Cultivation of earthworms and analysis of associated bacterial communities during earthworms' growth using two types of agricultural wastes.

Earthworm cultivation can effectively promote the resource utilization of agricultural waste. The efficient utilization of agricultural waste by earthworms mainly depends on the microbial communities in the guts. This study used silkworm excrement and cow manure as substrates for earthworm cultivation and investigated the associated bacterial communities during earthworms' growth. The survival rate of earthworms remained above 89% after 21 days of feeding with the two substrates. Proteobacteria, Actinobacteria, and Firmicutes constituted the predominant bacterial communities in earthworm growth, accounting for over 81% of the relative abundance in both guts and vermicompost. The bacteria richness and diversity in the foregut and midgut of earthworm were lower than those in the hindgut. The prediction function of intestinal bacterial communities of earthworms cultured with two substrates mainly involved biosynthesis, decomposition and energy production.

Differential regulation of belowground rhizospheric ecosystem by biological and chemical nitrogen supplies: implications for maize yield enhancement mechanisms.

Nitrogen (N) content affects aboveground maize growth and nutrient absorption by altering the belowground rhizospheric ecosystem, impacting both yield and quality. However, the mechanisms through which different N supply methods (chemical and biological N supplies) regulate the belowground rhizospheric ecosystem to enhance maize yield remain unclear. To address this issue, we conducted a field experiment in northeast China, comprising three treatments: maize monocropping without N fertilizer application (MM), maize/alfalfa intercropping without N fertilizer application (BNF), and maize monocropping with N fertilizer application (CNS). The MM treatment represents the control, while the BNF treatment represents the biological N supply form, and CNS treatment represents the chemical N supply form. In the autumn of 2019, samples of maize and rhizospheric soil were collected to assess parameters including yield, rhizospheric soil characteristics, and microbial indicators. Both BNF and MM significantly increased maize yield and different yield components compared with MM, with no statistically significant difference in total yield between BNF and CNS. Furthermore, BNF significantly improved N by 12.61% and available N (AN) by 13.20% compared with MM. Furthermore, BNF treatment also significantly increased the Shannon index by 1.90%, while the CNS treatment significantly increased the Chao1 index by 28.1% and ACE index by 29.49%, with no significant difference between CNS and BNF. However, CNS had a more pronounced impact on structure of the rhizosphere soil bacterial community compared to BNF, inducing more significant fluctuations within the microbial network (modularity index and negative cohesion index). Regarding N transformation pathways predicted by bacterial functions, BNF significantly increased the N fixation pathway, while CNS significantly increased assimilatory nitrate reduction. In CNS, AN, NO3-N, NH4-N, assimilatory nitrate reduction, and community structure contributed significantly to maize yield, whereas in BNF, N fixation, community structure, community stability, NO3-N, and NH4-N played significant roles in enhancing maize yield. While CNS and BNF can achieve comparable maize yields in practical agricultural production, they have significantly different impacts on the belowground rhizosphere ecosystem, leading to different mechanisms of yield enhancement.

The application of varying amount of green manure combined with nitrogen fertilizer altered the soil bacterial community and rice yield in karst paddy areas.

