Changes In Microbial Communities Research Articles

Changes in Soil Microbial Communities Induced by Biodegradable and Polyethylene Mulch Residues Under Three Different Temperatures

Mulching is a common method increasing crop yield and achieving out-of-season production; nevertheless, their removal poses a significant environmental danger. In this scenario, the use of biodegradable plastic mulches comes up as a solution to increase the sustainability of this practice, as they can be tilled in soil without risk for the environment. In this context, it is important to study the microbial response to this practice, considering their direct involvement in plastic biodegradation. This study evaluated the biodegradation of three commercial mulch residues: one conventional non-biodegradable mulch versus two biodegradable ones (white and black compostable Mater-Bi mulches). The experiment was conducted under three incubation temperatures (room temperature 20–25 °C, 30 °C, and 45 °C) for a 6-month trial using fallow agricultural soil. Soil without plastic mulch residues was used as a control. White mater-bi biodegradable mulch residues showed higher degradation rates up to 88.90% at 30 °C, and up to 69.15% at room temperature. Furthermore, incubation at 45 °C determines the absence of degradation for all types of mulch considered. Moreover, bacterial alpha diversity was primarily influenced by plastic type and temperature, while fungal populations were mainly affected by temperature. Beta diversity was impacted by all experimental variables. Predicted functional genes crucial for degrading complex substrates, including those encoding hydrolases, cutinases, cellobiosidases, and lipases, were derived from 16S rRNA gene sequencing data. Cluster analysis based on predicted enzyme-encoding gene abundance revealed two clusters, mainly linked to sampling time. Finally, core microbiome analysis identified dominant bacterial and fungal taxa in various soil-plastic ecosystems during degradation, pinpointing species potentially involved in plastic breakdown. The present study allows an assessment of how different temperatures affect the degradation of mulch residues in soil, providing important insights for different climatic growing zones. It also fills a gap in the literature by directly comparing the effects of biodegradable and polyethylene mulches on soil microbial communities.

Microbial community and dynamic changes of extracellular polymeric substances in relation to plastisphere of disposable surgical masks in natural aquatic environment

Microbial community and dynamic changes of extracellular polymeric substances in relation to plastisphere of disposable surgical masks in natural aquatic environment

Zero-waste biorefining co-products from ultrasonically assisted deep eutectic solvent-pretreated Chlorella biomass: Sustainable production of biodiesel and bio-fertilizer

Microalgal biomass is gaining increasing attention to produce high-value co-products. This study proposes integrating Chlorella microalgal biomass into a zero-waste biorefining system, aiming to produce biodiesel and biofertilizer. It investigates optimal conditions for ultrasound-assisted deep eutectic solvent (DES) pretreatment and lipid recovery to enhance the extraction of lipids. Optimal DES pretreatment was identified as a 1.6:1 acetic acid-to-choline chloride molar ratio, 0.36 g biomass loading, and 2.50 min of pretreatment. Lipid recovery succeeded with a 10-minute extraction time and a 1:3 methanol-to-butanol volume ratio. These conditions yielded biodiesel-quality lipids at 139.52 mg/g microalgal biomass with superior fuel characteristics. The de-oiled microalgal biomass residue exhibited promise as a lettuce biofertilizer, enhancing photosynthetic pigments but potentially reducing yields by 40 %. The study also notes changes in rhizosphere microbial communities, indicating both stimulatory and inhibitory effects on beneficial microbes. This study has the potential to enhance sustainability in energy, agriculture, and the environment.

Microbial Community Changes across Time and Space in a Constructed Wetland.

