Nitrogen Metabolic Pathways Research Articles

Start-up of solid-phase denitrification process for treatment of nitrate-rich water in recirculating mariculture system: Carbon source selection and nitrate removal mechanism

Efficient nitrate removal from recirculating mariculture system (RMS) water is of significance since high concentration of nitrate would cause chronic health effects on aquatic organisms and eutrophication. Solid-phase denitrification (SPD) is a safer and more sustainable approach than conventional heterotrophic denitrification by dosing liquid carbon sources. Thus, its application for treating nitrate-rich RMS water was investigated in this study. Poly 3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV) was identified with the best nitrate removal among four kinds of carbon sources. PHBV-filled reactors started with mariculture, municipal and mixing sludges (at the ratio of 1:1) and fed with 200 mg L-1 nitrate-rich RMS water all achieved over 81% nitrate removals with a HRT of 4 days. The dissolved organic carbon concentrations of the reactors were in the range of 3–9 mg L-1. Arcobacter, Halomonas, and Psedomonas were dominant genera responsible for nitrate removal in different reactors. Metagenomic analyses indicate that both denitrification and assimilatory nitrate reduction (ANR) are the main contributors to nitrate removals. Metagenomic results illustrated nirB/D cooperated with nasA may perform ANR pathway, which transformed nitrate to ammonia for biosynthesis. These results indicate that SPD could be a safer alternative for treating nitrate-rich RMS water, and provide new insights into nitrogen metabolism pathways in SPD process.

Efficient nitrogen removal by a novel extreme strain, Pseudomonas reactans WL20-3 under dual stresses of low temperature and high alkalinity: Characterization, mechanism, and application

Although many studies report the resistance of heterotrophic nitrification-aerobic denitrification (HN-AD) strains to single environmental stress, there is no research on its resistance to dual stresses of low temperature and high alkalinity. A novel bacterium Pseudomonas reactants WL20-3 isolated in this study showed removal efficiencies of 100%, 100%, and 97.76% for ammonium, nitrate, and nitrite, respectively, at 4 °C and pH 11.0. Transcriptome analysis revealed that the resistance of strain WL20-3 to dual stresses was attributed not only to the regulation of genes in the nitrogen metabolic pathway, but also to genes in other pathways such as the ribosome, oxidative phosphorylation, amino acid metabolism, and ABC transporters. Additionally, WL20-3 removed 83.98% of ammonium from actual wastewater at 4 °C and pH 11.0. This study isolated a novel strain WL20-3 with superior nitrogen removal under dual stresses and provided a molecular understanding of its tolerance mechanism to low temperature and high alkalinity.

The response of structure and nitrogen removal function of the biofilm on submerged macrophytes to high ammonium in constructed wetlands

The ammonium exceedance discharge from sewage treatment plants has a great risk to the stable operation of subsequent constructed wetlands (CWs). The effects of high ammonium shocks on submerged macrophytes and epiphytic biofilms on the leaves of submerged macrophytes in CWs were rarely mentioned in previous studies. In this paper, the 16S rRNA sequencing method was used to investigate the variation of the microbial communities in biofilms on the leaves of Vallisneria natans plants while the growth characteristics of V. natans plants were measured at different initial ammonium concentrations. The results demonstrated that the total chlorophyll and soluble sugar synthesis of V. natans plants decreased by 51.45% and 57.16%, respectively, and malondialdehyde content increased threefold after 8 days if the initial NH4+-N concentration was more than 5 mg/L. Algal density, bacterial quantity, dissolved oxygen, and pH increased with high ammonium shocks. The average removal efficiencies of total nitrogen and NH4+-N reached 73.26% and 83.94%, respectively. The heat map and relative abundance analysis represented that the relative abundances of phyla Proteobacteria, Cyanobacteria, and Bacteroidetes increased. The numbers of autotrophic nitrifiers and heterotrophic nitrification aerobic denitrification (HNAD) bacteria expanded in biofilms. In particular, HNAD bacteria of Flavobacterium, Hydrogenophaga, Acidovorax, Acinetobacter, Pseudomonas, Aeromonas, and Azospira had higher abundances than autotrophic nitrifiers because there were organic matters secreted from declining leaves of V. natans plants. The analysis of the nitrogen metabolic pathway showed aerobic denitrification was the main nitrogen removal pathway. Thus, the nitrification and denitrification bacterial communities increased in epiphytic biofilms on submerged macrophytes in constructed wetlands while submerged macrophytes declined under ammonium shock loading.

