In recent years, the tree of life has expanded substantially. Despite this, many abundant yet uncultivated microbial groups remain to be explored.

Electron acceptor redox potential (EARP) was presumed to be a determining factor for microbial metabolism in many natural and engineered processes. However, little is known about the potentially global effects of EARP on bacteria. In this study, we compared the physiological and transcriptomic properties of Shewanella decolorationis S12 respiring with different EARPs in microbial electrochemical systems to avoid the effects caused by the other physicochemical properties of real electron acceptor. Results showed that the metabolic activities of strain S12 were nonlinear responses to EARP. The tricarboxylic acid cycle for central carbon metabolism was down-regulated while glyoxylate shunt was up-regulated at 0.8 V compared to 0.2 and −0.2 V, which suggested that EARP is an important but not the only determinant for metabolic pathways of strain S12. Moreover, few cytochrome c genes were differentially expressed at different EARPs. The energy intensive flagella assembly and assimilatory sulfur metabolism pathways were significantly enriched at 0.8 V, which suggested strain S12 had stronger electrokinesis behavior and oxidative stress-response at high EARP. This study provides the first global information of EARP regulations on microbial metabolism, which will be helpful for understanding microorganism respiration.

Microbial community play a fundamental role in primary succession of tailings ecosystems. However, the influence of heavy metal pollution on microbial interactions and assembly dynamics during this process remains poorly understood. In this study, we investigated bacterial and fungal communities in tailing soil and biological soil crusts (BSCs) undergoing primary succession under varying heavy metal pollution. By integrating microbial community profiling with measurements of soil nutrients and heavy metal concentrations, we aimed to elucidate how pollution levels shape microbial composition, co-occurrence networks, and assembly processes. Our results revealed clear differences in soil physicochemical properties, microbial diversity, community structure, and ecological interactions between low and high pollution conditions. Under high contamination, Burkholderiales dominated the bacterial communities, while Saccharomycetales and Pleosporales were representative among fungi. Microbial diversity decreased with increasing pollution, accompanied by simplified co-occurrence networks and increased modularity. In highly polluted environments, both bacterial and fungal communities exhibited stronger correlations with environmental factors. Interestingly, bacterial communities were more strongly associated with soil nutrient parameters, whereas fungal communities responded more closely to heavy metal concentrations. Community assembly analysis further showed a shift toward deterministic processes in bacterial communities under high pollution, while fungal assembly remained largely stochastic. These findings highlight the differential responses of bacterial and fungal communities to heavy metal stress and underscore the critical role of pollution in shaping microbial succession in tailing ecosystems. This study provides important insights into microbial ecology under environmental stress and may inform strategies for the bioremediation and management of contaminated mine lands.

The microbial method for the treatment of azo dye is promising, but the reduction of azo dye is the rate-limiting step. Zero valent iron (Fe0) can enhance microbial azo reduction, but the interactions between microbes and Fe0 and the potential mechanisms of enhancement remain unclear. Here, Shewanella decolorationis S12, a typical azo-reducing bacterium, was used to characterize the enhancement of Fe0 on microbial decolorization. The results indicated that anaerobic iron corrosion was a key inorganic chemical process for the enhancement of Fe0 on microbial azo reduction, in which OH−, H2, and Fe2+ were produced. Once Fe0 was added to the microbial azo reduction system, the proper pH for microbial azo reduction was maintained by OH−, and H2 served as the favored electron donor for azo respiration. Subsequently, the bacterial biomass yield and viability significantly increased. Following the corrosion of Fe0, nanometer-scale Fe precipitates were adsorbed onto cell surfaces and even accumulated inside cells as observed by transmission electron microscope energy dispersive spectroscopy (TEM-EDS). A conceptual model for Fe0-assisted azo dye reduction by strain S12 was established to explain the interactions between microbes and Fe0 and the potential mechanisms of enhancement. This model indicates that the enhancement of microbial azo reduction in the presence of Fe0 is mainly due to the stimulation of microbial growth and activity by supplementation with elemental iron and H2 as an additional electron donor. This study has expanded our knowledge of the enhancement of microbial azo reduction by Fe0 and laid a foundation for the development of Fe0-microbial integrated azo dye wastewater treatment technology.

The WOR-3 phylum is widely distributed in various environments, including hot springs, marine ecosystems, and hydrothermal vents, yet its ecological roles and metabolic capabilities remain poorly understood. In this study, we analyzed 181 medium- to high-quality metagenome-assembled genomes, including 59 newly reconstructed from environmental samples and 122 retrieved from public databases. Phylogenetic analyses resolved the WOR-3 lineage into four subgroups (subgroup 1–4). Metabolic reconstruction revealed significant divergence of the carbon, sulfur, nitrogen, and hydrogen metabolism pathways among the different subgroups. Subgroup 1 was characterized by fermentative metabolism involving formate and ethanol and uniquely exhibited potential for carbon fixation via the Calvin cycle, as indicated by the presence of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) gene. Notably, WOR-3 RuBisCO is phylogenetically affiliated with archaeal form III, although the carbon fixation pathway follows the canonical bacterial Calvin cycle—a feature of potential evolutionary significance. Subgroup 3 exhibits metabolic versatility, including genes for dissimilatory sulfate reduction, sulfur oxidation, partial denitrification, and fatty acid degradation. In addition, all subgroups harbored key components of hydrogen metabolism, including widespread NiFe hydrogenases, supporting H ₂ -dependent electron transfer and energy conservation. Within the WOR-3 lineage, the coexistence of two respiratory enzyme systems—the Rnf complex and the oxidative phosphorylation respiratory chain—indicates distinct anaerobic and aerobic metabolic lifestyles, respectively. Collectively, this study expands the genomic framework for the WOR-3 phylum and provides novel insights into the metabolic versatility and ecological functions of this previously uncharacterized lineage in biogeochemical cycles of carbon, nitrogen, and sulfur. IMPORTANCE: The WOR-3 phylum represents a widespread but poorly understood bacterial lineage inhabiting diverse various environments. By integrating 181 metagenome-assembled genomes, including 59 newly reconstructed, this study provides the most comprehensive genomic framework to date for WOR-3. Phylogenomic and metabolic reconstruction revealed four distinct subgroups with divergent capacities for carbon, sulfur, and nitrogen metabolism. Notably, subgroup 1 encodes a complete Calvin-Benson-Bassham cycle featuring an archaeal-type form III ribulose-1,5-bisphosphate carboxylase/oxygenase, suggesting an unusual evolutionary trajectory for carbon fixation in this lineage. Subgroup 3 exhibits versatile metabolic potential, including dissimilatory sulfur metabolism, partial denitrification, and fatty acid degradation, highlighting its possible roles in multiple biogeochemical processes. These findings not only expand the taxonomic and functional landscape of the WOR-3 phylum but also offer key insights into its ecological roles in global element cycling.