Diversity Of Bacterial Communities Research Articles

Viral diversity and co-evolutionary dynamics across the ant phylogeny.

Knowledge of viral biodiversity within insects, particularly within ants, is extremely limited with only a few environmental viruses from invasive ant species identified to date. This study documents and explores the viral communities in ants. We comprehensively profile the metagenomes of a phylogenetically broad group of 35 ant species with varied ecological traits and report the discovery of 3710 novel and unique ant-associated viral genomes. These previously unknown viruses discovered within this study constitute over 95% of all currently described ant viruses, significantly increasing our knowledge of the ant virosphere. The identified RNA and DNA viruses fill gaps in insect-associated viral phylogenies and uncover evolutionary histories characterized by both frequent host switching and co-divergence. Many ants also host diverse bacterial communities, and we discovered that approximately one-third of these new ant-associated viruses are bacteriophages. Two ecological categories, bacterial abundance in the host and habitat degradation are both correlated with ant viral diversity and help to structure viral communities within ants. These data demonstrate that the ant virosphere is remarkably diverse phylogenetically and genomically and provide a substantial foundation for studies in virus ecology and evolution within eukaryotes. We highlight the importance of studying insect-associated viruses in natural ecosystems in order to more thoroughly and effectively understand host-microbe evolutionary dynamics.

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.

Prevention and Control of Ginger Blast by Two Fumigants and Their Effects on a Soil Bacterial Community and the Metabolic Components of Ginger

A two-year field trial was conducted in order to assess techniques to control ginger blast and explore the effects of fumigants on soil bacterial microorganisms and ginger metabolites. This study examined the effects of dazomet and chloropicrin on the control of ginger blast and their influence on ginger yield in Luoping County, Yunnan Province, China. The results showed that in 2022, the control effectiveness of dazomet and chloropicrin treatments on ginger blast was 84.33% and 94.67%, respectively. The corresponding yields were 50,154.40 kg/hm2 and 50,296.90 kg/hm2. In 2023, the control effectiveness of dazomet and chloropicrin treatments on ginger blast were 86.33% and 93.67%, respectively, and the yields were 65,115.83 kg/hm2 and 65,337.93 kg/hm2. In both years, the incidence of ginger blast in the control group reached nearly 100%, leading to the near extinction of the crop. Additionally, in 2023, 16S rRNA high-throughput sequencing and non-targeted metabolomics techniques were used to analyze the effects of the fumigants on soil bacterial microorganisms and the metabolites in ginger. The results showed that the diversity and richness of soil bacterial communities were lower than those in the control group at 0 and 120 days after treatment with two fumigants, but the relative abundances of beneficial bacteria such as Pseudomonas increased at 60 days, and the relative abundances of Actinobacteria, Gemmatimonadetes, and Bacillus increased at 120 days. The abundance of Firmicutes also increased after 120 days of chloropicrin treatment. The non-targeted metabolic LC–MS results showed that the production of phenols and terpenoids was upregulated after dazomet and chloropicrin treatments. The contents of amino acids and their derivatives were also upregulated. This upregulation of metabolites was beneficial to the flavor quality of ginger and enhanced its anti-inflammatory, anti-tumoral, and antioxidant effects.

Variation in Bacterial and Fungal Communities in Soils from Three Major Apple Pear (Pyrus bretschneideri Rehd.) Orchards.

Microbial communities are closely related to the overall health and quality of soil, but studies on microbial ecology in apple pear orchard soils are limited. In the current study, 28 soil samples were collected from three apple pear orchards, and the composition and structure of fungal and bacterial communities were investigated by high-throughput sequencing. The molecular ecological network showed that the keystone taxa of bacterial communities were Actinobacteria, Proteobacteria, Gemmatimonadetes, Acidobacteria, Nitrospirae, and Chloroflexi, and the keystone taxon of fungal communities was Ascomycota. Mantel tests showed that soil texture and pH were important factors shaping soil bacterial and fungal communities, and soil water soluble organic carbon (WSOC) and nitrate nitrogen (NO3--N) were also closely related to soil bacterial communities. Canonical correspondence analysis (CCA) and variation partition analysis (VPA) revealed that geographic distance, soil texture, pH, and other soil properties could explain 10.55%, 13.5%, and 19.03% of the overall variation in bacterial communities, and 11.61%, 13.03%, and 20.26% of the overall variation in fungal communities, respectively. The keystone taxa of bacterial and fungal communities in apple pear orchard soils and their strong correlation with soil properties could provide useful clues toward sustainable management of orchards.

