Development of biological systems for the traceability of environmental pollutants

Arsenic is a natural trace element found in the environment in different oxidation states. Exposure to inorganic arsenic can cause various health effects with different severity, such as irritation of the stomach, intestine and cancer development. In many industrial areas (Bagnoli, Taranto, Italy) the environmental concentration of this metalloid has reached levels that exceed hazard thresholds. The ubiquity of arsenic has led to the evolution of molecular systems for its detoxification. The ars operon constitutes the most important mechanism of arsenic tolerance in bacteria. This system mediates the extrusion of arsenite out of the cells [1]. We report the ability of the thermophilic bacterium Thermus thermophilus HB27 to grow aerobically in medium supplemented with up to 13 mM arsenate or 4 mM arsenite. Two genes, TTC0353 and TTC1502, coding for a putative ArsR/SmtB transcriptional repressor and an arsenate reductase (ArsC) [2], respectively, have been identified; transcriptional analyses have demonstrated that smtB and arsC are transcribed in two different operons with non functionally correlated genes and that their expression is regulated by arsenic. The expression and characterization of the recombinant ArsC protein is also described.