The extracellular electron transfer (EET) efficiency in bioelectrochemical systems has been proven to be dependent on anode potentials. To explore the underlying mechanism, previous studies have ...mainly focused on EET conduit and bacterial biomass but rarely concerned with the role of extracellular polymeric substances (EPS) surrounding electroactive cells. In this study, the response of Geobacter biofilms to anode potentials was investigated with a special emphasis on the mechanistic role of EPS. The electrochemical activities and cell viabilities of Geobacter soli biofilms were simultaneously attenuated at 0.4 and 0.6 V compared to −0.2 and 0 V. It was found that the biofilms (especially the biofilm region closer to electrode surface) grown at −0.2 and 0 V produced relatively more extracellular redox-active proteins and less extracellular polysaccharides, which conferred higher electron accepting/donating capacities to EPS and consequently facilitated EET. Meanwhile, electrically nonconductive extracellular polysaccharide-dominated interior layers were formed in the biofilms grown at 0.4 and 0.6 V, which limited direct EET but might serve as physical barriers for protecting cells in these biofilms from the increasing stress by poised electrodes. These results demonstrated that the production of EPS under different anode potentials might be finely regulated by cells to keep balance between EET efficiency and cell-protection. This study provides a new insight to investigate the Geobacter biofilms coping with various environments, and is useful for optimizing electrochemical activity of anode biofilms.
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•Highest EET and cell viability observed in biofilms grown at −0.2 and 0 V.•Heterogeneity is elucidated in spatial distribution of both viable cells and EPS.•Electrochemical activity of biofilm is positively related to redox activity of EPS.•Polysaccharide-dominated interior layers of EPS in 0.4 and 0.6 V biofilms hinder EET.
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•Recent research efforts to improve acetate production are summarized.•Future research paths for higher value chemicals production are highlighted.•How to integrate MES with existing ...biochemicals processes is proposed.
Microbial electrosynthesis (MES) is a novel microbial electrochemical technology proposed for chemicals production with the storage of sustainable energy. However, the practical application of MES is currently restricted by the limited low market value of products in one-step conversion process, mostly acetate. A theme that is pervasive throughout this review is the challenges associated with the expanded product spectrum. Several recent research efforts to improve acetate production, using novel reactor configuration, renewable power supply, and various 3-D cathode are summarized. The importance of genetic modification, two-step hybrid process, as well as input substrates other than CO2 are highlighted in this review as the future research paths for higher value chemicals production. At last, how to integrate MES with existing biochemicals processes is proposed. Definitely, more studies are encouraged to evaluate the overall performances and economic efficiency of these integrated process designs to make MES more competitive.
Traumatic brain injury (TBI) is a leading cause of death and disability worldwide. Microglial/macrophage activation and neuroinflammation are key cellular events following TBI, but the regulatory and ...functional mechanisms are still not well understood. Myeloid-epithelial-reproductive tyrosine kinase (Mer), a member of the Tyro-Axl-Mer (TAM) family of receptor tyrosine kinases, regulates multiple features of microglial/macrophage physiology. However, its function in regulating the innate immune response and microglial/macrophage M1/M2 polarization in TBI has not been addressed. The present study aimed to evaluate the role of Mer in regulating microglial/macrophage M1/M2 polarization and neuroinflammation following TBI.
The controlled cortical impact (CCI) mouse model was employed. Mer siRNA was intracerebroventricularly administered, and recombinant protein S (PS) was intravenously applied for intervention. The neurobehavioral assessments, RT-PCR, Western blot, magnetic-activated cell sorting, immunohistochemistry and confocal microscopy analysis, Nissl and Fluoro-Jade B staining, brain water content measurement, and contusion volume assessment were performed.
Mer is upregulated and regulates microglial/macrophage M1/M2 polarization and neuroinflammation in the acute stage of TBI. Mechanistically, Mer activates the signal transducer and activator of transcription 1 (STAT1)/suppressor of cytokine signaling 1/3 (SOCS1/3) pathway. Inhibition of Mer markedly decreases microglial/macrophage M2-like polarization while increases M1-like polarization, which exacerbates the secondary brain damage and sensorimotor deficits after TBI. Recombinant PS exerts beneficial effects in TBI mice through Mer activation.
