Biofertilizers regulate the soil microbial community and enhance Panax ginseng yields

Linking soil nutrients, microbial community composition, and enzyme activities to saponin content of Paris polyphylla after addition of biochar and organic fertiliser

The application of organic fertilisers and biochar has become widespread in agroforestry ecosystems to enhance the yield and quality of crops and medicinal plants. However, their specific impact on both the yield and quality of Paris polyphylla (P. polyphylla), along with the underlying mechanisms, remains unclear. In this study, we investigated the distinct effects of organic fertiliser (at concentrations of 5% and 10%) and biochar application (at levels of 2% and 4%) on P. polyphylla saponin content. This content is intricately regulated by available soil nutrients, enzyme activities, and microbial community compositions and activities. Our results clearly demonstrated a significant increase in the saponin content, including total saponin, polyphyllin I (PPI), polyphyllin II (PPII), polyphyllin VI (PPVI), and polyphyllin VII (PPVII), in P. polyphylla following the application of both biochar and organic fertiliser. Moreover, in comparison to the control group, the addition of biochar and organic fertiliser led to a considerable rise in the activity of glycosyltransferase enzyme (GTS) and cycloartenol synthase (CAS) in P. polyphylla. Additionally, it increased soil available potassium (AK) and soil organic matter (SOM) concentration, along with the activity of urease, acid phosphatase, and catalase, although biochar amendment resulted in a decrease in nitrate nitrogen (NO3--N) concentration. Crucially, our findings revealed a positive correlation between total saponin content and the activity of CAS in P. polyphylla, soil AK, SOM concentration, and the activities of urease, acid phosphatase, and catalase. Conversely, there was a negative correlation with NO3--N content. Furthermore, the application of organic fertiliser and biochar significantly influenced microbial community structures and specific microbial taxa. Notably, total saponin content exhibited a positive relationship with the relative abundances of Dehalococcoidia, Saccharomycetes, and Agaricomycetes taxa while showing a negative correlation with the abundance of Verrucomicrobiae. In conclusion, the observed increase in saponin content can be attributed to the modulation of specific microbial taxa in soils, as well as alterations in soil nutrients and enzyme activities resulting from the application of biochar and organic fertiliser. This study identifies a potential mechanism for enhancing saponin content in the artificial cultivation of P. polyphylla.

Meta-analysis reveals the effects of microbial inoculants on the biomass and diversity of soil microbial communities

Microbial inoculation involves transplanting microorganisms from their natural habitat to new plants or soils to improve plant performance, and it is being increasingly used in agriculture and ecological restoration. However, microbial inoculants can invade and alter the composition of native microbial communities; thus, a comprehensive analysis is urgently needed to understand the overall impact of microbial inoculants on the biomass, diversity, structure and network complexity of native communities. Here we provide a meta-analysis of 335 studies revealing a positive effect of microbial inoculants on soil microbial biomass. This positive effect was weakened by environmental stress and enhanced by the use of fertilizers and native inoculants. Although microbial inoculants did not alter microbial diversity, they induced major changes in the structure and bacterial composition of soil microbial communities, reducing the complexity of bacterial networks and increasing network stability. Finally, higher initial levels of soil nutrients amplified the positive impact of microbial inoculants on fungal biomass, actinobacterial biomass, microbial biomass carbon and microbial biomass nitrogen. Together, our results highlight the positive effects of microbial inoculants on soil microbial biomass, emphasizing the benefits of native inoculants and the important regulatory roles of soil nutrient levels and environmental stress.

Effects of plants-associated microbiota on cultivation and quality of Chinese herbal medicines

Microbial resource influences the life activities of medicinal plants from several perspectives. Endophytes, rhizosphere microorganisms, and other environmental microorganisms play essential roles in medicinal plant growth and development, plant yield, and clinical efficacy. The microbiota can influence the biosynthesis of active compounds in medicinal plants by stimulating specific metabolic pathways. They induce host plants to improve their resistance to environmental stresses by accumulating secondary metabolites. Microorganisms can interact with their host plants to produce long-term, targeted selection results and improve their ability to adapt to the environment. Due to the interdependence and interaction between microorganisms and medicinal plants, Chinese herbal medicines (CHMs) quality is closely related to the associated microorganisms. This review summarizes the relationship between medicinal plants and their associated microorganisms, including their species, distribution, life activities, and metabolites. Microorganisms can aid in quality control, improve the efficacy of medicinal plants, and provide markers for identifying the origin and storage time of CHMs. Therefore, a comprehensive understanding of the relationship between microorganisms and medicinal plants will help to control the quality of CHMs from different perspectives.

Differences in soil bacterial community structure during the remediation of Cd-polluted cotton fields by biochar and biofertilizer in Xinjiang, China

Introduction

Heavy metal pollution is a major worldwide environmental problem. Many remediation techniques have been developed, these techniques have different performance in different environments.

Methods

In this study, soil sampling was conducted in multiple cotton fields in Xinjiang, China, and found that cadmium (Cd) was the most abundant soil heavy metal. Then, to find the most suitable technique for the remediation of Cd pollution in cotton fields, a two-year study was conducted to explore the effects of cotton straw-derived biochar (BC, 3%) and Bacillus-based biofertilizer (BF, 1.5%) on cotton Cd uptake and transport and soil microbial community structure under Cd exposure conditions (soil Cd contents: 1, 2, and 4 mg·kg-1).

