New insights into functional divergence and adaptive evolution of uncultured bacteria in anammox community by complete genome-centric analysis

Anaerobic ammonium-oxidation (anammox) bacteria play a crucial role in global nitrogen cycling and wastewater nitrogen removal, but they share symbiotic relationships with various other microorganisms. Functional divergence and adaptive evolution of uncultured bacteria in anammox community remain underexplored. Although shotgun metagenomics based on short reads has been widely used in anammox research, metagenome-assembled genomes (MAGs) are often discontinuous and highly contaminated, which limits in-depth analyses of anammox communities. Here, for the first time, we performed Pacific Biosciences high-fidelity (HiFi) long-read sequencing on the anammox granule sludge sample from a lab-scale bioreactor, and obtained 30 accurate and complete metagenome-assembled genomes (cMAGs). These cMAGs were obtained by selecting high-quality circular contigs from initial assemblies of long reads generated by HiFi sequencing, eliminating the need for Illumina short reads, binning, and reassembly. One new anammox species affiliated with Candidatus Jettenia and three species affiliated with novel families were found in this anammox community. cMAG-centric analysis revealed functional divergence in general and nitrogen metabolism among the anammox community members, and they might adopt a cross-feeding strategy in organic matter, cofactors, and vitamins. Furthermore, we identified 63 mobile genetic elements (MGEs) and 50 putative horizontal gene transfer (HGT) events within these cMAGs. The results suggest that HGT events and MGEs related to phage and integration or excision, particularly transposons containing tnpA in anammox bacteria, might play important roles in the adaptive evolution of this anammox community. The cMAGs generated in the present study could be used to establish of a comprehensive database for anammox bacteria and associated microorganisms. These findings highlight the advantages of HiFi sequencing for the studies of complex mixed cultures and advance the understanding of anammox communities.

Potential Role of the Anammoxosome in the Adaptation of Anammox Bacteria to Salinity Stress

The underlying adaptative mechanisms of anammox bacteria to salt stress are still unclear. The potential role of the anammoxosome in modulating material and energy metabolism in response to salinity stress was investigated in this study. The results showed that anammox bacteria increased membrane fluidity and decreased mechanical properties by shortening the ladderane fatty acid chain length of anammoxosome in response to salinity shock, which led to the breakdown of the proton motive force driving ATP synthesis and retarded energy metabolism activity. Afterward, the fatty acid chain length and membrane properties were recovered to enhance the energy metabolic activity. The relative transmission electron microscopy (TEM) area proportion of anammoxosome decreased from 55.9 to 38.9% under salinity stress. The 3D imaging of the anammox bacteria based on Synchrotron soft X-ray tomography showed that the reduction in the relative volume proportion of the anammoxosome and the concave surfaces was induced by salinity stress, which led to the lower energy expenditure of the material transportation and provided more binding sites for enzymes. Therefore, anammox bacteria can modulate nitrogen and energy metabolism by changing the membrane properties and morphology of the anammoxosome in response to salinity stress. This study broadens the response mechanism of anammox bacteria to salinity stress.

The recovery potential and utilization pathway of chemical energy from wastewater pollutants during wastewater treatment in China

Research on the potential for chemical energy recovery and the optimization of recovery pathways in different regions of China is still lacking. This study aimed to address this gap by evaluating the potential and optimize the utilization pathways for chemical energy recovery in various regions of China for achieving sustainable wastewater treatment. The results showed that the eastern and northeastern regions of China exhibited higher chemical energy levels under the existing operating conditions. Key factors affecting chemical energy recovery included chemical oxygen demand removal (ΔCOD), treatment scale, and specific energy consumption (μ) of wastewater treatment plants (WWTPs). Furthermore, the average improvement in the chemical energy recovery rate with an optimized utilization pathway was approximately 40% in the WWTPs. The use of the net-zero energy consumption (NZE) model proved effective in improving the chemical energy recovery potential, with an average reduction of greenhouse gas (GHG) emissions reaching next to 95% in the investigated WWTPs.

[An analysis on clinical characteristics and prognosis-related risk factors in patients with drug-induced liver injury]

Objective: To explore the drugs and clinical characteristics causing drug-induced liver injury (DILI) in recent years, as well as identify drug-induced liver failure, and chronic DILI risk factors, in order to better manage them timely. Methods: A retrospective investigation and analysis was conducted on 224 cases diagnosed with DILI and followed up for at least six months between January 2018 and December 2020. Univariate and multivariate logistic regression analyses were used to identify risk factors for drug-induced liver failure and chronic DILI. Results: Traditional Chinese medicine (accounting for 62.5%), herbal medicine (accounting for 84.3% of traditional Chinese medicine), and some Chinese patent medicines were the main causes of DILI found in this study. Severe and chronic DILI was associated with cholestatic type. Preexisting gallbladder disease, initial total bilirubin, initial prothrombin time, and initial antinuclear antibody titer were independent risk factors for DILI. Prolonged time interval between alkaline phosphatase (ALP) and alanine aminotransferase (ALT) falling from the peak to half of the peak (T(0.5ALP) and T(0.5ALT)) was an independent risk factor for chronic DILI [area under the receiver operating characteristic curve (AUC) = 0.787, 95%CI: 0.697~0.878, P < 0.001], with cutoff values of 12.5d and 9.5d, respectively. Conclusion: Traditional Chinese medicine is the main contributing cause of DILI. The occurrence risk of severe DILI is related to preexisting gallbladder disease, initial total bilirubin, prothrombin time, and antinuclear antibodies. T(0.5ALP) and T(0.5ALT) can be used as indicators to predict chronic DILI.

Motility behavior and physiological response mechanisms of aerobic denitrifier, Enterobacter cloacae strain HNR under high salt stress: Insights from individual cells to populations

The motility behaviors at the individual-cell level and the collective physiological responsive behaviors of aerobic denitrifier, Enterobacter cloacae strain HNR under high salt stress were investigated. The results revealed that as salinity increased, electron transport activity and adenosine triphosphate content decreased from 15.75 μg O2/g/min and 593.51 mM/L to 3.27 μg O2/g/min and 5.34 mM/L, respectively, at 40 g/L, leading to a reduction in the rotation velocity and vibration amplitude of strain HNR. High salinity stress (40 g/L) down-regulated genes involved in ABC transporters (amino acids, sugars, metal ions, and inorganic ions) and activated the biofilm-related motility regulation mechanism in strain HNR, resulting in a further decrease in flagellar motility capacity and an increase in extracellular polymeric substances secretion (4.08 mg/g cell of PS and 40.03 mg/g cell of PN at 40 g/L). These responses facilitated biofilm formation and proved effective in countering elevated salt stress in strain HNR. Moreover, the genetic diversity associated with biofilm-related motility regulation in strain HNR enhanced the adaptability and stability of the strain HNR populations to salinity stress. This study enables a deeper understanding of the response mechanism of aerobic denitrifiers to high salt stress.

Potential role of AgNPs within wastewater in deteriorating sludge floc structure and settleability during activated sludge process: Filamentous bacteria and quorum sensing

Excellent sludge floc structure and settleability are essential to maintain the process stability and excellent effluent quality during the activated sludge process. The underlying effect of silver nanoparticles (AgNPs) within wastewater on sludge floc structure and settleability is still unclear. The potential role of AgNPs in promoting filamentous bacterial proliferation and deteriorating sludge floc structure and settleability based on quorum sensing (QS) were investigated in this study. The results indicated that N-acyl homoserine lactose (AHL) concentration sharply increased from 23.56 to 108.41 ng/g VSS in the sequencing batch reactor with 1 mg/L AgNPs. AgNPs strengthened communication between filamentous bacteria, which triggered the filamentous bacterial QS system involving the synthetic gene hdtS and sensing genes traR and lasR. Filamentous bacterial proliferation was promoted by the triggered QS via positively regulating its cell cycle progression including chromosomal replication and divisome formation. In addition, extracellular protein production was obviously increased from 43.56 to 97.91 mg/g VSS through QS by regulating arginine and tyrosine secretion during filamentous bacterial proliferation under 1 mg/L AgNPs condition, which led to an increase in the negative charge and hydrophily at the cell surface. AgNPs resulted in an obvious increase in the surface energy barrier (WT) between bacteria. The change in the physicochemical properties of extracellular polymeric substance (EPS) induced by QS among filamentous bacteria obviously inhibited bacterial aggregation between filamentous bacteria and floc-forming bacteria under AgNPs condition, thus resulting in serious deterioration of the sludge floc structure and settleability. This study provided new insights into the microcosmic mechanism for the effect of AgNPs on sludge floc structure and settleability.