Long-term application of green manure (GM) and nitrogen (N) fertilizers markedly improved soil fertility and boosted rice yield in ecologically fragile karst paddy fields. However, the precise response mechanisms of the soil bacterial community to varying amounts of green manure alone and in combination with N fertilizer in such environments remain poorly elucidated. In this study, we investigated the soil bacterial communities, keystone taxa, and their relationship with soil environmental variables across eight fertilization treatments. These treatments included group without N addition (N0M0, no N fertilizer and no GM; N0M22.5, 22.5 t/ha GM; N0M45, 45 t/ha GM, N0M67.5, 67.5 t/ha GM) and group with N addition (NM0, N fertilizer and no GM; NM22.5, N fertilizer and 22.5 t/ha GM; NM45, N fertilizer and 45 t/ha GM; NM67.5, N fertilizer and 67.5 t/ha GM). The results revealed that increasing green manure input significantly boosted rice yield by 15.51-22.08% and 21.84-35% in both the group without and with N addition, respectively, compared to N0M0 treatment. Moreover, with escalating green manure input, soil TN, AN, AK, and AP showed an increasing trend in the group without N addition. However, following the addition of N fertilizer, TN and AN content initially rose, followed by a decline due to the enhanced nutrient availability for rice. Furthermore, the application of a large amount of N fertilizer decreased the C: N ratio in the soil, resulting in significant changes in both the soil microbial community and its function. Particularly noteworthy was the transition of keystone taxa from their original roles as N-fixing and carbon-degrading groups (oligotrophs) to roles in carbon degradation (copiotrophs), nitrification, and denitrification. This shift in soil community and function might serve as a primary factor contributing to enhanced nutrient utilization efficiency in rice, thus significantly promoting rice yield.

Deciphering Indigenous Bacterial Diversity of Co-Polluted Sites to Unravel Its Bioremediation Potential: A Metagenomic Approach.

Polluted drains across the globe are affected due to reckless disposal of untreated industrial effluents resulting in significant water pollution affecting microbial community structure/dynamics. To elucidate this, polluted samples were collected from Budha Nala (BN) drain, Tung Dhab (TD) drain, and wastewater treatment plant (WWTP) receiving an inflow of organic pollutants as well as heavy metals due to anthropogenic activities. The sample of unpolluted pristine soil (PS) was used as control, as there is no history of usage of organic chemicals at this site. The bacterial diversity of these samples was sequenced using the Illumina MiSeq platform by amplifying the V3/V4 region of 16S rRNA. The majority of operational taxonomic unit (OTUs) at polluted sites belonged to phyla Proteobacteria specifically Gammaproteobacteria class, followed by Actinobacteria, Bacteriodetes, Chloroflexi, Firmicutes, Planctomycetes, WS6, and TM7, whereas unpolluted site revealed the prevalence of Proteobacteria followed by Actinobacteria, Planctomycetes, Firmicutes, Acidobacteria, Chloroflexi, Bacteroidetes, Verrucomicrobia, and Nitrospirae. The data sets decode unclassified species of the phyla Proteobacteria, Bacteriodetes, Chloroflexi, Firmicutes, and WS6, along with some unclassified bacterial species. The study provided a comparative study of changed microbial community structure, their possible functions across diverse geographical locations, and identifying specific bacterial genera as pollution bio-indicators of aged polluted drains.

Bacterial and fungal communities regulated directly and indirectly by tobacco-rape rotation promote tobacco production.

Tobacco continuous cropping is prevalent in intensive tobacco agriculture but often leads to microbial community imbalance, soil nutrient deficiency, and decreased crop productivity. While the tobacco-rape rotation has demonstrated significant benefits in increasing tobacco yield. Microorganisms play a crucial role in soil nutrient cycling and crop productivity. However, the internal mechanism of tobacco-rape rotation affecting tobacco yield through microbe-soil interaction is still unclear. In this study, two treatments, tobacco continuous cropping (TC) and tobacco-rape rotation (TR) were used to investigate how planting systems affect soil microbial diversity and community structure, and whether these changes subsequently affect crop yields. The results showed that compared with TC, TR significantly increased the Shannon index, Chao1 index, ACE index of bacteria and fungi, indicating increased microbial α-diversity. On the one hand, TR may directly affect the bacterial and fungal community structure due to the specificity of root morphology and root exudates in rape. Compared with TC, TR significantly increased the proportion of beneficial bacterial and fungal taxa while significantly reduced soil-borne pathogens. Additionally, TR enhanced the scale and complexity of microbial co-occurrence networks, promoting potential synergies between bacterial OTUs. On the other hand, TR indirectly changed microbial community composition by improving soil chemical properties and changing microbial life history strategies. Compared with TC, TR significantly increased the relative abundance of copiotrophs while reduced oligotrophs. Notably, TR significantly increased tobacco yield by 39.6% compared with TC. The relationships among yield, microbial community and soil chemical properties indicated that planting systems had the greatest total effect on tobacco yield, and the microbial community, particularly bacteria, had the greatest direct effect on tobacco yield. Our findings highlighted the potential of tobacco-rape rotation to increase yield by both directly and indirectly optimizing microbial community structure.

