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This study examined structural priming during online second language (L2) comprehension. In two self-paced reading experiments, 64 intermediate to advanced Chinese learners of English as a foreign language read coordinated noun phrases where the conjuncts had either the same structure or different structures. Experiment 1 showed that the second conjunct was read faster when it had the same structure as the first. This effect occurred for the structurally marked adjective phrases (e.g., a simple to grasp problem) but only showed a numerical trend for the less marked relative clauses (e.g., a problem that was simple to grasp). Experiment 2 compared unmarked adjective phrases and relative clauses (e.g., a simple problem vs. a problem that was simple) and found significant priming for both. Together, the two experiments showed that L2 comprehension priming could occur without repetition of the lexical head. Moreover, this priming was susceptible to inverse frequency effects, with the less frequent structure exhibiting greater priming. [ABSTRACT FROM AUTHOR]

This paper focuses on the generation and transformation of defects associated with subsurface damages (SSDs) in seed crystals during the physical vapor transport (PVT) growth of 4H-SiC crystals. SSDs in the 4H-SiC seed crystal were first revealed and labeled through photo-chemical etching. After 30 min of PVT growth on the 4H-SiC seed crystal, we found that ridge-like substances with a height ranging from 0.2 to 1.5 μm were formed in the region above the SSDs in the 4H-SiC seed crystal. Raman spectra analysis indicated that these ridge-like substances were 4H-SiC under tensile strain. We then continued the PVT growth to obtain a 4H-SiC boule and carried out a wafering process to obtain 4H-SiC single-crystal wafers. For the bottom wafer, above the 4H-SiC seed wafer, the full width at a half maximum (FWHM) of the rocking curves of the region above the SSDs of the seed wafer was higher than that in the other regions, indicating that the SSDs degrade the crystalline quality of 4H-SiC single crystal. The average value of the FWHM of the rocking curves of the top wafer became lower than that of the bottom wafer, indicating that the effect of SSDs gradually recovers. Molten-KOH etching indicated that SSDs in the 4H-SiC seed crystal give rise to the formation of low-angular grain boundaries (LAGBs) that consist of a wall of threading edge dislocations (TEDs) in 4H-SiC single crystals. [ABSTRACT FROM AUTHOR]

Long‐term mowing can cause morphological stuntedness of plants, thus reducing grassland productivity and exacerbating grassland degradation. Although plant microbiomes can enhance plant resistance against disturbance, considerable uncertainty exists regarding how mowing and mowing‐induced plant trait plasticity affect plant microbiomes in natural grasslands.Here we examined the responses of leaf/root‐associated bacterial (LAB/RAB) communities of 11 dominant herbaceous perennials (six replicates per species) to a 17‐year mowing treatment in a temperate grassland. We also measured leaf/root physiological and morphological traits, and analysed the relationships among mowing practice, bacterial community structures and leaf/root trait parameters.We found that both leaf and root functional traits showed interspecific variations (variations across different plant species), while only the leaf traits exhibited intraspecific variation (treatment‐induced variations within plant species) between the treatments. Similarly, the LAB community structure was more sensitive to mowing but less influenced by host species identity, compared to the RAB community. The RAB community structure was primarily shaped by host species identity, while mowing was a secondary influencing factor.The different patterns of LAB and RAB communities in response to mowing could be specifically explained by the inter/intraspecific variations of the related leaf and root traits. The LAB community was strongly correlated with the leaf traits which exhibited mowing‐induced plasticity (intraspecific variation), with the correlations with nitrogen resorption efficiency and above‐ground dry weight being the greatest. The root traits were important indicators of bacterial community structure in the root compartment across the hosts, rather than between the treatments. Root tissue density showed the strongest interspecific variation, and was identified as an overwhelming driver of the RAB community. The shifts in LAB/RAB communities under mowing were largely attributed to the increased proportions of Actinobacteria. The high mowing sensitivity of the LAB community was associated with the enrichment of soil‐derived Actinobacteria in leaves under mowing. Actinobacteria were also the main keystone taxa in the bacterial community networks under mowing.Our results demonstrate that the magnitude of plant‐associated microbial community response to long‐term mowing is plant compartment and trait variation dependent, and advance our understanding of the leaf/root microbiome‐trait relationships in complex plant communities. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

His serum K SP + sp was 4.4 mmol/l and Mg SP 2+ sp was 1.3 mmol/l. Intravenous amiodarone therapy was initiated, and after 72 h of drug exposure (total dose of 4.5 g amiodarone), sinus rhythm was successfully restored. Learning points for clinicians Macroscopic T-wave alternans (TWA) signifies significant vulnerability during repolarization and may be a harbinger of impending electrical instability. Introduction This case study presents the electrocardiographic (ECG) findings of a 70-year-old male with chronic heart failure caused by atrial fibrillation, who developed macrovolt T-wave alternans (TWA) and subsequent malignant arrhythmia after amiodarone treatment. [Extracted from the article]

Tardigrades, also known as 'water bear' or 'moss piglet', inhabit diverse environments ranging from marine to freshwater and terrestrial habitats. They occupy various trophic levels in the micro-food web attributed to their different feeding preferences and different predators, which also heralds the complexity of their ecological functions. Therefore, understanding the ecological preference of tardigrades and their interactions with other organisms is crucial for uncovering the changes in ecosystem functions performed by these organisms under future scenarios of climate change. Here, we investigated the diversity and community composition of tardigrades, and their driving factors from 194 soil samples across south and eastern Australia, based on amplicon sequencing of 18S rRNA gene. We further validated the presence or absence of tardigrades in selected soil samples using morphological detection. Eleven tardigrade genera were observed in 53 samples, predominantly from coastal soils, with Eremobiotus as the most dominant genus. Notably, mean annual temperature (MAT) was the most important factor influencing the presence of tardigrades, revealing a decreased relative abundance of tardigrades as MAT increased. Other abiotic factors, including soil pH, total nitrogen, and mean annual precipitation, as well as biotic factors, including bacteria, fungi, protists, algae and nematodes, were also critical to the distribution of tardigrades, as revealed by structural equation modelling. Morphological identification broadly aligned with our molecular findings; it also illustrated the sporadic distribution pattern of tardigrades. Taken together, our findings provide the first empirical evidence for the relationships between soil tardigrades and the environmental factors using environmental DNA and demonstrated the importance of both biotic and abiotic factors in shaping the large-scale distribution patterns of soil tardigrades. Additionally, our findings imply a certain degree of feasibility for soil tardigrade researches using environmental DNA, and highlight the potential risk of a decline in tardigrade communities in the face of increasing global temperatures. • Soil tardigrades were more prevalent in coastal areas rather than inland. • Temperature is an important factor influencing the presence or absence of soil tardigrades. • Lower temperature is more favourable for soil tardigrade existence. • Multiple biotic and abiotic factors affect the tardigrade community composition. • Morphological detection of tardigrade broadly aligned with molecular detection. [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhizal (AM) fungi and soil invertebrates represent a large proportion of total soil biomass and biodiversity and are vital for plant performance, soil structure, and biogeochemical cycling. However, the role of soil invertebrates in AM fungi development remains elusive. In this opinion article, we summarize the ecological importance of AM fungi and soil invertebrates in the plant–soil continuum and highlight the effects of soil invertebrates on AM fungal hyphae development and functioning. In a context of global change, we envision that better mechanistic understanding of the complex feedback via chemical signaling pathways across the interactions between soil invertebrates and AM fungi is critical to predict their ecological consequences and will open new avenues for promoting ecosystem resilience and sustainability. Arbuscular mycorrhizal fungi and soil invertebrates play critical roles in maintaining ecosystem primary productivity, nutrient cycling, soil health, and climate regulation. Soil invertebrates may affect the development of arbuscular mycorrhizal fungi through both direct (consumption, incidental damage, and dispersal vectors) and indirect effects (volatile organic compounds and nonvolatile secondary metabolites). Global environmental changes such as warming, drought, land use change, and microplastic pollution may affect the diversity and function of arbuscular mycorrhizal fungi and soil invertebrates. Unravelling the complex interactions between plants and soil biota will allow harnessing the potential of arbuscular mycorrhizal symbioses to improve plant resilience to biotic and abiotic stresses and to increase ecosystem sustainability in the changing environment. [ABSTRACT FROM AUTHOR]