Constructed wetlands are artificial ecosystems designed to replicate natural wetland processes. Microbial communities play a pivotal role in cycling essential elements, particularly sulfur, which is crucial for trace metal fixation and remobilization in these ecosystems. By their response to their environment, microbial communities act as biological indicators of the wetland performance. To address knowledge gaps pertinent to the changes in trace metal bioavailability in relation to microbial activities in the H-02 constructed wetland, we performed this study to investigate temporal and spatial variations in microbial communities by using molecular biology tools. Quantitative polymerase chain reaction and next generation sequencing techniques were employed to analyze archaeal and bacterial groups associated with sulfur and methane cycling. Alpha diversity indices were used to assess species richness, evenness, and dominance. Results indicated high gene abundance of Desulfuromonas (5.37 × 106 g.cell-1), methane oxidizing bacteria (6.92 × 106 g.cell-1), and methanogenic microorganisms (3.02 × 105 g.cell-1) during cool months. Warm months were marked by sulfate reducing bacteria dominance (3.31 × 106 g.cell-1), potentially due to competitive interactions and environmental conditions, higher temperatures, and lower redox potential. Spatial variability among microbial groups was insignificant, but trends in gene abundance indicated complex factors influencing these groups. Next generation sequencing data demonstrated Firmicutes as the most abundant phylum with over 50% regardless of the season or sampling location. Cool months exhibited higher alpha diversity than warm months. Overall, this study showed that seasonal changes significantly impacted the microbial communities in the H-02 constructed wetland that are associated with the sulfur cycle and eventually trace metal biogeochemistry, revealing two distinct mechanisms of the sulfur cycle between the two main seasons, whereas spatial variability effects were not conclusive.

Impact of high-dose cholecalciferol (vitamin D3) and inulin prebiotic on intestinal and airway microbiota in adults with cystic fibrosis: A 2 × 2 randomized, placebo-controlled, double-blind pilot study

BackgroundCystic fibrosis (CF) is a multi-organ disease caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR). Individuals with CF often have gastrointestinal (GI) dysbiosis due to chronic inflammation and antibiotic use. Previous studies suggested a role for vitamin D in reversing the GI dysbiosis found in CF. ObjectiveTo explore the potential role of a combination of high-dose oral cholecalciferol (vitamin D3) and fermentable dietary fiber, inulin, to impact bacterial composition, richness, and diversity of intestinal and airway microbiota in adults with CF. MethodsThis was a 2 × 2 factorial, double-blinded, placebo-controlled, randomized, pilot clinical trial in which adults with CF received oral cholecalciferol (vitamin D3) (50,000 IU/week) and/or inulin (12 g/day) for 12 weeks. Thus, there were 4 study groups (n = 10 subjects per group); 1) placebo 2) vitamin D3 3) inulin 4) vitamin D3 plus inulin. Stool and sputum samples were collected at baseline (just before) and after the intervention and were analysed using 16S ribosomal RNA gene sequencing for gut and airway microbiota composition. Statistical analyses assessed alpha and beta diversity to evaluate microbial community changes. ResultsOf a total of 254 screened participants, 40 eligible participants were randomized to one of the 4 treatment arms. Participants receiving vitamin D3 plus inulin exhibited greater changes in microbiome indexes in both intestinal and airway relative to those in the other study groups. Specific taxonomic changes supported the potential beneficial influence of this combination to mitigate both intestinal and airway dysbiosis in adults with CF. ConclusionThis pilot study established that the combination of oral vitamin D3 and the prebiotic inulin was well tolerated over 12 weeks in adults with CF and altered gut and airway bacterial communities. Future research appear warranted to define clinical outcomes and the role of microbiota changes therein with this approach.

Polyester Microfibers Exposure Modulates Mytilus galloprovincialis Hemolymph Microbiome.