Differences of Nitrogen Transformation Pathways and Their Functional Microorganisms in Water and Sediment of a Seasonally Frozen Lake, China

Nitrogen is one of the most important elements involved in ecosystem biogeochemical cycling. However, little is known about the characteristics of nitrogen cycling during the ice-covered period in seasonally frozen lakes. In this study, shotgun metagenomic sequencing of subglacial water and sediment from Lake Ulansuhai was performed to identify and compare nitrogen metabolism pathways and microbes involved in these pathways. In total, ammonia assimilation was the most prominent nitrogen transformation pathway, and Bacteria and Proteobacteria (at the domain and phylum levels, respectively) were the most abundant portion of microorganisms involved in nitrogen metabolism. Gene sequences devoted to nitrogen fixation, nitrification, denitrification, dissimilatory nitrate reduction to ammonium, and ammonia assimilation were significantly higher in sediment than in surface and subsurface water. In addition, 15 biomarkers of nitrogen-converting microorganisms, such as Ciliophora and Synergistetes, showed significant variation between sampling levels. The findings of the present study improve our understanding of the nitrogen cycle in seasonally frozen lakes.

Simultaneous removal of antibiotics and nitrogen by microbial fuel cell-constructed wetlands: Microbial response and carbon–nitrogen metabolism pathways

Microbial fuel cell-constructed wetlands (MFC-CWs) are attracted extensive attention due to their simultaneous removal performance during the co-occurrence of various pollutants in wastewater. This study explored the performance and mechanisms on the simultaneous removal of antibiotics and nitrogen from MFC-CWs which packed with coke (MFC-CW (C)) and quartz sand (MFC-CW (Q)) substrate. Results showed that removal of sulfamethoxazole (93.60 %), COD (77.94 %), NH4+-N (79.89 %), NO3−- N (82.67 %), and TN (70.29 %) significantly enhanced by MFC-CW (C) due to the enhancement of relative abundance of membrane transport, amino acid metabolism and carbohydrate metabolism pathways. The results indicated that coke substrate can generate more electric energy in MFC-CW. Firmicutes (18.56–30.82 %), Proteobacteria (23.33–45.76 %), and Bacteroidetes (17.1–27.85 %) were dominant phyla in the MFC-CWs. MFC-CW (C) posed significant effects on the microbial diversity and structure, which motivated the functional microbes involved in the transformation of antibiotics and nitrogen and bioelectricity generation. Given the overall performance of MFC-CW, packing with cost-effective substrate to electrode region of MFC-CWs was found to be an effective strategy for simultaneously removing antibiotics and nitrogen in the wastewater treatment.

#4941 A METABOLOMIC FINGERPRINT PERSPECTIVE OF GUT-DERIVED METABOLITES ON EARLY DIABETIC KIDNEY DISEASE IN TYPE 2 DIABETES MELLITUS PATIENTS

