Reuse of composted food waste from rural China as vermicomposting substrate: effects on earthworms, associated microorganisms, and economic benefits

ABSTRACTAerobic composting of food waste (FW) from rural China using a composting device results in a substantial financial burden on the government. This study aimed to assess the feasibility of mitigating this cost using vermicomposting of composted FW. The specific aims were to elucidate the effects of composted FW on earthworm growth and reproduction, reveal the changes in the physical and chemical properties of earthworm casts during vermicomposting, identify the microbial community structure associated with vermicomposting, and perform a financial analysis based on the yield of earthworms and earthworm casts. Mixing composted FW and mature cow dung in an equal ratio achieved the highest earthworm reproduction rate, where 100 adult earthworms produced 567 juvenile earthworms and 252 cocoons in 40 d. Earthworms reduce salt content of vermicomposting substrates by assimilating Na+ and promoting humification by transforming humin into humic and fulvic acid, thus producing earthworm casts with a high generation index > 80%. When composted FW was added to a vermicomposting substrate, a distinctive microbial community structure with alkaliphilic, halophilic, and lignocellulolytic microorganisms dominated the microflora. The dominant bacterial species was Saccharopolyspora rectivirgula, and the dominant fungal species changed from Kernia nitida to Coprinopsis scobicola. Furthermore, microbial genes for refractory organic matter and fat degradation were observed in Vibrio cholerae, Kernia nitida, and Coprinopsis scobicola. Financial analysis showed that vermicomposting has the potential to reduce the cost associated with FW disposal from $ 57 to $ 18/t.

High synthetic cost-amino acids reduce member interactions of acetate-degrading methanogenic microbial community

Introduction

The cooperation among members of microbial communities based on the exchange of public goods such as 20 protein amino acids (AAs) has attracted widespread attention. However, little is known about how AAs availability affects interactions among members of complex microbial communities and the structure and function of a community.

Methods

To investigate this question, trace amounts of AAs combinations with different synthetic costs (low-cost, medium-cost, high-cost, and all 20 AAs) were supplemented separately to acetate-degrading thermophilic methanogenic reactors, and the differences in microbial community structure and co-occurring networks of main members were compared to a control reactor without AA supplementation.

Results

The structure of the microbial community and the interaction of community members were influenced by AAs supplementation and the AAs with different synthetic costs had different impacts. The number of nodes, links, positive links, and the average degree of nodes in the co-occurrence network of the microbial communities with AAs supplementation was significantly lower than that of the control without AAs supplementation, especially for all 20 AAs supplementation followed by the medium- and high-cost AAs supplementation. The average proportion of positive interactions of microbial members in the systems supplemented with low-cost, medium-cost, high-cost, all AAs, and the control group were 0.42, 0.38, 0.15, 0.4, and 0.45, respectively. In addition, the ecological functions of community members possibly changed with the supplementation of different cost AAs.

Discussion

These findings highlight the effects of AAs availability on the interactions among members of complex microbial communities, as well as on community function.

Mixing with native broadleaf trees modified soil microbial communities of Cunninghamia lanceolata monocultures in South China

Mixing with different broadleaf trees into the monocultures of Cunninghamia lanceolata is widely adopted as an efficient transformation of the pure C. lanceolata forest. However, it is unclear how native broad-leaved trees influence the belowground ecological environment of the pure C. lanceolata culture plantation in nutrient-poor soil of South China. Herein, we aimed to investigate how a long-time mixing with native broadleaf trees shape soil microbial community of the pure C. lanceolata forest across different soil depth (0-20 cm and 20-40 cm) and to clarify relationships between the modified soil microbial community and those affected soil chemical properties. Using high-throughput sequencing technology, microbial compositions from the mixed C. lanceolata-broadleaf forest and the pure C. lanceolata forest were analyzed. Network analysis was utilized to investigate correlations among microorganisms, and network robustness was assessed by calculating network natural connectivity. Results demonstrated that the content of soil microbial biomass carbon and nitrogen, total phosphorus and pH in mixed forest stand were significantly higher than those in pure forest stand, except for available phosphorus in topsoil (0-20 cm). Simultaneously, the mixed C. lanceolata-broadleaf forest has a more homogeneous bacterial and fungal communities across different soil depth compared with the pure C. lanceolata forest, wherein the mixed forest recruited more diverse bacterial community in subsoil (20-40 cm) and reduced the diversity of fungal community in topsoil. Meanwhile, the mixed forest showed higher bacterial community stability while the pure forest showed higher fungal community stability. Moreover, bacterial communities showed significant correlations with various soil chemical indicators, whereas fungal communities exhibited correlations with only TP and pH. Therefore, the mixed C. lanceolata-broadleaf forest rely on their recruiting bacterial community to enhance and maintain the higher nutrient status of soil while the pure C. lanceolata forest rely on some specific fungi to satisfy their phosphorus requirement for survive strategy.

Insight into characteristics of sulphur-based autotrophic denitrifying microbiota in the nitrate removal

Mariculture wastewater is characterized by low organic carbon to nitrogen ratio (C/N) but high nitrate concentration, which makes it difficult to remove nitrate by the completely heterotrophic denitrification. However, high nitrate discharge poses a threat to the natural environment and human health. Thus, we enriched sulphur-based autotrophic denitrifying (SAD) microbiota and optimized the nitrate removal under different environmental factors and electron donor conditions. The results showed that the dominant genera in the enriched microbiota were previously confirmed autotrophic denitrifiers, Sulfurovum, Thioalkalispira-Sulfurivermis, and Sedimenticola, with a high relative abundance of 41.14%, 21.01%, and 6.17%. Among the environmental factors, pH was the key factor affecting SAD microbiota, and pH 7-9 favoured nitrate removal. However, high pH led to nitrite accumulation (e.g. 10 mg/L at pH = 9), which should be strictly avoided. With regard to electron donors, the optimal concentrations of thiosulphate and nitrate were 50 and 5 mg/L, respectively. The best organic carbon is acetate with an optimal concentration of 10 mg/L. Meanwhile, the initial concentration of thiosulphate was proportional to the nitrate removal rate, while higher concentrations of organic carbon stimulated the heterotrophic denitrification potential of microbiota and thus benefited to dentrification. This study showed that the enriched SAD microbiota was able to achieve efficient nitrate removal under suitable environmental conditions and mixed electron donors and thus presented the potential for application in the treatment of mariculture wastewater.

Structure of Benthic Microbial Communities in the Northeastern Part of the Barents Sea

The Barents Sea shelf is one of the most economically promising regions in the Arctic in terms of its resources and geographic location. However, benthic microbial communities of the northeastern Barents Sea are still barely studied. Here, we present a detailed systematic description of the structures of microbial communities located in the sediments and bottom water of the northeastern Barents Sea based on 16S rRNA profiling and a qPCR assessment of the total prokaryotic abundance in 177 samples. Beta- and alpha-diversity analyses revealed a clear difference between the microbial communities of diverse sediment layers and bottom-water fractions. We identified 101 microbial taxa whose representatives had statistically reliable distribution patterns between these ecotopes. Analysis of the correlation between microbial community structure and geological data yielded a number of important results-correlations were found between the abundance of individual microbial taxa and bottom relief, thickness of marine sediments, presence of hydrotrolite interlayers, and the values of pH and Eh. We also demonstrated that a relatively high abundance of prokaryotes in sediments can be caused by the proliferation of Deltaproteobacteria representatives, in particular, sulfate and iron reducers.

[Two-stage Inhibition Effects of Burkholderia sp. Y4 Application on Cadmium Uptake and Transport in Wheat]

In order to evaluate the feasibility of using Burkholderia sp. Y4 as a cadmium （Cd）-reducing bacterial agent in contaminated wheat fields， the changes in the rhizosphere soil microbial community and Cd available state， as well as the content and transport characteristics of Cd in the wheat root， basal node， internode， and grain under the treatment of strain Y4 were tested using microbial high-throughput sequencing， step-by-step extraction， subcellular distribution， and occurrence analyses. The results showed that root application of strain Y4 significantly reduced the root and grain Cd content of wheat by 7.7% and 30.3%， respectively， compared with that in the control treatment. The Cd content and Cd transfer factor results in wheat vegetative organs showed that strain Y4 reduced the Cd transfer factor from basal node to internode by 79.3%， and Cd content in the wheat internode stem also decreased by 50.9%. The study of Cd occurrence morphology showed that strain Y4 treatment increased the proportion of residual Cd in roots and basal ganglia， decreased the contents of inorganic and water-soluble Cd in roots， and increased the content of residual Cd in basal ganglia. Further examination of the subcellular distribution of Cd showed that the Cd content in root cell walls and basal ganglia cell fluid increased by 21.3% and 98.2%， respectively， indicating that the Cd fixation ability of root cell walls and basal ganglia cell fluid was improved by the strain Y4 treatment. In the rhizosphere soil， it was found that the microbial community structure was changed by strain Y4 application. Under the Y4 treatment， the relative abundance of Burkholderia increased from 9.6% to 11.5%， whereas that of Acidobacteriota decreased. Additionally， the relative abundance of Gemmatimonadales， Pseudomonadales， and Chitinophagales were also increased by strain Y4 treatment. At the same time， the application of strain Y4 increased the pH value of rhizosphere soil by 8.3%. The contents of exchangeable Cd， carbonate-bound Cd， and iron-manganese oxide-bound Cd in the soil decreased by 44.4%， 21.7%， and 15.9%， respectively， whereas the proportion of residual Cd reached 53.6%. Root application of strain Y4 increased the contents of nitrate nitrogen and ammonium nitrogen in the soil by 22.0% and 21.4%， respectively， and the contents of alkaline nitrogen also increased to a certain extent. In conclusion， the root application of strain Y4 not only improved soil nitrogen availability but also inhibited Cd transport and accumulation from contaminated soil to wheat grains in a "two-stage" manner by reducing Cd availability in rhizosphere soil and improving Cd interception and fixation capacity of wheat roots and basal nodes. Therefore， Burkholderia Y4 has application potential as a Cd-reducing and growth-promoting agent in wheat.