Results

The results showed that the bioaccumulation coefficients (Cd content of cotton organs / soil available Cd content) of cotton roots, stems, leaves, and buds/bolls reduced by 15.93%, 14.41%, 23.53%, and 20.68%, respectively after the application of BC, and reduced by 16.83%, 17.15%, 22.21%, and 26.25%, respectively after the application of BF, compared with the control (no BC and BF). Besides, the application of BC and BF reduced the transport of Cd from soil to root system, and enhanced the diversity of soil bacterial communities (dominant species: Alphaproteobacteria and Actinobacteria) and the metabolic functions related to amino acid synthesis. It was worth noting that the differential species for BF group vs BC group including Alphaproteobacteria, Gemmatimonadetes, Bacilli, and Vicinamibacteria were associated with the enrichment and transport of Cd, especially the transport of Cd from cotton roots to stems.

Discussion

Therefore, the application of BC and BF changed the soil bacterial diversity in Cd-polluted cotton field, and then promoted the transport of Cd in cotton, ultimately improving soil quality. This study will provide a reference for the selection of soil heavy metal pollution remediation techniques in Xinjiang, China.

Microbial Catabolic Activity: Methods, Pertinence, and Potential Interest for Improving Microbial Inoculant Efficiency

Microbial catabolic activity (MCA) defined as the degrading activity of microorganisms toward various organic compounds for their growth and energy is commonly used to assess soil microbial function potential. For its measure, several methods are available including multi-substrate-induced respiration (MSIR) measurement which allow to estimate functional diversity using selected carbon substrates targeting specific biochemical pathways. In this review, the techniques used to measure soil MCA are described and compared with respect to their accuracy and practical use. Particularly the efficiency of MSIR-based approaches as soil microbial function indicators was discussed by (i) showing their sensitivity to different agricultural practices including tillage, amendments, and cropping systems and (ii) by investigating their relationship with soil enzyme activities and some soil chemical properties (pH, soil organic carbon, cation exchange capacity). We highlighted the potential of these MSIR-based MCA measurements to improve microbial inoculant composition and to determine their potential effects on soil microbial functions. Finally, we have proposed ideas for improving MCA measurement notably through the use of molecular tools and stable isotope probing which can be combined with classic MSIR methods. Graphical abstract describing the interrelation between the different parts and the concepts developed in the review.

Bio-organic fertilizers improve Dendrocalamus farinosus growth by remolding the soil microbiome and metabolome

Organic and microbial fertilizers have potential advantages over inorganic fertilizers in improving soil fertility and crop yield without harmful side-effects. However, the effects of these bio-organic fertilizers on the soil microbiome and metabolome remain largely unknown, especially in the context of bamboo cultivation. In this study, we cultivated Dendrocalamus farinosus (D. farinosus) plants under five different fertilization conditions: organic fertilizer (OF), Bacillus amyloliquefaciens bio-fertilizer (Ba), Bacillus mucilaginosus Krassilnikov bio-fertilizer (BmK), organic fertilizer plus Bacillus amyloliquefaciens bio-fertilizer (OFBa), and organic fertilizer plus Bacillus mucilaginosus Krassilnikov bio-fertilizer (OFBmK). We conducted 16S rRNA sequencing and liquid chromatography/mass spectrometry (LC-MS) to evaluate the soil bacterial composition and soil metabolic activity in the different treatment groups. The results demonstrate that all the fertilization conditions altered the soil bacterial community composition. Moreover, the combination of organic and microbial fertilizers (i.e., in the OFBa and OFBmK groups) significantly affected the relative abundance of soil bacterial species; the largest number of dominant microbial communities were found in the OFBa group, which were strongly correlated with each other. Additionally, non-targeted metabolomics revealed that the levels of soil lipids and lipid-like molecules, and organic acids and their derivatives, were greatly altered under all treatment conditions. The levels of galactitol, guanine, and deoxycytidine were also markedly decreased in the OFBa and OFBmK groups. Moreover, we constructed a regulatory network to delineated the relationships between bamboo phenotype, soil enzymatic activity, soil differential metabolites, and dominant microbial. The network revealed that bio-organic fertilizers promoted bamboo growth by modifying the soil microbiome and metabolome. Accordingly, we concluded that the use of organic fertilizers, microbial fertilizers, or their combination regulated bacterial composition and soil metabolic processes. These findings provide new insights into how D. farinosus-bacterial interactions are affected by different fertilization regiments, which are directly applicable to the agricultural cultivation of bamboo.

Bacillus and microalgae biofertilizers improved quality and biomass of Salvia miltiorrhiza by altering microbial communities

Objective

Biofertilizers are reliable alternatives to chemical fertilizers due to various advantages. However, the effect of biofertilizers on Salvia miltiorrhiza yield and quality and the possible mechanisms remain little known. Here, an experiment was conducted in S. miltiorrhiza field treated with two kinds of biofertilizers including Bacillus and microalgae.

Methods

A field experiment was conducted on S. miltiorrhiza of one year old. The biofertilizers were applied at six treatments: (i) control check, CK; (ii) microalgae, VZ; (iii) Bacillus, TTB; (iv) microalgae + Bacillus (1:1), VTA; (v) microalgae + Bacillus (0.5:1), VTB; (vi) microalgae + Bacillus (1:0.5), VTC. Here, high-throughput sequencing, ICP-MS and UPLC were employed to systematically characterize changes of microbial diversity and structure composition, heavy metals content and bioactive compounds, respectively.

