Bacteria In Rhizosphere Soil Research Articles

Differential effects of cow dung and its biochar on Populus euphratica soil phosphorus effectiveness, bacterial community diversity and functional genes for phosphorus conversion.

Continuous monoculture leading to soil nutrient depletion may cause a decline in plantation productivity. Cow dung is typically used as a cheap renewable resource to improve soil nutrient status. In this study, our purpose was to compare the effects of different cow dung return methods (direct return and carbonization return) on soil microbial communities and phosphorus availability in the root zone (rhizosphere soil and non-rhizosphere soil) of P.euphratica seedlings in forest gardens and to explore possible chemical and microbial mechanisms. Field experiments were conducted. Two-year-old P.euphratica seedlings were planted in the soil together with 7.5 t hm-2 of cow dung and biochar made from the same amount of cow dung. Our findings indicated that the available phosphorus content in soil subjected to biochar treatment was considerably greater than that directly treated with cow dung, leading to an increase in the phosphorus level of both aboveground and underground components of P.euphratica seedlings. The content of Olsen-P in rhizosphere and non-rhizosphere soil increased by 134% and 110%, respectively.This was primarily a result of the direct and indirect impact of biochar on soil characteristics. Biochar increased the biodiversity of rhizosphere and non-rhizosphere soil bacteria compared with the direct return of cow dung. The Shannon diversity index of carbonized cow manure returning to field is 1.11 times and 1.10 times of that of direct cow manure returning to field and control, and the Chao1 diversity index is 1.20 times and 1.15 times of that of direct cow manure returning to field and control.Compared to the direct addition of cow dung, the addition of biochar increased the copy number of the phosphorus functional genes phoC and pqqc in the rhizosphere soil. In the biochar treatment, the abundance of the phosphate-solubilizing bacteria Sphingomonas and Lactobacillus was significantly higher than that in the other treatments, it is relative abundance was 4.83% and 2.62%, respectively, which indirectly improved soil phosphorus availability. The results indicated that different cow dung return methods may exert different effects on phosphorus availability in rhizosphere and non-rhizosphere soils via chemical and microbial pathways. These findings indicated that, compared to the direct return of cow dung, biochar return may exert a more significant impact on the availability of phosphorus in both rhizosphere and non-rhizosphere soils, as well as on the growth of P.euphratica seedlings and the microbial community.

Control effect of root exudates from mycorrhizal watermelon seedlings on Fusarium wilt and the bacterial community in continuously cropped soil.

Watermelon (Citrullus lanatus) is susceptible to wilt disease caused by Fusarium oxysporum f. sp niveum (FON). AMF colonization alleviates watermelon wilt and regulates the composition of root exudates, but the effects of mycorrhizal watermelon root exudates on watermelon Fusarium wilt is not well understood. Root exudates of watermelon inoculated with AMF (Funeliformis mosseae or Glomus versiformme) were collected in this study. Then the root exudates of control plants and mycorrhizal plants were used to irrigate watermelon in continuous cropping soil, respectively. Meanwhile, the watermelon growth, antioxidant enzyme activity, rhizosphere soil enzyme activities and bacterial community composition, as well as the control effect on FON were analyzed. The results indicated that mycorrhizal watermelon root exudates promoted the growth of watermelon seedlings and increased soil enzyme activities, actinomyces, and the quantity of bacteria in rhizosphere soil. The proportion of Proteobacteria and Bacteroides was decreased, and the proportion of Actinobacteria, Firmicutes, and Chloroflexi in rhizosphere soil was increased when the seedlings were watered with high concentrations of mycorrhizal root exudates. The dominant bacterial genera in rhizosphere soil were Kaistobacter, Rhodanobacter, Thermomonas, Devosia, and Bacillus. The root exudates of mycorrhizal watermelon could reduce the disease index of Fusarium wilt by 6.7-30%, and five ml/L of watermelon root exudates inoculated with F. mosseae had the strongest inhibitory effect on watermelon Fusarium wilt. Our results suggest mycorrhizal watermelon root exudates changed the composition of bacteria and soil enzyme activities in rhizosphere soil, which increase the resistance of watermelon to Fusarium wilt and promoted the growth of plants in continuous cropping soil.

