DYNAMICS SLOWDOWN DURING EARLY STAGES OF BACTERIAL ...
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DYNAMICS SLOWDOWN DURING EARLY STAGES OF BACTERIAL COLONISATION Groupe Physique des Energies Laboratoire APC Université Paris Diderot Thomas Vourc’h, Julien Léopoldès, Hassan Peerhossaini
Transcript of DYNAMICS SLOWDOWN DURING EARLY STAGES OF BACTERIAL ...
DYNAMICS SLOWDOWN DURING EARLY STAGES OF BACTERIAL COLONISATION
Groupe Physique des Energies
Laboratoire APC
Université Paris DiderotThomas Vourc’h, Julien Léopoldès, Hassan Peerhossaini
MICRO-ORGANISMS SURFACE INTERACTIONS
o Biofouling
o Infections
o Food-processing industry
o Biofuel production
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Introduction
T. Bjarnsholt, 2013
yachting-pages.com
famille-schlegel.com
CYANOBACTERIA: PRIMITIVE ORGANISMS
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Introduction
Evolution of the oxygene rate in atmosphere plotted against time
o Primitive organisms, whichenabled the transition to more evolved forms of life.
Govindjee et Dimitriy Shevala,
2011
CYANOBACTERIA’S POTENTIAL
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Ducat et al., 2011
Different products from cyanobacteria
Introduction
Photosynthetic efficiency :
o Cyanobacteria : 3 – 9 %
o Average terrestrial
organisms: 0.25 – 3%
M. Brenner, 2006
G. Dismukes et al., 2008
20minutes.fr
BIOFILM FORMATION
5Different stages of biofilm formation
Introduction
C. Cassier-Chauvat
& F. Chauvat, 2015
Mantle of Exopolysaccharides
(EPS)
Typical SEM (scanning electron microscopy) images of
cyanobacterium Synechocystis sp. PCC6803
DIFFERENT KIND OF MOTILITY
6M. Mazza, Journal of Physics D: Applied Physics, 2016
Swimming motility
Swarming motility
Twitching motility
Gliding motilityD. Bhaya et al., Molecular Biology, 2000
Type IV Pili
Introduction
STUDYING DIFFUSION
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Definition of the Mean Squared Displacement (MSD):
In the case of a 2-D Fickian behaviour:
Introduction
DMSD 4)(
20)()( XXMSD
Slope :
4D
Time
MSD for simulated Brownian motionDisplacement probabilities at different
times for simulated Brownian motion
EXPERIMENTAL SETUP
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Binary imagesExperimental setup
Camera
Microfluidic Chip
250 mm
I) Experimental results
VIDEO
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I) Experimental results
DIFFUSIVE DYNAMICS SLOWDOWN
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Temporal evolution of the detected
number of bacteria
Bacterial transport towards the
surface via a sedimentation
process.
I) Experimental results
DIFFUSIVE DYNAMICS SLOWDOWN
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Definition of the Mean Squared Displacement (MSD):
In the case of a Fickian behaviour:
I) Experimental results
t
DMSD 4)(
20)()( XXMSD
DIFFUSIVE DYNAMICS SLOWDOWN
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Temporal evolution of the diffusion
coefficient
Diffusion coefficient
decreases with time
I) Experimental results
INTERMITTENT MOTILITY
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A typical trajectory of 668s duration, divided
into run and tumble periods
I) Experimental results
Experimental displacement
probabilities
Central
part
Tails
ANALYTIC FORMULA FOR THE DIFFUSION COEFFICIENT : CONTINUOUS-TIME RANDOM WALK (CTRW) MODEL
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rt
run
tt
ll
l
runl
tt
rt
Experimental
parameters
CTRW model
parameters
2
4
1 lD
Bouchaud &
Georges, 1990
II) Model
ANALYTIC FORMULA FOR THE DIFFUSION COEFFICIENT
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II) Model
Ballistic hypothesis:
Bacteria landing
at time t’
Area covered by a
particle between t’ and t
COVERED SURFACE PROPORTION S(T)
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Bhaya, et al., 2015
Golestatnian, et al.,
2015
III) Dynamics slowdown analysis
Experimental colonisation maps drawn at different experiment times
COVERED SURFACE PROPORTION S(T)
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Glass EPS
III) Dynamics slowdown analysis
WHAT HAPPENS WITH MUTANTS ?
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III) Dynamics slowdown analysis
Wild Type Cells
Mutant cells – Deficient in EPS production
EPSJittawuttipoka et al.,
2015
Decrease of the relative diffusion
coefficient with time
Mutants
Wild Type
COMPARISON OF DIFFERENT SURFACES
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Glass
PDMS
Temporal evolution of the diffusion coefficient on
glass and on a PDMS surface
IV) Comparison of different surfaces
SURFACE COLONISATION AFTER ONE WEEK OF CULTURE
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Colonisation on a glass surface:
diffusion enables an homogeneized
colonisation.
Colonisation on a PDMS surface:
adhesion leads to the formation of
numerous micro-colonies.
50 mm 50 mm
IV) Comparison of different surfaces
COLONISATION AFTER ONE WEEK: MODEL
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• Numerical computations model
Speed : 2 px/step Speed : 0.05 px/step
IV) Comparison of different surfaces
CONCLUSIONS
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o Cyanobacterium Synechocystis sp. PCC 6803 diffusive dynamics decreases with time.
o Dynamics is well described with an intermittent model.
o This decrease can be linked to a progressive surface covering with the EPS droppedby the bacteria. EPS-depleted mutants do not exhibit such a decrease.
o Early dynamics can be linked to the shape of microcolonies growing on surface.
Conclusions
ACKNOWLEDGEMENTS
Many thanks to :
o Annick Méjean
o Franck Chauvat & Corinne Cassier-Chauvat
o Mojtaba Jarrahi
o Jean-Pierre Thermeau
o Guillaume Chau, Elnaz Pashmi & Chau Minh N’guyen
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Acknowledgements
INTERMITTENT MOTILITY
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2))2/()2/(()(
tXtXtD
Temporal evolution of D (red) and
instantaneous speed (blue)A typical trajectory of 668s
duration
I) Experimental results
COVERED SURFACE PROPORTION S(T)
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Bhaya, et al., 2015
Golestatnian, et al.,
2015
III) Dynamics slowdown analysis
DIFFUSIVE DYNAMICS SLOWDOWN
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Definition of the Mean Squared Displacement (MSD):
In the case of a Fickian behaviour:
I) Experimental results
