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1.
Macromol Biosci ; : e2100417, 2022 Jan 04.
Artigo em Inglês | MEDLINE | ID: mdl-34981893

RESUMO

This work reports a hypoxia-activated fluorescent probe for tumor imaging by using self-immolative block copolymer with azobenzene linkage. The water-soluble polymer composed of self-immolative building blocks shows no obvious fluorescence. Under the hypoxic microenvironment of tumor cells, the azobenzene is reduced by the overexpressed azoreductase, which will trigger a domino-like disassembly of the self-immolative polymer. The released building blocks from the self-immolative polymer emit strong fluorescence, which shows the potential application in tumor imaging.

2.
J Environ Manage ; 305: 114380, 2022 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-34995945

RESUMO

The co-occurrence networks and interactions of bacterial communities in sediments are highly variable with environmental factors, which are vital to the nutrient biogeochemical cycle, pollutants biodegradation, and microbial community stability in lake ecosystems. Although pollution gradients reflect environmental variation comprehensively, few studies have characterized the changes in co-occurrence networks and interactions of bacterial communities along sediment pollution gradients. In order to investigate the impact of pollution gradients on compositions, co-occurrence networks, and interactions of sedimentary microbial communities, we studied the bacterial communities in the sediments of a typical shallow eutrophic lake, Taihu Lake, along pollution gradients using 16S rRNA gene high-throughput sequencing technology. All the sediment sampling sites were classified into mild, moderate, and severe pollution groups according to the sediments' physicochemical properties. Our results showed that the taxon richness was lowest in the severe pollution group, and the diversity of species decreased with the level of pollution. The complexity of the co-occurrence network decreased as the level of pollution increased, and the severe pollution group was characterized by a small-world network. The relative abundance of Proteobacteria, Bacteroidetes, and Chlorobi increased significantly as the level of pollution increased (P < 0.05). Strong inter-phyla co-occurrence or co-exclusion patterns demonstrated that the strength of interactions was enhanced in the severe pollution group, indicating stronger cooperative or competitive relationships. Chloroflexales and Chlorobiales were unique keystone taxa in the severe pollution group. The results of this study indicate that severe pollution reduces microbial diversity and network complexity, which may lead to community instability. The competition for nutrients of some copiotrophic bacteria may be enhanced as the level of pollution increased. The unique keystone taxa may contribute to photosynthesis and pollutant degradation in the severe pollution group. These findings expand our understanding of variation in bacterial co-occurrence networks and interactions along sediment pollution gradients.

3.
J Environ Manage ; 304: 114267, 2022 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-34896801

RESUMO

Prioritizing the relationship between heterogeneity of sediment habitats and river bends is critical when planning and reconstructing urban rivers. However, the exact relationship between ecological heterogeneity and river bends remains ambiguous. Therefore, this research proposed a new approach to quantify and predict bend-induced ecological heterogeneity, incorporating the bacteria-based index of biotic integrity (Ba-IBI), path model, and random forest regression model. The developed Ba-IBI quantified heterogeneity in sediment microbial communities, ranging from low (1.40) to high (3.97). A path model was developed and validated in order to further investigate the relative contributions of environmental factors to the Ba-IBI. The established path model, which was considered acceptable with a CMIN/df = 1.949 < 4, suggested that primary environmental factors affecting the sediment bacterial communities were flow velocity and ammonium concentration in sediment. To further characterize the relationship between environmental factors and the Ba-IBI, a function was constructed using the random forest regression model that predicts the responses of sediment bacterial communities to environmental factors with R2 = 0.6126. The proposed approach and prediction tools will provide knowledge to improve natural channel design and post-project evaluations in river restoration projects.