Horizontal gene transfer plays a crucial role in the development of antibiotic resistance in an antibiotic-free shrimp farming system.

Antibiotic selective pressure in aquaculture systems often results in the antibiotic resistance genes (ARGs) proliferation. Nonetheless, a paucity of data exists concerning the mechanisms of ARGs development in aquaculture systems without the influences of antibiotics. This study utilized metagenomic approaches to elucidate the dynamics and transfer mechanisms of ARGs throughout the aquaculture of Pacific white shrimp. A marked change in the resistome was observed throughout the aquaculture without antibiotics. The total ARGs relative abundance increased from 0.05 to 0.33 by day 90 of cultivation, with even higher in mixed wastewater (0.44). Both bacterial communities and mobile genetic elements play pivotal roles in the development of ARGs. Metagenome-assembled genomes showed enrichment of environmentally intrinsic ARGs on chromosomes including macB and mdtK. The plasmid-mediated horizontal transfer was recognized as a principal factor contributing to the rise of ARGs, particularly for tetG and floR, and this led to an escalation of resistance risk, peaking at a risks core of 35.43 on day 90. This study demonstrates that horizontal gene transfer plays a crucial role in ARGs development without antibiotic pressure, which can provide a theoretical foundation for controlling ARGs proliferation in aquaculture systems.

Genetically modified indigenous Pseudomonas aeruginosa drove bacterial community to change positively toward microbial enhanced oil recovery applications.

AIMS: Microbial enhanced oil recovery (MEOR) is cost-effective and eco-friendly for oil exploitation. Genetically modified biosurfactants-producing high-yield strains are promising for ex-situ MEOR. However, can they survive and produce biosurfactants in petroleum reservoirs for in-situ MEOR? What is their effect on the native bacterial community? METHODS AND RESULTS: A genetically modified indigenous biosurfactants-producing strain Pseudomonas aeruginosa PrhlAB was bioaugmented in simulated reservoir environments. P. aeruginosa PrhlAB could stably colonize in simulated reservoirs. Biosurfactants (200 mg L-1) were produced in simulated reservoirs after bio-augmenting strain PrhlAB. The surface tension of fluid was reduced to 32.1 mN m-1. Crude oil was emulsified with an emulsification index of 60.1%. Bio-augmenting strain PrhlAB stimulated the MEOR-related microbial activities. Hydrocarbons-degrading bacteria and biosurfactants-producing bacteria were activated, while the hydrogen sulfide producing bacteria were inhibited. Bio-augmenting P. aeruginosa PrhlAB reduced the diversity of bacterial community, and gradually simplified the species composition. Bacteria with oil displacement potential became dominant genera, such as Shewanella, Pseudomonas and Arcobacter. CONCLUSIONS: Culture-based and sequence-based analysis reveal that genetically modified biosurfactants-producing strain P. aeruginosa PrhlAB are promising for in-situ MEOR as well.

Microbial community structure in an uranium-rich acid mine drainage site: implication for the biogeochemical release of uranium.

