Antagonism between neuropeptides and monoamines in a distributed circuit for pathogen avoidance.

Pathogenic infection elicits behaviors that promote recovery and survival of the host. After exposure to the pathogenic bacterium Pseudomonas aeruginosa PA14, the nematode Caenorhabditis elegans modifies its sensory preferences to avoid the pathogen. Here, we identify antagonistic neuromodulators that shape this acquired avoidance behavior. Using an unbiased cell-directed neuropeptide screen, we show that AVK neurons upregulate and release RF/RYamide FLP-1 neuropeptides during infection to drive pathogen avoidance. Manipulations that increase or decrease AVK activity accelerate or delay pathogen avoidance, respectively, implicating AVK in the dynamics of avoidance behavior. FLP-1 neuropeptides drive pathogen avoidance through the G protein-coupled receptor DMSR-7, as well as other receptors. DMSR-7 in turn acts in multiple neurons, including tyraminergic/octopaminergic neurons that receive convergent avoidance signals from the cytokine DAF-7/transforming growth factor ß. Neuromodulators shape pathogen avoidance through multiple mechanisms and targets, in agreement with the distributed neuromodulatory connectome of C. elegans.

Mechanistic insight into the aggregation ability of anammox microorganisms: Roles of polarity, composition and molecular structure of extracellular polymeric substances.

The chemical characteristics of extracellular polymeric substances (EPS) of anammox bacteria (AnAOB) play a crucial role in the rapid enrichment of AnAOB and the stable operation of wastewater anammox processes. To clarify the influential mechanisms of sludge EPS on AnAOB aggregation, multiple parameters, including the polarity distribution, composition, and molecular structure of EPS, were selected, and their quantitative relationship with AnAOB aggregation was analyzed. Compared to typical anaerobic sludge (anaerobic floc and granular sludge), the anammox sludge EPS exhibited higher levels of tryptophan-like substances (44.82-56.52 % vs. 2.57-39.81 %), polysaccharides (40.02-53.49 mg/g VSS vs. 30.22-41.69 mg/g VSS), and protein structural units including α-helices (20.70-23.98 % vs. 16.48-19.32 %), ß-sheets (37.43-42.98 % vs. 25.78-36.72 %), and protonated nitrogen (Npr) (0.065-0.122 vs. 0.017-0.061). In contrast, it had lower contents of ß-turns (20.95-27.39 % vs. 28.17-39.04 %). These biopolymers were found to originate from different genera of AnAOB. Specifically, the α-helix-rich proteins were mainly derived from Candidatus Kuenenia, whereas the extracellular proteins related to tryptophan and Npr were closely associated with Candidatus Brocadia. Critically, these EPS components could drive anammox aggregation through interactions. Substantial amounts of tryptophan-like substances facilitated the formation of ß-sheet structures and the exposure of internal hydrophobic clusters, which benefited the anammox aggregation. Meanwhile, extracellular proteins with high Npr content played a pivotal role in the formation of mixed protein-polysaccharide gel networks with the electronegative regions of polysaccharides, which could be regarded as the key component in the maintenance of anammox sludge stability. These findings provide a comprehensive understanding of the multifaceted roles of EPS in driving anammox aggregation and offer valuable insights into the development of EPS regulation strategies aimed at optimizing the anammox process.

Effect and potential mechanisms of sludge-derived chromium, nickel, and lead on soil nitrification: Implications for sustainable land utilization of digested sludge.

Increasing occurrence of heavy metals (HMs) in sewage sludge threatens its widespread land utilization in China due to its potential impact on nutrient cycling in soil, requiring a better understanding of HM-induced impacts on nitrification. Herein, lab-scale experiments were conducted over 185-day, evaluating the effect of sludge-derived chromium (Cr3+), nickel (Ni2+), and lead (Pb2+) on soil nitrification at different concentrations. Quantitative polymerase chain reaction and linear regression results revealed an inhibitory sequence of gene abundance by HMs' labile fraction: ammonia-oxidizing bacteria (AOB)-ammonia monooxygenase (amoA)> nitrite oxidoreductase subunit alpha (nxrA)> nitrite oxidoreductase subunit beta (nxrB). The toxicity of HMs' incremental labile fraction decreased in the order of Ni2+>Cr3+>Pb2+, with respective threshold values of 5.01, 24.03 and 38.42 mg·kg-1. Furthermore, extending incubation time reduced HMs inhibition on ammonia oxidation, mainly related to their fraction bound to carbonate minerals. Random Forest analysis, variation partitioning analysis, and Mantel test indicated that soil physicochemical properties primarily affected nitrification genes, especially in the test of Cr3+ on AOB-amoA, nxrA, nxrB, Ni2+ for complete ammonia-oxidizing bacteria-amoA, and Pb2+ for nxrA and nxrB. These findings underline the importance of labile HMs fractions and soil physicochemical properties to nitrification, guiding the establishment of HM control standards for sludge utilization.

