Analysis of Bacterial Random Motility in a Porous Medium Using Magnetic Resonance Imaging and Immunomagnetic Labeling

• Published in: Environmental science & technology 2003-02, Vol.37 (4), p.781-785
• Main Authors: Sherwood, Juli L, Sung, James C, Ford, Roseanne M, Fernandez, Erik J, Maneval, James E, Smith, James A
• Format: Article
• Language: English
• Subjects: Analysis; Analytical Methods; Animal, plant and microbial ecology; Antibodies, Monoclonal; Applied sciences; Aquatic life; Bacteria; Bacteriology; Biological and medical sciences; Environmental Monitoring - methods; Escherichia coli; Exact sciences and technology; Ferrosoferric Oxide; Fundamental and applied biological sciences. Psychology; Groundwaters; Iron; Labeling; Magnetic Resonance Imaging; Microbial ecology; Microbiology; Motility; Motility, taxis; Movement; Natural water pollution; NMR; Nuclear magnetic resonance; Oxides; Pollution; Population Dynamics; Porosity; Various environments (extraatmospheric space, air, water); Water Microbiology; Water treatment and pollution
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es011210u

In this study, we demonstrate the application of immunomagnetic labeling and magnetic resonance imaging (MRI) for the noninvasive visualization of changes in bacterial density distributions as a function of time in a water-saturated porous medium. Magnetite particles (50−60 nm diameter) were attached via a monoclonal antibody to the surface of Escherichia coli K12 NR50 cells. The cells maintained their motility after labeling, and the presence of the magnetite did not significantly alter cell swimming speed. Diffusive migration for both motile and nonmotile E. coli through a porous medium with a particle-diameter distribution of 250−300 μm was compared. The movement of the nonmotile cells was described by an effective random motility coefficient consistent with Brownian diffusion of a nonmotile colloid. An effective coefficient determined a priori from bacterial motility in an aqueous medium and properties of the porous medium adequately described the movement of the motile cells. The ability to noninvasively visualize bacterial concentrations within an opaque porous medium in real time provides researchers with a powerful tool for studying bacterial transport in porous media. This is important for understanding the impact of bacterial transport on remediation strategies for environmental cleanup of polluted groundwater.