Microplastic (MP) contamination in the aquatic environment is a cause of concern worldwide since MP can be taken up by different organisms, altering different biological functions. In particular, evidence is accumulating that MP can affect the relationship between the host and its associated microbial communities (the microbiome), with potentially negative health consequences. Synthetic microfibers (MFs) represent one of the main MPs in the marine environment, which can be accumulated by filter-feeding invertebrates, such as bivalves, with consequent negative effects and transfer through the food chain. In the mussel Mytilus galloprovincialis, polyethylene terephthalate (PET) MFs, with a size distribution resembling that of an MF released from textile washing, have been previously shown to induce multiple stress responses. In this work, in the same experimental conditions, the effects of exposure to PET-MF (96 h, 10, and 100 μg/L) on mussel hemolymph microbiome were evaluated by 16S rRNA gene amplification and sequencing. The results show that PET-MF affects the composition of bacterial communities at the phylum, family and genus level, with stronger effects at the lowest concentration tested. The relationship between MF-induced changes in hemolymph microbial communities and responses observed at the whole organism level are discussed.

Comparative effects of ammonium nitrogen on perchlorate degradation performance under heterotrophic condition with different carbon sources

Perchlorate (ClO4-) mainly exists in the form of ammonium perchlorate in industrial production. However, the degradation mechanisms of different concentrations of ammonium nitrogen (NH4+-N) and ClO4- mixed pollutants in the environment are not well understood. This study aims to explore the potential of different types of carbon sources for ClO4- and NH4+-N biodegradation. Experimental results showed that the concentration and type of carbon sources are decisive to simultaneous removal of NH4+-N and ClO4-. Under condition of C(COD)/C(ClO4-) ratio of 21.15 ± 4.40, the simultaneously removal efficiency of ClO4- and NH4+-N in acetate (Ace) was relatively higher than that in methanol (Met). C(NH4+-N)/C(ClO4-) ratio of 9.66 ± 0.51 and C(COD)/C(ClO4-) ratio of 2.51 ± 0.87 promoted ClO4- reduction in glucose-C (Glu-C). However, high concentration of Glu could cause pH decrease (from 7.57 to 4.59), thereby inhibiting ClO4- reduction. High-throughput sequencing results indicated that Proteobacteria and Bacteroidetes have made a major contribution to the simultaneous removal of NH4+-N and ClO4-. They are two representative bacterial phyla for participating in both ClO4- reduction and denitrification. Notably, the abundance of main ClO4- degrading bacteria (such as Proteobacteria, Chloroflexi, and Firmicutes) significantly increased by 528.57 % in Glu-C. It can be inferred that the concentration of carbon source and NH4+-N were the most important factors determining the removal efficiency of ClO4- by influencing changes in the core microbial community. This study will provide new techniques and mechanistic insights for the simultaneous removal of mixed ClO4- and nitrogen pollutants, which can also provide theoretical support for innovation in future biological treatment processes.

Transformation and degradation of tebuconazole and its metabolites in constructed wetlands with arbuscular mycorrhizal fungi colonization

Arbuscular mycorrhizal fungi (AMF) colonization has been used in constructed wetlands (CWs) to enhance treatment performance. However, its role in azole (fungicide) degradation and microbial community changes is not well understood. This study aims to explore the impact of AMF on the degradation of tebuconazole and its metabolites in CWs. Total organic carbon levels were consistently higher with the colonization of AMF (AMF+; 9.63- 16.37 mg/L) compared to without the colonization of AMF (AMF-; 8.79–14.48 mg/L) in CWs. Notably, tebuconazole removal was swift, occurring within one day in both treatments (p = 0.885), with removal efficiencies ranging from 94.10 % to 97.83 %. That's primarily due to rapid substrate absorption at the beginning, while degradation follows with a longer time. Four metabolites were reported in CWs first time: tebuconazole hydroxy, tebuconazole lactone, tebuconazole carboxy acid, and tebuconazole dechloro. AMF decreased the abundance of tebuconazole dechloro in the liquid phase, suggesting an inhibitory effect of AMF on dechlorination processes. Furthermore, tebuconazole carboxy acid and hydroxy were predominantly found in plant roots, with a higher abundance observed in AMF+ treatments. Metagenomic analysis highlighted an increasing abundance in bacterial community structure in favor of beneficial microorganisms (xanthomonadales, xanthomonadaceae, and lysobacter), along with a notable presence of functional genes like codA, NAD, and deaD in AMF+ treatments. These findings highlight the positive influence of AMF on tebuconazole stress resilience, microbial community modification, and the enhancement of bioremediation capabilities in CWs.

