Lecture 4. Motility and Chemotaxis in Bacteria

Question 1

How do bacteria move ?

Answer 1

Use flagella and a proton motor force

Question 2

What is a proton motor force ?

Answer 2

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

Question 3

What happens when flagella rotate anticlockwise ?

Answer 3

The flagella bundle forward at a great speed

Question 4

What is a run ?

Answer 4

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

Question 5

What happens when the flagella rotate clockwise ?

Answer 5

The flagella bundle unravels and the bacteria tumbles

Question 6

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

Answer 6

Yes

Question 7

What is a random walk ?

Answer 7

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

Question 8

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

Answer 8

There are more runs than tumbles

Question 9

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

Answer 9

Many genes

Question 10

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

Answer 10

Protein monomers

Question 11

What is an example of protein monomers ?

Answer 11

FliC

Question 12

What causes the motor to turn ?

Answer 12

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

Question 13

What is the motor filament export apparatus known as ?

Answer 13

A type 3 secretion system

Question 14

What is the order of assembly in flagella ?

Answer 14

1. Motor
2. Hook
3. Filament

Question 15

What does the export apparatus do ?

Answer 15

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

Question 16

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

Answer 16

They are tightly regulated in the timing of their activation

Question 17

What are the master regulators involved in flagellum expression ?

Answer 17

flhC and flhD

Question 18

Where are flhC and flhD expressed from ?

Answer 18

The flhDC operon

Question 19

What is the flhDC operon linked to ?

Answer 19

Many stress responses of cells

Question 20

What is the flhDC operon positively enhanced by ?

Answer 20

The cAMP-CRP activation complex

Question 21

What does the cAMP-CRP activation complex create ?

Answer 21

A transcriptional activation complex that activates the middle genes

Question 22

What do sigma factors form in flagellum gene expression ?

Answer 22

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

Question 23

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

Answer 23

FliA/sigma 28

Question 24

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

Answer 24

FLGM

Question 25

What is FLGM ?

Answer 25

An anti-sigma factor

Question 26

What happens once middle genes are finished doing their jobs ?

Answer 26

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

Question 27

How are the flagella of E.coli arranged ?

Answer 27

Peritrichously - spread over the entire surface

Question 28

What helps salmonella to evade host defences ?

Answer 28

FliC being replaced by FliB - randomly switching

Question 29

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

Answer 29

Phase variation

Question 30

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

Answer 30

Either flijBA operon or fliC gene

Question 31

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

Answer 31

No it is biased towards switching from phase H2 to H1

Question 32

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

Answer 32

The flijBA operon and the fliC gene is off

Question 33

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

Answer 33

The fljBA operon is off and the fliC gene is on

Question 34

What is fljA ?

Answer 34

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

Question 35

What is the fljB fljA operon ?

Answer 35

Invertible

Question 36

Where is DNA in the chromosome physically inverted ?

Answer 36

Between the hixL and hixR inverted repeats

Question 37

What is an inverted repeat ?

Answer 37

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

Question 38

What is H switch ?

Answer 38

The invertible genetic element of DNA in the chromosome

Question 39

What are hixR and hixL ?

Answer 39

Identical but orientated in opposite directions

Question 40

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

Answer 40

Once the promoter faces away from the operative genes

Question 41

What encodes Hin invertase ?

Answer 41

9966-bp H-switch

Question 42

What is Hin invertase?

Answer 42

A site specific recombination protein -- serines recombinase

Question 43

Where are hin repeats bought together ?

Answer 43

At an enhancer region within the Hin gene

Question 44

What are Hin repeats held in place by ?

Answer 44

The Hin protein tetramer

Question 45

What cuts DNA at inverted repeats ?

Answer 45

Catalytic components of invertors

Question 46

How is the Hin invertasome formed ?

Answer 46

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

Question 47

What are HU and FIS ?

Answer 47

Architectural DNA binding proteins and are also known as KNAPs

Question 48

What does KNAP stand for ?

Answer 48

nucleate associative proteins

Question 49

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

Answer 49

Structure DNA in the nuclear site in a highly organised fashion

Question 50

What does protein HU help ?

Answer 50

Loop formation and helps tight bending in the smaller loop

Question 51

What does protein FIS do ?

Answer 51

Enhances Hin activity by stabilising correct DNA topology

Question 52

Why is the right loop larger ?

Answer 52

As it is not equidistant from the inverted repeats

Question 53

Why can the right loop form on its own ?

Answer 53

Due to the intrinsic ability of DNA to bend

Question 54

What is chemotaxis ?

Answer 54

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

Question 55

How does chemotaxis occur ?

Answer 55

Using signal transduction by a two component regulatory system

Question 56

What does the sensor protein have ?

Answer 56

A transmitter component containing a histidine residue

Question 57

What does the output protein contain ?

Answer 57

A receiver domain with a conserved aspartic acid

Question 58

What happens when a sensor receives a signal ?

Answer 58

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

Question 59

What happens after the transmitter domain becomes phosphorylated ?

Answer 59

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

Question 60

Where is the sensor histidine kinase ?

Answer 60

Embedded in the cell membrane

Question 61

What is the methyl accepting chemotactic protein ?

Answer 61

The sensor histidine kinase embedded in the cell membrane

Question 62

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

Answer 62

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

Question 63

What is a methyl accepting protein monomer composed of ?

Answer 63

Up, down up down four helical structure

Question 64

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

Answer 64

The cytoplasm

Question 65

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

Answer 65

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

Question 66

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

Answer 66

A confirmation change that precludes binding to a second site

Question 67

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 ?

Answer 67

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

Question 68

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

Answer 68

Cycles of methylation by cheR and cheD by cheBs by MCPs

Question 69

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

Answer 69

The alpha helical bundles remain apart and cheA remains inactive

Question 70

What happens when methyl accepting protein attractants are absent ?

Answer 70

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

Question 71

What happens when cheA is active and phosphorylated ?

Answer 71

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

Question 72

What does phosphorylated cheY do ?

Answer 72

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

Question 73

What does cheY become dephosphorylated by ?

Answer 73

CheZ and the system is reset

Question 74

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

Answer 74

Conserved cytoplasmic domains