Results

Compared to CK, root biomass increased by 29.31%-60.39% (P < 0.001). Meanwhile, bioactive compounds were higher than CK after the application of the biofertilizers, peculiarly in TTB and VTB. However, the content of Pb contents in roots significantly reduced by 46.03% and 37.58% respectively in VTC and TTB (P < 0.05). VTA application notably increased the available nitrogen content by 53.03% (P < 0.05), indicating the improvement of soil fertility. Significantly, bacterial and fungal Chao I diversity indices showed an increasing trend with biofertilizer application (P < 0.05), and biofertilizer amendment enriched the rhizosphere soil with beneficial microorganisms that have abilities on promoting plant growth (Achromobacter and Penicillium), adsorbing heavy metal (Achromobacter and Beauveria), controlling plant pathogen (Plectosphaerella, Lechevalieria, Sorangium, Phlebiopsis and Beauveria) and promoting the accumulation of metabolites (Beauveria and Phoma).

Conclusion

Bacillus and microalgae biofertilizers improved the quality and biomass of S. miltiorrhiza by altering microbial communities in soil.

Core rhizosphere microbiome of Panax notoginseng and its associations with belowground biomass and saponin contents

The core rhizosphere microbiome is critical for plant fitness. However, its contribution to the belowground biomass and saponin contents of Panax notoginseng remains unclear. High-throughput sequencing of amplicon and metagenome was performed to obtain the microbiome profiles and functional traits in P. notoginseng rhizosphere across a large spatial scale. We obtained 639 bacterial and 310 fungal core OTUs, which were mainly affected by soil pH and organic matter (OM). The core taxa were grouped into four ecological clusters (i.e. high pH, low pH, high OM and low OM) for sharing similar habitat preferences. Furthermore, structural equation modelling (SEM) and correlation analyses revealed that the diversity and composition of core microbiomes, as well as the metagenome-derived microbial functions, were related to belowground biomass and saponin contents. Key microbial genera related to the two plant indicators were also identified. In short, this study explored the main driving environmental factors of core microbiomes in the P. notoginseng rhizosphere and revealed that the core microbiomes and microbial functions potentially contributed to the belowground biomass and saponin contents of the plant. This work may enhance our understanding of interactions between microbes and perennial plants and improve our ability to manage root microbiota for the sustainable production of herbal medicine.

UPLC-TOF/MS-based metabolomics reveals the chemical changes and in vitro biological effects in fermentation of white ginseng by four probiotics

Microbial fermentation is a useful method for improving the biological activity of Chinese herbal medicine. Herein, we revealed the effects of solid-state fermentation by Lactiplantibacillus plantarum, Bacillus licheniformis, Saccharomyces cerevisiae, Eurotium cristatum and multiple strains on total flavonoid content, total phenol content, as well as antioxidants, α-amylase inhibitory activities and α-glucosidase inhibitory activities in white ginseng (WG). Metabolite differences between non-fermented and fermented WG by different probiotics were comprehensively investigated using ultra-performance liquid chromatography time-of-flight mass spectrometry (UPLC-TOF-MS). Results showed that the total flavonoid content, ferric reducing antioxidant power, scavenging activities of DPPH radical and ABTS radical, α-amylase inhibitory activities and α-glucosidase inhibitory activities of WG were considerably enhanced after processing by solid-state fermentation in all strains. The total phenol content was increased by E. cristatum and B. licheniformis fermentation, but decreased by L. plantarum, S. cerevisiae and multi-strain fermentation. Additionally, E. cristatum exhibited stronger biotransformation activity on WG compared to other strains. Significant differential metabolites were mainly annotated as prenol lipids, carboxylic acids and derivatives, flavonoids, polyphenols, coumarins and derivatives. Correlation analysis further showed that changes of these metabolites were closely related to antioxidant and hypoglycemic effects. Our results confirmed that fermentation of WG by different probiotics has distinct effects on biological activities and metabolite composition, and indicating fermentation as an important novel strategy to promote components and bioactivities of WG.

Study of the effect of bacterial-mediated legume plant growth using bacterial strain Serratia marcescens N1.14 X-45

Soil microorganisms play an indispensable role in plant growth and are widely used to promote plant growth. However, poor microbial strains are homogeneous. The heavy application of chemical fertilizers and pesticides to agricultural soil has adversely affected the soil flora, necessitating the regulation of the soil flora to maintain soil health. In this study, X-45, a highly efficient and phosphorus-dissolving strain of the lysogenic bacterium Serratia marcescens N1.14 was isolated from bare rock slope soil samples from Yueyang Avenue, Hunan Province, China. We observed that microbial strain X-45 could release P from the rocks into solution when the sample rocks were used as the only phosphorus source. Furthermore, we observed that the P content in media increased by 3.08 X compared to the control. After applying X-45 as a bacterial fertilizer, the growth of potted Indigofera pseudotinctoria plants significantly increased, the soil physicochemical properties were significantly improved, and the relative abundance of Bradyrhizobium in the soil increased significantly from 1 to 42%. Besides, Bradyrhizobium became the most dominant genus in the soil. The indirect promotion of another beneficial microorganism by X-45 further revealed the intrinsic mechanism by which X-45 exerted its effect on plant promotion and soil improvement. Using this bacteria, the hypothesis of the superposition effect of legume plant promotion was also confirmed.

