Inoculation of phosphate-solubilizing bacteria (Bacillus) regulates microbial interaction to improve phosphorus fractions mobilization during kitchen waste composting

Low-intensity alternating ventilation achieves effective humification during food waste composting by enhancing the intensity of microbial interaction and carbon metabolism

Vertical static composting is an efficient and convenient technology for the treatment of food waste. Exploring the impact of oxygen concentration levels on microbial community structure and functional stability is crucial for optimizing ventilation technology. This study set three experimental groups with varying ventilation intensities based on self-made alternating ventilation composting reactor (AL2: 0.2 L kg-1 DM·min-1; AL4: 0.4 L kg-1 DM·min-1; AL6: 0.6 L kg-1 DM·min-1) to explore the optimal alternating ventilation rate. The results showed that the cumulative ammonia emission of AL2 group reduced by 25.13% and 12.59% compared to the AL4 and AL6 groups. The humification degree of the product was 1.18 times and 1.25 times higher than the other two groups. AL2 increased the relative abundance of the core species Saccharomonospora, thereby strengthening microbial interaction. Low-intensity alternating ventilation increased the carbon metabolism levels, especially aerobic_chemoheterotrophy, carbohydrate and lipid metabolism. However, it simultaneously reduced nitrogen metabolism. Structural equation model analysis demonstrated that alternating low-intensity ventilation effectively regulated both microbial diversity (0.81, p < 0.001) and metabolism (0.81, p < 0.001) by shaping the composting environment. This study optimized the intensity of alternating ventilation and revealed the regulatory mechanism of community structure and metabolism. This study provides guidance for achieving efficient and low-consumption composting.

Effect of initial moisture content, resulting from different ratios of vegetable waste to maize straw, on compost was mediated by composting temperatures and microbial communities at low temperatures

Owing to the huge amounts and perishable character of vegetable wastes, composting is one of the best options for recycling vegetable wastes post-harvest. The initial moisture content (MC) is critical for optimizing composting process, but the effect of high MC in undehydrated vegetable wastes on composting was rarely reported. For this, the plant-scale windrows were prepared by mixing cauliflower waste and maize straw at different ratios to control initial MC of 70 % (T1-70) and 80 % (T2-80), respectively, and composted in winter. As composting progressed, substantial organic matter degradation, progressive humification, decreases in electrical conductivity and increases of pH and germination index (GI) were observed in both treatments. Nonetheless, T1-70 accelerated heating rate early during composting, prolonged high temperature period (>50 °C) by 30 d, thus increased the harmless level of composting, and significantly improved the humification of end-products compared to T2-80. Results also revealed that T1-70 activated more indigenous microbes and enhanced microbial interactions early during composting, with the fungi enriched in T1-70 playing an important role in accelerating the composting process. Remarkably, the difference in composting temperatures, humification degree, and microbial communities between the two treatments was most significant during the maturation phase. In this phase, MWH_CFBk5, Planktosalinus, Pseudopedobacter, and Luteimonas enriched in T1-70 were positively correlated with humification indices. It is suggested that the effect of initial MC, resulting from different ratios of vegetable waste to maize straw, on their composting was mediated by the composting temperature and microbial communities at low temperatures.

Response of phosphorus fractions transformation and microbial community to carbon-to-phosphorus ratios during sludge composting

Phosphorus (P) is one of the essential nutrient elements for plant growth and development. Sludge compost products can be used as an important source of soil P to solve the shortage of soil P. The difference in the initial carbon-to-phosphorus ratio (C/P) will lead to difference in the bacterial community, which would affect the biological pathway of P conversion in composting. However, few studies have been reported on adjusting the initial C/P of composting to explore P conversion. Therefore, this study investigated the response of P component transformations, bacterial community and P availability to C/P during sludge composting by adjusting initial C/P. The results showed that increasing C/P promoted the mineralization of organic P and significantly increased the content of the labile P. High C/P also increased the relative content of available P, especially when the C/P was at 45 and 60, it reached 60.51% and 60.47%. High C/P caused differences in the community structure, and improved the binding ability of microbial network modules and the competitiveness of microbial communities. Additionally, high C/P strengthened the effect of microbial communities on the transformation of P components. Finally, the study showed that C/P was the main contributor to P content variation (64.7%) and indirectly affected P component conversion by affecting the microbial community. Therefore, adjusting the C/P is crucial to improve the P utilization rate of composting products.

Enhancing C and N turnover, functional bacteria abundance, and the efficiency of biowaste conversion using Streptomyces-Bacillus inoculation

Microbial inoculation plays a significant role in promoting the efficiency of biowaste conversion. This study investigates the function of Streptomyces-Bacillus Inoculants (SBI) on carbon (C) and nitrogen (N) conversion, and microbial dynamics, during cow manure (10% and 20% addition) and corn straw co-composting. Compared to inoculant-free controls, inoculant application accelerated the compost's thermophilic stage (8 vs 15 days), and significantly increased compost total N contents (+47%) and N-reductase activities (nitrate reductase: +60%; nitrite reductase: +219%). Both bacterial and fungal community succession were significantly affected by DOC, urease, and NH4+-N, while the fungal community was also significantly affected by cellulase. The contribution rate of Cupriavidus to the physicochemical factors of compost was as high as 83.40%, but by contrast there were no significantly different contributions (∼60%) among the top 20 fungal genera. Application of SBI induced significant correlations between bacteria, compost C/N ratio, and catalase enzymes, indicative of compost maturation. We recommend SBI as a promising bio-composting additive to accelerate C and N turnover and high-quality biowaste maturation. SBI boosts organic cycling by transforming biowastes into bio-fertilizers efficiently. This highlights the potential for SBI application to improve plant growth and soil quality in multiple contexts.

Investigating fungal community characteristics in co-composted cotton stalk and various livestock manure products

Agricultural wastes, comprising cotton straw and livestock manure, can be effectively managed through aerobic co-composting. Nevertheless, the quality and microbial characteristics of co-composting products from different sources remain unclear. Therefore, this study utilized livestock manure from various sources in Xinjiang, China, including herbivorous sheep manure (G), omnivorous pigeon manure (Y), and pigeon-sheep mixture (GY) alongside cotton stalks, for a 40-day co-composting process. We monitored physicochemical changes, assessed compost characteristics, and investigated fungal community. The results indicate that all three composts met established composting criteria, with compost G exhibiting the fastest microbial growth and achieving the highest quality. Ascomycota emerged as the predominant taxon in three compost products. Remarkably, at the genus level, the biomarker species for G, Y, and GY are Petromyces and Cordyceps, Neurospora, and Neosartorya, respectively. Microorganisms play a pivotal role in organic matter degradation, impacting nutrient composition, demonstrating significant potential for the decomposition and transformation of compost components. Redundancy analysis indicates that potassium, total organic carbon, and C:N are key factors influencing fungal communities. This study elucidates organic matter degradation in co-composting straw and livestock manure diverse sources, optimizing treatment for efficient agricultural waste utilization and sustainable practices.