Soybean (Glycine max) rhizosphere organic phosphorus recycling relies on acid phosphatase activity and specific phosphorus-mineralizing-related bacteria in phosphate deficient acidic soils

Bacteria play critical roles in regulating soil phosphorus (P) cycling. The effects of interactions between crops and soil P-availability on bacterial communities and the feedback regulation of soil P cycling by the bacterial community modifications are poorly understood. Here, six soybean (Glycine max) genotypes with differences in P efficiency were cultivated in acidic soils with long-term sufficient or deficient P-fertilizer treatments. The acid phosphatase (AcP) activities, organic-P concentrations and associated bacterial community compositions were determined in bulk and rhizosphere soils. The results showed that both soybean plant P content and the soil AcP activity were negatively correlated with soil organic-P concentration in P-deficient acidic soils. Soil P-availability affected the α-diversity of bacteria in both bulk and rhizosphere soils. However, soybean had a stronger effect on the bacterial community composition, as reflected by the similar biomarker bacteria in the rhizosphere soils in both P-treatments. The relative abundance of biomarker bacteria Proteobacteria was strongly correlated with soil organic-P concentration and AcP activity in low-P treatments. Further high-throughput sequencing of the phoC gene revealed an obvious shift in Proteobacteria groups between bulk soils and rhizosphere soils, which was emphasized by the higher relative abundances of Cupriavidus and Klebsiella, and lower relative abundance of Xanthomonas in rhizosphere soils. Among them, Cupriavidus was the dominant phoC bacterial genus, and it was negatively correlated with the soil organic-P concentration. These findings suggest that soybean growth relies on organic-P mineralization in P-deficient acidic soils, which might be partially achieved by recruiting specific phoC-harboring bacteria, such as Cupriavidus.

Responses of bulk and rhizosphere soil microbiomes to different cover crop inputs and their connection and contribution to soil fertility and plant growth

Bulk and rhizosphere soil microbiomes may be naturally linked and exhibit unique responses to different cover crop inputs during the early decomposition process. However, their relationship and contribution to soil carbon and nitrogen levels and plant growth during the decomposition process remain unclear. Herein, we performed a pot-based experiment to investigate the interactive effects of cover crops (rye, hairy vetch [HV], and a mixture of rye and HV [mix]) and soil microbial habitats (bulk and rhizosphere soils) on the microbial community. Additionally, we identified the hub taxa and evaluated their contributions to the microbial community, soil fertility, and plant growth. Lettuce was grown in soil exposed to control, rye, HV, or mixed cover crops. Bacterial 16S rRNA) and fungal (ITS) community structures were characterized in bulk and rhizosphere soils of lettuce plants using a DNA-based molecular approach. The results showed that cover crops and soil microbial habitats independently affected microbial community structures; the relative abundances of fungi and bacteria, known as decomposers in bulk soil and plant growth-promoting bacteria in rhizosphere soil, increased. The hub taxa under each treatment represented specific groups that connect bulk and rhizosphere microbiomes. Based on Mantel statistical analysis, hub taxa may maintain the bulk soil microbiome, within which the bacterial community in HV and mix treatments may contribute to the nitrogen supply from cover crop residues. Additionally, the bacterial community in rhizosphere soil in HV and mix treatments may contribute to nitrogen absorption by lettuce plants. These results add to the understanding of the early process of sustainable agriculture using cover crops.

Effects of microbial agent application on the bacterial community in ginger rhizosphere soil under different planting years.