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.

Molecular mechanisms of growth promotion and selenium enrichment in tomato plants by novel selenium-doped carbon quantum dots

Selenium (Se)-doped nanoparticles as novel Se fertilizers have a promising potential in the agricultural application. Here, the effects of two novel Se-doped carbon quantum dots (Se-CQDs1 and Se-CQDs2, prepared using co-cracking and adsorption-reduction methods, respectively) on the growth and Se enrichment of tomato plants were studied, where the promoting molecular mechanisms were explored in terms of the related genes expression and soil microbial composition. The results indicated that the soil application of 2.5 mg kg−1 Se-CQDs1 more significantly increased the root growth, plant biomass, and fruit yield than that of Se-CQDs2 and Na2SeO3 treatments (control). Specifically, Se-CQDs1 treatment was more effective to up-regulate the expressions of aquaporin gene (i.e., PIP) and growth hormone synthesis gene (i.e., NIT) than Se-CQDs1 and Na2SeO3 treatments. The expressions of Se methyltransferase gene (smt) and methionine methyltransferase gene (mmt) induced by Se-CQDs1 were 1.45 and 1.18 times higher than that by Se-CQDs2 as well as 1.82 and 2.17 times higher than that by Na2SeO3. Also, Se-CQDs1 more greatly increased the diversity and relative abundance of soil bacterial communities, especially the Actinobacteria phylum, which was beneficial to increase plant growth-promoting substances. These outstanding promoting effects of Se-CQDs1 were mainly ascribed to its higher hydrophilicity and content of the stable doped-Se. The overall results demonstrated that Se-CQDs would be a promising candidate for nano-fertilizer to increase crop growth and development (e.g., tomato plants), where the synthesis modes of Se-CQDs play a critical role in regulating the utilization efficiency of Se.

Soil depth and physicochemical properties influence microbial dynamics in the rhizosphere of two Peruvian superfood trees, cherimoya and lucuma, as shown by PacBio-HiFi sequencing

The characterization of soil microbial communities at different depths is essential to understand their impact on nutrient availability, soil fertility, plant growth and stress tolerance. We analyzed the microbial community at three depths (3 cm, 12 cm, and 30 cm) in the native fruit trees Annona cherimola (cherimoya) and Pouteria lucuma (lucuma), which provide fruits in vitamins, minerals, and antioxidants. We used PacBio-HiFi, a long-read high-throughput sequencing to explore the composition, diversity and putative functionality of rhizosphere bacterial communities at different soil depths. Bacterial diversity, encompassing various phyla, families, and genera, changed with depth. Notable differences were observed in the alpha diversity indices, especially the Shannon index. Beta diversity also varied based on plant type and depth. In cherimoya soils, positive correlations with Total Organic Carbon (TOC) and Cation Exchange Capacity (CEC) were observed, but negative ones with certain cations. In lucuma soils, indices like the Shannon index exhibited negative correlations with several metals and specific soil properties. We proposed that differences between the plant rhizosphere environments may explain the variance in their microbial diversity. This study provides insights into the microbial communities present at different soil depths, highlighting the prevalence of decomposer bacteria. Further research is necessary to elucidate their specific metabolic features and overall impact on crop growth and quality.

Calcium carbonate enhanced As uptake in Pteris vittata by increasing pH and As bioavailability and mediating rhizosphere As-transformation bacterial community

Pteris vittata is the first reported arsenic (As) hyperaccumulator, which is also a calcium (Ca) indicator and adapts to calcareous environment. Therefore, it is hypothesized that Ca plays a role in As accumulation but detail effects and mechanisms are unclear. Typical Ca-compounds (CaCO3, Ca3(PO4)2 and CaSO4) were added to hydroponics. CaCO3 and Ca3(PO4)2 increased pH by 0.75 and 0.31, while CaSO4 decreased it by 0.26. Besides, CaCO3 increased As concentration in P. vittata frond by 25.8 % from 65.4 to 82.3 mg kg–1, while Ca3(PO4)2 and CaSO4 decreased it by 15.1–38.2 % to 40.4–55.5 mg kg–1. So the effect of CaCO3 on soil pH, As bioavailability and As-transformation bacterial community was further examined. In pots, CaCO3 increased soil pH by 0.57 and increased bioavailable As concentration by 6.2 μg kg–1, thereby induced 27.3–28.5 % promotion in As plant accumulation. Rhizosphere bacterial community variance can be explained by soil pH and bioavailable As changes at 49–66 %. P. vittata frond As concentration was negatively correlated with rhizosphere As-transformation bacterial diversity (arrA and arsM) (R=-0.57 and -0.66), and positively correlated with the relative abundance of Geobacter (R=0.66) and Pseudomanas (R=0.48), which mediating As mobilization and transformation. This indicated that CaCO3 can enhance As uptake by P. vittata via increasing soil pH, As bioavailability and mediating As-transformation bacterial community in the rhizosphere. The information helps to better understand how calcareous environment-adaptation benefits P. vittata to uptake and accumulate As. This helps to strategize more efficient processes for As-contaminated soils remediation using the hyperaccumulating plants.

