title: Use of Endophytic and Rhizosphere Bacteria To Improve Phytoremediation of Arsenic-Contaminated Industrial Soils by Autochthonous Betula celtiberica.
abstract: The aim of this study was to investigate the potential of indigenous arsenic-tolerant bacteria to enhance arsenic phytoremediation by the autochthonous pseudometallophyteBetula celtibericaThe first goal was to perform an initial analysis of the entire rhizosphere and endophytic bacterial communities of the above-named accumulator plant, including the cultivable bacterial species.B. celtiberica's microbiome was dominated by taxa related toFlavobacteriales,Burkholderiales, andPseudomonadales, especially thePseudomonasandFlavobacteriumgenera. A total of 54 cultivable rhizobacteria and 41 root endophytes, mainly affiliated with the phylaProteobacteria,Bacteroidetes,Firmicutes, andActinobacteria, were isolated and characterized with respect to several potentially useful features for metal plant accumulation, such as the ability to promote plant growth, metal chelation, and/or mitigation of heavy-metal stress. Seven bacterial isolates were further selected and tested forin vitroaccumulation of arsenic in plants; four of them were finally assayed in field-scale bioaugmentation experiments. The exposure to arsenicin vitrocaused an increase in the total nonprotein thiol compound content in roots, suggesting a detoxification mechanism through phytochelatin complexation. In the contaminated field, the siderophore and indole-3-acetic acid producers of the endophytic bacterial consortium enhanced arsenic accumulation in the leaves and roots ofBetula celtiberica, whereas the rhizosphere isolateEnsifer adhaerensstrain 91R mainly promoted plant growth. Field experimentation showed that additional factors, such as soil arsenic content and pH, influenced arsenic uptake in the plant, attesting to the relevance of field conditions in the success of phytoextraction strategies.IMPORTANCEMicroorganisms and plants have developed several ways of dealing with arsenic, allowing them to resist and metabolize this metalloid. These properties form the basis of phytoremediation treatments and the understanding that the interactions of plants with soil bacteria are crucial for the optimization of arsenic uptake. To address this in our work, we initially performed a microbiome analysis of the autochthonousBetula celtibericaplants growing in arsenic-contaminated soils, including endosphere and rhizosphere bacterial communities. We then proceeded to isolate and characterize the cultivable bacteria that were potentially better suited to enhance phytoextraction efficiency. Eventually, we went to the field application stage. Our results corroborated the idea that recovery of pseudometallophyte-associated bacteria adapted to a large historically contaminated site and their use in bioaugmentation technologies are affordable experimental approaches and potentially very useful for implementing effective phytoremediation strategies with plants and their indigenous bacteria.
authors.affiliation: Departamento de Biología Funcional-IUBA, Universidad de Oviedo, Oviedo, Spain victoriamesa@gmail.com.
authors.forename: Victoria
authors.identifier: http://orcid.org/0000-0003-2615-7033
authors.initials: V
authors.lastname: Mesa
authors.affiliation: Departamento de Biología de Organismos y Sistemas-IUBA, Universidad de Oviedo, Oviedo, Spain.|Centre for Environmental Sciences (CMK), Hasselt University, Hasselt, Belgium.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Navazas
authors.affiliation: Departamento de Biología de Organismos y Sistemas-IUBA, Universidad de Oviedo, Oviedo, Spain.
authors.forename: Ricardo
authors.initials: R
authors.lastname: González-Gil
authors.affiliation: Departamento de Biología de Organismos y Sistemas-IUBA, Universidad de Oviedo, Oviedo, Spain.
authors.forename: Aida
authors.initials: A
authors.lastname: González
authors.affiliation: Centre for Environmental Sciences (CMK), Hasselt University, Hasselt, Belgium.
authors.forename: Nele
authors.initials: N
authors.lastname: Weyens
authors.affiliation: Equipe Environnement et Microbiologie (EEM), CNRS/Univ. Pau et des Pays Adour, Institut des sciences analytiques et de physico-chimie pour l'environnement et les matériaux-IPREM, UMR5254, Pau, France.
authors.forename: Béatrice
authors.initials: B
authors.lastname: Lauga
authors.affiliation: Departamento de Explotación y Prospección Minera-IUBA, Universidad de Oviedo, Mieres, Spain.
authors.forename: Jose Luis R
authors.initials: JLR
authors.lastname: Gallego
authors.affiliation: Departamento de Biología Funcional-IUBA, Universidad de Oviedo, Oviedo, Spain.
authors.forename: Jesús
authors.initials: J
authors.lastname: Sánchez
authors.affiliation: Departamento de Biología Funcional-IUBA, Universidad de Oviedo, Oviedo, Spain.
authors.forename: Ana Isabel
authors.initials: AI
authors.lastname: Peláez
mesh_terms: D001151:Arsenic / Q000378:metabolism* / Q000494:pharmacology; D001419:Bacteria / Q000737:chemistry / Q000145:classification / Q000187:drug effects / Q000378:metabolism*; D029662:Betula / Q000737:chemistry / Q000382:microbiology* / Q000502:physiology; D001673:Biodegradation, Environmental; D060026:Endophytes / Q000378:metabolism*; D005417:Flavobacterium / Q000187:drug effects / Q000302:isolation & purification / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007210:Indoleacetic Acids / Q000378:metabolism; D007220:Industrial Waste; D059013:Microbial Consortia / Q000502:physiology*; D063245:Plant Development; D018515:Plant Leaves / Q000737:chemistry; D018517:Plant Roots / Q000737:chemistry / Q000382:microbiology; D011549:Pseudomonas / Q000187:drug effects / Q000302:isolation & purification / Q000378:metabolism; D058441:Rhizosphere; D012989:Soil Pollutants / Q000032:analysis / Q000378:metabolism*
chemical_list: D007210:Indoleacetic Acids; D007220:Industrial Waste; D012989:Soil Pollutants; C030737:indoleacetic acid; D001151:Arsenic
keywords: Betula; arsenic; bioaugmentation; contaminated soil; field-scale study; phytoextraction; rhizobacteria; root endophytes