A review of application of combined biochar and iron-based materials in anaerobic digestion for enhancing biogas productivity: Mechanisms, approaches and performance.

Strengthening direct interspecies electron transfer (DIET), via adding conductive materials, is regarded as an effective way for improving methane productivity of anaerobic digestion (AD). Therein, the supplementation of combined materials (composition of biochar and iron-based materials) has attracted increasing attention in recent years, because of their advantages of promoting organics reduction and accelerating biomass activity. However, as far as we known, there is no study comprehensively summarizing the application of this kind combined materials. Here, the combined methods of biochar and iron-based materials in AD system were introduced, and then the overall performance, potential mechanisms, and microbial contribution were summarized. Furthermore, a comparation of the combinated materials and single material (biochar, zero valent iron, or magnetite) in methane production was also evaluated to highlight the functions of combined materials. Based on these, the challenges and perspectives were proposed to point the development direction of combined materials utilization in AD field, which was hoped to provide a deep insight in engineering application.

Carbonate-bound Pb percentage distribution in agricultural soil and its toxicity: Impact on plant growth, nutrient cycling, soil enzymes, and functional genes.

Metals pollution of lead in agricultural soils is a serious problem for food safety. Therefore, we investigated the toxic effects of carbonate-bound fraction Pb on agricultural soil from various aspects. The results revealed that a higher carbonate-bound fraction of Pb had more toxic effects on wheat growth, as evidenced by higher malondialdehyde (3.17 µmol g-1 FW) and lower catalase levels (9.77 µg-1 FW min-1). In terms of nutrient cycling, soil nutrients including carbon, nitrogen, and phosphorus would slow down transformation rates in high concentrations. Compared to carbon, nitrogen and phosphorus were more likely to be affected by the initial carbonate-bound fraction at the earlier stage. Increased Pb dosage may reduce the soil enzymes activity such as urease (119-50 U g-1) and phosphatase (3191-967 U g-1), as well as the functional genes of nitrogen degradation related nirK, nisS, and carbon related pmoA. Correlation analysis and structural equation modeling indicated that carbonate bound Pb could regulate nutrients cycle via functional genes inhibition, soil enzyme activity reduction and wheat growth suppression in agricultural soil. Our findings will help with polluted agricultural soil monitoring and regulation through microbial activity to ensure food safety.

Enhancement of organics and nutrient removal and microbial mechanism in vertical flow constructed wetland under a static magnetic field.

Low and unstable pollutant removal is regarded as the bottleneck problem in constructed wetlands (CWs) for wastewater treatment. This study investigated the effect of static magnetic field (MF) on enhancing the purification efficiency and microbial mechanism in vertical flow CW systems for treating domestic wastewater. The results showed that MF-CWs outperformed control systems in terms of treatment performance, with average removal efficiencies of COD, NH4+-N, TN, and TP reaching 92.58%, 73.58%, 72.53%, and 95.83%, respectively. The change of malondialdehyde (MDA), catalase (CAT), and superoxide dismutase (SOD) activity indicated that MF application was beneficial for plant health. Additionally, higher ammonia monooxygenase (AMO) activity in MF-CWs suggested the removal of NH4+-N was facilitated. The high-throughput sequencing results demonstrated that MF application could enrich the functional bacteria such as Patescibacteria phylum, mainly, including Gammaproteobacteria, Betaproteobacteria, and Alphaproteobacteria, which further accelerated pollutants transformation. These findings would be beneficial in understanding pollutant removal processes and their mechanism in CWs with MF application.

Extracellular polymeric substances-antibiotics interaction in activated sludge: A review.