Abstract Background and Aims Type 2 diabetes mellitus (T2DM) is the first cause of end stage renal disease worldwide. Metabolite profiling is an emerging field of great significance, as T2DM prevalence is continuously rising. The subtle dynamics of gut microbiota derived metabolites may have important implications in diabetic kidney disease (DKD) development. Nitrogen metabolic pathway and retinoic acid signaling pathway seem to be involved in early pathogenic mechanisms of DKD. The aim of study was to discover new putative gut-derived biomarkers that interfere with early physio-pathological mechanisms in DKD, regarding the podocyte, tubule, and the renal endothelium. Method The serum and urine of 90 T2DM patients (P group) and 20 healthy subjects (C group), were assessed in a cross-sectional study, by ultra-high-performance liquid chromatography coupled with electrospray ionization-quadrupole-time of flight-mass spectrometry (UHPLC-QTOF-ESI+-MS) techniques. P group was divided in 3 subgroups (normoalbuminuria-P1, microalbuminuria-P2, macroalbuminuria-P3). Statistical analysis was performed by untargeted multivariate (PLSDA, VIP scores, Random Forest, Biomarker analysis) and univariate (One Way ANOVA, Biomarker Analysis) methods. Results Multivariate analysis, by which the P group vs. C group were compared, displayed: (1) in serum samples: increased levels (P>C) of all-trans retinoic acid, cysteine-S sulfate, oleoylglicine, threonylglycine and decreased levels (P<C) of phenylalanine, tyrosine, kynurenic acid; (2) in urine samples, there were increased levels of: all-trans retinoic acid, indoxyl suflate, serotonin sulfate and glycylprolylarginine. Subsequently, by applying univariate analysis, the biomarkers derived from gut microbiota were selected: (1) in serum: all-trans retinoic acid (C<P1<P2<3), phenylalanine, tyrosine, and kynurenic acid with levels decreasing progressively from C to P1-P2-P3 (2) in urine: all trans retinoic acid, indoxyl sulfate, and serotonin sulfate, showing good differentiation between C and P1, and slight differences between P1∼P2∼P3 subgroups. The study suggests that ATRAs dynamic is disturbed in the normoalbuminuric stage of DKD. While its urinary levels correlated significantly with albuminuria, the changes observed in P1 subgroup, in serum and urine, may be correlated to the loss of renal tubular tight junction as a result of claudin downregulation. Phenylalanine and tyrosine, a part of nitrogen metabolic pathway, are indicators of the new-onset DKD. Their levels were upregulated in serum vs. urine, indicating their possible involvement in early DKD when comparing C vs. P1-P2-P3. Kynurenic acid and indoxyl-sulfate result from tryptophan metabolism. Low levels in serum of kynurenic acid may suggest its possible implication in incipient endothelial dysfunction in DKD. Indoxyl-sulfate (IS) urinary excretion is dependent on albuminuria. The study shows an elevated excretion of IS, in the normoalbuminuric group compared to controls and may suggest a tubular damage that precedes the glomerular modifications in DKD. Conclusion UHPLC-QTOF-ESI+-MS untargeted analysis reveals a particular metabolite fingerprint in early DKD. The study describes all-trans retinoic acid, phenylalanine, tyrosine, kynurenic acid, and indoxyl sulfate, as potential key biomarkers involved in early DKD pathogenesis, their levels being expressed in P1 subgroup compared with C group, and P2, P3 subgroups.

Blocking the Expression of the Nitrate Reductase Gene OsNia3 Confers Early Maturation in Rice

Early flowering is a major contributing factor to early crop maturation and is a prerequisite for the expansion of crop production to high latitudes with short growing seasons as well as for annual double/triple cropping systems. Nitrogen is the mineral element most limiting to plant growth and, consequently, also to crop yield. Nitrogen also plays a role in the regulation of flowering time. Here, we show that OsNia3 is a member of the rice nitrate reductase (NR) gene family. OsNia3 was found to be expressed in stem nodes of rice, while the loss of its function led to a reduction in plant height mainly due to disrupted nitrate metabolism at the site of OsNia3 expression. The expression levels of genes related to nitrate transport, nitrate assimilation, and ammonium assimilation, such as OsNia1, OsNRT2.3A, and OsNGS1, increased in the leaves of osnia3 mutant plants, concomitant with an increase in the activity of the nitrogen metabolism pathway. The ammonium and amino acid contents in the leaves also increased in the osnia3 mutant, as did the chlorophyll content. Phenotypic analysis showed that the osnia3 mutant exhibited a shorter growth period compared with wild-type plants; nevertheless, yield was not significantly affected in mutant plants. The deletion of the OsNia3 gene led to the upregulation of genes related to the photoperiod regulation network (OsGI, OsHd1, and OsHd3a), which likely promoted early flowering. These results indicated that OsNia3 is involved in the floral inhibition pathway (OsGI-OsHd1-OsHd3a) in rice under long-day conditions. Our findings provide a theoretical and material basis for the coordination and improvement of early maturity and high-yield traits in rice breeding.

