Taking the Fungal Highway:  Mobilization of Pollutant-Degrading Bacteria by Fungi

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 microorganisms 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 motilitythrough 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.

Plant litter and soil type drive abundance, activity and community structure of alkB harbouring microbes in different soil compartments

“…Factors such as the availability of nutrients or electron acceptors introduced by the plant litter may accordingly be important (Wiesenberg et al, 2004;Dignac and Rumpel, 2006) forming steep gradients and thus preferentially influencing the community structure. Furthermore, plant litter-derived degraders could be transferred to the litter-soil interface along fungal hyphae (Kohlmeier et al, 2005), without reaching the deeper soil layers. However, on the expression level, the depth differentiation between the two soil compartments was less pronounced as also observed for the alkB transcripts in litter and soil.…”

Enhanced Tolerance to Cadmium in Bacterial-Fungal Co-Cultures as a Strategy for Metal Biorecovery from e-Waste

“…Four criteria were used to define synergistic BF couples: (1) bacterial and fungal strains had both to grow at all the following Cd concentrations: 0.1 mM, 0.25 mM, 0.5 mM, 0.75 mM and 1 mM; (2) one strain should not have an inhibitory effect on the other inoculated strain; (3) the bacterial and the fungal strains should be able to grow in contact; (4) the bacterial strain should use the mycelium of the fungus for dispersal (FH interaction; [31]). The latter criterion was demonstrated by gently streaking an inoculation loop on the fungal mycelium at the greatest distance possible from bacterial inoculation and by using this as inoculum on a NA + cycloheximide medium.…”

Microbial dispersal in unsaturated porous media: Characteristics of motile bacterial cell motions in unsaturated angular pore networks

“…In heterogeneous systems, bacterial motility is often biased by chemotaxis that guides bacteria toward higher concentrations of nutrients (or away from toxic compounds) [Fenchel, 2002;Stocker et al, 2008]. Chemotaxis has been observed in soil where motile bacteria show chemotactic response to a variety of pollutants considered as potential nutrient sources [Parales et al, 2000;Olson et al, 2004;Kohlmeier et al, 2005;Ford and Harvey, 2007].…”