# Insights into uranium enrichment of indigenous electroactive Shewanella putrefaciens

## TL;DR

A native strain of Shewanella putrefaciens from uranium mine tailings shows high uranium removal efficiency and unique genetic traits for bioremediation.

## Contribution

The study reveals the genetic and mechanistic basis for uranium enrichment in an indigenous Shewanella putrefaciens strain.

## Key findings

- The isolated strain achieved 93% uranium removal efficiency.
- Genomic analysis showed enrichment of genes related to energy metabolism and stress resistance.
- The Mtr pathway was identified as crucial for uranium reduction via extracellular electron transfer.

## Abstract

Bioremediation of uranium-contaminated environments using native bacteria shows great promise. While Shewanella putrefaciens (S. putrefaciens) is a known uranium reducing bacterium, the mechanisms and adaptability of indigenous strains from uranium mine tailings remain unexplored. This study isolated a dominant indigenous strain of S. putrefaciens and employed a combined genomic and spectroscopic approach to elucidate its unique uranium fixation mechanism. Microbial diversity analysis confirmed the dominance of Shewanella in the oligotrophic and radioactive tailings. Whole-genome sequencing revealed a significant enrichment of genes related to energy metabolism and stress resistance, providing a genetic basis for its survival and activity. Crucially, by combining advanced spectroscopic techniques with an MtrA gene knockout experiment, we deciphered the specific role of the Mtr pathway in extracellular electron transfer for uranium reduction. Remarkably, the isolated strain achieved a uranium removal efficiency of up to 93% under experimental conditions, demonstrating its high potential for uranium bioremediation. This work not only provides a robust indigenous candidate for bioremediation but also delivers novel mechanistic insights into the uranium transformation processes of indigenous Shewanella, advancing strategies for the application of tailored microbiomes in radioactive waste management.

Diagram illustrating the process of U(VI) removal involving Shewanella, Alcaligenes, and Sporacetigenium. On the left, S. putrefaciens is isolated from soil under a sun, indicating energy metabolic conversion and defense mechanisms. A chart shows 16S rDNA and whole gene analysis. On the right, a cell model depicts U(VI) removal mechanisms: biosorption, biomineralization, bioaccumulation, and bioreduction via the Mtr pathway and TCA cycle. Symbols represent phosphate, enzymes, amino, carboxyl, U(VI), and U(IV).