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Rice paddy soil-associated microbiota participate in biogeochemical processes that underpin rice yield and soil sustainability, yet continental-scale biogeographic patterns of paddy soil microbiota remain elusive. The soil bacteria of four typical Chinese rice-growing regions were characterized and compared to those of nonpaddy soils. The paddy soil bacteria were significantly less diverse, with unique taxonomic and functional composition, and harbored distinct cooccurrence network topology. Both stochastic and deterministic processes shaped soil bacteria assembly, but paddy samples exhibited a stronger deterministic signature than nonpaddy samples. Compared to other environmental factors, climatic factors such as mean monthly precipitation and mean annual temperature described most of the variance in soil bacterial community structure. Cooccurrence network analysis suggests that the continental biogeographic variance in bacterial community structure was described by the competition between two mutually exclusive bacterial modules in the community. Keystone taxa identified in network models (Anaerolineales, Ignavibacteriae, and Deltaproteobacteria) were more sensitive to changes in environmental factors, leading us to conclude that environmental factors may influence paddy soil bacterial communities via these keystone taxa. Characterizing the uniqueness of bacterial community patterns in paddy soil (compared to nonpaddy soils) at continental scales is central to improving crop productivity and resilience and to sustaining agricultural soils. IMPORTANCE Rice fields provide food for over half of the world's human population. The ecology of paddy soil microbiomes is shaped by human activities, which can have a profound impact on rice yield, greenhouse gas emissions, and soil health. Investigations of the soil bacteria in four typical Chinese rice-growing regions showed that (i) soil bacterial communities maintain highly modularized species-to-species network structures; (ii) community patterns were shaped by the balance of integrated stochastic and deterministic processes, in which homogenizing selection and dispersal limitation dominate; and (iii) deterministic processes and climatic and edaphic factors influence community patterns mainly by their impact on highly connected nodes (i.e., keystone taxa) in networks. Characterizing the unique ecology of bacterial community patterns in paddy soil at a continental scale may lead to improved crop productivity and resilience, as well as sustaining agricultural soils.

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BackgroundPaddy soil dissolved organic matter (DOM) represents a major hotspot for soil biogeochemistry, yet we know little about its chemodiversity let alone the microbial community that shapes it. Here, we leveraged ultrahigh-resolution mass spectrometry, amplicon, and metagenomic sequencing to characterize the molecular distribution of DOM and the taxonomic and functional microbial diversity in paddy soils across China. We hypothesized that variances in microbial community significantly associate with changes in soil DOM molecular composition.ResultsWe report that both microbial and DOM profiles revealed geographic patterns that were associated with variation in mean monthly precipitation, mean annual temperature, and pH. DOM molecular diversity was significantly correlated with microbial taxonomic diversity. An increase in DOM molecules categorized as peptides, carbohydrates, and unsaturated aliphatics, and a decrease in those belonging to polyphenolics and polycyclic aromatics, significantly correlated with proportional changes in some of the microbial taxa, such as Syntrophobacterales, Thermoleophilia, Geobacter, Spirochaeta, Gaiella, and Defluviicoccus. DOM composition was also associated with the relative abundances of the microbial metabolic pathways, such as anaerobic carbon fixation, glycolysis, lignolysis, fermentation, and methanogenesis.ConclusionsOur study demonstrates the continental-scale distribution of DOM is significantly correlated with the taxonomic profile and metabolic potential of the rice paddy microbiome. Abiotic factors that have a distinct effect on community structure can also influence the chemodiversity of DOM and vice versa. Deciphering these associations and the underlying mechanisms can precipitate understanding of the complex ecology of paddy soils, as well as help assess the effects of human activities on biogeochemistry and greenhouse gas emissions in paddy soils.