Antibiotics, the most frequently prescribed drugs, have been widely applied to prevent or cure human and veterinary diseases and have undoubtedly led to massive releases into sewer networks and wastewater treatment systems, a hotspot where the occurrence and transformation of antibiotic resistance take place. Extracellular polymeric substances (EPS), biopolymers secreted via microbial activity, play an important role in cell adhesion, nutrient retention, and toxicity resistance. However, the potential roles of sludge EPS related to the resistance and removal of antibiotics are still unclear. This work summarizes the composition and physicochemical characteristics of state-of-the-art microbial EPS, highlights the critical role of EPS in antibiotics removal, evaluates their defense performances under different antibiotics exposures, and analyzes the typical factors that could affect the sorption and biotransformation behavior of antibiotics. Next, interactions between microbial EPS and antibiotic resistance genes are analyzed. Future perspectives, especially the engineering application of microbial EPS for antibiotics toxicity detection and defense, are also emphatically stressed.

Mechanisms, performance, and the impact on microbial structure of direct interspecies electron transfer for enhancing anaerobic digestion-A review.

Direct interspecies electron transfer (DIET) has been received tremendous attention, recently, due to the advantages of accelerating methane production via organics reduction during anaerobic digestion (AD) process. DIET-based syntrophic relationships not only occurred with the existence of pili and some proteins in the microorganism, but also can be conducted by conductive materials. Therefore, more researches into understanding and strengthening DIET-based syntrophy have been conducted with the aim of improving methanogenesis kinetics and further enhance methane productivity in AD systems. This study summarized the mechanisms, application and microbial structures of typical conductive materials (carbon-based materials and iron-based materials) during AD reactors operation. Meanwhile, detail analysis of studies on DIET (from substrates, dosage and effectiveness) via conductive materials was also presented in the study. Moreover, the challenges of applying conductive materials in boosting methane production were also proposed, which was supposed to provide a deep insight in DIET for full scale application.

Calcium peroxide and freezing co-pretreatment enhancing short-chain fatty acids production from waste activated sludge towards carbon-neutral sludge treatment.

Short-chain fatty acids (SCFAs) recovery through anaerobic fermentation is a promising technology to achieve carbon-neutral in waste activated sludge (WAS) management. After 0.15 g CaO2/g volatile suspended solids (VSS) addition and three-cycle freezing co-pretreatments, the maximal SCFAs production of 438.5 mg COD/g VSS was achieved within 4 days fermentation, and more than 70 % of SCFAs was composed of acetate and propionate, which achieved a higher level than reported in previous studies. Mechanism explorations elucidated that co-pretreatment triggered sludge solubilization, promoting the release of biodegradable organics, providing more biodegradable substrates for SCFAs generation. Further microbial community analysis indicated that the abundances of hydrolytic microorganisms and acidogens were enriched, whereas methanogens were inhibited. Besides, environmental analysis suggested that co-pretreatment could achieve carbon reduction benefits of 0.116-0.291 ton CO2/ton WAS, demonstrating its huge carbon-neutral potential benefits.

Efficiency assessment of ZVI-based media as fillers in permeable reactive barrier for multiple heavy metal-contaminated groundwater remediation.

Four zero valent iron-based composites were prepared and applied as the reactive media of permeable reactive barriers. Batch tests and continuous-flow column experiments were conducted to assess the long-term performance of these composites for possible utilization as fillers for PRB. The experimental results of the batch tests revealed that in single-metal systems, the removal efficiency of Cu(Ⅱ), Co(Ⅱ), Cr(Ⅵ) and As(Ⅲ) could reach 98% at equilibrium. Equilibrium data showed that composites displayed different selectivity values in binary and quaternary-component systems. For the continuous tests, column filled with chitosan-zero valent iron-based composites, exhibited optimal removal efficiency and achieved average removal values of 98.84%, 88.28%, 95.65% and 87.10% for Cu(Ⅱ), Co(Ⅱ), Cr(Ⅵ) and As(Ⅲ) during the whole 30-day operation, respectively. Dynamic removal improvement of multiple metals was observed with further assembly media, with average removal of 99.11%, 90.05% and 87.34% for Cu(Ⅱ), Co(Ⅱ) and As(Ⅲ), respectively. Combined with superficial characteristic analysis, the functional groups distributed on the surface of composites played a key role in metal sorption. Moreover, the adsorbed Cu(Ⅱ), Co(Ⅱ) and Cr(Ⅵ) gradually transferred to the mobile phase when the operational periods were prolonged, while As(Ⅲ) became more stable.

