Abandoned mining areas are a crucial environmental problem worldwide. The Sardinian mining area (SW Sardinia, Italy) has been a major source of Pb and Zn and was actively exploited from Phoenician times until recently. In the last century, the cessation of the mining activities caused a diffuse metal contamination due to inadequate definition of pollution containment plants. Large quantities of mine wastes are still present in the area. The Iglesiente district, one of the most significant abandoned mining areas, is now included in the Sardinian Geomining Park, a UNESCO world heritage. Moreover, the environmental reclamation of the area was planned. P. lentiscus is a shrub diffused in the Mediterranean Basin, including Sardinia. This metal-tolerant phanerophyte is widely distributed in the Sardinian mining area, growing also in particularly degraded sites. The P. lentiscus species has been recognised a good candidate for phytostabilization of abandoned mine tailings. The scope of this work was to characterize the diversity of the root-associated bacterial communities colonizing P. lentiscus from the Sardinian mining area, a peculiar environment characterized not only by extreme heavy metal concentrations but also by semi-arid conditions. The bacterial communities associated to plant root tissues were analysed by using both cultivation and cultivation-independent techniques. Spontaneous plants and rhizosphere soils were sampled from two different sites of the Iglesiente district: the tailing dump of the Campo Pisano abandoned mine and the Sa Masa wetland which collect the drainages of the main mines in the district. In the rhizosphere soils, Zn, Pb and Cd concentrations were 9-19, 4-6, 0.05-0.1 g/Kg, respectively. Concerning metal accumulation in plant tissues, concentrations were significantly higher in roots than in the aerial tissues. Two hundred bacteria strains were isolated from surface sterilized roots and identified by 16S rRNA sequence analysis. The isolates were further evaluated for properties that may be relevant for a beneficial plant-microbe interaction: heavy metal (Pb, Zn, and Cd) tolerance, phosphate solubilisation, 1-aminocyclopropane-1-carboxylic acid deaminase, indoleacetic acid, and siderophore production. The root-associated cultivable community from Campo Pisano plants is dominated by members of the Actinomycetales whereas that from Sa Masa plants is dominated by alpha and gamma Proteobacteria. Bacterial strains isolated from both sites demonstrated high level of metal tolerance and the ability to produce plant-growth promoting factors. The construction and sequencing of 16S rRNA gene clone libraries are currently in progress.
Characterization of bacterial communities associated with Pistacia lentiscus L. from the abandoned Sardinian mining area
CAPPAI, GIOVANNA SALVATORICA;CARUCCI, ALESSANDRA;BACCHETTA, GIANLUIGI;TAMBURINI, ELENA
2012-01-01
Abstract
Abandoned mining areas are a crucial environmental problem worldwide. The Sardinian mining area (SW Sardinia, Italy) has been a major source of Pb and Zn and was actively exploited from Phoenician times until recently. In the last century, the cessation of the mining activities caused a diffuse metal contamination due to inadequate definition of pollution containment plants. Large quantities of mine wastes are still present in the area. The Iglesiente district, one of the most significant abandoned mining areas, is now included in the Sardinian Geomining Park, a UNESCO world heritage. Moreover, the environmental reclamation of the area was planned. P. lentiscus is a shrub diffused in the Mediterranean Basin, including Sardinia. This metal-tolerant phanerophyte is widely distributed in the Sardinian mining area, growing also in particularly degraded sites. The P. lentiscus species has been recognised a good candidate for phytostabilization of abandoned mine tailings. The scope of this work was to characterize the diversity of the root-associated bacterial communities colonizing P. lentiscus from the Sardinian mining area, a peculiar environment characterized not only by extreme heavy metal concentrations but also by semi-arid conditions. The bacterial communities associated to plant root tissues were analysed by using both cultivation and cultivation-independent techniques. Spontaneous plants and rhizosphere soils were sampled from two different sites of the Iglesiente district: the tailing dump of the Campo Pisano abandoned mine and the Sa Masa wetland which collect the drainages of the main mines in the district. In the rhizosphere soils, Zn, Pb and Cd concentrations were 9-19, 4-6, 0.05-0.1 g/Kg, respectively. Concerning metal accumulation in plant tissues, concentrations were significantly higher in roots than in the aerial tissues. Two hundred bacteria strains were isolated from surface sterilized roots and identified by 16S rRNA sequence analysis. The isolates were further evaluated for properties that may be relevant for a beneficial plant-microbe interaction: heavy metal (Pb, Zn, and Cd) tolerance, phosphate solubilisation, 1-aminocyclopropane-1-carboxylic acid deaminase, indoleacetic acid, and siderophore production. The root-associated cultivable community from Campo Pisano plants is dominated by members of the Actinomycetales whereas that from Sa Masa plants is dominated by alpha and gamma Proteobacteria. Bacterial strains isolated from both sites demonstrated high level of metal tolerance and the ability to produce plant-growth promoting factors. The construction and sequencing of 16S rRNA gene clone libraries are currently in progress.
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