Factors affecting the accumulation of organotins by wild fish: A case study in the Three Gorges Reservoir, China

Organotin compounds (OTs) accumulate in fish easily, however, research on their influencing factors is still limited. This study collected 25 species of fish with different diets, habitats, and age from the Three Gorges Reservoir (TGR), the largest deep-water river channel-type reservoir in China, and analyzed the accumulation characteristics of OTs in these fish. The results showed that tributyltin (TBT) and triphenyltin (TPhT) were the dominant OTs in fish from the TGR. The correlation between OTs concentration and age, body length, and body weight varied with fish species. The concentrations of TBT and TPhT in carnivorous fish (mean, 25.78 and 11.69 ng Sn/g dw, respectively) were higher than those in other diet fish (P<0.01), but there was no significant difference in fish at different habitat water layers (P>0.05). In addition, the degradation rates of TBT and TPhT in different fish species were all below 50%. In summary, the accumulation of TBT and TPhT in fish is mainly influenced by diet, and both TBT and TPhT were difficult to degrade in fish. These results reveal the pollution characteristics of OTs in fish from the TGR, and can improve our understanding of the factors influencing TBT and TPhT accumulation in freshwater fish.

Unraveling the structure and function of bacterioferritin in Candidatus Kuenenia stuttgartiensis: Iron storage sites maintain cellular iron homeostasis

Anammox bacteria rely heavily on iron and have many iron storage sites. However, the biological significance of these iron storage sites has not been clearly defined. In this study, we explored the properties and location of iron storage sites to better understand their cellular function. To do this, the Candidatus Kuenenia stuttgartiensis iron storage protein, bacterioferritin (K.S Bfr), was successfully expressed and purified. In vitro, correctly assembled globulins were observed by transmission electron microscopy. The self-assembled K.S Bfr has active redox and can bind Fe²⁺ and mineralize it in the protein cavity. In vivo, engineered bacteria with K.S Bfr showed good adaptability to Fe²⁺, with a survival rate of 78.9% when exposed to 5 mM Fe²⁺, compared with only 66.0% for wild-type bacteria lacking K.S Bfr. A potential iron regulatory strategy similar to that of Anammox was identified in transcriptomic analysis of engineered bacteria. This system may be controlled by the iron uptake regulator Furto transport Fe²⁺ via FeoB and store excess Fe²⁺ in K.S Bfr to maintain cellular homeostasis. K.S Bfr has superior iron storage capacity both intracellularly and in vitro. The discovery of K.S Bfr reveals the storage location of iron-rich nanoparticles, increases our understanding of the adaptability of iron-dependent bacteria to Fe²⁺, and suggests possible iron regulation strategies in Anammox bacteria.

Mechanisms of survival mediated by the stringent response in Pseudomonas aeruginosa under environmental stress in drinking water systems: Nitrogen deficiency and bacterial competition

Pseudomonas aeruginosa causes public health problems in drinking water systems. This study investigated the potential role of the stringent response in regulating the adaptive physiological metabolic behaviors of P. aeruginosa to low nitrogen stress and bacterial competition in drinking water systems. The results indicated that guanosine tetraphosphate (ppGpp) concentrations in P. aeruginosa increased to 135.5 pmol/g SS under short-term nitrogen deficiency. Meanwhile, the expression levels of the ppGpp synthesis genes (ppx, relA) and degradation gene (spoT) were upregulated by 37.0% and downregulated by 26.8%, respectively, indicating that the stringent response was triggered. The triggered stringent response inhibited the growth of P. aeruginosa and enhanced the metabolic activity of P. aeruginosa to adapt to nutrient deprivation. The interspecific competition significantly affected the regulation of the stringent response in P. aeruginosa. During short-term nitrogen deficiency, the extracellular polymeric substances concentration of P. aeruginosa decreased significantly, leading to desorption and diffusion of attached bacteria and increased ecological risks. The regulatory effect of stringent response on P. aeruginosa gradually weakened under long-term nitrogen deficiency. However, the expression of pathogenic genes (nalD/PA3310) and flagellar assembly genes (fliC) in P. aeruginosa was upregulated by the stringent response, which increased the risk of disease.

Comprehensive analysis of the fates and risks of veterinary antibiotics in a small ecosystem comprising a pig farm and its surroundings in Northeast China

This study investigated the behavior of veterinary antibiotics (VAs) in a small farm ecosystem. Manure and environmental samples were collected around a large pig farm in northeast China. Thirty-four VAs in six categories were analyzed. Then, a multimedia fugacity model was used to estimate the fates of VAs in the environment. The results showed that VAs were prevalent in manure, soil, water, and sediment, but not in crops. Compared with fresh manure, VA levels were significantly lower in surface manure piles left in the open air for 3-6 months. The main VAs, tetracyclines and quinolones, decreased by 427.12 and 158.45 µg/kg, respectively. VAs from manure piles were transported to the surroundings and migrated vertically into deep soil. The concentrations of ∑VAs detected in agricultural soils were 0.03-4.60 µg/kg; > 94% of the mass inventory of the VAs was retained in soil organic matter (SOM), suggesting that SOM is the main reservoir for antibiotics in soil. Risk assessment and model analysis indicated that the negative impact of mixed antibiotics at low concentrations in farmland on crops may be mediated by indirect effects, rather than direct effects. Our findings highlight the environmental fates and risks of antibiotics from livestock farms.

Effects of physiologic activities of plankton on CO2 flux in the Three Gorges Reservoir after rainfall during algal blooms

The nutrient supply to the freshwater system may be changed by rainfall, which also encourages the cyclic succession of microorganisms. However, in a highly dynamic land-water reservoir, the microbial metabolic changes brought on by the changes of water nutrients following rainfall are not clearly documented. The study selected the Three Gorges Reservoir (TGR) backwater region during algal bloom seasons as the study area and time, and used the Biolog-EcoPlates technique to examine the heterotrophic metabolism conditions of the water before and after rain. The field monitoring assessed how biotic and abiotic variables affected CO₂ flux at the water-air interface. The tests conducted in the laboratory investigated the water-integrated metabolic process was affected by post-rainfall environmental changes. The results showed that the average flux of CO₂ at the water-air interface before rainfall was -489.17 ± 506.66 mg·(m²·d)^-1, while the average CO₂ flux reached 393.35 ± 793.49 mg·(m²·d)^-1 after rainfall. This is mostly explained by the heterotrophic metabolic variability of plankton in response to changes in the aqueous environment brought on by precipitation. These discoveries help us better understand how biological metabolisms after rain affect the CO₂ flux at the water-air interface and reservoir greenhouse gas (GHG) emission equivalents can be evaluated more accurately.