Ginger is one of the important spice crops in the world. Due to the prevalence of ginger wilt disease and the lack of effective prevention and control methods, the planting area, total production and value have declined sharply, which have become a key factor restricting ginger industry development in China. Understanding the influence of microbial agents on the rhizosphere microbiota of ginger will facilitate developing novel technologies for the prevention and control of ginger wilt disease. In the new planting and continuous cropping ginger fields, using large-root ginger and microbial agents, two inoculation levels (inoculation and no inoculation) were designed, and high-throughput sequencing technology was used to study the bacterial community structure in the rhizosphere soil at mature stage of ginger. The results showed that newly planted ginger showed a significant yield advantage over continuous cropping ginger, with a yield increase of 39% to 56%, and the lowest ginger wilt disease index. The community structure at the phylum level of soil bacteria in each treatment was very similar to that in the control, but the abundance of some taxonomic units changed significantly. The four dominant phyla of bacteria in mature ginger rhizosphere soil were Proteobacteria, Actinobacteria, Chloroflexi, and Acidobacteria, accounting for 72.91% to 89.09% of the total. The microbial agent treatment of continuous cropping had beneficial microorganisms such as Acidobacteria and Gemmatimonadetes with abundances increased by 12.2% and 17.1%, respectively, compared to the control. The microbial inoculant treatment of newly planted ginger increased the abundance of Acidobacteria and Gemmatimonadetes by 34.4% and 10.7%, respectively, compared to the control. The composition of bacterial communities were affected by changes in soil properties. Redundancy analysis showed that the hydrolysable nitrogen, available phosphorus, available potassium, and organic matter were significantly related to the composition of soil bacterial communities. Therefore, the microbial agents can not only promote the proliferation of beneficial microorganisms in the continuous cropping soil but also further reshape the soil bacterial community structure by changing the soil physicochemical properties such as effective phosphorus. These results provided a reference for related research on the impact of ginger continuous cropping on soil environment and soil management improvement in ginger fields.

Rhizosphere effects of moso bamboo and dominant tree species of secondary broadleaved forest on soil organic carbon mineralization.

The rhizosphere effect of plants affects soil organic carbon (SOC) mineralization. It is still unclear for the mechanism by which the rhizosphere effect of dominant plants in secondary broadleaved forest habitats invaded by moso bamboo affects SOC mineralization. Taking broadleaved tree species (Quercus glauca and Cunninghamia lanceolata) and moso bamboo, dominating respectively in uninvaded secondary broadleaved forest and bamboo forest formed after the invasion as test materials, we investigated rhizosphere effect of plants on the SOC mineralization in laboratory incubation experiments. The results showed that carbon mineralization rates of Phyllostachys edulis (PE), Quercus glauca (QG) and Cunninghamia lanceolata (CL) rhizosphere soils were 20%, 26%, and 21% higher than bulk soils, respectively. Carbon mineralization of bulk soils of QG and CL was 22% and 26% higher, while that of rhizosphere soils was 14% and 11% higher than PE, respectively. The contents of water-soluble organic carbon and organic carbon in rhizosphere soils of the three species were significantly higher than those of bulk soil, and the abundance of rhizosphere soil bacteria was higher than that of non-rhizosphere. The contents of microbial biomass carbon, water-soluble organic carbon, and total nitrogen were important factors influencing carbon mineralization in rhizosphere, while water-soluble organic carbon and microbial metabolic quotient were important factors influencing carbon mineralization in non-rhizosphere. On the whole, the rhizosphere effect increased total SOC mineralization, driving by changes in microbial biomass carbon, water-soluble organic carbon, and total nitrogen content. The results could provide a theoretical basis for plant-soil interaction on soil carbon cycling in bamboo invasion habitats.

Biological functions of endophytic bacteria in Robinia pseudoacacia 'Hongsen'.

Endophytes and their host plants have co-evolved for a very long time. This relationship has led to the general recognition of endophytes as a particular class of microbial resources. R. pseudoacacia 'Hongsen' is drought- and barren-resistant species that can be grown in both the north and south of China, efficiently addresses the ecological issues caused by China's 'southern eucalyptus and northern poplar. Up to date, cultured-dependent studies are available for the R. pseudoacacia nitrogen-fixing and other endophytes. Therefore, the present research studied the R. pseudoacacia 'Hongsen,' microbiome in detail by high-throughput sequencing and culture dependant. This study examined microbial species and functional diversity in Robinia pseudoacacia 'Hongsen' using culture-dependent (isolation) and culture-independent techniques. A total of 210 isolates were isolated from R. pseudoacacia 'Hongsen.' These isolates were clustered into 16 groups by the In Situ PCR (IS-PCR) fingerprinting patterns. 16S rRNA gene sequence analysis of the representative strain of each group revealed that these groups belonged to 16 species of 8 genera, demonstrating the diversity of endophytes in R. pseudoacacia 'Hongsen'. 'Bacillus is the most prevalent genus among all the endophytic bacteria. High-throughput sequencing of endophytic bacteria from R. pseudoacacia 'Hongsen' of the plant and the rhizosphere soil bacteria showed that the bacterial populations of soil near the root, leaf, and rhizosphere differed significantly. The microbial abundance decreased in the endophytes as compared to the rhizosphere. We observed a similar community structure of roots and leaves. With and without root nodules, Mesorhizobium sp. was significantly different in R. pseudoacacia 'Hongsen' plant. It was predicted that R. pseudoacacia 'Hongsen' plant endophytic bacteria would play a significant role in the metabolic process, such as carbohydrate metabolism, amino acid metabolism, membrane transport, and energy metabolism.

