Metal-Tolerant Thermophiles: From the Analysis of Resistance Mechanisms to their Biotechnological Exploitation

Extreme terrestrial and marine hot environments are excellent niches for specialized microorganisms belonging to the domains of Bacteria and Archaea; these microorganisms are considered extreme from an anthropocentric point of view because they are able to populate harsh habitats tolerating a variety of conditions, such as extreme temperature and/or pH, high metal concentration and/or salt; moreover, like all the microorganisms, they are also able to respond to sudden changes in the environmental conditions. Therefore, it is not surprising that they possess an extraordinary variety of dynamic and versatile mechanisms for facing different chemical and physical stresses. Such features have attracted scientists also considering an applicative point of view. In this review we will focus on the molecular mechanisms responsible for survival and adaptation of thermophiles to toxic metals, with particular emphasis on As(V), As(III), Cd(II), and on current biotechnologies for their detection, extraction and removal.