Plants as extreme environments? Ni-resistant bacteria and Ni-hyperaccumulators of serpentine flora

During recent years there has been an increasing interest in the bacterial communities occurring in unusual, often extreme, environments. On serpentine outcrops around the world, a high diversity of plant species showing the peculiar features of metal hyperaccumulation is present. These metal hyperaccumulators have received much attention for their potential biotechnological exploitation in phytoremediation processes, but also as unusual, extreme habitats for the associated bacterial flora, which could reveal novel details concerning bacterial adaptation. This paper will briefly focus on the research topics that have been addressed to date on bacteria associated with serpentine plants and aims to provide a state of the art and to present possible future directions for research which could lead to new insights on microbial adaptation and evolution, and potentially applied in technologies for sustainable use and remediation of contaminated land.