The genomes of three Bradyrhizobium sp. isolated from root nodules of Lupinus albescens grown in extremely poor soils display important genes for resistance to environmental stress

Abstract

Lupinus albescens is a resistant cover plant that establishes symbiotic relationships with bacteria belonging to the Bradyrhizobium genus. This symbiosis helps the development of these plants in adverse environmental conditions, such as the ones found in arenized areas of Southern Brazil. This work studied three Bradyrhizobium sp. (AS23, NAS80 and NAS96) isolated from L. albescens plants that grow in extremely poor soils (arenized areas and adjacent grasslands). The genomes of these three strains were sequenced in the Ion Torrent platform using the IonXpress library preparation kit, and presented a total number of bases of 1,230,460,823 for AS23, 1,320,104,022 for NAS80, and 1,236,105,093 for NAS96. The genome comparison with closest strains Bradyrhizobium japonicum USDA6 and Bradyrhizobium diazoefficiens USDA110 showed important variable regions (with less than 80% of similarity). Genes encoding for factors for resistance/tolerance to heavy metal, flagellar motility, response to osmotic and oxidative stresses, heat shock proteins (present only in the three sequenced genomes) could be responsible for the ability of these microorganisms to survive in inhospitable environments. Knowledge about these genomes will provide a foundation for future development of an inoculant bioproduct that should optimize the recovery of degraded soils using cover crops.

Presence of Bradyrhizobium sp. under Continental Conditions in Central Europe

“…could be mapped during the sequencing, it must be taken into account that Bradyrhizobia can also be hosted by other legumes, such as lupines. There is evidence of this in Brazil [24], USA [25], and Spain and Chile [26], where Bradyrhizobia was isolated from different lupine species. For the field control (C BW) and the other samples from the Pillnitz experimental station, however, this can be ruled out, as no cultivation with lupines has yet taken place on this site.…”

Taxonomic and functional analysis of soil microbial communities in a mining site across a metal(loid) contamination gradient

“…Several works have reported that these microsymbionts have a key role in the adaptation of legumes to soils poor in nitrogen and with high contents of metals and As (Fagorzi et al, 2018). For example, species from the genus Bradyrhizobium are found associated with the legume Glycine max growing in soils with a high content of As, and with the legume Lupinus luteus in soils with high concentrations of Cu, Cd and Pb (Fagorzi et al, 2018;Granada et al, 2018). The great abundance of Bradyrhizobium in the soil samples of our study may be related to the presence of Retama sphaerocarpa, a leguminous plant observed across the three sampling areas (A, B and C).…”