Complex Substrates Research Articles

Habitat‐setting affects biodiversity while predation determines oyster survival on experimental oyster reefs

Foundation species are being restored into inherently variable landscapes with multiple, interspersed habitats. However, understanding of the influence of different neighbouring habitats on community assembly and the survival of restored species is limited, despite their significant potential to affect restoration outcomes. We tested how habitat‐setting (being next to seagrass, seagrass and mangroves, or unvegetated sediments) and predation (by meso‐ and/or large predators) influenced macroinvertebrate community assembly and the survival of juvenile Sydney rock oysters (Saccostrea glomerata) on experimental oyster reef units in the Port Hacking estuary, New South Wales, Australia. Each habitat‐setting produced a distinct macroinvertebrate community on experimental reefs, whereas predation had limited effects on community structure. Juvenile oysters were instead highly predated everywhere, and oyster predation was dominated by the large, transient fish Acanthropagrus australis. Our findings allow practitioners to predict and tailor the communities which establish on restored oyster reefs by strategically placing them next to different habitats. If sites have a high predation risk but require seeding for reefs to establish, then caging or complex substrates must be used to increase seeded oyster survival.

Assessing anaerobic microbial degradation rates of crude light oil with reverse stable isotope labelling and community analysis

Oil reservoirs represent extreme environments where anaerobic degradation profoundly influences oil composition and quality. Despite the common observation of biodegraded oil, the microbial degradation rates remain largely unknown. To address this knowledge gap, we conducted microcosm incubations with light oil as carbon source, original formation water and sulfate as electron acceptor, closely mimicking in situ conditions to assess oil degradation rates. Samples were taken from a newly drilled oil well to exclude contamination with injection water and allochthonous microorganisms. At the end of the incubations, microbial community analyses with 16S rRNA gene amplicon sequencing revealed the most prominent phyla as Desulfobacterota, Thermotogota, Bacteroidota, Bacillota (formerly Firmicutes), and Synergistota, collectively accounting for up to 44% of relative abundance. Ion chromatography and reverse stable isotope labeling were used to monitor sulfate reduction and CO2 evolution respectively. We calculated an average degradation rate of 0.35 mmol CO2 per year corresponding to 15.2 mmol CO2/mol CH2(oil) per year. This resembles to approximately 200 years to degrade one gram of oil under the applied, presumably ideal conditions. Factoring in the available oil-water-contact (OWC) zone within the incubations yielded a degradation rate of 120 g CH2 m−2 OWC per year, closely aligning with the modeled degradation rates typically observed in oil reservoirs. Moreover, our study highlighted the utility of the reverse stable isotope labeling (RSIL) approach for measuring complex substrate degradation at minute rates.

Evaporation-driven interfacial restructuring induces highly efficient methanogenesis of waste biomass

Methanogenesis of waste biomass (WB) is a promising method for global sustainable development, reduction of pollution and carbon emission levels, and recovering bioenergy. Unlike in the methanogenesis of organic wastewater, in which microbial cells come into direct contact with the dissolved substrate, the ‘solid–liquid–solid’ modes in WB and between WB and microbial cells, which involve numerous solid–liquid interfaces, greatly hinder the methanogenesis efficiency of WB. Amongst all WB, waste activated sludge is the most complex, poorly biodegradable and representative. Herein, we highlight the role of water evaporation-driven solid-liquid interfacial restructuring of sludge in determining its methanogenesis efficiency. Non-free water evaporation increased surface roughness and adhesion, and compressed pore structure with numerous capillaries in sludge, resulting in a new solid-liquid interface of sludge with great capillary force and highly ordered interfacial water molecules, which provides an extremely favourable condition for high mass transfer and proton-coupled electron transfer (PCET) in sludge. This restructuring was confirmed to induce the enhancement of solid–liquid interfacial noncovalent interactions and electron transfer efficiency in the subsequent methanogenesis process (P < 0.05), promoting the effective contact between the sludge substrate and microbial cells, thereby enriching the methanogenic consortia (i.e., Clostridia and Methanosarcina were increased by 290.0 % and 239.7 %, respectively) and improving the activities of key enzymes. Stable isotope tracing and metagenomic analysis further reveal that this restructuring promoted the participation of water molecules in the methane formation by PCET-driven release of protons from water, and enhanced main methanogenesis metabolic pathways, especially the metabolic pathway of CO2-reduction methanogenesis (+65.2 %), thereby resulting in a great advance in methane generation (+147 %, P < 0.001). The findings can provide a reference for regulating directional anaerobic biotransformation of water-rich multiphase complex substrates by interfacial restructuring inducement.

