Soil pores provide a complex, heterogeneous habitat for diverse microbial species. When experiencing water stress or protozoa grazing, bacteria secrete extracellular polymeric substances (EPS) to form a protective biofilm. EPS has been shown to alter water storage capacity and hydraulic conductivity in bulk-scale soil columns, but this has not been directly observed at the pore-scale. This research employs microfluidic devices to observe the pore-scale effects of EPS secretion on soil hydrology. Preliminary results indicate that alginate, agarose, and EPS hydrogels help maintain hydration in microfluidic devices with simplified pore structures. Water retention of EPS produced by the soil bacteria Sinorhizobium meliloti is currently being tested with systematically varied temperature and humidity in a control chamber allowing real-time observation with optical microscopy. Images are analyzed to differentiate between water, hydrogel, and air phases. This work may eventually contribute to better models of water retention by biological hydrogels in complex pore geometries.

Pore-scale effects of microbial hydrogels on soil water retention

244th National Meeting (2012)

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