Assuntos
Monitoramento Ambiental , Microbiota , Algoritmos , Bactérias , Ecossistema , Rios , Aprendizado de Máquina Supervisionado
4.
J Mol Endocrinol ; 68(2): 111-123, 2022 Jan 20.
Artigo em Inglês | MEDLINE | ID: mdl-34910685

RESUMO

Effects of melatonin on the release and synthesis of gonadotropin-releasing hormone (GnRH) and luteinizing hormone (LH) at the hypothalamus and pituitary levels have been explored in some species, but a similar study in the corpora lutea (CL) has not yet been conducted. In this study, the immunostaining for GnRH and LH was observed in luteal cells of porcine CL during pregnancy, and a significant effect of pregnant stage on the level of GnRH and LH was found; higher values for GnRH and LH immunostaining and mRNA were detected in the early and mid-stages CL than in the later-stage CL (P < 0.01). Furthermore, the patterns of melatonin membrane receptors (MT1 and MT2) expression were consistent with those of GnRH and LH expression in the CL of pregnant sows; the relative levels of MT1 and MT2 in the early and mid-stages were significantly higher than those in the later-stage (P < 0.01). In luteal cells, melatonin dose-dependently increased in GnRH and LH secretion and mRNA expression. Melatonin also increased the GnRH-induced accumulation of LH and the LH-induced secretion of P4 in luteal cells. Additionally, the effects of melatonin on luteal GnRH and LH production were blocked by luzindole, a non-selective MT1 and MT2 receptor antagonist. Our results demonstrate the stimulatory effects of melatonin on GnRH and LH production in luteal cells of pregnant sows, suggesting a potential role for melatonin in luteal function through regulating the release and synthesis of GnRH and LH in luteal cells.

5.
Sci Total Environ ; 806(Pt 3): 150542, 2022 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-34582874

RESUMO

Pelagic fish embryos are thought to float in or near surface waters for the majority of their development and are presumed to have little to no control over their mobility, rendering these embryos at high risk for damages associated with surface stressors such as ultraviolet radiation (UVR). We recently challenged these long-standing paradigms by characterizing a potential mechanism of stressor avoidance in early-life stage mahi-mahi (Coryphaena hippurus) in which embryos sense external cues, such as UVR, and modify their buoyancy to reduce further exposure. It is unknown whether embryos of other marine fish with pelagic spawning strategies have similar capabilities. To fill this knowledge gap, we investigated buoyancy change in response to UVR in three additional species of marine fish that utilize a pelagic spawning strategy: yellowfin tuna (Thunnus albacares), red snapper (Lutjanus campechanus), and cobia (Rachycentron canadum). Embryos of all three species displayed increased specific gravity and loss of buoyancy after exposures to environmentally relevant doses of UVR, a response that may be ubiquitous to fish with pelagic embryos. To gain further insight into this response, we investigated recovery of buoyancy, oxygen consumption, energy depletion, and photolyase induction in response to UVR exposures in at least one of the three species listed above.


Assuntos
Perciformes , Poluição por Petróleo , Petróleo , Hidrocarbonetos Policíclicos Aromáticos , Poluentes Químicos da Água , Animais , Embrião não Mamífero/química , Hidrocarbonetos Policíclicos Aromáticos/análise , Raios Ultravioleta
6.
Sci Total Environ ; 806(Pt 3): 151210, 2022 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-34715211

RESUMO

Increasing attention has been focused on the diminishing health of coastal ecosystems. Understanding the effects of eutrophication on tidal flat ecosystems is beneficial for the restoration and management of coastal ecosystems. However, previous studies did not consider the effects of nitrogen on the structure and function of bacterial and archaeal communities in longitudinal and vertical profiles. Here, the diversity, composition, assembly mechanism, and potential metabolic function of the bacterial and archaeal communities were studied in two longitudinal tidal sections at different eutrophic levels. Nitrogen and salinity were the critical factors that influenced the bacterial and archaeal community composition using canonical correspondence and multivariate regression tree analyses. For the bacterial community, the higher nitrogen loading in tidal mudflats resulted in the convergence of diversity and structure in the longitudinal profile of bacteria, but divergence was detected in the vertical profile. For archaea, the diversity tended to be convergent in longitudinal and vertical profiles in the higher nitrogen area, but the change of structure was similar to that of bacteria. Besides the homogeneous processes influenced by salinity, the assembly process of the bacterial community was mainly influenced by heterogeneous selection (34.8%) and that of archaea by dispersal limitation (19.5%). However, the bacterial and archaeal communities in the higher nitrogen section presented more of an influence of heterogeneous selection (respectively, 39 and 5.6%) than that of the lower nitrogen section (respectively, 10 and 0.2%). Structural equation modeling indicated that nitrogen may have inhibited the effects of the bacterial community on nitrogen turnover in nitrogen-rich anoxic sediment environments, but may have strengthened the effect of the archaeal community on carbon metabolism compared to bacteria. This work deepens our understanding of the responses of bacterial and archaeal community structure and potential function to nitrogen pollution in tidal mudflats.


