Characterization of bacterial communities associated to plant species from the Sardinian mining district for heavy metal phytoremediation.

Introduction: Heavy metal pollution of soil is a significant environmental problem having negative impact on human health and agriculture. Particularly, abandoned mining areas represent an important problem all over Europe. The Sardinian mining district (SW Sardinia, Italy) has been a major source of Pb and Zn in Europe since its closure in the mid-19th century. Then, the whole mining complex was abandoned resulting in contamination of the area. Phytoremediation is an emerging technology that uses plants and their associated microorganisms for soil remediation of both organic and inorganic contaminants. Plant-associated microorganisms play an important role in the phytoremediation process by affecting heavy metal mobility and availability to the plant and increasing heavy metal tolerance and plant growth. Bioaugmentation-assisted phytoremediation is a promising method for the cleaning-up of soils contaminated by metals. Objectives: Actually, there is a need to improve our understanding of the mechanisms involved in plant promotion and to select plant growth-promoting bacteria for specific restoration programmes. The relevance of natural resources of the Sardinian mining district and its touristic importance require the preservation of the local biodiversity. Thus, the objective of this work is the characterization of bacterial community associated to autochthonous plant species. Results: In a previous study, Scrophularia canina subsp. bicolor and Pistacia lentiscus were identified as autochthonous plant species suitable for phytoremediation of the Sardinian mining district. In a field trial at Campo Pisano mine (Iglesias, Sardinia), root and rhizosphere samples were obtained from plants grown in Pb and Zn contaminated soil. More than 280 bacterial strains were selected for tolerance to Pb or Zn. Bacteria were identified by 16S rRNA sequence analysis. Characterization of the isolates regarding characteristics that may be relevant for a beneficial plant-microbe interaction (metal tolerance, indol-acetic acid and siderophore production) is currently in progress.