The generation of acid mine drainage (AMD) characterized by high acidity and elevated levels of toxic metals primarily results from the oxidation and dissolution of sulfide minerals facilitated by microbial catalysis. Although there has been significant research on microbial diversity and community composition in AMD, as well as the relationship between microbes and heavy metals, there remains a gap in understanding the microbial community structure in uranium-enriched AMD sites. In this paper, water samples with varying levels of uranium pollution were collected from an abandoned stone coal mine in Jiangxi Province, China during summer and winter, respectively. Geochemical and high-throughput sequencing analyses were conducted to characterize spatiotemporal variations in bacterial diversity and community composition along pollution groups. The results indicated that uranium was predominantly concentrated in the AMD of new pits with strong acid production capacity, reaching a peak concentration of 9,370 µg/L. This was accompanied by elevated acidity and concentrations of iron and total phosphorus, which were identified as significant drivers shaping the composition of bacterial communities, rather than fluctuations in seasonal conditions. In an extremely polluted environment (pH < 3), bacterial diversity was lowest, with a predominant presence of acidophilic iron-oxidizing bacteria (such as Ferrovum), and a portion of acidophilic heterotrophic bacteria synergistically coexisting. As pollution levels decreased, the microbial community gradually evolved to cohabitation of various pH-neutral heterotrophic species, ultimately reverting back to background level. The pH was the dominant factor determining biogeochemical release of uranium in AMD. Acidophilic and uranium-tolerant bacteria, including Ferrovum, Leptospirillum, Acidiphilium, and Metallibacterium, were identified as playing key roles in this process through mechanisms such as enhancing acid production rate and facilitating organic matter biodegradation.

Bacterial networks and enzyme genes in bacterial floccules from hydrolysis and aeration reactors in a dairy wastewater treatment system.

The dairy industry generates substantial wastewater, which is commonly treated using integrated anaerobic hydrolysis and aerated biofilm reactors. However, the bacterial composition and functional differences within the generated floccules remain unclear. In this study, we employed 16S rRNA and metagenomic sequencing to compare bacterial communities and enzyme gene profiles between suspended floccules from the hydrolysis ponds and the aeration ponds. Results revealed that the bacterial phyla Firmicutes, Proteobacteria, and Bacteroidetes, dominated the wastewater treatment system and the relative abundance of these bacterial phyla varied in each pond. Additionally, the aeration ponds exhibited higher bacterial OTUs and enzyme gene abundance. Network analysis demonstrated a more complex bacterial network structure in the hydrolysis ponds compared to the aeration ponds. Furthermore, enzyme gene abundance revealed higher metabolic enzyme genes in the hydrolysis ponds, while signal transduction enzyme genes were more abundant in the aeration ponds. Notably, the top ten bacterial genera, primarily Hydromonas in the hydrolysis ponds and Ferruginibacter in the aeration ponds exhibited distinct contributions to signal transduction enzyme genes. Hydromonas dominated the metabolic enzyme genes in both ponds. These findings provide crucial insights for optimizing dairy wastewater treatment technologies.

Removal of artificial sweeteners in wastewater treatment plants and their degradation during sewage sludge composting with micro- and nano-sized kaolin.

This study surveyed the fates of artificial sweeteners in influent, effluent, and sewage sludge (SS) in wastewater treatment plant, and investigated the effects of Micro-Kaolin (Micro-KL) and Nano-Kaolin (Nano-KL) on nitrogen transformation and sucralose (SUC) and acesulfame (ACE) degradation during SS composting. Results showed the cumulative rate of ACE and SUC in SS was ∼76 %. During SS composting, kaolin reduced NH3 emissions by 30.2-45.38 %, and N2O emissions by 38.4-38.9 %, while the Micro-KL and Nano-KL reduced nitrogen losses by 14.8 % and 12.5 %, respectively. Meanwhile, Micro-KL and Nano-KL increased ACE degradation by 76.8 % and 84.2 %, and SUC degradation by 75.3 % and 77.7 %, and significantly shifted microbial community structure. Furthermore, kaolin caused a positive association between Actinobacteria and sweetener degradation. Taken together, kaolin effectively inhibited nitrogen loss and promoted the degradation of ACE and SUC during the SS composting, which is of great significance for the removal of emerging organic pollutants in SS.

