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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
2
Introduction
T. Bjarnsholt, 2013
yachting-pages.com
famille-schlegel.com
CYANOBACTERIA: PRIMITIVE ORGANISMS
3
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
4
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
7
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
8
Binary imagesExperimental setup
Camera
Microfluidic Chip
250 mm
I) Experimental results
VIDEO
9
I) Experimental results
DIFFUSIVE DYNAMICS SLOWDOWN
10
Temporal evolution of the detected
number of bacteria
Bacterial transport towards the
surface via a sedimentation
process.
I) Experimental results
DIFFUSIVE DYNAMICS SLOWDOWN
11
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
12
Temporal evolution of the diffusion
coefficient
Diffusion coefficient
decreases with time
I) Experimental results
INTERMITTENT MOTILITY
13
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
11/15/2017 14
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
15/11/2017 15
II) Model
Ballistic hypothesis:
Bacteria landing
at time t’
Area covered by a
particle between t’ and t
COVERED SURFACE PROPORTION S(T)
15/11/2017 16
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)
15/11/2017 17
Glass EPS
III) Dynamics slowdown analysis
WHAT HAPPENS WITH MUTANTS ?
18
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
11/15/2017 19
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
20
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
11/15/2017 21
• Numerical computations model
Speed : 2 px/step Speed : 0.05 px/step
IV) Comparison of different surfaces
CONCLUSIONS
22
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
23
Acknowledgements
INTERMITTENT MOTILITY
24
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)
15/11/2017 25
Bhaya, et al., 2015
Golestatnian, et al.,
2015
III) Dynamics slowdown analysis
DIFFUSIVE DYNAMICS SLOWDOWN
26
Definition of the Mean Squared Displacement (MSD):
In the case of a Fickian behaviour:
I) Experimental results