Speaker
Description
Soil is a complex environment in which the presence of several phases creates numerous interfaces (solid-liquid, liquid-gas and solid-gas). Understanding the local hydrodynamics in soil pores and the biogeochemical processes such as nutrient cycling has been of growing importance in the field of bioremediation and ecology. Besides the coexistence of two immiscible phases (air and water) in the pore space, microorganisms, especially bacteria, are often found in large numbers in natural soil environments. The complex spatial distribution of air and water results in the development of a mosaic of regions of very low water velocity, including areas where water or air is trapped and of preferential channels of high velocity. This landscape of conditions enables microorganisms to live in the free-swimming phase and to form surface attached communities known as biofilms.
At the same time, the biofilms’ structure influences pore geometries resulting in altered hydrodynamics, affecting biofilm development and therefore mass transport. To study influences of soil conditions on biofilms and vice versa, we have studied two soil-born microorganisms, Pseudomonas and Bacillus, at the pore scale using microfluidic devices. We have explored the biofilm forming behavior under different physical conditions such as varied water saturation and flowrate. Carefully designed channel geometries coupled with automated video microscopy allowed us a zoomed-in view on specific interactions while controlling the water saturation by varying the gas flow into the channel. The simplified geometries of the devices resulted in a varied biofilm growth caused by the presence of an immiscible phase.
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