Organotins in a food web from the Three Gorges Reservoir, China: Trophic enrichment and potential health risk

Triphenyltin (TPhT) and tributyltin (TBT) remain widely present in various aquatic environments despite restrictions on their use in many countries for many years. The biomagnification of these compounds in the aquatic food web remains controversial. This study reports the bioaccumulation of TPhT and TBT in aquatic animals in the Three Gorges Reservoir (TGR), a deep-water river channel-type reservoir and the largest reservoir in China. We measured TPhT, TBT and their metabolites in 2 invertebrates, 27 fish and the aquatic environment. The logarithmic bioaccumulation factors of TPhT and TBT were 4.37 and 3.77, respectively, indicating that TPhT and TBT were enriched in organisms of the TGR. Both TPhT and TBT concentrations were significantly and positively correlated with trophic level, with trophic magnification factors of 3.71 and 3.63, respectively, indicating that TPhT and TBT exhibited similar trophic enrichment in the freshwater food web of the TGR. The results of health risk assessment showed that although all hazard index (HI) values were <1, more attention should be paid to the health risk to children associated with consumption of aquatic products (HI = 0.67). This study provides powerful evidence of trophic enrichment of TPhT and TBT in a freshwater food web in a deep-water river channel-type reservoir and provides valuable data regarding organotins in aquatic animals in the TGR.

Proteomics reveals the enhancing mechanism for eliminating toxic hydroxylamine from water by nanocompartments containing hydroxylamine oxidase

Hydroxylamine (NH₂OH) is a potentially toxic pollutant when it is present in water, as it can damage both bacteria and the human body. It is still difficult to eliminate the toxic NH₂OH in water. Here, we showed that the model bacterium (Escherichia coli) with nanocompartments encapsulated with hydroxylamine oxidase (HAO) can remove NH₂OH from water. In addition, the removal efficiency of NH₂OH by genetically modified bacteria (with HAO-nanocompartments) was 3.87 mg N L^-1 h^-1, and that of wild-type bacteria (without HAO-nanocompartments) was only 1.86 mg N L^-1 h^-1. Label-free quantitative proteomics indicated that the nanocompartments containing HAO enhanced bacterial activity by inducing the up-regulation of proteins involved in stress and stimulus responses, and decreased their intracellular NH₂OH concentration. Moreover, the synthesis of proteins involved in energy metabolism, gene expression, and other processes in bacterial was enhanced under hydroxylamine stress, and these changes increased the resistance of bacterial to NH₂OH. This work can aid our understanding of the toxic effects of NH₂OH on bacteria as well as the development of new approaches to eliminate NH₂OH in water.

[Distribution Characteristics of Soil Phosphorus Forms and Phosphatase Activity at Different Altitudes in the Soil of Water-Level-Fluctuation Zone in Pengxi River, Three Gorges Reservoir]

Phosphatases play important roles in converting organic phosphorus into inorganic phosphorus in soil. However, studies from this perspective on the water-level-fluctuation zone (WLFZ) of the Three Gorges Reservoir are limited. In this study, phosphatase activity and the forms of phosphorus were analyzed. Soil samples were collected in the river basin of the Penxi River in the WLFZ during a drying period. The correlation between phosphatase activity and phosphorus forms and the impacts of phosphatase activity on the phosphorus forms were analyzed. The results showed that the contents of H₂O-P_i, NaHCO₃-P_i, and NaOH-P_i in the soils of the WLFZ were higher than those in the soils by the river. In addition, a higher altitude resulted in higher contents of bio-enzymatically hydrolysable phosphorus and NaOH-P_o. Furthermore, redundancy analysis (RDA) showed that the contents of organic matter and amorphous Fe and Mn were the main factors affecting soil organic phosphorus forms. The average activities of acid phosphomonoesterase (ACP), alkaline phosphomonoesterase (ALP), phosphodiesterase (PDE) (all in p-NP), and phytase (PAE) (in P) in the soils of the WLFZ were 1.40, 2.60, 0.44, and 11.43 μmol·(g·h)^-1, respectively. Moreover, the activities of different phosphatases increased with altitude. Soil plant biomass and microbial biomass were important reasons for the difference in spatial distribution of phosphatase activity in the soil of the WLFZ. Phosphatase activities were significantly positively correlated with the contents of organic phosphorus forms but negatively correlated with the content of bioavailable phosphorus. A higher soil phosphatase activity and a lower content of bioavailable phosphorus were usually detected in soil samples taken at a higher altitude. In the early stage of flooding, phosphatase converted organic phosphorus into inorganic phosphorus at a relatively high rate, and the risk of phosphorus release to the overlying water body was also high. This study contributed to a comprehensive understanding of the geochemical cycle of soil phosphorus in the soil of the WLFZ.

Biofilm formation during wastewater treatment: Motility and physiological response of aerobic denitrifying bacteria under ammonia stress based on surface plasmon resonance imaging

A bacterial image analysis system based on surface plasmon resonance imaging was established to investigate the effect of bacterial motility on biofilm formation under high ammonia nitrogen at the single-cell level. The results showed that the bacterial mean rotation speed and vertical motility distance decreased with the increasing concentration of ammonia nitrogen. Ammonia nitrogen inhibited the metabolic activity of the bacteria, decreasing bacterial motility. Bacterial motility was negatively correlated with the biofilm-formation ability. The biofilm formation ability of Enterobacter cloacae strain HNR exposed to ammonia nitrogen was enhanced by reducing its movement and promoting EPS secretion. Genes related to the tricarboxylic acid cycle and oxidative phosphorylation were down-regulated, indicating inhibition of microbial energy metabolism. Genes related to bacterial secretion and lipopolysaccharide synthesis were up-regulated, facilitating the formation of biofilms and enabling the bacteria to resist ammonia nitrogen stress. This study provides new insights into the biofilm formation under ammonia stress.

The GHG mitigation opportunity of sludge management in China

Greenhouse gas (GHG) mitigation in wastewater treatment sector is indispensable in China's carbon neutral target. As an important component of wastewater system, sludge generation is rapidly increased with the acceleration of urbanization in China. It is crucial to investigate the carbon footprint of various sludge management strategies and quantify the potential optimization of GHG reduction effect at national scale. Therefore, this study conducted a comprehensive analysis of sludge distribution and GHG profiles of various sludge systems. The overall dry sludge generation in China is 12.15 Mt, with spatial resolution at city level. Different sludge treatment options were categorized into four types: energy recovery, nutrient recovery (e.g. phosphorus and nitrogen), material valorisation (e.g. brick, biochar) and conventional disposal. With various sludge treatment options, the GHG profile of annual sludge management in China ranges from -35.86 Mt/year to 57.11 Mt/year. The best GHG mitigation can be achieved through energy recovery by co-incineration system and the greatest reduction opportunity is concentrated in highly urbanized regions, such as Yangtze River Delta, Pearl River Delta, and Beijing-Tianjin-Hebei urban agglomerations.

Occurrence, seasonal variation, potential sources, and risks of organophosphate esters in a cold rural area in Northeast China

Organophosphate esters (OPEs) in the environment have been the focus of increasing attention due to their ubiquity and potential toxicity. However, there is little information on the occurrence and characteristics of OPEs in rural areas, especially those with cold year-round temperatures and frozen soil in winter. In this study, environmental samples were collected, in summer and winter, from villages and towns in Northeast China differing in the types and intensities of their anthropogenic activities. The samples were analyzed for 12 OPEs. The results showed the widespread presence of alkyl-OPEs, Cl-OPEs, and aryl-OPEs in the water, soil, snow, and ice of the study sites. In summer, tris(1-chloro-2-propyl) phosphate (TCPP) and tris(2-chloroethyl) phosphate (TCEP) were the primary compounds in water and soil, respectively. The ∑₁₂OPE concentration in three villages varied from 46.26 to 257.37 ng/L in water, and from 6.62 to 19.46 ng/g in soils. The ∑₁₂OPE concentrations in water were lower in winter than summer, but conversely, ∑₁₂OPE concentrations in frozen soils in winter were higher than those in soils in summer. In winter, there was a shift in the predominant OPEs in water and frozen soils, with dominance of TCEP and complex compounds, respectively. Obvious seasonal characteristics of the potential sources and ecological risks of OPEs in these areas were also determined, with more complex sources of OPEs seen in summer than winter. In summer, only 2-ethylhexyl diphenyl phosphate (EHDPP) in water posed a potential risk, while in summer and, especially, in winter, EHDPP and tris(2-ethylhexyl) phosphate posed potential risks in soils. The high ∑₁₂OPE concentration in snow (56.77 ng/L) implied that wet deposition can amplify OPEs in other environmental compartments. This is the first systematic report on OPEs in a cold rural area. Our findings highlight the need for seasonal monitoring of OPEs in similar areas.

