Use of mycelia as paths for the isolation of contaminant-degrading bacteria from soil

Mycelia of fungi and soil oomycetes have recently been found to act as effective paths boosting bacterial mobility and bioaccessibility of contaminants in vadose environments. In this study, we demonstrate that mycelia can be used for targeted separation and isolation of contaminant-degrading bacteria from soil. In a 'proof of concept' study we developed a novel approach to isolate bacteria from contaminated soil using mycelia of the soil oomycete Pythium ultimum as translocation networks for bacteria and the polycyclic aromatic hydrocarbon naphthalene (NAPH) as selective carbon source. NAPH-degrading bacterial isolates were affiliated with the genera Xanthomonas, Rhodococcus and Pseudomonas. Except for Rhodococcus the NAPH-degrading isolates exhibited significant motility as observed in standard swarming and swimming motility assays. All steps of the isolation procedures were followed by cultivation-independent terminal 16S rRNA gene terminal fragment length polymorphism (T-RFLP) analysis. Interestingly, a high similarity (63%) between both the cultivable NAPH-degrading migrant and the cultivable parent soil bacterial community profiles was observed. This suggests that mycelial networks generally confer mobility to native, contaminant-degrading soil bacteria. Targeted, mycelia-based dispersal hence may have high potential for the isolation of bacteria with biotechnologically useful properties.