Induced oxidative equilibrium damage and reduced toxin synthesis in Fusarium oxysporum f. sp. niveum by secondary metabolites from Bacillus velezensis WB

In this study, the antifungal mechanism of secondary metabolites from the WB strain against Fusarium oxysporum f. sp. niveum (Fon) was investigated. The WB strain induced the accumulation of reactive oxygen species (ROS) in Fon hyphae and caused morphological changes, including surface subsidence and shrinkage deformation. The cell-free supernatants (CFSs) from WB treatment caused a significant increase in superoxide dismutase, catalase, peroxidase and glutathione reductase activities and the contents of soluble protein and malondialdehyde. Additionally, CFSs from WB decreased the fusaric acid concentration in Fon. Transcriptome analysis revealed that the expression of some antioxidant-related genes was upregulated and that the expression of mycotoxin-related genes was downregulated. Four polypeptide compounds from the WB strain, including iturin A, fengycin, surfactin and bacitracin, were identified by UHPLC-ESI-MS/MS analysis and complete genome mining. RT-qPCR and a quantitative analysis confirmed that the presence of Fon induced the expression of polypeptide genes and elevated polypeptide production. The combined minimum inhibitory concentration and quantitative analysis of four polypeptides revealed that iturin A, fengycin, surfactin and bacitracin might be responsible for inhibiting the growth of Fon. In conclusion, secondary metabolites from strain WB exhibited antifungal effects on Fon by triggering oxidative stress and decreasing toxin levels.

Climate-Resilient Microbial Biotechnology: A Perspective on Sustainable Agriculture

We designed this review to describe a compilation of studies to enlighten the concepts of plant–microbe interactions, adopted protocols in smart crop farming, and biodiversity to reaffirm sustainable agriculture. The ever-increasing use of agrochemicals to boost crop production has created health hazards to humans and the environment. Microbes can bring up the hidden strength of plants, augmenting disease resistance and yield, hereafter, crops could be grown without chemicals by harnessing microbes that live in/on plants and soil. This review summarizes an understanding of the functions and importance of indigenous microbial communities; host–microbial and microbial–microbial interactions; simplified experimentally controlled synthetic flora used to perform targeted operations; maintaining the molecular mechanisms; and microbial agent application technology. It also analyzes existing problems and forecasts prospects. The real advancement of microbiome engineering requires a large number of cycles to obtain the necessary ecological principles, precise manipulation of the microbiome, and predictable results. To advance this approach, interdisciplinary collaboration in the areas of experimentation, computation, automation, and applications is required. The road to microbiome engineering seems to be long; however, research and biotechnology provide a promising approach for proceeding with microbial engineering and address persistent social and environmental issues.

Biofertilizers can enhance nitrogen use efficiency of sugarcane

Fertilizers are costly inputs into crop systems. To compensate for inefficiencies and losses from soil, farmers apply on average double the amount of nitrogen (N) fertilizer acquired by crops. We explored if N efficiency improves with biofertilizers formulated with organic waste, mineral N or plant growth-promoting rhizobacteria (PGPR). We compared treatments receiving mineral N fertilizer or biofertilizers at industry-recommended (100%) or lower (60%) N rates at two commercial sugarcane farms. Biofertilizer at the 60% N-rate generated promising results at one farm with significantly higher biomass and sugar yield than the no-N control, which matched the 100% mineral N treatment. This yield difference was accompanied by a shift in microbial diversity and composition. Correlation analysis confirmed that shifts in microbial communities were strongly linked to soil mineral N levels, as well as crop productivity and yield. Microbial co-occurrence networks further revealed that biofertilizer, including treatments with an added PGPR, can enhance bacterial associations, especially in the context of complex fungal networks. Collectively, the results confirm that biofertilizers have quantifiable effects on soil microbial communities in a crop system setting, which underscores the opportunities for biofertilizers to promote N use efficiency and the circular N economy.

Isolation of indole-3-acetic acid-producing Azospirillum brasilense from Vietnamese wet rice: co-immobilization of isolate and microalgae as a sustainable biorefinery

Production of indole-3-acetic acid (IAA) is well documented in various studies for the bacteria that inhabit the rhizosphere of plants, but with roots of wet rice, the outstandings have been not yet elucidated. This study began with the isolation of bacteria type strain Azospirillum sp. and developed the investigation to a screening of their ability in IAA production. This screening conducted a selection of only bacteria that was capable of the production of IAA with its content of over 25µg. mL^-1 for sequencing. Of 10 isolates only one resulted from the type strain Azospirillum brasilense (A. brasilense) with a similarity of 100%. Various factors that influence A. brasilense in biosynthesizing IAA such as temperature, pH, nitrogen presence and concentration of tryptophan in the culture medium were examined. The results indicated that the culture conditions were suitable for IAA biosynthesis at pH 6.5, 30°C, culture media with nitrogen, and 0.1% trytophan. The next survey on the role of the immobilization of this bacteria with microalgae in alginate was highlighted to its support in microalgal growth. With the co-immobilization of bacteria and microalgae, the density of Chlorella vulgaris was significantly increased during 15-day culture, inducing 2.2 times of cell content in culture batch microalgae immobilized A. brasilense higher than that free-bacteria.

Contents of lobetyolin, syringin, and atractylolide III in Codonopsis pilosula are related to dynamic changes of endophytes under drought stress

Background

Codonopsis pilosula, an important medicinal plant, can accumulate certain metabolites under moderate drought stress. Endophytes are involved in the metabolite accumulations within medicinal plants. It is still unknown that the endophytes of C. pilosula are associated with the accumulations of metabolites. This study aims to investigate the promoting effect of endophytes on the accumulations of active substances in C. pilosula under drought stress.