The influence of bioturbator activity on sediment bacterial structure and function is moderated by environment

Bioturbation in coastal sediments plays a crucial role in biogeochemical cycling. However, a key knowledge gap is the extent to which bioturbation influences bacterial community diversity and ecosystem processes, such as nitrogen cycling. This study paired bacterial diversity, bioturbation activity and in situ flux measurements of oxygen and nitrogen from bioturbated sediments at six estuaries along the East coast of Australia. Bacterial community diversity, composition and predicted functional profiles were similar across burrow and surface sediments but were significantly influenced by bioturbator activity (measured as number of burrows) at sites with higher fine grain content. Sediment oxygen demand increased with bioturbator activity but changes in nitrogen cycling (as measured by fluxes and predicted bacterial functional gene analysis) were more spatially variable and were unrelated to bioturbator activity and bacterial community shifts. This study highlights how bioturbator activity influences bacterial community structure and functioning and what implications this has for biogeochemical cycles in estuarine sediments.

Simulation of red mud/phosphogypsum-based artificial soil engineering applications in vegetation restoration and ecological reconstruction

Red mud and phosphogypsum are two of the most typical bulk industrial solid wastes. How they can be efficiently recycled as resources on a large scale and at low costs has always been a global issue that urgently needs to be solved. By constructing a small-scale test site and preparing two types of artificial soils using red mud and phosphogypsum, this study simulated their engineering applications in vegetation restoration and ecological reconstruction. According to the results of this study, the artificial soils contained a series of major elements (e.g. O, Si, Al, Fe, Ca, Na, K, and Mg) similar to those in common natural soil, and preliminarily possessed basic physicochemical properties (pH, moisture, organic matter, and cation exchange capacity), main nutrient conditions (nitrogen, phosphorus and potassium), and biochemical characteristics that could meet the demands of plant growth. A total of 18 different types of adaptable plants (e.g. wood, herbs, flowers, succulents, etc) grew in the test sites, indicating that the artificial soils could be used for vegetation greening and landscaping. The preliminary formation of microbial (fungal and bacterial) community diversity and the gradually enriched arthropod community diversity reflected the constantly improving quality of the artificial soils, suggesting that they could be used for the gradual construction of artificial soil micro-ecosystems. Overall, the artificial soils provided a feasible solution for the large-scale, low-cost, and highly efficient synergistic disposal of red mud and phosphogypsum, with enormous potential for future engineering applications. They are expected to be used for vegetation greening, landscaping, and ecological environment improvement in tailings, collapse, and soil-deficient areas, as well as along municipal roads.

Impact of Seasonal Variation in Pasture on Rumen Microbial Community and Volatile Fatty Acids in Grazing Yaks: Insights from High-Altitude Environments.

The environment is one of the most important factors influencing the variation and diversity of the host gut microbiome in plateau areas. It is well-established that dietary variations substantially alter the rumen microbiota. However, there is limited research on the response of the rumen microbiota of grazing yaks to changes in seasonal diet composition under high-altitude environments. This study investigates the seasonal variations in rumen fermentation parameters, bacterial, and fungal communities in yaks, with a focus on the cold and warm seasons. Quantitative data revealed that in the cold season, yaks had an increased acetic acid proportion (p < 0.05) and acetic acid/propionic acid ratio (p < 0.05) compared to the warm season. The relative abundance of Bacteroidetes and Firmicutes were 64.67% and 25.82% in the cold season, respectively, and 66.77% and 26.87% in the warm season. The fungal community showed a higher abundance of Ascomycetes (58.72% to 76.91%) and Neocallimastigomycota in the cold season. These findings highlight the adaptation mechanisms of yaks to seasonal dietary changes and their implications for optimizing yak husbandry practices.

