Soil Bacterial Diversity Research Articles

The largest single-species Nanozostera japonica seagrass meadow of China: Its decline, restoration attempts, and short-term effects on macrobenthos and soil bacterial communities

Seagrass beds support vital ecological functions so that when seagrass experience severe degradation, their ecosystem service functions are diminished or lost. The largest Nanozostera japonica seagrass bed in China, situated in the Yellow River Delta, has undergone significant degradation due to Spartina alterniflora invasion and the impact of Typhoon Lekima (2019). The lack of seeds and overwintering shoots makes natural seagrass recovery challenging, prompting the urgent need for seagrass ecological restoration. In the present study, seed sowing experiments were conducted with varying burial depths, seed sources, and sowing times, as well as transplantation experiments with different transplant unit sizes and intervals in the severely degraded seagrass bed. Subsequently, changes in macrobenthos and soil bacterial diversity were tracked after seagrass recovery. According to the results, the optimal burial depth for N. japonica seeds varies across different sediment types, with 4 cm being suitable for sandy soil and 2 cm for silty soil. Seeds sown in May did not survive due to high temperatures. Seeds from Dalian exhibited superior growth after sowing, making them ideal material for seed restoration projects. Transplanting N. japonica sods with 25 × 25 cm transplant units and 50-cm intervals resulted in the most robust growth, indicating it as a suitable method for adult transplantation. Following seagrass re-establishment, macrobenthos and soil bacterial diversity increased significantly. The findings of the present study provide valuable technical guidance and theoretical support for the ecological restoration of N. japonica. Future efforts should prioritize the restoration of seagrass bed ecological functions, with longer-term effects examined.

Different responses of soil bacterial community to plant-plant interactions under organic-inorganic fertilizers affect seedling establishment during subalpine forest succession.

Rhizosphere bacterial community as a valuable indicator of soil quality and function, has been widespread studied. However, little knowledge is about the response of bacterial communities to plant-plant interaction and different fertilizers during secondary forest succession. We conducted a field pot experiment applying organic and inorganic fertilizers to monocultures and mixed cultures of dominant plant species from mid- to late-successional stages (Salix oritrepha, Betula albosinensis, and Picea asperata), and investigated the responses of plant growth and rhizosphere bacterial communities. Results indicated that growth rate of plant height varied among plant species, but no significant differences were observed in soil bacterial diversity and composition among plant species or inter-specific interactions under control. Compared to control, inorganic fertilizer resulted in increases in plant growth and the relative abundance of Proteobacteria, Patescibacteria, Bacteroidetes and Gemmatimonadetes, while simultaneously leading to decrease in the relative abundance of Acidobacteria, Actinobacteria, Chloroflexi, Rokubacteria and Planctomycetes. When grown with other species, the bacterial communities in the mixture resembled those of S. oritrepha in singular monoculture under inorganic fertilizer treatment, but plant growth was not affected by interspecific interaction. Unlike inorganic fertilizer, organic fertilizer significantly affected bacterial communities and increased bacterial diversity, but did not alter the effects of plant-plant interactions on bacterial communities. It was also observed that organic fertilizer facilitated later successional species' growth (P. asperata and B. albosinensis) by the mid-successional species (S. oritrepha), ultimately facilitating secondary forest succession. In addition, plants at different successional stages harbor specific bacterial communities to affect their growth, and the bacterial communities contributed more than soil properties to the variations in the plant growth of S. oritrepha and P. asperata though the bacterial communities were regulated by soil factors. This finding highlights the significance of the rhizosphere bacteria on plant growth and plant community succession. It also emphasize the importance of considering both plant-plant interactions and diverse fertilizer types in forest restoration efforts and provide valuable insights into optimizing agronomic practices for secondary forest succession.

Diversity and community distribution of soil bacterial in the Yellow River irrigation area of Ningxia, China.

