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Abstract Background Tendon-ligament injuries (TLIs), including Achilles tendinopathy, cruciate ligament injury, tennis elbow, rotator cuff injury, patellar tendinopathy, and tibial tendinopathy, are common musculoskeletal soft injuries during physical activity. Matrix metalloproteinase-3 (MMP-3) gene polymorphisms have been implicated in the etiology of TLIs in several genetic association studies with inconsistent results. The purpose of this study was to collect and synthesize the current evidences on the association of MMP-3 polymorphisms and TLIs. Methods The search was conducted using PubMed, Web of Science, EMBASE, Cochrane Library, CNKI and Wanfang databases, prior to July, 2021. Newcastle Ottawa Scale was used to appraise the study quality. Strengths of association were represented by odds ratios (ORs) and 95% confidence intervals (95% CIs). Results Thirteen studies with 2871 cases and 4497 controls met the eligibility criteria, and each study was in high quality. The overall analyzes suggested rs3025058 was associated with an increased TLIs risk (5A vs. 6A, OR = 1.20, 95% CI 1.03–1.40, P = 0.020). However, the association was not found for rs679620, rs591058, and rs650108 polymorphisms. Subgroup analysis by injury type suggested that rs679620 polymorphism was associated with a reduced risk to Achilles tendon rupture (AA + AG vs. GG, OR = 0.46, 95% CI 0.25–0.87, P = 0.020), and rs3025058 was associated with an elevated risk to anterior cruciate ligament injury (5A5A + 5A6A vs. 6A6A, OR = 1.46, 95% CI 1.03–2.06, P = 0.030). When stratified by ethnicity, the findings indicated that rs3025058 polymorphism was associated with an increased TLIs risk among Caucasians (5A6A vs. 6A6A, OR = 1.55, 95% CI 1.09–2.42, P = 0.020) and Brazilians (5A5A vs. 5A6A + 6A6A, OR = 2.80, 95% CI 1.44–5.45, P = 0.002). Conclusion Findings of this study suggest that rs679620 polymorphism is associated with a reduced Achilles tendon rupture risk, and rs3025058 polymorphism contributes to an increased TLIs risk in Caucasians and Brazilians. However, rs591058 and rs650108 polymorphisms do not show any association with TLIs.

Antler is a kind of natural biological material that is an important weapon for attack and defense and has good strength and excellent toughness. Synchrotron radiation computed tomography technology was adopted in this paper to continuously observe the deformation and failure process of the internal microstructure of antlers during the tensile process. The corresponding full-field strain and evolution of information of the internal structure were quantitatively analyzed combined with digital volume correlation technology. In the experiment, a large quantity of internal canals and lacunae with various shapes and sizes, forming a complex 3D spatial arrangement in antlers, were observed. While realizing the overall lightweight design of the structure, these pore structures can also implement a decrease in local strain concentration and block the long-distance propagation of the high strain concentration region through their cooperation and respective advantages. In addition, there are special high shear strain distribution regions in the antler, which guide the frequent deflection and stepped expansion of cracks, thus playing an important role in the excellent load-bearing capacity and energy dissipation of the antler. These results have positive guiding significance for the lightweight design and performance optimization of artificial porous materials.

Recently, deep neural network-based image compressed sensing methods have achieved impressive success in reconstruction quality. However, these methods (1) have limitations in sampling pattern and (2) usually have the disadvantage of high computational complexity. To this end, a fast multi-scale generative adversarial network (FMSGAN) is implemented in this paper. Specifically, (1) an effective multi-scale sampling structure is proposed. It contains four different kernels with varying sizes so that decompose, and sample images effectively, which is capable of capturing different levels of spatial features at multiple scales. (2) An efficient lightweight multi-scale residual structure for deep image reconstruction is proposed to balance receptive field size and computational complexity. The key idea is to apply smaller convolution kernel sizes in the multi-scale residual structure to reduce the number of operations while maintaining the receptive field. Meanwhile, the channel attention structure is employed for enriching useful information. Moreover, perceptual loss is combined with MSE loss and adversarial loss as the optimization function to recover a finer image. Numerous experiments show that our FMSGAN achieves state-of-the-art image reconstruction quality with low computational complexity.