The response pattern of the microbial community structure and metabolic profile of jiupei to Bacillus subtilis JP1 addition during baijiu fermentation

BACKGROUND

Baijiu brewing is a complex and multifaceted multimicrobial co-fermentation process, in which various microorganisms interact to form an interdependent micro-ecosystem, subsequently influencing metabolic activities and compound production. Among these microorganisms, Bacillus, an important bacterial genus in the liquor brewing process, remains unclear in its role in shaping the brewing microbial community and its functional metabolism.

RESULTS

A baijiu fermentation system was constructed using B. subtilis JP1 isolated from native jiupei (grain mixture) combined with daqu (a saccharifying agent) and huangshui (a fermentation byproduct). Based on high-throughput amplicon sequencing analysis, it was evident that B. subtilis JP1 significantly influences bacterial microbial diversity and fungal community structure in baijiu fermentation. Of these, Aspergillus and Monascus emerge as the most markedly altered microbial genera in the jiupei community. Based on co-occurrence networks and bidirectional orthogonal partial least squares discriminant analysis models, it was demonstrated that the addition of B. subtilis JP1 intensified microbial interactions in jiupei fermentation, consequently enhancing the production of volatile flavor compounds such as heptanoic acid, butyl hexanoate and 3-methylthiopropanol in jiupei.

CONCLUSION

B. subtilis JP1 significantly alters the microbial community structure of jiupei, enhancing aroma formation during fermentation. These findings will contribute to a broader application in solid-state fermentation. © 2024 Society of Chemical Industry.

The influence of low-temperature resistant lactic acid bacteria on the enhancement of quality and the microbial community in winter Jerusalem Artichoke (Helianthus tuberosus L.) silage on the Qinghai-Tibet Plateau

Jerusalem Artichoke (Helianthus tuberosus L.), an emerging "food and fodder" economic crop on the Qinghai-Tibet Plateau. To tackle problems such as incomplete fermentation and nutrient loss occurring during the low-temperature ensilage of Jerusalem Artichokes in the plateau's winter, this study inoculated two strains of low-temperature resistant lactic acid bacteria, Lactobacillus plantarum (GN02) and Lactobacillus brevis (XN25), along with their mixed components, into Jerusalem Artichoke silage material. We investigated how low-temperature resistant lactic acid bacteria enhance the quality of low-temperature silage fermentation for Jerusalem Artichokes and clarify its mutual feedback effect with microorganisms. Results indicated that inoculating low-temperature resistant lactic acid bacteria significantly reduces the potential of hydrogen and water-soluble carbohydrates content of silage, while increasing lactic acid and acetic acid levels, reducing propionic acid, and preserving additional dry matter. Inoculating the L. plantarum group during fermentation lowers pH and propionic acid levels, increases lactic acid content, and maintains a dry matter content similar to the original material. Bacterial community diversity exhibited more pronounced changes than fungal diversity, with inoculation having a minor effect on fungal community diversity. Within the bacteria, Lactobacillus remains consistently abundant (>85%) in the inoculated L. plantarum group. At the fungal phylum and genus levels, no significant changes were observed following fermentation, and dominant fungal genera in all groups did not differ significantly from those in the raw material. L. plantarum exhibited a positive correlation with lactic acid and negative correlations with pH and propionic acid. In summary, the inoculation of L. plantarum GN02 facilitated the fermentation process, preserved an acidic silage environment, and ensured high fermentation quality; it is a suitable inoculant for low-temperature silage in the Qinghai-Tibet Plateau.

Impact of Anthropogenic Activities on Microbial Community Structure in Riverbed Sediments of East Kazakhstan

Heavy metal (HMe) pollution in regions with mining and metallurgy activities is known to be a serious environmental problem worldwide. Hydrological processes contribute to the dissemination of HMes (drainage, precipitation, flow rate). The aim of the present study is to investigate the microbial community structure in ten river sediments sampled in different regions of East Kazakhstan, which are contaminated with HMes. The overall degree of sediment contamination with HMes (Cr, Cu, Zn, Pb, and Cd) was assessed using the pollution index Zc, which ranged from 0.43 to 21.6, with the highest in Ridder City (Zc = 21.6) and Ust-Kamenogorsk City, 0.8 km below the dam of the hydroelectric power station (Zc = 19.6). The tested samples considerably differed in organic matter, total carbon, nitrogen, and phosphorus content, as well as in the abundance of HMe-related functional gene families and antibiotic resistance genes. Metagenomic analysis of benthic microorganisms showed the prevalence of Proteobacteria (88.84-97.61%) and Actinobacteria (1.21-5.98%) at the phylum level in all samples. At the class level, Actinobacteria (21.68-57.48%), Betaproteobacteria (19.38-41.17%), and Alphaproteobacteria (10.0-39.78%) were the most common among the classified reads. To the best of our knowledge, this is the first study on the metagenomic characteristics of benthic microbial communities exposed to chronic HMe pressure in different regions of East Kazakhstan.

Correlation of microbial community structure and volatile flavor compounds during corn yellow wine fermentation

High-throughput sequencing was used to define microbial community structure and GC-MS to identify volatile flavor substances during fermentation of corn yellow wine, and results were analyzed by multivariate statistical analysis. Seventeen bacterial phyla, 239 bacterial genera, 4 fungal phyla, and 18 fungal genera were found and changes in community structure occurred during fermentation. Twenty-four volatile flavor substances, including 14 esters and 5 alcohols, were detected and changes during fermentation recorded. Sixteen microbial genera correlated with volatile flavor substances and Weissella, Lactobacillus, Pseudomonas, Rhodotorul, and Kwoniella had significant correlation with ethyl esters and higher alcohols. Micro-organisms thus influence flavor development during corn yellow wine fermentation.

Shifts in soil ammonia-oxidizing community maintain the nitrogen stimulation of nitrification across climatic conditions

Anthropogenic nitrogen (N) loading alters soil ammonia-oxidizing archaea (AOA) and bacteria (AOB) abundances, likely leading to substantial changes in soil nitrification. However, the factors and mechanisms determining the responses of soil AOA:AOB and nitrification to N loading are still unclear, making it difficult to predict future changes in soil nitrification. Herein, we synthesize 68 field studies around the world to evaluate the impacts of N loading on soil ammonia oxidizers and nitrification. Across a wide range of biotic and abiotic factors, climate is the most important driver of the responses of AOA:AOB to N loading. Climate does not directly affect the N-stimulation of nitrification, but does so via climate-related shifts in AOA:AOB. Specifically, climate modulates the responses of AOA:AOB to N loading by affecting soil pH, N-availability and moisture. AOB play a dominant role in affecting nitrification in dry climates, while the impacts from AOA can exceed AOB in humid climates. Together, these results suggest that climate-related shifts in soil ammonia-oxidizing community maintain the N-stimulation of nitrification, highlighting the importance of microbial community composition in mediating the responses of the soil N cycle to N loading.

The impact of smash-ridge tillage on agronomic traits of tobacco plants, soil enzymatic activity, microbial community structure, and functional diversity

Smash-ridge tillage is a novel cultivation technique that significantly influences the quality of arable land and crop yield. In this study, we employed high-throughput 16S rRNA sequencing and Biolog-ECO methods to systematically investigate the impact of smash-ridge tillage on soil microbial community structure and functional diversity. The results demonstrate that both ST30 and ST50 treatments significantly enhance the average plant height, average plant diameter, average fresh root weight, stem fresh weight, and leaf area of tobacco plants, with the ST50 treatment exhibiting superior performance. Furthermore, both ST30 and ST50 treatments exhibit significantly higher soil enzyme activity and microbial community diversity compared to the CK treatment. They also improve the soil microbial utilization of carbon sources. Additionally, the ST50-treated soil samples demonstrate 15 microbial functional pathways that exceed those of the CK and ST30 treatments. In conclusion, the Smash-ridge tillage treatment at a depth of 50 cm yields more favorable results. This study provides a theoretical foundation for enhancing soil quality in Smash-ridge tillage by elucidating the mechanisms through which it impacts soil microbial ecology.

Role of plant metabolites in the formation of bacterial communities in the rhizosphere of Tetrastigma hemsleyanum

Tetrastigma hemsleyanum Diels et Gilg, commonly known as Sanyeqing (SYQ), is an important traditional Chinese medicine. The content of bioactive constituents varies in different cultivars of SYQ. In the plant growth related researches, rhizosphere microbiome has gained significant attention. However, the role of bacterial communities in the accumulation of metabolites in plants have not been investigated. Herein, the composition of bacterial communities in the rhizosphere soils and the metabolites profile of different SYQ cultivars' roots were analyzed. It was found that the composition of microbial communities varied in the rhizosphere soils of different SYQ cultivars. The high abundance of Actinomadura, Streptomyces and other bacteria was found to be associated with the metabolites profile of SYQ roots. The findings suggest that the upregulation of rutin and hesperetin may contribute to the high bioactive constituent in SYQ roots. These results provide better understanding of the metabolite accumulation pattern in SYQ, and also provide a solution for enhancing the quality of SYQ by application of suitable microbial consortia.