Enhanced nitrogen removal and antibiotic resistance genes control through electrocatalytic reduction and the underlying mechanisms

The control of antibiotic resistance genes (ARGs) and removal of nitrogen are the main challenges in antibiotic wastewater treatment. This study adopted the multielectrode microbial fuel cell (MFC) to promote autotrophic denitrification and adopted agricultural waste as a slow-release carbon source to enhance heterotrophic denitrification while running in a siphoning mode. The associated metabolic process and mechanism were explored. The results showed that the electrochemical catalysis and siphoning aeration significantly improved the removal of COD and antibiotics. The number of ARGs and MGEs decreased significantly when both the electrochemical process and the siphoning mode were used. The removal of NH4+-N was limited under open-circuit conditions, and the removal was lower than 35.4% in all the reactors. Under electrochemical conditions, the addition of slow-release carbon sources promoted heterotrophic denitrification, and the removal of TN increased by 42.9%. The microbial mechanism of nitrogen removal and ARG control under the electrochemical process were revealed by metagenomic analysis. Compared with the control group, there were a large number of functional genes related to iron REDOX (oorB, oorD, moxR, moxA, mnxG, and mcoA) in the system, which promoted the efficiency of nitrogen removal through coupling with genes related to the nitrogen metabolic pathway. The results can provide a reference for ARGs control and nitrogen removal in the treatment of antibiotic wastewater containing high nitrogen concentrations.

Transcriptome analysis of the uterovaginal junction containing sperm storage tubules in heat-stressed breeder hens

Sperm storage tubules (SSTs) in the uterovaginal junction (UVJ) of the oviduct are major sites of sperm storage after artificial insemination or mating. Female birds may regulate sperm motility in the UVJ. Heat stress can decrease the reproductive ability of broiler breeder hens. However, its effects on UVJ remain unclear. Changes in gene expression aid in understanding heat stress-affected molecular mechanisms. Herein, we wanted to conduct a comparative transcriptomic analysis to identify the differentially expressed genes (DEGs) in the UVJ of breeder hens under thermoneutral (23°C) and heat stress (36°C for 6 h) conditions. The results indicated that cloacal temperatures and respiratory rates were significantly increased in heat-stressed breeder hens (P < 0.05). Total RNA was extracted from the hen UVJ tissues containing SSTs after heat exposure. Transcriptome analysis identified 561 DEGs, including 181 upregulated DEGs containing heat shock protein (HSP) transcripts and 380 downregulated DEGs containing immune-related genes, such as interleukin 4-induced 1, radical S-adenosyl methionine domain containing 2, and 2'-5'-oligoadenylate synthetase like, in heat-stressed hens. Gene Ontology analysis revealed the significantly enriched terms involving HSPs. Kyoto Encyclopedia of Genes and Genomes analysis identified 9 significant pathways, including the protein processing in endoplasmic reticulum (11 genes including HSPs), neuroactive ligand-receptor interaction (13 genes including luteinizing hormone/choriogonadotropin receptor), biosynthesis of amino acids (4 genes including tyrosine aminotransferase), ferroptosis (3 genes including heme oxygenase 1), and nitrogen metabolism (carbonic anhydrase [CA]-12 and CA6) pathways. Protein-protein interaction network analysis of DEGs revealed 2 large networks, one containing upregulated HSPs and the other containing downregulated interferon-stimulating genes. Overall, heat stress inhibits innate immunity in the UVJ tissues of broiler chickens, and heat-stressed chickens protect their cells by increasing the expression levels of HSPs. The identified genes are potential candidates for further exploration of the UVJ in heat-stressed hens. The identified molecular pathways and networks increase our understanding of the sperm storage reservoirs (UVJ containing SSTs) within the reproductive tract and may be used to prevent heat stress-induced fertility loss in breeder hens.

