6533b7cffe1ef96bd1258acd

RESEARCH PRODUCT

Estimation of the degrading genetic potential of soil bacterial communities: a new tool for evaluating and predicting soil contamination by organic micropollutants (i.e. pesticides, PAHs)

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During the last two centuries, industrialisation has led to increasing contamination of the environment by xenobiotics, notably aromatic compounds (i.e. PAHs, pesticides). These widespread pollutants are a major threat affecting soil quality and human health. In this context, numerous policies have been drawn up notably in Europe, to monitor the threats of pollution to ecosystems and to detect and implement measures to counterbalance the damage. Nevertheless, the European Commission and scientific community are still confronted with a lack of appropriate tools to monitor biodiversity in relation to environmental processes affecting global warming and soil protection. This study proposes tools to assess the biodiversity of functional bacterial communities involved in the process of natural and xenobiotic aromatics biodegradation in soil environments. The major route for the degradation of aromatic compounds is the ß-ketoadipate pathway. We developed two molecular markers i.e. two primer sets targeting two key genes (pcaH and catA) of the ß-ketoadipate pathway, encoding enzymes responsible for the ring cleavage of catechol and protocatechuate. The PCAH molecular marker targeted a sequence from the ß-subunit of 3,4-PCD encoded by the pcaH gene. PCAH was shown to amplify a wide diversity of pcaH sequences in the soil environment, thereby highlighting its interest in characterising the pca bacterial community responsible for the degradation of protocatechuate. This tool was applied to assess the structure, diversity and density of the pca bacterial community. When tested in experimental fields, it revealed changes in the structure, diversity and density of the pca bacterial community in response to organic amendments. This work showed that PCAH could constitute a tool of prime interest for assessing the impact produced by extrinsic factors such as agricultural practices on biodiversity of the pca community. The CATA molecular marker targeted a fragment of the 1,2-CTD encoding gene (catA). The wide diversity of catA sequences was revealed. At this stage in the development of pca and cat bioindicators, we can only provide tools to describe the structure, diversity and density of these bacterial communities. The use of PCR-RFLP fingerprinting and q-PCR assays is recommended to assess the impact of environmental stresses on these functional bacterial communities.