TY - JOUR
T1 - Ancient Heavy Metal Contamination in Soils as a Driver of Tolerant Anthyllis vulneraria Rhizobial Communities
AU - Mohamad, Roba
AU - Maynaud, Geraldine
AU - Le Quéré, Antoine
AU - Vidal, Céline
AU - Klonowska, Agnieszka
AU - Yashiro, Erika
AU - Cleyet-Marel, Jean-Claude
AU - Brunel, Brigitte
N1 - Copyright © 2016 American Society for Microbiology.
PY - 2017/1/15
Y1 - 2017/1/15
N2 - Anthyllis vulneraria is a legume associated with nitrogen-fixing rhizobia that together offer an adapted biological material for mine-soil phytostabilization by limiting metal pollution. To find rhizobia associated with Anthyllis at a given site, we evaluated the genetic and phenotypic properties of a collection of 137 rhizobia recovered from soils presenting contrasting metal levels. Zn-Pb mine soils largely contained metal-tolerant rhizobia belonging to Mesorhizobium metallidurans or to another sister metal-tolerant species. All of the metal-tolerant isolates harbored the cadA marker gene (encoding a metal-efflux PIB-type ATPase transporter). In contrast, metal-sensitive strains were taxonomically distinct from metal-tolerant populations and consisted of new Mesorhizobium genospecies. Based on the symbiotic nodA marker, the populations comprise two symbiovar assemblages (potentially related to Anthyllis or Lotus host preferences) according to soil geographic locations but independently of metal content. Multivariate analysis showed that soil Pb and Cd concentrations differentially impacted the rhizobial communities and that a rhizobial community found in one geographically distant site was highly divergent from the others. In conclusion, heavy metal levels in soils drive the taxonomic composition of Anthyllis-associated rhizobial populations according to their metal-tolerance phenotype but not their symbiotic nodA diversity. In addition to heavy metals, local soil physicochemical and topoclimatic conditions also impact the rhizobial beta diversity. Mesorhizobium communities were locally adapted and site specific, and their use is recommended for the success of phytostabilization strategies based on Mesorhizobium-legume vegetation.IMPORTANCE: Phytostabilization of toxic mine spoils limits heavy metal dispersion and environmental pollution by establishing a sustainable plant cover. This eco-friendly method is facilitated by the use of selected and adapted cover crop legumes living in symbiosis with rhizobia that can stimulate plant growth naturally through biological nitrogen fixation. We studied microsymbiont partners of a metal-tolerant legume, Anthyllis vulneraria, which is tolerant to very highly metal-polluted soils in mining and nonmining sites. Site-specific rhizobial communities were linked to taxonomic composition and metal tolerance capacity. The rhizobial species Mesorhizobium metallidurans was dominant in all Zn-Pb mines but one. It was not detected in unpolluted sites where other distinct Mesorhizobium species occur. Given the different soil conditions at the respective mining sites, including their heavy-metal contamination, revegetation strategies based on rhizobia adapting to local conditions are more likely to succeed over the long term compared to strategies based on introducing less-well-adapted strains.
AB - Anthyllis vulneraria is a legume associated with nitrogen-fixing rhizobia that together offer an adapted biological material for mine-soil phytostabilization by limiting metal pollution. To find rhizobia associated with Anthyllis at a given site, we evaluated the genetic and phenotypic properties of a collection of 137 rhizobia recovered from soils presenting contrasting metal levels. Zn-Pb mine soils largely contained metal-tolerant rhizobia belonging to Mesorhizobium metallidurans or to another sister metal-tolerant species. All of the metal-tolerant isolates harbored the cadA marker gene (encoding a metal-efflux PIB-type ATPase transporter). In contrast, metal-sensitive strains were taxonomically distinct from metal-tolerant populations and consisted of new Mesorhizobium genospecies. Based on the symbiotic nodA marker, the populations comprise two symbiovar assemblages (potentially related to Anthyllis or Lotus host preferences) according to soil geographic locations but independently of metal content. Multivariate analysis showed that soil Pb and Cd concentrations differentially impacted the rhizobial communities and that a rhizobial community found in one geographically distant site was highly divergent from the others. In conclusion, heavy metal levels in soils drive the taxonomic composition of Anthyllis-associated rhizobial populations according to their metal-tolerance phenotype but not their symbiotic nodA diversity. In addition to heavy metals, local soil physicochemical and topoclimatic conditions also impact the rhizobial beta diversity. Mesorhizobium communities were locally adapted and site specific, and their use is recommended for the success of phytostabilization strategies based on Mesorhizobium-legume vegetation.IMPORTANCE: Phytostabilization of toxic mine spoils limits heavy metal dispersion and environmental pollution by establishing a sustainable plant cover. This eco-friendly method is facilitated by the use of selected and adapted cover crop legumes living in symbiosis with rhizobia that can stimulate plant growth naturally through biological nitrogen fixation. We studied microsymbiont partners of a metal-tolerant legume, Anthyllis vulneraria, which is tolerant to very highly metal-polluted soils in mining and nonmining sites. Site-specific rhizobial communities were linked to taxonomic composition and metal tolerance capacity. The rhizobial species Mesorhizobium metallidurans was dominant in all Zn-Pb mines but one. It was not detected in unpolluted sites where other distinct Mesorhizobium species occur. Given the different soil conditions at the respective mining sites, including their heavy-metal contamination, revegetation strategies based on rhizobia adapting to local conditions are more likely to succeed over the long term compared to strategies based on introducing less-well-adapted strains.
KW - Acyltransferases/genetics
KW - Bacterial Proteins/genetics
KW - Biodegradation, Environmental
KW - DNA, Bacterial/genetics
KW - Fabaceae/microbiology
KW - France
KW - Germany
KW - Mesorhizobium/classification
KW - Metals, Heavy/toxicity
KW - Mining
KW - Phylogeny
KW - RNA, Ribosomal, 16S/genetics
KW - Rec A Recombinases/genetics
KW - Seasons
KW - Sequence Analysis, DNA
KW - Soil Microbiology
KW - Soil Pollutants/toxicity
KW - Symbiosis/drug effects
U2 - 10.1128/AEM.01735-16
DO - 10.1128/AEM.01735-16
M3 - Journal article
C2 - 27793823
SN - 0099-2240
VL - 83
JO - Applied and Environmental Microbiology
JF - Applied and Environmental Microbiology
IS - 2
M1 - e01735-16
ER -