Wuzi Yanzong Pill (WYP) was found to play a protective role on nerve cells and neurological diseases, however the molecular mechanism is unclear. To understand the molecular mechanisms that underly the neuroprotective effect of WYP on dopaminergic neurons in Parkinson's disease (PD). PD mouse model was induced by the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Gait and hanging tests were used to assess motor behavioral function. Immunofluorescence assay was used to determine TH-positive neurons in substantia nigra (SN). Apoptosis, dopamine and neurotrophic factors as well as expression of PI3K/Akt pathway were detected by TUNEL staining, ELISA and western blotting, respectively. First, it was observed that WYP intervention improved abnormal motor function in MPTP-induced PD model, alleviated the loss of TH+ neurons in SN, and increased dopamine content in brain, revealing a potential protective effect. Second, network pharmacology was used to analyze the possible targets and pathways of WYP action in the treatment of PD. A total of 126 active components related to PD were screened in WYP, and the related core targets included ALB, GAPDH, Akt1, TP53, IL6 and TNF. Particularly, the effect of WYP on PD may be medicate through PI3K/Akt signaling pathway and apoptotic regulation. The WYP treated PD mice had higher expression of p-PI3K, p-Akt and Bcl-2 but lower expression of Bax and cleaved caspase-3 than the non-WYP treated PD mice. Secretion of brain-derived neurotrophic factor (BDNF) and cerebral dopamine neurotrophic factor (CDNF) were also increased in the treated mice. WYP may inhibit apoptosis and increase the secretion of neurotrophic factor via activating PI3K/ Akt signaling pathway, thus protecting the loss of dopamine neurons in MPTP-induced PD mice. Highlights: Network pharmacology approach combined with experimental verification to clarify the mechanism. Wuzi Yanzong Pill ameliorated MPTP-induced PD mice by activating PI3K/Akt signaling pathway. Wuzi Yanzong Pill inhibited apoptosis of dopaminergic neurons in MPTP-induced PD mice. [ABSTRACT FROM AUTHOR]

To improve approaches for studying soil tardigrades, we compared three tardigrade extraction methods, including centrifugal flotation, Baermann funnel, and Whitehead tray, and found that the Whitehead tray method outperformed the two others. We optimised the Whitehead tray extraction condition under various soil pre-treatment processes, sample sizes, light exposure, and extraction time. We found that extending light exposure of non-sieved soils facilitates the extraction of tardigrades. We sequenced the DNA extracted from isolated tardigrade individuals and environmental soil samples, and found that tardigrade DNA extracts yielded a 173-fold increase in the proportion of tardigrade sequences and a 12-fold improvement in the estimation of tardigrade diversity. [Display omitted] • The Whitehead tray method outperformed centrifugal flotation and the Baermann funnel in soil tardigrade extraction. • Prolonged light exposure of non-sieved soils enhanced tardigrade extraction. • Tardigrade extractions improved tardigrade detection in samples where soil environmental DNA failed. • Extracting DNA from tardigrade individuals increased sequence recovery and diversity detection. [ABSTRACT FROM AUTHOR]

Summary: It is a grand challenge to ensure the food security for a predicted world population of exceeding 9.7 billion by 2050, especially in an era of global climate change, land degradation and biodiversity loss. Current agricultural productions are mainly relying on synthetic chemical fertilisers to boost plant productivity but have undesirable effects on the environment and soil biodiversity. A promising direction in sustainable agriculture is to harness naturally occurring processes of beneficial plant‐associated microbiomes to ensure sustained crop production and global food security. Despite the significant progress made in the development of beneficial microbes as inoculants to enhance plant performance, challenges remain with the translation of knowledge of plant and soil microbiomes to successful microbial products in the agricultural sector. Here, we highlight how fertilizer technology should be renovated by harnessing microbiome‐based innovations to promote plant productivity and contribute to the end of hunger. [ABSTRACT FROM AUTHOR]

Lithium tantalite (LiTaO 3 or LT) single crystal has been extensively applied in the fields of electro-optical and piezoelectric devices. As a typical anisotropic material, the crystallographic orientation effect on its machining responses, i.e., surface roughness and material removal rate (MRR), is not yet well understood. In the present work, we investigated the polishing responses of the three typical crystallographic orientations for LT single crystal under a series of rotation speeds. The results showed that both the rotation speed and crystalline orientation had little effect on the quality of polished surface. While for the MRR, it was almost linearly increased with increasing rotation speed for all of the three planes, among which the enhancements of MRR on Y-42° and Y-36° planes were more pronounced than that on X-112° plane. The scratch features and friction coefficients were investigated using a nanoindentation system under various velocities. The nano-hardness values were obtained under various strain rates and, hence, the strain rate sensitivities (SRS) were determined as 0.0172, 0.0455, and 0.043 for X-112°, Y-42°, and Y-36° planes, respectively. The better mechanical properties and "plastic" removal mechanism of X-112° plane resulted in the lower value of MRR. Also, the much lower SRS corresponded well with the relatively less sensitivity of MRR with rotation speed on X-112° plane. Results of this study suggested that the plastic parameter of SRS could provide as an excellent indicator to bridge the machining response and intrinsic deformation mechanism for brittle single crystal ceramics. [ABSTRACT FROM AUTHOR]