Catalytic enhancement of microbial denitrification by FeVO4@biochar: Insight into the extra cellular polymeric matrix mechanism

The biological denitrification is being considered as one of the best methods for nitrate removal from wastewaters, however it suffers with lower efficiency which needs to be improved effectively. The present study was aimed to prepare FeVO4@biochar and investigated its role as electron shuttle in enhancing the biological denitrification through various batch experiments. Significantly higher rates of denitrification were observed after addition of FeVO4@biochar in different concentrations and the highest efficiency was observed in 15 wt% FeVO4@biochar (BF-15) where 87.6 % denitrification was achieved after 7 days (from 100 mg/L to 12.7 mg/L of nitrate) compared to pure biochar (65.7 mg/L; 34.3 %) and sludge (72.7 mg/L; 27.3 %). FeVO4@biochar increased the transfer of external electron to bacteria and enhanced the denitrification activity. The variations in NAR (nitrate reductase), NIR (nitrite reductase) and ETSA (electron transport system activity) were investigated to understand the changes in microbial-community during denitrification. The FeVO4@biochar and extracellular polymeric substance (EPS) both acted as the media for electron transport along with the decreased repulsions between nitrate and the catalyst surface that further provides higher nitrate reduction efficiency. The electroactive bacteria could easily utilize the photogenerated electrons from FeVO4@biochar and facilitate excellent denitrification. The microbial-diversity analysis revealed Bacteroidota, Firmicutes, Proteobacteria, Chloroflexi, Desulfobacterota, Acidobacteriota, Actinobacteriota, and Gemmatimonadota were observed as the most predominant phyla actively participated in enhanced denitrification. This study suggested that the addition of photoactive catalyst strongly enhanced the electron transfer during denitrification and provides new ideas to the biological denitrification

Eutrophication driven macrophyte-derived organic matter decomposition to methane emission relates to co-metabolism effect in freshwater sediments

Lakes and wetlands play pivotal roles in global organic matter storage, receiving significant inputs of organic material. However, the co-metabolic processes governing the decomposition of these organic materials and their impact on greenhouse gas emissions remain inadequately understood. This study aims to assess the effects of mixed decomposition involving macrophytes and cyanobacteria on carbon emissions. A series of microcosms was established to investigate the decomposition of macrophyte residues and algae over a period of 216 days. A two-component kinetic model was utilized to estimate methane (CH4) production rates. Gas isotope technology was employed to discern the contributions of CH4 produced by macrophyte residues or algae. Quantitative PCR and analysis of 16S rRNA gene amplicons were employed to assess changes in functional genes and microbial communities. There were significant differences in the cumulative carbon release from the decomposition of different plant types due to the addition of carbon sources. After adding algae, the cumulative emission of CH4 increased significantly. The δ13C–CH4 partitioning indicated that CH4 originated exclusively from the fresh organic carbon of macrophyte residues, while it shifted to algae source after adding algae. The synergistic effect of the mixed decomposition on the CH4 emissions was greater than the sum of the individual decompositions. The microbial community richness was higher in the single plant residue treatment compared to the mixed treatment with algae addition, while microbial evenness in the sediment increased steadily in each treatment. Our findings emphasize the pronounced co-metabolic effect observed during the mixed decomposition of macrophytes and cyanobacteria.