The unique proline isomerase Pin1 is pivotal for protecting against age-dependent neurodegeneration in Alzheimer's disease (AD), with its inhibition providing a molecular link between tangle and plaque pathologies. Pin1 is oxidatively modified in human AD brains, but little is known about its regulatory mechanisms and pathological significance of such Pin1 modification. In this paper, our determination of crystal structures of oxidized Pin1 reveals a series of Pin1 oxidative modifications on Cys113 in a sequential fashion. Cys113 oxidization is further confirmed by generating antibodies specifically recognizing oxidized Cys113 of Pin1. Furthermore, Pin1 oxidation on Cys113 inactivates its catalytic activity in vitro, and Ala point substitution of Cys113 inactivates the ability of Pin1 to isomerize tau as well as to promote protein turnover of tau and APP. Moreover, redox regulation affects Pin1 subcellular localization and Pin1-mediated neuronal survival in response to hypoxia treatment. Importantly, Cys113-oxidized Pin1 is significantly increased in human AD brain comparing to age-matched controls. These results not only identify a novel Pin1 oxidation site to be the critical catalytic residue Cys113, but also provide a novel oxidative regulation mechanism for inhibiting Pin1 activity in AD. These results suggest that preventing Pin1 oxidization might help to reduce the risk of AD.

The effective elimination of aromatic compounds from wastewater is imperative for safeguarding the ecological environment. Bioelectrochemical processes that combine cathodic reduction and anodic oxidation represent a promising approach for the biomineralization of aromatic compounds. However, conventional direct current bioelectrochemical methods have intrinsic limitations. In this study, a low-frequency and low-voltage alternating current (LFV-AC)-driven bioelectrode offering periodic in situ coupling of reduction and oxidation processes was developed for the biomineralization of aromatic compounds, as exemplified by the degradation of alizarin yellow R (AYR). LFV-AC stimulated biofilm demonstrated efficient bidirectional electron transfer and oxidation–reduction bifunctionality, considerably boosting AYR reduction (63.07% ± 1.91%) and subsequent mineralization of intermediate products (98.63% ± 0.37%). LFV-AC stimulation facilitated the assembly of a collaborative microbiome dedicated to AYR metabolism, characterized by an increased abundance of functional consortia proficient in azo dye reduction (Stenotrophomonas and Bradyrhizobium), aromatic intermediate oxidation (Sphingopyxis and Sphingomonas), and electron transfer (Geobacter and Pseudomonas). The collaborative microbiome demonstrated a notable enrichment of functional genes encoding azo- and nitro-reductases, catechol oxygenases, and redox mediator proteins. These findings highlight the effectiveness of LFV-AC stimulation in boosting azo dye biomineralization, offering a novel and sustainable approach for the efficient removal of refractory organic pollutants from wastewater.

