Predictive Modeling of collective swimming in bacterial supensions

Summary

Principal Investigator: Leonid Berlyand
Abstract: Collective swimming -- a highly correlated motion of bacteria -- plays an important role in the life cycle of many bacterial species. Experiments, some conducted under the direction of one of the coPIs, have uncovered several important consequences of collective motion in suspensions of swimming bacteria: a dramatic increase in the effective diffusivity, a lowering of the effective viscosity by an order of magnitude, and the extraction of useful work from the correlated motion of bacteria. These phenomena clearly distinguish the properties of bacterial suspensions both from the properties of the fluid they swim in, and from the properties of individual swimming bacteria. In particular, an effective diffusivity enhanced by the collective motion of an aerobic bacterial colony leads to an increased supply of dissolved oxygen -- a survival advantage relative to an isolated bacterium. Collective swimming manifests in the appearance of persistent coherent configurations of bacteria many times the size of a single bacterium. However, a description of the mechanism leading to collective motion remains lacking. The goal of this project is to use mathematical modeling and carefully designed experiments to advance the understanding of the mechanisms of this type of bacterial self-organization. This can in turn have a profound effect on the state of biological an medical sciences: from to insight into the formation of biofilms and evolution of multicellular organisms from unicellular, to the understanding of the formation and organization of tissues and organs. There are many theoretical works trying to explain the appearance of collective motion and its impact on the macroscopic properties of the system. Most are based on the assumption of the central role of the additive long-range hydrodynamic interactions between the bacteria, which in the context of kinetic theory can be accurately captured by the mean field approximation. This assumption, however, is not accurate in the disordered configurations prevalent before the onset of collective motion, were the dipolar fields from different bacteria largely cancel each other. Here fluctuations -- deviations from the mean -- are significant, and the strongest interactions are due to collisions between the bacteria. Here a new kinetic model is proposed that goes beyond the mean field approximation and, in particular, incorporates fluctuations and captures collisions. The effect of binary inelastic collisions will be modeled using an integral operator. The fluctuations will take the form of a self-quenching white noise - a noise whose strength decays when the local alignment between the bacteria increases, reflecting the physical fact that in a highly-aligned configuration collisions are rare. This approach leads to a generalized Fokker-Plank equation (GFPE) - a time-dependent integro-differential equation governing the position and orientation of a single bacterium. GFPE will be derived, analyzed and validated against suitably-designed experiments.
Funding Period: 2012-07-01 - 2015-04-30
more information: NIH RePORT

Top Publications

  1. pmc Effective viscosity of puller-like microswimmers: a renormalization approach
    Simon Gluzman
    Department of Mathematics, Pennsylvania State University, University Park, PA 16802, USA
    J R Soc Interface 10:20130720. 2013

Detail Information

Publications3

  1. pmc Effective viscosity of puller-like microswimmers: a renormalization approach
    Simon Gluzman
    Department of Mathematics, Pennsylvania State University, University Park, PA 16802, USA
    J R Soc Interface 10:20130720. 2013
    ..We find that the method performs much better than an earlier RG-based technique. For pullers, the validation is done by comparing them to experiments conducted on Chlamydamonas suspensions. ..

Research Grants30

  1. CENTER FOR GASTROINTESTINAL BIOLOGY AND DISEASE
    Robert S Sandler; Fiscal Year: 2013
    ..Through all of its activities, the Center improves communication, promotes collaboration, develops careers and generally enriches the intellectual climate for digestive disease research. ..
  2. MULTI-SCALE MODEL OF THORMBOSIS IN ARTIFICIAL CIRCULATION
    James F Antaki; Fiscal Year: 2013
    ..The purpose of this project is to create a computer simulation program that will predict when this might occur, and thereby guide developers of these devices to produce more safe and effective devices. ..
  3. New Approaches To Cardiothoracic Tolerance Induction
    Joren C Madsen; Fiscal Year: 2013
    ..We anticipate ongoing progress will continue to contribute to a reduction in the morbidity and mortality associated with solid organ transplantation. ..
  4. Rocky Mountain Regional Center of Excellence or Biodefense and Emerging Infectiou
    John T Belisle; Fiscal Year: 2013
    ..abstract_text> ..
  5. Dynamics and mechanism of mechanical regulation of bacterial flagellar motor swit
    Jianhua Xing; Fiscal Year: 2013
    ..It will place studies of BFM functions in the broader context of cell physiology regulations. ..
  6. Simultaneous Time-Resolved X-ray Spectroscopy and Crystallography: A Mechanistic
    Rosalie Tran; Fiscal Year: 2013
    ..abstract_text> ..
  7. Study of the interplay of motility mechanisms during swaming of Myxococcus xanthu
    Mark Alber; Fiscal Year: 2013
    ....
  8. Protein Dynamics in Enzymatic Catalysis
    Robert Callender; Fiscal Year: 2013
    ..The Equipment Core (Core A) supports the specialized comprehensive suite of instrumentation for the Program. The Administrative Core (Core B) administers the Program Project. ..
  9. Probes for fluids in bacterial swarms
    Howard C Berg; Fiscal Year: 2013
    ..We also will try to develop buoyant particulate probes for viscosity and pH. ..
  10. CaMKII and InsP3-Mediated Signaling in Cardiac Myocytes
    Donald M Bers; Fiscal Year: 2013
    ..Results will greatly increase our understanding of the roles of CaMKll and InsP3R in cardiac myocytes during ECC, arrhythmogenesis &nuclear signaling in normal, Hyp and HF cardiac myocytes. ..