Lecture 6. Bacterial Motility, Introduction To Pili/Fimbriae

Question 1

What does monotriochous mean?

Answer 1

One flagellum

Question 2

What is an example of a monotriochous bacteria?

Answer 2

Vibrio cholerae

Question 3

What does amphitrichous mean?

Answer 3

One flagellum at both ends

Question 4

What is an example of an amphitrichous bacteria?

Answer 4

Campylobacter jejuni

Question 5

What does lophotrichous mean?

Answer 5

Multiple flagella at both ends

Question 6

What is an example of a lophotrichous bacteria?

Answer 6

Helicobacter pylori

Question 7

What does petrichous mean?

Answer 7

Multiple flagella all around bacteria

Question 8

What is an example of a petrichous bacteria?

Answer 8

E. coli

Question 9

What is the motility pattern in bacteria?

Answer 9

Alternating between “run” and “tumble”

Question 10

In terms of bacteria motility, what does “run” mean?

Answer 10

Motor rotates anti-clockwise, flagellar filaments (with left-handed helices) form bundle and propel cell

Question 11

In terms of bacteria motility, what does “tumble” mean?

Answer 11

Quick reversal of motor to clockwise rotation, produces
twisting force that transforms flagella into a right-handed helix

Question 12

What does aerotaxis mean?

Answer 12

Movement usually towards oxygen

Question 13

What does chemotaxis mean?

Answer 13

Movement usually towards nutrients but also away from toxins

Question 14

What does magnetotaxis mean?

Answer 14

Movement along lines of magnetism

Question 15

What does phototaxis mean?

Answer 15

Movement towards light

Question 16

What occurs in chemotaxis?

Answer 16

Bacteria sense changes in nutrient concentration in environment through a set of transmembrane proteins known as methyl-accepting chemotaxis proteins (MCP)
These proteins interact with cytoplasmic proteins which dictates run or tumble

Question 16

What does MCP interact with?

Answer 16

Sensor kinase CheA, which can autophosphorylate
Attractant: decrease in CheA-℗
Repellent: increase in CheA-℗

Question 17

How does the motor switch in the flagellum?

Answer 17

CheA-℗ phosphorylates CheY
Only CheY–℗, not CheY, can bind to flagellar motor
CheY-℗ binding effects change from CCW to CW rotation – bacterium tumbles

Question 18

What dephosphorylates CheY–℗, allowing the CCW motion to resume?

Answer 18

CheZ

Question 19

How does a bacteria adapt to attractant?

Answer 19

Over time cell integrates attractants/repellants signal via
methylation of MCP
CheR constantly methylates MCP
Fully methylated MCP is insensitive to attractant

Question 20

What occurs in low attractant concentrations? (high CheA-℗, high CheB-℗)

Answer 20

Demethylation of MCP, increasing sensitivity to attractant (longer runs)

Question 21

What occurs in high attractant concentrations? (low CheA-℗, low CheB-℗)

Answer 21

High methylation level of MCP, decreasing sensitivity to attractant, increasing autophosphorylation of CheA (more likely to tumble)
Used to stay in a “good” environment

Question 22

What is CheB?

Answer 22

A methylesterase, is phosphorylated by CheA–℗
Increases methylesterase activity and demethylation of MCP

Question 23

How does F. johnsoniae glide?

Answer 23

Latex spheres added to F. johnsoniae bind to and are rapidly propelled along cells
Suggests that adhesive molecules move laterally along the cell surface during gliding

Question 24

What is required for gliding?

Answer 24

Gld genes 3 Gld proteins are components of an ATP-binding-cassette (ABC) transporter 5 Gld proteins are lipoproteins in the cytoplasmic membrane or outer membrane Disruption of gld genes results in loss of motility

Question 25

How does twitching motility occur?

Answer 25

Based on type IV pili first extending from cell surface then being retracted, dragging cell along surface Powered by ATP hydrolysis and retraction proteins control direction of movement

Question 26

What are gas vesicles?

Answer 26

Protein vesicles that contain gas, which confers buoyancy to the cell Allow cells to float up to oxygenated water or towards the light Can be involved in vertical migration in aquatic systems such as lakes Found in planktonic bacteria (e.g cyanobacteria) and some archaea

Question 27

What are fimbriae/pili?

Answer 27

Surface appendages, multi-subunit proteins that are not flagella Implicated in host–pathogen interactions, colonisation, host and tissue specificity (tropism), biofilm formation Specialised pili involved in genetic exchange between bacteria

Question 28

How many groups of pili are there?

Answer 28

7

Question 29

What are the most important pili types?

Answer 29

Type I and type IV

Question 30

What are fimbriae involved in?

Answer 30

Bacterial adhesion to surfaces in nature Major determinants of bacterial virulence Sometimes aid resistance to immune cell phagocytosis