Acidithiobacillus species mediated mineral weathering promotes lead immobilization in ferric-silica microstructures at sulfidic tailings.

Immobilization and stabilization of heavy metals (HMs) in sulfidic and metallic tailings are critical to long-term pollution control and sustainable ecological rehabilitation. This study aims to unravel immobilization mechanisms of Pb (Ⅱ) in the neoformed hardpan structure resulting from Acidithiobacillus spp. accelerated bioweathering of sulfides in the presence of silicates. It was found that the bioweathered mineral composite exhibited an elevated Pb (Ⅱ) adsorption capacity compared to that of natural weathered mineral composite. A suit of microspectroscopic techniques such as synchrotron-based X-ray Absorption Spectroscopy (XAS), X-ray Photoelectron Spectroscopy (XPS), Fourier Transform Infrared Spectroscopy (FTIR) and Field-Emission Scanning Electron Microscope (FE-SEM) indicated that secondary Fe-bearing minerals, functional groups, and surface properties in the neoformed hardpan were key factors contributing to Pb (Ⅱ) adsorption and immobilization in ferric-silica microstructures. The underlying mechanisms might involve surface adsorption-complexation, dissolution-precipitation, electrostatic attraction, and ion exchange. Microbial communities within the muscovite groups undergoing bioweathering processes demonstrated distinctive survival strategies and community composition under the prevailing geochemical conditions. This proof of concept regarding Pb (Ⅱ) immobilization in microbial transformed mineral composite would provide the basis for scaling up trials for developing field-feasible methodology to management HMs pollution in sulfidic and metallic tailings in near future.

Land use/cover drive functional patterns of bacterial communities in sediments of a subtropical river, China.

The bacterial community in sediment serves as an important indicator for assessing the environmental health of river ecosystems. However, the response of bacterial community structure and function in river basin sediment to different land use/cover changes has not been widely studied. To characterize changes in the structure, composition, and function of bacterial communities under different types of land use/cover, we studied the bacterial communities and physicochemical properties of the surface sediments of rivers. Surface sediment in cropland and built-up areas was moderately polluted with cadmium and had high nitrogen and phosphorus levels, which disrupted the stability of bacterial communities. Significant differences in the α-diversity of bacterial communities were observed among different types of land use/cover. Bacterial α-diversity and energy sources were greater in woodlands than in cropland and built-up areas. The functional patterns of bacterial communities were shown that phosphorus levels and abundances of pathogenic bacteria and parasites were higher in cropland than in the other land use/cover types; Urban activities have resulted in the loss of the denitrification function and the accumulation of nitrogen in built-up areas, and bacteria in forested and agricultural areas play an important role in nitrogen degradation. Differences in heavy metal and nutrient inputs driven by land use/cover result in variation in the composition, structure, and function of bacterial communities.

Distinct electrochemical and metabolic responses of anode respiring bacteria to sulfamethoxazole in microbial fuel cells coupled with constructed wetlands.

The influence of sulfamethoxazole (SMX) on the electrochemical activity, bacterial community, and metabolic state of anode respiring microbes was investigated in constructed-wetland-coupled microbial fuel cells (CW-MFCs). Results suggested that SMX shortened the acclimatisation period and enhanced the maximal power density of the CW-MFC at 0.1 mg/L. Cyclic voltammetry (CV) results indicated that SMX may trigger an electrocatalytic process related to an extra redox-active compound. Exposure to SMX significantly altered the bacterial communities, leading to decreased abundances of Desulfurivibrio and Pseudomonas, while increasing the contents of Rhodobacter and Anaerovorax. Furthermore, metabolites related to amino acids and nucleotide metabolism were suppressed at 10 mg/L SMX, while the related metabolites increased at 0.1 mg/L SMX. The upregulated pathway of biofilm formation indicated that the bacteria tended to form biofilms under the influence of SMX. This study provides valuable insights into the complex interactions between SMX and electrochemically active bacteria.

