Effects of Zinc Pollution and Compost Amendment on the Root Microbiome of a Metal Tolerant Poplar Clone

Abstract

Until recently, many phytoremediation studies were focused solely on a plants ability to reclaim heavy metal (HM) polluted soil through a range of different processes, such as phytoextraction and phytostabilization. However, the interaction between plants and their own rhizosphere microbiome represents a new research frontier for phytoremediation. Our hypothesis is that rhizomicrobiome might play a key role in plant wellness and in the response to external stimuli; therefore, this study aimed to shed light the rhizomicrobiome dynamics after an organic amendment (e.g., compost) and/or HM pollution (e.g., Zn), and its relation with plant reclamation ability. To reach this goal we set up a greenhouse experiment cultivating in pot an elite black poplar clone (N12) selected in the past for its excellent ability to reclaim heavy metals. N12 saplings were grown on a soil amended with compost and/or spiked with high Zn doses. At the end of the experiment, we observed that the compost amendment strongly increased the foliar size but did not affect significantly the Zn accumulation in plant. Furthermore, the rhizomicrobiome communities (bacteria and fungi), investigated through NGS, highlighted how α diversity increased in all treatments compared to the untreated N12 saplings. Soil compost amendment, as well as Zn pollution, strongly modified the bacterial rhizomicrobiome structure. Conversely, the variation of the fungal rhizomicrobiome was only marginally affected by soil Zn addition, and only partially impaired by compost. Nevertheless, substantial alterations of the fungal community were due to both compost and Zn. Together, our experimental results revealed that organic amendment increased the bacterial resistance to external stimuli whilst, in the case of fungi, the amendment made the fungi microbiome more susceptible. Finally, the greater microbiome biodiversity does not imply, in this case, a better plant wellness or phytoremediation ability, although the microbiome plays a role in the external stimuli response supporting plant life.

Zinc Essentiality, Toxicity, and Its Bacterial Bioremediation: A Comprehensive Insight

“…Furthermore, excess levels of Zn in soil also contribute to the inhibition and alteration of soil microorganisms ( Olaniran et al, 2013 ), due to its bioavailability in the form of ionic Zn and as part of organo-metallic complexes, which have been previously determined ( Pueyo et al, 2004 ; Anju and Banerjee, 2011 ; Fedotov et al, 2012 ; Agnieszka et al, 2014 ; Kim et al, 2015 ; Baran et al, 2018 ). Therefore, efficient methods of heavy metal remediation are crucial for the alleviation of Zn toxicity in order to preserve soil microorganisms and their biodiversity, as well as plant and human health ( Guarino et al, 2020 ).…”

Peculiarities of the Edaphic Cyanobacterium Nostoc linckia Culture Response and Heavy Metal Accumulation from Copper-Containing Multimetal Systems

“…Thus, zinc is a constituent of many proteins, it is also an enzyme cofactor and is fundamental for optimum plant growth and development. However, at high concentrations in the soil, Zn is phytotoxic, and plants that accumulate it through root absorption or deposition pose a health risk to consumers [ 5 ]. Nickel is an essential micronutrient required for the growth of higher plants.…”

Toxicity effects of aged refuse on Tagetes patula and rhizosphere microbes

“…As an important component of the soil ecosystem, rhizosphere microbes are ubiquitously implicated in the regulation of plant growth and remediation of contaminated soil. A number of studies have shown that rhizospheric microbes play important roles in the corrosion of metal in soils and heavy metal tolerance in plants (Y. Chen et al, 2018; Guarino et al, 2020; Huang et al, 2021; Jiao et al, 2019). For example, three common legume plants showed clear succession and resilience patterns of the soil microbiome in response to inorganic and organic contaminants in the study of Jiao et al (Jiao et al, 2019), and they found that different legume plants displayed stronger soil microbiome taxonomic selection processes that were helpful for the growth of plants with metal tolerance ability.…”

“…A number of studies have shown that rhizospheric microbes play important roles in the corrosion of metal in soils and heavy metal tolerance in plants (Y. Chen et al, 2018;Guarino et al, 2020;Huang et al, 2021;Jiao et al, 2019).…”