Summary: Understanding the current and future distributions of plant pathogens is critical to predict the plant performance and related economic benefits in the changing environment. Yet, little is known about the roles of environmental drivers in shaping the profiles of fungal plant pathogens in phyllosphere, an important habitat of microbiomes on Earth. Here, using a large‐scale investigation of Eucalyptus phyllospheric microbiomes in Australia and the multiple linear regression model, we show that precipitation is the most important predictor of fungal taxonomic diversity and abundance. The abundance of fungal plant pathogens in phyllosphere exhibited a positive linear relationship with precipitation. With this empirical dataset, we constructed current and future atlases of phyllosphere plant pathogens to estimate their spatial distributions under different climate change scenarios. Our atlases indicate that the abundance of fungal plant pathogens would increase especially in the coastal regions with up to 100‐fold increase compared with the current abundance. These findings advance our understanding of the distributions of fungal plant pathogens in phyllospheric microbiomes under the climate change, which can improve our ability to predict and mitigate their impacts on plant productivity and economic losses. [ABSTRACT FROM AUTHOR]

This article explores the relationship between tree species diversity and microbial carbon use efficiency (CUE) in forest ecosystems. The study conducted by Duan et al. in a subtropical forest in southwest China found that increasing tree species diversity led to an enhancement in microbial CUE. This improvement was attributed to a disproportionate increase in microbial growth rate compared to microbial respiration. The study also highlighted the role of microbial community structure, biomass, and extracellular enzyme activity in influencing microbial CUE. These findings emphasize the importance of maintaining high tree diversity for soil carbon sequestration and climate change mitigation. [Extracted from the article]

Summary: Termites are ubiquitous insects in tropical and subtropical habitats, and some of them construct massive nests ('mounds'), which substantially promote substrate heterogeneity by altering soil properties. Yet, the role of termite nesting process in regulating the distribution and diversity of soil microbial communities remains poorly understood, which introduces uncertainty in predictions of ecosystem functions of termite mounds in a changing environment. Here, by using amplicon sequencing, we conducted a survey of 134 termite mounds across >1500 km in northern Australia and found that termite mounds significantly differed from bulk soils in the microbial diversity and community compositions. Compared with bulk soils, termite nesting process decreased the microbial diversity and the relative abundance of rare taxa. Rare taxa had a narrower habitat niche breadth than dominant taxa and might be easier to be filtered by the potential intensive microbial competition during the nesting processes. We further demonstrated that the shift in pH induced by termite nesting process was a major driver shaping the microbial community profiles in termite mounds. Together, our work provides novel evidence that termite nesting is an important process in regulating soil microbial diversity, which advances our understanding of the functioning of termite mounds. [ABSTRACT FROM AUTHOR]

Cobalt‐catalyzed reductive carboxylation of aryl bromides with carbon dioxide has been developed. The reaction proceeded under one atm pressure of CO2 at 40 °C in the presence of cobalt iodide/2,2′‐bipyridine catalysts and zinc dust as a reducing reagent. Various aryl bromides could be converted to the corresponding carboxylic acids in good to high yields. Preliminary mechanistic experiments ruled out intervention of intermediate organozinc species for carboxylation with CO2, thus suggesting a direct CO2 insertion into the corresponding ArCoBr species. [ABSTRACT FROM AUTHOR]

Growing evidence suggests that livestock manure used as organic fertilizer in agriculture may lead to the potential propagation of antibiotic resistance genes (ARGs) from "farm to fork." However, little is known about the impacts of manure fertilization on the incidence of ARGs in the plant-associated microbiomes (including rhizosphere, endosphere, and phyllosphere), which hampers our ability to assess the dissemination of antibiotic resistance in the soil-plant system. Here, we constructed a pot experiment to explore the effects of poultry and cattle manure applications on the shifts in the resistome in the plant microbiome of harvested cherry radish. A total of 144 ARGs conferring resistance to eight major classes of antibiotics were detected among all the samples. Rhizosphere and phyllosphere microbiomes harbored significantly higher diversity and abundance of ARGs than did root endophytic microbiomes of cherry radish. Manure application significantly increased the abundance of ARGs in the rhizosphere and phyllosphere but not in the endophytes of the root, which is the edible part of cherry radish. Soil and plant microbiomes changed dramatically after manure applications and clustered separately according to different sample types and treatments. Structural equation modeling revealed that bacterial abundance was the most important factor modulating the distribution patterns of soil and plant resistomes after accounting for multiple drivers. Taken together, we provide evidence that enrichment of the resistome in the rhizosphere and phyllosphere of cherry radish is more obvious than with the endosphere after manure application, suggesting that manure amendment might not enhance the dissemination of ARGs into the root of vegetables in the pot experiment. [ABSTRACT FROM AUTHOR]

A titanocene‐catalyzed regioselective carbocarboxylation of dienes or alkenes has been developed. This reaction proceeds efficiently to form flexible and versatile carboxylic acids in the presence of nBuMgCl by the combined use of dienes or alkenes with organic halides and CO2 as the carbon synthon and carboxyl group, respectively. 2,3‐Disubstituted 1,3‐butadienes were used to afford acrylic acids in excellent yields with various organic halides. In the most cases, the arylalkenes afforded benzylic acids in high yields under similar conditions. The titanocene catalyst plays important roles in the generation of radicals and allyl‐ or benzyl‐magnesium halides. [ABSTRACT FROM AUTHOR]

Abstract Growing evidence points to the pivotal role of the environmental factors in influencing the transmission of antibiotic resistance genes (ARGs) and the propagation of resistant human pathogens. However, our understanding of the ecological and evolutionary environmental factors that contribute to development and dissemination of antibiotic resistance is lacking. Here, we profiled a wide variety of ARGs using the high-throughput quantitative PCR analysis in 61 soil samples collected from ocean and river beaches, which are hotspots for human activities and platforms for potential transmission of environmental ARGs to human pathogens. We identified the dominant abiotic and biotic factors influencing the diversity, abundance and composition of ARGs in these ecosystems. A total of 110 ARGs conferring resistance to eight major categories of antibiotics were detected. The core resistome was mainly affiliated into β-lactam and multidrug resistance, accounting for 66.9% of the total abundance of ARGs. The oprJ gene conferring resistance to multidrug was the most widespread ARG subtype detected in all the samples. The relative abundances of total ARGs and core resistome were significantly correlated with salinity-related properties including electrical conductivity and concentrations of sodium and chloride. Random forest analysis and structural equation modelling revealed that salinity was the most important factor modulating the distribution patterns of beach soil ARGs after accounting for multiple drivers. These findings suggest that beach soil is a rich reservoir of ARGs and that salinity is a predominant factor shaping the distribution patterns of soil resistome. Graphical abstract Unlabelled Image Highlights • Ocean and river beach soils are important reservoirs of antibiotic resistance genes (ARGs). • The oprJ gene is the most widespread ARG in beach soils. • Beach soils in different geographical locations shared extensive core resistome. • The abundance of ARGs had a significantly positive correlation with soil salinity properties. • Salinity is the most important factor modulating the distribution patterns of beach soil ARGs. [ABSTRACT FROM AUTHOR]

