LectSlides_QuorumSensing_1

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Unformatted text preview: Mul$cellular
Behavior
by
 Bacteria
 Bacterial
Communica$on
Regulates:
 Virulence
 Extracellular
Enzyme
Produc$on
 An$bio$c
Produc$on
 Cellular
Differen$a$on
 Gene$c
Exchange
 General
Mechanisms
for
Cell‐Cell
Signaling
 Signaling through direct cell-cell contact. Signaling through secreted extracellular factors. secreting cell target cell secreting cell = target cell Quorum
Sensing
 Monitoring
Popula$on
Density
 What
Benefit
Does
Quorum
Sensing
 Provide?
 Model
1:
"Economies
of
scale"
 What
Benefit
Does
Quorum
Sensing
 Provide?
 Model
2:
Diffusion
Sensing
 Slow
Rate
of
Diffusion
 Fast
Rate
of
Diffusion
 Quorum
Sensing
Was
First
Described
For
the
Marine
 Bacterium
Vibrio
fischeri
 Light
organ:
 high
cell
density
 light
produc$on
 Euprymna
scolopes
 Work
of
Nealson,
Has$ngs,
and
others.
 Open
ocean:
 low
cell
density
 no
light
produc$on
 Expression
of
Light
by
V.
fischeri
was
 unusual
 Models
for
Regula$on
of
Light
 Produc$on
by
V.
fischeri
 Model
1:
The
cells
secrete
an
inducer
that
had
to
 reach
a
cri$cal
concentra$on
before
ac$va$ng
light
 produc$on.
 Model
2:

The
cells
had
to
remove
an
inhibitor
from
 the
medium
before
light
produc$on
could
be
 expressed.


 Experiment
to
Test
Whether
V.
fischeri
 Condi$ons
the
Growth
Medium
 Cells
Grown
in
Condi$oned
Medium
Induce
 Light
Produc$on
at
a
Low
Cell
Density
 condi$oned
 medium
 fresh
 medium
 Experiment
to
Determine
Whether
Medium
Was
 Condi$oned
by
Accumula$on
of
an
Inducer
or
Removal
 of
an
Inhibitor
 An
Acyl‐Homoserine
Lactone
Mediates
Quorum
 Sensing
By
V.
fischeri

 Iden$fica$on
of
How
the
Acyl‐HSL
 Regulated
Light
Produc$on
 Phenotype
of
Lux
Mutants
 1000 1000 OD -1 600 WT
 LU ml 800 -1 1200 400 200 LuxC‐
+/‐
HSL
 0 0.1 1 WT
 800 600 400 LuxR‐
+/‐
HSL
 200 0 10 0.01 0.1 OD -1 1200 1000 800 LuxI‐
+
HSL
 600 WT
 400 LuxI‐
‐
HSL
 200 0 0.01 1 OD600 (cell density) OD600 (cell density) -1 0.01 LU ml LU ml-1 OD-1 1200 0.1 1 OD600 (cell density) 10 10 Mechanism
Of
Gene
Regula$on
By
the
Acyl‐ Homoserine
Lactone
 transcrip$on

 ac$vator
 Processes
Regulated
by
Acyl‐Homoserine
Lactone
 Mediated
Quorum
Sensing
 Disease
produc$on
in
plants
 
Erwinia
caratovora
 
 
 
 
Agrobacterium
tumefaciens
 
 
 
 
Pantoea
stewar<i
 Disease
produc$on
in
animals 
Pseudomonas
aeruginosa
 
 
 
 
Burkholderia
cepacia
 Disease
suppression
in
plants 
Pseudomonas
aureofaciens
 An$bio$c
produc$on 
 
Erwinia
caratovora
 
 
 
 
Rhizobium
leguminosarum
 
 
 
 
Pseudomonas
aureofaciens
Biofilm
forma$on 
Pseudomonas
aeruginosa
 
 
 
 
Burkholderia
cepacia
 DNA
transfer
 
 
Agrobacterium
tumefaciens
 
 
 
 
Rhizobium
leguminosarum

 
 Acyl‐Homoserine
Lactone
Mediated
Quorum
Sensing
 Is
Conserved
Among
the
Proteobacteria
 From
“Brock
Biology
Of
Microorganisms”
10th
edi$on
 Pep$des
Mediate
Quorum
Sensing
By
Gram‐Posi$ve
 Bacteria
 Ala‐Asp‐Pro‐Ile‐Thr‐Arg‐Gln‐Trp‐Gly‐Asp
 Geranyl
group
 ComX
Pheromone
of
Bacillus
sub<lis
 ComX
Pheromone
Of
Bacillus
sub<lis
Facilitates
Gene$c
 Exchange
 DNA Chromosome Gene$cally
Competent
Cell
 Expression
of
a
Gene$c
Competence
Gene
Is
 Higher
at
High
Cell
Densi$es
 Iden$fica$on
of
the
Gene$c
Competence
 Inducing
Factor

 Mass
spectrometry
‐
one
compound
 Protease
treatment
‐
loss
of
ac$vity
 Amino
acid
sequencing
‐
 
A‐D‐P‐I‐T‐R‐Blank‐G‐D
 Blast
sequence
 A-D-P-I-T-R-Q-W-G-D comQ comP comX comA Iden$fica$on
of
the
Gene$c
Competence
 Inducing
Factor

 Synthe$c
Pep$de
 A‐D‐P‐I‐T‐R‐Q‐W‐G‐D
 • 
mass
spectrometry
‐
71
Da
smaller
than
purified
factor
 • 
ac$vity‐
does
not
induce
expression
of
competence
genes
 • 
ComX‐
mutant
‐
does
not
have
the
competence
inducing
factor
in
CM
 Conclusions:
The
inducing
factor
is
derived
from
comX.

The
inducing
factor
is
the
10
 amino
acid
pep$de
with
a
modifica$on
on
the
tryptophan.




 The
Genes
Downstream
of
comX
Are
Involved
in
 Response
to
ComX
Pheromone
 A-D-P-I-T-R-Q-W-G-D comQ comP comA comX his$dine
protein

 kinase
 response

 regulator
 Two‐component
regulatory
system
 Mechanism
By
Which
ComX
Pheromone
Mediates
 Quorum
Sensing
 ComX Pheromone membrane P receptor Pheromone precursor transcription activator P genes genetic competence Processes
Regulated
By
Pep$de
Mediated
Quorum
 Sensing
 Gene$c
Exchange

 
Bacillus
sub<lis 
 
 
 
 
Streptococcus
pneumoniae
 
 
 
 
Streptococcus
mutans
 Disease
produc$on
in
animals 
Staphylococcus
aureus
 An$bio$c
produc$on 
 
Bacillus
sub<lis
 
 
 
 
Lactobacillus
plantarum
 
 
 
 
Lactobacillus
sake
 
 
 
 
Carnobacterium
pisciola
 Biofilm
forma$on
 
Streptococcus
mutans
 
 ...
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