Response of bacterial community characteristics in the rhizosphere soil of Stellera chamaejasme L. to its expansion on the Qinghai‐Tibet Plateau

AbstractQinghai‐Tibet Plateau is facing a serious environmental and ecological problem of Meadow degradation. Toxic weed invasion is a typical characteristic of grassland degradation. Soil microbial community composition is sensitive to environmental changes; however, the effects of poisonous weed expansion on soil bacterial communities are unclear. Here, we investigated the effects of Stellera chamaejasme L. expansion on the rhizosphere soil bacterial community structure and function using high‐throughput sequencing. The results showed that expansion of Stellera chamaejasme L. changed soil nitrogen(e.g., total nitrogen [TN, −39.02%], available nitrogen [AN, −32.95%]) and other soil nutrients. Redundancy analysis (RDA) and Variance partitioning analysis (VPA) showed that soil nutrients changed, leading to significant changes in the bacterial community structure. The expansion of Stellera chamaejasme L significantly reduced its rhizosphere bacterial alpha diversity, and the beta diversity had significant differences (p < 0.05). Principal coordinates analysis (PCoA) and analysis of similarity (ANOSIM) indicated that the expansion caused significant variations in the rhizosphere bacterial community (R = 0.7037, p < 0.01). The linear discriminant analysis (LDA) effect size (LEfSe) analysis identified 23 biomarkers, most of which were Proteobacteria, indicating that bacteria involved in soil nutrient cycling were better able to survive in the alpine grassland. The Biolog EcoPlate method was used to determine the soil microbial metabolic capacity in different S. chamaejasme expansions. The result showed that heavy expansion had higher carbon source usage ability and microbial diversity index values. Furthermore, it was also found that heavy expansion improved the usage rate of amino acid carbon sources. Tax4Fun prediction analysis further indicated that carbohydrate metabolism, amino acid metabolism, and membrane transport were central metabolic pathways of rhizosphere soil bacteria. Our study found that Stellera chamaejasme L. changed rhizosphere soil nutrient and bacterial community structure during expansion and helped it tolerate harsh conditions by enriching bacterial communities actively involved in carbon and nitrogen metabolism and promoting plant growth. These findings provided evidence to propose effective restoration measures for poisonous grassland degradation.

Responses of Phragmites communis and its rhizosphere bacteria to different exposure sequences of molybdenum disulfide and levofloxacin

The effect of the molybdenum disulfide (MoS2)/levofloxacin (LVF) co-exposure was explored on Phragmites communis and rhizosphere soil bacterial communities. The sequence of MoS2/LVF exposure and the different MoS2 dosages (10 mg/kg and 100 mg/kg) contributed to different degrees of effect on the plant after 42 days of exposure. The treatment with priority addition of low dosage MoS2 significantly ameliorated P. communis growth, with root length growing up to 532.22 ± 46.29 cm compared to the sole LVF stress (200.04 ± 29.13 cm). Besides, MoS2 served as an alleviator and reduced the accumulation of reactive oxygen species (ROS) and malondialdehyde (MDA) in P. communis under LVF stress, and activated bacteria in rhizosphere soil. These rhizosphere soil microbes assisted in mitigating toxic pollution in the soil and inducing plant resistance to external stress, such as bacteria genera Bacillus, Microbacterium, Flavihumibacter and altererythrobacter. Potential functional profiling of bacterial community indicated the addition of MoS2 contributed to relieve the reduction in functional genes associated with amino acid metabolism and the debilitation of gram_negative and aerobic phenotypic traits caused by LVF stress. This finding reveals the effect of different exposure sequences of MoS2 nanoparticles and antibiotic for plant-soil systems.