Transition-Metal-Free C-N Cross-Coupling Enabled by a Multifunctional Reagent.

We report the design and development of a transition-metal-free cross-coupling reaction of phenols and primary amines using a simple and readily available multifunctional reagent. The reactions work by induced proximity and electronic activation of both the nucleophile and the electrophile for net dehydrative C-N coupling reactions. Notably, the reactions do not involve the use of a transition metal for C-N bond formation, preactivation of the phenol electrophile, or exclusion of air or moisture. The mild conditions tolerate a broad range of functional groups and allow for this to be applied to the late-stage functionalization of complex substrates with a wide scope of coupling partners.

Recent Developments and Applications of Biocatalytic and Chemoenzymatic Synthesis for the Generation of Diverse Classes of Drugs.

Biocatalytic and chemoenzymatic biosynthesis are powerful methods of organic chemistry that use enzymes to execute selective reactions and allow the efficient production of organic compounds. The advantages of these approaches include high selectivity, mild reaction conditions, and the ability to work with complex substrates. The utilization of chemoenzymatic techniques for the synthesis of complicated compounds has lately increased dramatically in the area of organic chemistry. Biocatalytic technologies and modern synthetic methods are utilized synergistically in a multi-step approach to a target molecule under this paradigm. Chemoenzymatic techniques are promising for simplifying access to essential bioactive compounds because of the remarkable regio- and stereoselectivity of enzymatic transformations and the reaction diversity of modern organic chemistry. Enzyme kits may include ready-to-use, reproducible biocatalysts. Its use opens up new avenues for the synthesis of active therapeutic compounds and aids in drug development by synthesizing active components to construct scaffolds in a targeted and preparative manner. This study summarizes current breakthroughs as well as notable instances of biocatalytic and chemoenzymatic synthesis. To assist organic chemists in the use of enzymes for synthetic applications, it also provides some basic guidelines for selecting the most appropriate enzyme for a targeted reaction while keeping aspects like cofactor requirement, solvent tolerance, use of whole cell or isolated enzymes, and commercial availability in mind.

Enhancing short-chain fatty acids production via acidogenic fermentation of municipal sewage sludge: Effect of sludge characteristics and peroxydisulfate pre-oxidation.

This study first employed a combined pretreatment of low-dose peroxy-disulfate (PDS) and initial pH 10 to promote short-chain fatty acids (SCFAs) production via acidogenic fermentation using different types of sewage sludge as substrates. The experimental results showed that the yield of maximal SCFAs and acetate proportion after the combined pretreatment were 1513.82±28.25mg chemical oxygen demand (COD)/L and 53.64%, and promoted by 1.28 and 1.56 times higher, respectively, compared to the sole initial pH 10 pretreatment. Furthermore, in terms of the disintegration degree of sewage sludge, it increased by more than 18% with the combined pretreatment compared to the pretreatment of sole initial pH 10. Waste-activated sludge (WAS) from A2/O and Bardenpho processes were more biodegradable, explained by the 1.47- and 1.35-times higher disintegration rate than those from oxidation ditch and they favored acetate dominant fermentation. Correlation analysis revealed a strong correlation (p ≤ 0.01) between SCFAs production and soluble COD, total proteins, proteins in soluble-extracellular polymeric substances (SEPS), total polysaccharides, and polysaccharides in SEPS. Mechanism explorations showed that preoxidation with PDS enhanced the solubilization and biodegradability of complex substrates, and altered the microbial community structure during the fermentation process. Firmicutes and Tetrasphaera were proven to play a key role in improving SCFA production, especially in promoting acetate production by converting additional SCFAs into acetate. Additionally, the addition of PDS greatly promoted sulfur and iron-related metabolic activities. Finally, the combined pretreatment was estimated to be a cost-effective solution for reutilizing and treating Fe-sludge.

