Lecture 4: Cell-Cell Communication & Development in Bacteria

Question 1

What does a bacteria need in order for a signal to be detected and transduced?

Answer 1

Signal Receptor

Signal Transduction Apparatus

Question 2

Define Cheating

Answer 2

Bacteria makes a signal itself

This can lead to extinction

Question 3

Examples of behaviours controlled by quorum sensing

Answer 3

Bioluminescence
Biofilm formation
Conjugation
Virulence

Question 4

Define bioluminescence, biofilm formation, conjugation and virulence

Answer 4

Bioluminescence - in some bacteria
Ex) Aliivibrio fischeri, generate light

Biofilm formation - transition from planktonic , free swimming, to community based lifestyle

Conjugation - DNA transfer one bacterium to another
Ex) Gram-pos Enterococcus

Virulence - occurs when large number of bacteria is needed to establish successful infection

Question 5

Explain 5 steps in Virulence in Cholera

Answer 5

1. Vibrio cholerae move from lumen in small intestine to surface of microvilli
2. Use Type 6 Secretion System to target and kill gut bacteria
3. Signals from microvillus environment induce expression of Toxin Co-regulated Pili (TCP)
   - > TCP anchors V.cholerae cells to host surface and biofilm begins to form
4. V. cholerae cells produce and export cholera toxin (CT)
5. CT disrupts metabolism of human cells, cause increase production of cAMP, rise in cAMP concentration triggers loss of water and electrolytes in gut

Question 6

Why is chitin important?

Answer 6

It is a molecular signal in lifestyle of V. cholerae bacterium
Chitin and bacteria population density control the bacterium behaviour

Question 6

Why is chitin important?

Answer 6

It is a molecular signal in lifestyle of V. cholerae bacterium
Chitin and bacteria population density control the bacterium behaviour

Question 7

What is Type 6 Secretion System?

Answer 7

T6SS - a weapon designed to kill other bacteria

Uses spring loaded mechanism

Question 8

Name and describe the 3 types of Horizontal Gene Transfer

Answer 8

Transduction - bacteriophage mediates transfer process following attachment to bacterial surface

Transformation - Naked DNA taken up from external environment by bacteria that are ‘competent’ for transformation

Conjugation - plasmid mediates own transfer between cells, encoding machinery for transfer in own genome

Question 9

Describe Generalised Transduction

Answer 9

*Bacteriophage injects genetic material into cell
*Goes through replication and destroys host genome in process
*Packages DNA randomly into newly formed phage heads
-> random pieces of bacterial DNA packaged into phage by
headful packing
*New virus capsule that contains part bacterial DNA infects another bacterial cell when bacterial DNA packaged into virus is inserted into recipient

Question 10

Describe Specialised Transduction

Answer 10

*Bacteriophage injects genetic material
*Gets inserted into genome - into sites which possess some
homology to viral genetic material
*Usually resides here and replicates along bacterial chromosome
*Rare occurrence when becomes excised from genome along some
bacterial DNA and packed into phage head - cycle repeats
*Bacterial genome is NOT destroyed

Question 11

What is Type 4 Secretion System?

Answer 11

Responsible for physical transfer of genetic material between cells

Question 12

What is the restriction-modification system?

Answer 12

‘self’ DNA has ‘approved’ methylation pattern and not digested
‘non-self’ DNA lacks ‘approved’ methylation pattern and is digested