The soft rock can promote the improvement of aeolian sandy soil in Mu Us Sandy Land, China

This study focuses on the significance of improving the land degradation of Mu Us Sandy Land to increase cultivated land area and promote ecological green development. The research objects were four kinds of mixed soils, and rhizosphere soils were collected during the crop harvesting period. The volume ratio of soft rock to sand was 0:1 (control check, CK), 1:5 (composite soil one, PS1), 1:2 (composite soil two, PS2), and 1:1 (composite soil three, PS3). The results showed that the large aggregates were primarily mechanically stable aggregates, while the small aggregates were mainly water-stable aggregates. The soft rock promoted the increase of clay and silt content in sandy soil, and the soil texture changed from sand to loam. The contents of organic matter, available phosphorus, and available potassium increased significantly under PS2 and PS3 treatments, but there was no significant difference between them. Total nitrogen had no significant difference among treatments. Actinobaciota, Proteobateria, and Chloroflexi were the dominant bacteria in rhizosphere soil, accounting for about 75% of all microorganisms. At the Genus level, the soft rock contributes to richer species composition. The diversity index, evenness index, and richness index was higher in PS1, and the available phosphorus and available potassium content promoted the increase of diversity. Therefore, when the proportion of soft rock and sand compound soil is between 1: 5 and 1: 2, it can be used as an important basis and technical parameter for Mu Us Sandy Land improvement.

The rhizosphere soil properties and bacteria community of poplar are affected by magnetic field under salt condition

Magnetic fields (MFs) are konwn to affect plant growth, but their effects on soil conditions remain obscure. In this study, poplar seedlings (Populus×euramericana 'Neva') were subjected to a MF under saline conditions, and the rhizosphere soil properties and bacterial communities were then examined. Salt stress detrimentally influenced rhizosphere soil nutrients availability and bacterial community structure. However, MF treatments showed several positive effects, such as increasing the ammonium nitrogen (NH4+-N), amorphous iron oxide (Feo) and available phosphorus (AP) contents in the soil. Moreover,. soil urease and acid phosphatase activity increased by 59% and 63%, respectively. Meanwhile, MF treatments significantly improved the contents of extracellular polymeric substances (EPS) in rhizosphere soils and increased the relative abundance of dominant bacteria phyla (e.g., Actinobacteria, Gemmatimonadetes, and Proteobacteria). Furthermore, a co-occurrence network analysis revealed greater modular clustering in the MF treatments, however, the network stability did not improve. In conclusion, MFs increased rhizobacterial community modularity and promoted the production of bacterial EPS, these effects that then enhanced soil nutirent availability and poplar salt tolerance.

Apple-marigold intercropping improves soil properties by changing soil metabolomics and bacterial community structures.

Marigold can protect crops against soil-borne diseases. However, the effects of intercropping with marigold on apple rhizosphere soils are not known. In this study, we investigated the metabolite profiles and bacterial community structures in rhizosphere soils of the apple-marigold intercropping system by high-throughput sequencing and soil metabolomics. The results show that intercropping marigold could significantly enhance soil moisture, nitrogen, and enzyme activities compared with clean tillage. The soil metabolite profiles and the soil bacterial community structures in the rhizosphere soils were different between the inter-and mono-cropping systems. Among nine metabolites, carbohydrates were more increased in the intercropping system than in the monocropping system. Pathway enrichment analysis revealed that the greatest differential, in terms of metabolic pathway, was starch and sucrose metabolism. Moreover, intercropping marigold significantly increased the relative abundance of plant growth promoting bacteria in rhizosphere soils, such as Rhizobiales, Pseudomonadales, and Bacillales. These results indicate that marigold intercropping positively affected the apple orchard's soil quality and may provide a new intercropping technique to improve soil fertility in orchards and promote plant growth.

Effects of Rhizophagus intraradices and Acinetobacter calcoaceticus on Soybean Growth and Carbendazim Residue

In agricultural production, carbendazim and other pesticides are used to prevent soybean root rot. However, carbendazim degrades slowly and affects a series of biochemical processes such as soil biological nitrogen fixation and soil nutrient activation in the natural environment. This study mainly investigated the effects of Rhizophagus intraradices, Acinetobacter calcoaceticus, and carbendazim on soybean biomass, the incidence of root rot, the total number of bacterial colonies and phosphorus-solubilizing bacteria in rhizosphere soil, and carbendazim residue in soybean grains and rhizosphere soil. The results showed that the arbuscular mycorrhizal fungi (AMF) spore density, AMF infection rate, soybean biomass, nodule number, total bacterial colonies, and phosphorus-solubilizing bacteria colonies in the soybean rhizosphere soil were the highest in the R. intraradices and A. calcoaceticus treatment groups under natural soil conditions. Moreover, the incidence of root rot and carbendazim residue in soybean grains and rhizosphere soil were the lowest in the R. intraradices and A. calcoaceticus treatment group under natural soil conditions. This result indicated that R. intraradices and A. calcoaceticus can effectively reduce carbendazim residue in soybean grains and rhizosphere soil. This study provided theoretical support for the development of microbial fertilizer and microbial degradation of pesticide residues and improved the practical basis for ensuring food safety.

