Microbial community structure and functional potential in a long-term uranium-nickel contaminated ecosystem

Area of Science:

• Environmental Microbiology
• Geomicrobiology
• Soil Science

Background:

• The Savannah River Site (SRS) is a legacy nuclear materials production facility with long-term uranium (U) and nickel (Ni) soil contamination.
• Acidic wastewater discharge has led to spatially variable U and Ni contamination, impacting microbial ecosystems.

Purpose of the Study:

• To investigate the microbial community structure, functional potential, and resistance determinants in U- and Ni-contaminated SRS soils.
• To understand microbial adaptation and potential for bioremediation in legacy nuclear-contaminated environments.

Main Methods:

• Soil cores were collected from the Steed Pond area with characterized U and Ni concentrations.
• Shotgun metagenomic sequencing and high-throughput quantitative PCR (HT-qPCR) were employed to analyze microbial communities and functional genes.

Main Results:

• Bacterial communities were dominated by Pseudomonadota, Actinomycetota, and Acidobacteriota, with enrichment of diazotrophic genera.
• Nitrogen fixation-related genes were abundant, while carbon and nitrogen cycle genes showed pathway-specific shifts.
• A significant number of antibiotic-resistance genes (ARGs), metal-resistance genes (MRGs), and mobile genetic elements (MGEs) were identified, indicating co-selection and horizontal gene transfer.

Conclusions:

• Long-term U-Ni contamination selects for metabolically versatile, diazotroph-enriched, and genetically mobile microbiomes.
• These adapted microbial communities exhibit resistance proliferation and hold potential for bioremediation in contaminated soils.