Mer is an important regulator of microglial/macrophage M1/M2 polarization and neuroinflammation, and may be considered as a potential target for therapeutic intervention in TBI.
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•Inhibition of hydrogenotrophic methanogens in anaerobic fermentation is analyzed.•The free acetic acid (FAA) concentration is the key factor for the inhibition.•Good correlation of ...CoM, relative electron transport activity and FAA is obtained.•The FAA for 50% and 90% of CH4 inhibition are 0.31 and 2.36 g/L, respectively.•Methanogenic activity can be recovered at the low FAA concentration (<0.81 g/L).
The inhibition of acetate under acidic pH is an ideal way to reduce methanogenesis in mesophilic mixed culture fermentation (MCF). However, the effects of acetate concentration and acidic pH on methanogenesis remain unclear. Besides, although hydrogenotrophic methanogens can be suitable targets in MCF, they are generally ignored. Therefore, we intentionally enriched hydrogenotrophic methanogens and found that free acetic acid (FAA, x) concentration and specific methanogenic activity (SMA, y) were correlated according to the equation: y = 0.86 × 0.31/(0.31 + x) (R2 = 0.909). The SMA was decreased by 50% and 90% at the FAA concentrations of 0.31 and 2.36 g/L, respectively. The coenzyme M concentration and relative electron transport activity agreed well with the FAA concentration. Moreover, the methanogenic activity could not be recovered when the FAA concentration exceeded 0.81 g/L. These findings indicated that neither acetate nor acidic pH, but FAA was the key factor to inhibit methanogenesis in MCF.
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•Electro-stimulation of microbial chain elongation for ethanol and CO2 conversion.•Caproate was produced at 2.41 ± 0.69 g L−1 d−1, and reached to 7.66 ± 1.38 g L−1.•Maximum ...SelectivityS was 91.47 ± 0.58% and SelectivityS+E was 80.28 ± 0.52%.•Carbon of 23.43 ± 0.69% in final products was from CO2.•Microbial electrochemical caproate was produced without base addition.
The production of value added chemicals from CO2 is of critical importance for the practical application of microbial electrosynthesis (MES). Here, a binary electron donor (ED) design (using electrode and ethanol) was introduced to provide an efficient caproate production with the bioconversion of both CO2 and ethanol. A maximum caproate production rate of 2.41 ± 0.69 g L−1 d−1, and a final concentration of 7.66 ± 1.38 g L−1 was achieved. Caproate production selectivity based on the substrate increased to 91.47 ± 0.58% (Binary EDs) from 32.22 ± 32.58% (open circuit Electrode ED). An observed amount of 23.43 ± 0.69% of carbon within the final binary ED products originated from the CO2. This work proves for the first time the potential of caproate production from CO2 utilization and ethanol upgrading using solid electrodes to regulate the chain elongation process.
Zika virus (ZIKV), which preferentially targets neural stem and progenitor cells (NSCs) especially in developing brain, is causally associated with fetal microcephaly, intrauterine retardation, and ...other congenital malformations in humans. However, there are, so far, no effective drugs and vaccines against ZIKV epidemics, warranting an enhanced understanding of ZIKV biology. Immune response is essential for neuronal cells to combat viral invasion. In turn, neurotropic ZIKV has developed a complex strategy of neuroimmune evasion to facilitate viral pathogenesis, especially developmental impairment in embryonic brain. Here, we review not only overall knowledge of ZIKV-related immune responses, but also current advances in our understanding of immune evasion in ZIKV infection. We also review several specific mechanisms underlying ZIKV protein-mediated immune evasion for viral pathogenesis.
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•A fresh and acclimated cathode regulates mixed culture chain elongation process.•Tunable products (propionate, butyrate, valerate, and caproate) was generated.•A fresh carbon felt ...cathode increased the caproate specificity by about 28%.•With an acclimated cathode, the caproate specificity was mostly non-linear.