Encapsulins from Ca. Brocadia fulgida: An effective tool to enhance the tolerance of engineered bacteria (pET-28a-cEnc) to Zn2

Zn²⁺ is largely discharged from many industries and poses a severe threat to the environment, making its remediation crucial. Encapsulins, proteinaceous nano-compartments, may protect cells against environmental stresses by sequestering toxic substances. To determine whether hemerythrin-containing encapsulins (cEnc) from anammox bacteria Ca. Brocadia fulgida can help cells deal with toxic substances such as Zn²⁺, we transferred cEnc into E.coli by molecular biology technologies for massive expression and then cultured them in media with increasing Zn²⁺ levels. The engineered bacteria (with cEnc) grew better and entered the apoptosis phase later, while wild bacteria showed poor survival. Furthermore, tandem mass tag-based quantitative proteomic analysis was used to reveal the underlying regulatory mechanism by which the genetically-engineered bacteria (with cEnc) adapted to Zn²⁺ stress. When Zn²⁺ was sequestered in cEnc as a transition, the engineered bacteria presented a complex network of regulatory systems against Zn²⁺-induced cytotoxicity, including functions related to ribosomes, sulfur metabolism, flagellar assembly, DNA repair, protein synthesis, and Zn²⁺ efflux. Our findings offer an effective and promising stress control strategy to enhance the Zn²⁺ tolerance of bacteria for Zn²⁺ remediation and provide a new application for encapsulins.

New insight into filamentous sludge bulking: Potential role of AHL-mediated quorum sensing in deteriorating sludge floc stability and structure

The microcosmic mechanisms underlying filamentous bulking remain unclear. The role of extracellular polymeric substances (EPS) governed by quorum sensing (QS) in deteriorating sludge floc stability and structure during filamentous bulking and the feasibility of using quorum quenching (QQ) to maintain sludge floc stability and structure and sludge settling were investigated in this study. The results indicated that the concentration of C₆HSL increased from 22.08±3.22 ng/g VSS to 81.42±5.98 ng/g VSS during filamentous bulking. The filamentous bacteria gradually evolved the hdtS gene related to the synthesis of C₆HSL with increases in the population density. Triggered QS by filamentous bacteria proliferation induced variation in the composition and structure of EPS within the sludge flocs. The proteins (PN) content of the EPS increased evidently from 40.06 ± 2.41 mg/g VSS to 110.32 ± 4.32 mg/g VSS, and the polysaccharides (PS) content slightly increased during filamentous bulking. The upregulated proteins in the EPS led to a decrease in the relative hydrophobicity of the sludge and an increase in negative surface charge. The α-helix/(β-sheet+random coil) ratio evidently increased from 0.76 to 0.99 during filamentous bulking, revealing that the proteins were tightly structured, which prevented the exposure of inner hydrophobic groups. The total energy of the interaction (W_T) between bacteria increased during sludge bulking, which resulted in the weakening of sludge aggregation. Variation in the physicochemical properties of EPS induced by QS in the filamentous bacteria markedly restrained adhesion between the filamentous bacteria and floc-forming bacteria. The production of PN in the EPS and the expression of the hdtS gene were inhibited by vanillin, which served as a QS inhibitor. The W_T between bacteria with 50 mg/L of vanillin basically did not change. Filamentous bulking was significantly inhibited by the addition of vanillin. Therefore, QQ is a potential strategy for the prevention and control of filamentous bulking. This study provides new information regarding the microcosmic mechanisms of filamentous bulking.

Insight into the structure and metabolic function of iron-rich nanoparticles in anammox bacteria

Anaerobic ammonium-oxidizing (anammox) bacteria are iron abundant and depend heavily on iron-binding proteins. The iron demand of anammox bacteria is relatively large. However, it still remains some doubts where these large quantities of available iron come from and how they are regulated in anammox bacteria. Herein, iron-rich nanoparticles in anammoxosomes were detected by synchrotron soft X-ray tomography coupled with scanning transmission X-ray microscopy (STXM). The iron-rich nanoparticles were identified as ferric oxide (α-Fe₂O₃) mineral cores, and the local atomic structure of iron-rich nanoparticles was obtained by X-ray absorption fine-structure (XAFS) spectra. The bacterioferritin of Q1Q315 and Q1Q5F8 were detected by proteomics analysis. On this basis, the metabolic pathway centered on iron-rich nanoparticles was proposed.

Occurrence, potential sources and risks of organophosphate esters in the high-elevation region, Tibet, China

Organophosphate esters (OPEs) are widely used flame retardants that are frequently released into the environment, causing potential harm to humans and ecosystems. Tibet is located on the Tibetan Plateau, known as the "roof of the world", but the occurrence of OPEs in Tibet remains unclear. This is the first report of the occurrence, potential sources and risks of 12 OPEs in water, soil, sediment and snow from Xainza, a typical town at high-elevation in Tibet (average elevation = 4700 m). Ten OPEs were observed, with ∑OPE concentrations of 46.45-1744.73 ng/L in surface water, 29.74-73.85 ng/g in soil, and 13.30-32.23 ng/g in sediment. Moreover, the mean ∑OPE concentration in snow was 413.90 ng/L. Tris (2-chloroethyl) phosphate (TCEP) and tris (2-chloroisopropyl) phosphate (TCPP) were the main OPEs in surface water and snow, while 2-ethylhexyl diphenyl phosphate (EHDPP) was dominant in soil and sediment. Local human activities and long-distance atmospheric transport may be the main sources of OPEs in Xainza. The assessment of ecological risk indicated that EHDPP in soil poses potential risk. The occurrence of OPEs in Xainza showed that more attention should be paid to persistent organic pollutants in high-elevation regions.

[Regulatory effects of microRNAs on hepatic stellate cell activation and liver fibrogenesis]

Hepatic fibrogenesis (HF) is the common consequence of various chronic liver diseases (CLD) induced by a variety of pathogenic factors. The mechanism of HF involves the interactions within different types of liver cells, cytokines, chemokines, cell mediators and multiple signaling pathways in a way of networks. As a result, excessive production and deposition of extracellular matrix (ECM) mainly composed of type I and type III fibril forming collagen destroys the original morphology, structure and function of the liver. The activation of hepatic stellate cells (HSCs), the major scar forming cells in liver, plays a crucial role in hepatic fibrogenesis. MicroRNAs are a group of short, single stranded, non-coding RNAs that can inhibit mRNA expression at the transcriptional and post transcriptional levels. They can be loaded and transferred as cargos by exosomes, to regulate the function of nearby and distant receptive cells. The expressions of many microRNAs such as miR-21, miR-29, miR-708, miR-101, miR-455, miR-146, miR-193 change significantly in activated HSCs, which regulate the activation, fibrogenic function, proliferation, apoptosis and autophagy of HSCs via affecting target genes expression and signaling pathway molecules. They are important substances and regulatory mechanism that mediate the initiation and progression of HF.

