Bulletin of the American Physical Society
71st Annual Meeting of the APS Division of Fluid Dynamics
Volume 63, Number 13
Sunday–Tuesday, November 18–20, 2018; Atlanta, Georgia
Session A22: Biological Fluid Dynamics: Biofilms and Bio-Suspensions |
Hide Abstracts |
Chair: Jian Sheng, Texas A&M University, Corpus Christi Room: Georgia World Congress Center B310 |
Sunday, November 18, 2018 8:00AM - 8:13AM |
A22.00001: Rivalry in Bacillus subtilis Colonies: Enemy or Family? Rajorshi Paul, Tanushree Ghosh, Tian Tang, Aloke Kumar A bacterial colony constitutes a complex microcosm where bacteria interact with each other and the external environment to ensure the survival of the colony. Two adjacent Bacillus subtilis colonies growing on a nutrient rich agar plate have been found to exhibit two distinct interactions: they either coalesce as they grow or form an interface at the colony fronts without complete coalescence. The nature of interaction has been found to be dependent on the agar concentration (C) in the growth medium and the initial separation between the colonies (d). Interactions of a colony with solid structures and liquid drops have indicated that biochemical rather than physical factors are responsible for the interface formation. A simple mathematical model has been formulated to numerically simulate the two interaction patterns. The model predicts the nature of interaction for the given combination of C and d. The model prediction agrees well with experimental findings and generates a C-d phase diagram containing coalescence and interface regimes. The study provides valuable insights into the dynamics of bacterial colonies, especially when multiple colonies interact with each other. |
Sunday, November 18, 2018 8:13AM - 8:26AM |
A22.00002: Mesoscopic Turbulence in Exotic Active Emulsions Livio Nicola Carenza, Luca Biferale, Giuseppe Gonnella Constituents of active matter inject energy in their surroundings, on scales much smaller than the system size, thus keeping the system far from thermodynamic equilibrium. Many examples of active matter evolve in the low Reynolds number regime, such as suspensions of bacteria or microtubules bundles. It is somehow surprising that this kind of systems exhibit a behavior reminescent of inertial turbulence. In this work we present results of an in silico study for a binary fluid, made of a polar active component and an isotropic passive solvent in presence of a surfactant favouring emulsification of the two phases. The present model allows for the confinment of the turbulent behavior by triggering the typical size of active domains, i.e. the characteristic lengthscales of energy injection. We show that energy spectra exhibit power-law scaling in the high-wavenumber regime, only in a peculiar region of the parameter space. In particular exponents exhibit a strong dependence both on the active fraction and on the strength of active doping. These features arise due to a non-trivial hydrodynamics coupling between the liquid-crystal phase and the underlying fluid, thus causing the transfer of energy between different lengthscales. |
Sunday, November 18, 2018 8:26AM - 8:39AM |
A22.00003: Characterization of drag mechanisms over biofilm Elizabeth Callison, Joel D Hartenberger, Andrew J Uggeri, James W Gose, Marc Perlin, Steven Louis Ceccio Soft biofilms can form at flow boundaries, producing increased friction drag and adversely affecting the performance of hydrodynamic systems. The underlying mechanisms of drag production in soft biofilms–such as the role played by compliance, vibration of streamers, and the contribution of form drag to overall resistance–are poorly understood. To examine the drag producing flow, flat plates covered in biofilms were studied in the Skin-Friction Flow Facility at the University of Michigan. Experiments evaluating the drag produced by the live biofilm were then compared to those of solid, 3D printed, rigid replicas to differentiate the measured drag forces and their components. High-resolution, 3D rigid replicas of select cases were generated via additive manufacturing using in situ measurements of the biofilm surface profile. These measurements were accurate to 50 µm as measured by a Micro-epsilon 2900-25 laser line scanner. The hydrodynamic performance of the biofilms, grown under flow on flat plates, was determined through pressure drop measurements as well as planar particle image velocimetry. Comparisons of the resistance curves for the rigid replicas and live biofilm will be discussed and flow measurements will be presented. |
Sunday, November 18, 2018 8:39AM - 8:52AM |
A22.00004: Path to “dirty blizzard” from Deepwater Horizon deep-sea plume: Bacteria form streamers on rising oil droplets to increase drag. Andrew R. White, Maryam Jalali, Jian Sheng During the Deepwater Horizon oil spill, wellhead injection of dispersant caused a large pool of micro-droplets to be entrained in the 400 m thick deep-sea plume spanning over kilometers. The perceived fates of these droplets are metabolic degradation or sedimentation. However, both fates are contested on the grounds that droplets rise too fast to allow microbes to encounter, adhere, and grow over them to initiate biotic processes. Using a microfluidic platform capable of investigating a single oil droplet rising through a microbial suspension at ecologically relevant length (0.5um–1 mm) and time scales (1 ms–1 d) with well-controlled physicochemical environments, we found that within minutes after droplet's exposure to Pseudomonas suspensions, long polymeric streamers are extruded behind it and bundled into a large tail extending up to 10 drop diameters within hours. Flow measurements show that drag is increased by > 60% with only a few streamers. Increase in drag by streamers slows the drop and consequently lengthens its residence time to surrounding microbes. Short formation time scales compounded with impacts on hydrodynamics provide a creditable missing link in pathways to biodegradation and sedimentation, and significant implications in droplet transport models. |
Sunday, November 18, 2018 8:52AM - 9:05AM |
