Co-occurrence network of microbial communities affected by application of anaerobic fermentation residues during phytoremediation of ionic rare earth tailings area.

The long-term exploitation of ionic rare earth elements (REEs) in southern China has produced a large-scale of abandoned tailings area. While the application of anaerobic fermentation residues to cultivate economically valuable remediation plants (e.g. energy plant) has become a hotspot due to their merits in low-cost and sustainability in recent years, the succession and co-occurrence patterns of these microbial communities remain unclear. In this study, soil samples were collected from the sustainable restoration area, natural restoration area and tailings area. The composition and diversity of bacterial and fungal communities on five soil samples were evaluated using high-throughput sequencing technology. The results shown that the phytoremediation with anaerobic fermentation residues could significantly improve the physicochemical properties (especially for soil nutrients) and microbial diversity of soil within 3 years, while these parameters in natural restoration area were lower. The nonmetric multidimensional scaling (NMDS) ordinations revealed the shifts of microbial communities depending on soil physicochemical properties and plant species, and soil nutrients were the main factors affecting the microbial variation explained by the variation partition analysis (VPA). The soil nutrient accumulation obviously changed the proportion of oligotrophic and copiotrophic groups, among which the copiotrophic groups were significantly increased, such as Proteobacteria, Bacteroidetes, Gemmatimonadetes and Glomeromycota. The microbial co-occurrence network analysis indicated that application of anaerobic fermentation residues could significantly improve the topological properties and the stability of microbial network. The copiotrophic groups (e.g. Proteobacteria, Ascomycota) became the key to assemble stable network structure. Moreover, herbaceous plants could increase the proportion of fungi (e.g. Ascomycota) in microbial network, which improved the topological properties with bacteria synergistically. Therefore, the soil environment of REEs tailings area was effectively optimized by anaerobic fermentation residues and herbaceous plants, which furthered understanding of co-occurrence pattern and mutualistic relationships of microbial communities during sustainable restoration.

Thirty-year changes of the coastlines, wetlands, and ecosystem services in the Asia major deltas.

Coastal zones are usually composed of coastlines and coastal wetlands and are among the most productive and dynamic ecosystems. However, the deltas are seldom detected and compared in detail at the continental scale to investigate the spatiotemporal evolution of coastline migration and coastal wetlands. Here we detected and compared the spatiotemporal changes in coastlines, wetlands, and ecosystem services in major deltas in Asia, including the Yellow River Delta (YRD), Yangtze River Delta (YAD), Pearl River Delta (PRD), Red River Delta (RRD), Mekong River Delta (MERD), Chao Phraya River Delta (CPRD), Mahanadi River Delta (MARD), Krishna River Delta (KRD), and Indus River Delta (IRD). We used time series remote sensing images from 1990 to 2019 to derive coastline and wetland information for the nine coastal zones. The ecosystem service value coefficients were applied to explore the ecosystem services characteristics of wetland changes in coastal areas. We found that the coastlines of the deltas in the study area changed less in the bedrock and sandy coasts, while the coastlines in the silty delta coasts changed more from 1990 to 2019. The interannual dynamics of coastal wetland areas in nine major deltas over the nearly 30 years can be divided into three periods: decreasing variability (1990-2005), increasing variability (2005-2015), and increasing volatility (2015-2019). Ecosystem services had an overall downward trend. These findings complement the official database of coastal planning and have substantial guiding implications for adjusting coastal management regulation policies.

Pollution characteristics of livestock faeces and the key driver of the spread of antibiotic resistance genes.

The increasing prevalence of antibiotic resistance genes (ARGs) in livestock and poultry faeces has attracted considerable amounts of attention. However, in the actual breeding environment, the key driver of the spread of ARGs and which bacteria are involved remain unclear. This study investigated 19 antibiotics and 4 heavy metals in 147 animal faeces. The results showed that piglet faeces exhibited the highest levels of antibiotics and heavy metals. Twelve ARGs, 4 mobile genetic elements (MGEs) and bacterial communities of piglet faeces from 6 pig farms were further assessed to determine the key driver and relevant mechanism of the spread of ARGs. Sulphonamides (SAs) explained 36.5% of the variance (P < 0.05) of the bacterial community and were significantly related to 8 genes (P < 0.01), indicating that SAs dominated the spread of ARGs and should be tightly supervised. Structural equation modelling (SEM) indicated that SAs increased the abundance of ARGs via two pathways: horizontal transfer of ARGs (involving 10 genera) and vertical transfer of ARGs (involving 26 genera). These results improve our understanding of the potential hosts involved in the spread of ARGs, suggesting that monitoring of the above potential hosts is also important in animal feeding practice.

Differences of methanogenesis between mesophilic and thermophilic in situ biogas-upgrading systems by hydrogen addition.

To investigate the differences in microbial community structure between mesophilic and thermophilic in situ biogas-upgrading systems by H2 addition, two reactors (35 °C and 55 °C) were run for four stages according to different H2 addition rates (H2/CO2 of 0:1, 1:1, and 4:1) and mixing mode (intermittent and continuous). 16S rRNA gene-sequencing technology was applied to analyze microbial community structure. The results showed that the temperature is a crucial factor in impacting succession of microbial community structure and the H2 utilization pathway. For mesophilic digestion, most of added H2 was consumed indirectly by the combination of homoacetogens and strict aceticlastic methanogens. In the thermophilic system, most of added H2 may be used for microbial cell growth, and part of H2 was utilized directly by strict hydrogenotrophic methanogens and facultative aceticlastic methanogens. Continuous stirring was harmful to the stabilization of mesophilic system, but not to the thermophilic one.