Soil phosphorus transformation and plant uptake driven by phosphate-solubilizing microorganisms

Phosphorus (P) is an important nutrient for plants, and a lack of available P greatly limits plant growth and development. Phosphate-solubilizing microorganisms (PSMs) significantly enhance the ability of plants to absorb and utilize P, which is important for improving plant nutrient turnover and yield. This article summarizes and analyzes how PSMs promote the absorption and utilization of P nutrients by plants from four perspectives: the types and functions of PSMs, phosphate-solubilizing mechanisms, main functional genes, and the impact of complex inoculation of PSMs on plant P acquisition. This article reviews the physiological and molecular mechanisms of phosphorus solubilization and growth promotion by PSMs, with a focus on analyzing the impact of PSMs on soil microbial communities and its interaction with root exudates. In order to better understand the ability of PSMs and their role in soil P transformation and to provide prospects for research on PSMs promoting plant P absorption. PSMs mainly activate insoluble P through the secretion of organic acids, phosphatase production, and mycorrhizal symbiosis, mycorrhizal symbiosis indirectly activates P via carbon exchange. PSMs can secrete organic acids and produce phosphatase, which plays a crucial role in soil P cycling, and related genes are involved in regulating the P-solubilization ability. This article reviews the mechanisms by which microorganisms promote plant uptake of soil P, which is of great significance for a deeper understanding of PSM-mediated soil P cycling, plant P uptake and utilization, and for improving the efficiency of P utilization in agriculture.

Effect of microbial inoculum on composting efficiency in the composting process of spent mushroom substrate and chicken manure

This work aimed to investigate the microbial mechanisms for the improvement of composting efficiency driven by the compound microbial inoculum (MI) (Bacillus subtilis SL-44, Enterobacter hormaechei Rs-189 and Trichoderma reesei) during co-composting of spent mushroom substrate (SMS) and chicken manure (CM). The treatments used in the study were as follows: 1) MI (inoculation with microbial inoculum), 2) CI (inoculation with commercial microbial inoculum), and 3) CK (without inoculation). The results demonstrated that MI increased the seed germination index (GI) by 25.11%, and contents of humus, humic acid (HA) and available phosphorus (AP) were correspondingly promoted by 12.47%, 25.93% and 37.16%, respectively. The inoculation of MI increased the temperature of the thermophilic stage by 3-7 °C and achieved a cellulose degradation rate of 52.87%. 16S rRNA gene analysis indicated that Actinobacteria (11.73-61.61%), Firmicutes (9.46-65.07%), Proteobacteria (2.86-32.17%) and Chloroflexi (0.51-10.92%) were the four major phyla during the inoculation composting. Bacterial metabolic functional analysis revealed that pathways involved in amino acid and glycan biosynthesis and metabolism were boosted in the thermophilic phase. There was a positive correlation between bacterial communities and temperature, humification and phosphorus fractions. The average dry weight, fresh weight and seedling root length in the seedling substrates adding MI compost were 1.13, 1.23 and 1.06 times higher than those of the CK, respectively. This study revealed that biological inoculation could improve the composting quality and efficiency, potentially benefiting the resource utilization of agricultural waste resources.

Effect of simplified inoculum agent on performance and microbiome during cow manure-composting at industrial-scale

A simplified inoculum agent, only comprising Bacillus subtilis and Aspergillus niger, was utilized for industrial-scale cow-manure composting to investigate its impact on composting performance and microbiome. Inoculants elevated the average and peak temperatures by up to 7 and 10 °C, respectively, during the thermophilic stage, reduced organic matter content, and raised germination index. Inoculation also extended the period of composting above 50 °C from 12 to 26 days. Sequencing unveiled significant shifts in microbial diversity, composition, and function. Aspergillus thrived during the mesophilic phase, potentially initiating composting, whereas Bacillus, Lysinibacillus, and Clostridium were enriched during the thermophilic stage. Metagenomic sequencing revealed an increased abundance of carbohydrate-active enzymes and glycometabolism-related genes responsible for lignocellulose degradation and heat generation after inoculation. These enriched microbes and functional genes contributed to organic matter degradation and temperature maintenance during thermophilic stage, expediting composting. This suggests the effectiveness of this simplified inoculum in industrial-level cow-manure composting.

Functional differences of cultivable leaf-associated microorganisms in the native Andean tree Gevuina avellana Mol. (Proteaceae) exposed to atmospheric contamination

AIMS

This study aimed to evaluate and describe the functional differences of cultivable bacteria and fungi inhabiting the leaves of Gevuina avellana Mol. (Proteaceae) in an urban area with high levels of air pollution and in a native forest in the southern Andes.

METHODS AND RESULTS

Phyllosphere microorganisms were isolated from the leaves of G. avellana, their plant growth-promoting capabilities were estimated along with their biocontrol potential and tolerance to metal(loid)s. Notably, plants from the urban area showed contrasting culturable leaf-associated microorganisms compared to those from the native area. The tolerance to metal(loid)s in bacteria range from 15 to 450 mg l-1 of metal(loid)s, while fungal strains showed tolerance from 15 to 625 mg l-1, being especially higher in the isolates from the urban area. Notably, the bacterial strain Curtobacterium flaccumfaciens and the fungal strain Cladosporium sp. exhibited several plant-growth-promoting properties along with the ability to inhibit the growth of phytopathogenic fungi.

CONCLUSIONS

Overall, our study provides evidence that culturable taxa in G. avellana leaves is directly influenced by the sampling area. This change is likely due to the presence of atmospheric pollutants and diverse microbial symbionts that can be horizontally acquired from the environment.