Tracing dissolved organic matter in inflowing rivers of Nansi Lake as a storage reservoir: Implications for water-quality control.

Quantitative characterization of dissolved organic matter (DOM) in various aquatic ecosystems has become of increasing importance as its transformation plays a key role in inland water carbon, yet few studies have quantified water DOM inputs to storage lakes for water quality control and safety assurance. This study assessed the quantity and quality of DOM in 21 inflow rivers of Nansi Lake as the important storage lake of large-scale water transfer projects by using excitation-emission matrix spectroscopy coupled with parallel factor analysis (EEM-PARAFAC) and ultraviolet-visible (UV-Vis) spectroscopy. The results showed that DOM contents varied significantly with an average value of 5.8 mg L-1 in different inflow rivers, and three fluorescence substances (including UVC humic-like, UVA humic-like and tyrosine-like components) were identified by EEM-PARAFAC. The distribution of the DOM components was distinctively different among sampling sites, and UVA humic-like component mainly dominated in Nansi Lake. Meanwhile, DOM components with higher aromaticity and molecular weight were found in the west side of lake. Fluorescence spectral indexes manifested that the source of DOM was mainly from allochthonous or terrestrial input. Moreover, significant correlations between water quality and DOM characteristics were observed in Nansi Lake. These findings would be beneficial to understand the biogeochemical role and impact of DOM in inflowing rivers in the water-quality monitoring and control of storage lakes.

Mapping the biosynthetic pathway of a hybrid polyketide-nonribosomal peptide in a metazoan.

Polyketide synthase (PKS) and nonribosomal peptide synthetase (NRPS) hybrid systems typically use complex protein-protein interactions to facilitate direct transfer of intermediates between these multimodular megaenzymes. In the canal-associated neurons (CANs) of Caenorhabditis elegans, PKS-1 and NRPS-1 produce the nemamides, the only known hybrid polyketide-nonribosomal peptides biosynthesized by animals, through a poorly understood mechanism. Here, we use genome editing and mass spectrometry to map the roles of individual PKS-1 and NRPS-1 enzymatic domains in nemamide biosynthesis. Furthermore, we show that nemamide biosynthesis requires at least five additional enzymes expressed in the CANs that are encoded by genes distributed across the worm genome. We identify the roles of these enzymes and discover a mechanism for trafficking intermediates between a PKS and an NRPS. Specifically, the enzyme PKAL-1 activates an advanced polyketide intermediate as an adenylate and directly loads it onto a carrier protein in NRPS-1. This trafficking mechanism provides a means by which a PKS-NRPS system can expand its biosynthetic potential and is likely important for the regulation of nemamide biosynthesis.

Impacts of aeration and biochar on physiological characteristics of plants and microbial communities and metabolites in constructed wetland microcosms for treating swine wastewater.

Constructed wetlands (CWs) by modifying operation strategies or substrates have grown in popularity in recent years for improving the treatment capacity. However, few studies focused on the responses of wetland vegetation and associated microorganisms in CWs for treating high-strength wastewaters. This study evaluated the long-term responses of plants and microbes in CWs with biochar and intermittent aeration for treating real swine wastewater. The results showed that intermittent aeration or combined with biochar could decrease the stress response of wetland plants against the swine wastewater. Biochar addition promoted the production of extracellular polymeric substances (EPS, total 516.27 mg L-1) mainly including protein-like, humic-like and tryptophan-like components. However, intermittent aeration resulted in the EPS reduction (99.24 mg L-1). As for microbial communities, biochar addition supported rich and diverse microbial communities (652 OTUs), while the combination with biochar and aeration could not improve diversity of microbes (597 OTUs). Additionally, the combination altered the microbial community structures and changed microbial composition correlated with environmental factors.

Dynamic variation in nitrogen removal of constructed wetlands modified by biochar for treating secondary livestock effluent under varying oxygen supplying conditions.