Combined Application of Chemical and Organic Fertilizers Promoted Soil Carbon Sequestration and Bacterial Community Diversity in Dryland Wheat Fields

Combined Application of Chemical and Organic Fertilizers Promoted Soil Carbon Sequestration and Bacterial Community Diversity in Dryland Wheat Fields

Spatiotemporal distribution of the planktonic microbiome and antibiotic resistance genes in a typical urban river contaminated by macrolide antibiotics

The widespread application of macrolide antibiotics has caused antibiotic resistance pollution, threatening the river ecological health. In this study, five macrolide antibiotics (azithromycin, clarithromycin, roxithromycin, erythromycin, and anhydro erythromycin A) were monitored in the Zao River across three hydrological periods (April, July, and December). Simultaneously, the changes in antibiotic resistance genes (ARGs), mobile genetic elements (MGEs), and planktonic bacterial communities were determined using metagenomic sequencing. A clear pollution gradient was observed for azithromycin and roxithromycin, with the concentrations in the dry season surpassing those in other seasons. The highest concentration was observed for azithromycin (1.36 μg/L). The abundance of MLS resistance genes increased along the Zao River during the dry season, whereas the opposite trend was obtained during the wet season. A significant correlation between the levels of MLS resistance genes and macrolide antibiotics was identified during the dry season. Notably, compared with the reference site, the abundance of transposase in the effluent from wastewater treatment plants (WWTPs) was significantly elevated in both dry and wet seasons, whereas the abundance of insertion sequences (IS) and plasmids declined during the dry season. The exposure to wastewater containing macrolide antibiotics altered the diversity of planktonic bacterial communities. The bacterial host for ARGs appeared to be Pseudomonas, primarily associated with multidrug subtypes. Moreover, the ARG subtypes were highly correlated with MGEs (transposase and istA). The partial least-squares path model (PLS-PM) demonstrated a positive correlation between the abundance of MGEs and ARGs, indicating the significance of horizontal gene transfer (HGT) in the dissemination of ARGs within the Zao River. Environmental variables, such as TN and NO3−-N, were significantly correlated with the abundance of MGEs, ARGs, and bacteria. Collectively, our findings could provide insights into the shift patterns of the microbiome and ARGs across the contamination gradient of AZI and ROX in the river.

Refractory wastewater shapes bacterial assembly and key taxa during long-term acclimatization

Bacterial assembly and key taxa during long-term acclimatization in refractory wastewater treatment systems is of paramount importance for optimizing system performance and improving management strategies. Therefore, this study employed high-throughput sequencing, coupled with machine learning models and statistical analysis approaches, to comprehensively elucidate key features of bacterial communities and assembly processes in pesticide wastewater treatment systems. A nine-month monitoring showed substantial variation in diversity and composition of bacterial community between two interconnected biological treatment units (designated as BA and PA). Dynamics of bacterial communities in both units were similar. Moreover, water quality played crucial roles in regulating the bacterial community structure of activated sludge, which were primarily driven by deterministic patterns. Homogeneous selection contributed to 62.85 % and 64.43 % of the variations in BA and PA samples, respectively. Additionally, network analysis revealed significant modularity in bacterial compositions in both groups. Linear regression analysis identified major bacterial modules associated with metabolism and degradation functions. Notably, Module 2 in PA samples has significant positive correlations with functions related to metabolism of nucleotide, amino acid, and xenobiotics, as well as benzoate degradation. Furthermore, key taxa in ecological modules identified by Random Forest model, such as Pseudomonas, Sphingobium, and PHOS-HE28, were dominant populations with metabolism and degradation functions. Particularly, Sphingobium, appeared to be a potential multifunctional degrading bacterium, related to amino acid and xenobiotics metabolism, as well as fatty acid, valine, leucine, isoleucine, fluorobenzoate, and aminobenzoate degradation. These findings are important for developing operating strategies to maintain stable system performance during refractory wastewater treatment.

Bibacillin 1: A two-component lantibiotic from Bacillus thuringiensis.