The bacterial community performs an essential ecological role in maintaining agriculture systems. The roles of bacteria in the forest, marine, and agricultural systems have been studied extensively and intensively. However, similar studies in the areas irrigated by the Yellow River remain limited. In this study, we used Illumina sequencing analysis with the 16S rRNA method to analyze the bacterial diversity, community structure, and influencing factors in soil samples from eight regions of the Yellow River irrigation area in northwestern China. The bacterial community structure and diversity varied among samples from the eight regions. The samples differed significantly in terms of the bacterial community composition. Proteobacteria (approximately 12.4%-55.7%) accounted for the largest proportion and was the dominant bacteria, followed by Actinobacteria (approximately 9.2%-39.7%), Bacteroidetes (approximately 1.8%-21.5%), and Chloroflexi (approximately 2.7%-12.6%). Among the physicochemical variables, the soil pH in the eight regions was mildly alkaline, and the total nitrogen, total phosphorus, and total potassium contents in the soils differed significantly. However, the trend in the variations of the above variables was essentially similar. Soil bacteria in Yongning county had greater Chao1, Shannon-Wiener, and Simpson indices than those in the other regions. Notably, soil moisture, organic matter, and total nitrogen were recognized as the primary factors influencing the bacterial community in the Yellow River irrigation area. Our results revealed the laws of variation in soil bacterial diversity and community composition in the Yellow River irrigation area. Our findings could be beneficial for maintaining sustainable ecological practices in the Yellow River irrigation area.

Biotic Interactions Shape Soil Bacterial Beta Diversity Patterns along an Altitudinal Gradient during Invasion

Invasive plants have already been observed in the understory of mountain forests, which are often considered a safe shelter for most native plants. Microorganisms might be drivers of plant invasions. Nevertheless, the mechanisms determining variations in microbial community composition (beta diversity) during invasion along altitudinal gradients remain to be elucidated. Here, the elevational patterns and the driving ecological processes (e.g., environmental filtering, co-occurrence patterns, and community assembly processes) of soil bacterial beta diversity were compared between invasive and native plants on the Qinling Mountains. The species turnover dominated bacterial compositional dissimilarities in both invasive and native communities, and its contribution to total beta diversity decreased during invasion. Total soil bacterial dissimilarities and turnover exhibited significant binominal patterns over an altitudinal gradient, with a tipping point of 1413 m. Further analysis showed that the contributions of assembly processes decreased in parallel with an increase in contributions of co-occurrence patterns during the invasion process, indicating that species interdependence rather than niche partitioning is strongly correlated with the bacterial biogeography of invasive communities. Plant invasion affects the relative contributions of stochastic processes and co-occurrence interactions through the regulation of the physiochemical characteristics of soil, and ultimately determines compositional dissimilarities and the components of the bacterial community along altitudinal gradients.

Wet-dry or freeze-thaw alternation can regulate the impacts of farmland plastic pollution on soil bacterial communities and functions

The persistence of farmland plastic pollution has raised significant concerns regarding its potential long-term impacts on soil health in the context of global climate change. However, there are still gaps in the understanding of the impacts of plastic residues on soil microbial communities and functions in agricultural environments under unstable and extreme climatic conditions. In this study, the effects of plastic residues (two types and three shapes) on farmland soil bacterial communities and functions across varying environmental conditions were investigated through microscopic experiments. The results revealed that plastic residues subjected to wet-dry or freeze-thaw alternations exhibited greater degradation compared to those under natural conditions. The effects of plastic residue types and shapes on soil bacterial diversity and function were regulated by environmental factors. The plastic residues significantly reduced the stability of the bacterial network under natural condition (P < 0.05), whereas the opposite phenomenon was observed under wet-dry or freeze-thaw alternating conditions. Compared to under natural condition, lower numbers of bacterial functional pathways exhibiting significant differences due to plastic residues were observed under wet-dry or freeze-thaw alternating conditions. Significant associations were observed between soil bacterial communities and functions and various soil physicochemical properties under natural conditions (P < 0.05), and most of these associations were attenuated in the wet-dry or freeze-thaw alternations. This study demonstrated the potential impacts of plastic pollution on farmland soil microbiomes, which could be modulated by both residue characteristics and climatic conditions. Specifically, extreme environments could mitigate plastic-pollution-driven influences on soil microbiomes.