We report 2 self-paced reading experiments investigating the longevity of structural priming effects in comprehending reduced relative clauses among adult Chinese-speaking learners of English. Experiment 1 showed that structural priming occurred both when prime and target sentences were immediately adjacent and when they were separated by 1 or 2 filler sentences of unrelated structures. Moreover, the magnitude of the priming effect held constant across different lag conditions. Experiment 2 replicated the persistent priming effect and ruled out the possibility that the effect was due to verb repetition priming. Taken together, the current results suggest that recent experience with a given structure can have relatively long-lived facilitation effect on the language-processing system in second-language learners. As such, structural priming may serve as a learning mechanism for second-language speakers. [ABSTRACT FROM AUTHOR]

The recent discovery of comammox Nitrospira capable of converting ammonia to nitrate in a single organism radically challenged our century-long perception of the classic two-step nitrification performed by ammonia oxidizers and nitrite oxidizers. However, our understanding of the niche separation of comammox Nitrospira and canonical nitrifiers in forest ecosystems remains limited, especially under a global scenario of elevated nitrogen (N) deposition. Here we evaluated the impacts of six-year N deposition on the dynamics of comammox Nitrospira , ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) in a subtropical forest soil. Soil inorganic N concentrations significantly increased under the six-year simulation of N deposition, while soil pH, available phosphorus, total carbon (C), C/N ratio and microbial biomass significantly decreased. Quantitative PCR showed that the amoA gene abundances of comammox Nitrospira clade B and AOA substantially increased under the increasing rates of N deposition. By contrast, the AOB amoA gene abundance significantly decreased with the higher levels of N deposition (100 and 150 kg N ha−1 yr−1). Increased 13CO 2 incorporation into the AOA communities, rather than comammox Nitrospira or AOB, was demonstrated in a DNA-stable isotope probing microcosm, indicative of the capacity of AOA to assimilate 13CO 2 through autotrophic nitrification in the investigated subtropical forest soil under long-term N deposition. Phylogenetic analysis revealed that the autotrophic AOA assemblages belonged to the Nitrosotalea cluster, and their capacity for assimilating CO 2 through autotrophic nitrification was not affected by the long-term N deposition. Taken together, we provided new evidence for the niche separation of comammox Nitrospira and canonical ammonia oxidizers in soil nitrification under the long-term N deposition in the acidic subtropical forest soil. Highlights • The abundances of comammox Nitrospira clade B and AOA increased with N input. • The abundance of AOB decreased with N input rates higher than 100 kg N ha−1 yr−1. • Increased 13CO 2 was only incorporated into soil AOA through autotrophic pathway. • N input showed no effect on autotrophic AOA within the Nitrosotalea cluster. [ABSTRACT FROM AUTHOR]

Land application of animal manures is a major dissemination route for antibiotic resistance genes (ARGs) in agro-ecosystems, which are a potential risk to public health if they migrate into the food chain. Despite the fact that animal manure is a rich reservoir of ARGs our knowledge of the impacts of different types and amounts of animal manures on the temporal succession of a wide array of ARGs and potential ARG-hosts remains limited. Here, we constructed soil microcosms amended with two levels of swine, poultry or cattle manures to explore the time-course patterns of ARGs, mobile genetic elements (MGEs) including integrons and transposons, and bacterial communities. The high-throughput quantitative PCR detected 260 unique ARGs, and the application of all manure types, especially at the higher concentration (80 mg manure g−1 soil), significantly increased the diversity and abundances of ARGs and MGEs. The abundance of ARGs in manured soils declined over time, but was still higher than that in untreated soils after 120 days, indicating the persistence of ARGs in manured soils. The next-generation sequencing revealed a clear shift in the bacterial community compositions of manured soils during the incubation. Mantel test and network analysis revealed that the ARG profile was strongly correlated with the bacterial community compositions. Variation partitioning analysis, and structure equation models, further indicated that bacterial phylogeny played a primary role in shaping the ARG profiles in manured soils. However, the significant correlation between the abundances of MGEs and ARGs suggested that the potential effects of horizontal gene transfer on the persistence of ARGs should not be overlooked. In addition, soil properties, which were strongly affected by the added manures, could also affect the ARG patterns. These findings demonstrated the temporal patterns and dissemination risk of ARGs in manured soils, which might contribute to the development of effective strategies to minimise the spread of ARGs in agro-ecosystems. Graphical abstract Image 1 Highlights • Swine, poultry and cattle manures are a source of antibiotic resistance genes (ARGs). • Animal manure addition significantly increased the level of ARGs in soil microcosms. • Application of animal manures markedly changed the profile of the soil bacterial community. • ARG abundance declined with time, but ARGs persisted in the soil for at least 120 days. [ABSTRACT FROM AUTHOR]

• Crop diversity promoted soil microbial network complexity and multifunctionality. • Intermediate management intensities promoted soil microbial network complexity and multifunctionality. • Soil microbial network complexity had a stronger effect on multifunctionality than diversity. Although it is widely accepted that crop rotations can alleviate the adverse effects of agricultural intensification on ecosystem functioning, the influence of rotational diversification on soil microbial diversity, network complexity, and their associations with multifunctionality remains unclear. Here, we used a 16-year field experiment to assess the effect of six cropping regimes, and their respective crop diversity index (CDI, i.e., the number of crop species in a rotation multiplied by the species per year) and management intensity (MI, i.e., the anthropogenic inputs including fertilizer use, pesticide use and fuel consumption across a 2-year cycle), on soil microbial community (bacteria, fungi and protists) and soil multifunctionality. We used 20 soil functions related to soil properties, soil basal respiration, soil enzymatic activities and soil nitrogen cycling potential to characterize soil multifunctionality. Diversified crop rotation was shown to enhance soil multifunctionality. Also, soil multifunctionality and microbial diversity increased with CDI, but were negatively correlated or had a hump-shaped relationship with MI. With the increase in CDI, microbiome network nodes, edges and degree increased, but betweenness and average path length decreased. An increase in MI was found to have a hump-shaped relationship with the topological properties of the network. Soil microbiome network complexity had a stronger effect on multifunctionality than microbiome diversity and community composition. This study illustrates that more diverse rotations under intermediate MI promoted soil multifunctionality, and highlights the crucial role of network complexity in maintaining soil functions. [ABSTRACT FROM AUTHOR]