Up-flow dual-loop anammox system treating mature landfill leachate: ultra-efficient nitrogen removal, anammox granules formation, and functional divergence

Achieving the effective retention and rapid enrichment of anammox bacteria (AnAOB) remains a challenge in landfill leachate treatment systems. The application of the anammox process is also restricted by an inadequate supply of nitrite and poor resistance to adverse environments. To overcome these obstacles, an up-flow dual-loop anammox (UDLA) system treating mature landfill leachate was established, based on partial nitrification, anammox, and partial denitrification (PNAPD) technology. The nitrogen removal efficiency and nitrogen loading rate reached 92.9 ± 1.5% and 0.4 kg N/m3/d, and isotope tracing tests demonstrated that 88.2 ± 6.5%-93.9 ± 3.9% of the nitrogen loss contributed by anammox pathway. Under the up-flow dual-loop strategy, anammox granules were successfully cultivated when flux ratios of effluent/influent and produced gas/influent were maintained at 1640.0%, and 250.0%, respectively. The proportion of medium granules (500–1000 μm) with the highest PNAPD activity increased from 0 to 24.9%, whereas the percentage of floc (0–200 μm) reduced from 98.4% to 23.3%. The mechanism of anammox granules formation in the UDLA system was revealed by multidimensional analysis. Candidatus_Brocadia_sapporoensis (13.3%-13.5%), Candidatus_Kuenenia_stuttgartiensis (2.0%-4.8%), and Candidatus_Brocadia_sp. (0.9%-1.1%) were the predominant anammox species, enriched in medium and macro granules. Metagenomic sequencing confirmed the functional divergence of nitrogen and carbon metabolism among the size-fractioned granules, possible functions of specific species, and gene distribution in the nitrogen metabolism pathway. The abundant GlnA, GltB(D), GdhA, GudB (GDH2), and GLUD1_2 genes might promote the synthesis of adhesive proteins and further facilitate microbial aggregation. This study enhanced the comprehension of anammox granules formation and showed important implications for leachate treatment in engineering.

A novel filter-type constructed wetland for secondary effluent treatment: Performance and its microbial mechanism

A novel filter-type constructed wetland was constructed by combining plastic fillers and mineral fillers for secondary effluent treatment. Findings showed that TN, TP and COD removal in the constructed wetland with composite fillers (CFCW) was 3.9%, 8.0% and 3.5% higher than that of constructed wetland with ordinary gravel fillers (CW) in the stable phase, respectively. CFCW showed better pollutants removal when dealing with higher influent concentrations and hydraulic loading. The main functional bacteria in two systems were significantly different (p < 0.05). Composite fillers could change the dominant genera, enhance genera activity and increase genera quantity. Denitrification (e.g., Pseudorhodobacter, Zoogloea, Pseudarthrobacter), nitrification (e.g., Devosia, Nitrospira), heterotrophic nitrification-aerobic denitrification (e.g., Paracoccus) and partial denitrification (e.g., g__Simplicispira) in CFCW provided diverse nitrogen metabolism pathways, resulting in higher nitrogen removal. The novel filter-type constructed wetland is suitable for the advanced treatment of sewage treatment plant effluent with enhanced pollutants removal and exuberant microorganisms.

Complete nitrogen removal from low-strength wastewater via double nitrite shunt coupling anammox and endogenous nitrate respiration: Functional metabolism and electron transport

Autotrophic nitrogen removal processes based on anammox are facing huge challenges of high effluent quality in wastewater treatment. In this study, a novel hybrid system of anammox coupled with heterotrophic endogenous metabolisms was developed in a single-stage bioreactor to treat real domestic wastewater. Complete nitrogen removal was achieved at a low carbon to nitrogen (C/N) ratio of 2.8 and more than 95.2% nitrogen removal was maintained under an extremely low C/N ratio of 1.9. The nitrite shunt supplied by dual partial pathways (partial nitritation and endogenous partial denitratation) guaranteed the anammox activity with a high contribution to nitrogen removal above 60%. While endogenous denitrification (ED) and denitrifying phosphorus removal (DPR) both participated in nitrate respiration, contributing more than 28% and 9% to nitrogen removal, respectively. The coexistence and enrichment of anammox bacteria (Ca. Brocadia, 0.9%), glycogen accumulating organisms (Ca. Competibacter, 6.4%) and phosphorus accumulating organisms (Dechloromonas, 3.9% and Ca. Accumulibacter, 0.7%) contributed to the co-metabolism of carbon, nitrogen and phosphorus. The functional genes encoding the above metabolism were highly correlated with the dominant strains, indicating that the multiple pathways of carbon and nitrogen metabolism supported the continuous supply of electrons required for nitrogen removal. This study puts forward a novel complete nitrogen removal process by successfully coupling autotrophic and endogenous heterotrophic metabolism.