Conversion to Greenhouse Cultivation from Continuous Corn Production Decreases Soil Bacterial Diversity and Alters Community Structure

Changes in crop types and long-term monoculture substantially impact soil microbial communities. Exploring these changes and their influencing factors is of great significance for addressing the challenges posed by continuous cropping. Soil surface layer samples from greenhouse tomatoes fields cultivated for 5 (Y5), 9 (Y9), 13 years (Y13), and a surrounding corn field (CK) as a control were analyzed. The Y13 sample showed a significant increase in the relative abundance of Pseudomonadota (43.1%) and a decrease in Actinobacteria (50.3%) compared to the CK sample. Soil bacterial alpha diversity generally declined from the CK to Y13 (0.1–22.2%) sample, with a small peak in Y9 for Chao1 and Observed_species. Significant differences in Chao1 and Observed_ species were observed between the CK and Y13 samples. Beta diversity analysis revealed a pronounced variation in soil bacterial community structure across planting years, with the divergence from the CK sample intensifying over time. In comparison to the Y5 vs. CK samples, Y9 and Y13 exhibited marked differences from the CK across the same and broader metabolic pathways, suggesting a potential convergence of microbial activities over time. The Y9 and Y13 samples showed significantly higher biosynthesis abundance (7.50% and 6.36%, respectively) than the CK. In terms of soil physicochemical indices, the carbon–nitrogen ratio was the primary factor influencing soil bacterial composition. In conclusion, we found that crop alteration and continued planting changed the soil’s bacterial composition and increasing planting years suppressed the soil’s bacterial diversity, leading to a stable bacterial ecology after nine years. Implementing appropriate measures during this critical period is vital for optimal soil utilization.

Composting of Cow-Dung-Amended Soil by the Dung Beetle Catharsius molossus L. Improves Bacterial Ecological Functions Related to Nitrogen Mineralization and Human and Plant Pathogenesis

The Asian dung beetle (Catharsius molossus L.; Coleoptera: Scarabeidae) has been shown to positively affect soil bacterial diversity and the agronomic features of crop plants. In this study, we used bioinformatic tools to investigate the differences in bacterial functional phenotypes and ecological functions between control soil, cow dung-amended soil (CD), and cow dung-amended soil composted by dung beetles (DB). The soil bacterial metagenomes were sequenced and analyzed with the bioinformatic packages BugBase, PICRUSt2, Tax4Fun, and FAPROTAX to evaluate the effects of dung beetle-mediated composting on bacterial functions such as human and plant pathogenicity, trophic strategies, and soil nutrient transformation. BugBase proved useful for the determination of differences in major functional phenotypes, whereas FAPROTAX was effective at identifying differences in bacterial ecological functions between the treatments. Both tools suggested a relative decrease in human pathogens in the DB soil. This was corroborated by the pairwise comparison of abundances in bacterial species, which showed a significant reduction in the abundance of the broad-host-range pathogen Pseudomonas aeruginosa in the DB soil. In addition, FAPROTAX suggested a decrease in plant pathogens and an increase in chitinolytic bacteria, meaning that the DB treatment might be beneficial to the plant-growth-promoting bacteria involved in biological control. Finally, FAPROTAX revealed an array of ecological functions related to trophic strategies and macro- and micronutrient metabolism. According to these results, the activity of C. molossus beetles enhanced methanotrophy, ammonification, nitrification, sulfate reduction, and manganese oxidation, whereas iron respiration was decreased in the DB-treated soil. Our results represent a collection of general insights into the effects of C. molossus beetles on soil bacterial functions, which also reflect on the nutrient composition of dung beetle-composted soil.

