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Cells to Organisms - Lectures > Lecture 4. Motility and Chemotaxis in Bacteria > Flashcards

Lecture 4. Motility and Chemotaxis in Bacteria Flashcards

1
Q

How do bacteria move ?

A

Use flagella and a proton motor force

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2
Q

What is a proton motor force ?

A

Protons move from a high-density area on the periplasm side of the inner membrane along a proton motor gradient through the motor, causing the motor to turn

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3
Q

What happens when flagella rotate anticlockwise ?

A

The flagella bundle forward at a great speed

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4
Q

What is a run ?

A

When flagella rotate anticlockwise causing the flagella to move forward at a great speed

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5
Q

What happens when the flagella rotate clockwise ?

A

The flagella bundle unravels and the bacteria tumbles

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6
Q

In a homogenous environment, is there an equal number of run and tumbles ?

A

Yes

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7
Q

What is a random walk ?

A

An equal amount of run and tumbles, in a homogenous environment

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8
Q

What happens to run and tumbles, when the environment is improving over time ?

A

There are more runs than tumbles

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9
Q

What does the motor filament structure require in flagella motor filament ?

A

Many genes

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10
Q

What does the expression of many genes in the motor filament structure form ?

A

Protein monomers

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11
Q

What is an example of protein monomers ?

A

FliC

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12
Q

What causes the motor to turn ?

A

Protons moving along a protein gradient from the periplasmic space moving between the stator and motor before moving into the cytoplasm

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13
Q

What is the motor filament export apparatus known as ?

A

A type 3 secretion system

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14
Q

What is the order of assembly in flagella ?

A
  1. Motor
  2. Hook
  3. Filament
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15
Q

What does the export apparatus do ?

A

Moves protein monomers through the centre of the assembled structure until they reach their destination where they self assemble

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16
Q

What are transcription genes involved in the motors filaments structure function ?

A

They are tightly regulated in the timing of their activation

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17
Q

What are the master regulators involved in flagellum expression ?

A

flhC and flhD

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18
Q

Where are flhC and flhD expressed from ?

A

The flhDC operon

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19
Q

What is the flhDC operon linked to ?

A

Many stress responses of cells

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20
Q

What is the flhDC operon positively enhanced by ?

A

The cAMP-CRP activation complex

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21
Q

What does the cAMP-CRP activation complex create ?

A

A transcriptional activation complex that activates the middle genes

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22
Q

What do sigma factors form in flagellum gene expression ?

A

Components of the RNA polymerase complex that direct complexes towards specific classes of promoters

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23
Q

What is the sigma factor responsible for directing the polymerase complex towards the later genes ?

A

FliA/sigma 28

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24
Q

When the middle genes are being expressed what is FliA bound to and inactivated by ?

A

FLGM

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25
Q

What is FLGM ?

A

An anti-sigma factor

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26
Q

What happens once middle genes are finished doing their jobs ?

A

The FLGM protein detaches from fliA and moves through the flagella complex. FliA can now direct RNA polymerase towards the late genes/spatial temporal regulation

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27
Q

How are the flagella of E.coli arranged ?

A

Peritrichously - spread over the entire surface

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28
Q

What helps salmonella to evade host defences ?

A

FliC being replaced by FliB - randomly switching

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29
Q

What is the name for the process of salmonella evading host defences ?

A

Phase variation

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30
Q

In the genetic of flagellin protein expression in salmonella, what does bacteria randomly switch between ?

A

Either flijBA operon or fliC gene

31
Q

In the genetic of flagellin protein expression in salmonella, is the switching random ?

A

No it is biased towards switching from phase H2 to H1

32
Q

In the genetic of flagellin protein expression in salmonella, what happens in phase H2 ?

A

The flijBA operon and the fliC gene is off

33
Q

In the genetic of flagellin protein expression in salmonella, what happens in phase H1 ?

A

The fljBA operon is off and the fliC gene is on

34
Q

What is fljA ?

A

An inhibitor of fliC expression that acts post transcriptionally and blocks the translation of fliC mRNA

35
Q

What is the fljB fljA operon ?

A

Invertible

36
Q

Where is DNA in the chromosome physically inverted ?

A

Between the hixL and hixR inverted repeats

37
Q

What is an inverted repeat ?

A

A single stranded sequence of nucleotides followed downstream by its reverse complement

38
Q

What is H switch ?

