Effects of different antimony contamination levels on paddy soil bacterial diversity and community structure

Rhizosphere Microbial Communities and Geochemical Constraining Mechanism of Antimony Mine Waste-Adapted Plants in Southwestern China

Antimony (Sb) and arsenic (As) are two hazardous metalloid elements, and the biogeochemical cycle of Sb and As can be better understood by studying plant rhizosphere microorganisms associated with Sb mine waste. In the current study, samples of three types of mine waste—Sb mine tailing, waste rocks, and smelting slag—and associated rhizosphere microorganisms of adapted plants were collected from Qinglong Sb mine, southwest China. 16S rRNA was sequenced and used to study the composition of the mine waste microbial community. The most abundant phylum in all samples was Proteobacteria, followed by Bacteroidota, Acidobacteriota, and Actinobacteriota. The community composition varied among different mine waste types. Gammaproteobacteria was the most abundant microorganism in tailings, Actinobacteria was mainly distributed in waste rock, and Saccharimonadia, Acidobacteriae, and Ktedonobacteria were mainly present in slag. At the family level, the vast majority of Hydrogenophilaceae were found in tailings, Ktedonobacteraceae, Chthoniobacteraceae, and Acidobacteriaceae (Subgroup 1) were mostly found in slag, and Pseudomonadaceae and Micrococcaceae were mainly found in waste rock. Actinobacteriota and Arthrobacter are important taxa for reducing heavy metal(loid) mobility, vegetation restoration, and self-sustaining ecosystem construction on antimony mine waste. The high concentrations of Sb and As reduce microbial diversity.

Microbial community structures and their driving factors in a typical gathering area of antimony mining and smelting in South China

This study investigated soil microbial community in a typical gathering area of antimony mining and smelting in South China. The physical and chemical properties of different soils (mining waste dumps, flotation tailings, and smelting slag) and depths (0-20 cm, 40-60 cm, and 80-100 cm) were compared. The results showed that antimony (Sb) and arsenic (As) were the main pollutants, and their concentrations were 5524.7 mg/kg and 3433.7 mg/kg, respectively. Xanthates were found in the flotation tailings and smelting slag, and the highest concentration was 585.1 mg/kg. The microbial communities were analyzed by high-throughput sequencing, and it was shown that Proteobacteria, Acidobacteria, Chlorobacterium, Bacteroides, and Actinomycetes were the dominant taxa at the phylum level. There were obvious differences in microbial community structure in different sites. The dominant microorganism in the mining site was Chujaibacter. Subgroup_2_unclassified and Gemmatimonadaceae_unclassified were the prevalent microorganisms in the flotation and smelting sites, respectively. As, Sb, and xanthates were the main factors affecting the diversity and composition of bacteria in the flotation tailings and smelting slag areas. Therefore, this study provides experimental guidance and a theoretical basis for soil antimony pollution quality assessment, biological treatment, and environmental remediation.

Dose–Response Effect of Nitrogen on Microbial Community during Hydrocarbon Biodegradation in Simplified Model System

Knowledge about the influence of C:N ratio on the biodegradation process of hydrocarbon compounds is of significant importance in the development of biostimulation techniques. The purpose of this study was to assess the impact of nitrogen compounds on the environmental consortium during the process of biological decomposition of hydrocarbons. The experimental variants represented low, moderate, and excessive biostimulation with nitrogen compounds. The metabolic activity of the consortium was tested using the flow cytometry technique. The efficiency of the biodegradation of hydrocarbons of the consortium, based on the gas chromatography method, and metapopulation changes, based on the analysis of V4 16srRNA sequencing data, were assessed. The results of the research confirm the positive effect of properly optimized biostimulation with nitrogen compounds on the biological decomposition of polycyclic aromatic hydrocarbons. The negative impact of excessive biostimulation on the biodegradation efficiency and metabolic activity of microorganisms is also proven. Low resistance to changes in the supply of nitrogen compounds is demonstrated among the orders Xanthomonadales, Burkholderiales, Sphingomonadales, Flavobacteriales, and Sphingobacteriales. It is proven that quantitative analysis of the order of Rhizobiales, characterized by a high-predicted potential for the decomposition of polycyclic aromatic hydrocarbons, may be helpful during biostimulation optimization processes in areas with a high nitrogen deficiency.

Relevance of the microbial community to Sb and As biogeochemical cycling in natural wetlands

Mining activities lead to elevated levels of antimony (Sb) and arsenic (As) in river systems, having adverse effects on the aquatic environment and human health. Microbes inhabiting river sediment can mediate the transformation of Sb and As, thus changing the toxicity and mobility of Sb and As. Compared to river sediments, natural wetlands could introduce distinct geochemical conditions, leading to the formation of different sedimentary microbial compositions between river sediments and wetland sediments. However, whether such changes in microbial composition could influence the microbially mediated geochemical behavior of Sb or As remains poorly understood. In this study, we collected samples from a river contaminated by Sb tailings and a downstream natural wetland to study the influence of microorganisms on the geochemical behavior of Sb and As after the Sb/As-contaminated river entered the natural wetland. We found that the microbial compositions in the natural wetland soil differed from those in the river sediment. The Sb/As contaminant components (Sb(III), As(III), As(V), As_exe) and nutrients (TC) were important determinants of the difference in the compositions of the microbial communities in the two environments. Taxonomic groups were differentially enriched between the river sediment and wetland soil. For example, the taxonomic groups Xanthomonadales, Clostridiales and Desulfuromonadales were important in the wetland and were likely to involve in Sb/As reduction, sulfate reduction and Fe(III) reduction, whereas Burkholderiales, Desulfobacterales, Hydrogenophilales and Rhodocyclales were important taxonomic groups in the river sediments and were reported to involve in Sb/As oxidation and sulfide oxidation. Our results suggest that microorganisms in both river sediments and natural wetlands can affect the geochemical behavior of Sb/As, but the mechanisms of action are different.