Lecture3:BacterialSwimming
• Introduc6on• Bacterialswimming• Nearsurfaceaccumula6on• Circulartrajectoriesnearinterface• Trappingofswimmingbacteriaattheair-waterinterface
Jay X Tang, Brown University 1
Abundanceofmicrobesattheinterface
Biofilm: Bacteria mats near Grand Prismatic Spring in Yellowstone � www.wikipedia.org
Steps flagellated bacteria take to form biofilm Watnick and Kotler, 2000.
Jay X Tang, Brown University 2
Various species of motile bacteria
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Bacterialmo6ondrivenbyrota6onofflagellarmotor
Biochemistry, 3rd Ed., 1999, Voet & Voet, John Wiley & Sons
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Swimming direction
Google images
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LifecycleofCaulobactorcrescentus
Swarmercell
Stalkedcell
Yves Brun, Indiana University Jay X Tang, Brown University 5
From swimming to attachment and adhesion
• Body parts – Cell body – Flagellum – Pilli – Holdfast – Stalk
• Physics
– Swimming hydrodynamics (H. Berg, PNAS, 1995; Magariyama, BJ, 2005; G. Li & J. X. Tang, BJ, 2006; J. Hill, et al., Phys Rev Lett, 2007; G. Li & J. X. Tang, Phys. Rev. Letts., 2009)
– Electrostatics (DLVO) (Jucker et. al., 1998; Vigeant et al., App. Env Microbio., 2002; G. Li, LK Tam & J. X. Tang, PNAS, 2008)
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Areversiblemotorpowersbacterialswimming
Biochemistry, 3rd Ed., Voet & Voet, John Wiley & Sons
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Uni-flagellatedbacteriaareefficientswimmers
C. crescentus, movies taken by Guanglai Li , Brown Univ.
G. Li & J. X. Tang, Biophys J., 2006, 91:2726G. Li, LK Tam & J. X. Tang, PNAS, 2008, 105:18355G. Li & J. X. Tang, Phys Rev Lett, 2009, 103:078101
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Theessen6alphysicsofbacterialswimming
• Theretwoessen6alproper6esofabacterialflagellum:– Arotaryflagellarmotor– Ahelicalflagellarfilament
• Thenexttwoslidesexplainthebasichydrodynamicsthatenableswimmingofflagellatedbacteria.
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Asymmetricdragandvectoranalysis
BiologicalPhysics,byPhilipNelson,2004,W.H.FreemanG.Li&J.X.Tang,PRE,2004;
G.Li,Q.Wen&J.X.Tang,J.Chem.Phys,2005
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Ahelicalpropeller
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Specifictopics• I.Nearsurfacesaccumula6on
– stericconfinement&effectsofcollision– nearsurfacedrag,lubrica6onforce
• II.Nearsurfaceswimmingpath– observa6onandanalysisofcirculartrajectories– couplingbetweenBrownianmo6onand
hydrodynamics
• ***Swimmingpathattheair/waterandoil/waterinterface– trappedatthesurface– effectsofsurfacetension,surfaceviscosity,and
hydrophobicityImplications: chemotaxis, bacterial adhesion, differentiation, biofilm formation, etc.
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TopicI.Nearsurfaceaccumula6onofmicro-swimmers
Berkeetal.2008,PhysRevLe`(Lauga)
E.coli
Rothschild,1963,Nature
Bullsperm
0 50 100 150 200
0.00
0.05
0.10
0.15
0.20
0.25
Pro
babi
lity
Den
sity
Distance (µm)
Red:Caulobacter
Li&Tang,2009,PhysRevLe`
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Visualizinghowbacteriahitasurface
Ming-ming Wu, Cornell Univ.
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Whathappensaheraswimmerhitsasurface
X
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Howfasttobecomeparalleltosurface
Vx�
Forceandtorquebalance
Hydrodynamicforceandtorqe
Results
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Simula6ngamicroswimmerconfinedinathinlayer
Equa6onsofMo6onSimplifiedModel
SimulatedPath Densitydistribu6on
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ComparisonwithExperiments
10rad2/s
10.1 0.0001
Guanglai Li & J. X. Tang, Phys Rev Lett, 2009, 103:078101Jay X Tang, Brown University 18
SummaryofTopicI
Surfacesetsini-alangle
Swimmingundertheinfluenceofrota-onalBrownianmo-on
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SpecificTopicIINearsurfaceswimmingpath
• Observa6onandanalysisofcirculartrajectories
• CouplingbetweenBrownianmo6onandhydrodynamicsImplica-onson– chemotaxis– bacterialadhesion– differen6a6on– biofilmforma6on
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Swimmingincirclesnearasurfaceboundary
Frymier,PNAS1995 Goto,Biophys.2005E.coli Vibio.alginoly<cus
C.crescentus Li,PNAS2008 H.pylori Celli,PNAS2009
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Thehydrodynamicbasisofcirculartrajectoryofnearsurfaceswimming
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Swimming direction
Dragforce
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TrajectoriesObservedbyTIRF
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ForceandTorqueAnalysis
+ + =+
dlvo(Derjaguin,Landau,VerweyandOverbeekTheory) Jay X Tang, Brown University 24
CurvatureandSwimmingSpeedvsDistance-ComparisonbetweenMeasuredandSimulatedData
MeasuredbyTIRFmicroscopy
Simulated
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RoleofBrownianMo6ononForaging
Guanglai Li, LK Tam & J. X. Tang, PNAS, 2008, 105:18355
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OpenPuzzle:Whyarecircularpathnotedonlyforbackwardswimmers?
