Generalist taxa shape fungal community structure in cropping ecosystems

Fungi regulate nutrient cycling, decomposition, symbiosis, and pathogenicity in cropland soils. However, the relative importance of generalist and specialist taxa in structuring soil fungal community remains largely unresolved. We hypothesized that generalist fungi, which are adaptable to various environmental conditions, could potentially dominate the community and become the basis for fungal coexisting networks in cropping systems. In this study, we identified the generalist and habitat specialist fungi in cropland soils across a 2,200 kms environmental gradient, including three bioclimatic regions (subtropical, warm temperate, and temperate). A few fungal taxa in our database were classified as generalist taxa (~1%). These generalists accounted for >35% of the relative abundance of all fungal populations, and most of them are Ascomycota and potentially pathotrophic. Compared to the specialist taxa (5–17% of all phylotypes in three regions), generalists had a higher degree of connectivity and were often identified as hub within the network. Structural equation modeling provided further evidence that after accounting for spatial and climatic/ edaphic factors, generalists had larger contributions to the fungal coexistence pattern than habitat specialists. Taken together, our study provided evidence that generalist taxa are crucial components for fungal community structure. The knowledge of generalists can provide important implication for understanding the ecological preference of fungal groups in cropland systems

Microbial regulation of the soil carbon cycle: evidence from gene-enzyme relationships.

A lack of empirical evidence for the microbial regulation of ecosystem processes, including carbon (C) degradation, hinders our ability to develop a framework to directly incorporate the genetic composition of microbial communities in the enzyme-driven Earth system models. Herein we evaluated the linkage between microbial functional genes and extracellular enzyme activity in soil samples collected across three geographical regions of Australia. We found a strong relationship between different functional genes and their corresponding enzyme activities. This relationship was maintained after considering microbial community structure, total C and soil pH using structural equation modelling. Results showed that the variations in the activity of enzymes involved in C degradation were predicted by the functional gene abundance of the soil microbial community (R2>0.90 in all cases). Our findings provide a strong framework for improved predictions on soil C dynamics that could be achieved by adopting a gene-centric approach incorporating the abundance of functional genes into process models

Harnessing microbiome‐based biotechnologies for sustainable mitigation of nitrous oxide emissions

Achieving the Sustainable Development Goal of climate change mitigation within this century will require adoption of new innovative technologies to control emissions of nitrous oxide (N2O), an important greenhouse gas leading to global warming. This is particularly important in the face of growing fertilizer consumption and continuous land degradation. Currently used tools to mitigate N2O emissions are based on agrochemical inputs and agronomic practices. Emerging technologies include plant breeding approaches to manipulate microbiome activities in agro-ecosystems, and microbial biotechnology approaches for in situ microbiome manipulation and engineering via use of biochemical, cellular and genome-editing methods. This article assessed the likely contribution of microbial biotechnology to the mitigation of N2O emissions and discussed how to facilitate the development of environmental-friendly microbiome-based biotechnology for sustainable climate change mitigation

Harnessing microbiome-based biotechnologies for sustainable mitigation of nitrous oxide emissions

Achieving the Sustainable Development Goal of climate change mitigation within this century will require adoption of new innovative technologies to control emissions of nitrous oxide (N2O), an important greenhouse gas leading to global warming. This is particularly important in the face of growing fertilizer consumption and continuous land degradation. Currently used tools to mitigate N2O emissions are based on agrochemical inputs and agronomic practices. Emerging technologies include plant breeding approaches to manipulate microbiome activities in agro-ecosystems, and microbial biotechnology approaches for in situ microbiome manipulation and engineering via use of biochemical, cellular and genome-editing methods. This article assessed the likely contribution of microbial biotechnology to the mitigation of N2O emissions and discussed how to facilitate the development of environmental-friendly microbiome-based biotechnology for sustainable climate change mitigation

Study on transport phenomena and performance of proton exchange membrane fuel cell with radial flow fields

The radial flow field structure, which has the advantages of low pressure drop, good water removal and good mass transfer, is an emerging structure for proton exchange membrane fuel cell (PEMFC) flow fields. However, optimization work on the design the structure is scarce for a complex structure that is difficult to manufacture. A comprehensive three-dimensional, non-isothermal and single-phase mathematical model is developed to describe the flow and heat, mass and charge transfer processes in a PEMFC. The transport phenomena and cell performance of radial flow fields with different gradient channels and parallel flow fields are studied and compared using the commercial computational fluid dynamics (CFD) software Fluent®. The distribution of oxygen concentration, pressure drop and temperature with different radial lengths is obtained. The effects of gradient channels, gas supply modes and radial lengths on cell performance are investigated. The results show that radial flow fields could offer more uniform oxygen distributions and lower pressure drops compared with parallel flow fields. Larger gradient channel sizes contribute to larger transfer volumes and higher gas molar concentrations in the catalyst layers and lower pressures in channels. The counter-flow supply mode is superior to the co-flow supply mode because it can enable a higher oxygen velocity and hence a higher current density

Silicon dioxide nanoparticles have contrasting effects on the temporal dynamics of sulfonamide and β-lactam resistance genes in soils amended with antibiotics

Nanoparticles (NPs) and antibiotic resistant genes (ARGs), as emerging environmental contaminants, have been reported to be accumulated in the soil environment. The use of NPs have raised increasing concerns about their environmental impacts, but the combined effect of NPs and antibiotics on ARGs remains less understood. Here, we established laboratory microcosms to explore the impacts of different concentrations of SiO _2 NPs on β -lactam and sulfonamide resistance genes in soils amended with β -lactam or sulfonamide. Illumina sequencing and quantitative PCR revealed that the addition of NPs increased the bacterial community diversity but had no significant effects on the bacterial abundance. Moreover, NPs and sulfonamide jointly increased the abundances of sulfonamide resistance genes, while the exposure of NPs and β -lactam decreased β -lactam resistance genes. The detected ARGs were associated closely with two mobile genetic elements (MGEs, the tnp A and int I1 genes), indicating that MGEs may contribute to the dissemination of ARGs. Correlation analysis indicated the shifts in potential bacterial hosts and the frequency of horizontal gene transfer were important factors explaining the patterns of ARGs. Furthermore, structural equation models indicated that NPs exposure decreased the abundances of β -lactam resistance genes by driving changes in bacterial community and MGEs, whereas the increased abundances of sulfonamide resistance genes were mainly associated with the bacterial community, diversity and MGEs mediated by NPs and antibiotics. These results suggested that the combined effects of NPs and antibiotics on soil bacterial resistance were different due to the types of antibiotics