Biochar addition accelerates the humification process by affecting the microbial community during human excreta composting

Biochar addition plays an important role in manure composting, but its driving mechanism on microbial succession and humification process of human excreta composting is still unclear. In the present study, the mechanism of biochar addition was explored by analysing the humification process and microbial succession pattern of human excreta aerobic composting without and with 10% biochar (HF and BHF). Results indicated that BHF improved composting temperature, advanced the thermophilic phase by 1 d, increased the germination index by 49.03%, promoted the growth rate of humic acid content by 17.46%, and raised the compost product with the ratio of humic acid to fulvic acid (HA/FA) by 16.19%. Biochar regulated the diversity of fungi and bacteria, increasing the relative abundance of Planifilum, Meyerozyma and Melanocarpus in the thermophilic phase, and Saccharomonospora, Flavobacterium, Thermomyces and Remersonia in the mature phase, which accelerates the humification. Bacterial communities' succession had an obvious correlation with the total carbon, total nitrogen, and temperature (P < 0.05), while the succession of fungal communities was influenced by the HA/FA and pH (P < 0.05). This study could provide a reference for the improvement of on-site human excreta harmless by extending the thermophilic phase, and facilitating the humification in human excreta compost with biochar addition.

Diversity and correlation analysis of different root exudates on the regulation of microbial structure and function in soil planted with Panax notoginseng

Introduction

Specific interactions between root exudates and soil microorganisms has been proposed as one of the reasons accounting for the continuous cropping obstacle (CCO) of Panax notoginseng. However, rotation of other crops on soils planted with P. notoginseng (SPP) did not show CCO, suggesting that root exudates of different crops differentially regulate soil microorganisms in SPP.

Methods

Here, we investigated the microbial community structure and specific interaction mechanisms of the root exudates of the four plant species, P. notoginseng (Pn), Zea mays (Zm), Nicotiana tabacum (Nt) and Perilla frutescens (Pf), in SPP by static soil culture experiment.

Results

The results showed that the chemical diversity of root exudates varied significantly among the four plant species. Pn had the highest number of unique root exudates, followed by Nt, Zm and Pf. Terpenoids, flavonoids, alkaloids and phenolic acids were the most abundant differentially accumulated metabolites (DAMs) in Pn, Nt, Zm and Pf, respectively. However, lipids were the most abundant common DAMs among Zm Nt and Pf. Pn root exudates decreased the relative abundance of bacteria, but increased that of fungi. While specific DAMs in Pn enriched Phenylobacterium_zucineum, Sphingobium_yanoikuyae, Ophiostoma_ulmi and functional pathways of Nucleotide excision repair, Streptomycin biosynthesis, Cell cycle-Caulobacter and Glycolysis/Gluconeogenesis, it inhibited Paraburkholderia _caledonica and Ralstonia_pickettii. However, common DAMs in Zm, Nt and Pf had opposite effects. Moreover, common DAMs in Zm, Nt and Pf enriched Ralstonia_pseudosolanacearum and functional pathway of Xylene degradation; unique DAMs in Zm enriched Talaromyces_purcureogeneus, while inhibiting Fusarium_tricinctum and functional pathways of Nucleotide excision repair and Alanine, aspartate and glutamate metabolism; unique DAMs in Pf enriched Synchytrium_taraxaci.

Discussion

The core strains identified that interact with different root exudates will provide key clues for regulation of soil microorganisms in P. notoginseng cultivation to alleviate CCO.

[Effects of Aeration Methods on Microbial Diversity and Community Structure in Rice Rhizosphere]

To explore the effects of different aeration methods on the abundance of microorganisms and microorganism community structure in rice rhizosphere soil, two rice varieties, Miyang 46(MY) and Zhenshan 97B(ZS), were used with three aeration treatments:alternate wetting and drying(AWD), continuous flooding and aeration(CFA), and continuous flooding(CF). The diversity of bacterial and fungal communities in rice rhizosphere soil was analyzed using Illumina MiSeq high-throughput sequencing. Soil physical and chemical factors were also analyzed. The results showed that the dominant bacterial communities in rice rhizosphere soil were Chloroflexi, Actinobaciota, Acidobacteria, Proteobacteria, and Firmicutes, and the dominant fungal communities were Ascomycota and Basidiomycota in rice rhizosphere soil. At each growth stage, the relative abundance of Chloroflexi and Acidobacteria was higher in the AWD treatment than in the other treatments, and the relative abundance of Actinobaciota was higher in the CFA treatment than in the other treatments. The relative abundance of Firmicutes was lower in the AWD treatment than in the other treatments. Aeration methods affected the diversity and richness of rhizosphere microbial species. For example, the diversity of bacterial species was higher, and the richness of bacterial species was lower in the AWD treatment than that in the other treatments. The diversity and richness of fungal species were higher in the AWD and CFA treatments than those in the CF treatment. The physical and chemical properties of rhizosphere soil were also affected by aeration method. The soil redox potential(Eh) was the highest in AWD, followed by that in CFA and CF, and significant differences were observed among treatments. The NO3--N content was significantly higher, and the NH4+-N content was significantly lower in the AWD and CFA treatments than in the CF treatment in rhizosphere soil at all growth stages. Correlation analysis showed that the pH and Eh of rhizosphere soil were positively correlated with the diversity of bacterial species, negatively correlated with the richness of bacterial species, and positively correlated with the diversity and richness of fungal species. Redundancy analysis indicated that the relative abundance of Chloroflexi was positively correlated with the pH and NH4+-N content at each period, positively correlated with the Eh and NO3--N content at the tillering and heading stages, and negatively correlated with Eh and NO3--N content at the maturity stage. At each growth stage, the pH and Eh were positively correlated with the relative abundance of Acidobacteria, Proteobacteria, and Basidiomycota and negatively correlated with the relative abundance of Firmicutes and Ascomycota. During the entire growth period, the relative abundance of Ascomycota was negatively correlated with the NO3--N content and positively correlated with the NH4+-N content, and the opposite patterns were observed for the relative abundance of Basidiomycota. In summary, rhizosphere oxygenation enhanced the soil oxygen environment, altered soil physical and chemical properties, and affected microbial community diversity and richness to optimize microbial community structure.

Phylosymbiosis: The Eco-Evolutionary Pattern of Insect-Symbiont Interactions

Insects harbor diverse assemblages of bacterial and fungal symbionts, which play crucial roles in host life history. Insects and their various symbionts represent a good model for studying host-microbe interactions. Phylosymbiosis is used to describe an eco-evolutionary pattern, providing a new cross-system trend in the research of host-associated microbiota. The phylosymbiosis pattern is characterized by a significant positive correlation between the host phylogeny and microbial community dissimilarities. Although host-symbiont interactions have been demonstrated in many insect groups, our knowledge of the prevalence and mechanisms of phylosymbiosis in insects is still limited. Here, we provide an order-by-order summary of the phylosymbiosis patterns in insects, including Blattodea, Coleoptera, Diptera, Hemiptera, Hymenoptera, and Lepidoptera. Then, we highlight the potential contributions of stochastic effects, evolutionary processes, and ecological filtering in shaping phylosymbiotic microbiota. Phylosymbiosis in insects can arise from a combination of stochastic and deterministic mechanisms, such as the dispersal limitations of microbes, codiversification between symbionts and hosts, and the filtering of phylogenetically conserved host traits (incl., host immune system, diet, and physiological characteristics).

Intercropping system modulated soil-microbe interactions that enhanced the growth and quality of flue-cured tobacco by improving rhizospheric soil nutrients, microbial structure, and enzymatic activities

As the promotive/complementary mechanism of the microbe-soil-tobacco (Nicotiana tabacum L.) interaction remains unclear and the contribution of this triple interaction to tobacco growth is not predictable, the effects of intercropping on soil nutrients, enzymatic activity, microbial community composition, plant growth, and plant quality were studied, and the regulatory mechanism of intercropping on plant productivity and soil microenvironment (fertility and microorganisms) were evaluated. The results showed that the soil organic matter (OM), available nitrogen (AN), available phosphorus (AP), available potassium (AK), the urease activity (UE) and sucrase activity (SC), the diversity, abundance, and total and unique operational taxonomic units (OTUs) of bacteria and fungi as well as plant biomass in T1 (intercropping onion), T2 (intercropping endive), and T3 (intercropping lettuce) treatments were significantly higher than those of the controls (monocropping tobacco). Although the dominant bacteria and fungi at the phylum level were the same for each treatment, LEfSe analysis showed that significant differences in community structure composition and the distribution proportion of each dominant community were different. Proteobacteria, Acidobacteria, and Firmicutes of bacteria and Ascomycota and Basidiomycetes of fungi in T1, T2, and T3 treatments were higher than those of the controls. Redundancy analysis (RDA) suggested a close relation between soil characteristic parameters and microbial taxa. The correlation analysis between the soil characteristic parameters and the plant showed that the plant biomass was closely related to soil characteristic parameters. In conclusion, the flue-cured tobacco intercropping not only increased plant biomass and improved chemical quality but also significantly increased rhizospheric soil nutrient and enzymatic activities, optimizing the microbial community composition and diversity of rhizosphere soil. The current study highlighted the importance of microbe-soil-tobacco interactions in maintaining plant productivity and provided the potential fertilization practices in flue-cured tobacco production to maintain ecological sustainability.

The impact of main Areca Catechu root exudates on soil microbial community structure and function in coffee plantation soils

Coffee is an important cash crop worldwide, but it has been plagued by serious continuous planting obstacles. Intercropping with Areca catechu could alleviate the continuous planting obstacle of coffee due to the diverse root secretions of Areca catechu. However, the mechanism of Areca catechu root secretion in alleviating coffee continuous planting obstacle is still unclear. The changes of coffee rhizosphere soil microbial compositions and functions were explored by adding simulated root secretions of Areca catechu, the primary intercropping plant species (i.e., amino acids, plant hormone, organic acids, phenolic acids, flavonoids and sugars) in current study. The results showed that the addition of coffee root exudates altered soil physicochemical properties, with significantly increasing the availability of potassium and organic matter contents as well as promoting soil enzyme activity. However, the addition of plant hormone, organic acids, or phenolic acids led to a decrease in the Shannon index of bacterial communities in continuously planted coffee rhizosphere soil (RS-CP). The inclusion of phenolic acids specifically caused the decrease of fungal Shannon index. Plant hormone, flavonoids, phenolic acids, and sugars increased the relative abundance of beneficial bacteria with reduced bacterial pathogens. Flavonoids and organic acids increased the relative abundance of potential fungal pathogen Fusarium. The polyphenol oxidase, dehydrogenase, urease, catalase, and pH were highly linked with bacterial community structure. Moreover, catalase, pH, and soil-available potassium were the main determinants of fungal communities. In conclusion, this study highlight that the addition of plant hormone, phenolic acids, and sugars could enhance enzyme activity, and promote synergistic interactions among microorganisms by enhancing the physicochemical properties of RS-CP, maintaining the soil functions in coffee continuous planting soil, which contribute to alleviate the obstacles associated with continuous coffee cultivation.

