Tracking microbial movement in saturated media with spectral induced polarization

Area of Science:

• Geophysics
• Environmental Microbiology
• Subsurface Science

Background:

• Pathogenic microorganisms in subsurface environments pose risks to human health.
• Current detection methods using direct sampling are limited in spatiotemporal resolution.
• Monitoring microbial transport pathways is crucial for early detection of biohazardous threats.

Purpose of the Study:

• To evaluate the efficiency of spectral induced polarization (SIP) in monitoring microbial chemotaxis.
• To assess the correlation between SIP signals and the movement of Sporosarcina pasteurii in saturated porous media.

Main Methods:

• A vertical column packed with Ottawa sand was used, saturated with KCl solution.
• Sporosarcina pasteurii was introduced at the bottom, migrating upwards towards a carbon source.
• Temporal SIP measurements were collected at the bottom, middle, and top of the column.

Main Results:

• Both real (σ') and imaginary (σ″) conductivity parts of the SIP signal increased over time.
• A peak in the imaginary conductivity (σ″) signal correlated with the upward microbial movement.
• Control experiments without a carbon source or microbial injection showed no significant SIP signal changes.

Conclusions:

• Spectral induced polarization (SIP) is a viable geophysical technique for monitoring microbial chemotaxis in subsurface environments.
• SIP signals show a strong correlation with microbial movement, offering a promising tool for subsurface contamination detection.