Studies are limited on microbial-driven sulfurous species reduction coupled with anaerobic ammonium oxidation (Sammox) in a water environment. In this study, thiosulfate-driven Sammox bacteria from Ningbo Critical Zone Observatory (CZO) groundwater, Zhejiang Province, China were enriched and analyzed. The results showed that all three groundwater samples contained bacteria with sulfur reduction, sulfide oxidation-dependent denitrification, and nitrogen fixation abilities. At the genus level, Arcobacter, Flavobacterium, Hydrogenophaga, Gemmobacter, Pseudomonas, and Methylophilus have higher abundance in three samples. Proteobacteria accounted for a large proportion at the phylum level in all groundwater samples, and are often found in the sulfate reduction coupled with the ammonium oxidation process. Sammox can be performed by synergistic action of bacteria, which may convert ammonium to nitrite and thiosulfate to sulfide. Arcobacter was the dominant bacteria in the medium to remove nitrite and thiosulfate/sulfide. Sammox may also be performed by a single bacterium, belonging to Planctomycetes, Verrucomicrobia, and Chlamydiae superphylum. Overall, bacterial-mediated Sammox exists in the environment of CZO groundwater.
The use of microorganisms in geochemical gold recycling was considered recently. To explore the feasibility of gold biomineralization in this study, bacteria GX-3 were isolated from a heavy metal contaminated paddy soil in Guangxi province, China. This sulfur-reducing bacteria, Delftia tsuruhatensis, can survive in toxic Au3+ solution. Alkaline conditions (pH 8.0) and 35 °C were optimal for GX-3 cultivation. Nanoparticle formation was promoted by the coexistence of Fe3+. Field-emission scanning electron microscopy and transmission electron microscopy (TEM) images of GX-3 showed the presence of spherical particles, ranging from 50 to 100 and 200 to 500 nm in diameter, respectively, that stuck together and distributed around the surface of the bacteria as well as outside the cell. These nanoparticles were identified as gold according to the TEM–energy dispersive X-ray spectroscopy analysis. Here, bacterial extracellular solute-binding protein and/or porin should account for the gold nanoparticle formation and the detoxification in aqueous system as it transports electrons to Au3+ for nanoparticle precipitation. The ubiquitous nature of bacteria in near-surface environments and the rapid precipitation of gold by the sulfur-reducing bacterium suggest that these bacteria could be responsible for the wide bioaccumulation of gold in natural systems.
Abstract Flooded paddy soils after rewetting dry soils accompanied by extensive nitrogen fertilizer input are important anthropogenic N 2 O emitters due to the denitrification process. Owing to multiple complex denitrifying N 2 O sources, however, the extent to which biotic (fungal or bacterial) and abiotic (chemical) denitrification contribute to total N 2 O emissions remains largely unquantified. Here we sampled across eight provinces where most of the flooded paddy soils were in China to explore microbial and abiotic denitrification potentials and decipher N 2 O dynamics. N 2 O isotopocules and site preference (δ 15 N SP ) analyses found that in most of the sampled paddy soils, fungi‐mediated denitrification was the largest N 2 O contributor (51%–63%); while bacterial and chemical denitrifications contributed 12%–31% and 12%–28% of N 2 O emissions, respectively. Further, using 15 N labeling, a significant spatial heterogeneity of denitrification performance was observed among these flooded paddy soils. As indicated by variance partitioning and regression analyses, this heterogeneity was mainly determined by soil properties (especially soil organic carbon and total nitrogen) rather than by denitrifying communities. Our findings provide insights into the establishment of predictive models of future N 2 O emission from global paddy soils considering both the biotic and abiotic contributions.
Resource-transfer connections among bacteria, fungi, and microbivorous nematodes play an integral role in the decomposition pathways of soil micro-foodweb. Exploring the response of soil bacteria, fungi, and nematodes to grassland degradation is crucial for predicting the direction and trajectory of degradation. However, the knowledge about soil bacteria-fungi-nematode interactions in ecosystem function and nutrient cycling must be highlighted properly, especially in the Qinghai-Tibet Plateau. Therefore, this study focuses on four alpine meadows at different degenerate gradients (non-degraded grassland, slightly degraded grassland, moderately degraded grassland, and severely degraded grassland) on the Qinghai-Tibet Plateau. The investigation of soil bacteria-fungi-nematode interactions uses high-throughput sequencing and correlation network analysis. The results demonstrate significant variations in the composition of soil nematode genera, and bacterial and fungal phyla, across different degradation stages. Moreover, the diversity of nematodes, bacteria and fungi declined as grassland degradation worsened. Principal component analysis (PCA) revealed that alpine meadows with varying degradation gradients significantly influenced the community structure of bacteria, fungi, and nematodes. Mantel analysis indicated that soil water content (P < 0.05), total phosphorus (P < 0.05), and total nitrogen (P < 0.05) were the primary soil properties affecting the soil bacterial community. Similarly, available soil potassium (P < 0.05), microbial biomass carbon (P < 0.05), and microbial biomass nitrogen (P < 0.05) were the main soil factors influencing the soil fungal community. In contrast, the correlation between individual soil characteristics and soil nematodes did not reach a significant level, suggesting that a blend of physical and chemical properties regulates the soil nematode community. As grassland degradation intensified, the number of links in the interaction network of bacteria, fungi, and nematodes increased. Particularly, the networks between fungi and nematodes expanded, and the key species within each network varied with the different stages of grassland degradation. Concurrently, soil micro-foodweb decomposition pathways shifted. In the ND treatment, bacteria and fungi jointly dominated the degradation channels of the soil micro-food web, while the LD and MD treatments mainly dominated the degradation channels of fungi. On the other hand, SD treatment was dominated by bacterial degradation channels. This research adds to our theoretical understanding of meadow soil micro-foodwebs and the sustainable use of alpine grasslands in the Qinghai-Tibet Plateau.
This study investigates the impact of long-term warming on the carbon dynamics of forest ecosystems. This dataset is not available for commercial use. Please inform and acknowledge in case of any modifications or citations.
Urban wetland parks are an important practice for urban wetland protection and utilization due to the vast ecosystem service value. As emerging contaminants, antibiotic resistance genes (ARGs) are great attractions for environmental research and public concerns. Based on high-throughput qPCR and high-throughput amplicon sequencing techniques, we investigated the occurrence, abundance, and distribution profiles of antibiotic resistance genes in the aquatic environment of Xiamen urban wetland parks (five sites). The influencing factors and driving mechanisms of antibiotic resistance genes were deciphered on the basis of microbial community structure and water quality. Diverse and abundant ARGs were observed and coexisted in urban wet parks. A total of 217 ARGs were detected in the water body of urban wetland parks, with an abundance up to 6.48×10
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