Effects of Priestia aryabhattai on Phosphorus Fraction and Implications for Ecoremediating Cd-Contaminated Farmland with Plant-Microbe Technology

The application of phosphate-solubilizing bacteria has been widely studied in remediating Cd-contaminated soil, but only a few studies have reported on the interaction of P and Cd as well as the microbiological mechanisms with phosphate-solubilizing bacteria in the soil because the activity of phosphate-solubilizing bacteria is easily inhibited by the toxicity of Cd. This paper investigates the phosphorus solubilization ability of Priestia aryabhattai domesticated under the stress of Cd, which was conducted in a soil experiment with the addition of Cd at different concentrations. The results show that the content of Ca2-P increased by 5.12-19.84%, and the content of labile organic phosphorus (LOP) increased by 3.03-8.42% after the addition of Priestia aryabhattai to the unsterilized soil. The content of available Cd decreased by 3.82% in the soil with heavy Cd contamination. Priestia aryabhattai has a certain resistance to Cd, and its relative abundance increased with the increased Cd concentration. The contents of Ca2-P and LOP in the soil had a strong positive correlation with the content of Olsen-P (p < 0.01), while the content of available Cd was negatively correlated with the contents of Olsen-P, Ca2-P, and LOP (p < 0.05). Priestia aryabhattai inhibits the transport of Cd, facilitates the conversion of low-activity P and insoluble P to Ca2-P and LOP in the soil, and increases the bioavailability and seasonal utilization of P in the soil, showing great potential in ecoremediating Cd-contaminated farmland soil with plant-microbe-combined technology.

Enhancing food waste reduction efficiency and high-value biomass production in Hermetia illucens rearing through bioaugmentation with gut bacterial agent

The black soldier fly (BSF) rearing technology has been a promising bioconversion method for food waste (FW) disposal. However, when used independently, it currently only achieves low efficiency and biomass transformation rates (BTR). This study screened and identified two strains of gut beneficial bacteria, Bacillus cereus and Bacterium YC-LK-LKJ45. The efficiency of a complex culture formulated by these strains was investigated, focusing on enhancing FW reduction and high-value biomass production during the rearing of BSF larvae. The coculture agent group (G1-10%, with two strains in 1:1 volume ratio at a 10 % dosage) exhibited higher larval yield (627.67 g·kg-1), BTR (47.90 %), FW reduction efficiency (80.67 %), and total protein and fat yield (261.99 g·kg-1and 46.24 g·kg-1) compared to the control and the monoculture agent group (which added a single gut beneficial bacteria agent, either Bacillus cereus or Bacterium YC-LK-LKJ45). The bacterial agent altered the richness and diversity of the gut microbial community of BSF, increasing the relative abundance of beneficial bacteria such as Bacillus, Oceano bacillus, and Akkermansia, while decreasing pathogenic bacteria, such as Acinetobacter and Escherichia-Shigella. Structural equation model quantification revealed that α-diversity (λ = 0.897, p < 0.001) and BTR (λ = 0.747, p < 0.001) are crucial drivers for enhancing high-value biomass during bioaugmentation rearing. This investigation provides a theoretical framework for the effective management of food waste using BSF, enhancing its decomposition and transformation into higher-value biomass.

Phosphate-solubilizing fungi enhances the growth of Brassica chinensis L. and reduces arsenic uptake by reshaping the rhizosphere microbial community

High concentrations of arsenic in soil and plant systems are a threat to human health and ecosystems. The levels of phosphate ions in the soil strongly influence the soil efficacy and arsenic absorption by plants. This study investigated the effects of phosphate-solubilizing fungi (PSF) on environmental factors and structural changes in microbial community in soils contaminated with arsenic. Four experimental groups were created: control (CK), Penicillium GYAHH-CCT186 (W186), Aspergillus AHBB-CT196 (W196), and Penicillium GYAHH-CCT186 + Aspergillus AHBB-CT196 (W186 + W196), with Pakchoi (Brassica chinensis L.) as the test plant. Analysis of altered nutrient levels, enzyme activities and microbial community structure in the soil as well as the growth and physiological characteristics of Pakchoi, revealed a significant increase in the available phosphorus (AP), organic matter (OM), cation exchange capacity (CEC) and available arsenic (AAs) content of the soil following W186 + W196, W196 and W186 treatments. All experimental treatments enhanced the activity of soil β-glucosidase (β-GC) and soil catalase (S-CAT). W186 + W196 and W196 treatments significantly enhanced soil acid phosphatase (S-ACP) activity. Besides, W186 + W196 treatment significantly induced dehydrogenase (S-DHA) activity. Further, of the treatment with PSF increased the fresh weight, root length, plant height and chlorophyll levels while decreasing the arsenic accumulation in Pakchoi. Exposure to PSF also increased the activity of Ascomycota, Basidiomycota, Chytridiomycota, unclassified_Fungi, Mortierellomycota, Cryptomycota and Rozellomycota in the soil. The relative abundance of Ascomycota, Basidiomycota, and Mortierellomycota was positively correlated with the available nutrients (except iron) in the soil as well as enzyme activities. Consequently, the PSF improved the quality of soil and the safety of Pakchoi, suggesting that PSF can be utilized for the remediation of arsenic-contaminated soil.

Phosphate-solubilizing bacteria: Their agroecological function and optimistic application for enhancing agro-productivity

Phosphorus (P) is a limiting nutrient in the soil-plant nutrient cycling. Although the exogenous application of chemical P fertilizers can satisfy crop P requirements during critical growth phases. While excessive P fertilizers use results in low phosphorus acquisition efficiency (PAE), it has serious environmental consequences and hastens the depletion of P mineral reserves. Phosphate-solubilizing bacteria (PSB) have the potential to make insoluble phosphate available to plants through solubilization and mineralization, increasing crop yields while maintaining environmental sustainability. Existing reviews mainly focus on the beneficial effects of PSB on crop performance and related mechanisms, while few of them elucidate the action mechanisms of PSB in soil-microbe-plant interactions for crop cultivation with high yield efficiency. Hence, this study provides a comprehensive review of the physicochemical and molecular mechanisms (e.g., root exudates, extracellular polysaccharides, organic acids, phosphatases, and phosphate-specific transport systems) of PSB to facilitate the P cycle in the soil-plant systems. Further, the potential of commercial applications of PSB (e.g., genetic engineering, seed priming and coating) are also discussed in order to highlight their contribution to sustainable agriculture. Finally, existing challenges and future prospects in agricultural applications are proposed. In conclusion, we firmly believe that PSB represent a highly significant biotechnological tool for enhancing agricultural productivity and offers a wide range of extensive potential applications.

