The Bacterial and Fungal Microbiota of Hyperaccumulator Plants: Small Organisms, Large Influence

Abstract

Hyperaccumulator plants can take up large amounts of metals in their shoots without showing significant signs of toxicity. This makes hyperaccumulators ideal candidates for metal phytoremediation and phytomining. Hyperaccumulation of metals does not only depend on the bioavailability of the metals in soil and the expression of detoxification genes and metal transporters provided by the plant, but also on the plant-associated microbiota. Studies using culture-dependent strategies have shown that hyperaccumulator plants carry a high diversity of bacteria and fungi in the rhizosphere and endosphere, some of which are shown to have potential for assisting plants to grow in metal-contaminated soil and regulating plant metal uptake. However, there is yet little information available about the total microbial communities and their functions associated with the majority of hyperaccumulators known to date. Culture-independent molecular techniques and next generation sequencing allow to uncover a broader diversity of microbial species than the classical 1% cultivable fraction and can provide unprecedented insights in microbial community functions. Some unique microbial groups that are highly abundant in heavy contaminated sites have been detected in this way and have great potential for improving the efficiency of metal phytoextraction. This chapter provides the latest insights in the plant-associated microbiota of common hyperaccumulator plant species and discusses on the implications, and future prospects, of exploiting the microbiome for enhancing metal uptake by plants.