Potential role of nanobubbles in dynamically modulating the structure and stability of anammox granular sludge within biological nitrogen removal process

The generation of visible macrobubbles considerably affects the structure and function of anammox granules in the anammox granular sludge (AnGS) system. However, the existence of nanobubbles (NBs) and their role in maintaining the AnGS structure and stability are unclear because of the complexity of the system and lack of effective analytical methods. In this study, methods for NB analysis and assessment of their effects were developed to investigate the formation and characteristics of NBs in an AnGS system and the effects of NBs on the properties and function of AnGS. The results indicated that dissolved gas supersaturation caused by AnGS generated NBs of 2.75 × 10⁸ bubbles/mL inside an AnGS reactor after running for 300 min at 30 °C. The increasing absolute value of the zeta potential of NBs with time indicated that the NBs in the AnGS system were gradually stable. The size of the stable NBs ranged from 150 nm to 400 nm. NB formation also increased the space and pressure between cells, leading to the breakage of the cell cluster and causing structural changes in granules. Changes in the local granular microstructure caused by NBs were favorable for the porous structure of granules to avoid granular disintegration and flotation caused by the excessive secretion of extracellular polymeric substances blocking gas channels. The formation and stability of NBs penetrating the cell clusters played a crucial role in the formation and stability of nanopores around or inside the cell clusters, further providing a basis for the formation of high-porosity structures and efficient mass transfer of AnGS.

[Effect of occupational stress on depression in gas field workers]

Objective: To explore the occurrence level of depressive symptoms and it's influencing factors among gas field workers. Methods: In October 2018, a cross-sectional study was conducted in 1726 gas field workers from a gas field by using cluster sampling method. Questionaire was used to evaluate the individual factors, depressive symptoms, occupational stress factors and stress regulatory factors. The correlation between depressive symptoms and occupational stress was analyzed. Multivariate logistic regression was used to analyze the influencing factors of depressive symptoms. Results: The depressive symptoms score of gas field workers was 12.00 (7.00, 19.00) point. Correlation analysis revealed that depressive symptoms score was positively related to sleep disorders (r=0.598) , effort (r=0.186) , daily tension (r=0.478) , negative affectivity (r=0.565) , social support (r=0.446) and monotony of work (r=0.484) (P<0.01) . And it was negatively related to reward (r=-0.386) , work stability (r=-0.294) , promotion opportunities (r=-0.258) , positive affectivity (r= -0.310) , self-efficacy (r=-0.312) , contral strategy (r=-0.268) , support strategy (r=-0.209) and job satisfaction (r=-0.398) (P<0.01) . Multivariate logistic regression analysis revealed that sleep disorder, high negative affectivity, low support from colleagues, low support from family, high monotony of work and high daily tension were the risk factors for depressive symptoms of gas field worker (OR=3.423, 95%CI: 2.644-4.397; OR=2.847, 95%CI: 2.200-3.683; OR=1.646, 95%CI: 1.215-2.116; OR=1.496, 95%CI: 1.164-1.923; OR=1.578, 95%CI: 1.227-2.303; OR=1.903, 95%CI: 1.480-2.440; P<0.01) . High work stability, high self-efficacy and high job satisfaction were protective factors for depressive symptoms of gas field workers (OR=0.752, 95%CI: 0.591-0.958; OR=0.590, 95%CI: 0.465-0.749; OR=0.718, 95%CI: 0.516-0.999; P<0.05) . Conclusion: Occupational stress factors have a great influence on the depressive symptoms of gas field workers. Increased work stability, self-efficacy and job satisfaction could reduce the risk of depressive symptoms.

Adaptation mechanism of aerobic denitrifier Enterobacter cloacae strain HNR to short-term ZnO nanoparticle stresses

The adaptation mechanism of a wild type (WT) and resistant type (Re) strain of the aerobic denitrifier Enterobacter cloacae strain HNR to short-term ZnO nanoparticle (NP) stresses was investigated. The results showed that Re maintained higher nitrite reductase (NIR) and nitrate reductase (NR) activities and showed lower increment of reactive oxygen species (ROS) than WT, under ZnO NP stresses. The affinity constant (K_A) of WT to Zn²⁺ was 5.06 times that of Re, indicating that Re was more repulsive to Zn²⁺ released by ZnO NPs. Transcriptomic analysis revealed that the up-regulation of the nitrogen metabolism of Re helped maintain NIR and NR activities, that the enhancement of purine metabolism lowered the intracellular ROS increment, and that the up-regulation of cationic antimicrobial peptide resistance contributed to the lower K_A of Re to Zn²⁺. These findings provided new insights into the adaptation mechanism of aerobic denitrifying bacteria to ZnO NPs.

Bacterially self-assembled encapsulin nanocompartment for removing silver from water

Compartmentalization can protect cells from the interference of external toxic substances by sequestering toxic products. We hypothesized that proteinaceous nanocompartments may be a feasible candidate material to be added to genetically modified bacteria for the sequestration of toxic environmental products, which would open up a new bioremediation pathway. Here, we showed that the model bacterium (Escherichia coli) with self-assembling nanocompartments can remove silver (Ag) from water. Transmission electron microscopy and energy dispersive X-ray (TEM-EDX) analysis showed that the nanocompartments combined stably with silver in vitro. In addition, when exposed to 30 μM AgNO₃, the survival rate of genetically modified bacteria (with nanocompartments) was 86%, while it was just 59% in the wild-type bacteria (without nanocompartments). Label-free quantitative proteomics indicated that the nanocompartments enhanced bacterial activity by inducing the up-regulation of protein processing and secondary metabolites, and decreased their intracellular silver concentration, both of which contributed to their increased resistance to toxic silver. This study on nanocompartments has contributed to a deeper understanding of how bacteria respond to environmental stressors like heavy metal pollutants in water. The technology promises to provide a new strategy for recycling heavy metals from sewage.

The role of morphological changes in algae adaptation to nutrient stress at the single-cell level

Individual cell heterogeneity within a population can be critical to its peculiar function and fate. Conventional algal cell-based assays mainly analyze the average responses from a population of algal cells. Therefore, the mechanisms through which changes in population characteristics are driven by the behavior of single algal cells are still not well understood. Algal cells may modulate their physiology and metabolism by changing their morphology in response to environmental stress. In this study, an algal single-cell culture and analysis system was developed to investigate the potential role of morphological changes by algal cells during adaptation to nutrient stress based on a microwell array chip. The surface-to-volume ratio of Microcystis aeruginosa (M. aeruginosa) and the volume of Scenedesmus obliquus (S. obliquus) significantly increased with increasing culture time under nutrient stress. The eccentricity of M. aeruginosa and S. obliquus gradually increased and decreased, respectively, with increasing culture time, indicating that the morphology of M. aeruginosa and S. obliquus became increasingly irregular and regular, respectively, under nutrient stress. There were significant correlations between the morphological characteristics and physiological characteristics of M. aeruginosa and S. obliquus under nutrient stress. In M. aeruginosa, an increased surface-to-volume ratio facilitated a high specific fluorescence intensity, specific Raman intensity, and maximum electron transport rate. In S. obliquus, increased cell volume enhanced nutrient absorption, which facilitated a higher specific growth rate. M. aeruginosa and S. obliquus adopted different adaptation strategies in response to nutrient stress based on morphological changes. These findings facilitate the development of management strategies for controlling harmful cyanobacterial blooms.

[Correlation between social support and occupational stress among gas production workers in the field]

Objective: To investigate the level of social support and its correlation with occupational stress among gas production workers in the field. Methods: In October 2018, the cluster sampling method was used to perform a cross-sectional survey for 1726 gas production workers in the field, and related data of these workers were collected, including age, education level, marital status, level of social support, and related factors for occupational stress. A Spearman's rank correlation analysis was used to investigate the correlation between social support and occupational stress, and the levels of occupational stress-related factors were compared between the groups with different social support scores. Results: The gas production workers in the field had a median (25th percentile, 75th percentile) social support score of 24.00 (19.00, 28.00) , and there was a significant difference in social support score between the workers with different posts or work shifts (P<0.01) . Social support score was positively correlated with effort, daily stress, negative emotion, and job routinization (P<0.05) and was negatively correlated with job satisfaction, reward, working stability, and promotion opportunity (P<0.05) . The group with a high social support score had significantly higher scores of effort, job routinization, sleep disorders, and daily stress than the other two groups (P<0.01) , and the group with a low social support score had significantly higher scores of reward, self-efficacy, positive affection, and job satisfaction than the other two groups (P<0.01) . Conclusion: High-level social support plays an important role in alleviating occupational stress and protecting mental health among gas production workers in the field.

