Short-Term Rhizosphere Effect on Available Carbon Sources, Phenanthrene Degradation, and Active Microbiome in an Aged-Contaminated Industrial Soil

Abstract

Over the last decades, understanding of the effects of plants on soil microbiomes has greatly advanced. However, knowledge on the assembly of rhizospheric communities in aged-contaminated industrial soils is still limited, especially with regard to transcriptionally active microbiomes and their link to the quality or quantity of carbon sources. We compared the short-term (2–10 days) dynamics of bacterial communities and potential PAH-degrading bacteria in bare or ryegrass-planted aged-contaminated soil spiked with phenanthrene, put in relation with dissolved organic carbon (DOC) sources and polycyclic aromatic hydrocarbon (PAH) pollution. Both resident and active bacterial communities (analyzed from DNA and RNA, respectively) showed higher species richness and smaller dispersion between replicates in planted soils. Root development strongly favored the activity of Pseudomonadales within the first 2 days, and of members of Actinobacteria, Caulobacterales, Rhizobiales, and Xanthomonadales within 6–10 days. Plants slowed down the dissipation of phenanthrene, while root exudation provided a cocktail of labile substrates that might preferentially fuel microbial growth. Although the abundance of PAH-degrading genes increased in planted soil, their transcription level stayed similar to bare soil. In addition, network analysis revealed that plants induced an early shift in the identity of potential phenanthrene degraders, which might influence PAH dissipation on the long-term.

Characterization of the belowground microbial community in a poplar-assisted bioremediation strategy for restoring a multi-contaminated soil

“…This means that the planting layout of the poplars (0.5 × 2m) was effective in ensuring that their root development positively stimulated the overall microbial community in each planted plot. The positive "rhizosphere effect" has been reported by other authors [26,27] and was presumably due to the root surface releasing several organic compounds into the adjacent soil. Roots release low-molecular-weight exudates (e.g.…”

pH is the primary determinant of the bacterial community structure in agricultural soils impacted by polycyclic aromatic hydrocarbon pollution

“…It has been previously observed that abundance of PAH-RHDα gene was often changed by root exudates23, organic matter24 and pH25. Controlled experiments with more comprehensive and sensitive tests, for example the transcription activities analysis2627 are therefore required to reveal the effects of PAH pollution on degrader community.…”

Below‐ground connections underlying above‐ground food production: a framework for optimising ecological connections in the rhizosphere

“…While there is accumulating evidence that plant traits, and in particular root traits, can predict soil faunal and microbial community structure and functioning (De Vries et al 2012b;Grigulis et al 2013;Legay et al 2016), there is only limited evidence that links plant traits to soil microbial networks. For example, it has been shown that specific compounds in root exudates can promote the formation of bacterial clusters (Thomas & Cebron 2016). In addition, in a mesocosm study with eucalyptus seedlings, networks of ammonia-oxidising archaea were more connected and had more modules in soil under elevated CO 2 than those under control conditions, presumably through changes in below-ground plant C inputs (Hu et al 2016).…”