Effects of Enterobacter cloacae insecticidal protein on the Duox-ROS system and midgut bacterial community and function of Galleria mellonella larvae.

BACKGROUND: Enterobacter cloacae insecticidal proteins have been reported to kill Galleria mellonella larvae through affecting their midgut microbiome. However, the mechanisms involved remain unclear. Here we aim to investigate how the insecticidal proteins act on the midgut Duox-ROS system and microbial community of G. mellonella larvae. METHODS: Reverse transcription qPCR and fluorescence probes were utilized to assess the Duox expression levels and to evaluate quantitative changes of the ROS levels. Sequencing of the 16S rRNA gene sequences of the midgut bacteria of G. mellonella larvae was conducted for further analyses of bacterial diversity, composition, and abundance. RESULTS: After the injection of the insecticidal proteins, the Duox expression levels first increased within 28 h, then dramatically peaked at 36 h, and slowly decreased thereafter. Simultaneously, the ROS levels increased significantly at 36 h, peaked at 48 h, and rapidly declined to the normal level at 60 h. Responsive to the change of the ROS levels, the structure of the midgut microbial community was altered substantially, compared to that of the untreated larvae. The relative abundance of Enterobacteriaceae and other specific pathogenic bacteria increased significantly, whereas that of Lactobacillus decreased sharply. Importantly, notable shifts were observed in the crucial midgut predicted metabolic functions, including membrane transportation, carbohydrate metabolism, and amino acid metabolism. CONCLUSION: Insecticidal proteins of E. cloacae kill G. mellonella larvae mainly through generation of high oxidative stress, alterations of the midgut microbial community and function, and damage to the physiological functions. These findings provide insights into the inhibition mechanism of E. cloacae insecticidal proteins to G. mellonella larvae.

Anthropogenic activity shapes the assemble and co-occurrence pattern of microbial communities in fishing harbors around the Bohai Economic Circle.

This study aimed to elucidate the effects of coastal environmental stress on the composition of sediment bacterial communities and their cooccurrence patterns in fishing harbors around the Bohai Economic Circle, China. Compared with the natural sea area, fishing harbors contained higher levels of organic pollution (organic pollution index = 0.12±0.026) and considerably reduced bacterial richness and evenness. The distributions of sediment microbial communities clustered along the pollutant concentration gradients across fishing harbors. Betaproteobacteria dominated (76%) organically polluted fishing harbors, which were mostly disturbed by anthropogenic activities. However, the harbors also revealed the absence of numerous pathogenic (Coxiella and Legionella) and photosynthetic (Synechococcus and Leptolyngbya) bacteria. Abundant genera, including Thiobacillus and Arenimonas, exhibited a positive correlation with total phosphorus and a negative correlation with total nitrogen in sediments. Meanwhile, Sulfurovum, Psychrobacter, and Woeseia showed the opposite trend. Pollutant accumulation and anthropogenic activities caused the decrease in the sediment microbial diversity and dispersal ability and promoted convergent evolution. Severely polluted harbors with simplified cooccurrence networks revealed the presence of destabilized microbial communities. In addition, the modularity of bacterial networks decreased with organic pollution. Our results provide important insights into the adjustment mechanism of microbial communities to community organization and functions under environmental pollution stress. Overall, this study enhanced our understanding of how microbial communities in coastal sediments adapted and survived amidst anthropogenic activities like oily effluent discharges from large ships, wash water, domestic sewage, garbage, and fisheries wastes. It also examined their resilience to future contamination.

Effect of thermal treatment of illite on the bioavailability of copper and zinc in the aerobic composting of pig manure with corn straw.