Bioavailability of organic phosphorus in the water level fluctuation zone soil and the effects of ultraviolet irradiation on it in the Three Gorges Reservoir, China

Ultraviolet (UV) irradiation is an abiotic pathway for the transformation of complex phosphorus (P) components into inorganic P in ecosystems. To explore the effect of UV irradiation on organic P (OP) bioavailability in the water level fluctuation zone (WLFZ) soil, we collected representative soil samples from WLFZ of the Pengxi River, a tributary of the TGR, China. We determined the contents of different forms of OP in the WLFZ soil through sequential extraction. The bioavailability of different forms of OP and the effect of UV light were characterised using a combination of enzymatic hydrolysis and UV irradiation. The OP contents of the different extracts (P_o) were ranked as NaOH-P_o > NaHCO₃-P_o > H₂O-P_o, whereas those of enzymatically hydrolysable organic P (EHP) were ranked as NaOH-EHP > NaHCO₃-EHP > H₂O-EHP. UV irradiation was found to improve OP bioavailability, as demonstrated by increased levels of UV-sensitive P (UV-P) and EHP in the extracts after irradiation. The total contents of bioavailable P_o in extracts were 5.6-35.3% higher after UV irradiation than before irradiation. Thus, the effect of UV irradiation on the OP bioavailability and release activity cannot be neglected in TGR WLFZ soil.

[Effect of Hydroxylamine on Community of ANAMMOX Sludge]

At present, the anaerobic ammonium oxidation (ANAMMOX) process has the advantages of high efficiency, low energy consumption, and low sludge quantity, and it therefore has broad application prospects in sewage nitrogen removal. Hydroxylamine is not only an intermediate product of ANAMMOX metabolism but also an inhibitor. However, the effect of hydroxylamine on the activity of ANAMMOX is not clear. Therefore, we investigated the ANAMMOX activity under the condition of adding different concentrations of hydroxylamine (40-80 mg·L^-1) through a hydroxylamine batch experiment. It was found that hydroxylamine can inhibit ANAMMOX activity. However, it was impossible to determine the threshold of ANAMMOX bacteria to hydroxylamine. Next, the mRNA levels of hydrazine oxidase (HZO) in different reactors were detected by real-time fluorescent quantitative polymerase chain reaction (RT-qPCR), and it was found that the expression levels of HZO peak and then decrease with an increase of hydroxylamine concentration. It was suggested that the tolerated hydroxylamine concentration was within 60-70 mg·L^-1 for 3.12 g·L^-1 ANAMMOX granular sludge. Moreover, a 16S rRNA high-throughput sequencing method was used to analyze the structure and function of ANAMMOX granules in microbial communities in the reactor. It was found that the addition of an appropriate concentration of hydroxylamine (50 mg·L^-1) helped to enhance the cellular motility of bacteria and promoted the composition of ANAMMOX bacteria, providing a better ecological balance.

New insights into nitrous oxide emissions in a single-stage CANON process coupled with denitrification: thermodynamics and nitrogen transformation

The dynamic characteristics of N₂O emissions and nitrogen transformation in a sequencing batch biofilm reactor (SBBR) using the completely autotrophic nitrogen removal over nitrite (CANON) process coupled with denitrification were investigated via ¹⁵N isotope tracing and thermodynamic analysis. The results indicate that the Gibbs free energy (ΔG) values of N₂O production by the nitrifier denitrification and heterotrophic denitrification reactions were greater than that of NH₂OH oxidation, indicating that N₂O was easier to produce via either nitrifier and heterotrophic denitrification than via NH₂OH oxidation. Ammonia-oxidizing bacteria (AOB) denitrification exhibited a higher f_s ⁰ (the fraction of electron-donor electrons utilized for cell synthesis) than NH₂OH oxidation. Therefore, AOB preferred the denitrification pathway because of its growth advantage when N₂O was produced by the AOB. The N₂O emissions by hydroxylamine oxidation, AOB denitrification and heterotrophic denitrification in the SBBRs using different C/N ratios account for 5.4-7.6%, 45.2-60.8% and 33.8-47.2% of the N₂O produced, respectively. The total N₂O emission with C/N ratios of 0, 0.67 and 1 was 228.04, 205.57 and 190.4 μg N₂O-N·g^-1VSS, respectively. The certain carbon sources aid in the reduction of N₂O emissions in the process.

New insights into filamentous sludge bulking: The potential role of extracellular polymeric substances in sludge bulking in the activated sludge process

The control of filamentous sludge bulking has been regarded as an important issue in the activated sludge process due to there is still a lack of understanding of the bulking mechanisms. In this study, changes in the extracellular polymeric substances (EPS) and metabolic profile of bulking sludge based on the proteomics level was investigated to reveal the potential role of EPS in deteriorating sludge floc stability and structure during filamentous bulking. The results showed that the EPS content gradually decreased from 210.23 mg/g volatile suspended solids (VSS) to 131.34 mg/g VSS during sludge bulking. The protein (PN) content of the EPS significantly decreased from 173.33 mg/g VSS to 95.42 mg/g VSS during sludge bulking. However, a gradual increase in polysaccharides (PS) was observed. Bacterial aggregation was hindered by the changes in the EPS and its components. The excessive proliferation of filamentous bacteria had a significant effect on the molecular functions of the extracellular PN and metabolic pathways of the EPS. The proteins associated with the hydrophobic amino acid synthesis decreased, whereas the proteins associated with the hydrophilic amino acid synthesis increased during sludge bulking. Electric repulsion was the key factor affecting the aggregation and flocculation ability of the bacteria during sludge bulking. The changes in the EPS and its components induced by the excessive proliferation of filamentous bacteria resulted in a loose floc structure and poor settling performance during sludge bulking. These findings provide new insights into sludge bulking during the activated sludge process.

A self-assembled nanocompartment in anammox bacteria for resisting intracelluar hydroxylamine stress

Anammox bacteria play an important role in the global nitrogen cycle, but research on anammoxosome structure is still in its initial stages. In particular, the anammox bacteria genome contains nanocompartments gene loci. However, the function and structure of the nanocompartments in anammox bacteria is poorly understood. We apply genetic engineering to demonstrate the self-assembled nanocompartments of anammox bacteria. The encapsulin shell protein (cEnc) and cargo protein hydroxylamine oxidoreductase (HAO) can self-assemble to form regular nanocompartments (about 128 nm in diameter) in vitro. Cell growth curve tests show that nanocompartments help model bacteria resist hydroxylamine (NH₂OH) stress. Batch test results and transcriptional data show that cEnc and HAO are highly expressed in response to the negative effects of NH₂OH on anammox efficiency, predicting a potential role of nanocompartments in helping anammox bacteria resist NH₂OH stress. These findings improve our understanding of the mechanisms by which anammox bacteria respond to harmful environmental metabolites.

Quantitative three-dimensional nondestructive imaging of whole anaerobic ammonium-oxidizing bacteria

Anaerobic ammonium-oxidizing (anammox) bacteria play a key role in the global nitrogen cycle and in nitrogenous wastewater treatment. The anammox bacteria ultrastructure is unique and distinctly different from that of other prokaryotic cells. The morphological structure of an organism is related to its function; however, research on the ultrastructure of intact anammox bacteria is lacking. In this study, in situ three-dimensional nondestructive ultrastructure imaging of a whole anammox cell was performed using synchrotron soft X-ray tomography (SXT) and the total variation-based simultaneous algebraic reconstruction technique (TV-SART). Statistical and quantitative analyses of the intact anammox bacteria were performed. High soft X-ray absorption composition inside anammoxosome was detected and verified to be relevant to iron-binding protein. On this basis, the shape adaptation of the anammox bacteria response to iron was explored.