Effects of FeSO4 and Organic Additives on Soil Properties and Microbiota during Model Soybean Planting in Saline-Alkali Soil

Saline soils are characterized by organic matter and nutrient deficiencies, and their mineral fraction consists almost exclusively of fine sand particles, resulting in an unstable soil formation process. Due to the high amount of soluble salts in the soil, the osmotic pressure of the soil is elevated, restricting water absorption. This ultimately leads to the death of the plant and adversely impacts crop growth and yield. Incorporating Fe2+ can improve fertilizer utilization efficiency by reducing the oxidation of NH4+ to nitrogen (N2). However, reports on the usage of iron addition for the improvement of saline-alkali soils are scanty. This study conducted an outdoor simulation in pots to assess the soils of soybean crops during the podding stage. The effects of Fe2+ along with organic fertilizer or bio-C addition were elucidated on the composition and function of saline and alkaline microbial communities. The findings were correlated with soil environmental factors to analyze the dynamic changes in soil microbial communities. The soil pH decreased by 1.22–2.18% and SOM increased by 2.87–11.77% with organic fertilizer (OF) treatment. Compared to the ck treatment (control without iron supplementation), other treatments showed an average increase in abundance of dominant phylum by 8.25–11.23%, and an increase in the diversity and richness of the microbial community by 1.73–10.87%. The harmful bacteria in the Actinobacteriota, Chloroflexi, and Basidiomycota groups reduced by 57.83%, 74.29%, and 67.29%, and the beneficial bacteria in Ascomycota increased by 18.23–20.39%. Fe2+ combined with organic fertilizer or bio-C treatment could weaken the competitive relationship between the various bacterial lineages, enhance synergistic ability, favor the function and structure of the microbial community, and thus, improve the soil environment. Overall, the application of Fe2+ combined with organic fertilizers improved the saline-alkali soil, while the biochar (C) treatment mainly affected the soil nutrients. Through its detailed analysis, the study provides actionable insights for farmers to manage soil fertility in saline-alkaline soils, thereby overcoming the challenges of poor yields due to salinity stress. This will lead to resilient and sustainable farming systems, contributing to global food security.

Medicinal Plant Root Exudate Metabolites Shape the Rhizosphere Microbiota.

The interactions between plants and rhizosphere microbes mediated by plant root exudates are increasingly being investigated. The root-derived metabolites of medicinal plants are relatively diverse and have unique characteristics. However, whether medicinal plants influence their rhizosphere microbial community remains unknown. How medicinal plant species drive rhizosphere microbial community changes should be clarified. In this study involving high-throughput sequencing of rhizosphere microbes and an analysis of root exudates using a gas chromatograph coupled with a time-of-flight mass spectrometer, we revealed that the root exudate metabolites and microorganisms differed among the rhizosphere soils of five medicinal plants. Moreover, the results of a correlation analysis indicated that bacterial and fungal profiles in the rhizosphere soils of the five medicinal plants were extremely significantly or significantly affected by 10 root-associated metabolites. Furthermore, among the 10 root exudate metabolites, two (carvone and zymosterol) had opposite effects on rhizosphere bacteria and fungi. Our study findings suggest that plant-derived exudates modulate changes to rhizosphere microbial communities.

Gut microbial comminoty in Tenebrio molitor larvae responsed to PS and PE within 6 hours

Gut microbes of Tenebrio molitor larvae are crucial in plastic degradation. However, microbial responses to the plastic feeding remains unclear. This study aimed to analyze the changes of microbial community and function feeding PE and PS. It found that after 72 h, the larvae survival rate was 92.2% and 82.2% and the plastic weight loss (consumption rate) was 8.8% (0.44 g, p < 0.01) and 6.9% (0.09 g) for PS and PE, respectively. More interestingly, plastic structure changes and the relative microbial responses happened after 6 h. CO and C–O stretching, hydrogen bonding, and a significant decrease in [Mn] (p < 0.05) and [MW] (p < 0.001) were found; Furthermore, the time-similar microbial diversity obviously clustered and the composition significantly changed. The dominant phylum were Firmicutes and Proteobacteria. At genus level, the dominant PS-degrading taxa were unclassified Enterobacteriaceae, Acinetobacter and Sediminibacterium, and were unclassified Enterobacteriaceae, Acinetobacter and Delftia in PE samples; Additionally, difference of carbohydrate metabolism was found, and plastic degrading gene S-formyl glutathione hydrolase significantly high-expressed (PS-3500 fold and PE-5 fold); Moreover, PS-degrading pathways, such as styrene, benzoate, ethylbenzene and xylene degradation pathways were identified. Those illustrated the plastic degrading occurred just within 6 h and the plastic chemistry determined its’ degradability.

