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MCDB 131 > Lecture 14 - bacterial community > Flashcards

Lecture 14 - bacterial community Flashcards

1
Q

What type of competition is implemented with Type V and VI secretion systems

A

Contact dependent

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2
Q

What type of competition is implemented with bacteriocins

A

Contact independent

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3
Q

How was the type V secretion system discovered

A

K12 E.coli could not survive in culture with non-K12 wild isolate

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4
Q

How large is the type V secretion system pilus?

A

About 33 nm

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5
Q

What genes encode the type V secretion system?

A

cdiB, cdiA, and cdiI

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6
Q

CdiB

A

beta barrel protein that is required for export of the type V secretion pilus

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7
Q

CdiA

A

33 nm pilus for type V secretion system

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8
Q

CdiI

A

Confers immunity to the toxin exported by the type V secretion system

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9
Q

Steps of type V secretion

A
  1. Receptor binding domain on the end of the pilus binds its receptor
  2. Toxin is exported to the target cell
  3. Toxin is taken up by target cell through an outer membrane protein and inner membrane transporter
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10
Q

How many kind of toxin are exported in type V secretion?

A

One

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11
Q

What kinds of toxins are secreted in type V secretion?

A

DNase, tRNAse, pole formers

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12
Q

What are pole-forming toxins?

A

Disrupt the charge differential across cell membranes

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13
Q

How does the type V secretion system get toxin into the target cell?

A

Hijacking of regular transport proteins already expressed on the cell surface

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14
Q

How does the type VI secretion system get toxin into the target cell?

A

Needle-like tip of the pilus punctures the cell exterior

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15
Q

How many types of toxins are secreted in type VI secretion?

A

Many different kinds to cover all possibilities in the target cell

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16
Q

What is an example of a bacteriocin?

A

Colicin

17
Q

When is expression of colicin triggered

A

During the SOS response

18
Q

What genes encode the colicin system?

A

colA, immA, lysA

19
Q

Steps of colicin system implementation

A
  1. immA is expressed at all times (different promoter from colA) and provides immunity to toxin in Col+ cells
  2. extensive DNA damage induces SOS system and expression of colA
  3. LysA punches holes in damaged cell to release toxin and immunity protein into surroundings
  4. toxin is delivered to surrounding cells
20
Q

Do all cells get affected by ColA when it is released?

A

Col+ cells are always encoding the protein for immunity, so they are not affected. Only Col- cells are affected

21
Q

What kind of toxin is delivered by colicin system?

A

Nuclease

22
Q

Components of colicin protien

A
  1. translocator domain
  2. receptor binding domain
  3. effector domain
23
Q

How does colicin get into target cells?

A

Recognizes BtuB on outer membrane and imports toxin to target cell through OmpF

24
Q

What kinds of bacteria are type V and VI secretion and bacteriocins useful against?

A

Gram negative

25
Q

Quorum sensing

A

Process where bacterial cells coordinate gene expression depending on population density

26
Q

How was quorum sensing first discovered?

A

Discovered in Vibrio fischerii, a bioluminescent bacterium that colonizes the light organ of the Hawaiian bobtail squid

27
Q

Use of bioluminescent bacteria for squid

A

Counterillumination hides the squid’s shadow from predators

28
Q

How is the quorum-sensing gene system induced?

A
  1. Accumulation of a secreted autoinducer in cell surroundings
  2. Autoinducer enters neighboring cells
  3. Autoinducer binds receptor proteins that act as transcription factors
29
Q

What is the quorum-sensing gene system in Vibrio fischerii

A

LuxR-autoinducer complex activates transcription of protiens incuding LuxA and LuxB

30
Q

What causes bioluminescence in Vibrio fischerii?

A

Luciferase made by LuxA and B

31
Q

Possible functions of quorum sensing systems

A
  • bioluminescence
  • exoenzyme production
  • extracellular toxin production
  • antibiotic production
  • cell division
  • conjugation

MCDB 131 (15 decks)

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