Effects of mixed biocrusts on soil nutrients and bacterial community structure: a case study from Hilly Loess Plateau, China

The ecological function of biological crusts in arid and semi-arid areas is of great importance. Bacteria, as a crucial microbial group in biological crusts, play a key role in the formation, nutrient cycling, and regulation of these crusts. However, the succession of biological crusts and the diversity of bacterial communities, along with key environmental factors in the Loess Plateau’s hilly and gully areas, remain unclear. This study investigated soil bacterial abundance and diversity in bare soil (BS), alga-lichen mixed crust (MC), and alga-lichen mixed crust subsoil (MCS) using high-throughput sequencing methods. It explored the relationship between the bacterial community in biological crusts and key environmental factors. The results indicated that the Chao1, Shannon index, and phylogenetic diversity of bacteria significantly increased with the succession of biological crusts. There were notable differences in the community composition and structure of bacteria at different stages of crust development, with Rubrobacteria and Cyanobacteriia dominating in MCS. Effective phosphorus, available potassium, nitrogen, pH, and total organic carbon were identified as key environmental factors affecting soil bacterial communities. In summary, the succession of biological crusts alters soil physicochemical characteristics and creates different ecological niches for bacterial communities. Soil nutrients and pH play a crucial role in the selection of bacterial species and the shaping of bacterial communities in the Loess Plateau’s hilly and gully areas.

Influence of herbaceous litter thickness on bacterial community structure and physicochemical properties of aeolian sand.

The change and mechanism of soil and soil bacterial diversity during the change of herbaceous litter thickness in desert areas is crucial to understand. In the study, the dominant herbaceous litter mixture in Baijitan National Nature Reserve was selected as the research material, and an experiment was established by adjusting the litter depth. The results showed that the measured values of soil physicochemical factors (total nitrogen, total protein, total potassium, available phosphorus, available potassium, pH, and soil water content) increased with the increase of herbaceous litter mixture thickness in 0-5cm soil layer. Actinobacteria, Proteobacteria, Acidobacteria, Chloroflexi, and Gemmatimonadetes were the dominant bacterial phyla under different thicknesses of herbaceous litter in 0-5 and 5-10cm soil layers. Balneimonas, Rubrobacter, and Geodermatophilus were the dominant bacterial genera under different thicknesses of herbaceous litter in 0-5 and 5-10cm soil layers. There was no obvious change in the α-diversity index of bacterial community the same soil layer, but the α-diversity index in the 0-5cm soil layer was lower compared to the 5-10cm soil layer. The results of this study revealed that the change of herbaceous litter thickness had no significant effect on soil bacterial community structure in desert areas.

Bacillus licheniformisYB06: A Rhizosphere-Genome-Wide Analysis and Plant Growth-Promoting Analysis of a Plant Growth-Promoting Rhizobacterium Isolated from Codonopsis pilosula.

Codonopsis pilosula, commonly known as Dangshen, is a valuable medicinal plant, but its slow growth and susceptibility to environmental stress pose challenges for its cultivation. In pursuit of sustainable agricultural practices to enhance the yield and quality of Dangshen, the present study isolated a bacterial strain exhibiting plant growth-promoting potential from the rhizosphere of C. pilosula. This strain was subsequently identified as Bacillus licheniformisYB06. Assessment of its plant growth-promoting attributes revealed the potential of B. licheniformis YB06 as a biofertilizer. Whole-genome sequencing of B. licheniformis YB06 revealed a genome size of 4,226,888 bp with a GC content of 46.22%, harboring 4325 predicted protein-coding sequences. Genomic analysis of B. licheniformis YB06 revealed a diverse array of genes linked to induced systemic resistance (ISR) and plant growth-promoting (PGP) traits, encompassing phytohormone production, nitrogen assimilation and reduction, siderophore biosynthesis, phosphate solubilization, biofilm formation, synthesis of PGP-related amino acids, and flagellar motility. Seed germination assays demonstrated the positive effects of B. licheniformis YB06 on the germination and growth of C. pilosula seedlings. Furthermore, we explored various fertilization regimes, particularly the B. licheniformis YB06-based biofertilizer, were investigated for their impact on the structure and diversity of the C. pilosula rhizosphere soil bacterial community. Our findings revealed that fertilization significantly impacted soil bacterial composition and diversity, with the combined application of B. licheniformis YB06-based biofertilizer and organic fertilizer exhibiting a particularly pronounced enhancement of rhizosphere bacterial community structure and diversity. This study represents the first report on the beneficial effects of B. licheniformis YB06 on both the growth of C. pilosula and the composition of its rhizosphere soil microbial community. These findings provide a theoretical foundation and practical guidance for the development of novel bio-organic compound fertilizers, thereby contributing to the sustainable cultivation of C. pilosula.