A comprehensive review on the decentralized composting systems for household biodegradable waste management

Municipal solid waste primarily consists of household biodegradable waste (HBW). HBW treatment is a crucial step in many countries due to rapid urbanization. Composting is an effective technique to treat HBW. However, conventional composting systems are unable to produce matured compost (MC), as well as releasing huge amounts of greenhouse and odorous gases. Therefore, this review attempts to suggest suitable composting system to manage HBW, role of additives and bulking agents in composting process, identify knowledge gaps and recommend future research directions. Centralized composting systems are unable to produce MC due to improper sorting and inadequate aeration for composting substrate. Recently, decentralized compost systems (DCS) are becoming more popular due to effective solid waste reduction at the household and/or community level itself, thereby reducing the burden on municipalities. Solid waste sorting and aeration for the composting substrate is easy at DCS, thereby producing MC. However, Mono-composting of HBW in DCS leads to production of immature compost and release greenhouse and odorous gases due to lower free air space and carbon-to-nitrogen ratios, and higher moisture content. Mixing HBW with additives and bulking agents in DCS resulted in a proper initial substrate for composting, allowing rapid degradation of substrate due to longer duration of thermophilic phase and produce MC within a shorter duration. However, people have lack of awareness about solid waste management is the biggest challenge. More studies are needed to eliminate greenhouse and odorous gases emissions by mixing different combinations of bulking agents and additives (mainly microbial additives) to HBW in DCS.

Nutrient-cycling functional gene diversity mirrors phosphorus transformation during chicken manure composting

Elucidating ecological mechanism underlying phosphorus transformation mediated by phosphate-solubilizing bacteria (PSB) during manure composting is an important but rarely investigated subject. The research objective is to disentangle ecological functions of the inoculation of PSB Pseudomonas sp. WWJ-22 during chicken manure composting based on gene quantification and amplicon sequencing. There are large dynamic changes in phosphorus fractions, gene abundances, and bacterial community structure. The PSB addition notably increased available phosphorus from 0.29-0.89 g kg-1 to 0.49-1.39 g kg-1 and significantly affected phosphorus fractionation. The PSB inoculation significantly affected composition of nutrient-cycling functional genes (NCFGs), and notably influenced bacterial community composition and function. Compost bacteria showed significant phylogenetic signals in response to phosphorus fractions, and stochastic processes dominated bacterial community assembly. Results emphasized that PSB addition increased functional redundancy, phylogenetic conservatism, and stochasticity-dominated assembly of bacterial community. Overall, findings highlight NCFG diversity can be a bio-indicator to mirror phosphorus transformation.

Effects of compost as a soil amendment on bacterial community diversity in saline-alkali soil

Introduction

Soil salinization poses a worldwide challenge that hampers agricultural productivity.

Methods

Employing high-throughput sequencing technology, we conducted an investigation to examine the impact of compost on the diversity of bacterial communities in saline soils. Our study focused on exploring the diversity of bacterial communities in the inter-root soil of plants following composting and the subsequent addition of compost to saline soils.

Results

Compared to the initial composting stage, Alpha diversity results showed a greater diversity of bacteria during the rot stage. The germination index reaches 90% and the compost reaches maturity. The main bacterial genera in compost maturation stage are Flavobacterium, Saccharomonospora, Luteimonas and Streptomyces. Proteobacteria, Firmicutes, and Actinobacteria were the dominant phyla in the soil after the addition of compost. The application of compost has increased the abundance of Actinobacteria and Chloroflexi by 7.6 and 6.6%, respectively, but decreased the abundance of Firmicutes from 25.12 to 18.77%. Redundancy analysis revealed that soil factors pH, solid urease, organic matter, and total nitrogen were closely related to bacterial communities.

Discussion

The addition of compost effectively reduced soil pH and increased soil enzyme activity and organic matter content. An analysis of this study provides theoretical support for compost's use as a saline soil amendment.

Insight into the microbial mechanisms for the improvement of spent mushroom substrate composting efficiency driven by phosphate-solubilizing Bacillus subtilis

The objective of this study was to investigate the microbial mechanisms for the improvement of composting efficiency after Bacillus subtilis inoculation with soluble phosphorus function in the spent mushroom substrate (SMS) aerobic composting. The methods in this study, including redundant analysis (RDA), co-occurrence network analyze and Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt 2) were carried out studying the dynamic changes of phosphorus (P) components, microbial interactions and metabolic characteristics in the SMS aerobic composting inoculated with phosphorus-solubilizing B. subtilis (PSB). An increase in germination index (GI) (up to 88.4%), total nitrogen (TN) (16.6 g kg^-1), available P content (0.34 g kg^-1) and total P (TP) content (3.20 g kg^-1) and a decrease in total organic carbon (TOC), C/N and electrical conductivity (EC) in final composting stage indicated B. subtilis inoculation could further improve maturity quality of the composting product compared with CK. Other results also demonstrated that PSB inoculation increased the stability of compost, humification degree and bacterial diversity, contributing to P fractions transformation in the composting process. Co-occurrence analysis suggested that PSB strengthened microbial interactions. Metabolic function of bacterial community analysis showed pathways such as carbohydrate metabolism, and amino acid metabolism in the composting were increased by effects of PSB inoculation. In summary, this study reveals a useful basis for better regulating the P nutrient level of the SMS composting and reducing environmental risks by inoculating B. subtilis with P solubilizing function.

Cadmium-resistant phosphate-solubilizing bacteria immobilized on phosphoric acid-ball milling modified biochar enhances soil cadmium passivation and phosphorus bioavailability

Cadmium (Cd) can accumulate in agriculture soil from the regular application of phosphorus (P) fertilizer. Microbiological method is considered as a potentially effective strategy that can not only remediate the Cd-contaminated soil but also provide the phosphorus needed for crop growth. However, the toxicity of Cd may affect the activity of microorganisms. To solve this problem, Klebsiella variicola with excellent phosphate solubilization ability (155.30 mg L^-1 at 48 h) and Cd adsorption rate (90.84 % with 10 mg L^-1 Cd initial concentration) was firstly isolated and identified in this study. Then, a phosphoric acid and ball milling co-modified biochar (PBC) was selected as the carrier to promote the activities of K. variicola under Cd pollution. Surface characterization revealed that the promotion of K. variicola by PBC was mainly attributed to the large specific surface area and diverse functional groups. Compared to contaminated soil, microbial PBC (MPBC) significantly increased the pakchoi biomass and phosphorus (P) content, while the Cd content in leave and root of pakchoi (Brassica chinensis L.) decreased by 25.90-43.46 % (P < 0.05). The combined application also favored the transformation of the resistant P fractions to bioavailable P, and facilitated the immobilization of 20.12 % exchangeable Cd to reducible, oxidizable, and residual Cd in the treated soil. High-throughput sequencing revealed that the response of the soil microbial community to the MPBC was more beneficial than K. variicola or PBC alone. Therefore, the application of MPBC has the potential to act as an efficient, stable, and environmentally friendly sustainable product for Cd remediation and enhanced P bioavailability in agricultural production.