Summary: Antibiotic resistance is ancient and prevalent in natural ecosystems and evolved long before the utilization of synthetic antibiotics started, but factors influencing the large‐scale distribution patterns of natural antibiotic resistance genes (ARGs) remain largely unknown. Here, a large‐scale investigation over 4000 km was performed to profile soil ARGs, plant communities and bacterial communities from 300 quadrats across five forest biomes with minimal human impact. We detected diverse and abundant ARGs in forests, including over 160 genes conferring resistance to eight major categories of antibiotics. The diversity of ARGs was strongly and positively correlated with the diversity of bacteria, herbaceous plants and mobile genetic elements (MGEs). The ARG composition was strongly correlated with the taxonomic structure of bacteria and herbs. Consistent with this strong correlation, structural equation modelling demonstrated that the positive effects of bacterial and herb communities on ARG patterns were maintained even when simultaneously accounting for multiple drivers (climate, spatial predictors and edaphic factors). These findings suggest a paradigm that the interactions between aboveground and belowground communities shape the large‐scale distribution of soil resistomes, providing new knowledge for tackling the emerging environmental antibiotic resistance. [ABSTRACT FROM AUTHOR]

Prior work has shown intriguing differences between first language (L1) and second language (L2) comprehension priming of relative clauses. We investigated English reduced relative clause priming in Chinese adult learners of English. Participants of different education levels read sentences in a self-paced, moving window paradigm. Critical sentences had a temporarily ambiguous reduced relative clause. Across lists, critical sentences were rotated, so that they occurred either as prime or as target, and had either the same or different verb as the critical sentence with which they were paired. Prime/target pairs were separated by several filler sentences, which never contained a relative clause. Mean reading times for the disambiguating region in the target sentences were faster than in the prime sentences, but only in the same-verb condition, not in the differentverb condition. This pattern of results is consistent with L1 comprehension priming research, suggesting that similar lexically specific mechanisms are involved in L1 and L2 comprehension priming of reduced relative clauses. These findings are in line with lexicalist accounts of sentence comprehension (e.g. MacDonald et al., 1994), according to which syntactic information is bound to specific words. In addition, these findings argue against theories that postulate fundamental differences in processing of L1 and L2 (e.g. Clahsen and Felser, 2006a, 2006b). [ABSTRACT FROM AUTHOR]

Composting has been suggested as a potential strategy to eliminate antibiotic residues and pathogens in livestock manure before its application as an organic fertilizer in agro-ecosystems. However, the impacts of composting on antibiotic resistance genes (ARGs) in livestock manure and their temporal succession following the application of compost to land are not well understood. We examined how aerobic composting affected the resistome profiles of cattle manure, and by constructing laboratory microcosms we compared the effects of manure and compost application to agricultural soils on the temporal succession of a wide spectrum of ARGs. The high-throughput quantitative PCR array detected a total of 144 ARGs across all the soil, manure and compost samples, with Macrolide-Lincosamide-Streptogramin B, aminoglycoside, multidrug, tetracycline, and β-lactam resistance as the most dominant types. Composting significantly reduced the diversity and relative abundance of ARGs and mobile genetic elements (MGEs) in the cattle manure. In the 120-day microcosm incubation, the diversity and abundance of ARGs in manure-treated soils were significantly higher than those in compost-treated soils at the beginning of the experiment. The level of antibiotic resistance rapidly declined over time in all manure- and compost-treated soils, coupled with similar temporal patterns of manure- and compost-derived bacterial communities as revealed by SourceTracker analysis. The network analysis revealed more intensive interactions/associations among ARGs and MGEs in manure-treated soils than in compost-treated soils, suggesting that mobility potential of ARGs was lower in soils amended with compost. Our results provide evidence that aerobic composting of cattle manure may be an effective approach to mitigate the risk of antibiotic resistance propagation associated with land application of organic wastes. [ABSTRACT FROM AUTHOR]

A metastable state for the elongated Permalloy elements is found to exist within a short field range before magnetization reversal. From the micromagnetic simulation it exhibits a wavelike structure, and the corresponding magnetic pole density distribution shows a pattern with periodic spots along the boundary. We also use magnetic force microscopy imaging and magnetoresistance measurement, which measures the nucleation field and coercive field, to study the noncoherent magnetization reversal properties of Permalloy ellipse with long axis, short axis, and thicknesses of 18 μm, 1 μm, and 45 nm, respectively. The metastable state before switching is found to be repeatable. [ABSTRACT FROM AUTHOR]

Soil ecosystem represents the largest contributor to global nitrous oxide (N2O) production, which is regulated by a wide variety of microbial communities in multiple biological pathways. A mechanistic understanding of these N2O production biological pathways in complex soil environment is essential for improving model performance and developing innovative mitigation strategies. Here, combined approaches of the 15N-18O labelling technique, transcriptome analysis, and Illumina MiSeq sequencing were used to identify the relative contributions of four N2O pathways including nitrification, nitrifier-induced denitrification (nitrifier denitrification and nitrification-coupled denitrification) and heterotrophic denitrification in six soils (alkaline vs. acid soils). In alkaline soils, nitrification and nitrifier-induced denitrification were the dominant pathways of N2O production, and application of the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) significantly reduced the N2O production from these pathways; this is probably due to the observed reduction in the expression of the amoA gene in ammonia-oxidizing bacteria (AOB) in the DMPP-amended treatments. In acid soils, however, heterotrophic denitrification was the main source for N2O production, and was not impacted by the application of DMPP. Our results provide robust evidence that the nitrification inhibitor DMPP can inhibit the N2O production from nitrifier-induced denitrification, a potential significant source of N2O production in agricultural soils. [ABSTRACT FROM AUTHOR]

Globally, drylands represent the largest terrestrial biome and are projected to expand by 23% by the end of this century. Drylands are characterized by extremely low levels of water and nutrients and exhibit highly heterogeneous distribution in plants and biocrusts which make microbial processes shaping the dryland functioning rather unique compared with other terrestrial ecosystems. Nitrous oxide (N2O) is a powerful greenhouse gas with ozone depletion potential. Despite of the pivotal influences of microbial communities on the production and consumption of N2O, we have limited knowledge of the biological pathways and mechanisms underpinning N2O emissions from drylands, which are estimated to account for 30% of total gaseous nitrogen emissions on Earth. In this article, we describe the key microbial players and biological pathways regulating dryland N2O emissions, and discuss how these processes will respond to emerging global changes such as climate warming, extreme weather events and nitrogen deposition. We also provide a conceptual framework to precisely manipulate the dryland microbiome to mitigate N2O emissions in situ using emerging technologies with great specificity and efficacy. These cross-disciplinary efforts will enable the development of novel and environmental-friendly microbiome-based solutions to future mitigation strategies of climate change. [ABSTRACT FROM AUTHOR]

