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Infection Biology and Microbiology > Lecture 7: Pili/fimbriae and Endospores > Flashcards

Lecture 7: Pili/fimbriae and Endospores Flashcards

Tuesday 22nd October

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1
Q

where are type 1 fimbriae widespread in?

A

Enterobacteriaceae, including most E. coli

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2
Q

Which pathogens is type 1 fimbriae an important virulence factor in?

A

E. coli

Salmonella spp.

Vibrio cholerae

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3
Q

What is the size of type 1 fimbriae?

A

7 nm wide and approximately 1-2 µm long surface polymer

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4
Q

What is type 1 fimbriae made up of?

A

The bulk of type 1 fimbriae is made up of 500-3000 subunits of the protein, FimA, stacked in a helical cylinder

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5
Q

What is the tip adhesin of type 1 fimbriae?

A

FimH

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6
Q

What does the FimH tip adhesin bind to?

A

to D-mannose containing structures (we have mannose in many of our cells)

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7
Q

What links FimH adhesin onto type 1 fimbriae?

A

FimF and FimG

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8
Q

What proteins are associated with the building of type 1 fimbriae itself?

A

FimC and FimD

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9
Q

What does FimA do?

A

It hepls build the pili from the base to the top

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10
Q

What proteins catalyse FimA polymerisation?

A

FimC and FimD

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11
Q

What is another name for P pili?

A

PAP: Pyelonephritis-Associated-Pili

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12
Q

What is P-pili a critical virulence factor for?

A

Critical virulence factor of uropathogenic E. coli (UPEC) which cause cystitis and pyelonephritis

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13
Q

Does cystisis cause discomfort, but not a lot of damage?

A

Yes

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14
Q

Describe pyelonephritis

A
  • Pyelonephritis is a UTI that reaches the kidneys
  • Can be fatal
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15
Q

How is P-pili similar to type 1 fimbriae?

A

Similar in structure and assembly

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16
Q

What is the tip adhesin of P-pili?

A

PapG, which binds to surface globoside receptors (glycolipid) in uroepithelial cells

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17
Q

What are the 3 variants of PapG?

A

PapG1, PapG2 and PapG3

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18
Q

Which bacteria is type IV pili most common in?

A

Gram negatives

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19
Q

Give some examples of gram negative bacteria

A
  • Enterobacteriaceae
  • Salmonella enterica
  • Pseudomonas aeruginosa
  • Legionella pneumophila
  • Neisseria gonorrhoeae
  • Neisseria meningitidis
  • Vibrio cholerae
  • some cyanobacteria
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20
Q

can type VI pili be gram positive?

A

Some can, but they’re mostly gram negative

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21
Q

Give an example of a gram positive type VI pili

A

Clostridia

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22
Q

Is it true that Type VI pili are typically longer than fimbriae?

A

Yes (up to 10 µm)

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23
Q

Is it true that there’s only few pili per cell with type VI pili?

A

Yes (on the order of 1-10)

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24
Q

Are type VI pili typically at both poles of the cell?

A

Yes

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25
Q

Are type VI pilli hollow?

A

No, unlike flagella, which are typically very hollow

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26
Q

How do type vi pili move?

A

Via twitching motility

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27
Q

How thin are type VI pili?

A

Quite thin. About 6– 8 nm wide

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28
Q

How does type VI pili form bundles?

A

By aggregating laterally

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29
Q

Why do type VI pili form bundles?

A

This makes them more pathogenic

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30
Q

What are the roles of type VI pili?

A
  • Host cell adhesion
  • Biofilm formation (EPEC)
  • Twitching motility, crawl along a surface
  • Enable enteropathogenic E. coli (EPEC) to form microcolonies on tissue monolayers
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31
Q

Is it true that many pathogens are only specific to certain species?

A

Yes

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32
Q

What is the specificty of E coli pathogens determines by?

A

LPS (O antigen) and fimbriae (K antigen)

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33
Q

When does inter-species transfer occur?

A

If there is the correct adherence factor present on new host cells

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34
Q

How do Enterotoxigenic E. coli (ETEC) strains interact with mucous epithelium?

A

Via CFA – colonising factor antigen

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35
Q

Do non-pathogenic strains of e coli possess cfa?

A

No

36
Q

What do non-pathogenic strains of E-coli do?

A

Non-pathogenic strains adhere to colon and are routinely secreted in faeces

37
Q

What do the pathogenic strains of e coli adhere to?

A

tissues, e.g. small intestine and urinary tract

38
Q

how does e coli express its pathogenicity?

A

by production of toxins

39
Q

What are the measurements of the F pilus?

A

up to 10 µm in length and 8 nm in diameter

40
Q

Unlike other pili/fimbriae , what does the F pilus have?

A

a central 2 nm wide channel

41
Q

What type of bacteria is the F pillus usually found on?

A

Gram negative bacteria

42
Q

What type of plasmids are the F pili encoded in?

A

The F pili are encoded in plasmids that can move from one organism to another

43
Q

During adhesion, what does the Sex pillus act like?

A

The type VI pili

(Attach via tip
, Retracts to bring cells together
)

44
Q

What is the sex pilus best known in?

A

the E. coli F pilus

45
Q

when was the sex pilus first identified?

A

in 1960’s

46
Q

What is the sex pilus required for?

A

gene transfer

47
Q

How many sex pili are usually expressed per cell?

