Biotechnology for a sustainable remediation of polluted soils

Soil is a living and life-giving non-renewable natural resource. Pollution associated with human activity is one of the main agents of soil degradation. Hydrocarbons are the most abundant group of soil pollutants, including the toxic and carcinogenic polycyclic aromatic hydrocarbons (PAHs). Bioremediation, which utilizes the natural biodegradative capacities of soil microorganisms, is a sustainable technology with the potential to restore the natural functions of soil. Though its use in Europe has increased dramatically during the last decade, uncertainty regarding final end-point concentrations continues to hamper its widespread application. Laboratory biotreatability studies are a useful tool for designing and evaluating the potential of bioremediation strategies in the clean-up of specific sites. However, optimization of this biotechnology and the development of new diagnostic and monitoring tools require a comprehensive understanding of the metabolic microbial networks involved in pollutants removal. Metabolic studies with single bacterial cultures have proven essential for hypothesizing how microbial communities cooperate in the synergistic degradation of organic contaminants, with key populations initiating attacks to produce partially oxidized compounds that are then more efficiently mineralized by secondary degraders. Advances in molecular tools are not only facilitating more comprehensive analysis of culturable and non-culturable microbial populations, but also finer distinctions between active and non-active microorganisms, and quantification of the expression of key enzymatic functions. These innovations will help confirm and illuminate the actual role of previously hypothesized networks, revealing new microbial functions for exploitation.