Bacterial migration is important in understanding many practical probl
ems ranging from disease pathogenesis to the bioremediation of hazardo
us waste in the environment. Our laboratory has been successful in qua
ntifying bacterial migration in fluid media through experiment and the
use of population balance equations and cellular level simulations th
at incorporate parameters based on a fundamental description of the mi
croscopic motion of bacteria. The present work is part of an effort to
extend these results to bacterial migration in porous media. Random w
alk algorithms have been used successfully to date in nonbiological co
ntexts to obtain the diffusion coefficient for disordered continuum pr
oblems. This approach has been used here to describe bacterial motilit
y. We have generated model porous media using molecular dynamics simul
ations applied to a fluid with equal sized spheres. The porosity is va
ried by allowing different degrees of sphere overlap. A random walk al
gorithm is applied to simulate bacterial migration, and the Einstein r
elation is used to calculate the effective bacterial diffusion coeffic
ient. The tortuosity as a function of particle size is calculated and
compared with available experimental results of migration of Pseudomon
as putida in sand columns. Tortuosity increases with decreasing obstac
le diameter, which is in agreement with the experimental results.