Can bacteria associated with willow explain differences in Cd-accumulation capacity between different cultivars?

Abstract

Phyoremediation has been proposed as an economically interesting alternative for remediation of metal contaminated soils. It can be applied on extended and diffusely contaminated areas and targets the "bioavailable" fraction of metals, which is the most relevant fraction from an environmental risk assessment perspective. The most important drawback is the long time period required for remediation process. Main limiting factors for an efficient phytoextraction are plant availability of metals, metal uptake and phytotoxicity. These constraints can be conquered by (1) choosing plant cultivars with both high metal uptake capacity and high biomass production; by (2) increasing metal availability and uptake using plant-associated bacteria capable of producing siderophores, organic acids and/or auxins; or by (3) reducing metal phytotoxicity exploiting endophytes equipped with a metal sequestration system. In this work two different willow clones growing on a Cd-contaminated site were chosen.; one with a rather high and one with a rather low Cd-accumulation capacity. All cultivable bacteria associated with both willow clones were isolated and identified using 16SrDNA ARDRA analysis followed by 16SrDNA sequencing. Further all isolated bacteria were tested for their capacity to produce siderophores, organic acids and indol acetic acid for their Cd-resistance. Both willow-associated bacterial populations were compared and if possible, differences in phenotypic characteristics were related to the different Cd-accumulation capacities of their hosts. From this bacterial collection, bacteria with the potential to improve Cd-phytoremediation will be inoculated in willow cuttings and their Cd-extraction capacity and Cd-phytotoxicity will be evaluated in a greenhouse experiment.