Soil bacteria are adapted to thrive in an extremely challenging environment. They must face prolonged periods of tough competition with other organisms for a limiting amount of nutrients. Under such selective pressure, populations of soil bacteria have developed the ability to grow on a large array of unusual substrates, including many contaminant organic compounds. Biological degradation of contaminant organic compounds is a very interesting subject in Biotechnology because of their increase in the environment during the last years due to human industrial activity, and the challenge poised by novel residues generated by chemical synthesis. However, bacterial biodegradation is frequently limited by tight regulation of the degradative genes that renders the pathways inactive under most environmental conditions. Our main interests in this field are (i) the biochemical and genetic characterization of biodegradative pathways; (ii) the molecular characterization of the mechanisms involved in regulation of the expression of degradative genes; (iii) the elucidation of global regulatory networks that control carbon and nitrogen metabolism in soil bacteria, and (iv) the rational design of highly efficient expression systems based on regulatory elements from biodegradative pathways for industrial and therapeutic applications. Our current lines of research are the following: