Taxonomic and functional responses of soil and root bacterial communities associated with poplar exposed to a contamination gradient of phenanthrene

Abstract

Polycyclic aromatic hydrocarbon (PAH) contamination of industrial wasteland soils affects microbial diversity, but little is known about the dose-response effects of such contaminants on taxonomic and functional diversities of rhizospheric and plant endophytic bacteria. This study focused on the response of soil and root bacterial communities associated to poplar grown in a contamination gradient of phenanthrene (PHE). It was hypothesized that the increase in contamination would modify gradually the bacterial diversity and functions. The effects of the PHE contamination were limited to soil communities and did not affect the poplar root endophytome where Streptomyces and Cutibacterium were the most abundant genera. Along the PHE gradient, alpha-diversity indices decreased and the community structure of soil bacteria at the taxonomic level shifted. The abundance of genes involved in PAH-degradation pathways and the relative proportion of certain microbial taxa such as Polaromonas, Sphingopyxis, Peredibacter, Phenylobacterium, Ramlibacter, Sphingomonas, Pseudomonas, often described as potential PAH biodegraders, increased with the PHE concentration in the soil community. Conversely, the contamination negatively impacted other taxa like Nocardioides, Streptomyces, Gaiella, Solirubrobacter, Bradyrhizobium and Nitrospira. Functional inference and enzymatic activity measurements revealed that some bacterial functions related to carbon, nitrogen and phosphorus cycles were modified in soil throughout the PHE gradient. This study allowed a deeper understanding of the complex plant-bacteria interactions in the case of soil PAH contamination and the potential impact on soil functioning.

Editorial: thematic issue on microbial ecotoxicology

“…Another series of papers illustrates the diverse ways by which the response of microbial strains and communities to chemicals can be used for bioindication (Narciso et al 2023 ), as well as for toxicological risk assessment for individual species (Helander et al 2023 ) and higher-level biomes, e.g. microbial–plant interactions (Gkimprixi et al 2023 , Gréau et al 2023 ).…”