This work focused on the interactions between physical and chemical gradients in porous media and their influence on gene expression, adaptation, and growth. The practical motivation was to better understand and manipulate the factors controlling biodegradation or recalcitrance in the environment. Using a micromodel system in which the pore structure, flows, and chemical gradients were known, we investigated adaptation of the bacterium Delftia acidovorans to degrade the herbicide 2,4-dichlorophenoxyacetate (2,4-D). Adaptation occurred in the micromodel, and persisted longer in the absence of alternative substrates than in chemostat studies. A distinct spatial structure of adaptation was not observed. This could indicate that the process is not highly sensitive to chemical gradients, or it could reflect the distribution of adapted cells through motility.
Funding: USDA CSREES Agriculture and Food Research Initiative, Soil Processes

Collaborators: Charlie Werth (Illinois) & Roland Müller (Helmholtz Centre for Environmental Research, Leipzig)

Students & Postdocs: Sabine Leibeling, Ken Ng, Xing Wang, Hongkyu Yoon, Changyong Zhang

Related publications:

Yoon, H., S. Leibeling, C. Zhang, R. H. Müller, C. J. Werth, and J. L. Zilles. 2014. Adaptation of Delftia acidovorans for herbicide degradation in a microfluidic porous medium. Biodegradation 25(4):595. 2014 Feb 12. [Epub ahead of print]

Leibeling, S., M. B. Maeß, F. Centler, S. Kleinsteuber, M. von Bergen, M. Thullner, H. Harms, and R. H. Müller. 2013. Posttranslational oxidative modification of (R)-2,4-dichlorophenoxypropionate/α-ketoglutarate-dioxygenase (RdpA) leads to improved degradation of 2,4-dichlorophenoxyacetate (2,4-D). Eng. Life Sci. 13:278-291. DOI:10.1002/elsc.201100093

Zhang, C., Q. Kang, X. Wang, J. L. Zilles, R. H. Müller, and C. J. Werth. 2010. Effects of porous media heterogeneity and transverse mixing on bacterial growth. Environ. Sci. Technol. 44(8):3085-3092.

Leibeling, S., F. Schmidt, N. Jehmlich, M. von Bergen, R. H. Müller, and H. Harms. 2010. Declining capacity of starving Delftia acidovorans MC1 to degrade phenoxypropionate herbicides correlates with oxidative modification of the initial enzyme. Environ. Sci. Technol. 44 (10), 3793-3799.