Addition of exogenous microbial agents increases hydrogen sulfide emissions during aerobic composting of kitchen waste by improving bio-synergistic effects

The effect of microbial agents (MA) on hydrogen sulfide (H₂S) emissions in the compost is still a controversial issue. This study examined the effects and microbial mechanisms of MA on H₂S emissions during the composting of kitchen waste. The results showed that MA addition can promote sulfur conversion to elevate H₂S emissions by approximately 1.6 ∼ 2.8 times. Structural equations demonstrated that microbial community structure was the dominant driver on H₂S emissions. Agents reshaped the compost microbiome, showing more microorganisms participated in sulfur conversion, and enhanced the connection between microorganisms and functional genes. The relative abundance of keystone species associated with H₂S emissions increased after adding MA. Particularly, the sulfite and sulfate reduction processes were intensified, as evidenced by an increasing in the abundance and pathways cooperation of sat and asrA after MA addition. The outcome provides deeper insights into MA on regulating the mitigation of H₂S emissions in compost.

Phosphorus transformation behavior and phosphorus cycling genes expression in food waste composting with hydroxyapatite enhanced by phosphate-solubilizing bacteria

This study aimed to explore the effect of phosphate-solubilizing bacteria (PSB) Bacillus inoculation in the cooling stage on hydroxyapatite dissolution, phosphorus (P) forms transformation, and bacterial P cycling genes in food waste composting with hydroxyapatite. Results indicated that PSB inoculation promoted the dissolution of hydroxyapatite, increased P availability of compost by 8.1% and decreased the ratio of organic P to inorganic P by 10.2% based on sequential fractionation and ³¹P nuclear magnetic resonance spectroscopy. Illumina sequencing indicated Bacillus relative abundance after inoculation increased up to one time higher than control after the cooling stage. Network analysis and metabolic function of bacterial community analysis suggested inorganic P solubilizing genes of Bacillus and organic P mineralization genes of other genera were improved after inoculation in the core module. Therefore, bioaugmentation of PSB in the cooling stage may be a potential way to improve P bioavailability of bone and food waste in composting.

Strong linkage between nutrient-cycling functional gene diversity and ecosystem multifunctionality during winter composting with pig manure and fallen leaves

Microorganisms play important roles in element transformation and display distinct compositional changes during composting. However, little is known about the linkage between nutrient-cycling functional gene diversity and compost ecosystem multifunctionality (EMF). This study performed winter composting with pig manure and fallen leaves and evaluated the distribution patterns and ecological roles of multiple functional genes involved in nutrient cycles. Physicochemical properties and enzyme activities presented large fluctuations during composting. Absolute abundance, composition, and diversity of functional genes participating in carbon, nitrogen, phosphorus, and sulfur cycles presented distinct dynamic changes. Stronger linkage was found between enzyme activities and temperature than other physicochemical factors, whereas total nitrogen rather than other physicochemical factors displayed closer linkage with functional gene composition and diversity. EMF targeting key nutrient (i.e., carbon, nitrogen, phosphorus, and sulfur) cycles was significantly positively correlated with temperature and notably negatively correlated with functional gene diversity. Enzyme activities rather than functional gene diversity showed a greater potential effect on phosphorus availability. Consequently, the available phosphorus (AP) content increased from initial 0.50 g/kg to final 1.43 g/kg. To our knowledge, this is the first study that deciphered ecological roles of nutrient-cycling functional gene diversity during composting, and the final compost can serve as a potential phosphorus fertilizer.

Insight into application of phosphate-solubilizing bacteria promoting phosphorus availability during chicken manure composting

Understanding ecological roles of phosphate-solubilizing bacteria (PSB) is important to optimize composting systems. Illumina MiSeq sequencing, gene quantitation, and statistical analyses were employed to explore ecological mechanisms underlying available phosphorus (AP) facilitation during composting with the inoculation of PSB Pseudomonas sp. WWJ-22. Results displayed that the inoculation of PSB significantly increased AP from 0.83 to 1.23 g kg^-1, and notably increased abundances of phosphorus-cycling genes as well as numbers of PSB mineralizing phytate and lecithin. The PSB addition significantly affected compost bacterial community composition, and phosphorus factions and phosphorus-cycling genes independently explained 25.4 % and 25.0 % bacterial compositional dissimilarity. Stochastic and homogenizing processes affected more on bacterial community assembly, and rare bacteria potentially mediated organic phosphorus mineralization. These results emphasized that phosphorus fractions, PSB number, phosphorus-cycling gene abundance, and bacterial community composition contributed differently to phosphorus availability. Findings highlight ecological roles of exogenous PSB during chicken manure composting.

Co-composting of cattle manure and wheat straw covered with a semipermeable membrane: organic matter humification and bacterial community succession

Semipermeable membrane-covered composting is one of the most commonly used composting technologies in northeast China, but its humification process is not yet well understood. This study employed a semipermeable membrane-covered composting system to detect the organic matter humification and bacterial community evolution patterns over the course of agricultural waste composting. Variations in physicochemical properties, humus composition, and bacterial communities were studied. The results suggested that membrane covering improved humic acid (HA) content and degree of polymerization (DP) by 9.28% and 21.57%, respectively. Bacterial analysis indicated that membrane covering reduced bacterial richness and increased bacterial diversity. Membrane covering mainly affected the bacterial community structure during thermophilic period of composting. RDA analysis revealed that membrane covering may affect the bacterial community by altering the physicochemical properties such as moisture content. Correlation analysis showed that membrane covering activated the dominant genera Saccharomonospora and Planktosalinus to participate in the formation of HS and HA in composting, thus promoting HS formation and its structural complexity. Membrane covering significantly reduced microbial metabolism during the cooling phase of composting.

Phosphorus functional microorganisms and genes: A novel perspective to ascertain phosphorus redistribution and bioavailability during copper and tetracycline-stressed composting

There is limited information on the phosphorus availability under copper and tetracycline-amended composting: Insights into microbial communities and genes. Thus, this work investigated the phosphorus redistribution and transformation, illustrated the variation in microbial communities and genes, and ascertained the multiple action-patterns among which within copper and tetracycline-amended composting. Phosphorus bioavailability reduced by 8.96 % ∼ 13.10 % due to the conservation of Ex-P to Ca-P. Copper and tetracycline showed a significant effect on fungal succession, but not to bacteria, as well as inhibited the phosphorus functional genes in fungal communities, while accelerated it in bacterial communities. Under the copper/tetracycline-stressed conditions, bacterial Firmicutes could promote the mineralization of organic phosphorus, and bacterial Proteobacteria might facilitate the dissolution of inorganic phosphorus. These findings could provide theoretical guidance for the further research on phosphorus bioavailability ascribed to microbial communities and genes.

