Lecture 9 Flashcards Preview

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Flashcards in Lecture 9 Deck (14):
1

How might a bacterial communication system work?
- where does the signal come from
- type of molecule
- detection
- regulatory mechanism
- why would the population's gene expression shift at the same time?
(4)

Signal genes and transporter genes activate response genes, via various methods.
- Feedback regulation
- Two component system
- Quorum sensing
- Self-regulated positive feedback mechnanisms

2

In feedback regulation, where does the signal come from?

From the cells, so the signal becomes a measure of the number of cells and the density of cells.

3

In feedback regulation, how is the signal made?

Could be a product of the cell, made via an enzyme pathway within the cell.

4

How would the signal in a feedback regulation mechanism be exported from the cell?

Via carrier proteins in the cell membrane.

5

When lambda is moving toward lysogeny what does the repressor do?

It activates its own expression, pushing itself further toward the pathway producing it.

6

What is quorum sensing (QS)?
(2)

- A form of density-dependent bacterial cel-cell communication mediating coordinated population-wide changes in gene expression.
- Associated with virulence, biofilm formation, sporulation, antibiotic production, bioluminescence.

7

What is a biofilm?

- A population of bacteria on an object that adhere and grow into a population that change gene expression as the population grows.

8

What is bioluminescence? eg) in Vibrio fischeri

- Vibria fischeri is a gram-negative marine bacterium
- They use ATP in the form of luciferase to form light.
- Often found in symbiosis with fish or squid, in order to find food, avoid predation, or find mates.

9

Luciferase bioluminescence gene expression is a positive regulatory mechanism:

- luxR makes a signal that binds to a regulator, activating expression of luxl
- luciferase genes produce luciferase proteins which produce light
- luxl is a gene which makes an enzyme which makes a small MW signal that is exported from the cell

10

What is the signal used in luciferase bioluminescence?

- acyl-homoserine lactone
- with a R group that varies between organisms
- lipid-like so they can diffuse across membranes

11

What are biofilms eg) Pseudomonas aeruginosa

An opportunistic pathogen that attaches to plastics and metals (especially in a hospital setting) forming micro-colonies, and with quorum sensing mature into a biofilm community.

12

What quorum sensing mechanism does pseudomonas aeruginosa use for biofilm generation?

- LasI produces a signal which binds to
- LasR the early infection genes regulator.
- The early infections genes produced bind to RhII which binds to
- RhIR, the late infection genes regulator

13

Two component feedback system eg) staphylococcus aureus

- A gram-positive bacteria, with a gene encoding the inducer peptide.
- These peptides are transported out of the cell, circularising the ends of them (AIP + signal).
- The circularised peptides are more stable.
- A two component system causes a cascade of gene expression to be induced.

14

Interspecies communication via quorum sensing uses:

- good for anti-microbial agent targets, use of an antagonist and an autoinducer.