Methods

High–performance liquid chromatography and high–throughput sequencing technology were performed to investigate changes in the contents of secondary metabolite and endophyte abundances of C. pilosula under drought stress, respectively. Spearman’s correlation analysis was further conducted to identify the endophytic biomarkers related to accumulations of pharmacodynamic compounds. Culture-dependent experiments were performed to confirm the functions of endophytes in metabolite accumulations.

Results

The distribution of pharmacological components and diversity and composition of endophytes showed tissue specificity within C. pilosula. The contents of lobetyolin, syringin, and atractylolide III in C. pilosula under drought stress were increased by 8.47%‒86.47%, 28.78%‒230.98%, and 32.17%‒177.86%, respectively, in comparison with those in untreated groups. The Chao 1 and Shannon indices in different parts of drought–stressed C. pilosula increased compared with those in untreated parts. The composition of endophytic communities in drought treatment parts of C. pilosula was different from that in control parts. A total of 226 microbial taxa were identified as potential biomarkers, of which the abundances of 42 taxa were significantly and positively correlated to the pharmacodynamic contents. Culture-dependent experiments confirmed that the contents of lobetyolin and atractylolide III were increased by the application of Epicoccum thailandicum, Filobasidium magnum, and Paraphoma rhaphiolepidis at the rates of 11.12%‒46.02%, and that the content of syringin was increased by Pseudomonas nitroreducens at the rates of 118.61%‒119.36%.

Conclusions

Certain endophytes participated in the accumulations of bioactive metabolites, which provided a scientific evidence for the development and application of microorganisms to improve the quality of traditional Chinese medicine.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13020-021-00533-z.

Microbial inoculants and garbage fermentation liquid reduced root-knot nematode disease and As uptake in Panax quinquefolium cultivation by modulating rhizosphere microbiota community

Objective

To find a suitable ecological cultivation measure to solve the problem of root-knot nematode disease of Panax quinquefolium (Panacis Quinquefolii Radix) and the heavy metals accumulating in its roots.

Methods

Three-year-old P. quinquefolium was treated with four different combinations of microbial inoculant (MI) and garbage fermentation liquid (GFL) [the joint application of ‘TuXiu’ MI and Fifty potassium MI (TF), the combination use of ‘No. 1′ MI and Fifty potassium MI (NF), ‘Gulefeng’ poly-γ-glutamic acid MI (PGA), GFL], and the untreated control (CK). Here, high-throughput sequencing, ICP-MS and UPLC were employed to systematically characterize changes of microbial diversity and structure composition, heavy metals (As, Cd and Pb) content and ginsenoside content among different treatments.

Results

The results revealed that different MIs and GFL could increase the root dry weight of P. quinquefolium, PGA enhanced it by 83.24%, followed by GFL (49.93%), meanwhile, PGA and GFL were able to lessen root-knot nematode disease incidence by 57.25% and 64.35%. The treatment of PGA and GFL can also effectively reduce heavy metals in roots. The As content in GFL and PGA was decreased by 52.17% and 43.48% respectively, while the Cd and Pb contents of GFL and PGA was decreased somewhat. Additionally, the content of total ginsenosides was increased by 42.14% and 42.07%, in response to TF and NF, respectively. Our metagenomic analysis showed that the relative abundance of particular soil microbial community members related to the biocontrol of root-knot nematode disease and plant pathogen (i.e., Chaetomium in NF, Xylari in GFL, and Microascus in PGA), heavy metal bioremediation (Hyphomacrobium in PGA and Xylaria in GFL), and nitrogen fixation (Nordella and Nitrospira in TF) was significantly increased; notably, potential harmful microflora, such as Plectosaphaerella and Rhizobacter, were more abundant in the control group.

Conclusion

MI and GFL could improve the quality of P. quinquefolium by modifying its rhizosphere microbial community structure and composition, both of them are beneficial to the development of ecological cultivation of P. quinquefolium.

Comparative Effect of Fertilization Practices on Soil Microbial Diversity and Activity: An Overview

Continuously increasing human population demands increased food production, which needs greater fertilizer's input in agricultural lands to enhance crop yield. In this respect, different fertilization practices gained acceptance among farmers. We reviewed effect of three main fertilization practices (Conventional-, Organic-, and Bio-fertilization) on soil microbial diversity, activity, and community composition. Studies reported that over application of inorganic fertilizers decline soil pH, change soil osmolarity, cause soil degradation, disturb taxonomic diversity and metabolism of soil microbes and cause accumulation of extra nutrients into the soil such as phosphorous (P) accumulation. On the contrary, organic fertilizers increase organic carbon (OC) input in the soil, which strongly encourage growth of heterotrophic microbes. Organic fertilizer vermicompost application provides readily available nutrients to both plants as well as microbes and encourage overall microbial number in the soil. Most recently, role of beneficial bacteria in long-term sustainable agriculture attracted attention of scientists towards their use as biofertilizer in the soil. Studies documented favorable effect of biofertilization on microbial Shannon, Chao and ACE diversity indices in the soil. It is concluded from intensive review of literature that all the three fertilization practices have their own way to benefit the soil with nutrients, but biofertilization provides long-term sustainability to crop lands. When it is used in integration with organic fertilizers, it makes the soil best for microbial growth and activity and increase microbial diversity, providing nutrients to soil for a longer time, thus improving crop productivity.