In order to understand the pyrolysis and explosion characteristics of typical wood fiber dusts, the pyrolysis process, kinetic parameters, and pyrolysis gas types of the two dusts were calculated and analyzed using thermogravimetric-infrared coupler with redwood fiber dust and poplar fiber dust as the research objects. The results showed that the pyrolysis rate of mahogany dust was higher than that of poplar dust, and the activation energy was lower. The thermal weight loss of the two dusts was mainly reflected in the thermal decomposition at low temperature and combustion reaction at high temperature, and the pyrolysis products were mainly CO2, CO, H2O and a small amount of alkanes, alcohols, aldehydes, ketones and carboxylic acids, and the combustion products were mainly CO2 and CO, and the amount of CO2 of combustion products of mahogany fiber was higher than that of poplar fiber, while the pyrolytic combustion process of poplar fiber is relatively complex, with a high degree of incomplete combustion. The dust cloud minimum ignition temperature and maximum explosion pressure of the two wood fiber dusts were tested. Redwood fiber dust was more dangerous than poplar, and the mechanism was explained from the thermogravimetric-infrared test results. The results of this study could provide some data reference for the development of relevant policies and measures at sites involving such dusts. [ABSTRACT FROM AUTHOR]

Neuron is the basic unit of nervous system. Studying the fine morphology of neurons is crucial for understanding the structure of neural network and the manner of neural information processing. At present, effective methods to visualize fine morphology of neurons with specific cell types and specific projection are still lacking. In this paper, a recombination vesicular stomatitis virus (VSV) was designed, with nucleoprotein gene mutated and glycoprotein gene deleted. The virus, VSV-△G-NR7A-EGFP, was capable of highlighted morphology of the labelled neurons in a short time. With specific transgenic animals and a helper virus rAAV-EF1α-Dio-Bfp-Tva, it was demonstrated that, a further constructed virus VSV-△G-EnvA-NR7A-EGFP could sparsely and specifically label D2R neurons with nucleus accumbens-lateral hypothalamus (NAc-LH) projection and dopamine neurons with ventral tegmental area (VTA)-NAc projection.

Quantitative analyses of molecular expression, cell counts and neural network connections among different brain regions are essential in brain science research. Based on Paxinos and Franklin's the Mouse Brain in Stereotaxic Coordinates (Ⅱ) and public image processing software such as Photoshop and ImageJ, we developed a convenient method for semi-automatic segmentation and cell counting on brain sections. A standard template for brain region segmentation was first obtained from the Paxinos and Franklin's mouse brain atlas. Photoshop was then used to transform the standard template semi-automatically into the space of brain sections, yielding masks of segmented brain regions. Finally, ImageJ was used to analyze the data in different brain regions. This method is useful for immunohistochemical and neuron distribution pattern analyses, as well as neural network labelling studies. The method does not require expensive commercial image analysis software, and is also easy to implement and use.

Domestic biodegradable wastes (DBW) pose a threat to environmental quality and human health. Bioconversion via black soldier fly larvae (BSFL; Hermitia illucens L.) is an expedient way for converting 'waste to resource' (insect protein and biofertilizer). Although researches abounded in laboratory-reared experiments and bioconversion mechanisms were pertinent, the void of data from actual and full-scale operation restricts the intensification of BSFL technology and its global adoption. Hence, a full-scale BSFL bioconversion system lasting 4 years in Hangzhou (China) was investigated, and the feasibility and efficiency of 15 tonnes of DBW per day were studied. Through continuous technical optimization, the average production of fresh larvae was increased from 8.5% in 2017 to 15.3% in 2020, along with bioconversion rate of final vermicompost decreased from 35.4% to 14.5%. The total biomass reduction rate in 2020 was 68.7 ± 17.4 kg/(m3 d), equivalent to 0.735 ± 0.215 kg/(kg d) in the form of fresh larvae. Crude fat in fresh larvae accounted for 13.4%, and crude protein accounted for 16.2% in which the determined amino acid profile bore a strong resemblance to fish meal only except histidine and tyrosine. Its economic benefits proved the feasibility of this technology, and the profit reached up to 35.9 US$ per tonne of DBW in 2019. In conclusion, BSFL bioconversion system under current 'insect-farm' operation was a promising solution for DBW treatment with value-added waste recycling. [ABSTRACT FROM AUTHOR]