Remediation Mechanism of Chitosan-modified Biochar on Cd-contaminated Farmland Soil and Its Effect on Bacterial Community

To explore the remediation mechanism of chitosan-modified biochar （passivator） on Cd-contaminated farmland soil, pot experiments were conducted to determine the effects of passivator on soil physical and chemical properties, ryegrass biomass, enzyme activity, and the response of soil bacterial diversity and structure. The results showed that when the amount of passivating agent was increased from 0.5% to 3%, the content of available Cd in soil was significantly decreased compared with that in the control, and the above-ground and subsurface biomass of ryegrass was increased by 1.08-1.56 times and 1.00-1.68 times, respectively. The enrichment and running coefficients were reduced by 6.15%-30.00% and 10.42%-31.25%, respectively. The correlation analysis results showed that soil pH, CEC, SOM, AN, AP, and AK were significantly negatively correlated with DTPA-Cd, indicating that the application of a passivating agent promoted the passivation of Cd in soil by changing the physical and chemical properties of soil. High-throughput sequencing results showed that the application of the inactivation agent changed the structure and diversity of the soil bacterial community, which was manifested as a significant decrease in α diversity, significant isolation of bacteria between different treatment groups, and an increase in the relative abundance of beneficial bacteria such as Sphingomonas and Blastococcus. Moreover, the activities of soil urease and cellulase increased, whereas the activities of sucrase and catalase decreased with the addition of a passivator. This study provides a theoretical basis and technical reference for the application of modified biochar in the remediation of Cd-contaminated farmland soil.

Soil pH enhancement and alterations in nutrient and Bacterial Community profiles following Pleioblastus amarus expansion in tea plantations

BackgroundThe expansion of bamboo forests increases environmental heterogeneity in tea plantation ecosystems, affecting soil properties and microbial communities. Understanding these impacts is essential for developing sustainable bamboo management and maintaining ecological balance in tea plantations.MethodsWe studied the effect of the continuous expansion of Pleioblastus amarus into tea plantations, by establishing five plot types: pure P. amarus forest area (BF), P. amarus forest interface area (BA), mixed forest interface area (MA), mixed forest center area (TB), and pure tea plantation area (TF). We conducted a comprehensive analysis of soil chemical properties and utilized Illumina sequencing to profile microbial community composition and diversity, emphasizing their responses to bamboo expansion.Results(1) Bamboo expansion significantly raised soil pH and enhanced levels of organic matter, nitrogen, and phosphorus, particularly noticeable in BA and MA sites. In the TB sites, improvements in soil nutrients were statistically indistinguishable from those in pure tea plantation areas. (2) Continuous bamboo expansion led to significant changes in soil bacterial diversity, especially noticeable between BA and TF sites, while fungal diversity was unaffected. (3) Bamboo expansion substantially altered the composition of less abundant bacterial and fungal communities, which proved more sensitive to changes in soil chemical properties.ConclusionThe expansion of bamboo forests causes significant alterations in soil pH and nutrient characteristics, impacting the diversity and composition of soil bacteria in tea plantations. However, as expansion progresses, its long-term beneficial impact on soil quality in tea plantations appears limited.