The size dependence of switching fields of permalloy rings is studied by micromagnetic simulations and by magnetoresistance measurements. Experimentally, the switching fields can be obtained from the discontinuities of the magnetoresistance curve. From the simulated hysteresis loops and the magnetoresistance curves obtained by experiment it is shown that the switching field from the vortex state to the reverse onion state increases considerably as decreasing of the lateral size or as increasing of the thickness. There is, however, no significant correlation between the ring size and the switching field from the onion state to the vortex state. [ABSTRACT FROM AUTHOR]

4H silicon carbide (4H-SiC) substrate wafers without surface / subsurface damages and low surface roughness are ideal substrates for the development of power electronics and radio frequency (RF) microwave devices, which hold great promise in applications of new energy, rail transportation, smart grid and 5G communication. The processing of 4H-SiC substrate wafers includes slicing, grinding, lapping, polishing and cleaning. However, the surface damages ( SDs) and subsurface damages (SSDs) introduced during the processing of 4H-SiC substrates affects the properties of 4H-SiC substrates and epitaxial layers, and thus the performance and reliability of devices based on 4H-SiC. This paper focuses on the formation and removal mechanisms of SDs / SSDs during the processing of 4H-SiC substrate wafers. Based on the detection method of SDs / SSDs, the morphologies and characterization approaches of SDs / SSDs are reviewed. Finally, three commonly used technologies for the removal SDs / SSDs, along with their technical advantages, development challenges and trends, are briefly discussed. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Land management practices considerably influence ecosystem processes and functioning, particularly in dryland ecosystems where nutrient and water limitations have direct (via effects on productivity) and indirect (via effects on soil biota) effects on ecosystem properties. Fungi in soils and associated with roots play critical roles in soil nutrient cycling and plant nutrient acquisition, but their responses to land management practices in dryland ecosystems remain equivocal. Here we evaluate the responses of fungal communities in roots and soils associated with a Eucalyptus saligna plantation after six years of forest management practices (irrigation and fertilisation) and in two different microenvironments within treated plots, in the presence and absence of understorey grasses. We observed that the richness and evenness of fungal communities were higher in soil than in root samples, but these two parameters did not vary among any of the management treatments. Effects of fertilisation and irrigation on fungal community composition were observed and appeared to be related to variation in soil pH, moisture, and nitrogen availability. Both fertilisation and irrigation decreased the ratios of ectomycorrhizal fungi to total fungi and increased the frequencies of saprotrophic and/or plant pathogenic fungi. We observed that some OTUs were shared between soil and root-associated fungal communities but that fertilisation was associated with lower frequencies of shared OTUs, suggesting a decoupling of these communities. In the absence of grasses, where only tree roots were present, we observed fewer tight relationships between fungal occurrence in root and soil samples. Our findings highlight the importance of forest management practices for fungal community assembly processes in dryland ecosystems, which may have consequences for the predictability of fungal community dynamics and nutrient cycling. [ABSTRACT FROM AUTHOR]

Bacterial resistance to antibiotics and heavy metals are frequently linked, suggesting that exposure to heavy metals might select for bacterial assemblages conferring resistance to antibiotics. However, there is a lack of clear evidence for the heavy metal-induced changes of antibiotic resistance in a long-term basis. Here, we used high-capacity quantitative PCR array to investigate the responses of a broad spectrum of antibiotic resistance genes (ARGs) to 4–5 year copper contamination (0–800 mg kg−1) in two contrasting agricultural soils. In total, 157 and 149 unique ARGs were detected in the red and fluvo-aquic soil, respectively, with multidrug and β-lactam as the most dominant ARG types. The highest diversity and abundance of ARGs were observed in medium copper concentrations (100–200 mg kg−1) of the red soil and in high copper concentrations (400–800 mg kg−1) of the fluvo-aquic soil. The abundances of total ARGs and several ARG types had significantly positive correlations with mobile genetic elements (MGEs), suggesting mobility potential of ARGs in copper-contaminated soils. Network analysis revealed significant co-occurrence patterns between ARGs and microbial taxa, indicating strong associations between ARGs and bacterial communities. Structural equation models showed that the significant impacts of copper contamination on ARG patterns were mainly driven by changes in bacterial community compositions and MGEs. Our results provide field-based evidence that long-term Cu contamination significantly changed the diversity, abundance and mobility potential of environmental antibiotic resistance, and caution the un-perceived risk of the ARG dissemination in heavy metal polluted environments. [ABSTRACT FROM AUTHOR]

The nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) is a powerful tool that can be used to promote nitrogen (N) use efficiency and reduce N losses from agricultural systems by slowing nitrification. Mounting evidence has confirmed the functional importance of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) in nitrification and N2O production; however, their responses to DMPP amendment and the microbial mechanisms underlying the variable efficiencies of DMPP across different soils remain largely unknown. Here we compared the impacts of DMPP on nitrification and the dynamics of ammonia oxidizers between an acidic pasture soil and an alkaline vegetable soil using a 15N tracing and 13CO2-DNA-stableisotope probing (SIP) technique. The results showed that DMPP significantly inhibited nitrification and N2O production in the vegetable soil only, and the transient inhibition was coupled with a significant decrease in AOB abundance. No significant effects on the community structure of ammonia oxidizers or the abundances of total bacteria and denitrifiers were observed in either soil. The 15N tracing experiment revealed that autotrophic nitrification was the predominant form of nitrification in both soils. The 13CO2-DNA-SIP results indicated the involvement of AOB in active nitrification in both soils, but DMPP inhibited the assimilation of 13CO2 into AOB only in the vegetable soil. Our findings provide evidence that DMPP could effectively inhibit nitrification through impeding the abundance and metabolic activity of AOB in the alkaline vegetable soil but not in the acidic pasture soil, possibly due to the low AOB abundance or the adsorption of DMPP by organic matter. [ABSTRACT FROM AUTHOR]

As a typical multi-functional single crystal material, lithium tantalate (LiTaO 3 or LT) exhibits its excellent electro-optical, piezoelectric properties and has now been widely applied into many applications, such as electro-optical modulators, pyroelectric detectors, optical waveguide, piezoelectric transducers and SAW (surface acoustic wave) substrates. LT is known as a very important functional material, however the details of its machinability are not readily available yet. The content in this study is firstly focuses on the physical properties of LT like piezoelectric and pyroelectric effects and their influence on grinding performance. The obtained results are analyzed and discussed to understand its physical properties which have significant influences on their machinability in the grinding process. The crack initiation is possible to be dominated by internal stress which originated from self-polarization of the material itself. Hence, in order to suppress the physical effects induced by polarization during grinding of LT, control the temperature of coolant and increase the electrical conductivity of coolant are purposely tried in this study. The grinding results suggest that control of coolant temperature and use of electrolyte solution can effectively suppress the increasing rate of grinding torque and surface roughness, which in turn enhance the performance of LT wafer grinding. The LT wafers are eventually able to be thinned less than 100 μm. [ABSTRACT FROM AUTHOR]

