Biofilms as complex fluids

Wilking, James N.; Angelini, Thomas E.; Seminara, Agnese; Brenner, Michael P.; Weitz, David A.

doi:10.1557/mrs.2011.71

Cited by 222 publications

(246 citation statements)

References 72 publications

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“…[1][2][3] Action potentials, osmotic flows, energy transduction, 4 and the stabilization of proteins are driven by ion concentration gradients across liquid films on hydrophobic biomaterials. 3,[5][6][7][8][9][10] Recent experiments in our laboratory revealed that ions interact specifically at the prototype airwater interface over separations that vastly exceed the range of direct electrostatic forces in any dielectric medium. 11 Such long-range specific ion effects (LR-SIE) may be triggered by electrostatic and electrodynamic forces, but it is obvious that they must be powered by other mechanisms, such as the thermal fluctuations intrinsic to fluid interfaces.…”

Section: Introductionmentioning

confidence: 99%

Long-range specific ion-ion interactions in hydrogen-bonded liquid films

Enami

Colussi

2013

The Journal of Chemical Physics

102

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Anions populate fluid interfaces specifically. Here, we report experiments showing that on hydrogenbonded interfaces anions interact specifically over unexpectedly long distances. The composition of binary electrolyte (Na + , X − /Y − ) films was investigated as a function of solvent, film thickness, and third ion additions in free-standing films produced by blowing up drops with a high-speed gas. These films soon fragment into charged sub-micrometer droplets carrying excess anions detectable in situ by online electrospray ionization mass spectrometry. We found that (1) the larger anions are enriched in the thinner (nanoscopic air-liquid-air) films produced at higher gas velocities in all (water, methanol, 2-propanol, and acetonitrile) tested solvents, (2) third ions (beginning at sub-μM levels) specifically perturb X − /Y − ratios in water and methanol but have no effect in acetonitrile or 2-propanol. Thus, among these polar organic liquids (of similar viscosities but much smaller surface tensions and dielectric permittivities than water) only on methanol do anions interact specifically over long, viz.: r i − r j /nm = 150 (c/μM) −1/3 , distances. Our findings point to the extended hydrogenbond networks of water and methanol as likely conduits for such interactions. © 2013 AIP Publishing LLC. [http://dx

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Section: Introductionmentioning

confidence: 99%

Long-range specific ion-ion interactions in hydrogen-bonded liquid films

Enami

Colussi

2013

The Journal of Chemical Physics

102

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“…The principles of soft condensed matter physics can be applied to understanding how bacterial aggregates form; cultures of non-motile bacteria are effectively colloidal dispersions, and many mechanisms that underlie the stability of colloidal dispersions will be relevant to bacterial cultures [17]. Polymers can contribute to the destabilization of colloidal dispersions via two generic mechanisms: polymer bridging and depletion attraction.…”

Section: Introductionmentioning

confidence: 99%

Aggregation by depletion attraction in cultures of bacteria producing exopolysaccharide

Dorken

Ferguson

French

et al. 2012

J. R. Soc. Interface.

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In bacteria, the production of exopolysaccharides-polysaccharides secreted by the cells into their growth medium-is integral to the formation of aggregates and biofilms. These exopolysaccharides often form part of a matrix that holds the cells together. Investigating the bacterium Sinorhizobium meliloti, we found that a mutant that overproduces the exopolysaccharide succinoglycan showed enhanced aggregation, resulting in phase separation of the cultures. However, the aggregates did not appear to be covered in polysaccharides. Succinoglycan purified from cultures was applied to different concentrations of cells, and observation of the phase behaviour showed that the limiting polymer concentration for aggregation and phase separation to occur decreased with increasing cell concentration, suggesting a 'crowding mechanism' was occurring. We suggest that, as found in colloidal dispersions, the presence of a non-adsorbing polymer in the form of the exopolysaccharide succinoglycan drives aggregation of S. meliloti by depletion attraction. This force leads to self-organization of the bacteria into small clusters of laterally aligned cells, and, furthermore, leads to aggregates clustering into biofilm-like structures on a surface.

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“…embedded in a hydrated polymeric mesh [90]. If the volume fraction φ occupied by the cells is high, greater than roughly 0.2-0.5, the mechanical response will be dominated by steric hinderance acting between the stiff cell walls, and an analogy with colloidal systems is possible [102]. More commonly, however, φ ≪ 1 and the response is determined by the interdispersed matrix which reacts via purely physicochemical mechanisms on times scales shorter than the cells' metabolic response.…”

Section: Molecular Origins Of Biofilm Mechanicsmentioning

confidence: 99%

“…The primary distinction from a recent review [39] is the focus here on constitutive modelling following an approach common to soft matter systems, i.e. solutions of macromolecules such as colloids, flexible and semi-flexible polymers, which have been recognised as an abiotic counterpart of biofilms with regards mechanical response [102]. A pragmatic benefit of deriving and validating quantitative models is their predictive capability, which can be used to guide the design of novel technologies targeting reduced biofilm-related infections, for instance water lines that minimise microbial spread.…”

Section: Introductionmentioning

confidence: 99%

Biomechanical Analysis of Infectious Biofilms

Head

2016

Biophysics of Infection

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The removal of infectious biofilms from tissues or implanted devices and their transmission through fluid transport systems depends in part of the mechanical properties of their polymeric matrix. Linking the various physical and chemical microscopic interactions to macroscopic deformation and failure modes promises to unveil design principles for novel therapeutic strategies targeting biofilm eradication, and provide a predictive capability to accelerate the development of devices, water lines etc. that minimise microbial dispersal. Here our current understanding of biofilm mechanics is appraised from the perspective of biophysics, with an emphasis on constitutive modelling that has been highly successful in soft matter. Fitting rheometric data to viscoelastic models has quantified linear and non-linear stress relaxation mechanisms, how they vary between species and environments, and how candidate chemical treatments alter the mechanical response. The rich interplay between growth, mechanics and hydrodynamics is just becoming amenable to computational modelling and promises to provide unprecedented characterisation of infectious biofilms in their native state.

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Biofilms as complex fluids

Abstract: Abstract

Cited by 222 publications

References 72 publications

Long-range specific ion-ion interactions in hydrogen-bonded liquid films

Long-range specific ion-ion interactions in hydrogen-bonded liquid films

Aggregation by depletion attraction in cultures of bacteria producing exopolysaccharide

Biomechanical Analysis of Infectious Biofilms

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