Thiomicrorhabdus marina sp.nov., an obligate chemolithoautotroph isolated from tidal zone sediment, and genome insight into the genus Thiomicrorhabdus

The contribution of microbes to the marine sulfur cycle has received considerable attention in recent years. In this study, a new Gram-stain-negative, aerobic sulfur-oxidizing bacterium, designated strain 6S2-11T, was isolated from tidal zone sediment of the coast of Weihai, China. Strain 6S2-11T was an obligate chemolithoautotroph utilizing thiosulfate as the energy source. Physiological and biochemical experiments, phylogenetic analysis, and comparative genomic analysis were done with strain 6S2-11T. According to genomic analysis, strain 6S2-11T owned a complete thiosulfate oxidation pathway and an untypical nitrogen metabolism pathway. Its relatively small genome also has multiple environmental adaptation mechanisms. The DNA G+C content of strain 6S2-11T was 44.1%. Strain 6S2-11T was observed to grow at 20-37°C (optimum, 35°C), pH 6.0-9.5 (optimum, pH 7.5), and 0.5-5% (w/v) NaCl (optimum, 2.5%). The major cellular fatty acids (&amp;gt;10%) of strain 6S2-11T were Summed Feature 8 (C18:1ω7c/C18:1ω6c), C16:0 and Summed Feature 3 (C16:1ω7c/C16:1ω6c). The comparison of 16S rRNA gene sequences indicated that strain 6S2-11T was most closely to Thiomicrorhabdus xiamenensis G2T (96.8%). Based on the results of phylogenetic analysis, the strain 6S2-11T is a novel specie of the genus Thiomicrorhabdus, for which name Thiomicrorhabdus marina sp.nov. is proposed with the type strain 6S2-11T (=MCCC 1H00523T=KCTC 82994T).

Inhibition of invasive plant Mikania micrantha rapid growth by host-specific rust (Puccinia spegazzinii).

Mikania micrantha Kunth is a fast-growing global invasive weed species that causes severe damage to natural ecosystems and very large economic losses of forest and crop production. Although Puccinia spegazzinii can effectively inhibit the growth of M. micrantha and is used as a biological control strain in many countries, the mechanism of inhibiting the growth in Mikania micrantha is not clear. Here, we used a combination of phenotypic, enzyme activity, transcriptomic and metabolomic approaches to study the response of M. micrantha after infection by P. spegazzinii. In the early stages of rust infection, JA, JA-Ile and SA levels in infected leaves were significantly lower than that in uninfected leaves. In teliospore initial and developed stages of P. spegazzinii, JA and JA-Ile levels substantially increased by more than 6 times, which resulted in a significant decrease in accumulation of defense hormone SA in infected leaves of M. micrantha. The contents of plant growth-promoting hormones were significantly reduced in the infected plants as a result of substantial downregulation of expression of key genes related to hormone biosynthesis. Furthermore, rust infection led to high levels of ROS in chloroplasts and the destruction of chlorophyll structure, which also led to decreased photosynthetic gene expression, net photosynthetic rate, activity of Rubisco and levels of important organic acids in the Calvin cycle. We hypothesised that after P. spegazzinii infection, JA or JA-Ile accumulation not only inhibited SA levels to promote rust infection and development, but also impeded the rapid growth of M. micrantha by affecting plant growth hormones, carbon, and nitrogen metabolic pathways.

Bifidobacterium longum subsp. infantis utilizes human milk urea to recycle nitrogen within the infant gut microbiome