A

The invertible genetic element of DNA in the chromosome

39
Q

What are hixR and hixL ?

A

Identical but orientated in opposite directions

40
Q

When are genes no longer transcribe in the genetic of flagellin protein expression in salmonella ?

A

Once the promoter faces away from the operative genes

41
Q

What encodes Hin invertase ?

A

9966-bp H-switch

42
Q

What is Hin invertase?

A

A site specific recombination protein – serines recombinase

43
Q

Where are hin repeats bought together ?

A

At an enhancer region within the Hin gene

44
Q

What are Hin repeats held in place by ?

A

The Hin protein tetramer

45
Q

What cuts DNA at inverted repeats ?

A

Catalytic components of invertors

46
Q

How is the Hin invertasome formed ?

A

DNA swap positions with respect to the rest of the genome and re-join ends - inverting the switch

47
Q

What are HU and FIS ?

A

Architectural DNA binding proteins and are also known as KNAPs

48
Q

What does KNAP stand for ?

A

nucleate associative proteins

49
Q

What is the role of KNAP In the genetic of flagellin protein expression in salmonella ?

A

Structure DNA in the nuclear site in a highly organised fashion

50
Q

What does protein HU help ?

A

Loop formation and helps tight bending in the smaller loop

51
Q

What does protein FIS do ?

A

Enhances Hin activity by stabilising correct DNA topology

52
Q

Why is the right loop larger ?

A

As it is not equidistant from the inverted repeats

53
Q

Why can the right loop form on its own ?

A

Due to the intrinsic ability of DNA to bend

54
Q

What is chemotaxis ?

A

A system that detects signals from the environment, transduces signal across the membrane into the cell and causes an effect which allows bacteria to respond to the situation

55
Q

How does chemotaxis occur ?

A

Using signal transduction by a two component regulatory system

56
Q

What does the sensor protein have ?

A

A transmitter component containing a histidine residue

57
Q

What does the output protein contain ?

A

A receiver domain with a conserved aspartic acid

58
Q

What happens when a sensor receives a signal ?

A

The structure changes slightly and causes the histidine residue in the transmitter domain to become phosphorylated

59
Q

What happens after the transmitter domain becomes phosphorylated ?

A

It in turns phosphorylates the receiver domain of the output protein on the conserved aspartic acid residue

60
Q

Where is the sensor histidine kinase ?

A

Embedded in the cell membrane

61
Q

What is the methyl accepting chemotactic protein ?

A

The sensor histidine kinase embedded in the cell membrane

62
Q

What happens when the MCP detects the signal from outside the cell ?

A

It initiates the signal cascade by becoming phosphorylated on the histidine.

This in turn causes the phosphorylation of the aspartic acid in the output side of the system

63
Q

What is a methyl accepting protein monomer composed of ?

A

Up, down up down four helical structure

64
Q

What do the first and last helixes of the methyl accepting protein extend into ?

A

The cytoplasm

65
Q

What does the sensing domain homodimer of the methyl accepting protein have ?

A

Two symmetrical, non - overlapping aspartate binding sites at the dimer interface

66
Q

What does binding at the aspartate at either symmetric site act as ?

A

A confirmation change that precludes binding to a second site

67
Q

What is an example of further ligand induced conformational changes which is the source of signaling across the cell membrane or inhibitor of cheA kinase activity in the cytoplasm ?

A

The downwards piston like movement of the second transmembrane helix, with the first transmembrane helix and a rotation of the dimer subunits

68
Q

What creates a short term memory within the chemotaxis system allowing it to constantly reset ?

A

Cycles of methylation by cheR and cheD by cheBs by MCPs

69
Q

What happens in methyl accepting protein monomer when attractants are present ?

A

The alpha helical bundles remain apart and cheA remains inactive

70
Q

What happens when methyl accepting protein attractants are absent ?

A

The bundles come together and cheA becomes phosphorylated with the help of cheW

71
Q

What happens when cheA is active and phosphorylated ?

A

It fuses to the motor complex where it in turn is phopshorylated by cheY

72
Q

What does phosphorylated cheY do ?

A

It interacts with film motor proteins and causes tumbling to be suppressed

73
Q

What does cheY become dephosphorylated by ?

A

CheZ and the system is reset

74
Q

What are the chemoreceptor sensory domains of methyl accepting protein linked by ?

A

Conserved cytoplasmic domains

Cells to Organisms - Lectures (36 decks)

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