The response of roots and the rhizosphere environment to integrative cultivation practices in paddy rice

Integrative cultivation practices (ICPs) are essential for enhancing cereal yield and resource use efficiency. However, the effects of ICP on the rhizosphere environment and roots of paddy rice are still poorly understood. In this study, four rice varieties were produced in the field. Each variety was treated with six different cultivation techniques, including zero nitrogen application (0 N), local farmers’ practice (LFP), nitrogen reduction (NR), and three progressive ICP techniques comprised of enhanced fertilizer N practice and increased plant density (ICP1), a treatment similar to ICP1 but with alternate wetting and moderate drying instead of continuous flooding (ICP2), and the same practices as ICP2 with the application of organic fertilizer (ICP3). The ICPs had greater grain production and nitrogen use efficiency than the other three methods. Root length, dry weight, root diameter, activity of root oxidation, root bleeding rate, zeatin and zeatin riboside compositions, and total organic acids in root exudates were elevated with the introduction of the successive cultivation practices. ICPs enhanced nitrate nitrogen, the activities of urease and invertase, and the diversity of microbes (bacteria) in rhizosphere and non-rhizosphere soil, while reducing the ammonium nitrogen content. The nutrient contents (ammonium nitrogen, total nitrogen, total potassium, total phosphorus, nitrate, and available phosphorus) and urease activity in rhizosphere soil were reduced in all treatments in comparison with the non-rhizosphere soil, but the invertase activity and bacterial diversity were greater. The main root morphology and physiology, and the ammonium nitrogen contents in rhizosphere soil at the primary stages were closely correlated with grain yield and internal nitrogen use efficiency. These findings suggest that the coordinated enhancement of the root system and the environment of the rhizosphere under integrative cultivation approaches may lead to higher rice production.

High-Throughput Sequencing Reveals the Effect of the South Root-Knot Nematode on Cucumber Rhizosphere Soil Microbial Community

Due to long-term cultivation in greenhouses, cucumbers are susceptible to root-knot nematode (RKN), resulting in reduced yield and quality. The objective of this study was to investigate the effect of RKN on the rhizosphere microbial community of cucumber. Understanding the composition of rhizosphere bacterial and fungal communities and the possible interaction between microorganisms and RKN is expected to provide a reference for the eco-friendly control of M. incognita in the future. Three different groups were selected for sampling based on the RKN incidence and root galling scale (NHR, 0%, no root galling; NR, 5–15%, root galling scale 1–2; NS, 60–75%, root galling scale 4–5). Soil properties were determined to evaluate the effect of M. incognita on rhizosphere soil. High-throughput sequencing was used to examine the bacterial and fungal communities in rhizosphere soil. The results showed that the contents of soil nutrients and enzyme activities were significantly lower in the NS than in the NHR. The alpha diversity showed that M. incognita had a greater effect on rhizosphere soil bacteria than on fungi. In beta diversity, there were significant differences among the three groups by PCoA (p = 0.001). Furthermore, bacteria and fungi with significant differences in relative abundance were screened at the genus level for a correlation analysis with soil factors, and a correlation analysis between the bacteria and fungi was performed to study their relationships. A redundancy analysis (RDA) of rhizosphere microorganisms and soil properties showed a negative correlation between nematode contamination levels and soil nutrient content. Finally, we predicted the interaction among RKN, soil factors, and the rhizosphere microbial community, which provided evidence for the prevention of RKN via microecological regulation in the future.