The Volatile Flavor Substances, Microbial Diversity, and Their Potential Correlations of Inner and Surface Areas within Chinese Qingcheng Mountain Traditional Bacon

The objective of this study was to explore the microbial diversity, volatile flavor substances, and their potential correlations in inner and surface Chinese Qingcheng Mountain traditional bacon (CQTB). The results showed that there were 39 volatile flavor substances in inner and surface CQTB detected by headspace solid-phase microextraction and gas chromatography-mass spectrometry (HS-SPME-GC-MS). Moreover, significant differences in volatile flavor substances between the inner and surface CQTB were observed. Sixteen key volatile flavor substances were screened (OAV > 1), including guaiacol, nonanal, ethyl isovalerate, and others. High-throughput sequencing (HTS) result indicated that Firmicutes, Proteobacteria, and Actinobacteria were the predominant bacterial phyla, and Ascomycota and Mucoromycota were the predominant fungal phyla. Staphylococcus, Psychrobacter, and Brochothrix were the predominant bacteria, and Debaryomyces, Penicillium, and Mucor were the predominant fungal genera. Spearman correlation coefficient analysis suggested that Apiotrichum and Lactobacillus were closely and positively correlated with the formation of key phenol compounds. The present work demonstrates the microbial diversity and related volatile flavor substances and their potential correlations in CQTB and provides a theoretical basis for the development of microbial starter culture and green processing of CQTB.

Ecologically different earthworm species are the driving force of microbial hotspots influencing Pb uptake by the leafy vegetable Brassica campestris

Food chain contamination by soil lead (Pb), beginning with Pb uptake by leafy vegetables, is a threat to food safety and poses a potential risk to human health. This study highlights the importance of two ecologically different earthworm species (the anecic species Amynthas aspergillum and the epigeic species Eisenia fetida) as the driving force of microbial hotspots to enhance Pb accumulation in the leafy vegetable Brassica campestris at different Pb contamination levels (0, 100, 500, and 1,000 mg·kg-1). The fingerprints of phospholipid fatty acids (PLFAs) were employed to reveal the microbial mechanism of Pb accumulation involving earthworm-plant interaction, as PLFAs provide a general profile of soil microbial biomass and community structure. The results showed that Gram-positive (G+) bacteria dominated the microbial community. At 0 mg·kg-1 Pb, the presence of earthworms significantly reduced the total PLFAs. The maximum total of PLFAs was found at 100 mg·kg-1 Pb with E. fetida inoculation. A significant shift in the bacterial community was observed in the treatments with E. fetida inoculation at 500 and 1,000 mg·kg-1 Pb, where the G+/G- bacteria ratio was significantly decreased compared to no earthworm inoculation. Principal component analysis (PCA) showed that E. fetida had a greater effect on soil microbial hotspots than A. aspergillum, thus having a greater effect on the Pb uptake by B. campestris. Redundancy analysis (RDA) showed that soil microbial biomass and structure explained 43.0% (R2 = 0.53) of the total variation in Pb uptake by B. campestris, compared to 9.51% of microbial activity. G- bacteria explained 23.2% of the total variation in the Pb uptake by B. campestris, significantly higher than the other microbes. The Mantel test showed that microbial properties significantly influenced Pb uptake by B. campestris under the driving force of earthworms. E. fetida inoculation was favorable for the G- bacterial community, whereas A. aspergillum inoculation was favorable for the fungal community. Both microbial communities facilitated the entry of Pb into the vegetable food chain system. This study delivers novel evidence and meaningful insights into how earthworms prime the microbial mechanism of Pb uptake by leafy vegetables by influencing soil microbial biomass and community composition. Comprehensive metagenomics analysis can be employed in future studies to identify the microbial strains promoting Pb migration and develop effective strategies to mitigate Pb contamination in food chains.

[Effects of Nitrogen Speciation Transformation on Microbial Community Succession in Input Rivers of Miyun Reservoir]

The Miyun Reservoir is the major source of surface drinking water in Beijing. However, the total nitrogen (TN) concentrations in the Miyun Reservoir and inflowing rivers have recently been increasing. In this study, the Mangniu River, a typical inflow river in the upper reaches of the Miyun Reservoir, was selected as the study area to investigate the spatial distribution and transformation of various nitrogen forms from the perspective of microbial community composition and predicting function, aimimg at providing a scientific reference for nitrogen pollution control of the Miyun Reservoir. The results indicated that except for TN, all the other physical and chemical water quality indicators in the upper reaches of the Miyun Reservoir met the Class II criteria of the environmental quality standards for surface water in China (GB 3838-2002). Additionally, NO3--N was the primary constituent of TN, ranging from 77.7% to 92.9%. Banchengzi Reservoir has a certain self-purification ability because its high C/N ratio promotes denitrification. Significant differences in microbial community structure were observed between the water and sediments of Mangniu River along with spatial distribution. High NO3--N concentration was the major environmental factor affecting the succession of microbial community structure. Many nitrification and denitrification microorganisms existed in Mengniu River, and the relative abundance of denitrification bacteria (DNB) was higher than that of nitrification bacteria, and that in the sediments was slightly higher than that in the water. Nitrosopumilus and Pseudomonas were the dominant nitrification and denitrification bacteria in Mengniuhe River, respectively. The results of phylogenetic investigation of communities by the reconstruction of unobserved states (PICRUSt2) showed that NO3--N reduction module was the major nitrogen metabolism module, which primarily occurred in water. The abundance of the functional genes for nitrification (i.e., narGH) was the highest in water, and the major functional gene involved in NO3--N reduction was nirBD of DNRA, which was primarily present in the sediments; however, the main functional gene involved in denitrification was nirK.

Comparative study on physicochemical properties, microbial composition, and the volatile component of different light flavor Daqu

Baijiu, a type of liquor, is known for its pure fragrance and softness. Its unique style is attributed to the complex microbial flora and flavor precursors found in Daqu. In order to elaborate the nature of light flavor Daqu to guide the baijiu production, four Daqu samples (DQ1, DQ2, DQ3, and DQ4) from Shanxi province were analyzed to determine their microbial structure, physicochemical properties, and volatile flavors using high-throughout put seqencing and headspace solid-phase microextraction/gas chromatography-mass spectrometry method in this study. The findings indicated that there were no noticeable variations in the water content and esterase activity of the four Daqu. However, the DQ2 sample had a higher acidity value and saccharifying enzyme activity, whereas DQ3 had the highest protease activity. The microbial community structure of the four Daqu was similar, with Lactobacillus and Streptophyta as the dominant bacteria, but the abundance of bacteria was different among the four Daqu. Issachenkia was a common dominant fungus genus in all samples. Rhizopus and Lichtemia were higher in DQ1 and DQ2, while Torulaspora, Aspergillus, and Candida were more prevalent in DQ4. A total of 27 volatile components were detected in the four Daqu, including esters, alcohols, ketones, aldehydes, and acids. DQ2 had the most volatile components and ethyl lactate and ethyl acetate were the most significant esters in the four samples. In conclusion, the physicochemical indicators of the four light flavor Daqu had distinct differences. There were significant variations in the abundance of bacteria and fungi, leading to differences in the volatile component content. These research findings can serve as a theoretical foundation for blending different light flavors Daqu and hold great significance in enhancing the quality of baijiu.

Proteins released into the plant apoplast by the obligate parasitic protist Albugo selectively repress phyllosphere-associated bacteria

Biotic and abiotic interactions shape natural microbial communities. The mechanisms behind microbe-microbe interactions, particularly those protein based, are not well understood. We hypothesize that released proteins with antimicrobial activity are a powerful and highly specific toolset to shape and defend plant niches. We have studied Albugo candida, an obligate plant parasite from the protist Oomycota phylum, for its potential to modulate the growth of bacteria through release of antimicrobial proteins into the apoplast. Amplicon sequencing and network analysis of Albugo-infected and uninfected wild Arabidopsis thaliana samples revealed an abundance of negative correlations between Albugo and other phyllosphere microbes. Analysis of the apoplastic proteome of Albugo-colonized leaves combined with machine learning predictors enabled the selection of antimicrobial candidates for heterologous expression and study of their inhibitory function. We found for three candidate proteins selective antimicrobial activity against Gram-positive bacteria isolated from A. thaliana and demonstrate that these inhibited bacteria are precisely important for the stability of the community structure. We could ascribe the antibacterial activity of the candidates to intrinsically disordered regions and positively correlate it with their net charge. This is the first report of protist proteins with antimicrobial activity under apoplastic conditions that therefore are potential biocontrol tools for targeted manipulation of the microbiome.

Positive effects of lignocellulose on the formation and stability of aerobic granular sludge

Introduction

Lignocellulose is one of the major components of particulate organic matter in sewage, which has a significant influence on biological wastewater treatment process. However, the effect of lignocellulose on aerobic granular sludge (AGS) system is still unknown.

Methods

In this study, two reactors were operated over 5 months to investigate the effect of lignocellulose on granulation process, structure stability and pollutants removal of AGS.