Vertical flow constructed wetlands are facing the problem of low removal efficiency when treating high-load wastewater. This study explored the effect of oxygen supplement (1.2, 1.0, 0.8 L min-1 for 6 h; 1.0 L min-1 for 4 h and 2 h) on enhancing nitrogen removal in vertical flow constructed wetlands modified by adding biochar for treating secondary livestock effluent. The results indicated that biochar addition could enhance contaminant removal due to its adsorption of contaminants under the condition of no aeration. Additionally, the aeration addition of 1.0 L min-1 for 2 h per day in biochar-based constructed wetlands achieved the high efficiencies for chemical oxygen demand (95%) and total nitrogen (73%) removal. However, total nitrogen removal efficiency in biochar-based constructed wetlands declined under excessive dissolved oxygen conditions which might restrain the denitrification process. Average nitrous oxide emission fluxes in biochar-based constructed wetlands (575-1877 µg m-2 h-1) were lower than those in non-biochar constructed wetlands (745-2298 µg m-2 h-1). In addition, the variation of N2O emission under different aeration conditions was similar with the maximum value at the aeration condition of 1.2 L min-1 for 6 h d-1. These results could be useful for improving the sustainable design and operation of constructed wetlands for high-load wastewater treatments.

An innovative biochar-amended substrate vertical flow constructed wetland for low C/N wastewater treatment: Impact of influent strengths.

Application of biochar can be an effective and low cost technique for wastewater treatment while reducing greenhouse gas emissions. In this study, biochar was used as substrates in Vertical flow constructed wetlands (VFCWs) for enhancing the removal of contaminant from low C/N wastewaters with different influent strengths. The removal of organic matter and nitrogen in biochar-added and non-biochar-added VFCWs with different low C/N influent strengths were evaluated systematically. The results demonstrated that combining VFCWs and biochar addition could be an appropriate strategy as compared to conventional VFCWs with average removal of organic pollutants (85%), NH4+-N (39%) and TN (39%) especially at high influent strengths. Meanwhile, N2O emission was also significantly lower in biochar-added VFCWs (138-1008µgm-2h-1) than that in non-biochar-added VFCWs (164-1304µgm-2h-1) under different influent strengths. We believe that VFCWs by adding biochar can be a useful technology for treating low C/N wastewaters.

Biosynthetic tailoring of existing ascaroside pheromones alters their biological function in C. elegans.

Caenorhabditis elegans produces ascaroside pheromones to control its development and behavior. Even minor structural differences in the ascarosides have dramatic consequences for their biological activities. Here, we identify a mechanism that enables C. elegans to dynamically tailor the fatty-acid side chains of the indole-3-carbonyl (IC)-modified ascarosides it has produced. In response to starvation, C. elegans uses the peroxisomal acyl-CoA synthetase ACS-7 to activate the side chains of medium-chain IC-ascarosides for ß-oxidation involving the acyl-CoA oxidases ACOX-1.1 and ACOX-3. This pathway rapidly converts a favorable ascaroside pheromone that induces aggregation to an unfavorable one that induces the stress-resistant dauer larval stage. Thus, the pathway allows the worm to respond to changing environmental conditions and alter its chemical message without having to synthesize new ascarosides de novo. We establish a new model for biosynthesis of the IC-ascarosides in which side-chain ß-oxidation is critical for controlling the type of IC-ascarosides produced.

[Immature dendritic cells phagocytosing human spleen cells treated by PUVA present the characteristics of regulatory dendritic cells].

Objective To investigate the effect of psoralen combined with A-band ultraviolet (PUVA)-treated human spleen lymphocytes on the phenotype and function of immature dendritic cells (imDCs). Methods Human peripheral blood mononuclear cells (PBMCs) were isolated and induced to produce DCs by interleukin-4 (IL-4) and recombinant human granulocyte macrophage colony stimulating factor (rhGM-CSF). On the sixth day, the imDCs were obtained and stimulated by lipopolysaccharide (LPS). One day later, mature DCs were harvested. Human spleen cells (SPs) were isolated and treated with PUVA to prepare apoptotic PUVA-SPs. Co-culture of imDCs with PUVA-SPs resulted in extracorporeal photochemotheraputic DCs (ecpDCs). Co-culture of imDCs with SPs resulted in SP-DCs. The expressions of CD11c, CD83 and CD86 were detected by flow cytometry. The levels of IL-10 and IL-12 in the supernatants of the above cells were determined by ELISA. Results The early apoptosis rate of PUVA-SPs was (94.21±3.75)%. There was no significant difference in the expressions of CD83 and CD86 between imDCs and ecpDCs. But the positive rates of CD83 and CD86 in ecpDCs were lower than those in DCs. However, the positive rates of CD83 and CD86 in SP-DCs were significantly higher than those of the imDCs. Conclusion The imDCs phagocytosing apoptotic human SPs present phenotype and function of regulatory DCs.