Assuntos
Archaea , Nitrogênio , Archaea/genética , Bactérias/genética , Ecossistema , Sedimentos Geológicos , Filogenia , RNA Ribossômico 16S
7.
Environ Res ; 204(Pt D): 112371, 2022 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-34774512

RESUMO

The importance of suspended particulate matter (SPM) in nitrogen removal from aquatic environments has been acknowledged in recent years by recognizing the role of attached microbes. However, the succession of attached microbes on suspended particles and their role in nitrogen removal under specific surface microenvironment are still unknown. In this study, the causation among characteristics of SPM, composition and diversity of particle-attached microbial communities, and abundances of nitrogen-related genes in urban rivers was firstly quantitatively established by combing spectroscopy, 16 S rRNA amplicon sequencing, absolute gene quantification and supervised integrated machine learning. SPM in urban rivers, coated with organic layers, was mainly composed of silt and clay (87.59-96.87%) with D50 (medium particle size) of 8.636-30.130 µm. In terms of material composition of SPM, primary mineral was quartz and the four most abundant elements were O, Si, C, Al. The principal functional groups on SPM were hydroxyl and amide. Furthermore, samples with low, medium and high levels of ammoxidation potential were classified into three groups, among which significant differences of microbial communities were found. Samples were also separated into three groups with low, medium and high levels of denitrification potential and significant differences occurred among groups. The particle size, content of functional groups and concentration of SPM were identified as the most significant factors related with microbial communities, playing an important role in succession of particle-attached microbes. In addition, the path model revealed the significantly positive effect of organic matter and particle size on the microbial communities and potential nitrogen removal. The content of hydroxyl and temperature were identified as the most effective predicting factors for ammoxidation potential and denitrification potential respectively by Random Forests Regression models, which had good predictive performances for potential of ammoxidation (R2 = 0.71) and denitrification (R2 = 0.61). These results provide a basis for quickly assessing the ability of nitrogen removal in urban rivers.

8.
Chemosphere ; 287(Pt 2): 132196, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34517239

RESUMO

The intimate coupling of photocatalysis and biodegradation (ICPB) possesses an enhanced ability of recalcitrant contaminant removal and energy generation, owing to the compact communication between biotic components and photocatalysts during the system operation. The photocatalysts in the ICPB system could dispose of noxious contaminants to relieve the external pressure on microorganisms which could realize the mineralization of the photocatalytic degradation products. However, due to the complex components in the composite system, the mechanism of the ICPB system has not been completely understood. Moreover, the variable environmental conditions would play a significant role in the ICPB system performance. The further development of the ICPB scheme requires clarification on how to reach an accurate understanding of the system condition during the practical application. This review starts by offering detailed information on the system construction and recent progress in the system components' amelioration. We then describe the potential influences of relevant environmental factors on the system performance, and the analytical strategies applicable for comprehending the critical processes during the system operation are further summarized. Finally, we put forward the research gaps in the current system and envision the system's prospective application. This review provides a valuable reference for future researches that are devoted to assessing the environmental disturbance and exploring the reaction mechanisms during the practical application of the ICPB system.