Results and discussion

The results indicated that lignocellulose not only promoted the secretion of tightly bound polysaccharide in extracellular polymeric substances, but also acted as skeletons within granules, thereby facilitating AGS formation, and enhancing structural strength. Lignocellulose imposed little effect on the removal efficiency of pollutants, with more than 95, 99, and 92% of COD, NH4+-N, and PO43--P were removed in both reactors. However, it did exhibit a noticeable influence on pollutants conversion processes. This might be due to that the presence of lignocellulose promoted the enrichment of functional microorganisms, including Candidatus_Accumulibacter, Candidatus_Competibacter, Nitrosomonas, and Nitrospira, etc. These findings might provide valuable insights into the control strategy of lignocellulose in practical AGS systems.

Effects of tea oil camellia (Camellia oleifera Abel.) shell-based organic fertilizers on the physicochemical property and microbial community structure of the rhizosphere soil

Soil microorganisms play important roles in promoting soil ecosystem restoration, but much of the current research has been limited to changes in microbial community structure in general, and little is known regarding the soil physicochemical property and microbial community structure. In this study, four organic fertilizers were first prepared based on tea oil camellia shell (TOCS). Our findings indicate that the application of BOFvo increased both total pore volume and BET surface area of the rhizosphere soils, as well there was a remarkable enhancement in total organic matter (TOM), total nitrogen (TN), available nitrogen (AN), total phosphorus (TP), total potassium (TK), and available potassium (AK) contents of the rhizosphere soils. Meanwhile, in comparison to the CK and CF groups, the utilization of BOFvo led to a substantial increase in both average yield and fruiting rate per plant at maturity, as well resulted in a significant increase in TN and TP contents of tea oil camellia leaves. Furthermore, our findings suggest that the application of TOCS-based organic fertilizers significantly enhances the microbial diversity in the rhizosphere soils with Proteobacteria and Ascomycota being the dominant bacterial and fungal phyla, respectively, and Rhodanobacter and Fusarium being the dominant bacterial and fungal genus, respectively. Redundancy analysis (RDA) indicates that the physicochemical characteristics of TOCS-based organic fertilizers had a significant impact on the composition and distribution of microbial communities in the rhizosphere soils. This study will facilitate the promotion and application of TOCS-based organic fertilizers, thereby establishing a foundation for the reuse of tea oil camellia waste resources.

Effect of the Combination of Phosphate-Solubilizing Bacteria with Orange Residue-Based Activator on the Phytoremediation of Cadmium by Ryegrass

Amendments with activators or microorganisms to enhance phytoremediation in toxic-metal-polluted soils have been widely studied. In this research, the production of indoleacetic acid, siderophore, and 1-aminocyclopropane-1-carboxylate (ACC) deaminase by phosphate-solubilizing bacteria was investigated during a pure culture experiment. Pot experiments were performed using Cd-polluted soil with the following treatments: control (CK, only ultrapure water), orange-peel-based activator (OG), and a combination of phosphate-solubilizing bacteria (Acinetobacter pitti) and OG (APOG). Ryegrass plant height and fresh weight, Cd content in ryegrass, total and available Cd soil content, soil enzyme activity, and soil bacterial diversity were determined in this work. The findings showed that the height of ryegrass in OG and APOG increased by 14.78% and 21.23%. In the APOG group, a decreased ratio of Cd was 3.37 times that of CK, and the bioconcentration factor was 1.28 times that of CK. The neutral phosphatase activity of APOG was 1.33 times that of CK and catalase activity was 1.95 times that of CK. The activity of urease was increased by 35.48%. APOG increased the abundance of beneficial bacteria and Proteobacteria was the dominant bacterium, accounting for 57.38% in APOG. Redundancy analysis (RDA) showed that nutrient elements were conducive to the propagation of the dominant bacteria, the secretion of enzymes, and the extraction rate of Cd in the soil. The possible enhancement mechanism of phytoremediation of cadmium by A. pitti combined with OG was that, on the one hand, APOG increased soil nutrient elements and enzyme activities promoted the growth of ryegrass. On the other hand, APOG activated Cd and boosted the movement of Cd from soil to ryegrass. This research offers insight for the combination of phosphate-solubilizing bacteria with an orange-peel-based activator to improve phytoremediation of Cd-contaminated soils and also provides a new way for the resource utilization of fruit residue.

Straw mulch improves soil carbon and nitrogen cycle by mediating microbial community structure and function in the maize field

This study was conducted to investigate the capability of the microbial community characteristics and soil variables to promote carbon and nitrogen cycles in maize fields under straw mulch. We covered the surface soil of the maize field with different amounts of wheat straw (0 kg/ha, 2,250 kg/ha, and 4,500 kg/ha) and used 16S rRNA and ITS sequencing, Biology ECO-plate, traditional enzymology, TOC analyzer, and HPLC to measure bacterial and fungal community composition and functions, characteristics of microbial carbon source metabolism, carbon and nitrogen fraction, enzyme activity, and organic acid content in the maize rhizosphere and non-rhizosphere. The results indicated that short-term straw mulch insignificantly affected the alpha diversity of bacterial and fungal communities whereas significantly influenced their beta diversity. The results of functional prediction revealed that straw mulch considerably boosted the relative abundances of bacteria belonging to chemoheterotrophy, aerobic chemoheterotrophy, ureolysis, and nitrogen fixation and inhibited fermentation and nitrate reduction in maize rhizosphere soil. These processes primarily drove the C and N cycles in soil. Straw mulch also improved fungal saprotrophs by raising the proportion of Chaetomiaceae and Chaetosphaeriaceae. The Biology ECO-plate results illustrated that straw mulch weakened the metabolism capacity of microbial labile carbon resources. As a result, the labile C and N fractions were raised under straw mulch. Our results also showed that straw mulch primarily regulated the microbial community structure in rhizosphere soil by significantly decreasing Firmicutes and Ascomycota relative abundance while increasing Basidiomycota. The fungal community structure is more than bacterial for affecting soil microbial biomass carbon, readily oxidizable organic carbon, dissolved organic carbon, available nitrogen, ammonium, and nitrate directly and indirectly through malic acid content and cellulase, protease, and amylase activity. Overall, our findings imply that straw mulch might influence the bacterial and fungal community structures, thereby boosting the production of labile C and N components and accelerating the C and N cycle in maize fields.

Pragmatic Considerations When Extracting DNA for Metagenomics Analyses of Clinical Samples

Microbiome analyses are essential for understanding microorganism composition and diversity, but interpretation is often challenging due to biological and technical variables. DNA extraction is a critical step that can significantly bias results, particularly in samples containing a high abundance of challenging-to-lyse microorganisms. Taking into consideration the distinctive microenvironments observed in different bodily locations, our study sought to assess the extent of bias introduced by suboptimal bead-beating during DNA extraction across diverse clinical sample types. The question was whether complex targeted extraction methods are always necessary for reliable taxonomic abundance estimation through amplicon sequencing or if simpler alternatives are effective for some sample types. Hence, for four different clinical sample types (stool, cervical swab, skin swab, and hospital surface swab samples), we compared the results achieved from extracting targeted manual protocols routinely used in our research lab for each sample type with automated protocols specifically not designed for that purpose. Unsurprisingly, we found that for the stool samples, manual extraction protocols with vigorous bead-beating were necessary in order to avoid erroneous taxa proportions on all investigated taxonomic levels and, in particular, false under- or overrepresentation of important genera such as Blautia, Faecalibacterium, and Parabacteroides. However, interestingly, we found that the skin and cervical swab samples had similar results with all tested protocols. Our results suggest that the level of practical automation largely depends on the expected microenvironment, with skin and cervical swabs being much easier to process than stool samples. Prudent consideration is necessary when extending the conclusions of this study to applications beyond rough estimations of taxonomic abundance.

The differences in main components, enzyme activity, and microbial composition between substandard and normal jiuyao

BACKGROUND

Jiuyao is a critical fermenting agent in traditional huangjiu brewing and it affects the quality of huangjiu. To assess and monitor the quality of jiuyao effectively we determined the differences between two common types of substandard jiuyao and normal jiuyao, with emphasis on the comparison of the main components, enzymatic activity, volatile substances, and microbial community structure.

RESULTS

The water and starch content, acid protease activity, and esterification capability of type I substandard jiuyao were significantly lower than those of the normal jiuyao, and the protein contents, liquefaction capability, glycation capability, and neutral protease activity were substantially higher than those of the normal jiuyao. Type II substandard jiuyao had significantly lower indices than the normal group except for the starch and free amino acid content, which were significantly higher than those of the normal jiuyao. Significant differences were observed between substandard and normal jiuyao in the content of 21 volatile compounds. 2-Pentylfuran could be used as a marker of substandard jiuyao. Type I substandard jiuyao contained a higher abundance of aerobic Pediococcus and Marivita in comparison with the normal jiuyao. Type II substandard jiuyao consisted of a greater abundance of anaerobic Mucor and Staphylococcus.

CONCLUSION

The quality of jiuyao was significantly affected by the water content. Due to the different abundances of aerobic and anaerobic bacteria in jiuyao, oxygen may also be an important parameter affecting the quality of jiuyao. We believe that the present study offers a theoretical basis for the evaluation and control of the quality of jiuyao. © 2023 Society of Chemical Industry.

Reinforced Bioremediation of Excessive Nitrate in Atrazine-Contaminated Soil by Biodegradable Composite Carbon Source

Bioremediation is a good alternative to dispose of the excessive nitrate (NO₃^-) in soil and alleviate the secondary salinization of soil, but the presence of atrazine in soil interferes with the bioremediation process. In the present study, the biodegradable composite carbon source with different dosages was added to the atrazine-contaminated soil to intensify the bioremediation of excessive NO₃^-. The atrazine-contaminated soil with a 25 g/kg composite carbon source achieved the optimal NO₃^- removal performance (92.10%), which was slightly higher than that with a 5 g/kg composite carbon source (86.15%) (p > 0.05). Unfortunately, the negative effects of the former were observed, such as the distinctly higher emissions of N₂O, CO₂ and a more powerful global warming potential (GWP). Microbial community analysis showed that the usage of the composite carbon source clearly decreased the richness and diversity of the microbial community, and greatly stimulated nitrogen metabolism and atrazine degradation (p < 0.05). To sum up, the application of a 5 g/kg composite carbon source contributed to guaranteeing bioremediation performance and reducing adverse environmental impacts at the same time.

