Geophysical monitoring of microbial transport in saturated media
Abstract
Microbial transport in the subsurface can pose either a problem (e.g., pathogenic microorganisms in water supplies) or the solution (e.g., bioremediation). Monitoring the location of microorganisms in the subsurface often is limited to a few sampling locations (e.g., wells) and due to limited spatial and temporal resolution of these points, the trajectory of the microbial transport in subsurface remains ambiguous. Geophysical methods are capable of delineating subsurface changes, including microbial transport, with high spatiotemporal resolution. Spectral induced polarization (SIP) is an established geophysical technique that can detect microbial cells and is a promising method to monitor microbial transport pathways.
In this project we evaluated the efficiency of SIP in monitoring the chemotactic movement of Sporosarcina pasteurii in saturated porous media. S. pasteurii cells were prepared in batch cultivations and their motility was confirmed under the microscope. The porous media (quartzitic sand) was packed into a 10X2.5 cm column and saturated with KCl to allow free movement of the microbes. The column was oriented vertically and S. pasteurii was introduced at the bottom, allowing the movement of the bacteria against gravity, towards the carbon source available at the top of the column. SIP measurements were collected at 3 locations of the column: bottom (microbial injection point), middle (transient area) and top (carbon source). Fluorescence staining of fluid samples collected at each location showed the presence of microbial cells at middle and top of the column after 20 hours confirming microbial chemotaxis in response to the carbon stimuli. The SIP signal showed sensitivity to microbial movements; the imaginary conductivity signal increased over time with the peak signal magnitude following the upward movement of the microbes. In contrast, the real conductivity changes did not follow the microbial movements, but instead followed the diffusion of the carbon source within the porous media. The result shows the promising capabilities of SIP in monitoring microbial transport in real-time; however, further tests on different types of porous media, microbes and saturation fluids as well as under unsaturated and uncontrolled conditions are required.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.B53F2461N
- Keywords:
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- 0406 Astrobiology and extraterrestrial materials;
- BIOGEOSCIENCES;
- 0418 Bioremediation;
- BIOGEOSCIENCES;
- 1505 Biogenic magnetic minerals;
- GEOMAGNETISM AND PALEOMAGNETISM;
- 1835 Hydrogeophysics;
- HYDROLOGY