Chain elongation has been proposed as a novel secondary fermentation process for the production of medium chain fatty acids as organic waste valorization. However, a strategy to effectively control the product spectrum of the chain elongation process is required. This study evaluated the effect of electro-fermentation on the mixed culture chain elongation process in detail. The results showed that electro-fermentation with a fresh carbon felt cathode increased the caproate specificity by about 28%, compared with the open circuit control and without carbon felt control. With an acclimated cathode, the effect of electro-fermentation on caproate specificity depended on the substrate concentration. The majority of bacteria belonged to Firmicutes, Bacteroidetes, and Proteobacteria, the distribution of which under biofilm and planktonic conditions were shaped by the application of electro-fermentation. These findings suggested that microorganisms interacted electrochemically with the polarized fresh electrode for chain elongation. The synergistic effect between microorganisms and acclimated electrode was largely affected by elevated substrate concentrations, and thus resulted in a redirection of the fermentation pattern.
High probability of metastasis limited the long-term survival of patients with hepatocellular carcinoma (HCC). Our previous study revealed that Galectin-3 was closely associated with poor prognosis ...in HCC patients.
The effects of Galectin-3 on tumour metastasis were investigated in vitro and in vivo, and the underlying biological and molecular mechanisms involved in this process were evaluated.
Galectin-3 showed a close correlation with vascular invasion and poor survival in a large-scale study in HCC patients from multiple sets. Galectin-3 was significantly involved in diverse metastasis-related processes in HCC cells, such as angiogenesis and epithelial-to-mesenchymal transition (EMT). Mechanistically, Galectin-3 activated the PI3K-Akt-GSK-3β-β-catenin signalling cascade; the β-catenin/TCF4 transcriptional complex directly targeted IGFBP3 and vimentin to regulate angiogenesis and EMT, respectively. In animal models, Galectin-3 enhanced the tumorigenesis and metastasis of HCC cells via β-catenin signalling. Moreover, molecular deletion of Galectin-3-β-catenin signalling synergistically improved the antitumour effect of sorafenib.
The Galectin-3-β-catenin-IGFBP3/vimentin signalling cascade was determined as a central mechanism controlling HCC metastasis, providing possible biomarkers for predicating vascular metastasis and sorafenib resistance, as well as potential therapeutic targets for the treatment of HCC patients.
•Comprehensive analysis of the bidirectional EET of a single electrode-biofilm.•Summary of current study using pure culture capable of bidirectional EET.•Side-by-side discussing of the application ...and challenges of bidirectional EET.
The extracellular electron transfer (EET) between microorganisms and electrodes forms the basis for microbial electrochemical technology (MET), which recently have advanced as a flexible platform for applications in energy and environmental science. This review, for the first time, focuses on the electrode-biofilm capable of bidirectional EET, where the electrochemically active bacteria (EAB) can conduct both the outward EET (from EAB to electrodes) and the inward EET (from electrodes to EAB). Only few microorganisms are tested in pure culture with the capability of bidirectional EET, however, the mixed culture based bidirectional EET offers great prospects for biocathode enrichment, pollutant complete mineralization, biotemplated material development, pH stabilization, and bioelectronic device design. Future efforts are necessary to identify more EAB capable of the bidirectional EET, to balance the current density, to evaluate the effectiveness of polarity reversal for biocathode enrichment, and to boost the future research endeavors of such a novel function.
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•Electric field applications inhibited nitrification in composting.•Electric-field assisted composting promoted nosZ expression.•N2O was mainly from nitrification in electric-field ...assisted aerobic composting.
Nitrous oxide (N2O) emission is a serious environmental problem in composting. Previous studies have indicated that electric field assistance results in lower N2O emissions in aerobic composting; however, the exact mechanisms involved in electric-field assisted aerobic composting (EAAC) are not clear. In this study, the biological N transformation processes and the N-associated genes were investigated. The results demonstrated that electric field application inhibited nitrification, weakened the nitrifying functional genes (the hao and nxrA genes declined maximally by 86% and 86.8%, respectively), and increased the N2O consumption-related gene (nosZ) by a maximum factor of 2.76 compared with that in CAC. The correlation analysis demonstrated that nitrification was the main source of N2O emission in EAAC. The findings imply that EAAC is a promising process for mitigating N2O emission at the source during aerobic composting.
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