Enhancing Nitrogen Removal Efficiency and Anammox Metabolism in Microbial Electrolysis Cell Coupled Anammox Through Different Voltage Application

The slow growth and difficulty in cultivating anammox bacteria limit the rapid start-up of anammox process and effective microbial enrichment. In this study, microbial electrolysis cell (MEC) was coupled with anammox to investigate the effects of different applying voltage methods on substrate removal efficiency and rates, microbial community structure, anammox metabolism and metabolic pathways. The results showed that applying voltage not only improved NH₄⁺-N removal efficiency and removal rates, but also promoted electron transfer efficiency, key enzyme activity and extracellular polymeric substances (EPS) secretion in the systems. Step-up voltage was more conducive to the growth of Candidatus_Kuenenia in the cathode, which promoted the rapid start-up of anammox and treating wastewater with low ammonia concentration. The main metabolic pathway in step-up voltage operation was hydrazine to nitrogen, while in constant voltage operation was hydroxylamine oxidation pathway. These findings provide a new insight into the enhancement and operation of anammox system.

Variations in soil microbial community structure and extracellular enzymatic activities along a forest-wetland ecotone in high-latitude permafrost regions

Permafrost degradation by global warming is expected to alter the hydrological processes, which results in changes in vegetation species composition and gives rise to community succession. Ecotones are sensitive transition areas between ecosystem boundaries, attract particular interest due to their ecological importance and prompt responses to the environmental variables. However, the characteristics of soil microbial communities and extracellular enzymes along the forest-wetland ecotone in high-latitude permafrost region remain poorly understood. In this study, we evaluated the variations of soil bacterial and fungal community structures and soil extracellular enzymatic activities of 0-10 cm and 10-20 cm soil layers in five different wetland types along environmental gradients, including Larix gmelinii swamp (LY), Betula platyphylla swamp (BH), Alnus sibirica var. hirsute swamp (MCY), thicket swamp (GC), and tussock swamp (CC). The relative abundances of some dominant bacterial (Actinobacteria and Verrucomicrobia) and fungal (Ascomycota and Basidiomycota) phyla differed significantly among different wetlands, while bacterial and fungal alpha diversity was not strongly affected by soil depth. PCoA results showed that vegetation type, rather than soil depth explained more variation of soil microbial community structure. β-glucosidase and β-N-acetylglucosaminidase activities were significantly lower in GC and CC than in LY, BH, and MCY, while acid phosphatase activity was significantly higher in BH and GC than LY and CC. Altogether, the data suggest that soil moisture content (SMC) was the most important environmental factor contributing to the bacterial and fungal communities, while extracellular enzymatic activities were closely related to soil total organic carbon (TOC), nitrate nitrogen (NO3--N) and total phosphorus (TP).

Analysis of the microbial community structure and flavor components succession during salt-reducing pickling process of zhacai (preserved mustard tuber)

The salt-reducing pickling method has been applied to the industrial production of zhacai. In order to reveal the succession of the microbial community structure and flavor components during the pickling process, this study used PacBio Sequel to sequence the full length of 16S rRNA (bacteria, 1400 bp) and ITS (fungi, 1200 bp) genes, and detected flavor components simultaneously, including organic acids, volatile flavor components (VFC), monosaccharides, and amino acids. Eleven phyla and 148 genera were identified in the bacterial community, and 2 phyla and 60 genera in the fungal community. During the four stages of pickling, the dominant bacterial genera were Leuconostoc, Lactobacillus, Leuconostoc, and Lactobacillus, while the dominant fungal genera were Aspergillus, Kazachstania, Debaryomyces, and Debaryomyces, respectively. There were 32 main flavor components (5 organic acids, 19 VFCs, 3 monosaccharides, and 5 amino acids). Correlation heat mapping and bidirectional orthogonal partial least squares (O2PLS) analysis showed that the flora having close relation to flavor components included 14 genera of bacteria (Leuconostoc, Clostridium, Devosia, Lactococcus, Pectobacterium, Sphingobacterium, Serratia, Stenotrophomonas, Halanaerobium, Tetragenococcus, Chromohalobacter, Klebsiella, Acidovorax, and Acinetobacter) and 3 genera of fungi (Filobasidium, Malassezia, and Aspergillus). This study provides detailed data regarding the microbial community and flavor components during the salt-reducing pickling process of zhacai, which can be used as a reference for the development and improvement of salt-reducing pickling methods.

The effects of adding exogenous lignocellulose degrading bacteria during straw incorporation in cold regions on degradation characteristics and soil indigenous bacteria communities

Low temperature is one of the bottleneck factors that limits the degradation of straw during rice straw incorporation. Determining strategies to promote the efficient degradation of straw in cold regions has become a highly active research area. This study was to investigate the effect of rice straw incorporation by adding exogenous lignocellulose decomposition microbial consortiums at different soil depths in cold regions. The results showed that the lignocellulose was degraded the most efficiently during straw incorporation, which was in deep soil with the full addition of a high-temperature bacterial system. The composite bacterial systems changed the indigenous soil microbial community structure and diminished the effect of straw incorporation on soil pH, it also significantly increased rice yield and effectively enhanced the functional abundance of soil microorganisms. The predominant bacteria SJA-15, Gemmatimonadaceae, and Bradyrhizobium promoted straw degradation. The concentration of bacterial system and the depth of soil had significantly positive correlations on lignocellulose degradation. These results provide new insights and a theoretical basis for the changes in the soil microbial community and the application of lignocellulose-degrading composite microbial systems with straw incorporation in cold regions.

Chemical and microbiological characterization of pig manures and digestates

Livestock and poultry breeding modes, feed compositions and manure collection systems have regional characteristics, which can directly affect the composition of livestock and poultry breeding manure, energy production by anaerobic digestion and resource utilization of products. The chemical, heavy metal contents and microbiological characteristics of pig manures and digestates were characterized in five pig farms and biogas plants in Quzhou (Zhejiang Province) in this study. The results showed that hemicellulose and cellulose of pig manures could be partly degraded in anaerobic digestion, but lignin was difficultly degraded and accumulated in digestates. The content of Zn was highest in the pig manure and digestate samples, followed by Cu, Cr, As, Ni, Pb, Cd, T1 and Hg. The As content was 16.09-31.22 mg kg^-1 in the pig manure and digestate samples, which exceeded the standard limitation requirements in fertilizers in China (≤15 mg kg^-1). Bacteroidota, Firmicutes, Proteobacteria and Spirochaetota dominated in the pig manure and digestate samples, with a relative abundance of 73.6%-99.4%. The microbial community structure in the pig manure samples was quite different among the five farms. The pH, contents of lignin, T1 and As had a significant effect on the microbial community structure in the pig manure samples, while the contents of total phosphorus, NO₃^--N, cellulose and Pb could significantly influence the microbial community structure in the digestate samples. These findings can provide a theoretical basis for recycling manure and improving biogas engineering in large-scale pig farms.

Synergetic effects of pyrrhotite and biochar on simultaneous removal of nitrate and phosphate in autotrophic denitrification system

In the trend of upgrading wastewater treatment plants, developing advanced treatment technologies for more efficient nutrient removal is crucial. This study prepared a pyrrhotite-biochar composite (Fe_x S_y @BC) to investigate its potential for simultaneous removal of nitrate and phosphate under autotrophic denitrification conditions. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) were used to characterize the novel composite of Fe_x S_y @BC, which exhibited 9.2 mg N/(L·d) NO₃ ^- -N reduction rate, 97.3% N₂ production, and 81.8 mmol N/(kg·d) NO₃ ^- -N material load with small solid/liquid ratio (0.008). The NO₃ ^- -N removal with Fe_x S_y @BC was 1.2-2.2 times higher than that with pure iron sulfides or biochar or their mixtures, whereas the Δn(S)/Δn(N) of Fe_x S_y @BC was the lowest (1.80). Moreover, the PO₄ ^3- -P reduction rate of Fe_x S_y @BC reached 3.23 mg P/(L·d), as high as that of pure pyrite or pyrrhotite. Thiobacillus was the most dominant denitrifying bacterium. Fe_x S_y @BC exhibited great promise for enhancing nutrient removal from secondary effluent without additional carbon source. PRACTITIONER POINTS: FexSy@BC enhanced nitrate and phosphate removal simultaneously. First-order kinetics and Monod model were fitted for denitrification with FexSy@BC. FexSy@BC had smaller molar ratio of sulfate release to nitrate removal. Thiobacillus was the dominant bacterium in FexSy@BC autotrophic denitrification. Synergistic effects on nutrients removal existed between biochar and pyrrhotite.

Variation characteristics of microorganisms at different soil depths of typical forests in southwest China

Microbial biomass and community structure play a significant role in soil carbon cycling. There is a large amount of organic carbon in the subsoil, but most studies on soil microbial community have focused on the surface soil. The changes and influencing mechanisms of microbial community in subsoil are unclear. We analyzed soil microbial biomass and community structure at different soil depths (0-20, 20-40, 40-60, 60-80, and 80-100 cm) in three typical forests in southwest China, Xishuangbanna tropical rain forest, Ailao Mountain subtropical broad-leaved forest, and Lijiang temperate coniferous forest, by using phospholipid fatty acid technology, to explore their variation characteristics and influencing factors in different forests and soil depths. The results showed that contents of soil organic carbon and total nitrogen decreased gradually, microbial biomass declined significantly. The ratio of Gram-positive bacteria to Gram-negative bacteria (G⁺:G^-) reduced gradually, while the ratio of fungi to bacteria (F:B) increased with the increasing soil depth. Microbial community turned from G^--dominated which adapted to eutrophic environment into G⁺-dominated which adapted to oligotrophic environment. The three forest types differed little in soil microbial biomass, but different significantly in microbial community structure. Ailao Mountain subtropical broad-leaved forest and Lijiang temperate coniferous forest had much higher F:B at 0-20 cm than Xishuangbanna tropical rain forest, while significantly higher G⁺:G^- at 0-100 cm in Xishuangbanna tropical rain forest was observed. Results of the redundancy analysis showed that the contents of soil organic carbon and total nitrogen were the main factors determining microbial biomass, with combined explanation of 78.3%. Results of the stepwise regression analysis showed that C:N was the most important driving factor on F:B and G⁺:G^-. The change in microbial community structure and the decrease in biomass along soil profile might strongly affect the dynamics of soil organic carbon in southwest China forests.

