Hydrocarbon degradation and plant colonization by selected bacterial strains isolated from Italian ryegrass and birdsfoot trefoil

Aims: To assess the degradation potential and plant colonization capacity of four alkane-degrading strains (ITSI10, ITRI15, ITRH76 and BTRH79) in combination with birdsfoot trefoil and Italian ryegrass and to evaluate the diversity of indigenous alkane-degrading soil bacteria in the rhizo- and endosphere. Methods and Results: Contaminated soil was prepared by spiking agricultural soil with 10 g diesel fuel per kg soil. Italian ryegrass (Lolium multiflorum var. Taurus) and birdsfoot trefoil (Lotus corniculatus var. Leo) were inoculated with four alkane-degrading strains. Hydrocarbon degradation (up to 57%) was observed in all inoculated treatments of vegetated and unvegetated samples. Italian ryegrass in combination with compost and BTRH79 showed highest degradation, while birdsfoot trefoil performed best with compost and strain ITSI10. Cultivation-based as well as cultivation-independent analysis showed that both strains were competitive colonizers. Conclusions: The combination between vegetation, inoculation with well-performing degrading bacteria and compost amendment was an efficient approach to reduce hydrocarbon contamination. Two Pantoea sp. strains, ITSI10 and BTRH79, established well in the plant environment despite the presence of a variety of other, indigenous alkane-degrading bacteria. Significance and Impact of the Study: This study suggests that the application of degrading bacterial strains, which are able to compete with the native microflora and to tightly associate with plants, are promising candidates to be used for phytoremediation applications.