Chemolithoautotrophic Antimonite Oxidation Coupled Nitrogen Fixation in the Rhizosphere of Local Plant in Antimony Tailing Area

Antimony (Sb) tailings pose a significant environmental
challenge.
N-fixing microorganisms are essential for nutrient accumulation and
plant colonization in degraded habitats. However, the oligotrophic
conditions of tailings often inhibit the energy-intensive N-fixing
process. This study identified a chemolithoautotrophic Sb(III) oxidation-coupled
nitrogen fixation (SbNF) pathway in the rhizosphere of local plants.
SbNF integrates biological detoxification and nutrient accumulation,
enabling plant colonization and ecological restoration of degraded
habitats. Multi-omic analyses reveal that Sb content
strongly shapes the composition of Sb-oxidizing and N-fixing bacterial
communities in the rhizosphere. Abundant marker genes for carbon fixation
(cbbL), Sb(III) oxidase (aioAB/anoA), and nitrogenase (nifH) were consistently detected
in SbNF metagenome-assembled genomes. Positive correlations between
gene abundances associated with autotrophic potential (aioA-cbbL) and coupling potential (aioA-nifH) were observed in the rhizoplane but not in
the endosphere. In addition to genetic potentials, high-throughput
cultivation of native SbNF-isolates (e.g., Pseudomonas, Arthrobacter, and Sphingomonas) confirmed their rapid Sb(III) oxidation coupling autotrophic growth
and nitrogen fixation. Isolates also exhibited plant growth-promoting
traits, including indole-3-acetic acid production, phosphate solubilization,
and siderophore secretion, providing multiple benefits to host plants.
Co-cultivation of these isolates revealed minimal antagonism, suggesting
the potential for designing synthetic microbial communities for sustainable
phytoremediation. Cross-validation further suggests that SbNF is widespread
in the rhizosphere of various local plants. These findings uncover
a novel biogeochemical process in the rhizosphere, linking mineral
oxidation, autotrophic growth, and nitrogen fixation, highlighting
its importance for the ecological restoration of degraded tailing
area.