Rare alkaline phosphatase-harboring bacteria mediate organic phosphorus mineralization during swine manure composting

Deciphering ecological functions of alkaline phosphatase (phoD)-harboring bacteria in composting systems is crucial but poorly understood. High-throughput sequencing, gene quantification, and statistical analyses were applied to investigate effects of abundance and diversity of phoD-harboring bacteria (PHB) on phosphorus availability during swine manure composting. Results showed that available phosphorus notably increased from 0.5 to 1.43 g kg^-1, and physicochemical properties and enzyme activities affected PHB community composition. Phylogenetic signals of PHB responded notably to temperature and phosphorus components, and stochasticity (94.2 %) dominated community assembly. Abundance and diversity of PHB directly and indirectly influenced phosphorus availability, and rare PHB mediated organic phosphorus mineralization. A phosphate-solubilizing bacterium (PSB) Pseudomonas sp. WWJ-22 isolated from compost displayed good efficiency in mineralizing lecithin, demonstrating the highest phosphorus-solubilizing level of 116.3 mg L^-1. This study highlights ecological roles of PHB on phosphorus availability and provides a potential PSB candidate for composting.

Insight into the dynamic microbial community and core bacteria in composting from different sources by advanced bioinformatics methods

Microbial communities are important for high composting efficiency and good quality composts. This study was conducted to compare the changes of physicochemical and bacterial characteristics in composting from different raw materials, including chicken manure (CM), duck manure (DM), sheep manure (SM), food waste (FW), and vegetable waste (VW). The role and interactions of core bacteria and their contribution to maturity in diverse composts were analyzed by advanced bioinformatics methods combined sequencing with co-occurrence network and structural equation modeling (SEM). Results indicated that there were obviously different bacterial composition and diversity in composting from diverse sources. FW had a low pH and different physiochemical characteristics compared to other composts but they all achieved similar maturity products. Redundancy analysis suggested total organic carbon, phosphorus, and temperature governed the composition of microbial species but key factors were different in diverse composts. Network analysis showed completely different interactions of core bacterial community from diverse composts but Thermobifida was the ubiquitous core bacteria in composting bacterial network. Sphaerobacter and Lactobacillus as core genus were presented in the starting mesophilic and thermophilic phases of composting from manure (CM, DM, SM) and municipal solid waste (FW, VW), respectively. SEM indicated core bacteria had the positive, direct, and the biggest (> 80%) effects on composting maturity. Therefore, this study presents theoretical basis to identify and enhance the core bacteria for improving full-scale composting efficiency facing more and more organic wastes.

Potential utilization of vitamin C industrial effluents in agriculture: Soil fertility and bacterial community composition

The potential of industrial effluents from vitamin C (VC) production was assessed for agricultural applications by monitoring plant growth, soil properties, and microbial community structure. The results demonstrated that two types of effluents-residue after evaporation (RAE) and concentrated bacterial solution after ultrafiltration (CBS)-had positive effects on the yield and VC content of pak choi. The highest yield and VC content were achieved with a combined RAE-CBS treatment (55.82 % and 265.01 % increase, respectively). The soil fertility was also enhanced by the application of RAE and CBS. Nitrate nitrogen and organic carbon contents in the soil were positively correlated with the RAE addition, while ammonium nitrogen and available phosphorus were positively correlated with the CBS addition. The diversity of bulk and rhizosphere soil bacterial communities increased significantly after the addition of RAE-CBS. The abundance of Sphingomonas and Rhizobium significantly increased after the RAE-CBS treatment, which affected aromatic compound hydrolysis and nitrogen fixation positively. Changes in plant growth and soil fertility were closely related to the upregulation of functional gene expression related to C, N, and P cycling. RAE and CBS application exerted various positive synergistic effects on plant growth, soil fertility, and bacterial community structure. Consequently, the study results confirmed the potential of RAE and CBS application in agriculture. This study provides an innovative solution for utilizing VC industrial wastewater in agriculture in a resourceful and economically beneficial manner while alleviating the corresponding environmental burden.

Phytotoxicity of farm livestock manures in facultative heap composting using the seed germination index as indicator

Static facultative heap composting of animal manure is widely used in China, but there is almost no systematic research on the phytotoxicity of the produced compost. Here, we evaluated the phytotoxic variation in compost produced by facultative heap composting of four types of animal manure (chicken manure, pig manure, sheep manure, and cattle manure) using different plant seeds (cucumber, radish, Chinese cabbage, and oilseed rape) to determine germination index (GI). The key factors that affected GI values were identified, including the dynamics of the phytotoxicity and microbial community during heap composting. Sensitivity to toxicity differed depending on the type of plant seed used. Phytotoxicity during facultative heap composting, evaluated by the GI, was in the order: chicken manure (0-6.6 %) < pig manure (14.4-90.5 %) < sheep manure (46.0-93.0 %) < cattle manure (50.2-105.8 %). Network analysis showed that the volatile fatty acid (VFA) concentration was positively correlated with Firmicutes abundance, and NH₄⁺-N was correlated with Actinobacteria, Proteobacteria, and Bacteroidetes. More bacteria were stimulated to participate in conversions of dissolved organic carbon, dissolved nitrogen, VFA, and ammonia-nitrogen (NH₄⁺-N) in sheep manure heap composting than that in other manure. The GI was most affected by VFA in chicken manure and cattle manure heap composting, while NH₄⁺-N was the main factor affecting the GI in pig manure and sheep manure compost. The dissolved carbon and nitrogen content and composition, as well as the core and proprietary microbial communities, were the primary factors that affected the succession of phytotoxic substances in facultative heap composting, which in turn affected GI values. In this study, the key pathways of livestock manure composting that affected GI and phytotoxicity were found and evaluated, which provided new insights and theoretical support for the safe use of organic fertilizer.

Impact of aeration rate on phosphorus conversion and bacterial community dynamics in phosphorus-enriched composting

This study was to investigate the effects of different aeration rates on phosphorus (P) conversion and bacterial community dynamics in P-enriched composting by 16S rRNA gene sequencing, sequential P fractionation, network analysis and structural equation model (SEM). Results indicated that Olsen P content increased by 138 %, 150 %, 121 % after composting with aeration rate (L kg-1 DM min-1) at 0.2 (AR0.2), 0.4 (AR0.4) and 0.6 (AR0.6). AR0.4 was more conducive to enhance P solubilization efficacy and available P accumulation. Redundancy analysis indicated Lactobacillus, Spartobacteria and Pseudomonas were key bacteria associated with HCl-Pi especially in AR0.2 and AR0.4. Network analysis showed that increased aeration rate enhanced the connection and function homoplasy among modules and AR0.4 had more orderly community organization for key bacteria to solubilize P in directly and indirectly biotic way. SEM suggested indirectly biotic P-solubilization had more contribution than directly biotic way mainly by phosphate-solubilizing bacteria.