Characteristic Analysis of the Soil Bacterial Community Structure of Dendrocalamus brandisii from Seven Geographical Provenances in Yunnan Province

Soil is the basis of bamboo growth and quality formation of bamboo shoots and has an important contribution to the sustainable development of agriculture. To this end, We studied the soil properties and microbial communities of Dendrocalamus brandisii by collecting twenty-one soil samples from its seven typical geographic provenances in Yunnan Province, China. Bacterial 16S rRNA gene amplicons were used to detect soil bacteria and predict bacterial functions using Tax4Fun. The results indicated that the soil bacterial diversity indices (ACE, Chao1, Simpson, and Shannon) were significantly different among different geographical provenances. The dominant bacterial groups at the phylum level in all seven regions were Proteobacteria (19.78~29.06%), Actinobacteria (13.53~30.01%), Chloroflexi (8.03~31.47%), and Acidobacteria (7.12~19.17%), with markedly different constitution proportions. Total phosphorus, available potassium, and pH were the main environmental factors affecting soil bacterial communities. There were significant differences in the secondary metabolic pathways and phenotypes of soil bacterial functions, exhibiting a diversity of functions. The geographical variables of the soil bacterial community in D. brandisii varied with spatial scales. Environmental factors such as available potassium (AK), pH, and total nitrogen (TN) have an impact on soil bacterial communities.

Interactions between Sugarcane Leaf Return and Fertilizer Reduction in Soil Bacterial Network in Southern China Red Soil.

Microbes may play an important role in the sugarcane leaf degradation and nutrient conversion process. Soil bacterial communities are more or less involved in material transformation and nutrient turnover. In order to make better use of the vast sugarcane leaf straw resources and reduce the overuse of chemical fertilizers in the subtropical red soil region of Guangxi, a pot experiment, with three sugarcane leaf return (SLR) amounts [full SLR (FS), 120 g/pot; half SLR (HS), 60 g/pot; and no SLR (NS)] and three fertilizer reduction (FR) levels [full fertilizer (FF), 4.50 g N/pot, 3.00 g P2O5/pot, and 4.50 g K2O/pot; half fertilizer (HF), 2.25 g N/pot, 1.50 g P2O5/pot, and 2.25 g K2O/pot; and no fertilizer (NF)], was conducted to assess the interactions of different SLR amounts and chemical FR levels in the soil bacterial network and the relationship between the soil properties and bacterial network by using Illumina Miseq high-throughput sequencing technology. According to the results of the soil bacterial community compositions and diversity, the soil bacterial network was changed during maize growth. SLR exerted a stronger effect on soil bacterial function than FR. Returning the sugarcane leaf to the field increased the diversity of the soil bacteria network. The bacterial communities were consistently dominated by Acidobacteria, Actinobacteria, and Bacteroidetes across all treatments, among which Actinobacteria was the most abundant bacteria type by almost 50% at the phylum level. The analysis results of the experimental factor on maize growth showed that the effect of SLR was lower than that of FR; however, this was opposite in the soil bacterial community structure and diversity. The soil bacterial network was significantly correlated with the soil total K, available N and organic matter contents, and EC. The soil bacteria community showed different responses to SLR and FR, and the FF in combination with FS partly increased the complexity of the soil bacteria network, which can further benefit crop production and soil health in the red soil region.