A22.00005: Microfluidic studies of morphological changes of crude oil microdroplets exposed to different bacteria species and consortia under different flow velocities Maryam Jalali, Andrew R. White, Jian Sheng Utilizing biodegradation for marine oil spill cleanup has gained a significant amount of attention. A deeper understanding of the oil consumption ability of different bacteria species in addition to bacteria consortia, as well as the effect of hydrodynamics on this process and oil degradation is essential. In our previous studies we determine the effectiveness of the size of the oil microdroplets on the bacteria-oil interaction and biodegradation. Additional experiments were conducted to explore the interaction of different bacteria species on stationary oil microdroplets versus microbial interaction of oil degrading consortia containing six different bacteria species. The experiments were done in a non-flow condition and various flow shears. To attain the results, we developed a micro-bioassay containing an enclosed chamber with bottom substrate printed with stationary oil microdroplets and a digital holographic interferometer (DHI). The experimental results showed the size dependence of droplets subject to biodegradation. Experiments involving bacteria isolates displayed that different bacteria species have varied appetite for oil and it is independent of motility. The experiments of consortia and various flow shears on biodegradation will be reported in details. |
Sunday, November 18, 2018 9:05AM - 9:18AM |
A22.00006: Compound Particle Model for the Microbial Degradation of Solitary Oil Microdroplets Traveling through a Water Column George E. Kapellos, Nicolas Kalogerakis, Patrick S. Doyle A compound particle model is developed for the biodegradation of oil microdroplets moving through a water column. The compound particle consists of an oily core that is successively surrounded by a bioreactive skin of negligible thickness and another bioreactive shell of finite thickness. The bioreactive skin represents a layer of superhydrophobic microbes that uptake oil directly from the oily phase, whereas the bioreactive shell represents a distinct biofilm phase. The new model accounts for all three modes of biodegradation: interfacial uptake, bioreaction in the bulk aqueous phase, and bioreaction in a biofilm formed around the droplet. Equations have been established for the determination of the droplet shrinking rate and the evolution of the compound particle dimensions as functions of the drifting speed, the microbial kinetics, the biofilm thickness, the diffusivity and solubility ratios. Numerical analysis is used to extend the domain of validity of the model by taking into account the effects of multiple oil components, oxygen limitation and biofilm erosion. Computational findings will be discussed in relation to observations from the biodegradation of hexadecane droplets by Marinobacter sp. in a microfluidic setting. |
Sunday, November 18, 2018 9:18AM - 9:31AM |
A22.00007: Growth and deformation of bacterial biofilms in fluid shear Philip Pearce, Raimo Hartmann, Praveen Singh, Rachel Mok, Boya Song, Dominic Skinner, Jorn Dunkel, Knut Drescher Bacterial biofilms are surface-associated, three-dimensional structures populated by cells embedded in matrix. In typical natural, medical and industrial contexts, biofilms are subjected to significant fluid shear, but the effect of flow on biofilm dynamics is not well understood. Combining single-cell live imaging with simulations, we characterize how hydrodynamic effects at multiple stages of growth contribute to Vibrio cholerae biofilm morphologies. Our results demonstrate that dynamics at several scales determine the architectures of biofilms in flow. |
Sunday, November 18, 2018 9:31AM - 9:44AM |
A22.00008: Acoustic confinement of Escherichia coli: The impact on biofilm formation Salomé Gutiérrez-Ramos, Ramiro Godoy-Diana, Jesús Carlos Ruiz-Suárez, Jean-Marc Ghigo, Christophe Beloin, Aimee Wessel Brownian or self-propelled particles in aqueous suspensions can be trapped by acoustic fields generated by piezoelectric transducers usually at frequencies in the megahertz. The obtained confinement allows the study of rich collective behaviours like clustering or spreading dynamics in microgravity-like conditions. The acoustic field induces the levitation of self- propelled particles and provides secondary lateral forces to capture them at nodal planes. Here, we give a step forward in the field of confined active matter, reporting levitation experiments of bacterial suspensions of Escherichia coli. Clustering of living bacteria is monitored as a function of time, where different behaviours are clearly distinguished. Upon the removal of the acoustic signal, bacteria rapidly spread, impelled by their own swimming. Trapping of diverse bacteria phenotypes result in irreversible bacteria entanglements and in the formation of free-floating biofilms. |
Sunday, November 18, 2018 9:44AM - 9:57AM |
A22.00009: Liquid plug formation in an airway closure model Francesco Romanò, Hideki Fujioka, Metin Muradoglu, James Bernard Grotberg Human lung airways are lined with a liquid made out of mucus and serous layers. In small airways, the surface tension between this liquid layer and the air can induce a Plateau-Rayleigh instability. In order to study this, we model the airway as a rigid pipe coated internally with a Newtonian liquid. Our numerical simulations are based on the VOF method, employed to simulate the interfacial instability from initiation to coalescence and plug formation. This event closes the airway. Our parametric study considers relevant conditions for healthy or pathological situations. It demonstrates that the plug formation induces a high level of stress and stress gradients on the pipe walls, where epithelial cells cover the airways. We find that post-coalescence wall stresses can be 300% to 600% greater than pre-coalescence values. Hence, airway closure qualifies as a cause of sub-lethal or lethal damage to the epithelial cells, which provokes biological response. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700