The large amount of various types of heavy metals in animal manure applied to agricultural field has caused severe threat to the ecosystems of soil environments. In this study, the effect of thermal treatment of illite on the bioavailability of copper (Cu) and zinc (Zn) in the aerobic composting of pig manure with corn straw biochar was investigated. The objectives of this study were to characterize the variations in the bioavailability of Cu and Zn in the aerobic composting of pig manure added with illite treated with high temperatures and to identify the relatively dominant microbes involved in the formation of humus and passivation of heavy metals in pig manure composting based on 16S rRNA high-throughput sequencing analysis. The results showed that in comparison with the raw materials of pig manure, the bioavailability of Zn and Cu in the control and three experimental composting groups, i.e., group I (with untreated illite), group I-2 (with illite treated under 200°C), and group I-5 (with illite treated under 500°C), was decreased by 27.66 and 71.54%, 47.05 and 79.80%, 51.56 and 81.93%, and 58.15 and 86.60%, respectively. The results of 16S rRNA sequencing analysis revealed that in the I-5 group, the highest relative abundance was detected in Fermentimonas, which was associated with the degradation of glucose and fructose, and the increased relative abundances were revealed in the microbes associated with the formation of humus, which chelated with Zn and Cu to ultimately reduce the bioavailability of heavy metals and their biotoxicity in the compost. This study provided strong experimental evidence to support the application of illite in pig manure composting and novel insights into the selection of appropriate additives (i.e., illite) to promote humification and passivation of different heavy metals in pig manure composting.

[Spatial Patterns of Soil Bacterial Communities and N-cycling Functional Groups Along an Altitude Gradient in Datong River Basin].

The altitude distribution patterns of soil microorganisms and their driving mechanisms are crucial for understanding the consequences of climate change on terrestrial ecosystems. There is an obvious altitude difference in Datong River Basin in the Qilian Mountains. Two spatial scale transections were set up along the mountain slope (with altitude spanning 1 000 m) and the mainstream direction (with altitude spanning 300-500 m), respectively. The distribution characteristics of the soil bacterial community structure and diversity along the altitude gradients were examined using high-throughput sequencing technology. Based on the FAPROTAX database, the altitude distribution patterns of nitrogen cycling functional groups were analyzed to investigate the major environmental factors influencing the altitude distribution patterns of soil bacterial communities. The findings revealed that:① Soil physicochemical characteristics varied significantly with altitude. The content of total nitrogen (TN) and nitrate nitrogen (NO3-) were positively correlated with the altitude (P < 0.01), whereas the soil bulk density and pH were negatively connected (P < 0.001). ② The abundance of OTU increased significantly along the altitude (P < 0.01), and the richness and diversity indices increased along the altitude, although the trend was not statistically significant (P > 0.05). ③ The predominant bacterial communities were Acidobacteria, Proteobacteria, and Bacteroidetes, and as altitude climbed, their relative abundances varied between increasing, decreasing, and slightly decreasing, respectively. ④ The nitrogen cycling processes involved 13 functional groups, primarily nitrification, aerobic ammonia oxidation, aerobic nitrite oxidation, etc. As the altitude increased, the response law changed, with an increase in the abundance of nitrobacteria (P < 0.01), a slight increase in the abundance of aerobic ammonia-oxidizing bacteria and nitrite-oxidizing bacteria, and a hump-back tendency in bacteria abundance for nitrogen respiration. ⑤ Redundancy analysis revealed that the key determinants influencing soil bacterial populations at the phylum level were altitude, pH, and the content of NH4+. Mantel analysis showed that the dominant groups of soil bacterial nitrogen cycling were all statistically and significantly driven by altitude (P < 0.01). ⑥ The α-diversity of the bacterial community with increasing altitude were both increased along the mountain slope and the mainstream direction, but the soil properties, the abundance of N-cycling functional groups, and the main environmental factors differed. Therefore, it is of great significance to explore the altitude distribution pattern of soil microorganisms at different spatial scales.

[Effects of Fly Ash on the Efficiency and Bacterial Community Structure of Urban Multi-source Organic Solid Waste].