Insights into enzyme activity and phosphorus conversion during kitchen waste composting utilizing phosphorus-solubilizing bacterial inoculation

The main objective of this research was to investigate the effects of Phosphorus-Solubilizing Bacterial (PSB) inoculant on the bacterial structure and phosphorus transformation during kitchen waste composting. High throughput sequencing, topological roles, and multiple analysis methods were conducted to explain the links between phosphorus fractions, enzyme contents, and microbial community structure and function. The findings indicated that bacterial inoculant improved environmental parameters and increased the concentration of total phosphorus, Olsen phosphorus, citric acid phosphorus, OM decomposition, and bacterial diversity. Network analysis concluded that the inoculation treatment was more complex (nodes and edges) and contained more positive links than the control, implying the inoculation effect. The structural equation model also displayed that pH and enzyme activity directly enhanced the phosphorus conversion and bacterial structure. Overall, these results suggest that bacterial inoculation may considerably increase enzyme activity, thus improving biological phosphorus transformation and nutrient content in composting products.

Aspergillus niger Enhances Organic and Inorganic Phosphorus Release from Wheat Straw by Secretion of Degrading Enzymes and Oxalic Acid

To explore the mechanisms of crop straw degradation and phosphorus (P) release by phosphate-solubilizing fungi (PSF), a typical PSF Aspergillus niger (A. niger, ANG) was investigated for the degradation of wheat straw (WST) in this work. The results revealed that A. niger significantly increased wheat straw degradation (30%) compared with no A. niger treatment (7.7%). Meanwhile, more than 92% of total P was released from WST by A. niger, much higher than from WST treatment (69.5%). Although the ratios of inorganic P release between WST and WST + ANG treatments were similar (17.6 vs 19.7%), a significant difference occurred between their release of organic P, i.e., WST (51.9%) vs WST + ANG (72.5%). The high enzyme activity of β-1,4-glucanase and β-glucosidase produced by A. niger contributed to the wheat straw degradation and organic P release compared with no A. niger treatment. Oxalic acid secreted by A. niger dominated the release of inorganic P from WST. Our findings suggested that A. niger is an efficient microbial agent for crop straw degradation and P release, which could be a candidate in the pathway of straw return.

Effects of two types nitrogen sources on humification processes and phosphorus dynamics during the aerobic composting of spent mushroom substrate

Aerobic composting is increasingly regarded as a promising technology for the recycling of spent mushroom substrate (SMS), and an applicable nitrogen source is necessary to improve the process. This study is the first to investigate the effects of protein-like N source (chicken manure, CM) and high-N source (urea, UR) on humification process and P dynamics during SMS composting. The effect of different N sources on microbial succession was also studied. Results showed that CM addition achieved a longer thermophilic phase (16 d vs 9 d), greater germination indices (131.6% vs 106.3%), and higher total phosphorus content (13.1 g/kg vs 6.56 g/kg) in the end products, as compared to UR. The addition of CM showed beneficial effects on humification and stabilization, including decreased weight loss and fluctuations in the level of functional groups. The P produced in the compost was interconverted and leached in the P pool. In this case, the P detected in the compost was in the form of orthophosphate and MgNH₄PO₄⋅6H₂O crystal as inorganic P and orthophosphate monoester as organic P. The most abundant microorganisms at the phylum level mainly include Firmicutes, Actinobacteria, and Proteobacteria, accounting for more than 88% of the total microorganisms. The addition of CM to SMS compost resulted in higher organic matter degradation rates. This work clarified the role of various N sources in SMS composting and presented an appropriate waste management method beneficial to bioresource technology and sustainable development of the edible fungi business.

Effects of exogenous cellulose-degrading bacteria on humus formation and bacterial community stability during composting

This study aimed to reveal the potential mechanism of influence exogenous cellulose-degrading bacteria (ECDB) exerted on humus synthesis during the co-composting of corn straw and cattle manure. By measuring the changes in physicochemical factors and bacterial communities, it was revealed that inoculation with ECDB enhanced the driving force of cellulose degradation and humus synthesis. ECDB not only directly participated in cellulose degradation as degrading bacteria, but also changed the bacterial community succession, and increased the abundance of bacterial communities associated with cellulose degradation. The results showed that ECDB stimulated the potential functions and interactions of bacterial communities. Structural equation modeling confirmed that ECDB acted mainly as a bioactivator to promote humus formation in co-composting of corn straw and cattle manure. Taken together, these findings offered new strategies which can be effectively utilized to increase the efficiency and quality of corn straw composting.

Microbial mechanism of zinc fertilizer input on rice grain yield and zinc content of polished rice

Zinc is an essential minor element for rice growth and human health, which can also change the structure of the microorganisms. However, it remains unclear for the effects of zinc fertilizer on microbiome function in agricultural soils and crops. To solve this research gap, we investigated the relationship between improving rice (Oryza sativa L.) yield, Zn concentration, soil microbial community diversity, and function by the application of Zn fertilizer. The field trials included three rice varieties (Huanghuazhan, Nanjing9108, and Nuodao-9925) and two soil Zn levels (0 and 30 kg ha^-1) in Jiangsu province, China. As a test, we studied the variety of soil bacterial composition, diversity, and function using 16S rRNA gene sequencing. The results showed that soil Zn application reduced the diversity of microbial community, but the bacterial network was more closely linked, and the metabolic function of bacterial community was improved, which increased the grain yield (17.34-19.52%) and enriched the Zn content of polished rice (1.40-20.05%). Specifically, redundancy analysis (RDA) and Mantel's test results revealed soil total nitrogen (TN) was the primary driver that led to a community shift in the rice rhizosphere bacterial community, and soil organic carbon (SOC) was considered to have a strong influence on dominant phyla. Furthermore, network analysis indicated the most critical bacterial taxa were identified as Actinobacteria, Bacteroidetes, Proteobacteria, and Chloroflexi based on their topological roles of microorganisms. KEGG metabolic pathway prediction demonstrated that soil Zn application significantly (p < 0.05) improved lipid metabolism, amino acid metabolism, carbohydrate metabolism, and xenobiotic biodegradation. Overall, their positive effects were different among rice varieties, of which Nanjing-9108 (NJ9108) performed better. This study opens new avenues to deeply understand the plant and soil-microbe interactions by the application of fertilizer and further navigates the development of Zn-rich rice cultivation strategies.

