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The progress of plasmon-based technologies relies on an understanding of the properties of the enhanced electromagnetic fields generated by the coupling nanostrucutres1–6. Plasmon-enhanced applications include advanced spectroscopies7–10, optomechanics11, optomagnetics12 and biosensing13–17. However, precise determination of plasmon field intensity distribution within a nanogap remains challenging. Here, we demonstrate a molecular ruler made from a set of viologen-based, self-assembly monolayers with which we precisely measures field distribution within a plasmon nanocavity with ~2-Å spatial resolution. We observed an unusually large plasmon field intensity inhomogeneity that we attribute to the formation of a plasmonic comb in the nanocavity. As a consequence, we posit that the generally adopted continuous media approximation for molecular monolayers should be used carefully., QC 20201117

Subtropically grown bananas have different interactions with Fusarium oxysporum f. sp. cubense (Foc), causal agent of Fusarium wilt of banana (FWB), when compared with those grown in the tropics. The designation ‘subtropical’ race 4 (SR4) was assigned to Foc strains able to infect Cavendish (AAA) cultivars in the subtropics, but not in the tropics. ‘Tropical’ race 4 (TR4) gained prominence with the appearance and spread of a Foc strain that severely affects Cavendish bananas in both the tropics and subtropics. Recent surveys in Asia revealed TR4 as the predominant strain both in the tropics and subtropics, affecting not only Cavendish, but also many other cultivars. In many subtropical banana zones, Foc races 1 and 2, which complete the racial structure of Foc, are also found and cause severe losses in certain market-preferred dessert bananas. Environmental constraints increase the susceptibility of Cavendish bananas to SR4. However, the role of abiotic stresses in cultivar susceptibility to Foc needs to be better understood. It is not clear why some Foc strains only affect Cavendish in the subtropics, and what other factors, including pathogen virulence and microbial functional diversity, might be driving disease epidemics. Field experience suggests that optimum soil and water management strategies can reduce disease intensity, but targeted studies are needed to understand the virulence of different strains, the impact of fluctuating temperatures, soil pH, organic matter breakdown and soil microbial dynamics. Research findings on the epidemiology and management of FWB in Australia, Brazil, China, India and South Africa are discussed to propose priority areas for the development of improved disease management practices. © 2020 International Society for Horticultural Science. All rights reserved.

We lack empirical evidence for the relative importance of microbial functional attributes vs taxonomic attributes in regulating specified soil processes related to carbon (C) and nitrogen (N) cycling, which has hindered our ability to predict the responses of ecosystem multifunctionality to environmental changes. Here, we collected soil samples from a long-term experimental field with eight inorganic and organic fertilization treatments and evaluated the linkage between microbial functional attributes (abundance of functional genes), taxonomic attributes (microbial taxonomic composition), and soil processes including soil respiration, denitrification and nitrification. Long-term fertilization had no significant effect on the bacterial or fungal alpha-diversity. The treatments of chicken manure and sewage sludge addition significantly altered the rates of soil respiration, denitrification and nitrification, which were significantly correlated with the abundances of relevant functional genes. Random forest model indicated that the abundance of functional genes was the main diver for the rate of soil processes. The predominant effect of microbial functional attributes in driving soil processes was maintained when simultaneously accounting for multiple abiotic (total C, total N and soil pH) and biotic drivers (bacterial and fungal community structure), indicating that microbial functional attributes were the predominant driver predicting the rate of soil respiration, denitrification and nitrification. Our results suggested the importance of developing a functional gene-centric framework to incorporate microbial communities into biogeochemical models, which may provide new insights into the biodiversity-functions relationship and have implications for future management of the consequences of biodiversity loss for ecosystem multifunctionality.

Background: Termites are ubiquitous insects in tropical and subtropical habitats, where they construct massive mounds from soil, their saliva and excreta. Termite mounds harbor an enormous amount of microbial inhabitants, which regulate multiple ecosystem functions such as mitigating methane emissions and increasing ecosystem resistance to climate change. However, we lack a mechanistic understanding about the role of termite mounds in modulating the microbial community assembly processes, which are essential to unravel the biological interactions of soil fauna and microorganisms, the major components of soil food webs. We conducted a large-scale survey across a > 1500 km transect in northern Australia to investigate biogeographical patterns of bacterial and fungal community in 134 termite mounds and the relative importance of deterministic versus stochastic processes in microbial community assembly. Results: Microbial alpha (number of phylotypes) and beta (changes in bacterial and fungal community composition) significantly differed between termite mounds and surrounding soils. Microbial communities in termite mounds exhibited a significant distance-decay pattern, and fungal communities had a stronger distance-decay relationship (slope = -1.91) than bacteria (slope = -0.21). Based on the neutral community model (fitness < 0.7) and normalized stochasticity ratio index (NST) with a value below the 50% boundary point, deterministic selection, rather than stochastic forces, predominated the microbial community assembly in termite mounds. Deterministic processes exhibited significantly weaker impacts on bacteria (NST = 45.23%) than on fungi (NST = 33.72%), probably due to the wider habitat niche breadth and higher potential migration rate of bacteria. The abundance of antibiotic resistance genes (ARGs) was negatively correlated with bacterial/fungal biomass ratios, indicating that ARG content might be an important biotic factor that drove the biogeographic pattern of mic