Sargassum mcclurei Mitigating Methane Emissions and Affecting Rumen Microbial Community in In Vitro Rumen Fermentation.

Methane emissions from ruminants significantly contribute to greenhouse gases. This study explores the methane mitigation effect and mechanism of S. mcclurei through in vitro rumen fermentation, aiming to establish its potential as a feed additive. We investigated the effects of freeze-dried and dried S. mcclurei at supplementation levels of 2%, 5%, and 10% of dry matter on nutrient degradation, ruminal fermentation, methane inhibition, and microbial community structure in in vitro rumen fermentation. The freeze-dried S. mcclurei at 2% supplementation significantly reduced CH4 emissions by 18.85% and enhanced crude protein degradability. However, total VFA and acetate concentrations were lower in both treatments compared to the control. The microbial shifts included a decrease in Lachnospiraceae_NK3A20_group and Ruminococcus and an increase in Selenomonas, Succinivibrio, and Saccharofermentans, promoting propionate production. Additionally, a significant reduction in Methanomicrobium was observed, indicating direct methane mitigation. Freeze-dried S. mcclurei at a 2% supplementation level shows potential as an effective methane mitigation strategy with minimal impact on rumen fermentation, supported by detailed insights into microbial community changes.

Analysis of Microbial Community Changes and Their Correlations with Volatile Flavouring Substances during Autonomous Fermentation of Western Sichuan Yi Suancai Based on High-Throughput Sequencing

Analysis of Microbial Community Changes and Their Correlations with Volatile Flavouring Substances during Autonomous Fermentation of Western Sichuan Yi Suancai Based on High-Throughput Sequencing

A 16S RNA Analysis of Yangzhou Geese with Varying Body Weights: Gut Microbial Difference and Its Correlation with Body Weight Parameters.

China is a major goose-raising country, and the geese industry plays a significant role in animal husbandry. Therefore, goose growth performance (body weight) is a critical topic. Goose gut microbiota influences weight gain by regulating its energy metabolism and digestion. Additionally, the impact of cecal microbial community structure on goose growth and development, energy metabolism, and immunity has been examined. However, most studies have used different additives or feeds as variables. Improving the understanding of the dynamic changes in gut microbial communities in geese of different body weights during their growth and development and their correlation with the host's body weight is necessary. In this study, the cecal microbiota of healthy Yangzhou geese with large (L) and small (S) body weights, all at the same age (70 days old) and under the same feeding conditions, were sequenced using 16S rRNA. The sequencing results were annotated using QIIME2 (classify-sklearn algorithm) software, and the linkET package was used to explore the correlation between intestinal microorganisms and the body weight of the Yangzhou goose (Spearman). At the phylum level, the Firmicutes/Bacteroidetes ratio in the large body weight group was approximately 20% higher than that in the small body weight group, with Bacteroidetes and Firmicutes exhibiting a highly significant negative correlation. At the genus level, Bacteroides constituted the most abundant microbial group in both groups, although the Prevotellaceae_Ga6A1_group exhibited a higher abundance in the large than the small weight group. Spearman correlation analysis and the linkET package were used to analyze the correlation between cecal microflora and production performance indicators that showed significant differences between the two groups and showed that birth weight was significantly positively correlated with Deferribacterota at the phylum level. At the genus level, leg and chest muscle weights exhibited significant positive correlations with Prevotellace-ae_Ga6A1_group, suggesting its critical role in promoting the growth and development of goose leg and chest muscles. A significant negative correlation was observed between [Ruminococ-cus]_torque and Prevotellaceae_Ga6A1_group. These findings offer a crucial theoretical foundation for the study of gastrointestinal microorganisms and provide insights into the development and formulation of poultry probiotics.