[Removal of BPA and EE2 from Water by Mn-Fe Embedded in Acicular Mullite]

Acicular mullite was modified by ferromanganese binary metal oxide (Mn-Fe) to improve the removal efficiency of endocrine disruptors by traditional water treatment practices, using the commercial ceramsite for comparison. The physicochemical properties of synthesized samples were characterized, and batch adsorption experiments were carried out to study the adsorption efficiency of bisphenol A (BPA) and 17α-ethinylestradiol (EE2) on synthesized samples, investigating how solution chemistry and regeneration may affect the adsorption efficiency. Results show that the manganese oxide loaded on the acicular mullite was manganite with an average particle size of 450 nm. After Mn-Fe impregnation, the specific surface area, cumulative pore volume, and mesoporous ratio of the acicular mullite were significantly increased. The virgin acicular mullite had no removal ability for BPA and EE2, and the removal efficiency of BPA and EE2 by Mn-Fe impregnated acicular mullite were significantly increased. Acicular mullite was more suitable as support material for modified filter material. The adsorption kinetics of BPA and EE2 on Mn-Fe-M were fitted with the intra-particle diffusion model, and found to be mainly affected by intra-particle diffusion. The isothermal adsorption data was best fitted to the Langmuir-Freundlich model, and the maximum adsorption capacities of BPA and EE2 were 5.043 mg·g^-1 and 3.990 mg·g^-1, respectively. Thermodynamic experiments showed that the adsorption of BPA and EE2 by Mn-Fe embedded in acicular mullite was an endothermic reaction, and the temperature increase is beneficial to the adsorption. The adsorption amount of BPA and EE2 on Mn-Fe embedded in acicular mullite decreased with increasing pH. The increase of ionic strength favored the adsorption removal of BPA and EE2. The co-existing anion of SO₄^2- promoted the adsorption of both BPA and EE2, while CO₃^2- and PO₄^3- inhibited the adsorption of both BPA and EE2 on Mn-Fe embedded in acicular mullite. The adsorbent regeneration test showed that Mn-Fe embedded acicular mullite was an easily recyclable adsorbent. Mn-Fe embedded in high-porosity acicular mullite can effectively remove typical endocrine disruptors in water, and it can be potentially extensively used to alleviate the problem of low removal efficiency of endocrine disrupting chemicals in traditional water treatment practice.

Sludge reduction based on microbial metabolism for sustainable wastewater treatment

Sludge reduction via microbial metabolism does not require extra energy and resource inputs and thus merits attention as an alternative approach for sustainable wastewater treatment. This review presents a summary and analysis of the existing literatures on sludge reduction based on microbial metabolism, as well as interprets these sludge reduction mechanisms using bacterial thermodynamics and stoichiometry. Future efforts should be directed toward using advanced analytical techniques to further reveal sludge reduction mechanisms. The feasibility of coupling sludge reduction and nutrient removal by microorganism metabolism needs to be further evaluated to minimize the effect of sludge reduction on nutrient removal. A comprehensive life cycle assessment of sludge reduction strategies is recommended to effectively confirm their sustainability. Full-scale research is needed to verify the results obtained from bench- and pilot-scale experiments. This review presents the future opportunities and challenges for sludge reduction based on microbial metabolism in the excess sludge disposal.

[The application of non-selective β-blockers, angiotensin receptor antagonists and statins in liver cirrhotic patients]

Portal hypertension is the major cause of complications in decompensated liver cirrhosis. Research results showed that non-selective β-blockers, angiotensin receptor antagonists, and statins can improve portal hypertension by reducing portal vein blood flow and intrahepatic resistance, and have certain prevention and treatment effect on hemodynamic disorders and portal hypertensive complications in chronic liver diseases. Herein, we review the mechanism of action, clinical effects and limitations of these three types of drugs on portal hypertension of cirrhosis.

[Characteristics of Nitrogen and Phosphorus Losses and Runoff in a Typical Purple Soil Watershed in the Three Gorges Reservoir Area]

To understand the runoff pollution characteristics of the typical purple soil small watershed in the Three Gorges Reservoir (TGR), the rainfall-runoff duration under typical land use types of the Xinzheng watershed and the nitrogen (N) and phosphorus (P) concentrations in the outlet runoff of each catchment were dynamically monitored, and the loss rule of N and P in the rainfall runoff in the small watershed in the TGR was investigated and analyzed. The results showed that the losses of runoff N and P were 13.69 kg·(hm²·a)^-1 and 1.50 kg·(hm²·a)^-1, respectively. N and P in agricultural fertilizers and rainfall scouring were the main causes of runoff pollution in the Xinzheng watershed. The average concentration of total nitrogen (TN) and total phosphorus (TP) reached 10.05 mg·L^-1 and 1.10 mg·L^-1, far exceeding the occurrence standard of eutrophication, which should be cause for concern. The nitrate nitrogen (NN) and particulate phosphorus (PP) in the rainfall were 69.47 kg and 6.83 kg on August 15, 2010, accounting for 53.91% and 53.78% of TN and TP, respectively. The NN and AN were 6.68 kg and 5.61 kg, respectively, in the rainfall on August 26, 2010, accounting for 37.74% and 31.69% of TN and PP was 1.36 kg, accounting for 57.63% of TP, indicating that nitrogen loss was mainly through the soluble state, while phosphorus migration was dominated by particulate matter. Heavy rainfall in the Xinzheng watershed had a significant impact on the loss of nitrogen and phosphorus. This was related to the properties of purple soil, such as thin soil layer, frequent cultivation and relatively loose soil.

Identification of ceftazidime interaction with bacteria in wastewater treatment by Raman spectroscopic mapping

Raman spectroscopy yields a fingerprint spectrum and is of great importance in medical and biological sciences as it is non-destructive, non-invasive, and available in the aqueous environment. In this study, Raman spectroscopy and Raman mapping were used to explore the dynamic biochemical processes in screened bacteria under ceftazidime stress. The Raman spectral difference between bacteria with and without antibiotic stress was analyzed by principal component analysis and characteristic peaks were obtained. The results showed that amino acids changed first and lipids were reduced when bacteria were exposed to ceftazidime stress. Furthermore, in Raman mapping, when bacteria were subjected to antibiotic stress, the peak at 1002 cm^-1 (phenylalanine) increased, while the peak at 1172 cm^-1 (lipids) weakened. This indicates that when bacteria were stimulated by antibiotics, the intracellular lipids decreased and the content of specific amino acids increased. The reduction of intracellular lipids may suggest a change of membrane permeability. The increase of specific amino acids suggests that bacteria resist external stimuli of antibiotics by regulating the activities of related enzymes. This study explored the processes of the action between bacteria and antibiotics by Raman spectroscopy, and provides a foundation for the further study of the dynamics of microbial biochemical processes in the future.

Toward N2O emission reduction in a single-stage CANON coupled with denitrification: Investigation on nitrite simultaneous production and consumption and nitrogen transformation

A dynamic analysis approach for determining nitrite production and consumption rates was established to systematically investigate the characteristics of nitrogen transformation and N₂O emission of the completely autotrophic nitrogen removal over nitrite (CANON) process coupled with denitrification using a sequencing batch biofilm reactor (SBBR). The results indicate that anaerobic ammonium-oxidizing bacteria was not inhibited significantly by low C/N ratios. There were no obvious differences in the nitrite production rate, nitrite consumption rate or nitrogen removal among reactors operated with C/N ratios of 0, 0.67 and 1.00, which suggested that the certain carbon source did not significantly affect the nitrite conversion and nitrogen removal in the process. More than 60% of total N₂O emission is generated during the initial phase of each period in the SBBR. More than 94.5% of N₂O was generated by NO₂^--N consumption via denitrification in the process. Interestingly, total N₂O production drops by 16.7%, when the C/N ratio increases from 0 to 1. This phenomenon may be caused by the inhibition of N₂O production via AOB denitrification. Therefore, an appropriate carbon source (C/N = 1.00) has the beneficial effect of reducing N₂O emission by CANON coupled with denitrification. The results of this study provide an important empirical foundation for the mitigation of N₂O emission in the CANON process coupled with denitrification.