A

1-3 pili

48
Q

What is the sex pilus made up from?

A

The helical arrangement of pilin (TraA)

49
Q

Is the sex pilus an F pilus?

A

Yes

50
Q

What is conjugation?

A

a form of horizontal gene transfer, where genetic material is transferred from one bacterium to another, typically through direct contact.

51
Q

Describe the conjugation process

A
  • The sex pilus attaches to a specific receptor on the surface of the recipient bacterium. (F+ donor will only bind to F- recipent)
  • Once the pilus makes contact, it retracts, pulling the two bacteria closer together.
  • A conjugation bridge is formed, through which plasmid DNA (or sometimes chromosomal DNA) is transferred from the donor to the recipient.
  • The cells have now both undergone transformation and both become F+ cells

-

52
Q

Where do bacterial ‘endospores’ get their name from?

A

The fact that they form inside bacterial cells

53
Q

How different are bacterial endospores to fungal endospores?

A

Very different

54
Q

What are bacterial endospores extremely resistant to?

A

heat, desiccation and radiation

55
Q

Is it true that some bacterial endospores can be viable for 100,000 years?

A

Yes

56
Q

How can bacterial endospores be dispersed?

A

through wind, water and faeces

57
Q

When do bacterial endospores form ?

A

When a vegetative cell becomes stressed

58
Q

When may bacterial endospores germinate and produce new vegetative cells?

A

When conditions become favourable again

59
Q

What conditions are bacterial endospores mostly found in ?

A

Soil bacteria

60
Q

Is it true that the genera of bacterial endospores mostly include Bacillus, Clostridium, Sporosarcina
?

A

Yes

61
Q

Do gram positives or gram negatives produce endospores?

A

Gram positives

62
Q

What does Clostridium perfringens cause?

A

Gas gangrene

63
Q

Describe how bacterial endospores look like under phase contact

A
  • bright refractile inclusions
  • Can be terminal or sub-terminal, oval or spherical
  • Some cause cell wall to bulge
64
Q

Which spore formers are important antigens?

A

Bacillus anthracis

Clostridium botulinum

Clostridium perfringens (causes gas gangrene)

65
Q

Is it true that sporulation has several stages, each controlled by different genes?

A

Yes

66
Q

How many genes are involved in sporulation?

A

More than 200

67
Q

How many hours does sporulation take to complete?

A

Around 8 hours

68
Q

What causes sporulaiton genes to be switched on?

A

Environmental trigger stops production of normal cell growth proteins and switches on sporulation genes
Trigger is probably nutrient depletion

69
Q

Stages of sporulation

A
  • Vegetative cell makes sure that it has 2 copies of its DNA (one to go into the spore and one to survive in the cell)
  • Invaginations in cellular membrane
  • DNA is organised along its long axis
  • Encloses one copy of the DNA into a forespore septum (section of the cell produced by the invaginations).
  • Cell membrane engulfs forespore in a second membrane
  • The cell dehydrates the inside of the spore by filling it with calcium and dipicolinic acid. This makes the spore very resistant to heat and to chemical attack.
  • To make the spore more robust to physical damage, complex exosporium layers are produced on its outside
  • A layer of cortex is produced on the outside of the spore to allow the spore to stick to surfaces, like soil particles and animal skin
  • Original cell lyses releasing spore
70
Q

What is the outer most layer of a spore, the exosporium, used for?

A

Not essential for survival but maybe for dispersal

71
Q

What does the spore coat consist of?

A

spore-specific proteins

72
Q

What does the core of an endospore include?

A

containing genome, cytoplasm, ribosomes, but metabolically inactive

73
Q

Why do the endospores need to be dehydrated?

A

To prevent denaturation

74
Q

What temperatures can endospores withstant?

A

150 degrees celcius

75
Q

What maintains the genome integrity and prevents the formation of pyrimidine dimers in DNA?

A

Small acid soluble proteins

76
Q

IS there any discernable metabolic activity inside the spore?

A

No

77
Q

What triggers germination in endospores?

A

Uptake of water and amino acids

78
Q

How long does germination take?

A

Rapid process, complete in 30 mins

79
Q

During germination, when a cell is released, does it begin to grow in a normal way?

A

Yes and the cell will usually be Gram negative on release but as peptidoglycan layer is rapidly built up they become Gram positive again

80
Q

What do more people in the world die from, infectious disease, or heart disease or cancer?

A

Infectious disease

81
Q

In 2002, how many deaths worldwide were attributable to infectious disease?

A

In 2002, 14.9 million deaths world wide were attributable to infectious disease

82
Q

In Africa over 50% of all deaths in 2016 were due to infectious diseases
Compares to only 10% in all of the Americas

A
83
Q

What is one of the most devastating infectious diseases humans have suffered from?

A

The Black Death – Bubonic Plague

84
Q

When were there pandemics of the plague in Asia and Europe?

A

In the mid 14th century

85
Q

What percentage of the european population was the plague said to have wiped out in the middle ages?

A

Believed to have wiped out between 30-60% of European population in the middle ages, which was about t 1 in 6 of the world’s population at that time (Equivalent to 1 billion people today
)

86
Q

What is the causative agent of the bubonic plague?

A

Yersinia pestis, transmitted by rodent populations carrying rat fleas
(Some scientists dispute this saying it moved too quickly across the world
)

87
Q
A

Infection Biology and Microbiology (23 decks)

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