The emerging environmental spread of antibiotic-resistance genes (ARGs) and their subsequent acquisition by clinically relevant microorganisms is a major threat to public health. Animal manure has been recognized as an important reservoir of ARGs; however, the dissemination of manure-derived ARGs and the impacts of manure application on the soil resistome remain obscure. Here, we conducted a microcosm study to assess the temporal succession of total bacteria and a broad spectrum of ARGs in two contrasting soils following manure application from cattle that had not been treated with antibiotics. High-capacity quantitative PCR detected 52 unique ARGs across all the samples, with β-lactamase as the most dominant ARG type. Several genes of soil indigenous bacteria conferring resistance to β-lactam, which could not be detected in manure, were found to be highly enriched in manure-treated soils, and the level of enrichment was maintained over the entire course of 140 days. The enriched β-lactam resistance genes had significantly positive relationships with the relative abundance of the integrase intI1 gene, suggesting an increasing mobility potential in manure-treated soils. The changes in ARG patterns were accompanied by a significant effect of cattle manure on the total bacterial community compositions. Our study indicates that even in the absence of selective pressure imposed by agricultural use of antibiotics, manure application could still strongly impact the abundance, diversity and mobility potential of a broad spectrum of soil ARGs. Our findings are important for reliable prediction of ARG behaviors in soil environment and development of appropriate strategies to minimize their dissemination. [ABSTRACT FROM AUTHOR]

Global climate change is predicted to enhance atmospheric temperature and CO2, with important consequences on biogeochemical nitrogen cycling in dryland ecosystems, which are highly vulnerable and characterized by extremely low nutrient availability. Belowground nitrification processes, predominantly mediated by ammonia-oxidizing archaea (AOA) and bacteria (AOB), are central to plant nitrogen availability and soil N2O emissions, but their responses to future climatic scenarios in drylands remain largely unknown. Here we investigated the impact of factorial combinations of elevated CO2 (+200 ppm) and elevated temperature (+3 °C) on dynamics of ammonia oxidizers and nitrification in three dryland soils planted with Eucalyptus tereticornis. Soil properties (including total carbon, H2O%, and nitrate) and potential nitrification rates were strongly impacted by elevated temperature after nine months, accompanied by significantly higher AOA abundance in two soils and a gradual decrease in AOB abundance under elevated temperature. DNA-stable isotope probing showed increased assimilation of 13CO2 by AOA, but not AOB, under warming, indicating that AOA were actively growing and utilizing the 13CO2 substrates, which was coupled with significantly higher net nitrogen mineralization and nitrification rates. High-throughput microarray analysis revealed temperature selections of particular AOA assemblages and a significant reduction in diversity and co-occurrence of the metabolically active AOA phylotypes. Although these responses were soil specific, structural equation modelling by compiling all the data together showed that warming had significant direct and indirect impacts on soil nitrification which were driven by changes in AOA community structure, but no obvious effects of elevated CO2 could be identified. Our findings suggest that warming has stronger effects than elevated CO2 on autotrophic nitrification, and AOA are more responsive to elevated temperature than AOB in the tested dryland ecosystems. [ABSTRACT FROM AUTHOR]

[Display omitted] [ABSTRACT FROM AUTHOR]

Hydrogen‐oxidising bacteria play a key role in maintaining the composition of gases within the atmosphere and are ubiquitous in agricultural soils. While studies have shown that hydrogen accumulates in soil surrounding legume nodules and the soil surface, soils as a whole act as a net sink for hydrogen, raising questions about how hydrogen is internally recycled by soils. Can the energy derived from hydrogen oxidation be directly funnelled into plants to promote their growth or does it only act as a booster for other plant‐growth promoting bacteria? Moreover, while the fertilisation effect of hydrogen on plants has previously been shown to be beneficial, questions remain about the upper limit of hydrogen uptake by plants before it becomes detrimental. Agricultural practices such as fertilisation may impact the balance of hydrogen‐oxidisers and hydrogen‐producers in these ecosystems, potentially having detrimental effects on not only agricultural land but also global biogeochemical cycles. In this perspectives piece, we highlight the importance of understanding the contribution of hydrogen to agricultural soils and the effects of agricultural practices on the ability for bacteria to cycle hydrogen in agricultural soils. We propose a framework to gain better insights into microbial hydrogen cycling within agroecosystems, which could contribute to the development of new agricultural biotechnologies. [ABSTRACT FROM AUTHOR]

The continuous increase of the greenhouse gas nitrous oxide (N2O) in the atmosphere due to increasing anthropogenic nitrogen input in agriculture has become a global concern. In recent years, identification of the microbial assemblages responsible for soil N2O production has substantially advanced with the development of molecular technologies and the discoveries of novel functional guilds and new types of metabolism. However, few practical tools are available to effectively reduce in situ soil N2O flux. Combating the negative impacts of increasing N2O fluxes poses considerable challenges and will be ineffective without successfully incorporating microbially regulated N2O processes into ecosystem modeling and mitigation strategies. Here, we synthesize the latest knowledge of (i) the key microbial pathways regulating N2O production and consumption processes in terrestrial ecosystems and the critical environmental factors influencing their occurrence, and (ii) the relative contributions of major biological pathways to soil N2O emissions by analyzing available natural isotopic signatures of N2O and by using stable isotope enrichment and inhibition techniques. We argue that it is urgently necessary to incorporate microbial traits into biogeochemical ecosystem modeling in order to increase the estimation reliability of N2O emissions. We further propose a molecular methodology oriented framework from gene to ecosystem scales for more robust prediction and mitigation of future N2O emissions. [ABSTRACT FROM AUTHOR]

Terrestrial arid and semi-arid ecosystems (drylands) constitute about 41% of the Earth's land surface and are predicted to experience increasing fluctuations in water and nitrogen availability. Mounting evidence has confirmed the significant importance of ammonia-oxidizing archaea (AOA) and bacteria (AOB) in nitrification, plant nitrogen availability and atmospheric N2O emissions, but their responses to environmental perturbations in drylands remain largely unknown. Here we evaluate how the factorial combinations of irrigation and fertilization in forests and land-use change from grassland to forest affects the dynamics of AOA and AOB following a 6-year dryland field study. Potential nitrification rates and AOA and AOB abundances were significantly higher in the irrigated plots, accompanied by considerable changes in community compositions, but their responses to fertilization alone were not significant. DNA-stable isotope probing results showed increased 13CO2 incorporation into the amoA gene of AOA, but not of AOB, in plots receiving water addition, coupled with significantly higher net mineralization and nitrification rates. High-throughput microarray analysis revealed that active AOA assemblages belonging to Nitrosopumilus and Nitrosotalea were increasingly labelled by 13CO2 following irrigation. However, no obvious effects of land-use changes on nitrification rates or metabolic activity of AOA and AOB could be observed under dry conditions. We provide evidence that water addition had more important roles than nitrogen fertilization in influencing the autotrophic nitrification in dryland ecosystems, and AOA are increasingly involved in ammonia oxidation when dry soils become wetted. [ABSTRACT FROM AUTHOR]