Assuntos
Titânio , Biodegradação Ambiental
9.
J Cancer Res Ther ; 17(5): 1269-1274, 2021 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-34850777

RESUMO

Objectives: The objective of the study was to assess the clinical efficacy of computed tomography (CT)-guided cryoablation as a means to treat adrenal metastasis (AM) secondary to lung cancer. Materials and Methods: This study was a single-center retrospective study that analyzed 39 consecutive patients with AM secondary to lung cancer who underwent CT-guided cryoablation in our center. The rates of complete ablation, local recurrence, local recurrence-free survival (RFS), and overall survival (OS) were analyzed. Results: The rates of primary and secondary complete ablation were 94.9% and 100%, respectively, and none of the patients suffered from a hypertensive crisis associated with the treatment. Over the follow-up period, 20.5% of the patients experienced local recurrence, and the median RFS duration was 26 months. The cumulative 1-, 3-, and 5-year local RFS rates in this study were 84.6%, 51.3%, and 5.9%, respectively. Extra-adrenal gland metastases were detected in five patients. Over the course of follow-up, 26 patients died. The mean OS duration was 34 months with cumulative 1-, 3-, and 5-year OS rates of 89.7%, 53.4%, and 8.3%, respectively. Advanced age (P = 0.001), primary adenocarcinoma (P = 0.006), other primary lung cancers (P = 0.038), and primary Stage III lung cancers (P = 0.007) were all found to be independent predictive factors of poor OS in these patients. Conclusion: CT-guided cryoablation can be safely and effectively used to control AM secondary to lung cancer, and patients with AM secondary to lung squamous cell carcinoma may be best suited for this form of treatment.

10.
Food Funct ; 2021 Dec 03.
Artigo em Inglês | MEDLINE | ID: mdl-34860235

RESUMO

Obesity is a disease in humans and companion animals that can cause many chronic diseases. Eurotium cristatum (E. cristatum) is a dominant fungus in Fuzhuan tea. In this study, we aimed to investigate the possibility that E. cristatum may reduce diet-induced obesity by regulating the gut microbiota and measuring the differences in the gut microbiota of obese mice and dogs under E. cristatum supplementation. High-fat diet-fed C57BL/6J mice and beagle dogs were supplemented with live E. cristatum for 8 or 12 weeks. Faecal microbiota transplantation (FMT) and 16S rRNA sequencing were used to evaluate the relationship between the anti-obesity effect of E. cristatum and the gut microbiota. The results suggested that live E. cristatum reduced obesity and metabolic disorders in obese mice and dogs. 16S rRNA sequencing results revealed that E. cristatum decreased the Firmicutes/Bacteroidetes (F/B) ratio and the abundance of members of the Firmicutes phylum, including Lactobacillus gasseri, Lactobacillus reuteri, and Lactobacillus intestinalis, in obese mice, but the opposite was true in obese dogs. Furthermore, to investigate whether the antiobesity effect of E. cristatum can be attributed to gut microbiota, FMT and 16S rRNA sequencing were employed. The FMT trial confirmed that the anti-obesity effect of E. cristatum was mediated by modulating gut dysbiosis. In addition, we isolated live E. cristatum from faeces and found the ß-hydroxy acid metabolite of monacolin K (MKA) in E. cristatum culture. Our research implies that E. cristatum has the potential to treat obesity as a novel probiotic.

11.
Infect Immun ; : IAI0058421, 2021 Dec 13.
Artigo em Inglês | MEDLINE | ID: mdl-34898251

RESUMO

Leptospirosis is a globally spread zoonotic disease with outcomes ranging from subclinical infection to fatal Weil syndrome. In addition to antibiotics, some immune activators have shown protective effects against leptospirosis. However, the unclear relationship between Leptospira and cytokines, has limited the development of antileptospiral immunomodulators. In this study, the particular role of IL-10 in leptospirosis was explored by using IL-10 defective (IL-10-/-) hamsters. After Leptospira infection, an improved survival rate, reduced leptospiral burden and alleviation of organ lesions were found in IL-10-/- hamsters compared with WT hamsters. In addition, the gene expression levels of IL-1ß, IL-6 and TNF-α and the NO level were higher in IL-10-/- hamsters than in WT hamsters. Our results indicate that IL-10 deficiency protects hamsters from Leptospira infection.

