BIOREMEDIATION OF A POLYCHLORINATED BIPHENYL (PCB) POLLUTED SITE: DEGRADING POTENTIAL OF SOIL MICROBIOTA AND EXPLOITATION OF PLANT-BACTERIA INTERACTIONS FOR ENHANCED RHIZOREMEDIATION
Tesi di Dottorato
Data di Pubblicazione:
2017
Citazione:
BIOREMEDIATION OF A POLYCHLORINATED BIPHENYL (PCB) POLLUTED SITE: DEGRADING POTENTIAL OF SOIL MICROBIOTA AND EXPLOITATION OF PLANT-BACTERIA INTERACTIONS FOR ENHANCED RHIZOREMEDIATION / L. Vergani ; supervisor: S. Borin ; coordinatore: F. Bonomi. DIPARTIMENTO DI SCIENZE PER GLI ALIMENTI, LA NUTRIZIONE E L'AMBIENTE, 2017 Dec 21. 30. ciclo, Anno Accademico 2017. [10.13130/l-vergani_phd2017-12-21].
Abstract:
The release of xenobiotic chemicals into the environment has dramatically increased over the last century following industrialization, with a consequent impact on the ecosystems and human health. Polychlorinated biphenyls (PCB), in particular, are among the twelve chlorinated organic compound families initially listed as persistent organic pollutants (POPs) by the Stockholm Convention on POPs. PCB, due to their chemical properties and high stability, have been widely used by industries in the twentieth century as dielectric and coolant fluids. Despite their production has been banned since the 1970s-1980s, these pollutants contaminate soils and waters and affect the ecosystems worldwide, being widespread global contaminants. Due to their high lipophilicity, PCB are recalcitrant to biodegradation, persist in the environment and bioaccumulate in the lipids of animals and humans, biomagnifying in the food web. It has been proved that PCB have relevant toxic effects on human health, including carcinogenic activity. The remediation of PCB-contaminated soils represents therefore a primary issue for our society; nonetheless, the available physical-chemical technologies have strong environmental and economic impact and are unsuitable for in situ soil remediation in extended contaminated areas. Rhizoremediation is a type of phytoremediation that relies on the capability of soil microbes responding to plant biostimulation, to degrade pollutants. This strategy appears as the most suitable for the detoxification of large-scale PCB-polluted soils. Among soil contaminants, rhizoremediation of PCB is specifically relying on the positive interactions between plants and microorganisms in the rhizosphere. In fact, several organic aromatic compounds released through root deposition can promote the activation of the biphenyl catabolic pathway that is responsible for the microbial oxidative PCB metabolism, thereby improving the overall PCB degradation performance in aerobic conditions in soil. Moreover, plant-growth promoting (PGP) microorganisms selected in the rhizosphere can sustain plant growth under stressed conditions typical of polluted soils, in turn enhancing the plant biostimulation. Nevertheless, the efficiency of this biotechnology in situ has been poorly assessed in the scientific literature, since the upscaling from laboratory to greenhouse conditions to the field was rarely implemented. Site-specific environmental conditions still represent a major challenge for an efficient in situ rhizoremediation intervention, especially when it comes to understand how the pollution fingerprint affects the autochthonous degrading bacterial populations and whether these are able to establish positive interactions with the introduced plant species. This PhD project focused on the Site of National Priority (SIN) Caffaro, a large site located in Northern Italy historically polluted by chlorinated POPs and metals. Aim of the work was to study the phylogenetic and functional diversity of the soil microbiota, assessing the correlation between diversity and pollutant profiles as a proxy to evaluate the biodegradation potential in the SIN Caffaro soil. A further aim of the thesis was to focus on the plant rhizosphere microbiome in order to setup in situ rhizoremediation strategies by evaluating the plant species with the higher potential for biostimulation.
The soil microbiome of three former agricultural fields within the SIN Caffaro was investigated with molecular ecology –16S rRNA metagenomic sequencing and DNA fingerprinting- and biochemical –fluorescein hydrolyses- approaches. The results revealed that the bacterial communities’ structure, their phylogenetic diversity and the soil microbial activity were related with the soil physical and chemica
Tipologia IRIS:
Tesi di dottorato
Elenco autori:
L. Vergani
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