?

A

Differentiates back into elementary body and causes host cell lysis to exit cell

176
Q

T or F: plasmids are not found in Chlamydia

A

F - plasmids are highly conserved

177
Q

How do elementary bodies enter the host cell?

A

They secrete translocated actin recruiting protein (TARP), a T3SS effector.
TARP causes actin to be recruited to entry site by activating Rac-dependent signalling cascade

178
Q

How is the cytoskeletal framework around the RB –> EB dismantled to allow the EB to exit cell?

A

EB secrete CPAF = chlamydial protease activity factor

179
Q

How many ORF are on Chlamydial plasmids?

180
Q

Which ORF on Chlamydial plasmids code for many putative virulence factors?

181
Q

What is Pgp4?

A

A trancriptional regulator of genes that are candidate virulence factors

MIMM465: Bacterial Pathology (6 decks)

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