Here we describe bibacillin 1 - a two-component lantibiotic from Bacillus thuringiensis. The peptides that comprise bibacillin 1 are modified by a class II lanthipeptide synthetase Bib1M producing two peptides with non-overlapping ring patterns that are reminiscent of cerecidin and the short component of the enterococcal cytolysin (CylLS"), a virulence factor associated with human disease. Stereochemical analysis demonstrated that each component contains LL-methyllanthionine and DL-lanthionine. The mature bibacillin 1 peptides showed cooperative bactericidal activity against Gram-positive bacteria, including members of ESKAPE pathogens, and weak hemolytic activity. Optimal ratio studies suggest that bibacillin 1 works best when the components are present in a 1:1 ratio, but near optimal activity was observed at ratios strongly favouring one component over the other, suggesting that the two peptides may have different but complementary targets. Mechanism of action studies suggest a lipid II-independent killing action distinguishing bibacillin 1 from two other two-component lantibiotics haloduracin and lacticin 3147. One of the two components of bibacillin 1 showed cross reactivity with the cytolysin regulatory system. These result support the involvement of bibacillin 1 in quorum sensing and raise questions about the impact of CylLS"-like natural products on lanthipeptide expression in diverse bacterial communities.

Insights into effects of conventional and biodegradable microplastics on organic carbon decomposition in different soil aggregates

The impacts of microplastics on soil ecological functions such as carbon recycling and soil structure maintenance have been extensively focused. However, the mechanisms underlying the impacts of microplastics on soil carbon transformation and soil microbial community at soil aggregate scale have not been clarified yet. In this work, the effects and action mechanisms of traditional microplastic polypropylene (PP) and degradable microplastic polylactic acid (PLA) on carbon transformation in three sizes of soil aggregates were investigated. The results showed that both PP and PLA promoted CO2 emission, and the effect depended on the type and content of microplastics, and the size of soil aggregates. Changes in soil carbon stocks were mainly driven by changes in organic carbon associated with macroaggregates. For macroaggregates, PP microplastics decreased soil organic carbon (SOC) as well as dissolved organic carbon (DOC). These changes were reversed in microaggregates and silt and clay. Interestingly, PLA increased the SOC, DOC and CO2 emissions in bulk soil and all three aggregates with a dose-effect response. These changes were associated with soil microbes, functional genes and enzymes associated with the degradation of labile and recalcitrant carbon fractions. Furthermore, PP and PLA reduced bacterial community diversities and shifted bacterial community structures in both the three aggregates and in bulk soil. Alterations of functional genes induced by microplastics were the key driving factors of their impacts on carbon transformation in soil aggregates. This research opened up a new insight into the mechanisms underlying the impacts of microplastics on soil carbon transformation, and helped us make rational assessments of the risks and the disturbances of microplastics on soil carbon cycling.

RNA-Seq reveals that Pseudomonas aeruginosa mounts growth medium-dependent competitive responses when sensing diffusible cues from Burkholderia cenocepacia

Most habitats host diverse bacterial communities, offering opportunities for inter-species interactions. While competition might often dominate such interactions, little is known about whether bacteria can sense competitors and mount adequate responses. The competition sensing hypothesis proposes that bacteria can use cues such as nutrient stress and cell damage to prepare for battle. Here, we tested this hypothesis by measuring transcriptome changes in Pseudomonas aeruginosa exposed to the supernatant of its competitor Burkholderia cenocepacia. We found that P. aeruginosa exhibited significant growth-medium-dependent transcriptome changes in response to competition. In an iron-rich medium, P. aeruginosa upregulated genes encoding the type-VI secretion system and the siderophore pyoverdine, whereas genes encoding phenazine toxins and hydrogen cyanide were upregulated under iron-limited conditions. Moreover, general stress response and quorum sensing regulators were upregulated upon supernatant exposure. Altogether, our results reveal nuanced competitive responses of P. aeruginosa when confronted with B. cenocepacia supernatant, integrating both environmental and social cues.

Natural Foraging Selection and Gut Microecology of Two Subterranean Rodents from the Eurasian Steppe in China.