Age-specific composition of milk microbiota in Tibetan sheep and goats

This study investigates the dynamic changes in milk nutritional composition and microbial communities in Tibetan sheep and goats during the first 56 days of lactation. Milk samples were systematically collected at five time points (D0, D7, D14, D28, D56) post-delivery. In Tibetan sheep, milk fat, protein, and casein contents were highest on D0, gradually decreased, and stabilized after D14, while lactose and galactose levels showed the opposite trend. Goat milk exhibited similar initial peaks, with significant changes particularly between D0, D7, D14, and D56. 16S rRNA gene sequencing revealed increasing microbial diversity in both species over the lactation period. Principal coordinates analysis identified distinct microbial clusters corresponding to early (D0–D7), transitional (D14–D28), and mature (D56) stages. Core phyla, including Proteobacteria, Firmicutes, Bacteroidetes, and Actinobacteria, dominated the milk microbiota, with significant temporal shifts. Core microbes like Lactobacillus, Leuconostoc, and Streptococcus were common in both species, with species-specific taxa observed (e.g., Pediococcus in sheep, Shewanella in goats). Furthermore, we observed a highly shared core microbiota in sheep and goat milk, including Lactobacillus, Leuconostoc, and Streptococcus. Spearman correlation analysis highlighted significant relationships between specific microbial genera and milk nutrients. For instance, Lactobacillus positively correlated with total solids, non-fat milk solids, protein, and casein, while Mannheimia negatively correlated with protein content. This study underscores the complex interplay between milk composition and microbial dynamics in Tibetan sheep and goats, informing strategies for livestock management and nutritional enhancement.Key points• The milk can be classified into three types based on the microbiota composition• The changes of milk microbiota are closely related to the variations in nutrition• Filter out microbiota with species specificity and age specificity in the milk

Effects of forest age and season on soil microbial communities in Chinese fir plantations.

Understanding changes in the distribution patterns and diversity of soil microbial communities from the perspectives of age-related changes, seasonal variations, and the interaction between the two factors can facilitate the management of plantations. In Chinese fir plantations, we collected soils from different depths in over-mature forests, mature forests, near-mature forests, middle-aged forests, and young forests in summer, autumn, and winter in China's subtropical regions. As the forests developed, bacterial and fungal communities' diversity changed, reached a minimum value at near-mature forests, and then increased in mature forests or over-mature forests. Near-mature forests had the lowest topological properties. The Shannon index of microbial communities varied with seasonal changes (P < 0.05). Bacterial and fungal community composition at genus level was more closely related to temperature indicators (including daily average temperature, daily maximum temperature, and daily minimum temperature) (P < 0.01, 0.5554 < R2 <0.8185) than daily average precipitation (P > 0.05, 0.0321 < R2 <0.6773). Bacteria were clustered by season and fungi were clustered by forest age. We suggested that extending the tree cultivation time of plantations could promote microbial community recovery. In addition, we found some species worthy of attention, including Bacteroidetes in autumn in over-mature forests, and Firmicutes in summer in young forests.IMPORTANCEChinese fir [Cunninghamia lanceolata (Lamb.) Hook] is an important fast-growing species with the largest artificial forest area in China, with the outstanding problems of low quality in soil. Soil microorganisms play a crucial role in soil fertility by decomposing organic matter, optimizing soil structure, and releasing essential nutrients for plant growth. In order to maintain healthy soil quality and prevent nutrient depletion and land degradation, it is crucial to understand the changes of soil microbial composition and diversity. Our study determined to reveal the change of soil microbial community from stand age, season, and the interaction between the two aspects, which is helpful to understand how interannual changes in different years and seasonal changes in one year affect soil fertility restoration and sustainable forest plantation management. It is a meaningful exploration of soil microbial communities and provides new information for further research.