Bio-activation of soil with beneficial microbes after soil fumigation reduces soil-borne pathogens and increases tomato yield

Soil-borne diseases have become increasingly problematic for farmers producing crops intensively under protected agriculture. Although soil fumigants are convenient and effective for minimizing the impact of soil-borne disease, they are most often detrimental to beneficial soil microorganisms. Previous research showed that bio-activation of soil using biological control agents present in biofertilizers or organic fertilizers offered promise as a strategy for controlling soil-borne pathogens when the soil was bio-activated after fumigation. Our research sought to determine how bio-activation can selectively inhibit pathogens while promoting the recovery of beneficial microbes. We monitored changes in the soil's physicochemical properties, its microbial community and reductions in soil-borne pathogens. We found that the population density of Fusarium and Phytophthora were significantly reduced and tomato yield was significantly increased when the soil was bio-activated. Soil pH and soil catalase activity were significantly increased, and the soil's microbial community structure was changed, which may have enhanced the soil's ability to reduce Fusarium and Phytophthora. Our results showed that soil microbial diversity and relative abundance of beneficial microorganisms (such as Sphingomonas, Bacillus, Mortierella and Trichoderma) increased shortly after bio-activation of the soil, and were significantly and positively correlated with pathogen suppression. The reduction in pathogens may have been due to a combination of fumigation-fertilizer that reduced pathogens directly, or the indirect effect of an optimized soil microbiome that improved the soil's non-biological factors (such as soil pH, fertility structure), enhanced the soil's functional properties and increased tomato yield.

Multi-Trait Wheat Rhizobacteria from Calcareous Soil with Biocontrol Activity Promote Plant Growth and Mitigate Salinity Stress

Plant growth promoting rhizobacteria (PGPR) can be functional microbial fertilizers and/or biological control agents, contributing to an eco-spirit and safe solution for chemical replacement. Therefore, we have isolated rhizospheric arylsulfatase (ARS)-producing bacteria, belonging to Pseudomonas and Bacillus genus, from durum wheat crop grown on calcareous soil. These isolates harbouring plant growth promoting (PGP) traits were further evaluated in vitro for additional PGP traits, including indole compounds production and biocontrol activity against phytopathogens, limiting the group of multi-trait strains to eight. The selected bacterial strains were further evaluated for PGP attributes associated with biofilm formation, compatibility, salt tolerance ability and effect on plant growth. In vitro studies demonstrated that the multi-trait isolates, Bacillus (1.SG.7, 5.SG.3) and Pseudomonas (2.SG.20, 2.C.19) strains, enhanced the lateral roots abundance and shoots biomass, mitigated salinity stress, suggesting the utility of beneficial ARS-producing bacteria as potential microbial fertilizers. Furthermore, in vitro studies demonstrated that compatible combinations of multi-trait isolates, Bacillus sp. 1.SG.7 in a mixture coupled with 5.SG.3, and 2.C.19 with 5.SG.3 belonging to Bacillus and Pseudomonas, respectively, may enhance plant growth as compared to single inoculants.

Exploring the global research trends in biofertilizers: a bibliometric approach

This research article attempts a bibliometric analysis of global research on biofertilizers carried out from 2000 to 2019. The main purpose of this analysis is in technology foresight; to understand where the research interest lies within the domain of biofertilizer and also to identify the major research networks. The analysis is based on 344 research articles identified using the ISI Web of Science tool, which is processed further using VOSviewer. The results demonstrated that there is an increase in the number of articles, particularly from countries like Brazil, India China, the USA, and Iran. The research focus has been on the assessment of nitrogen fixation capacity of biofertilizers, and the yield improvement due to biofertilizers, and the economics of biofertilizer application. Our findings can act as a useful reference for the researchers, and provide insights for directing future research on biofertilizers.

Health behaviors and metabolic risk factors are associated with dyslipidemia in ethnic Miao Chinese adults: the China multi-ethnic cohort study

BACKGROUND

Cardiovascular risk factors in Chinese ethnic minority groups are rarely reported.

OBJECTIVE

To quantify the cardiovascular risk factors in Miao Chinese adults and to examine the association of health behaviors and metabolic risk factors with dyslipidemia.

METHODS

A cross-sectional analysis was conducted using baseline data from the China Multi-Ethnic Cohort (CMEC) study. A representative sample of 5559 Miao participants aged 30 to 79 years were surveyed and given physical and laboratory exams. The proportion of behavioral and metabolic risk factors were described in ethnic Miao adults. Logistic regression was utilized to evaluate the odds ratio (OR) and 95% confidence interval (CI) of the association between health behaviors and metabolic risk factors with dyslipidemia.

RESULTS

In Miao Chinese adults, the prevalence of dyslipidemia was 32.8%. After multivariate adjustment, subjects with poor waist-to-hip ratio (WHR), body mass index (BMI), fasting blood glucose (FBG) and blood pressure (BP) were more likely to have higher risk of triglycerides (TG) abnormality, regardless of gender and age. Furthermore, the strongly association was detected between poor WHR and low density lipoprotein cholesterol (LDL-C) abnormality (adjusted OR = 5.24, 95%CI: 2.42-11.34) in the older subgroup (≥ 60 years). Males who current smoking were an independent risk factor only for high density lipoprotein cholesterol (HDL-C) abnormality (adjusted OR = 1.44, 95%CI: 1.05-1.99). However, in the subgroup age, current smoker were at greater risk of high TG and low HDL-C. Males with regular drinking were less likely to be high LDL-C (adjusted OR = 0.51, 95%CI: 0.32-0.81).

