Lecture 22 -- Intercellular Communication

Question 1

List three reasons bacteria use intercellular communication

Answer 1

• biofilm formation
• swarming
• infection of a host

Question 2

What is the main form of intracellular communication

Answer 2

second messengers

Question 3

what is the main form of intercellular communication

Answer 3

quorum sensing (using small diffusible signal molecules that travel in the environment)

Question 4

What are the four factors that make a good system for transmitting information

Answer 4

• transmittable signal
• receptor
• signal specificity
• signal decay

Question 5

Which signal molecules are found in gram-negatives and control their own synthesis

Answer 5

acyl homoserine lactones

Question 6

what signaling molecule is mainly found in gram positives with peptides that can be modified and ribosome-dependent synthesis

Answer 6

oligopeptide molecules (AIP)

Question 7

What is a universal signaling molecule found in Gram-negatives for interspecies cross-talk

Answer 7

A12

Question 8

What has long hydrocarbon chains with COOH at the ends whose different structures are responsible for differences in specificity

Answer 8

diffusible signal factors (DSF)

Question 9

LuxR-Luxl are a family of what kind of regulators

Answer 9

• cell-density responsive trancriptional regulators

- they provide an effective way for bacteria to take census of their numbers

Question 10

the regulation of gene expression based on the concentration of autoinducer signal molecules, which is a function of bacterial cell population and environment

Answer 10

quorum sensing

Question 11

where are the components of AHLs derived from

Answer 11

• acyl chain from Fatty Acid Synthesis pathway
• homoserine lactone from SAM
• one enzyme performs acylation and lactonization steps

Question 12

which parts of AHL signal molecules are conserved and which are variable

Answer 12

head group is conserved (homoserine lactone)

tail is variable (acyl)

Question 13

list factors that determine the specificity of AHLs

Answer 13

• chain length
• oxidation state
• degree of saturation

Question 14

what do the lux genes do

Answer 14

they catalyze the luciferase reaction to oxidize RCHO

Question 15

name the model organism for studying biofilms, its Gram orientation, its shape, and a disease it is found in

Answer 15

pseudomonas aeruginosa

gram-negative, rod-shaped, cystic fibrosis

Question 16

List the four molecules involved in quorum sensing for p. aeruginosa

Answer 16

1. HQNO (cytochrome inhibitor)
2. Rhamnolipid (a surfactant)
3. Pyocyanin (redox active compound)
4. Cyanide (cytochrome inhibitor)

Question 17

What molecules are LuxR-type receptor homologs that are good for listening and for mixed species quorum sensing

Answer 17

orphan receptors

Question 18

What is AI-2 formed from and what intermediate is toxic

Answer 18

SAM and SAH

Question 19

How can signals be produced in gram positive bacteria

Answer 19

• directly secreted

- produced by the action of proteases

Question 20

How can signals be received in gram-positive bacteria

Answer 20

• through sensor-response regulator systems

- by import into the cell followed by binding to intracellular effectors

Question 21

what is the function of lactonase in AHL inhibition

Answer 21

opens ring

Question 22

what is the function of acylase in AHL inhibition

Answer 22

cleaves amide bond

Question 23

which of the two enzymes involved in AHL inhibition act reversibly and which act irreversibly

Answer 23

AiiA lactonase = reversible in presence of HCl

acylase = not reversible

Question 24

what are the names for signal mimics that can inhibit and induce quorum sensing, respectively

Answer 24

• antagonists

- agonists