As the most abundant group of mammals, rodents possess a very rich ecotype, which makes them ideal for studying the relationship between diet and host gut microecology. Zokors are specialized herbivorous rodents adapted to living underground. Unlike more generalized herbivorous rodents, they feed on the underground parts of grassland plants. There are two species of the genus Myospalax in the Eurasian steppes in China: one is Myospalax psilurus, which inhabits meadow grasslands and forest edge areas, and the other is M. aspalax, which inhabits typical grassland areas. How are the dietary choices of the two species adapted to long-term subterranean life, and what is the relationship of this diet with gut microbes? Are there unique indicator genera for their gut microbial communities? Relevant factors, such as the ability of both species to degrade cellulose, are not yet clear. In this study, we analyzed the gut bacterial communities and diet compositions of two species of zokors using 16S amplicon technology combined with macro-barcoding technology. We found that the diversity of gut microbial bacterial communities in M. psilurus was significantly higher than that in M. aspalax, and that the two species of zokors possessed different gut bacterial indicator genera. Differences in the feeding habits of the two species of zokors stem from food composition rather than diversity. Based on the results of Mantel analyses, the gut bacterial community of M. aspalax showed a significant positive correlation with the creeping-rooted type food, and there was a complementary relationship between the axis root-type-food- and the rhizome-type-food-dominated (containing bulb types and tuberous root types) food groups. Functional prediction based on KEGG found that M. psilurus possessed a stronger degradation ability in the same cellulose degradation pathway. Neutral modeling results show that the gut flora of the M. psilurus has a wider ecological niche compared to that of the M. aspalax. This provides a new perspective for understanding how rodents living underground in grassland areas respond to changes in food conditions.

Enhanced Soil Fertility and Carbon Sequestration in Urban Green Spaces through the Application of Fe-Modified Biochar Combined with Plant Growth-Promoting Bacteria.

The soil of urban green spaces is severely degraded due to human activities during urbanization, and it is crucial to investigate effective measures that can restore the ecological functions of the soil. This study investigated the effects of plant growth promoting bacteria (Bacillus clausii) and Fe-modified biochar on soil fertility increases and mechanisms of carbon sequestration. Additionally, the effects on C-cycling-related enzyme activity and the bacterial community were also explored. Six treatments included no biochar or Bacillus clausii suspension added (CK), only Bacillus clausii suspension (BC), only biochar (B), only Fe-modified biochar (FeB), biochar combined with Bacillus clausii (BBC), and Fe-modified biochar combined with Bacillus clausii (FeBBC). Compared with other treatments, the FeBBC treatment significantly decreased soil pH, alleviated soil alkalization, and increased the alkali-hydro nitrogen content in the soil. Compared to the individual application of FeB and BC, the FeBBC treatment significantly improved aggregates' stability and positively improved soil fertility and ecological function. Additionally, compared to the individual application of FeB and BC, the soil organic carbon (SOC), particulate organic carbon (POC), and soil inorganic carbon (SIC) contents for the FeBBC-treated soil increased by 28.46~113.52%, 66.99~434.72%, and 7.34~10.04%, respectively. In the FeBBC treatment, FeB can improve soil physicochemical properties and provide bacterial attachment sites, increase the abundance and diversity of bacterial communities, and promote the uniform distribution of carbon-related bacteria in the soil. Compared to a single ecological restoration method, FeBBC treatment can improve soil fertility and carbon sequestration, providing important reference values for urban green space soil ecological restoration.

Specific root length regulated the rhizosphere effect on denitrification across distinct macrophytes

Macrophytes influence nitrogen (N) removal from wetlands. However, the specific plant traits responsible for this effect and the related microbial mechanisms remain largely unknown, especially root traits. In a mesocosm experiment, we determined the rhizosphere effect (RE) on microbial N removal processes by incubating rhizosphere and bulk soils collected from 11 macrophyte species. In addition, we examined root traits (involved in chemistry and morphology), along with examining the diversity, compositions, and abundance of bacterial communities involved in denitrification (nirS and nirK) and anammox (hzsB). Across the 11 macrophyte species, the positive RE on denitrification ranged from 66% to 412%, with an average of 194.72%. RE on denitrification was significantly and positively correlated with the recruitment of nir-type denitrifiers in the rhizosphere. We found that higher specific root length (SRL) root promoted the stronger RE, by increasing the abundance of nir-type denitrifiers and further enhancing N removal. Net N removal from water in the wetlands increased with a higher positive RE on nir-type denitrifiers. In addition, SRL significantly influenced the compositions of denitrifiers in the rhizosphere soil. We further found that the enrichment of Azospira, Bradyrhizobium, Sinorhizobium, Rhodopseudomonas, Alcaligenaceae, Bradyrhizobiaceae, and Pleomorphomonas improved the denitrification rate. These findings highlight the potential of root morphology in regulating plant–microbe interactions, thereby improving water purification.