Collaborative Research: Investigating the impact of microbial interactions with geologic media on geophysical properties: Implications for assessing geomicrobiology processes

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Bacteria have been shown to play an important role in geologic processes, however, their role in altering geophysical properties of rocks is not well understood, nor has it been thoroughly investigated. This project is a three-year collaboration between researchers at the University of Missouri-Rolla, Rutgers University, and Western Michigan University. Its purpose is to understand and measure geophysical changes resulting from microbial interactions with geologic media. Specific objectives of the project are to conduct laboratory and field studies to investigate: (1) the effect of increases in microbial cell concentrations and biofilm formation on soil and sediment electrical properties, (2) the effect of metabolic by-products of microbial activity, such as biosurfactants and organic acids, on geophysical electrical measurements, (3) potential changes in petrophysical properties (e.g., permeability, porosity, surface area) induced by microbial-mineral interactions, and (4) differences in the microbial communities and their structure, dynamics, and associations in sediments with anomalous geophysical signatures. The first phase of the work will involve measuring the electrical signatures of bacterial cells, biofilms, and organic acids in laboratory column reactors. Final reactor products will then be imaged with photomicrography to investigate biofilm distribution and changes in pore geometry. The second phase of the work will focus on measurements of reactor sediment physical properties (formation factor, surface area, porosity, permeability). Results of this work will help build a database to relate electrical, physical, and biochemical parameters that can be used in geophysical modeling of field input data. The final phase of the program will concentrate on field measurements and observations on how changes in sediment electrical conductivity can be related to microbial alteration of geologic materials. These analyses will be carried out on cores and at the field scale. This study will form the basis for the development of geophysics as a tool for investigating geomicrobiological processes. Broader and potential societal benefits include development of geophysical techniques that can be used for monitoring and assessing biological colonization of groundwater aquifers and microbial mineralization of dissolved pollutants in the near subsurface. Educational and outreach initiatives will focus on student involvement and student-led promotion of biogeophysics to the wider Geophysics and Biogeosciences community at national mad international meetings.