12.
Front Cell Neurosci ; 15: 780447, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34924959

RESUMO

Although epilepsy is one of the most common neurologic disorders, there is still a lack of effective therapeutic drugs for it. Recently, we synthesized a novel hydrogen sulfide (H2S) donor, which is found to reduce seizures in animal models effectively. But it remains to be determined for its mechanism. In the present study, we found that the novel H2S donor could reduce pilocarpine-induced seizures in mice. It alleviated the epileptic behavior, the hippocampal electroencephalography (EEG) activity of seizures, and the damage of hippocampal neurons in status epilepticus mice. In addition, the novel H2S donor could reduce microglial inflammatory response. It not only reduced the upregulation of pro-inflammatory markers [inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX2)] in status epilepticus mice, but also increased the levels of microglial anti-inflammatory marker arginase-1 (Arg-1). In lipopolysaccharide-treated microglia BV2 cells, administration of the H2S donor also significantly reduced the lipopolysaccharide-induced upregulation of the expression of the pro-inflammatory markers and increased the expression of the anti-inflammatory markers. Thus, the novel H2S donor regulates microglial inflammatory profile in status epilepticus mice and in vitro. These results suggested that the novel H2S donor can reduce seizures and regulate microglial inflammatory profile, which may be a novel mechanism and potential therapeutic strategy of the H2S donor anti-seizures.

13.
Environ Sci Technol ; 2021 Dec 30.
Artigo em Inglês | MEDLINE | ID: mdl-34968041

RESUMO

Polymeric membrane design is a multidimensional process involving selection of membrane materials and optimization of fabrication conditions from an infinite candidate space. It is impossible to explore the entire space by trial-and-error experimentation. Here, we present a membrane design strategy utilizing machine learning-based Bayesian optimization to precisely identify the optimal combinations of unexplored monomers and their fabrication conditions from an infinite space. We developed ML models to accurately predict water permeability and salt rejection from membrane monomer types (represented by the Morgan fingerprint) and fabrication conditions. We applied Bayesian optimization on the built ML model to inversely identify sets of monomer/fabrication condition combinations with the potential to break the upper bound for water/salt selectivity and permeability. We fabricated eight membranes under the identified combinations and found that they exceeded the present upper bound. Our findings demonstrate that ML-based Bayesian optimization represents a paradigm shift for next-generation separation membrane design.

14.
Microb Pathog ; 161(Pt A): 105274, 2021 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-34774700

RESUMO

Leptospirosis, caused by pathogenic Leptospira, is a global critical zoonotic disease in terms of mortality and morbidity. Vaccines are often used to prevent leptospirosis. However, few studies have reported the therapeutic effect of a vaccine against Leptospira infection. This study demonstrates the efficacy of the emergency vaccine immunization against acute leptospirosis in hamsters. Treatment with a whole-cell vaccine (Leptospira interrogans serovar Lai) at 24 h post-infection improved the survival rate of hamsters with lower leptospiral burden and minor pathological damage to organs. The vaccine also protected against multiple Leptospira serotypes acute infection. However, the protective effect of the vaccines was lost when beginning treatment at 36 h or 48 h post-infection. These results indicated that vaccines could treat acute leptospirosis in hamsters, but only if immunization is within 24 h after infection.