The core microbiota as a predictor of soil functional traits promotes soil nutrient cycling and wheat production in dryland farming

Abstract Host plants and the microbiota living in the rhizosphere are interdependent, mutually reinforced and mutually beneficial but the assembly, functions and microbial interactions of the host‐associated microbiota are still unclear. Herein, winter wheat was selected as a test plant to explore the assembly process of total bacteria from bulk soil (BS) and rhizosphere soil (RS), and phoD‐harbouring bacteria in RS at a long‐term (14 years) trial site. We also identified core microbes that are potentially relevant to soil carbon (C), nitrogen (N) and phosphorus (P) cycling genes and soil biogeochemical properties, and investigated the relationships between soil variables, functional genes and wheat productivity. The results showed that the microhabitat of the plant, rather than P fertilizer input, was the main factor affecting the microbial diversity, composition and co‐occurrence networks. The BS bacterial community was driven by deterministic processes but the RS and phoD bacterial communities were dominated by stochastic processes. The influence of deterministic processes decreased with increasing soil nutrient content. A core microbial community consisted of 10 OTUs in different microhabitats and was significantly related to soil functional genes and properties. In the rhizosphere soil, significant correlations were found between soil variables, soil functional bacteria and genes, and crop productivity. Synthesis and applications. This study provides empirical evidence that the assembly process of the microbial community is governed by environmental factors in various soil environments and provides new perspectives on the sustainable improvement of crop productivity. Read the free Plain Language Summary for this article on the Journal blog.

Effects of Microplastic High-density Polyethylene on Cotton Growth, Occurrence of Fusarium wilt, and Rhizosphere Soil Bacterial Community

Plastic mulch, especially polyethylene mulch, is widely used in agricultural production in China, but the microplastics formed by its degradation gradually have accumulated in soil, causing a series of environmental problems. At present, there have been many reports on the environmental biological effects of microplastics in farmland soil, but studies on the effects of microplastics on crop growth, disease occurrence, and rhizosphere soil bacterial communities are still lacking. In the previous study, it was found that 1% high-density polyethylene (HDPE, 500 mesh) could increase the incidence rate of cotton Fusarium wilt (33.3%) and inhibit growth, but this phenomenon was not found after soil sterilization. It was speculated that HDPE could affect the growth and occurrence of Fusarium wilt by regulating the soil microbial community. Therefore, high-throughput sequencing technology, combined with network and FAPROTAX function analysis, were used to investigate the effects of HDPE on the bacterial community structure, interaction network, and soil function in cotton rhizosphere in order to analyze the mechanism of HDPE. NovaSeq sequencing showed that the bacterial community of HDPE-treated cotton rhizosphere soil was composed of 54 phyla and 472 genera; the number of phyla and genera was higher than that in untreated soil. The α and β diversity and ANOSIM/Adonis analyses showed that HDPE significantly reduced the richness of the bacterial community and changed the composition of the community structure. Based on a T-test species difference analysis, HDPE significantly reduced the relative abundance of bacteria with biological control, pollutant degradation, and antifungal drug synthesis (such as Kribbella, Massiliam, Hailiangium, and Ramlibacter).The change in the bacterial community will lead to the change in soil bacterial function. Further analysis of FAPROTAX function revealed that HDPE weakened some biochemical functions of bacteria in the cotton rhizosphere soil, such as aerobic chemoheterotrophy, fermentation, and nitrate reduction. The correlation network at the genus level showed that HDPE treatment weakened the interaction between rhizosphere bacteria, reduced the number of positive correlation connections, increased the number of negative correlation connections, simplified network structure, and changed the key flora. The above results showed that HDPE could reduce the cotton growth and the occurrence of Fusarium wilt by changing the bacterial community, interaction, and functional metabolism in rhizosphere soil, which can provide guidance for evaluating the ecological risk of polyethylene microplastics and the remediation of contaminated soil.

Diversity and Predictive Functional of Caragana jubata Bacterial Community in Rhizosphere and Non-rhizosphere Soil at Different Altitudes