Interaction Effects of Vegetation and Soil Factors on Microbial Communities in Alpine Steppe Under Degradation

To clarify the regulating effect of vegetation and soil factors on microbial communities in the alpine steppe under degradation on the Qinghai-Xizang Plateau, the alpine steppe in the Sanjiangyuan area of the Qinghai-Tibet Plateau was chosen. We analyzed the differences in vegetation and soil factors in different stages of degradation （non-degradation, moderate degradation, and severe degradation） and detected the variations in microbial community characteristics in the alpine steppe under different degradation stages using high-throughput sequencing technology. Eventually, redundancy analysis （RDA） and multiple regression matrixes （MRM） based on the similarity or dissimilarity matrix were used to identify key environmental factors regulating microbial （bacterial and fungal） community changes under degradation. The results showed that the degradation of the alpine steppe significantly changed the community coverage, height, biomass, and important value of graminae； significantly reduced the contents of soil organic matter, total nitrogen, total phosphorus, and silt； and increased the soil bulk density and sand content. Degradation did not change the composition of bacteria and fungi, but their composition proportions changed and also resulted in the loss of microbial richness （Chao1 index and Richness index） but did not significantly change the microbial diversity （Shannon index）. With the occurrence of degradation, the vegetation characteristics, soil physicochemical properties, and microbial diversity showed a consistent change trend. Combined with the characteristics of the network topology changes （the number of nodes and clustering coefficient significantly decreased）, it was found that degradation of the alpine steppe led to the decline of interspecies interactions, decentralization of network, and homogenization of microorganisms, but the cooperation relations among the species were maintained （positive correlation connections accounted for more than 90% in all degradation stages）. Under the alpine steppe degradation, the vegetation-soil interaction had the greatest effect on soil bacterial community, whereas soil physicochemical properties had the greatest influence on soil fungal community. Specifically, vegetation community height, biomass, and soil bulk density were the mutual factors regulating soil microorganisms, whereas the vegetation Simpson index, important value of graminae, soil total phosphorus, total potassium, and silt content were the unique factors affecting the soil bacterial community, and soil pH and total nitrogen content were the particular factors affecting the soil fungal community.

Modeling and tracing of polycarbonate (PC) degradation in soil microcosm with a PC microplastics quantification method based on pyrolysis GC–MS

Understanding the migration and transformation of polycarbonate (PC) plastic wastes in the natural environment is crucial for assessing their environmental impact and bioremediation. In this study, PC plastic degradation was modeled and traced in soil microcosm by investigating physiochemical properties changes of PC, the formation of microplastics, and changes in soil microbial communities. Notably, PC microplastics quantification method was also successfully devised by pyrolysis gas chromatography mass spectrometry and also applied herein. Through gel permeation chromatography analysis, the molecular weight of the naturally aged PC film obviously reduced, whereas no change for unaged ones. After 12 months of soil burial, the surface corrosion and holes formation were emerged on the surfaces of both PC films in the non-sterilized soil harboring indigenous microorganisms by scanning electron microscope. The worsened thermal stability of both PC films in non-sterilized soil was demonstrated by thermogravimetric analysis. Meanwhile, the presence of increased hydroxyl group absorption and decreased carbonyl peak highlighted molecular chain breakage in both PC films by Fourier transform infrared spectroscopy. In particular, all the changes were more significant in aged PC than unaged ones. Furthermore, the increase of quantified PC microplastics on the surface of PC film in the non-sterilized soil accompanied the decreasing of microbial diversity and the enrichment of potential functional microorganisms. These findings revealed that the combination of natural aging and indigenous microbes exhibited a noticeable performance in PC plastics degradation in soil microcosm, providing new insights into the degradation mechanism of PC plastic wastes in the natural environment.