CONCLUSIONS

The present findings indicated that Miao adults with metabolic risk factors were at greater risk of dyslipidemia.

Streptomyces strains modulate dynamics of soil bacterial communities and their efficacy in disease suppression caused by Phytophthora capsici

The responses of rhizosphere bacterial communities of Streptomyces (SS14 and IT20 stains) treated-pepper plants following inoculation by Phytophthora capsici (PC) was investigated using Illumina MiSeq sequencing. Distinct modulation of the bacteriome composition was found for PC samples with the highest relative abundance (RA) of Chitinophaga (22 ± 0.03%). The RA of several bacterial operational taxonomic units (OTUs) was affected and caused changes in alpha and beta-diversity measures. In IT20, the RA of Cyanobacteria was enriched compared to SS14 (72%) and control samples (47%). Phylotypes belonging to Devosia, Promicromonospora, Kribbella, Microbacterium, Amylocolatopsis, and Pseudomonas genera in the rhizosphere were positively responding against the pathogen. Our findings show that the phosphate solubilizing strain IT20 has higher microbial community responders than the melanin-producing strain SS14. Also, positive interactions were identified by comparing bacterial community profiles between treatments that might allow designing synthetic bio-inoculants to solve agronomic problems in an eco-friendly way.

Comprehensive Quality Evaluation of American Ginseng for Different Parts and Abnormal Trait Based on the Major Ginsenoside Contents and Morphological Characteristics

The demand for American ginseng, a famous traditional medicine and high-grade healthy food, has increased dramatically over recent years. However, only the main root is popular among consumers, whereas other parts of American ginseng are rarely available in the market. In this study, the contents of 5 major ginsenosides (Re, Rc, Rg₁, Rd, and Rb₁) were determined through high-performance liquid chromatography. Our study showed that all these 5 major ginsenosides are found in different parts of American ginseng plants, and the total content in different parts varied significantly in the following order: fibrous root > flower > branch root > main root > leaf > stem. Interestingly, the total content in the fibrous root was approximately 2.24 times higher than that in the main root. Further research indicated that the ginsenoside content in American ginseng with abnormal characteristics (physical deformity caused by disease and discolouration) is similar to that in the normal plant. Interestingly, a positive correlation was observed between the main root diameter and total ginsenoside content, whereas a negative correlation was observed between the main root length and total ginsenoside content. Our comprehensive study revealed that all parts of American ginseng, including the main root with abnormal characteristics, possess medicinal or economic value. Therefore, our results provide feasible evidence to further explore the potential application of American ginseng.

Plant Growth Promoting Rhizobacteria (PGPR) as Green Bioinoculants: Recent Developments, Constraints, and Prospects

The quest for enhancing agricultural yields due to increased pressure on food production has inevitably led to the indiscriminate use of chemical fertilizers and other agrochemicals. Biofertilizers are emerging as a suitable alternative to counteract the adverse environmental impacts exerted by synthetic agrochemicals. Biofertilizers facilitate the overall growth and yield of crops in an eco-friendly manner. They contain living or dormant microbes, which are applied to the soil or used for treating crop seeds. One of the foremost candidates in this respect is rhizobacteria. Plant growth promoting rhizobacteria (PGPR) are an important cluster of beneficial, root-colonizing bacteria thriving in the plant rhizosphere and bulk soil. They exhibit synergistic and antagonistic interactions with the soil microbiota and engage in an array of activities of ecological significance. They promote plant growth by facilitating biotic and abiotic stress tolerance and support the nutrition of host plants. Due to their active growth endorsing activities, PGPRs are considered an eco-friendly alternative to hazardous chemical fertilizers. The use of PGPRs as biofertilizers is a biological approach toward the sustainable intensification of agriculture. However, their application for increasing agricultural yields has several pros and cons. Application of potential biofertilizers that perform well in the laboratory and greenhouse conditions often fails to deliver the expected effects on plant development in field settings. Here we review the different types of PGPR-based biofertilizers, discuss the challenges faced in the widespread adoption of biofertilizers, and deliberate the prospects of using biofertilizers to promote sustainable agriculture.

Composition and function of rhizosphere microbiome of Panax notoginseng with discrepant yields

Background

Panax notoginseng is a highly valuable medicinal plant. Reduced P. notoginseng yield is a common and serious problem that arises in a continuous cropping system. Variation in the composition and function of soil microbial community is considered the primary cause of yield reduction.

Methods

This study used shotgun metagenomic sequencing approaches to describe the taxonomic and functional features of P. notoginseng rhizosphere microbiome and screen microbial taxa and functional traits related to yields.

Results

At the family and genus level, a total of 43 families and 45 genera (relative abundance > 0.1%) were obtained, and the correlation with the yield of P. notoginseng was further analyzed. Nitrosomonadaceae, Xanthomonadaceae, Mycobacterium and Arthrobacter that were enriched in soils with higher yields were positively correlated with P. notoginseng yields, thereby suggesting that they might increase yields. Negative correlation coefficients indicated that Xanthobacteraceae, Caulobacteraceae, Oxalobacteraceae, Chitinophagaceae, Sphingomonas, Hyphomicrobium, Variovorax and Phenylobacterium might be detrimental to P. notoginseng growth. A total of 85 functional traits were significantly (P < 0.05) correlated with P. notoginseng yields. Functional traits, likely steroid biosynthesis and MAPK signaling pathway were positively correlated with P. notoginseng yields. In contrast, functional traits, such as bacterial secretion system, ABC transporters, metabolism of xenobiotics by cytochrome P450 and drug metabolism–cytochrome P450, were negatively associated with yields.