Abstract Background Microbial anaerobic metabolism is a key driver of biogeochemical cycles, influencing ecosystem function and health of both natural and engineered environments. However, the temporal dynamics of the intricate interactions between microorganisms and the organic metabolites are still poorly understood. Leveraging metagenomic and metabolomic approaches, we unveiled the principles governing microbial metabolism during a 96-day anaerobic bioreactor experiment. Results During the turnover and assembly of metabolites, homogeneous selection was predominant, peaking at 84.05% on day 12. Consistent dynamic coordination between microbes and metabolites was observed regarding their composition and assembly processes. Our findings suggested that microbes drove deterministic metabolite turnover, leading to consistent molecular conversions across parallel reactors. Moreover, due to the more favorable thermodynamics of N-containing organic biotransformations, microbes preferentially carried out sequential degradations from N-containing to S-containing compounds. Similarly, the metabolic strategy of C18 lipid-like molecules could switch from synthesis to degradation due to nutrient exhaustion and thermodynamical disadvantage. This indicated that community biotransformation thermodynamics emerged as a key regulator of both catabolic and synthetic metabolisms, shaping metabolic strategy shifts at the community level. Furthermore, the co-occurrence network of microbes-metabolites was structured around microbial metabolic functions centered on methanogenesis, with CH4 as a network hub, connecting with 62.15% of total nodes as 1st and 2nd neighbors. Microbes aggregate molecules with different molecular traits and are modularized depending on their metabolic abilities. They established increasingly positive relationships with high-molecular-weight molecules, facilitating resource acquisition and energy utilization. This metabolic complementarity and substance exchange further underscored the cooperative nature of microbial interactions. Conclusions All results revealed three key rules governing microbial anaerobic degradation. These rules indicate that microbes adapt to environmental conditions according to their community-level metabolic trade-offs and synergistic metabolic functions, further driving the deterministic dynamics of molecular composition. This research offers valuable insights for enhancing the prediction and regulation of microbial activities and carbon flow in anaerobic environments. Video Abstract

Polyethylene terephthalate (PET), one of the most ubiquitous engineering plastics, presents both environmental challenges and opportunities for carbon neutrality and a circular economy. This review comprehensively addressed the latest developments in biotic and abiotic approaches for PET recycling/upcycling. Biotically, microbial depolymerization of PET, along with the biosynthesis of reclaimed monomers [terephthalic acid (TPA), ethylene glycol (EG)] to value-added products, presents an alternative for managing PET waste and enables CO2 reduction. Abiotically, thermal treatments (i.e., hydrolysis, glycolysis, methanolysis, etc.) and photo/electrocatalysis, enabled by catalysis advances, can depolymerize or convert PET/PET monomers in a more flexible, simple, fast, and controllable manner. Tandem abiotic/biotic catalysis offers great potential for PET upcycling to generate commodity chemicals and alternative materials, ideally at lower energy inputs, greenhouse gas emissions, and costs, compared to virgin polymer fabrication. Remarkably, over 25 types of upgraded PET products (e.g., adipic acid, muconic acid, catechol, vanillin, and glycolic acid, etc.) have been identified, underscoring the potential of PET upcycling in diverse applications. Efforts can be made to develop chemo-catalytic depolymerization of PET, improve microbial depolymerization of PET (e.g., hydrolysis efficiency, enzymatic activity, thermal and pH level stability, etc.), as well as identify new microorganisms or hydrolases capable of degrading PET through computational and machine learning algorithms. Consequently, this review provides a roadmap for advancing PET recycling and upcycling technologies, which hold the potential to shape the future of PET waste management and contribute to the preservation of our ecosystems.

In environmental matrices, the migration and distribution of contaminants at water–solid interfaces play a crucial role in their capture or dissemination. Scientists working in environmental remediation and wastewater treatment are increasingly aware of metal–contaminant coordination; however, interfacial behaviors remain underexplored. Here, we show that trivalent metal ions (e.g. Al3+ and Fe3+) mediate the migration of pollutant ligands (e.g. tetracycline (TC) and ofloxacin) to the organic solid interface. In the absence of Al3+, humic acid (HA) colloids (50 mg/L) capture 26.1 % of the TC in water (initial concentration: 10 mg/L) via weak intermolecular interactions (binding energy: −5.71 kcal/mol). Adding Al3+ (2.5 mg/L) significantly enhances the binding of TC to an impressive 94.2 % via Al3+ mediated coordination (binding energy: −84.89 kcal/mol). The significant increase in binding energy results in superior interfacial immobilization. However, excess free Al3+ competes for TC binding via direct binary coordination, as confirmed based on the unique fluorescence of Al3+–TC complexes. Density functional theory calculations reveal the intricate process of HA–Al3+ binding via carboxyl and phenolic hydroxyl sites. The HA–Al3+ flocs then leverage the remaining coordination capacity of Al3+ to chelate with TC. As well as providing insights into the pivotal role of metal ion on the self-purification of natural water bodies, our findings on the interfacial behavior of metal–contaminant coordination will propel coagulation technology to the capture of microscale pollutants.

