Assay for bacteria in porous media by diffusion-weighted NMR

In this work, an NMR technique capable of detecting bacterial cells and measuring the cell density in suspension and in porous media has been developed. It is based on the pulsed-field-gradient technique and relies on the fact that extracellular water diffuses freely while intracellular water is completely restricted by the relatively impermeable cell wall of the bacterium. At high wave vectors, the signal from extracellular water is completely suppressed while the signal from intracellular water is comparatively unaffected. This technique has been applied to the mapping of bacterial distributions in porous media. This method is presented as a non-destructive, real-time technique for biomass characterization within laboratory column and flow cell experiments, and possibly for monitoring in situ bioremediation.