A schematic comparison between forward and backward swimming near a surface
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SummaryofTopicII
Brownianmo-onvariesdistancetosurface
Dragsensi-vetodistance
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TopicIII:Swimmingattheair/waterinterface
MikeMorse,Huang,Li,Maxey&Tang,Biophys.J.(2013),105:21-28
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Analysisoftrajectoriesattheairsurface
Twotypesofswimmingtrajectoriesattheliquid/airinterface:~40%straightswimmers&~60%circularswimmers
10 20 30 40 50 60 70-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
Speed (µm/s)
Cur
vatu
re (1
/µm
)
-0.20-0.10
0.000.10
0.200.30
0.400.50
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09
Curvature (1/µm)
Dis
tribu
tion
Straight Swimmers ~40% Circular Swimmers
~60%
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Manipula6onofswimmingattheair/waterinterface
-0.20-0.10
0.000.10
0.200.30
0.400.50
0.000.020.040.060.080.100.120.140.160.180.20
00.00010.0010.010.050.1
Curvature (1/µm)
Dis
trib
utio
n
0 0.0001 0.001 0.01 0.05 0.10.0000
0.1000
0.2000
0.3000
0.4000
0.5000
0.6000
0.7000
0.8000
0.9000
1.0000
StraightCircular
Percent Surfactant
Fra
ctio
n of
Tra
ject
orie
s
Hypothesis: bacteria tend to get trapped at the air/water surface due to its large surface tension. Adding surfactant, which reduces the surface tension, might release them from the surface. Experiment: Add Triton, a non-ionic surfactant and observe!
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MolecularLayerofTritonontotheSurfaceLeadstoFullReleaseofTrappedBacterialSwimmersfromtheLiquid-WaterInterface
Chemical Structure of Triton-100: Molecular weight: 625 Dalton Molecular Length: ~3 nm
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Ref for the blue curve: Danov, K.D. and P.A. Kralchevsky, Colloidal J., 2012
Swimmingcellsaretrappedattheairsurfaceofgrowthmediumbutnotminimalsaltsolu6on
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Orange data: minimal salt solution Blue data: growth medium containing Bactotrypton and Yeast Extract
Effectsofselectedorganicmaterialsingrowthmediumontrappingoftheswimmingcellsatthesurafce
Minimal salt solution 4.0+-2.4 Growth medium 59.7+-5.9 Growth medium + surfactant 6.8+-1.3
Minimal salts +Yeast Extract 15.9+-1.6 Minimal salts+Bactotrypton 25.6+-2.3
Percentage of trapped cells
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Circulartrajectoriesofoppositehandednessattheair/liquidsurface
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ContradictaryrecentreportsonE.coli• Lemelle,Pallierne,Chatre&Place,J.
Bacteriology,192:6307,2010. • CWandCCWcircles• Condi6on:growthmedium
• Leonardo,Dell’sArciprete,Angelani&
Iebba,PRL,106:038101,2011.• CWcirclesonly,oppositetonearsolidsurface
• Condi6on:mo6litybuffer
Take home message: SURFACE CHEMISTRY MATTERS
Observa6onofswimmingatthewater/oilinterface
Unpublished work-M. Morse & J. X. Tang
• Theforwardswimmersmovein-ght,clockwisecircles(radiusunder2um)
• Theytendtobeterminallytrapped
• Thestrainsthatswitchmotorrota-ondirec-onscanescapewhilebackingoff
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Flagellarmotorswitchingisafirstpassage6meprocess
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Morse, Bell, Li & Tang, Phys. Rev. Lett., 2015
ConcludingRemarks• Swimming microbes tend to accumulate near a confining surface subsequent to collision.
• The accumulation facilitates biological functions such as nutrient foraging, adhesion, and biofilm formation.
• Adsorption of large organic molecules at the air/water interface causes the swimming microbes to be trapped. The trapped swimmers can be released by surfactants, which some microbes secrete.
• Detailed experiments and analysis of low Reynold # hydrodynamics and surface physics/chemistry are required to explain various bacterial properties at interfaces. 38 Jay X Tang, Brown University
Acknowledgements• Dr.GuanglaiLi,formerpostdocandseniorassociate,Brown
University
• Collaborators:Prof.YvesBrunandassociates,IndianaUniversity;ProfsMar6nMaxeyandThomasPowers,BrownUniversity
• PhDstudents:MichaelMorse&JordanBell• Undergraduatestudents:LK Tam (Yale Univ), Lauren Francis, Robert Kim (Vanderbilt Univ.), Jesse Mahautmr, Daniel Munger, Katrina Wilson, Tatiana Lopes, James Bensson, Liana Nishimova, Serin Seckin, Athena Huang, Marianna Neubaeur, Yokun Gao, Erica Khan, Jeffrey Commons, Nathan Johnson, Sha Sha…
• FundingfromNIHandNSFPhys&NSFCBET
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KeyRefs• Li,G.,L.K.Tam,andJ.X.Tang,AmplifiedeffectofBrownianmo<onin
bacterialnear-surfaceswimming.ProcNatlAcadSciUSA,2008.105(47):p.18355-9.
• Li,G.andJ.X.Tang,Accumula<onofmicroswimmersnearasurfacemediatedbycollisionandrota<onalBrownianmo<on.PhysRevLe`,2009.103(7):p.078101.
• Morse,M.,Huang,A.,Li,G.,Maxey,M.R.,andTang,J.X.,Molecularadsorp6onsteersbacterialswimmingattheair/waterinterface,BiophysicalJournal,2013,105:21.
• Morse,M.,J.Bell,G.Li,andJ.X.Tang,FlagellarMotorSwitchinginCaulobacterCrescentusObeysFirstPassageTimeSta<s<cs.PRL,2015.115(19):p.198103.
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