A 4H-SiC single crystal is a substrate material for high-frequency and high-voltage power devices. Dislocation density is a fundamental criterion for evaluating the quality of 4H-SiC single crystals. 4H-SiC single crystals grown by the physical vapor transport (PVT) method generally have high dislocation density. To investigate the effect of nitrogen doping on dislocation proliferation in SiC crystals, the thermal field of the ingot during PVT growth was calculated by COMSOL Multiphysics, and thermal stress was calculated by thermal elastic theory. Finally, the dislocation density of the crystal was calculated based on the Alexander–Haasen model for inhomogeneous nitrogen doping. By comparing the calculation and experimental results, we proposed a possible value of the effective stress to evaluate the effect of a nitrogen dopant on dislocation density, which helps calculate the dislocation density in the n-type SiC. [ABSTRACT FROM AUTHOR]

Abstract: Acid soils, extensively used for nitrogen-fertilized agriculture and agroforestry, have important roles in maintaining global biogeochemical cycling and ecosystem functions. Huge inputs of nitrogen-based fertilizers into terrestrial ecosystems accelerate soil acidification, concomitantly altering the nitrogen transformation processes. Nitrification, as a critical component of the nitrogen cycle, is a microbially mediated process from ammonia to nitrate via nitrite, contributing to enormous losses of fertilizers through atmospheric emissions of greenhouse gas N2O and nitrate leaching to groundwater. However, the functionally dominant nitrifiers and underlying mechanisms for the acid soil nitrification are a long-standing mystery, which have confused scientists for more than 100 years. This century-long paradox originated from the early observations of active nitrification activity in acid soils, intensified by the failure of ammonia-oxidizing bacteria (AOB) cultures to sustain the nitrification in liquid batch under acid conditions, might be resolved by the recent progress in metagenomic, isotopic probing studies, and isolation of acidophilic ammonia-oxidizing archaea (AOA). Emerging evidence led to the supposition of the predominant role of AOA in controlling the autotrophic ammonia oxidation of acid soils, which has radically revised the previous perception that this oxidative reaction was exclusively regulated by autotrophic AOB and occasionally by heterotrophic nitrifiers. In this chapter, we review the recent progress in our understanding of the pH-impacted distribution of ammonia oxidizers, the niche differentiation of AOA and AOB shaped by acid stress, and the possible mechanisms of autotrophic nitrification in acid soils. The unveiling of this key process in widely distributed acid soils would help to identify effective biological strategies for better management of terrestrial nitrogen turnover and balance. [Copyright &y& Elsevier]

Based on a 6-year field trial in a temperate steppe in Inner Mongolia, we investigated the effects of nitrogen (N) and phosphorus (P) fertilization and mowing on the abundance and community compositions of ammonia-oxidizing Bacteria ( AOB) and Archaea ( AOA) upon early (May) and peak (August) plant growth using quantitative PCR (q PCR), terminal-restriction fragment length polymorphism ( T- RFLP), cloning and sequencing. The results showed that N fertilization changed AOB community composition and increased AOB abundance in both May and August, but significantly decreased AOA abundance in May. By contrast, P fertilization significantly influenced AOB abundance only in August. Mowing significantly decreased AOA abundance and had little effect on AOA community compositions in May, while significantly influencing AOB abundance in both May and August, Moreover, AOA and AOB community structures showed obvious seasonal variations between May and August. Phylogenetic analysis showed that all AOA sequences fell into the Nitrososphaera cluster, and the AOB community was dominated by Nitrosospira Cluster 3. The results suggest that fertilization and mowing play important roles in affecting the abundance and community compositions of AOA and AOB. [ABSTRACT FROM AUTHOR]

Abstract: Soil pollution by elevated heavy metals exhibits adverse effects on soil microorganisms. Ammonia oxidizing bacteria and ammonia oxidizing archaea perform ammonia oxidative processes in acidic soils. However, influence of heavy metal stress on soil ammonia oxidizers distribution and diversity is inadequately addressed. This study investigated the responses of ammonia oxidizing bacteria and archaea to heavy metals, Cu and As during short-term laboratory experiment. Two different acidic alfisols named as Rayka and Hangzhou spiked with different concentrations of As, Cu and As+Cu were incubated for 10 weeks. Significant reduction in copy numbers of archaeal-16S rRNA, bacterial-16S rRNA and functional amoA genes was observed along elevated heavy metal concentrations. Ammonia oxidizing archaea was found to be more abundant than ammonia oxidizing bacteria in all the heavy metal treatments. The potential nitrification rate significantly decreased with increasing As and Cu concentrations in the two soils examined. Denaturing gradient gel electrophoresis analysis revealed no apparent community shift for ammonia oxidizing archaea even at higher concentrations of As and Cu. Phylogenetic analysis of archaeal amoA gene from 4 clone libraries indicated that all the archaeal amoA sequences were placed within 3 distinct clusters from soil and sediment group 1.1b of Thaumarchaeota. Our results could be useful for the better understanding of the ecological effects of heavy metals on the abundance and diversity of soil ammonia oxidizers. [Copyright &y& Elsevier]

Terrestrial ecosystems are predicted to experience an increasing level of atmospheric nitrogen (N) deposition, which may cause significant shifts in plant community composition and concomitantly stimulate soil acidification. However, little is known concerning the effects of N deposition on belowground microbial communities in alpine grassland ecosystems such as on the Tibetan Plateau. This study examined the responses of soil N-transforming microbes (measured after DNA extraction and quantitative PCR), soil microbial biomass C (SMBC) and N (SMBN), and soil enzyme activities to different forms (NH-N, NO-N, and NHNO-N) and rates (1.5 and 7.5 g N m year, denoted as low and high N, respectively) of N fertilization (addition) in two successive plant growing seasons. The N rate, not N form, influenced the abundance of ammonia-oxidizing archaea (AOA). High N addition significantly increased ammonia-oxidizing bacteria (AOB) abundance which differed across different N form treatments. Nitrogen addition had no significant impact on the abundance of soil denitrifiers. The SMBC and SMBN were significantly decreased by high N additions, but no difference was found among different N forms. Despite higher urease activities being detected in the late plant growing season, the activities of invertase and alkaline phosphomonoesterase stayed unchanged irrespective of the different N amendments and plant growing season. Significant positive correlations were found between potential nitrification rates and AOB abundances. These results highlight that AOB seemed to respond more sensitively to different N fertilization and might have prominent roles in soil N cycling processes in this Tibetan Plateau alpine meadow than AOA. [ABSTRACT FROM AUTHOR]