Anaerobic digestion of waste-activated sludge (WAS) towards biogas recovery is constrained by the limited hydrolysis and inhibited acetogenesis steps that hinder subsequent energy recovery. This study employed Fe(VI)/S(IV) oxidation to enhance the WAS solubilization and coupled it with the syntrophic interaction of hydrogen-producing acetogen (HPA) and sulfate-reducing bacteria (SRB) to stimulate the successive procedure towards methane production. Results showed that the dosage ratio of HPA-SRB to WAS (H-S-W) with 1:1:50 outperformed with the highest methane production potential (11.63 ± 1.87 mL CH4/(g VSS·d). Meanwhile, the efficient and sequential process from acetogenesis to methanogenesis stimulated by HPA-SRB was evidenced by a significant decrease of 30.2% in the acetate concentration. The microbial community structure further manifested the crucial role of HPA-SRB with increased abundance of Desulfobulbus (2.07%), Syntrophomonas (1.24%) and Smithella (1.63%), which stimulated acetophilic methanogen boost with Methanobacterium dominating with 77.51% in H-S-W100. Furthermore, the positive syntrophic relationships among HPA-SRB and acetophilic methanogens towards methane production were confirmed via molecular ecological network and canonical correspondence analysis. This study highlighted the syntrophic cooperation of the mixed consortia of HPA and SRB on methane production based on Fe(VI)/S(IV) pretreatment and provided the theoretical and technical basis for the potential implementation of novel methanogenesis technology for WAS treatment.

Electrode biofilm and planktonic microorganisms are two important parts in bioelectrochemical system, but the mechanism of planktonic microorganisms affect biofilms is not clear. Waste sludge lysate produced from sludge pyrolysis contains melanoidins as complex carbon source that are refractory. Anaerobic digestion companied with weak electrostimulation is adopted to treat the wastewater and explore the mechanism in electron transfer, biofilm activity and microbial community structure. In the presence of planktonic microorganisms, electrode biofilm still plays a major role that about 70% of organics was removed by biofilm, the energy recovery efficiency increased by 10.81%, and the main electron transfer mechanism of biofilm is unchanged, but extra electron transfer pathway (Ef = 0.404 V vs Ag/AgCl) is generated. More cytochrome is produced in biofilm and charge transfer resistance decreases to facilitate electron transfer. The planktonic microorganisms cause more electrochemically active microorganisms and methanogens enrich in the electrode biofilm to enhance the direct interspecies electron transfer.

Carbon cycle regulation and greenhouse gas (GHG) emission abatement within wastewater treatment plants (WWTPs) can theoretically improve sustainability. Currently, however, large amounts of external carbon sources used for deep nitrogen removal and waste sludge disposal aggravate the carbon footprint of most WWTPs. In this pilot-scale study, considerable carbon was preliminarily recovered from primary sludge (PS) through short-term (five days) acidogenic fermentation and subsequently utilized on-site for denitrification in a wool processing industrial WWTP. The recovered sludge-derived carbon sources were excellent electron donors that could be used as additional carbon supplements for commercial glucose to enhance denitrification. Additionally, improvements in carbon and nitrogen flow further contributed to GHG emission abatement. Overall, a 9.1% reduction in sludge volatile solids was achieved from carbon recovery, which offset 57.4% of external carbon sources, and the indirect GHG emissions of the target industrial WWTP were reduced by 8.05%. This study demonstrates that optimizing the allocation of carbon mass flow within a WWTP has numerous benefits.