Conclusions

This study describes an overview of the rhizosphere microbiome of P. notoginseng with discrepant yields and identifies the taxa and functional traits related to yields. Our results provide valuable information to guide the isolation and culture of potentially beneficial microorganisms and to utilize the power of the microbiome to increase plant yields in a continuous cropping system.

Control of Fusarium wilt by wheat straw is associated with microbial network changes in watermelon rhizosphere

Straw return is an effective strategy to alleviate soil-borne diseases. Though watermelon Fusarium wilt is a severe soil-borne disease, the effect of wheat straw on the disease remains unclear. Thus, we investigated the effects of wheat straw on soil bacterial and fungal communities by adding wheat straw to consecutive watermelon soil in the greenhouse condition. The microbiome changes were further investigated using network analysis based on 16S rDNA and internal transcribed spacer deep sequencing. Wheat straw addition increased the fungal community diversity, whereas the bacterial diversity was not affected. Compared to the control group, the relative abundance of some bacteria, including Actinobacteria, Chloroflexi, and Saccharibacteria, was increased with wheat straw addition. For fungi, the relative abundance of Fusarium was decreased with wheat straw addition. Microbial network analysis demonstrated that the fungal community has a more complex connection than the bacterial community. In addition, redundancy analysis indicated that the Fusarium genera were significantly related to the disease index. Taken together, the addition of wheat straw might affect the microbial community through increasing the relative abundance of phylum Actinobacteria, decreasing the relative abundance of Fusarium, and increasing the fungal network complexity to enhance the defense of watermelon against Fusarium wilt disease.

Rs-198 Liquid Biofertilizers Affect Microbial Community Diversity and Enzyme Activities and Promote Vitis vinifera L. Growth

Chemical fertilizers were applied on perennial tree vines to obtain high yields, which have resulted in considerable deterioration of soil quality, and it is likely to have negative impacts on the development of the grape industry. In this study, P. putida Rs-198 liquid biofertilizer (Rs198LBF) was inoculated into grape rhizosphere soils to assess its influence on grape growth and microbial community. Field experiment results showed that grape growth and quality increased depending on the concentrations of Rs198LBF applications. The berry weight, length, and width in addition with 60 ml Rs198LBF (1.44 × 10¹³ cfu ml⁻¹ Rs-198) per grapevine treatment (BFP3) were 17.2%, 6.2%, and 4.4% higher than those of CK (control, non-inoculation) treatment, respectively. The available phosphorus contents in addition with 40 ml Rs198LBF per grapevine (BFP2) and BFP3 treatments were 12.6% and 55.3% higher than those of CK treatment (P < 0.05). The activities of invertase and alkaline phosphatase were improved in BFP2 and BFP3 treatment compared with those in CK. The relative abundance of potentially beneficial bacteria significantly increased compared with that in CK treatment (P < 0.05). The clusters of orthologous groups (COG) annotation illustrated that the application of 60 ml Rs198LBF increased the relative abundance of metabolic genes in rhizosphere soil. The results of this study show that biofertilizer is very effective in enhancing plant growth and affects soil community diversity.

A Novel Approach Based on Metabolomics Coupled With Intestinal Flora Analysis and Network Pharmacology to Explain the Mechanisms of Action of Bekhogainsam Decoction in the Improvement of Symptoms of Streptozotocin-Induced Diabetic Nephropathy in Mice

Bekhogainsam decoction (BHID), a representative prescription for the treatment of diabetes mellitus (DM) and diabetic complications in both traditional Korean and Chinese medicine, was examined for its ability to ameliorate diabetic nephropathy (DN), and its mechanism of action was evaluated by metabolomics, gut microbiota, and network pharmacology. In this study, male specific pathogen-free C57BL/6 mice were intraperitoneally injected with streptozotocin (STZ, 100 mg/kg) once per day for 3 days consecutively, and were then orally administered BHID at 100 and 500 mg/kg, and metformin at 250 mg/kg once per day for 4 weeks. Our results showed that the administration of BHID to mice with STZ-induced DN prevented physiological and serological changes, structural damage, and kidney dysfunction. Based on a metabolomics test with serum, the profoundly altered metabolites in the BHID treatment group were identified. Thirty-six BHID-related proteins and four signaling pathways, including valine, leucine, and isoleucine biosynthesis, nicotinate and nicotinamide metabolism, tryptophan metabolism, and alanine, aspartate, and glutamate metabolism pathways, were explored. Principal coordinates analysis (PCoA) of the gut microbiota revealed that BHID treatment significantly affected the flora composition. In addition, the network pharmacology analysis revealed that BHID acted through phosphatidylinositol-3-kinase/protein kinase B (PI3K/Akt) and MAPK-related protein targets. Our findings on the anti-DN effects of BHID and its mechanism of action, from the perspective of systems biology, have provided scientific evidence to support the clinical treatment of patients with diabetes, and implied that BHID has the potential to prevent the progression of DN.