Ultrasensitive SERS quantitative detection of antioxidants via diazo derivatization reaction and deep learning for signal fluctuation mitigation

Synthetic antioxidants serve as essential protectors against oxidation and deterioration of edible oils, however, prudent evaluation is necessary regarding potential health risks associated with excessive intake. The direct adsorption of antioxidants onto conventional surface-enhanced Raman scattering (SERS) substrates is challenging due to the presence of phenolic hydroxyl groups in their molecular structures, resulting in weak Raman scattering signals and rendering direct SERS detection difficult. In this study, a diazo derivatization reaction was employed to enhance SERS signals by converting antioxidant molecules into azo derivatives, enabling the amplification of the weak Raman scattering signals through the strong vibrational modes induced by the N = N double bond. The resulting diazo derivatives were characterized using UV–visible absorption and infrared spectroscopy, confirming the occurrence of diazo derivatization of the antioxidants. The proposed method successfully achieved the rapid detection of three commonly used synthetic antioxidants, namely butylated hydroxyanisole (BHA), tert-butylhydroquinone (TBHQ), and propyl gallate (PG) on interfacial self-assembled gold nanoparticles. Furthermore, rapid predictions of BHA, PG, and TBHQ within the concentration range of 1 × 10−6 to 2 × 10−3 mol/L were achieved by integrating a convolutional neural network model. The predictive range of this model surpassed the traditional quantitative method of manually selecting characteristic peaks, with linear coefficients (R2) of 0.9992, 0.9997, and 0.9997, respectively. The recovery of antioxidants in real soybean oil samples ranged from 73.0 % to 126.4 %. Based on diazo derivatization, the proposed SERS method eliminates the need for complex substrates and enables the analysis and determination of synthetic antioxidants in edible oils within 20 min, providing a convenient analytical approach for quality control in the food industry.

Activation of peroxymonosulfate using heterogeneous Fe-doped carbon-based catalyst to generate singlet oxygen for the degradation of sulfamethoxazole

Non-radical catalytic oxidation processes can eliminate refractory pollutants from wastewater containing complex substrates such as dissolved organic matter, but the production of selective non-radicals is challenging during the activation of peroxymonosulfate (PMS). Herein, a novel magnetic carbon-based catalyst (Fe3O4@CD-8, where 8 represents an annealing temperature of 800 ℃) with N and Fe species as catalytic active sites was fabricated to remediate sulfamethoxazole (SMX)-containing water. It showed excellent SMX removal efficiency and facilitated singlet oxygen (1O2) production. The characterization results revealed that Fe3O4@CD-8 had a microscopically hierarchical pore structure and an overall core–shell-like structure. Due to its large specific surface area, N-containing species, and Fe nanoparticles, 0.1 g/L Fe3O4@CD-8 removed almost 100% SMX (24 min) and achieved a 44.1% mineralization (40 min) efficiency in the presence of 0.5 mM PMS. This catalytic system also maintained its removal performance in the presence of inorganic anions and humic acids and over a wide pH range of 3–11, showing good tolerance to various environmental factors. 1O2 was confirmed to be the predominant active species for SMX degradation using the Fe3O4@CD-8/PMS system. Density functional theory (DFT) calculations, intermediate monitoring, and toxicity evaluation demonstrated that SMX was transformed into low-toxicity molecules and completely mineralized into CO2 and H2O. The addition of Fe nanoparticles enhanced PMS adsorption and facilitated the Fe(III)/Fe(II) redox cycle to accelerate the activation of PMS. This study provides new insights and strategies for the controlled production of non-radicals for remediating antibiotic-containing wastewater.

