Quorum Sensing

Question 1

Bacteria communicate by…to…and reveal..
They release the chemicals and when…builds up to…a…which

Answer 1

Chemicals
Distinguish species
Friend from enemy
The level
Critical, specific
Signal transmitted to the cell
Alerts that they reached a quorum

Question 2

After reaching a quorum the population acts as….carrying tasks..
Controls behaviours from..and…and..and..

Answer 2

Large coordinated group
Thats would be unsuccessful alone
Symbiosis
Virulence
Biofilm
Natural product production

Question 3

Why disrupt quorum sensing
Why promote it

Answer 3

Stop harmful bacteria
Valuable products

Question 4

Quorum sensing relies on…,…,..of extracellular molecules called
Sensed by …
Activates gene expression when

Enables bacteria to alter behaviour in response to…changes in neighbour community

Answer 4

Detection, production, group wide response
Autoinducers
Receptor protein
Reaching a quorum

Population density, species composition

Question 5

Symbiosis in marine life

Answer 5

V.fischeri bacteria and hawaiian bobtail squid, allows bacteria to grow to a quorum when wanting to hide from predators so they emit light that counter illuminates moonlight

Question 6

The more the cells the more the..
At a particular…indicative of their number bacteria change..

Answer 6

Inducers
Concentration
Their gene expression

Question 7

Quorum sensing steps

Answer 7

Production of autoinducers
Release of autoinducers actively or passively
Recognition of autoinducers by receptor proteins when they reach a threshold conc
Change in gene expression

Question 8

Classes of autoinducers

Answer 8

Intra species, one species
Intra genera, one genus
Inter species, gram negative or gram positive

Question 9

Quorum sensing indicates ..and..

Answer 9

Number
Species relatedness

Question 10

Quorum sensing systems

Answer 10

Gram negative&raquo_space; luxl/ luxR
Gram positive» peptide signals, two component signal transduction
Vibrio harveyi» AHL, two component signalling (multiple autoinducers)

Question 11

v.fischeri is..

Answer 11

gram negative

Question 12

V. fischeri quorum sensing

Answer 12

LuxI and LuxR
LuxI is the protein responsible for autoinducer production
LuxR is the protein necessary for detecting and responding

autoinducer (AHL)

Question 13

AHL stands for

Answer 13

acylated homoserine lactone

Question 14

why no cross talking in gram negative

Answer 14

each species has its own AHL differing slightly in the left carbon chain so only it can respond to it.

Question 14

steps for gram negative

Answer 14

lux L synthesis, autoinducers accumulate till quorum is reached , sensed by lux R
lux R- AHL complex is an activator binding to a promotor to turn on xyz genes

Question 15

Gram positive quorum sensing

Answer 15

peptide autoinducer and 2 component adaptive response circuit

Question 15

the 2 component circuit is composed of

Answer 15

membrane bound protein kinase, initiates information transfer by autophosphorylation

response regulator protein, controls transcription of target genes

Question 16

autoinducers in gram positive can be

Answer 16

naked peptides or peptides with moieties

Question 16

steps for gram positive

Answer 16

1.The peptide signal precursor locus is translated into a precursor protein, which is
subsequently cleaved to produce the peptide signal

2.peptide signal accumulates extracellularly till quorum

3.Detection occurs via a two-component
signal transduction circuit

4.phosphorylation “Activation” of a
response regulator protein,
bind promoter DNA and regulate
transcription of target genes (xyz).

Question 16

v.harveyi is

Answer 16

gram negative bacteria but with multiple autoinducers

has AHL and 2 component circuit and non AHL autoinducer

Question 17

Is gram + quorum sensing species specific?

Answer 17

yes

Question 18

v.harveyi systems

Answer 18

System 1: AHL autoinducer-1
AI-1 and Sensor 1 (LuxN)
System 2: non AHL autoinducer
AI-2 and Sensor 2 (LuxPQ)

both to protein called ‘‘LuxU’’ then LUX O then LUX R

Question 19

genes regulated by v.harveyi

Answer 19

CDABE operon

Question 20

examples for bacteria and their response after quorum sensing

Answer 20

Vibrio fischeri: Bioluminescence
Pseudomonas aeruginosa: Virulence Factors, Biofilm
Agrobacterium tumefaciens: Mating, Transfer of Mobile DNA
Erwinia carotovora: Virulence Factors, Antibiotic Synthesis

Question 21

Quorum Quenching

Answer 21

It is the inhibition of quorum sensing using chemical or enzymatic means to
counteract behaviors regulated by quorum sensing.
It interferes with the signaling mechanisms and
shuts down genes

Question 22

Strategies for Quorum Quenching

Answer 22

1.Inhibition of signal molecule synthesis
2.Degradation of signal molecules
3.Competitive inhibition in the combination of signal
molecules and receptors

Question 23

degradation of signal molecules

Answer 23

high temp/high pH/ lactonases enzymes all cause lactonolysis

Question 24

signal molecule synthesis inhibition

Answer 24

(AHLs) substrates
are S-adenosyl methionine (SAM) and AcylAcyl carrier proteins (acyl-ACP)
their analogues can be used

Question 25

example for signal degredation

Answer 25

plants infected by
E. carotovora increase the pH at the site of infection

AiiA enzyme produced by Bacillus species.

Question 26

Competitive inhibition

Answer 26

analogues of inducer molecules and thus directly
bind the signal receptor.

4-nitro-pyridine-N-oxide (4-NPO) from garlic extract.

Question 27

The applications
food and environment

Answer 27

Food>Increasing the shelf
life >counteract food spoilage >Quorum quenching against pathogens

Environment>Bioremediationbiodegradation, biosorption>Quorum sensing>degrade wastes,
remediate the polluted
environment

Question 28

applications agriculture and medicine

Answer 28

Agriculture>Enhancement in yield and quality of agricultural products>, plant disease control> Quorum quenching> lactonases enzymes

Medicine>Attenuate virulence and prevent microbial infections > Lactonases as anti-virulence, antibiofilm agents>AiiA,
AiiM> quorum quenching>