15.
Microb Pathog ; 162: 105315, 2021 Nov 24.
Artigo em Inglês | MEDLINE | ID: mdl-34826552

RESUMO

Leptospirosis is a worldwide re-emerging zoonosis caused by pathogenic Leptospira. Inflammatory storms induced by Leptospira are the reason to induce immunoparalysis and organ failures. Antibiotics are still the current mainstream treatment for leptospirosis. In addition to their antibacterial action, the immunomodulatory function of antibiotics has been paid more and more attention. In this study, the role of norfloxacin on Leptospira-induced inflammation was investigated. Treatment with norfloxacin down-regulated Leptospira-induced IL-1ß and TNF-α both in vivo and vitro models. Further study showed that norfloxacin inhibited Leptospira-induced phosphorylation of p65 and ERK. Norfloxacin also inhibited the Leptospira-induced NLRP3 inflammasome activation with the increased level of Na/K-ATPase Pump ß1 subunit and decreased level of Kcnk6. These results indicated that norfloxacin suppressed Leptospira-induced inflammation through inhibiting p65 and ERK phosphorylation and NLRP3 inflammasome activation. Norfloxacin may be a potential candidate for suppressing inflammatory storms caused by Leptospira.

16.
Sci Total Environ ; : 151620, 2021 Nov 12.
Artigo em Inglês | MEDLINE | ID: mdl-34780838

RESUMO

The intertidal wetland ecosystem is vulnerable to environmental and anthropogenic stressors. Understanding how the ecological statuses of intertidal wetlands respond to influencing factors is crucial for the management and protection of intertidal wetland ecosystems. In this study, the community characteristics of bacteria, archaea and microeukaryote from Jiangsu coast areas (JCA), the longest muddy intertidal wetlands in the world, were detected to develop a composite microbial index of biotic integrity (CM-IBI) and to explore the influence mechanisms of stresses on the intertidal wetland ecological status. A total of 12 bacterial, archaea and microeukaryotic metrics were determined by range, responsiveness and redundancy tests for the development of ba-IBI, ar-IBI and eu-IBI. The CM-IBI was further developed via three sub-IBIs with weight coefficients 0.40, 0.33 and 0.27, respectively. The CM-IBI (R2 = 0.58) exhibited the highest goodness of fit with the CEI, followed by ba-IBI (R2 = 0.36), ar-IBI (R2 = 0.25) and eu-IBI (R2 = 0.21). Redundancy and random forest analyses revealed inorganic nitrogen (inorgN), total phosphorus (TP) and total organic carbon (TOC) to be key environmental variables influencing community compositions. A conditional reasoning tree model indicated the close associating between the ecological status and eutrophication conditions. The majority of sites with water inorgN<0.67 mg/L exhibited good statuses, while the poor ecological status was observed for inorgN>0.67 mg/L and TP > 0.11 mg/L. Microbial networks demonstrated the interactions of microbial taxonomic units among three kingdoms decreases with the ecological degradation, suggesting a reduced reliability and stability of microbial communities. Multi-level path analysis revealed fishery aquaculture and industrial development as the dominant anthropogenic activities effecting the eutrophication and ecological degradation of the JCA tidal wetlands. This study developed an efficient ecological assessment method of tidal wetlands based on microbial communities, and determined the influence of human activities and eutrophication on ecological status, providing guidance for management standards and coastal development.

17.
Environ Res ; : 112166, 2021 Oct 04.
Artigo em Inglês | MEDLINE | ID: mdl-34619129

RESUMO

The ecological heterogeneity created by river bends benefits the diversity of microorganisms, which is vital for the pollutant degradation and overall river health. However, quantitative tools capable of determining the interactions among different trophic levels and species are lacking, and research regarding ecological heterogeneity has been limited to a few species. By integrating the multi-species-based index of biotic integrity (Mt-IBI) and the structure equation model (SEM), an interactions-based prediction modeling framework was established. Based on DNA metabarcoding, a multi-species (i.e., bacteria, protozoans, and metazoans) based index of biotic integrity including 309 candidate metrics was developed. After a three-step screening process, eight core metrics were obtained to assess the ecological heterogeneity, quantitatively. The Mt-IBI value, which ranged from 2.08 to 7.17, was calculated as the sum of each single core metric value. The Mt-IBI revealed that the ecological heterogeneity of concave banks was higher than other sites. According to the result of the SEM, D90 was the controlling factor (r = -0.779) of the ecological heterogeneity under the influence of the river bends. The bend-induced redistribution of sediment particle further influenced the concentrations of carbon, nitrogen, and sulphur. The nitrogen group (r = 0.668) also played an essential role in determining the ecological heterogeneity, follow by carbon group (r = 0.455). Furthermore, the alteration of niches would make a difference on the ecological heterogeneity. This multi-species interactions-based prediction modeling framework proposed a novel method to quantify ecological heterogeneity and provided insight into the enhancement of ecological heterogeneity in river bends.

