Bacteria are the most abundant organisms on Earth and they significantly influence carbon
cycling and sequestration, decomposition of biomass, and transformation of contaminants in the
environment. This motivates our study of the basic principles of
bacterial behavior and its control.The principal mechanism behind the
unique macroscopic properties of bacterial suspensions (e.g.,7-fold
reduction of the effective viscosity and a 10-fold increase of the
effective diffusivity) is self-organization of the bacteria at the
microscopic level – a multiscale phenomenon. Our goal is
theunderstanding the mechanism of self-organization, which is a
fundamental issue in the study of biological and inanimate systems. Our
work in this area includes:
- Analytical and numerical study of dilute and semi-dilute bacterial suspensions.
We introduced a so-called semi-dilute model for swimming bacteria that
includes pairwise interactions and obtained an explicit asymptotic
formula for the effective viscosity in terms of known physical
parameters. This formula is compared with that derived in our PDE model
for a dilute suspension of bacteria driven by a stochastic torque,
which models random reorientation of bacteria (“tumbling”).
This comparison leads to a phenomenon of stochasticity arising from a
deterministic system is referred to as self-induced noise.We also
conducted numerical modeling of a large number of interacting bacteria
using Graphical Processing Units (GPU).
- Kinetic collisional model–work in progress.
We seek to capture a phase transition in the bacterial suspension
– an appearance of correlations and local preferential alignment
with an increase of concentration. Collisions of the bacteria, ignored
in most of the previous works, play an important role in this study,
which is based on the kinetic theory approach.
Collaborators: PSU students S. Ryan and B. Haines, and DOE scientists I. Aronson and D.
Karpeev (both Argonne Nat. Lab)