Bridging ecological processes to diversity formation and functional profiles in belowground bacterial communities

Revealing the generation and maintenance of biodiversity is a central goal in ecology, but how dispersal, selection, and regional taxon pool size shape soil microbial communities is not well understood. Here, we examined how dispersal and environmental selection affected soil bacterial diversity and their related metabolic functions by leveraging large-scale cross-biome soil surveys of ∼1400 samples from diverse ecosystems across China, including agricultural, forest, grassland, and wetland soils. Our results showed that high dispersal increased α-diversity and decreased β-diversity, whereas strong selection generated the opposite pattern in various ecosystems. This is likely due to dispersal enabling species access to otherwise unreachable habitats, and environmental selection excluding non-adapted species from communities. The α-diversity increased with γ-diversity, whereas β-diversity did not covary. We also showed that bacterial phylotypes positively associated with dispersal and selection exhibited distinct metabolic diversity. Dispersal-induced phylotypes, which were abundant in agricultural soils, exhibited more metabolic diversity in fructose and mannose, starch and sucrose, and nitrogen metabolism. Conversely, selection-induced phylotypes, dominated in wetland soils, were primarily associated with sulfur and methane metabolism. In addition, the complexity of taxon associations increased when communities had higher selection increasing β-diversity. Our study establishes the predictive links of ecological processes to microbial diversity, metabolic functions, and taxon coexistence, thus facilitating a better understanding of the mechanisms underlying biodiversity generation and conservation.

Combined Application Strategy of Biochar/Phosphate Fertilizer Affects the rice Production by Regulating Soil Bacteria Taxa Composition

Phosphate fertilizer affects the rice yield and has a critical role in arable land management. Biochar regulates soil nutrient and soil microbe taxa composition. Our study aimed to elucidate the effects of co-application for biochar-phosphate on soil nutrient indicators, soil microorganisms, and crop production. Our experiment was set up as follows: 0 t/hm2, 28 t/hm2, and 55 t/hm2 biochar application rates with 20 kg/hm2, 40 kg/hm2, and 60 kg/hm2 phosphate fertilizer. The rice yield and soil nutrient indexes were observed and the differences between groups were analyzed based on multiple comparisons. 16S ribosomal DNA sequencing was used to analyze the soil bacteria structure. Redundancy analysis was performed to obtain the correlation relationships between microbial community marker species, soil nutrient indexes, and rice yield. The results showed that a higher application rate of biochar led to a significant alteration in the soil water content, bulk density, alkali-hydrolyzed nitrogen, and available phosphate content. In addition, high concentrations of biochar-phosphate fertilizer application elevated the soil bacterial diversity. Biochar had various effects on the relative abundance of soil bacteria taxa. Our study provided a theoretical basis for exploring efficient fertilization strategies in the rice cultivation industry and shed light on the extensive biochar application in agriculture production.

Impact of Transgenic Maize Ruifeng125 on Diversity and Dynamics of Bacterial Community in Rhizosphere Soil.

With the development of commercialized planting of genetically modified crops, their ecological security risks remain a key topic of public concern. Insect-resistant genetically modified maize, Ruifeng125, which expresses a fusion Bt protein (Cry1Ab-Cry2Aj), has obtained the application safety certificate issued by the Chinese government. To determine the effects of Ruifeng125 on the diversity and dynamics of bacterial communities, the accumulation and degradation pattern of the fusion Bt protein in the rhizosphere soil of transgenic maize were detected. Results showed that the contents of Bt protein varied significantly at different developmental stages, but after straw was returned to the field, over 97% of Bt proteins were degraded quickly at the early stages (≤10 d) and then they were degraded at a relatively slow rate. In addition, the variations in bacterial community diversity in the rhizosphere soil were detected by 16S ribosomal RNA (Rrna) high-throughput sequencing technology. A total of 44 phyla, 435 families, and 842 genera were obtained by 16S rRNA sequencing, among which Proteobacteria, Actinobacia, Acidobacter Acidobacterium, and Chloroflexi were the dominant taxa. At the same developmental stage, no significant differences in soil bacterial diversity were detected between Ruifeng125 and its non-transgenic control variety. Further analysis revealed that developmental stage, rather than the transgenic event, made the greatest contribution to the changes in soil microbial diversity. This research provides important information for evaluating the impacts of Bt crops on the soil microbiome and establishes a theoretical foundation for their environmental safety assessment.