Succession and change of potential pathogens in the co-composting of rural sewage sludge and food waste

Composting is an effective way to prevent and control the spread of pathogenic microorganisms which could put potential risk to humans and environment, from rural solid waste, especially sewage sludge and food waste. In the study, we aim to analyze the changes of pathogenic bacteria during the co-composting of rural sewage sludge and food waste. The results showed that only 27 pathogenic bacteria were detected after composting, compared to 50 pathogenic bacteria in the raw mixed pile. About 74% of pathogen concentrations dropped below 1000 copies/g after composting. Lactobacillus, Bacillus, Paenibacillus and Comamonas were the core pathogenic bacteria in the compost, of which concentrations were all significantly lower than that in the raw mixed pile at the end of composting. The concentration of Lactobacillus decreased to 3.03 × 10³ copies/g compared to 0 d with 1.25 × 10⁹ copies/g by the end of the composting, while that of Bacillus, Paenibacillus and Comamonas decreased to 2.77 × 10⁴ copies/g, 2.13 × 10⁴ copies/g and 3.38 × 10² copies/g, respectively, with 1.26 × 10⁷ copies/g, 4.71 × 10⁶ copies/g, 1.69 × 10⁸ copies/g on 0 d. Redundancy analysis (RDA) indicated that physicochemical factors and substances could affect the changes of pathogenic bacteria during composting, while temperature was the key influencing factor. In addition, certain potential pathogenic bacteria, such as Bacteroides-Bifidobacterium, show statistically strong and significant co-occurrence during composting, which may increase the risk of multiple infections and also influence their distribution. These findings provide a theoretical reference for biosafety prevention and control in the treatment and disposal of rural solid waste.

Effect of micronutrient selenium on greenhouse gas emissions and related functional genes during goat manure composting

To explore the effect of microelement selenium on greenhouse gas emission, nitrogen loss and related functional genes during the composting. Selenite and selenate were respectively mixed with goat manure and wheat straw and then composted the mixture without selenium regarded as control. The results indicated adding selenite prolonged the thermophilic phase and improved the organic matter degradation, while the selenate presented the opposite results. Selenite and selenate influenced ammonium transformation while prompting the formation of nitrate. Compared to the control, adding selenite and selenate both decreased NH₃ emissions (by 26.7%-53.1%) and increased the total nitrogen content of compost. The addition of selenium increased mcrA in the early phase of composting, thereby promoting CH₄ emission (by 3.5-18.4%). Meanwhile, adding selenate significantly reduced nirK abundance and consequently reduced N₂O emission. Moreover, selenate added treatment presented the highest compost maturity (88.77%) and the lowest global warm potential (117.46 g/kg CO₂-eq.) among all treatments.

Improving the humification and phosphorus flow during swine manure composting: A trial for enhancing the beneficial applications of hazardous biowastes

Improving the recovery of organic matter and phosphorus (P) from hazardous biowastes such as swine manure using acidic substrates (ASs) in conjunction with aerobic composting is of great interest. This work aimed to investigate the effects of ASs on the humification and/or P migration as well as on microbial succession during the swine manure composting, employing multivariate and multiscale approaches. Adding ASs, derived from wood vinegar and humic acid, increased the degree of humification and thermal stability of the compost. The ³¹P nuclear magnetic resonance spectroscopy and X-ray absorption near-edge structure analyses demonstrated compost P was in the form of struvite crystals, Ca/Al-P phases, and Poly-P (all inorganic P species) as well as inositol hexakisphosphate and Mono-P (organophosphorus species). However, the efficiency of P recovery could be improved by generating more struvite by adding the ASs. The flows among nutrient pools resulted from the diversity in the dominant microbial communities in different composting phases after introducing the ASs and appearance of Bacillus spp. in all phases. These results demonstrate the potential value of ASs for regulating and/or improving nutrients flow during the composting of hazardous biowastes for producing higher quality compost, which may maximize their beneficial benefits and applications.

Impact of inoculation and turning for full-scale composting on core bacterial community and their co-occurrence compared by network analysis

Window composting with inoculation or frequent turning is a superior way to improve traditional composting efficiency. However, the relationship between the innocent treatment in composting with inoculation or turning and microbial dynamics is unclear. Here, the impact of inoculation and turning for full scale composting on core bacterial community and their co-occurrence network as well as harmless level were compared by network analysis. Results showed that composts with both inoculation and turning had 46% increase of total organic carbon degradation compared to traditional composting and decreased the abundance of potential pathogens. The relative abundance of thermophilic bacteria and Galbibacter, Methylocaldum, Steroidobacter, etc. increased during composting with turning and inoculation. Luteimonas, Sphaerobacter, Turicibacter and Flavobacterium as core bacteria had significant difference between control and composting with enhanced innocent treatment efficiency. Network analysis suggested that turning increased the number of indigenous core bacteria and inoculation enhanced the interaction among key bacterial network.

Response and Dynamic Change of Microbial Community during Bioremediation of Uranium Tailings by Bacillus sp

Bacillus sp. is widely used in the remediation of uranium-contaminated sites. However, little is known about the competitive process of microbial community in the environment during bioremediation. The bioremediation of uranium tailings using Bacillus sp. was explored, and the bacterial community was analyzed by high-throughput sequencing at different stages of remediation. Bacillus sp. reduced the leaching of uranium from uranium tailings. The lowest uranium concentration was 17.25 μg/L. Alpha diversity revealed that the abundance and diversity of microorganisms increased with the extension of the culture time. The microbial abundance and diversity were higher in the treatment group than in the control group. The dominant species at the phyla level were Firmicutes and Proteobacteria in the uranium tailings environment, whereas the phylum of Proteobacteria was significantly increased in the treatment group. Based on the genus level, the proportions of Arthrobacter, Rhodococcus and Paenarthrobacter decreased significantly, whereas those of Clostridium sp., Bacillus and Pseudomonas increased dramatically. Hence, the remediation of uranium contamination in the environment was due to the functional microorganisms, which gradually became the dominant strain in the treatment, such as Desulfotomaculum, Desulfosporporosinus, Anaerocolumna, Ruminiclostridium and Burkholderia. These findings provided a promising outlook of the potential for remediation strategies of soil contaminated by uranium. The dynamic characteristics of the microbial community are likely to provide a foundation for the bioremediation process in practice.