ABSTRACT Human milk guides the structure and function of microbial commensal communities that colonize the nursing infant gut. Indigestible molecules dissolved in human milk establish a microbiome often dominated by bifidobacteria capable of utilizing these substrates. Interestingly, urea accounts for ~15% of total human milk nitrogen, representing a potential reservoir for microbiota that may be salvaged for critical metabolic operations during lactation and neonatal development. Accordingly, B. infantis strains are competent for urea nitrogen utilization, constituting a previously hypothetical phenotype in commensal bacteria hosted by humans. Urease gene expression, downstream nitrogen metabolic pathways, and enzymatic activity are induced during urea utilization to yield elevated ammonia concentrations. Moreover, biosynthetic networks relevant to infant nutrition and development are transcriptionally responsive to urea utilization including branched chain and other essential amino acids. Importantly, isotopically labeled urea nitrogen is broadly distributed throughout the expressed B. infantis proteome. This incisively demonstrates that the previously inaccessible urea nitrogen is incorporated into microbial products available for infant host utilization. In aggregate, B. infantis possesses the requisite phenotypic foundation to participate in human milk urea nitrogen recycling within its infant host and thus may be a key contributor to nitrogen homeostasis early in life.

Metabolite Profiling of the Gut–Renal–Cerebral Axis Reveals a Particular Pattern in Early Diabetic Kidney Disease in T2DM Patients

Type 2 diabetes mellitus (T2DM) represents an important microvascular disease concerning the kidney and the brain. Gut dysbiosis and microbiota-derived metabolites may be in relation with early pathophysiological changes in diabetic kidney disease (DKD). The aim of the study was to find new potential gut-derived biomarkers involved in the pathogenesis of early DKD, with a focus on the complex interconnection of these biomarkers with podocyte injury, proximal tubule dysfunction, renal and cerebrovascular endothelial dysfunction. The study design consisted of metabolite profiling of serum and urine of 90 T2DM patients (subgroups P1-normoalbuminuria, P2-microalbuminuria, P3-macroalbuminuria) and 20 healthy controls (group C), based on ultra-high-performance liquid chromatography coupled with electrospray ionization-quadrupole-time of flight-mass spectrometry analysis (UHPLC-QTOF-ESI+-MS). By multivariate and univariate analyses of serum and urine, which included Partial Least Squares Discriminant Analysis (PLSDA), Variable Importance Plots (VIP), Random Forest scores, One Way ANOVA and Biomarker analysis, there were discovered metabolites belonging to nitrogen metabolic pathway and retinoic acid signaling pathway which differentiate P1 group from P2, P3, C groups. Tyrosine, phenylalanine, indoxyl sulfate, serotonin sulfate, and all-trans retinoic acid express the metabolic fingerprint of P1 group vs. P2, P3, C groups, revealing a particular pattern in early DKD in T2DM patients.

Tritium and Carbon-14 Contamination Reshaping the Microbial Community Structure, Metabolic Network, and Element Cycle in the Seawater Environment.

The potential ecological risks caused by entering radioactive wastewater containing tritium and carbon-14 into the sea require careful evaluation. This study simulated seawater's tritium and carbon-14 pollution and analyzed the effects on the seawater and sediment microenvironments. Tritium and carbon-14 pollution primarily altered nitrogen and phosphorus metabolism in the seawater environment. Analysis by 16S rRNA sequencing showed changes in the relative abundance of microorganisms involved in carbon, nitrogen, and phosphorus metabolism and organic matter degradation in response to tritium and carbon-14 exposure. Metabonomics and metagenomic analysis showed that tritium and carbon-14 exposure interfered with gene expression involving nucleotide and amino acid metabolites, in agreement with the results seen for microbial community structure. Tritium and carbon-14 exposure also modulated the abundance of functional genes involved in carbohydrate, phosphorus, sulfur, and nitrogen metabolic pathways in sediments. Tritium and carbon-14 pollution in seawater adversely affected microbial diversity, metabolic processes, and the abundance of nutrient-cycling genes. These results provide valuable information for further evaluating the risks of tritium and carbon-14 in marine environments.