Sub‐Micron Thickness Self‐Limiting Electrospray Deposition via Voltage Bias of Spray Target

AbstractElectrospray deposition (ESD) is a technique with emerging relevance for applications requiring micro‐/nano‐scaled coatings. Self‐limiting electrospray deposition (SLED) is a regime of ESD where upon satisfying the criteria for self‐limiting behavior, the charge buildup of the material will eventually begin to repel itself until an asymptotic thickness is achieved, based primarily on the properties of the spray solution and deposited material. This work focuses on controlling the coating thickness further to achieve sub‐micron thicknesses. By applying a voltage bias of the same polarity of the spray onto the target substrate while providing a secondary grounded surface, the thickness of a payload can be manipulated for thinner and more precise thicknesses. The magnitude of the voltage bias is varied to show the effect of voltage bias on thickness, and 2‐D and 3‐D structures are used to demonstrate the generality of this technique for complex substrates. The results show how SLED can be included as a potential alternative for conformal coatings deposited at ambient conditions at the sub‐micron scale.

Hydroformylation of Alkynyl Sulfides: A Stereo‐ and Regioselective Route to α‐Sulfenyl Acroleins

AbstractThe rhodium‐catalyzed hydroformylation of alkynyl sulfides at 40 °C under 5 bars of syngas is described. The method gives access to α‐sulfenyl acroleins with α/β regioselectivities up to 89/11 and is applicable to alkyl or aryl substituted substrates. It is effective even on more complex substrates, such as cysteine and cholesterol derivatives. To demonstrate the synthetic potential of the obtained products, (Z)‐3‐cyclohexyl‐2‐methylsulfenyl acrolein was selected as an example and its sulfur atom selectively oxidized to the corresponding sulfoxide or sulfone. Acid‐promoted (Z) to (E) isomerization of the double bond occurred during oxidation. The three obtained sulfenyl‐, sulfinyl‐, and sulfonyl‐functionalized acroleins have been then used as dienophiles to access cyclohexene carbaldehydes.

Pulsed inputs of high molecular weight organic matter shift the mechanisms of substrate utilisation in marine bacterial communities.

Heterotrophic bacteria hydrolyze high molecular weight (HMW) organic matter extracellularly prior to uptake, resulting in diffusive loss of hydrolysis products. An alternative 'selfish' uptake mechanism that minimises this loss has recently been found to be common in the ocean. We investigated how HMW organic matter addition affects these two processing mechanisms in surface and bottom waters at three stations in the North Atlantic Ocean. A pulse of HMW organic matter increased cell numbers, as well as the rate and spectrum of extracellular enzymatic activities at both depths. The effects on selfish uptake were more differentiated: in Gulf Stream surface waters and productive surface waters south of Newfoundland, selfish uptake of structurally simple polysaccharides increased upon HMW organic matter addition. The number of selfish bacteria taking up structurally complex polysaccharides, however, was largely unchanged. In contrast, in the oligotrophic North Atlantic gyre, despite high external hydrolysis rates, the number of selfish bacteria was unchanged, irrespective of polysaccharide structure. In deep bottom waters (> 4000 m), structurally complex substrates were processed only by selfish bacteria. Mechanisms of substrate processing-and the extent to which hydrolysis products are released to the external environment-depend on substrate structural complexity and the resident bacterial community.