Caragana jubata, as the main dominant plant in the alpine and subalpine regions of northern China, is an important component of the local ecosystem. However, few studies have paid attention to its impact on the soil ecosystem and its response to environmental changes. Thus, in this study, we used high-throughput sequencing technology to investigate diversity and predictive function of rhizosphere and bulk soil bacteria communities of C.jubata from different altitudes. The results indicated that 43 phyla, 112 classes, 251 orders, 324 families, and 542 genera were obtained from the soil. The dominant phyla in all sample sites were Proteobacteria, Acidobacteria, and Actinobacteria. There were significant differences in bacterial diversity index and community structure between the rhizosphere and bulk soil at the same altitude, whereas the differences across altitudes were insignificant. PICRUSt analysis showed that the functional gene families were mainly related to 29 sub-functions, including amino acid metabolism, carbohydrate metabolism, and metabolism of cofactors and vitamins, and the abundance of metabolism was highest. There were significant correlations between the relative abundances of genes involved in the level Ⅱ metabolic pathway of bacteria and phylum-level taxa, such as Proteobacteria, Acidobacteria, and Chloroflexi. The predicted functional compositions of soil bacteria also showed a significantly positive correlation with the dissimilarity in bacterial community structure, indicating that there was a strong relationship between bacterial community structure and functional genes. This study preliminarily discussed the characteristics and functional prediction analysis of bacterial communities in the rhizosphere and bulk soil of C.jubata at different altitudinal gradients, which provided data support for the ecological effects of constructive plants and their responses to environmental changes in high altitude areas.

Effect of Reduced Chemical Fertilizers with Biochar Application on Microbial Community in Rhizosphere Soil of Amorphophallus konjac

In agricultural applications, biochar showed potentials to improve soil properties. At present, effects of chemical fertilizer reduction with biochar application on the microbial community in the rhizosphere soil need to be further investigated. In this study, konjac (Amorphophallus konjac K. Koch) was taken as the research subject, and analyzing the microbial α-diversity, amplicon sequence variants (ASVs) community composition in rhizosphere were analyzed using high-throughput sequencing technology, and tuber yield was calculated. Four treatments of chemical fertilizer with biochar application were set, T1: common fertilizer 20 g/plant, T2: common fertilizer 10 g/plant, T3: controlled-release fertilizers 10 g/plant, T4: controlled-release fertilizers 10 g/plant with biochar 100 g/plant. The results found that, the Chao1 index, number of unique ASVs, and total ASV of rhizosphere soil bacteria in T2 increased by 14.45, 13.39, and 14.36% respectively, compared to T1; while that of fungal abundance decreased by 17.82, 48.28, and 18.42%. Similarly, compared to T3, the Chao1 index, number of unique ASVs, and total ASV in bacterial of rhizosphere soil in T4 increased by 9.36, 19.88, and 9.81%, respectively, while that of fungal abundance decreased by 9.16, 20.18, and 9.62%. The yield of konjac showed no significant difference between T1 and T2 treatments. However, T4 treatment had a significantly higher yield than T3 treatment (P = 0.076), and T4 treatment was significantly higher than T1 treatment (P < 0.05). The results indicated that chemical fertilizer reduction with biochar application can improve bacterial abundance and unique and total ASVs in the rhizosphere soil of konjac, while reducing fungal abundance and unique and total ASVs. This can effectively promote the transformation of the rhizosphere soil towards a high-fertilizer “bacterial type”, leading to an increase in the yield of konjac.

Bacterial Communities Structure and Diversity in Rhizosphere Soil of Dominant Plants in Riparian Wetlands of Reservoir in Zhejiang Province, China

Soil bacterial play special roles in the maintenance and stabilization of wetland ecosystem. To investigate bacterial community structure and diversity in rhizosphere soils of four dominant plants in riparian wetlands of mountain reservoir in Zhejiang province, the V4+V5 areas of 16S rDNA gene of bacteria were sequenced and analyzed by the Illumina HiSeq 2500 high-throughput sequencing technology. The results indicated that 27 phylums, 70 classes, 144 orders, 218 families, and 370 genuses of bacteria were achieved, with Proteobacteria, Acidobacteria,Actinobacteria and Bacteroidetes being the dominant phylum and Gammaproteobacteria, Deltaproteobacteria, Acidobacteria, Actinobacteria, Betaproteobacteria and Thermoleophilia being the main class in the soils of riparian wetlands in this areas. The Shannon index and chao1 index of the rhizosphere soil bacteria of Salix babylonica were 8.64 and 585.58, respectively, which were the highest among the four plants, and that of Pterocarya stenoptera were the lowest, with 7.71 and 289.63, respectively. Soil pH, total nitrogen and organic matter were the main factors affecting the soil bacterial community structure in the soil rhizosphere of four dominant plants species in wetlands of riparian zone of reservoir in Zhejiang province.