Beneficial traits of root endophytes and rhizobacteria associated with poplar growing in phytomanaged soils with metal-organic contamination

KIDD PETRA; CERDEIRA-PEREZ ANDREA; ALVAREZ-LOPEZ VANESA; RODRIGUEZ-GARRIDO BEATRIZ; ALVAREZ ANALÍA; CHALOT MICHEL

Porto

Congreso; 2nd International Meeting on New Strategies in Bioremediation Processes; 2019

University of Porto

Phytomanaging contaminated soils can successfully restore biological fertility and diversity. Willow and poplar species are recognised for their metal tolerance and, in some cases, ability to extract trace metals (such as Cd and Zn) from contaminated soils. Plants used in these remediation options promote the abundance of beneficial microorganisms in their surroundings (endosphere and rhizosphere). Plant-associated bacteria can alleviate stress and improve plant development, degrade contaminants (organics) and/or alter contaminant bioavailability and plant accumulation (metals and organics). Biosurfactant-producing bacteria can enhance the solubility of organic contaminants and hence degradation. The objectives of this study were to: (a) assess the plant-associated culturable bacterial diversity under different phytomanagement options (poplar and mixed poplar-alder stands with and without mycorrhizal inoculation) in a mixed-contaminated site in Pierrelaye (France), (b) isolate root endophytes and rhizobacteria, (c) characterize bacterial strains for plant growth promoting (PGP) traits, PAHs degradation capacity, biosurfactant production and trace metal tolerance, and (d) assess the influence of biosurfactant producers on PAHs availability. Over 300 root endophytic and rhizosphere bacterial strains were isolated, grouped by amplified rDNA restriction analysis (ARDRA) and identified by 16S rDNA sequencing. Proteobacteria and Actinobacteria dominated the isolate collection, and differences in taxonomic diversity were observed amongst phytomanagement options. The majority of isolates had at least one of the PGP traits tested and were metal-resistant. Several strains were able to degrade some PAHs, and the cell-free culture of the biosurfactant-producer Rhizobium sp. MR28 increased PAHs bioavailability. Finally, several strains were selected for their potential as bioinoculants in rhizoremediation processes.