18.
Water Res ; 206: 117730, 2021 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-34619413

RESUMO

The nitrogen (N) cycle is one of the most important nutrient cycles in river systems, and it plays an important role in maintaining biogeochemical balance and global climate stability. One of the main ways that humans have altered riverine ecosystems is through the construction of hydropower dams, which have major effects on biogeochemical cycles. Most previous studies examining the effects of damming on N cycling have focused on the whole budget or flux along rivers, and the role of river as N sources or sinks at the global or catchment scale. However, so far there is still lack of comprehensive and systematic summarize on N cycling and the controlling mechanisms in reservoirs affected by dam impoundment. In this review, we firstly summarize N cycling processes along the longitudinal riverine-transition-lacustrine gradient and the vertically stratified epilimnion-thermocline-hypolimnion gradient. Specifically, we highlight the direct and indirect roles of multi-trophic microbiota and their interactions in N cycling and discuss the main factors controlling these biotic processes. In addition, future research directions and challenges in incorporating multi-trophic levels in bioassessment, environmental flow design, as well as reservoir regulation and restoration are summarized. This review will aid future studies of N fluxes along dammed rivers and provide an essential reference for reservoir management to meet ecological needs.


Assuntos
Microbiota , Rios , China , Ecossistema , Monitoramento Ambiental , Humanos , Nitrogênio , Ciclo do Nitrogênio
19.
Environ Res ; : 112182, 2021 Oct 12.
Artigo em Inglês | MEDLINE | ID: mdl-34648762

RESUMO

Microplastics are frequently detected in natural aquatic systems proximate to populated areas, such as urban rivers and lakes, and can be rapidly colonized by microbial communities. Microplastics and silver nanoparticles (AgNPs) share similar pathways into natural waters and tend to form heteroaggregations. However, very little is known about the long-term impacts on the structure and function of microplastic biofilms when chronically exposed to silver nanoparticles. Thus, the present study assessed the accumulation property of AgNPs on polymethyl methacrylate (PMMA) microplastics via adsorption tests and studied the chronic effects of AgNPs on the structure and function of microplastic biofilms via 30-day microcosmic experiments in eutrophic water. The adsorption tests showed that the biofilms-colonized PMMA microplastics presented the highest adsorption of 0.98 mg/g in the 1 mg/L AgNPs microcosms. After the 30-day exposure, lactic dehydrogenase release and reactive oxygen species generation of PMMA biofilms increased by 33.23% and 23.98% compared to the MPs-control group with no-AgNPs, indicating that the number of dead cells colonizing microplastics significantly increased. Network analysis suggested that the stabilization of the bacterial community declined with the long-term exposure to AgNPs through the reduction of the modularity and average path length of the network. Compared to the MPs-control group, long-term exposure to AgNPs caused cumulatively inhibitory effects on the nitrogen removal and the N2O emissions in eutrophic water. The isotopomer analysis revealed that the contribution rate of NO2- reduction to N2O emissions was gradually increasing with the AgNPs exposure. Real-time PCR analysis showed that denitrification genes were less sensitive to AgNPs than the nitrification genes, with gene nosZ performed the most negligible response. Overall, our results revealed that long-term exposure to AgNPs could alter biogeochemical cycling involved by microplastic biofilms and cumulatively reduce the self-recovery of the eutrophic ecosystem.

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