Maize kernel development is a complex biological process that involves the temporal and spatial expression of many genes and fine gene regulation at a transcriptional and post-transcriptional level, and microRNAs (miRNAs) play vital roles during this process. To gain insight into miRNA-mediated regulation of maize kernel development, a deep-sequencing technique was used to investigate the dynamic expression of miRNAs in the embryo and endosperm at three developmental stages in B73. By miRNA transcriptomic analysis, we characterized 132 known miRNAs and six novel miRNAs in developing maize kernel, among which, 15 and 14 miRNAs were commonly differentially expressed between the embryo and endosperm at 9 days after pollination (DAP), 15 DAP and 20 DAP respectively. Conserved miRNA families such as miR159, miR160, miR166, miR390, miR319, miR528 and miR529 were highly expressed in developing embryos; miR164, miR171, miR393 and miR2118 were highly expressed in developing endosperm. Genes targeted by those highly expressed miRNAs were found to be largely related to a regulation category, including the transcription, macromolecule biosynthetic and metabolic process in the embryo as well as the vitamin biosynthetic and metabolic process in the endosperm. Quantitative reverse transcription-PCR (qRT-PCR) analysis showed that these miRNAs displayed a negative correlation with the levels of their corresponding target genes. Importantly, our findings revealed that members of the miR169 family were highly and dynamically expressed in the developing kernel, which will help to exploit new players functioning in maize kernel development. [ABSTRACT FROM AUTHOR]

Long non-coding RNAs (lncRNAs) have been reported to be involved in the development of maize plant. However, few focused on seed development of maize. Here, we identified 753 lncRNA candidates in maize genome from six seed samples. Similar to the mRNAs, lncRNAs showed tissue developmental stage specific and differential expression, indicating their putative role in seed development. Increasing evidence shows that crosstalk among RNAs mediated by shared microRNAs (miRNAs) represents a novel layer of gene regulation, which plays important roles in plant development. Functional roles and regulatory mechanisms of lncRNAs as competing endogenous RNAs (ceRNA) in plants, particularly in maize seed development, are unclear. We combined analyses of consistently altered 17 lncRNAs, 840 mRNAs and known miRNA to genome-wide investigate potential lncRNA-mediated ceRNA based on "ceRNA hypothesis". The results uncovered seven novel lncRNAs as potential functional ceRNAs. Functional analyses based on their competitive coding-gene partners by Gene Ontology (GO) and KEGG biological pathway demonstrated that combined effects of multiple ceRNAs can have major impacts on general developmental and metabolic processes in maize seed. These findings provided a useful platform for uncovering novel mechanisms of maize seed development and may provide opportunities for the functional characterization of individual lncRNA in future studies. [ABSTRACT FROM AUTHOR]

The human asparaginase-like protein 1 (hASRGL1) is a member of the N-terminal nucleophile (Ntn) family that hydrolyzes l-asparagine and isoaspartyl-dipeptides. The nascent protein folds into an αβ-βα sandwich fold homodimer that cleaves its own peptide backbone at the G167-T168 bond, resulting in the active form of the enzyme. However, biophysical studies of hASRGL1 are difficult because of the curious fact that intramolecular cleavage of the G167-T168 peptide bond reaches only ≤50% completion. We capitalized upon our previous observation that intramolecular processing increases thermostability and developed a differential scanning fluorimetry assay that allowed direct detection of distinct processing intermediates for the first time. A kinetic analysis of these intermediates revealed that cleavage of one subunit of the hASRGL1 subunit drastically reduces the processing rate of the adjacent monomer, and a mutagenesis study showed that stabilization of the dimer interface plays a critical role in this process. We also report a comprehensive analysis of conserved active site residues and delineate their relative roles in autoprocessing and substrate hydrolysis. In addition to glycine, which was previously reported to selectively accelerate hASRGL1 cleavage, we identified several novel small molecule activators that also promote intramolecular processing. The structure-activity analysis supports the hypothesis that multiple negatively charged small molecules interact within the active site of hASRGL1 to act as a base in promoting cleavage. Overall, our investigation provides a mechanistic understanding of the maturation process of this Ntn hydrolase family member. [ABSTRACT FROM AUTHOR]