The treatment of high-concentration garlic processing wastewater by UASB-SBR

The treatment of garlic processing wastewater was investigated in a UASB-SBR system. The experimental results showed that UASB was successfully started up after 64 days of continuous operation with COD removal rate of 45%. SBR start-up phase went through 60 days and the COD removal rate achieved 96%. UASB ran under optimal conditions (HRT of 45 h, pH of 7.5, and temperature of 35 ± 2°C) for 14d and performed well in organic matter treatment. SBR played a major part in nitrogen and phosphorus removal when running under optimal conditions (cycle time of 12 h, temperature of 25°C, organic loading of 0.72 kgCOD/(m³·d), and COD of 6000 mg/L) for 18d. Secondly, the microbial community structure indicated that the abundance of β-Proteobacteria and α-Proteobacteria in the sludge reached 30.05% and 47.57%, respectively, and played a crucial part for the organic matter, nitrogen and phosphorus removal in the SBR. After UASB-SBR system had been stabilised with influent COD of 9800 mg/L, the average COD, TP, NH₃-N and TN removal rates were 99%, 94.82%, 87.07% and 94.87%, respectively, which were 3%, -2%, 1% and 3.5% higher than SBR running alone under optimal conditions. UASB coupled with SBR process had an excellent performance for high-concentration garlic processing wastewater.

Effect of deposit chemistry on microbial community structure and activity: Implications for under-deposit microbial corrosion

Introduction

The deposition of solid particles carried by production fluids from oil and gas companies in horizontal surfaces of different assets has shown to cause severe localised corrosion. Sand, one of the most common deposits in the energy sector pipelines, is frequently mixed with crude, oil, asphaltenes, corrosion inhibitors, and other organic compounds. For this reason, they might favour the metabolic activity of native microbial communities. This study aimed to determine the impact of sand-deposit chemical composition on the microbial community structure and functional attributes of a multispecies consortium recovered from an oilfield and the resulting risk of under-deposit microbial corrosion of carbon steel.

Methods

Sand deposits recovered from an oil pipeline were used in their raw form and compared against the same deposits exposed to heat treatment to remove organic compounds. A four-week immersion test in a bioreactor filled with synthetic produced water and a two-centimeter layer of sand was set up to assess corrosion and microbial community changes.

Results

The raw untreated deposit from the field containing hydrocarbons and treatment chemicals resulted in a more diverse microbial community than its treated counterpart. Moreover, biofilms developed in the raw sand deposit exhibited higher metabolic rates, with functional profile analysis indicating a predominance of genes associated with xenobiotics degradation. Uniform and localized corrosion were more severe in the raw sand deposit compared to the treated sand.

Discussion

The complex chemical composition of the untreated sand might have represented an additional source of energy and nutrients to the microbial consortium, favoring the development of different microbial genera and species. The higher corrosion rate obtained under the untreated sand suggests that MIC occurred due to syntrophic relationships between sulphate reducers or thiosulphate reducers and fermenters identified in the consortium.

[Revealing the Effect of Saline Water Drip Irrigation on Soil Microorganisms in Cotton Fields Based on Metagenomics]

Saline water irrigation has become an important means to alleviate the shortage of freshwater in arid areas. However, long-term saline water irrigation can cause soil salinity accumulation, affect soil microbial community structure, and then affect soil nutrient transformation. In this study, we used metagenomics to investigate the effects of long-term saline water drip irrigation on soil microbial community structure in a cotton field. In the experiment, the salinity of irrigation water (ECw) was set to two treatments:0.35 dS·m^-1 and 8.04 dS·m^-1 (denoted as FW and SW, respectively), and the nitrogen application rates were 0 kg·hm^-2and 360 kg·hm^-2 (denoted as N0 and N360, respectively). The results showed that saline water irrigation increased soil water content, salinity, organic carbon, and total nitrogen content and decreased soil pH and available potassium content. Nitrogen fertilizer application increased soil organic carbon, salinity, and total nitrogen content and decreased soil water content, pH, and available potassium content. The dominant bacterial phyla in each treatment were:Proteobacteria, Actinobacteria, Acidobacteria, Chloroflexi, and Gemmatimonadetes. Saline water irrigation significantly increased the relative abundances of Actinobacteria, Chloroflexi, Gemmatimonadetes, and Firmicutes but significantly decreased the relative abundances of Proteobacteria, Acidobacteria, Cyanobacteria, and Nitrospira. Nitrogen fertilizer application significantly increased the relative abundances of Chloroflexi and Nitrospira but significantly decreased the relative abundances of Acidobacteria, Gemmatimonadetes, Planctomycetes, Cyanobacteria, and Verrucomicrobia. LEfSe analysis showed that saline water irrigation had no significant effect on the number of potential biomarkers, and nitrogen fertilizer application decreased the number of potential biomarkers in soil microbial communities. The correlation network diagram showed that the 20 genera had different degrees of correlation, including 44 positive correlations and 48 negative correlations. The core species in the network diagram were Nocardioides, Streptomyces, Pyrinomonas, Candidatus_Solibacter, and Bradyrhizobium spp. Saline water irrigation increased the relative abundances of the denitrification genes nirK, nirS, nasB, and norC and decreased the relative abundances of the nitrification genes amoB, amoC, and nxrA, whereas nitrogen fertilizer application increased the relative abundances of the nitrification genes amoA, amoB, amoC, hao, and nxrA and decreased the relative abundances of the denitrifying genes narB, napA, nasA, and nosZ. Saline water irrigation could adversely affect soil physicochemical properties; SWC, EC_1:5, and BD were the main driving factors affecting soil microbial community structure and function genes; and soil microorganisms adapted to soil salt stress by regulating species composition.

[Analysis of Microbial Community Characteristics and Function Prediction of MBBR with Magnetic Biocarriers at Low Temperature]

In order to clarify effect of magnetic biocarriers on the performance of MBBR at low temperatures, the microbial diversity, community structure, functional characteristics, and nitrogen metabolism of biofilm in the reaction system were investigated. The results indicated that MBBR with magnetic biocarriers had a better pollutant removal efficiency, with the average removal rates of NH₄⁺-N and TN being 16.2% and 12.1% higher than those in the control group (commercial biocarriers), respectively. Illumina high-throughput sequencing analysis showed that higher diversity and richness of the bacterial community was established in the biofilm of magnetic biocarriers. There were obvious differences in microbial community structure of biofilm between the two biocarrier duos to bacterial magnetic susceptibility. The relative abundances of nitrifying bacteria (e.g., Nitrosomonas and Nitrospira) and denitrifying bacteria (e.g., Sphaerotilus and Zoogloea) were increased in the magnetic biocarriers. Functional prediction analysis with PICRUSt2 showed that the microorganism of magnetic biocarriers had a better total gene function expression level, which was significantly more increased than commercial biocarriers in gene-representing signal transduction mechanisms and intracellular trafficking, secretion, and vesicular transport. Furthermore, most of the abundances of nitrogen metabolism genes were raised in the biofilm of magnetic biocarriers (e.g., genes amo and hao, were responsible for nitrification, and genes nap and nor, which were responsible for denitrification). Magnetic biocarriers increased biofilm potential for denitrification at low temperatures. Our results explained the difference in performance between the two reactors from microbiology and provided the theoretical basis for magnetic biocarrier-enhanced performances of MBBR at low temperatures.

Improved Denitrification Performance of Polybutylene Succinate/Corncob Composite Carbon Source by Proper Pretreatment: Performance, Functional Genes and Microbial Community Structure

Blending biodegradable polymers with plant materials is an effective method to improve the biodegradability of solid carbon sources and save denitrification costs, but the recalcitrant lignin in plant materials hinders the microbial decomposition of available carbon sources. In the present study, corncob pretreated by different methods was used to prepare polybutylene succinate/corncob (PBS/corncob) composites for biological denitrification. The PBS/corncob composite with alkaline pretreatment achieved the optimal NO₃^--N removal rate (0.13 kg NO₃^--N m^-3 day^-1) with less adverse effects. The pretreatment degree, temperature, and their interaction distinctly impacted the nitrogen removal performance and dissolved organic carbon (DOC) release, while the N₂O emission was mainly affected by the temperature and the interaction of temperature and pretreatment degree. Microbial community analysis showed that the bacterial community was responsible for both denitrification and lignocellulose degradation, while the fungal community was primarily in charge of lignocellulose degradation. The outcomes of this study provide an effective strategy for improving the denitrification performance of composite carbon sources.