To achieve efficient resource utilization of fly ash and multi-source organic waste, a composting experiment was carried out to investigate the effects of fly ash on co-aerobic composting using kitchens, chicken manure, and sawdust (15:5:2). The effects of different application doses (5 % and 10 %, calculated in total wet weight of organic solid waste) of fly ash on physical and chemical properties, nutrient elements, and bacterial community structure during co-composting were evaluated. The results showed that the addition dose of 5 % and 10 % fly ash significantly increased the highest temperature (56.6 ℃ and 56.9 ℃) and extended the thermophilic period to nine days. Compared with that in the control, the total nutrient content of compost products in the treatments of 5 % FA and 10 % FA was increased by 4.09 % and 13.55 %, respectively. The bacterial community structure changed greatly throughout the composting, and the bacterial diversity of all treatments increased obviously. In the initial stage of composting, Proteobacteria was the dominant phylum of bacteria, with a relative abundance ranging from 35.26 % to 39.40 %. In the thermophilic period, Firmicutes dominated; its relative abundance peaked at 52.46 % in the 5 % FA treatment and 67.72 % in the 10 % FA treatment. Bacillus and Thermobifida were the predominant groups in the thermophilic period of composting. The relative abundance of Bacillus and Thermobifida in the 5 % FA and 10 % FA treatments were 33.41 % and 62.89 %(Bacillus) and 33.06 % and 12.23 %(Thermobifida), respectively. The results of the redundancy analysis (RDA) revealed that different physicochemical indicators had varying degrees of influence on bacteria, with organic matter, pH, available phosphorus, and available potassium being the main environmental factors influencing bacterial community structure. In summary, the addition of fly ash promoted the harmlessness and maturation of co- aerobic composting of urban multi-source organic waste, while optimizing microbial community structure and improving the quality and efficiency of composting.

Distinct strategies of the habitat generalists and specialists in the Arctic sediments: Assembly processes, co-occurrence patterns, and environmental implications.

Microorganisms could be classified as habitat generalists and specialists according to their niche breadth, uncovering their survival strategy is a crucial topic in ecology. Here, differences in environmental adaptation, community assemblies, co-occurrence patterns, and ecological functions between generalists and specialists were explored in the Arctic marine sediments. Compared to specialists, generalists showed lower alpha diversity but stronger environmental adaption, and dispersal limitation contributed more to the community assembly of specialists (74 %) than generalists (46 %). Furthermore, the neutral theory model demonstrated that generalists (m = 0.20) had a higher immigration rate than specialists (m = 0.02), but specialists exhibited more complex co-occurrence patterns than generalists. Our results also found that generalists may play more important roles in C, N, S metabolism but are weaker in carbon fixation and xenobiotic biodegradation and metabolism. This study would broaden our understanding of bacterial generalists' and specialists' survival strategies, and further reveal their ecological functions in marine sediments.

Engineered biochar combined clay for microplastic biodegradation during pig manure composting.

This study pursued to regulate bacterial community succession pattern and expedited biodegradation of microplastics (MP) during pig manure (PM) composting employing walnut shell biochar (WSB) and montmorillonite (M). The WSB with concentration of 0%, 2.5%, 5%, 7.5%, 10% and 12% along with 10% M participated into PM for 42 days compost to search the optimal solution. The results confirmed the most prosperous bacterial phylum consisted of Firmicutes (3.02%-91.80%), Proteobacteria (2.08%-48.54%), Chloroflexi (0-44.62%) and Bacteroidetes (0.85%-40.93%). The addition of biochar has dramatically arranged bacterial community at different stages of composting. Energy Dispersive Spectrometer (EDS) revealed that carbon element in MPs decreased since the chemical bond fracture, under the intervention of high-temperature composting and WSB, the carbon content of MPs was maximum reduced by 20.25%. Fourier transform infrared spectrum indicated that CC, C-O, C-H and -COOH abundance of MPs in 10% and 12% dose biochar addition sharply reduced, interestingly, explicating WSB and composting made MP biodegradable. This experiment possesses affirmatory practical meaning for elimination of potential hazards by composting.