Ultraviolet photodissociation (UVPD) mass spectrometry (MS) was used to characterize the sequences of proteins in native protein—ligand and protein—protein complexes and to provide auxiliary information about the binding sites of the ligands and protein—protein interfaces. UVPD outperformed collisional induced dissociation (CID), higher-energy collisional dissociation (HCD), and electron transfer dissociation (ETD) in terms of yielding the most comprehensive diagnostic primary sequence information about the proteins in the complexes. UVPD also generated noncovalent fragment ions containing a portion of the protein still bound to the ligand which revealed some insight into the nature of the binding sites of myoglobin/heme, eIF4E/m7GTP, and human peptidyl-prolyl cis—trans isomerase 1 (Pinl) in complex with the peptide derived from the C-terminal domain of RNA polymerase II (CTD). Noncovalently bound protein—protein fragment ions from oligomeric β-lactoglobulin dimers and hexameric insulin complexes were also produced upon UVPD, providing some illumination of tertiary and quaternary protein structural features. [ABSTRACT FROM AUTHOR]

Anaerobic digestion (AD) of organics is a challenging task under high-strength sulfate (SO42−) conditions. The generation of toxic sulfides by SO42−-reducing bacteria (SRB) causes low methane (CH4) production. This study investigated the feasibility of alleviating sulfide inhibition and enhancing CH4 production by using an anaerobic reactor with built-in microbial electrolysis cell (MEC), namely ME-AD reactor. Compared to AD reactor, unionized H2S in the ME-AD reactor was sufficiently converted into ionized HS− due to the weak alkaline condition created via cathodic H2 production, which relieved the toxicity of unionized H2S to methanogenesis. Correspondingly, the CH4 production in the ME-AD system was 1.56 times higher than that in the AD reactor with alkaline-pH control and 3.03 times higher than that in the AD reactors (no external voltage and no electrodes) without alkaline-pH control. MEC increased the amount of substrates available for CH4-producing bacteria (MPB) to generate more CH4. Microbial community analysis indicated that hydrogentrophic MPB (e.g. Methanosphaera) and acetotrophic MPB (e.g. Methanosaeta) participated in the two major pathways of CH4 formation were successfully enriched in the cathode biofilm and suspended sludge of the ME-AD system. Economic revenue from increased CH4 production totally covered the cost of input electricity. Integration of MEC with AD could be an attractive technology to alleviate sulfide inhibition and enhance CH4 production from AD of organics under SO42−-rich condition. Keywords: Anaerobic digestion (AD), Methanogenesis, Sulfate reduction, Microbial electrolysis, Microbial community analysis

The top-down approach to proteomics offers compelling advantages due to the potential to provide complete characterization of protein sequence and post-translational modifications. Here we describe the implementation of 193 nm ultraviolet photodissociation (UVPD) in an Orbitrap mass spectrometer for characterization of intact proteins. Near-complete fragmentation of proteins up to 29 kDa is achieved with UVPD including the unambiguous localization of a single residue mutation and several protein modifications on Pin1 (Q13526), a protein implicated in the development of Alzheimer's disease and in cancer pathogenesis. The 5 ns, high-energy activation afforded by UVPD exhibits far less precursor ion-charge state dependence than conventional collision- and electron-based dissociation methods. [ABSTRACT FROM AUTHOR]

