Web Release Date: May 11,
Taking the Fungal Highway: Mobilization of Pollutant-Degrading Bacteria by Fungi
and
Swiss Federal Institute of Technology Lausanne (EPFL), ENAC-ISTE-LPE, CH-1015 Lausanne, Switzerland, University of Virginia, Department of Chemical Engineering, Charlottesville, Virginia 22904, University of Lausanne, CH-1015 Lausanne, Switzerland, and Department of Fundamental Mirobiology, and Centre for Environmental Research Leipzig-Halle, Department of Environmental Microbiology, 04318 Leipzig, Germany
Received for review December 21, 2004
Revised manuscript received March 31, 2005
Accepted April 6, 2005
Abstract:
The capacity of fungi to serve as vectors for the dispersion of pollutant-degrading bacteria was analyzed in laboratory model systems mimicking water-saturated (agar surfaces) and unsaturated soil environments (glass-bead-filled columns). Two common soil fungi (Fusarium oxysporum and Rhexocercosporidium sp.) forming hydrophilic and hydrophobic mycelia, respectively, and three polycyclic aromatic hydrocarbon degrading bacteria (Achromobacter sp. SK1, Mycobacterium frederiksbergense LB501TG, and Sphingomonas sp. L138) were selected based on the absence of mutual antagonistic effects. It was shown that fungal hyphae act as vectors for bacterial transport with mobilization strongly depending on the specific micro-organisms chosen: The motile strain Achromobacter sp. SK1 was most efficiently spread along hyphae of hydrophilic F. oxysporum in both model systems with transport velocities of up to 1 cm d-1, whereas no dispersion of the two nonmotile strains was observed in the presence of F. oxysporum. By contrast, none of the bacteria was mobilized along the hydrophobic mycelia of Rhexocercosporidium sp. growing on agar surfaces. In column experiments however, strain SK1 was mobilized by Rhexocercosporidium sp. It is hypothesized that bacteria may move by their intrinsic motility through continuous (physiological) liquid films forming around fungal hyphae. The results of this study suggest that the specific stimulation of indigenous fungi may be a strategy to mobilize pollutant-degrading bacteria leading to their homogenization in polluted soil thereby improving bioremediation.
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