Plateau zokor disturbance enhances soil bacterial diversity and reduces network complexity

Rodent disturbances are considered as the key factors that affect grassland ecological restoration worldwide. Although the impact of rodent disturbances on plant diversity and ecosystem functions has been extensively studied, our understanding of how such activities shape soil bacterial community networks and their functional roles remains limited. In this study, we employed 16S rRNA sequencing to investigate soil bacterial communities between undisturbed alpine meadow and zokor mounds at different successional stages. Additionally, we analyzed the co-occurrence networks and potential functions within the alpine meadow ecosystem. The results revealed that (1) the disturbance by plateau zokors altered the soil bacterial community structure, increased bacterial diversity and reduced network complexity. Also, there were synergistic interactions among key species in the soil bacterial co-occurrence network; (2) soil organic carbon (SOC) and total nitrogen (TN) were identified as the key environmental variables that shape soil bacterial communities; (3) functional predictions based on FAPROTAX indicated that the disturbance by plateau zokors significantly affected the functional groups involved in carbon (C) and nitrogen (N) cycling. Overall, these findings significantly enhance our understanding of how small mammal activities influence the soil nutrient cycling and bacterial community in the Qinghai-Tibet Plateau (QTP) alpine meadow.

Urbanization reduces the stability of soil microbial community by reshaping the diversity and network complexity

Rapid urbanization considerably alters soil environment, biodiversity, and stability of terrestrial ecosystems. Soil microbial community, a key component of global biodiversity, plays a pivotal role in ecosystem stability and is highly vulnerable to urbanization. However, effects of urbanization on the diversity, stability, and network structure of soil microbial community remain poorly understood. Herein, we investigated the diversity and stability of soil microbial communities, including bacteria, fungi, and protists, across three regions with different levels of urbanization—urban, suburb, and ecoregion—using high-throughput sequencing techniques. Our results revealed that urbanization led to a notable decrease in the alpha diversity of soil microbial community, causing a significant reduction in soil stability, as assessed by the average variation degree (AVD). The loss of stability was linked to the diminished alpha diversity of the soil fungal and protistan communities, along with weakened interactions among bacteria, fungi, and protists. Notably, the majority of keystone species identified through network analysis were classified as bacteria (Proteobacteria) and displayed a strong positive correlation with the environmental factors influencing AVD. This highlights that the variability of bacteria and the immutability of fungi and protists are important to sustain soil microbial stability. Furthermore, structural equation models indicated that protistan diversity primarily drove soil microbial stability across all regions studied. In the suburban and ecoregion areas, soil microbial stability was directly influenced by the soil properties, bacterial diversity, and keystone species, as well as indirectly affected by heavy metals. These results underscore how urbanization can reduce the stability of soil microbial community via declined diversity and network complexity, whereas the establishment of ecoregions maybe contribute to preserve the diversity and stability of soil microbial community.

Multiple anthropogenic environmental stressors structure soil bacterial diversity and community network

Microbial communities in many ecosystems are suffering a wide range of environmental stressors induced by anthropogenic perturbations. While the impacts of a single stressor have been extensively estimated in numerous studies, the responses of microbial communities to multiple environmental stressors simultaneously are still poorly understood. In the current study, we investigated the taxonomic diversity, community resistance, and co-occurrence interaction of soil bacterial communities treated with different numbers of environmental stressors by conducting 136 microcosms. We found that the richness and Shannon diversity of the soil community decreased significantly from 1430 to 6.54 in the mono-factor treatments to 920 and 5.77 in the hepta-factor treatments. The counts of nodes and edges of the soil microbial networks decreased with the increasing stressor number, potentially indicating that multiple stressors can reduce the network size. Multiple stressors increased the community resistance potential to environmental disturbance. Additionally, the network cohesion suggested that the cooperative and competitive behaviors between microorganisms were induced by multiple stressors. The observation could be potentially due to the enrichment of the generalists by multiple environmental stressors. Although only a handful of stressors were included, our study still indicated that multiple environmental stressors would lead to diversity loss via deterministic processes.