[Research progress of extracellular vesicles in hepatic fibrosis]

Liver fibrosis is a pathophysiological process characterized by abnormal accumulation of connective tissues in the liver caused by chronic liver injuries, in which the activation and migration of hepatic stellate cells (HSCs) play a central role. Extracellular vesicles (EVs) are a class of nanoscale, bilayer lipid enveloped vesicles secreted by almost all cells. EVs are of great interest in liver pathology because they have been found to mediate the communication between cells and regulate cellular microenvironment via horizontal transfer of their cargoes. EVs carry bioactive cargoes including proteins, lipids and RNA molecules, and are involved in the activation of HSCs during liver fibrogenesis.

Thermodynamics of the interaction between antibiotics and extracellular polymeric substances within activated sludge

The removal of antibiotics in biological wastewater treatment plants (WWTPs) has attracted an ever-increasing interest. Extracellular polymeric substances (EPS) play a crucial role in antibiotics' bio-adsorption using activated sludge, but the interaction mechanism between antibiotics and EPS remains unclear. In this study, the thermodynamics of interactions between EPS and antibiotics (acetaminophen (ACT) and sulfamethazine (SMZ)) were investigated via isothermal titration calorimetry (ITC). The results show that the extracellular proteins strongly combined with ACT and SMZ, and the binding process depended on entropy driven by the hydrophobic interaction as the main driving force. Environmental conditions have a significant impact on the adsorption performance. Therefore, binding of antibiotics and EPS at different pH and ionic strength were investigated to determine the optimal pH and ionic strength. At the near-neutral condition of pH 6.8, the binding reaction of EPS and antibiotics was the most favorable and the conformational change was the maximal. Ionic strength has an obvious effect on the interaction between EPS and antibiotics. The results of this study provided a better understanding of the interaction between antibiotics and EPS in the WWTPs.

[Microbial Community of Granular Sludge in an ANAMMOX-EGSB Reactor Under Saline Conditions]

High-throughput sequencing technology was used to investigate changes in the microbial community in granular sludge under salinity conditions of 0, 15, and 30 g·L^-1 in an ANAMMOX-EGSB reactor under stable operation. The study found that when the influent salinity was increased to 15 g·L^-1 and 30 g·L^-1, the nitrogen removal performance of the reactor decreased slightly, but was restored with the extension of the running time. After the performance of the reactor became stable, the abundance of the ANAMMOX bacteria under the three salinity conditions was 10.33%, 20.90%, and 35.87%, of which Candidatus Kuenenia was the dominant genus. Planctomycetes, Proteobacteria, and Chloroflexi accounted for a high proportion in the granular sludge, and their cumulative abundance exceeded 80%, making them the dominant phyla of the reactor. Under saline conditions, the abundance of the Planctomycetes bacteria increased, the abundance of the Proteobacteria bacteria decreased, and the abundance of the Chloroflexi bacteria was relatively stable. Electron microscopy showed a large number of filamentous bacteria and extracellular polymers were present on the surface of the granular sludge under saline conditions. The increased abundance of the denitrifying bacteria enhanced the cooperative denitrification, the presence of aerobic microorganisms and denitrifying bacteria facilitated the maintenance of anaerobic conditions inside the reactor, and the increased abundance of Chloroflexi and Bacteroidetes was beneficial to maintain the stability of the granular sludge structure. These results showed that the ANAMMOX bacteria could be adapted to saline conditions by acclimation, and that the associated bacteria provided support for the function of the ANAMMOX bacteria under saline conditions.

Organotins in the aquatic media of secondary anabranches in the Three Gorges Reservoir Region, China

The Three Gorges Reservoir Region (TGRR) is one of the most sensitive areas of ecological environment in China. As vital backwater areas, the secondary anabranches of the TGRR were prone to eutrophication in Spring which would affect the distribution and transfer of organotins (OTs) among aquatic media. This study quantified the concentrations of butyltins (BTs) and phenyltins (PhTs) in water columns and aquatic media of two anabranches of the TGRR, the Daning River (DR) and the Xiaojiang River (XR) during the state of eutrophication. Our results showed that the average concentrations of BTs and PhTs in surface water are 43.91, 81.25 ng Sn L^-1 in the DR, and 63.49, 69.21 ng Sn L^-1 in the XR, respectively, and there were no obvious differences in the concentrations of BTs and PhTs across the water columns in the DR and XR. PhTs, especially monophenyltin (MPhT), are predominated in the dissolved phase, whereas BTs, especially dibutyltin (DBT), are predominated in both suspended particulate matter (SPM) and the sediment. Shipping and agricultural activity were likely the sources of OTs in both the DR and XR. High concentrations of tributyltin (TBT) and triphenyltin (TPhT) are still present in the aquatic media of the TGRR, and pose a significant risk to aquatic organisms due to the potential for bioaccumulation. Therefore, it is necessary to further monitor and assess OTs especially PhTs in surface water, and to continue to restrict the use of OTs to protect the aquatic environment of the TGRR.

Effect of high salinity in wastewater on surface properties of anammox granular sludge

Bacterial surface properties fundamentally affect the stability and aggregation of anammox granular sludge. The variation in the surface properties of the granular sludge at different salinities were investigated to further clarify the effect of salinity on the aggregation of anammox granular sludge in this study. High anammox activity was obtained at a salinity of 30 g/L NaCl, and the average removal efficiency of NH₄⁺N, NO₂^--N and TN reached 91.9% ± 1.4%, 97.3% ± 0.4% and 86.3% ± 0.9%, respectively. The sludge particle size in Reactor 1 (with 0 g/L NaCl as control) and Reactor 2 (with 0, 15 and 30 g/L NaCl) increased from 1.62 ± 0.16 mm and 1.59 ± 0.12 mm to 2.71 ± 0.23 mm and 2.44 ± 0.19 mm, respectively, during total operation. PN gradually decreased from 30.58 ± 2.5 mg/g to 18.11 ± 2.1 mg/g, and PS sharply increased from 1.48 ± 0.09 mg/g to 10.52 ± 0.50 mg/g with the increase in salinity. The PS/PN ratio of extracellular polymeric substances (EPS) rapidly increased from 0.05 to 0.58 with an increase of salinity. Fourier transform infra-red spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) results showed that salinity inhibited the expression of anammox sludge hydrophobicity by changing surface groups. Binding between multivalent metal ions and EPS was significantly hindered by the high Na⁺ concentration. The results of this study provided a better understanding of the effect of salinity on the stability and aggregation of anammox granular sludge in saline wastewater treatment.

New insight into sludge reduction induced by different substrate allocation strategy between oxygen and nitrate/nitrite as terminal electron acceptor

Sludge reduction based on regulating substrate allocation between catabolism and anabolism as a strategy is proposed to reduce energy and chemicals consumption during wastewater treatment. The results indicated that a sludge reduction of 14.8% and excellent nutrient removal were simultaneously achieved in the low dissolved oxygen (LDO) activated sludge system with a hydraulic retention time of 24 h at 25 °C. Denitrifiers comprised nearly 1/4 of all microorganisms in the system. These denitrifiers converted NO_x^- to N₂ obtaining a lower biomass yield. The oxidoreductase activity proteins in the LDO sample was more than twice that of the normal DO sample, indicating that catabolism was stimulated by NO_x^- when replacing O₂ as electron acceptor. Less substrate was used for cell synthesis in the LDO system. Stable sludge reduction without extra energy and chemicals inputs was achieved by regulating the substrate allocation by inducing the bacteria to utilize NO_x^- instead of O₂.