Effect of incorporation of broccoli residues into soil on occurrence of verticillium wilt of spring-sowing-cotton and on rhizosphere microbial communities structure and function

Cotton verticillium wilt (CVW) represented a typical plant soil-borne disease and resulted in widespread economic losses in cotton production. However, the effect of broccoli residues (BR) on verticillium wilt of spring-sowing-cotton was not clear. We investigated the effects of BR on CVW, microbial communities structure and function in rhizosphere of two cotton cultivars with different CVW resistance using amplicon sequencing methods. Results showed that control effects of BR on CVW of susceptible cultivar (cv. EJ-1) and resistant cultivar (cv. J863) were 58.49% and 85.96%, and the populations of V. dahliae decreased by 14.31% and 34.19%, respectively. The bacterial diversity indices significantly increased in BR treatment, while fungal diversity indices significantly decreased. In terms of microbial community composition, the abilities to recruit bacteria and fungi were enhanced in BR treatment, including RB41, Gemmatimonas, Pontibacter, Streptomyces, Blastococcus, Massilia, Bacillus, and Gibberella, Plectosphaerella, Neocosmospora, Aspergillus and Preussia. However, the relative abundances of Sphingomonas, Nocardioides, Haliangium, Lysobacter, Penicillium, Mortierella and Chaetomidium were opposite tendency between cultivars in BR treatment. According to PICRUSt analysis, functional profiles prediction showed that significant shifts in metabolic functions impacting KEGG pathways of BR treatment were related to metabolism and biosynthesis. FUNGuild analysis indicated that BR treatment altered the relative abundances of fungal trophic modes. The results of this study demonstrated that BR treatment decreased the populations of V. dahliae in soil, increased bacterial diversity, decreased fungal diversity, changed the microbial community structure and function, and increased the abundances of beneficial microorganisms.

Evaluation of dye decolorization using anaerobic granular sludge from an expanded granular sludge bed based on spectrometric and microbiome analyses

The decolorization of 11 dyes by granular sludge from an anaerobic expanded granular sludge bed (EGSB) reactor was evaluated. Biological decolorization of Reactive Red 21, 23, and 180, and Reactive Yellow 15, 17, and 23 in model textile wastewater was observed for the first time after a 7-day incubation (over 94% decolorization). According to the sequencing analysis of 16S rRNA gene amplicons from EGSB granular sludge, the operational taxonomic unit related to Paludibacter propionicigenes showed the highest increase in relative abundance ratios in the presence of dyes (7.12 times on average over 11 dyes) compared to those without dyes.

Effects of bio-augmented Daqu on microbial community, aroma compounds and physicochemical parameters of fermented grains during the brewing of Chinese special-flavor baijiu

BACKGROUND

Bio-augmented Daqu is used to improve the microbial community and physicochemical parameters of fermented grains, thus affecting the flavor and quality of baijiu. This study investigated the effects of bio-augmented Daqu inoculated with Aspergillus niger NCUF413.1 and Saccharomyces cerevisiae NCUF304.1 on the microbial community, aroma compounds, and physicochemical parameters of fermented grains during special-flavor baijiu brewing.

RESULTS

Compared with the control group (CG), the utilization of starch and production of ethanol in the inoculated group (IG) increased by 3.55% and 12.59%, respectively. The use of bio-augmented Daqu changed the bacterial communities. For example, Kroppenstedsia was the dominant bacterial genus (the relative abundance was about 22%) in the CG while Lactobacillus was the main dominant genus (the relative abundance was more than 30%) in the IG on days 20-30. Lactobacillus showed a significant positive correlation with the aroma compounds. The use of bio-augmented Daqu increased the aroma compound content - such as the ethyl heptanoate and ethyl hexanoate content.

CONCLUSION

The addition of bio-augmented Daqu with A. niger and S. cerevisiae could change microbial communities, resulting in an increase in the yield of ethanol and the aroma compound content of fermented grains, thus improving the quality of baijiu. © 2022 Society of Chemical Industry.

[Co-occurrence of Tetracycline Antibiotic Resistance Genes and Microbial Communities in Plateau Wetlands Under the Influence of Human Activities]

The widespread use of antibiotics has led to a large number of antibiotics entering the environment, to which microorganisms have become resistant. In recent years, with the intensification of human activities in the plateau region, the occurrence and migration of antibiotic resistance genes (ARGs) in plateau wetlands have attracted considerable attention. Here, we selected the Caohai National Wetland Park, located in the Yunnan-Guizhou Plateau, as our study area. The contents of tetracyclines, sulfonamides, quinolones, and macrolides in sediments from the upstream (the pristine habitat near the spring eye) and downstream (the sewage discharge outlet of residents) areas of the river in the park were analyzed. Among them, the detection content of tetracycline antibiotics was 103.65-2185 μg·kg^-1, which was the highest antibiotic detection content. To further investigate the occurrence characteristics and influencing factors of tetracycline resistance genes, the influence of environmental factors, bacterial community structure, and pathogenic bacteria on tetracycline ARGs under the influence of human activities were revealed via correlation analysis and network analysis. The results showed that a total of 15 tetracycline resistance genes were detected in the upstream and downstream sediments. Among them, seven resistance genes including tetPA, tetD, and tetPB were detected in the upstream, and 13 resistance genes such as tetPA, tetE, tetM, and tetX were detected in the downstream. The abundance of eight new resistance genes in the downstream accounted for 43.44% of the downstream genes. The tetracycline-like antibiotics and soil physicochemical indicators (i.e., available phosphorus, total organic carbon, nitrate nitrogen, and total phosphorus) were the main environmental factors affecting the distribution of tetracycline ARGs. Additionally, the bacteria detected in the upstream and downstream sediments belonged to 64 bacterial phyla, among which Proteobacteria, Firmicutes, and Bacteroidota were the main phyla affecting the abundance of tetracycline ARGs; meanwhile, 27 pathogenic bacteria were detected in the upstream and downstream sediments. Network analysis showed that the correlation between the eight new resistance genes and pathogens in the downstream area accounted for 70% of the network connectivity, and Listeria monocytogenes, Enterococcus faecalis, and Bacteroides vulgatus were identified as potential hosts for the transmission of tetracycline ARGs. Compared to the pristine habitat, the discharge of domestic sewage introduced large amounts of antibiotics and also changed the microenvironment and microbial community structure of the river wetland. Additionally, it increased the species of ARGs in sediments, which promoted the spread and transmission of ARGs among microorganisms and even pathogens.

The shift of soil microbial community induced by cropping sequence affect soil properties and crop yield

Rational cropping maintains high soil fertility and a healthy ecosystem. Soil microorganism is the controller of soil fertility. Meanwhile, soil microbial communities also respond to different cropping patterns. The mechanisms by which biotic and abiotic factors were affected by different cropping sequences remain unclear in the major grain-producing regions of northeastern China. To evaluate the effects of different cropping sequences under conventional fertilization practices on soil properties, microbial communities, and crop yield, six types of plant cropping systems were performed, including soybean monoculture, wheat-soybean rotation, wheat-maize-soybean rotation, soybean-maize-maize rotation, maize-soybean-soybean rotation and maize monoculture. Our results showed that compared with the single cropping system, soybean and maize crop rotation in different combinations or sequences can increase soil total organic carbon and nutrients, and promote soybean and maize yield, especially using soybean-maize-maize and maize-soybean-soybean planting system. The 16S rRNA and internal transcribed spacer (ITS) amplicon sequencing showed that different cropping systems had different effects on bacterial and fungal communities. The bacterial and fungal communities of soybean monoculture were less diverse when compared to the other crop rotation planting system. Among the different cropping sequences, the number of observed bacterial species was greater in soybean-maize-maize planting setup and fungal species in maize-soybean-soybean planting setup. Some dominant and functional bacterial and fungal taxa in the rotation soils were observed. Network-based analysis suggests that bacterial phyla Acidobacteria and Actinobacteria while fungal phylum Ascomycota showed a positive correlation with other microbial communities. The phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt) result showed the presence of various metabolic pathways. Besides, the soybean-maize-maize significantly increased the proportion of some beneficial microorganisms in the soil and reduced the soil-borne animal and plant pathogens. These results warrant further investigation into the mechanisms driving responses of beneficial microbial communities and their capacity on improving soil fertility during legume cropping. The present study extends our understanding of how different crop rotations effect soil parameters, microbial diversity, and metabolic functions, and reveals the importance of crop rotation sequences. These findings could be used to guide decision-making from the microbial perspective for annual crop planting and soil management approaches.

Surfaces of gymnastic equipment as reservoirs of microbial pathogens with potential for transmission of bacterial infection and antimicrobial resistance

Gymnastic equipment surfaces are shared by many people, and could mediate the transfer of bacterial pathogens. To better understand this detrimental potential, investigations on the reservoirs of bacterial pathogens and antimicrobial resistance on the surfaces of gymnastic equipment were performed by analyzing the bacterial community structures, prevalence of viable bacteria, and presence of antimicrobial resistance on both indoor and outdoor gymnastic facilities. The results of high-throughput 16S rDNA amplicon sequencing showed that Gram-positive bacteria on the surfaces of indoor gymnastic equipment significantly enriched, including the opportunistic pathogen Staphylococcus strains, while Enterobacteriaceae significantly enriched on surfaces of outdoor gymnastic equipment. The analysis of α-diversities showed a higher richness and diversity for bacterial communities on the surfaces of gymnastic equipment than the environment. Analysis of β-diversities showed that the bacterial communities on the surfaces of gymnastic equipment differ significantly from environmental bacterial communities, while the bacterial communities on indoor and outdoor equipment are also significantly different. Thirty-four bacterial isolates were obtained from the surfaces of gymnastic equipment, including three multidrug Staphylococcus and one multidrug resistant Pantoea. In particular, Staphylococcus hemolyticus 5-6, isolated from the dumbbell surface, is a multidrug resistant, hemolytic, high- risk pathogen. The results of quantitative PCR targeting antibiotic resistance related genes (intI1, sul1 and bla _TEM) showed that the abundances of sul1 and bla _TEM genes on the surfaces of gymnastic equipment are higher than the environment, while the abundances of sul1 gene on indoor equipment are higher than outdoor equipment. These results lead to the conclusion that the surfaces of gymnastic equipment are potential dissemination pathways for highly dangerous pathogens as well as antimicrobial resistance, and the risks of indoor equipment are higher than outdoor equipment.