This paper describes the role of α-subunit VISIT-DG sequence residues αSer-347 and αGly-351 in catalytic sites of Escherichia coli F1Fo ATP synthase. X-ray structures show the very highly conserved α-subunit VISIT-DG sequence in close proximity to the conserved phosphate-binding residues αArg- 376, βArg-182, βLys-155, and βArg-246 in the phosphate-binding subdomain. Mutations αS347Q and αG351Q caused loss of oxidative phosphorylation and reduced ATPase activity of F1Fo in membranes by 100- and 150-fold, respectively, whereas αS347A mutation showed only a 13-fold loss of activity and also retained some oxidative phosphorylation activity. The ATPase of αS347Q mutant was not inhibited, and the αS347A mutant was slightly inhibited by MgADP-azide, MgADP-fluoroaluminate, or MgADP-fluoroscandium, in contrast to wild type and αG351Q mutant. Whereas 7-chloro-4-nitrobenzo-2-oxa-1, 3-diazole (NBD-Cl) inhibited wild type and αG351Q mutant ATPase essentially completely, ATPase in αS347A or αS347Q mutant was inhibited maximally by ∼80 -90%, although reaction still occurred at residue βTyr-297, proximal to the α-subunit VISIT-DG sequence, near the phosphate-binding pocket. Inhibition characteristics supported the conclusion that NBD-Cl reacts in βE (empty) catalytic sites, as shown previously by x-ray structure analysis. Phosphate protected against NBD-Cl inhibition in wild type and αG351Q mutant but not in αS347Q or αS347A mutant. The results demonstrate that αSer-347 is an additional residue involved in phosphate-binding and transition state stabilization in ATP synthase catalytic sites. In contrast, αGly-351, although strongly conserved and clearly important for function, appears not to play a direct role. [ABSTRACT FROM AUTHOR]

Bacterial extracellular electron transfer (EET) plays a key role in various natural and engineering processes. Outer membrane c-type cytochromes (OMCs) are considered to be essential in bacterial EET. However, most bacteria do not have OMCs but have redox proteins other than OMCs in their extracellular polymeric substances of biofilms. We hypothesized that these extracellular non-cytochrome c proteins (ENCP) could contribute to EET, especially with the facilitation of electron mediators. This study compared the electrode respiring capacity of wild type Shewanella decolorationis S12 and an OMC-deficient mutant. Although the OMC-deficient mutant was incapable in direct electricity generation in normal cultivation, it regained electricity generation capacity (26% of the wide type) with the aid of extracellular electron mediator (riboflavin). Further bioelectrochemistry and X-ray photoelectron spectroscopy analysis suggested that the ENCP, such as proteins with Fe–S cluster, may participate in the falvin-mediated EET. The results highlighted an important and direct role of the ENCP, generated by either electricigens or other microbes, in natural microbial EET process with the facilitation of electron mediators.

ABSTRACT The processes and mechanisms of community assembly and its relationships to community functioning are central issues in ecology. Both deterministic and stochastic factors play important roles in shaping community composition and structure, but the connection between community assembly and ecosystem functioning remains elusive, especially in microbial communities. Here, we used microbial electrolysis cell reactors as a model system to examine the roles of stochastic assembly in determining microbial community structure and functions. Under identical environmental conditions with the same source community, ecological drift (i.e., initial stochastic colonization) and subsequent biotic interactions created dramatically different communities with little overlap among 14 identical reactors, indicating that stochastic assembly played dominant roles in determining microbial community structure. Neutral community modeling analysis revealed that deterministic factors also played significant roles in shaping microbial community structure in these reactors. Most importantly, the newly formed communities differed substantially in community functions (e.g., H2 production), which showed strong linkages to community structure. This study is the first to demonstrate that stochastic assembly plays a dominant role in determining not only community structure but also ecosystem functions. Elucidating the links among community assembly, biodiversity, and ecosystem functioning is critical to understanding ecosystem functioning, biodiversity preservation, and ecosystem management. IMPORTANCE Microorganisms are the most diverse group of life known on earth. Although it is well documented that microbial natural biodiversity is extremely high, it is not clear why such high diversity is generated and maintained. Numerous studies have established the roles of niche-based deterministic factors (e.g., pH, temperature, and salt) in shaping microbial biodiversity, the importance of stochastic processes in generating microbial biodiversity is rarely appreciated. Moreover, while microorganisms mediate many ecosystem processes, the relationship between microbial diversity and ecosystem functioning remains largely elusive. Using a well-controlled laboratory system, this study provides empirical support for the dominant role of stochastic assembly in creating variations of microbial diversity and the first explicit evidence for the critical role of community assembly in influencing ecosystem functioning. The results presented in this study represent important contributions to the understanding of the mechanisms, especially stochastic processes, involved in shaping microbial biodiversity.