Assembly strategies of the wheat root-associated microbiome in soils contaminated with phenanthrene and copper

Abstract

Plants can cope with stressful conditions by indirectly regulating root-associated microbial structures. However, the recruitment strategies of the root-associated microbiome in combined organic and inorganic contaminated soils are not well known, especially for common agricultural crops. In this study, we performed greenhouse experiments to investigate the interactive effects of joint copper (Cu) and phenanthrene (PHE) pollution on wheat growth and microbial detoxication processes. Results show that heavy metals did not affect PHE dissipation in the rhizosphere but significantly enhanced the accumulation of PHE in the endosphere. In contrast, the addition of PHE did not influence the absorption of Cu by wheat roots. Cu was the primary factor affecting the variation of microbial communities in cocontaminated treatments among each rhizocompartment while the interactive effects of combined pollutants were only detected in unplanted bulk soil. Microbes are known to degrade polycyclic aromatic hydrocarbons and tolerant heavy metal stress e.g. Novosphingobium, Sphingomonas, Sphingobium and Pseudomonas enriched in the contaminated treatments. Our results provide an integrated understanding of the synthetic effects of combined pollutants on the root-microbial assemblage process in plant-soil systems and offer useful information on the selection of effective bioremediating root-associated microbes for the application of self-remediation by common crops.

Keywords: Heavy metals; Interactive effects; Metal-tolerant microbes; Plant growth promoting rhizobacteria; Polycyclic aromatic hydrocarbons.