Metal-organic-framework-confined quantum dots enhance photocurrent signals: A molecularly imprinted photoelectrochemical cathodic sensor for rapid and sensitive tetracycline detection

BackgroundTetracycline (TC), a cost-effective broad-spectrum antibacterial drug, has been excessively utilized in the livestock and poultry industry, leading to a serious overabundance of TC in livestock wastewater. However, conventional analytical methods such as liquid chromatography and gas chromatography face challenges in achieving sensitive detection of trace amounts of TC in complex substrates. Therefore, it is imperative to develop a highly sensitive and anti-interference analytical method for the detection of tetracycline in livestock wastewater. ResultsA porphyrin-based MOF (PCN-224)-confined carbon dots (CDs) material (CDs@PCN-224) was synthesized by a “bottle-around-ship” strategy. The reduced carrier migration distance is conducive to the separation of electron-hole pairs and enhanced the photocurrent signal due to the tight coupling of CDs and PCN-224. Further, molecularly imprinted polymer (MIP) was synthesized by rapid in-situ UV-polymerization and employed as a recognition element. The specific recognition of the target by imprinted cavities blocks electron transfer, resulting in a “turn off” response signal, thus realizing the selective detection of TC. Under optimal conditions, the constructed MIP-PEC cathodic sensor detected 1.00 × 10−12 M to 1.00 × 10−7 M of TC sensitively, with a limit of detection of 3.72 × 10−13 M. In addition, the proposed MIP-PEC sensor demonstrated good TC detection performance in actual livestock wastewater. SignificanceThe strategy based on MOF pore-confined quantum dots can effectively enhance the photocurrent response of the photosensitive substrate. Simultaneously, the MIP constructed by in-situ rapid UV-polymerization showed excellent anti-interference and reusable properties. This work provides a promising MIP-PEC cathodic sensing method for the rapid and sensitive detection of antibiotics in complex-matrix environmental samples.

Microbial activity of lactic acid bacteria and hydrogen producers mediated by pH and total solids during the consolidated bioprocessing of agave bagasse

Lactic acid bacteria (LAB) coexist with Clostridium spp. in hydrogen production processes from complex substrates; however, the role of LAB is still unclear. This study analyzed the fermentation products in a wide range of initial pH (pHi, 5.5–6.9) and total solids (TS%, 8–22%) to determine the activity of these two microbial groups over time (from 24 to 120 h). Agave bagasse served as the feedstock for hydrogen production via consolidated bioprocess (CBP), while the inoculum source was the indigenous mature microbiota. In the early stage of the CBP, hydrogen production from lactic acid occurred only at pHi ≥ 6.0 (ρ = 0.0004) with no effect of TS%; lactic acid accumulated below this pHi value. In this stage, lactic acid production positively correlated with a first cluster of LAB represented by Paucilactobacillus (r = 0.64) and Bacillus (r = 0.81). After 72 h, hydrogen production positively correlated with a second group of LAB led by Enterococcus (r = 0.71) together with the hydrogen producer Clostridium sensu stricto 1 (r = 0.8) and the acetogen Syntrophococcus (r = 0.52) with the influence of TS% (ρ < 0.0001). A further experiment showed that buffering the pH to 6.5 increased and lengthened the lactic acid production, doubling the hydrogen production from 20 to 41 mL H2/gTSadded. This study confirmed the prevalence of distinct groups of LAB over time, whose microbial activity promoted different routes of hydrogen production.

Helicovermis profundi gen. nov., sp. nov., a novel mesophilic, asporogenous bacterium within the Clostridia isolated from a deep-sea hydrothermal vent chimney.

