Toward understanding submersed macrophyte Vallisneria natans-microbe partnerships to improve remediation potential for PAH-contaminated sediment.

Rhizodegradation using submersed macrophytes Vallisneria natans (V. natans) is a promising biotechnology with the potential to restore polycyclic aromatic hydrocarbon (PAH)-contaminated sediments. However, how different sediment types influence the rhizoremediation outcome and the characterization of microbial community along the sediment-V. natans continuum is poorly understood. Here, we collect V. natans, sediments and overlying water from two types of vegetation zones with different levels of PAHs pollutions and set up sediment microcosms for phytoremediation tests. V. natans presence was particularly useful for PAHs remediation in the highly contaminated sites and had a significant effect on PAHs rhizodegradation and microbial communities, especially rhizosphere sediments. The structural composition of microbial communities along the sediment-plant continuum was shaped predominantly by compartment niche of V. natans. Moreover, selective enrichment of specific microbial taxa like Herbaspirillum (relative abundance = 94.80%) in endosphere of V. natans was observed. Herbaspirillum could use PAH as carbon source and promote the growth of plants. In the highly contaminated sediment, V. natans could recruit these bacteria for toxicant degradation into the root interior. Thus, understanding the complex V. natans-microbe interactions could help set up novel decontamination strategies based on the rhizosphere and root interior interactions between plants and their microbial associates.