Effect of Temperature on Microorganisms and Nitrogen Removal in a Multi-Stage Surface Flow Constructed Wetland

The effect of low temperature on microbial nitrogen metabolism in constructed wetlands has yet to be extensively investigated. In this study, we analyzed the effects of temperature changes on nitrogen-associated microorganisms and nitrogen metabolism functional genes in a multi-stage surface flow constructed wetland (MSSFCW) using metagenomic sequencing. The treatment of polluted river water in the MSSFCW, which had a mean water temperature (MWT) of ≤17 °C, resulted in a low removal efficiency (RE) for total nitrogen (TN; average RE: 23.05% at 1–17 °C) and nitrate nitrogen (NO3−-N; average RE: −2.41% at 1–17 °C). Furthermore, at a MWT of ≤11 °C, the REs were low for ammonium nitrogen (NH4+-N; average RE: 67.92% at 1–11 °C) and for chemical oxygen demand (COD; average RE: 27.45% at 1–11 °C). At 0.24 m3 m−2 d−1 influent load, the highest REs for TN (66.84%), NO3−-N (74.90%), NH4+-N (83.93%), and COD (52.97%) occurred in July and August, when water temperatures were between 26 and 28 °C. The lowest rates (TN: 11.90%, NO3−-N: −21.98%, NH4+-N: 65.47%, COD: 24.14%) occurred in the January–February period, when the water temperature was lowest (1–5 °C). A total of 25 significantly different species were detected in surface sediment, none of which were dominant species. The dominant phyla and genera at low (January) and high (July) temperatures were similar; however, microorganisms were more abundant in the low-temperature months. Our analysis indicated that the same nitrogen metabolism pathways occurred in January and July. Denitrification-associated functional genes were the most abundant; nitrification-related functional genes were the least abundant. Only nirBD displayed significantly different abundances between January and July. This paper can hopefully help researchers and managers further understand how temperature affects nitrogen removal performance in constructed wetlands.

Effect of Frozen-Thawed Embryo Transfer on the Metabolism of Children in Early Childhood.

As a routine procedure in assisted reproductive technology (ART), it is crucial to assess the safety of frozen and thawed embryo transfer (FET). We aimed to investigate the metabolic profile of children conceived through FET in their early childhood. A total of 147 children between the age of 1.5 and 4 years old, conceived through FET or naturally conceived (NC), were recruited. A total of 89 children, 65 in the FET group and 24 in the NC group (matched with the FET group based on children's BMI) were included in the final statistical analysis of biochemical markers and metabolomics. Children conceived through FET had a lower level of fasting insulin level and HORM-IR and a higher level of fasting glucose and APOE as compared to children naturally conceived. Metabolomics showed that there were 16 small differential metabolites, mainly including amino acids, carnitines, organic acids, butyric, and secondary bile acid between two groups, which enriched in Nitrogen metabolism, Butanoate metabolism, Phenylalanine metabolism, and D-Arginine and D-ornithine metabolism pathways. Although the FET group had a significantly higher level of APOE and fasting glucose, it cannot yet be considered that children in the FET group had an obvious disorder of glucose and lipid metabolism. However, the potentially more active intestinal flora and lower carnitine levels of children in the FET group suggested by metabolomics are worth further exploration.

Microbial ecological responses of partial nitritation/anammox granular sludge to real water matrices and its potential application

Granular sludges are commonly microbial aggregates used to apply partial nitritation/anammox (PN/A) processes during efficient biological nitrogen removal from ammonium-rich wastewater. Considering keystone taxa of anammox bacteria (AnAOB) in granules and their sensitivity to unfavorable environments, it is essential to investigate microbial responses of autotrophic PN/A granules to real water matrices containing organic and inorganic pollutants. In this study, tap water, surface water, and biotreated wastewater effluents were fed into a series of continuous PN/A granular reactors, respectively, and the differentiation in functional activity, sludge morphology, microbial community structure, and nitrogen metabolic pathways was analyzed by integrating kinetic batch testing, size characterization, and metagenomic sequencing. The results showed that feeding of biotreated wastewater effluents causes significant decreases in nitrogen removal activity and washout of AnAOB (dominated by Candidatus Kuenenia) from autotrophic PN/A granules due to the accumulation of heavy metals and formation of cavities. Microbial co-occurrence networks and nitrogen cycle-related genes provided evidence for the high dependence of symbiotic heterotrophs (such as Proteobacteria, Chloroflexi, and Bacteroidetes) on anammox metabolism. The enhancement of Nitrosomonas nitritation in the granules would be considered as an important contributor to greenhouse gas (N2O) emissions from real water matrices. In a novel view on the application of microbial responses, we suggest a bioassay of PN/A granules by size characterization of red-color cores in ecological risk assessment of water environments.