A novel mesophilic bacterial strain, designated S502T, was isolated from a deep-sea hydrothermal vent at Suiyo Seamount, Japan. Cells were Gram-positive, asporogenous, motile, and curved rods, measuring 1.6-5.6 µm in length. The strain was an obligate anaerobe that grew fermentatively on complex substrates such as yeast extract and Bacto peptone. Elemental sulfur stimulated the growth of the strain, and was reduced to hydrogen sulfide. The strain grew within a temperature range of 10-23°C (optimum at 20°C), pH range of 4.8-8.3 (optimum at 7.4), and a NaCl concentration range of 1.0-4.0% (w/v) (optimum at 3.0%, w/v). Phylogenetic analysis based on the 16S rRNA gene sequence revealed that the isolate was a member of the class Clostridia, with Fusibacter paucivorans strain SEBR 4211T (91.1% sequence identity) being its closest relative. The total size of the genome of the strain was 3.12 Mbp, and a G + C content was 28.2 mol%. The highest values for average nucleotide identity (ANI), average amino acid identity (AAI), and digital DNA-DNA hybridization (dDDH) value of strain S502T with relatives were 67.5% (with Marinisporobacter balticus strain 59.4MT), 51.5% (with M. balticus strain 59.4MT), and 40.9% (with Alkaliphilus serpentinus strain LacTT), respectively. Based on a combination of phylogenetic, genomic, and phenotypic characteristics, we propose strain S502T to represent a novel genus and species, Helicovermis profundi gen. nov., sp. nov., with the type strain S502T (= DSM 112048T = JCM 39167T).

Multicomponent Cyclizative 1,2-Rearrangement Enabled Enantioselective Construction of 2,2-Disubstituted Pyrrolinones.

The 1,2-rearrangement reaction is one of the most important approaches to construct carbon-carbon bonds in organic synthesis. However, the development of catalytic asymmetric 1,2-rearrangements is still far from mature and often suffers from problems such as complex substrates, single product structure, and lack of synthetic application. Multicomponent reaction has been recognized as a robust tool for the synthesis of diverse and tunable products from readily available starting material. Conceptionally and practically, the development of multicomponent asymmetric 1,2-rearrangements is highly desirable. In this regard, we report herein a three-component benzilic acid-type rearrangement of 2,3-diketoesters, aromatic amines and aldehydes for the asymmetric construction of synthetically challenging pyrrolinones bearing aza-quaternary stereocenters. To the best of our knowledge, this reaction represents the first example of organocatalyzed multicomponent asymmetric 1,2-rearrangements.

Multicomponent Cyclizative 1,2‐Rearrangement Enabled Enantioselective Construction of 2,2‐Disubstituted Pyrrolinones

AbstractThe 1,2‐rearrangement reaction is one of the most important approaches to construct carbon‐carbon bonds in organic synthesis. However, the development of catalytic asymmetric 1,2‐rearrangements is still far from mature and often suffers from problems such as complex substrates, single product structure, and lack of synthetic application. Multicomponent reaction has been recognized as a robust tool for the synthesis of diverse and tunable products from readily available starting material. Conceptionally and practically, the development of multicomponent asymmetric 1,2‐rearrangements is highly desirable. In this regard, we report herein a three‐component benzilic acid‐type rearrangement of 2,3‐diketoesters, aromatic amines and aldehydes for the asymmetric construction of synthetically challenging pyrrolinones bearing aza‐quaternary stereocenters. To the best of our knowledge, this reaction represents the first example of organocatalyzed multicomponent asymmetric 1,2‐rearrangements.

Electrochemical Monitoring of Heterogeneous Peroxygenase Reactions Unravels LPMO Kinetics.

Biological conversion of plant biomass depends on peroxygenases and peroxidases acting on insoluble polysaccharides and lignin. Among these are cellulose- and hemicellulose-degrading lytic polysaccharide monooxygenases (LPMOs), which have revolutionized our concept of biomass degradation. Major obstacles limiting mechanistic and functional understanding of these unique peroxygenases are their complex and insoluble substrates and the hard-to-measure H2O2 consumption, resulting in the lack of suitable kinetic assays. We report a versatile and robust electrochemical method for real-time monitoring and kinetic characterization of LPMOs and other H2O2-dependent interfacial enzymes based on a rotating disc electrode for the sensitive and selective quantitation of H2O2 at biologically relevant concentrations. The H2O2 sensor works in suspensions of insoluble substrates as well as in homogeneous solutions. Our characterization of multiple LPMOs provides unprecedented insights into the substrate specificity, kinetics, and stability of these enzymes. High turnover and total turnover numbers demonstrate that LPMOs are fast and durable biocatalysts.

