Induction of phytoextraction, phytoprotection and growth promotion activities in Lupinus albus under mercury abiotic stress conditions by Peribacillus frigoritolerans subsp., mercuritolerans subsp. nov.

Strain SAICEUPBM was isolated from soils of Almadén (Ciudad Real, Spain), subjected to a high mercury concentration. SAICEUPBM significantly increased aerial plant weight, aerial plant length and the development of secondary roots under mercury stress; increased twice the absorption of mercury by the plant, while favoring its development in terms of biomass. Similarly, plants inoculated with SAICEUPBM and grown in soils contaminated with mercury, express a lower activity of antioxidant enzymes; catalase enzymes (CAT), superoxide dismutase (SOD), ascorbate peroxidase (APX), glutathione reductase (GR) for defense against ROS (reactive oxygen species). Whole genome analysis showed that ANI (95. 96 %), dDDH (72.9 %), AAI (93.3 %) and TETRA (0.99) values were on the thresholds established for differentiation a subspecies. The fatty acids analysis related the strain with the Peribacillus frigoritolerans species. And the synapomorphic analysis reveals a common ancestor with analysis related the strain with the Peribacillus frigoritolerans species. Results from genomic analysis together with differences in phenotypic features and chemotaxonomic analysis support the proposal of strain SAICEUPBM as the type strain of a novel subspecies for which the name Peribacillus frigoritolerans subps. mercuritolerans sp. nov is proposed. The absence of virulence genes and transmissible resistance mechanisms reveals its safety for agronomic uses, under mercury stress conditions. The ability of Peribacillus frigoritolerans subsp. mercuritolerans subsp. nov to improve plant development was tested in a Lupinus albus model, demonstrating a great potential for plant phytoprotection against mercury stress.