[Immature dendritic cells phagocytosing apoptotic human spleen cells treated with PUVA inhibits the maturation induced by LPS].

Objective To investigate whether lipopolysaccharide (LPS) can induce the maturation of immature dendritic cells (imDCs) which phagocytose apoptotic spleen lymphocytes. Methods Human peripheral blood mononuclear cells (PBMCs) were induced to produce DCs by interleukin 4 (IL-4) and recombinant human granulocyte macrophage colony stimulating factor (rhGM-CSF). Human spleen cells (hSPs) were isolated and treated with psoralen combined with ultraviolet A(PUVA) to obtain apoptotic PUVA-hSPs. Co-culture of imDCs with PUVA-hSPs resulted in extracorporeal photochemotherapeutic dendritic cells (ecpDCs). The imDCs and ecpDCs were collected and stimulated by 10 ng/mL LPS for 1 day. The expressions of CD11c, CD83 and CD86 were detected by flow cytometry. The level of IL-10 in the supernatants of the above cells was detected by ELISA. Results There was no significant difference in the expressions of CD83 and CD86 between ImDCs and ecpDCs. However, the positive rates of CD83 and CD86 in the imDCs stimulated by LPS were significantly higher than those in the ecpDCs treated by LPS. The level of IL-10 in imDCs culture supernatant was lower than that in ecpDCs. The level of IL-10 in LPS-stimulated imDCs was lower than that in LPS-stimulated ecpDCs. Conclusion Both imDCs and ecpDCs showed immature phenotype, but ecpDCs can inhibit the maturation of DC induced by LPS.

Sirolimus treatment for cirrhosis or hepatocellular carcinoma patients accompanied by psoriasis after liver transplantation: A single center experience.

There is currently no consensus on the most suitable therapeutic approach for psoriasis (PS) co-existing with posthepatic cirrhosis (PCs) and hepatocellular carcinoma (HCC) following liver transplantation (LT). The present study provides an analysis of the therapeutic experience of such patients. Five LT recipients (two with PC and three with HCC) with accompanying PS were included. The induction program consisted of methylprednisolone plus basiliximab treatment. The initial postoperative treatment scheme consisted of tacrolimus (FK506) plus mycophenolate mofetil (MMF) and hormone; the latter was withdrawn 1 week after LT. The patients with PC had been using FK506 with or without a postoperative MMF program; the patients with HCC and recurrence of PS had been switched to a sirolimus (SRL)-based replacement therapy. Furthermore, all patients received anti-hepatitis B virus (HBV) therapy. The patients were followed up after 8.3±1.5 years. There was a positive correlation between HBV-DNA copy numbers, and psoriatic area and severity index (PASI) scores (r=0.97; P=0.006). The PASI scores were decreased significantly at 6 months following surgery compared with pre-transplantation (P<0.05). The patients who had received the FK506-based treatment experienced PS recurrence two years post-transplantation. The PASI scores increased significantly (P<0.05) and then declined gradually, maintaining a stable level (P<0.05) by 1 year after switching to the SRL-based treatment. The patients who had received the SRL-based treatment exhibited no recurrence of PS. The results of the present study suggest that SRL therapy provides a promising novel treatment method for patients with PS following LT that may be superior to tacrolimus treatment. When co-existing HBV is present pre-transplantation, regular injection of human hepatitis B immunoglobulin should be used to prevent the HBV from relapsing or aggravating the PS.

A hybrid polyketide-nonribosomal peptide in nematodes that promotes larval survival.

Polyketides and nonribosomal peptides are two important types of natural products that are produced by many species of bacteria and fungi but are exceedingly rare in metazoans. Here, we elucidate the structure of a hybrid polyketide-nonribosomal peptide from Caenorhabditis elegans that is produced in the canal-associated neurons (CANs) and promotes survival during starvation-induced larval arrest. Our results uncover a novel mechanism by which animals respond to nutrient fluctuations to extend survival.