Complex Substrate Leading to PVC-Mediated Systolic Dysfunction in addition to Sustained Monomorphic VT in Repaired Tetralogy of Fallot.

Frequent premature ventricular complexes (PVCs) are associated with deleterious effects on left ventricular (LV) function in various clinical scenarios. Repaired tetralogy of Fallot (rTOF) is frequently affected by sustained ventricular arrhythmias dependent on complex post-surgical substrates. However, there is limited data regarding the potential of arrhythmogenic isthmuses to generate frequent PVCs and PVC-mediated LV systolic dysfunction development in rTOF. We present a case of rTOF experiencing relatively infrequent episodes of internal shocks for episodes of sustained monomorphic ventricular tachycardia and a high burden of PVCs associated with left ventricular systolic function deterioration, in which the successful substrate ablation of the anatomical VT isthmuses also led to PVC abolition and consequently to LV systolic function normalization. In such cases, understanding the pathogenic mechanisms that lead to LV dysfunction is only possible by rigorous clinical reasoning, which leads to a tailored specific treatment.

Acyl homoserine lactone-based regulation strategy for improved methane production in anaerobic digestion of agricultural wastes

The acyl homoserine lactone (AHL)-based regulation strategy presents a considerable potential in improving anaerobic digestion (AD) efficiency of complex substrates. However, the reinforcement mechanisms are still unclear. In this study, the effects of different AHL types (C4-HSL, C7-HSL, C12-HSL) and different adding times (0 d, 5 d, 15 d) on AD performance of agricultural wastes (corn straw and cattle manure) were investigated. The results indicated that all types of AHLs exerted positive effects on AD, and the adding time rather than the AHL type was the key factor affecting AD processes. The C12-5d group obtained the highest accumulated methane production (310.7 ± 2.56 mL/g VS), which increased by 47.71% than that of the Control group. The exogenous AHLs facilitated the hydrolysis and acidification of complex substrates and the utilization of released low-molecular-weight organic acids in AD systems. Furthermore, the role of methanogenic archaea was upregulated and the dominance of bacteria was relatively weakened in AD systems, which favored the establishment of their balanced and symbiotic metabolic relationship. The enriched Methanobacterium strengthened the hydrogenotrophic methanogenesis pathway. This study provides new insights into the regulation strategy of AD for agricultural waste treatment based on AHL addition.

Mechanisms and implications of bacterial-fungal competition for soil resources.

Elucidating complex interactions between bacteria and fungi that determine microbial community structure, composition, and functions in soil, as well as regulate carbon (C) and nutrient fluxes, is crucial to understand biogeochemical cycles. Among the various interactions, competition for resources is the main factor determining the adaptation and niche differentiation between these two big microbial groups in soil. This is because C and energy limitations for microbial growth are a rule rather than an exception. Here, we review the C and energy demands of bacteria and fungi-the two major kingdoms in soil-the mechanisms of their competition for these and other resources, leading to niche differentiation, and the global change impacts on this competition. The normalized microbial utilization preference showed that bacteria are 1.4-5 times more efficient in the uptake of simple organic compounds as substrates, whereas fungi are 1.1-4.1 times more effective in utilizing complex compounds. Accordingly, bacteria strongly outcompete fungi for simple substrates, while fungi take advantage of complex compounds. Bacteria also compete with fungi for the products released during the degradation of complex substrates. Based on these specifics, we differentiated spatial, temporal, and chemical niches for these two groups in soil. The competition will increase under the main five global changes including elevated CO2, N deposition, soil acidification, global warming, and drought. Elevated CO2, N deposition, and warming increase bacterial dominance, whereas soil acidification and drought increase fungal competitiveness.