Optimization of operating parameters and microbiological mechanism of a low C/N wastewater treatment system dominated by iron-dependent autotrophic denitrification.

Ferrous iron (Fe2+) reduces the amount of external carbon source used for the denitrification of low-C/N wastewater. The effects of key operating parameters on the efficiency of ferrous-dependent autotrophic denitrification (FDAD) and the functioning mechanism of the microbiome can provide a regulatory strategy for improving the denitrification efficiency of low C/N wastewater. In this study, the response surface method (RSM) was used to explore the influence of four important parameters-the molar ratio of Fe2+ to NO3--N (Fe/N), total organic carbon (TOC), the molar ratio of inorganic carbon to NO3--N (IC/N) and sludge volume (SV, %)-on the FDAD efficiency. Functional prediction and molecular ecological networks based on high-throughputs sequencing techniques were used to explore changes in the structure, function, and biomarkers of the sludge microbial community. The results showed that Fe/N and TOC were the main parameters affecting FDAD efficiency. Higher concentrations of TOC and high Fe/N ratios provided more electron donors and improved denitrification efficiency, but weakened the importance of biomarkers (Rhodanobacter, Thermomonas, Comamonas, Thauera, Geothrix and unclassified genus of family Gallionellaceae) in the sludge ecological network. When Fe/N > 4, the denitrification efficiency fluctuated significantly. Functional prediction results indicated that genes that dominated N2O and NO reduction and the genes that dominated Fe2+ transport showed a slight decrease in abundance at high Fe/N levels. In light of these findings, we recommend the following optimization ranges of parameters: Fe/N (3.5-4); TOC/N (0.36-0.42); IC/N (3.5-4); and SV (approximately 35%).

Development of tenofovir monobenzyl ester phosphonoamidate prodrugs with improved anti-hepatitis B virus activity and intrahepatic tenofovir enrichment.

Various tenofovir (TFV) prodrugs have been developed by introducing masking groups to the hydroxyls of the monophosphonate group to enhance intestinal absorption efficiency and therapeutic effects. However, the reported TFV prodrugs have drawbacks such as low bioavailability, systemic toxicity caused by their breakdown in non-targeted tissues, and potential low intracellular conversion efficiency. In the present study, we developed a class of TFV monobenzyl ester phosphonoamidate prodrugs without substitutions on the benzene ring. Compared with previous TFV prodrugs, compounds 3a and 3b developed in the present study showed higher anti-hepatitis B virus activity, stronger stability and higher levels of intrahepatic enrichment of the metabolic product (TFV), indicating the potential of these compounds as novel prodrugs with high efficiency and low systemic toxicity for the treatment of hepatitis B.

Distinctive species interaction patterns under high nitrite stress shape inefficient denitrifying phosphorus removal performance.

Denitrifying phosphorus removal using nitrite as an electron acceptor is an innovative, resource-efficient approach for nitrogen and phosphorus removal. However, the inhibitory effects of nitrite on anoxic phosphorus uptake and process stability are unclear. This study investigated the total phosphorus removal performance under nitrite stress and analyzed microbiome responses in 186 sludge samples. The results indicated that the total phosphorus removal rates and dominant taxon abundance were highly similar under nitrite stress. High nitrite stress induced a community-state shift, leading to unstable dynamics and decreased total phosphorus removal. This shift resulted from increased species cooperation. Notably, the shared genera OLB8 and Zoogloea under non-inhibitory nitrite stress, suggesting their vital roles in mitigating nitrite stress by enhancing carbon and energy metabolism. The response patterns of these bacterial communities to high nitrite stress can guide the design and optimization of high-nitrogen wastewater reactors.

Environmental stressors altered the groundwater microbiome and nitrogen cycling: A focus on influencing mechanisms and pathways.

Nitrogen cycling, as an important biogeochemical process in groundwater, strongly impacts the energy and matter flow of groundwater ecology. Phthalate esters (PAEs) were screened as key environmental stressors in the groundwater of Beijing, contributing to the alteration of microbial community structure and functions; thus, it could be deduced that these stressors might influence nitrogen cycling that is almost exclusively mediated by microorganisms. Identification of the influences of PAEs on groundwater nitrogen cycling and exploration of the potential influence mechanisms and pathways are vital but still challenging. This study explored the influence mechanisms and pathways of the environmental stressor PAE on nitrogen cycling in groundwater collected from a typical monitoring station in Beijing based on high-throughput sequencing and bioinformatics analysis combined with mediation analysis methods. The results suggested that among the 5 detected PAEs, dimethyl phthalate and diethyl phthalate significantly negatively impacted nitrogen cycling processes, especially nitrogen fixation and denitrification processes (p < 0.05), in groundwater. Their influences were fully or partially mediated by functional microorganisms, particularly assigned keystone genera (such as Dechloromonas, Aeromonas and Noviherbaspirillum), whose abundance was significantly inhibited by these PAEs via dysregulation of carbohydrate metabolism and activation of defense mechanisms. These findings confirmed that the influences of environmental stressors PAEs on nitrogen cycling in groundwater might be mediated by the "PAE stress-groundwater microbiome-nitrogen cycling alteration" pathway. This study may advance the understanding of the consequences of environmental stressors on groundwater ecology and support the ecological hazard assessment of groundwater stressors.

Response of the soil microbial community to petroleum hydrocarbon stress shows a threshold effect: research on aged realistic contaminated fields.

Introduction: Microbes play key roles in maintaining soil ecological functions. Petroleum hydrocarbon contamination is expected to affect microbial ecological characteristics and the ecological services they provide. In this study, the multifunctionalities of contaminated and uncontaminated soils in an aged petroleum hydrocarbon-contaminated field and their correlation with soil microbial characteristics were analyzed to explore the effect of petroleum hydrocarbons on soil microbes. Methods: Soil physicochemical parameters were determined to calculate soil multifunctionalities. In addition, 16S high-throughput sequencing technology and bioinformation analysis were used to explore microbial characteristics. Results: The results indicated that high concentrations of petroleum hydrocarbons (565-3,613 mg•kg-1, high contamination) reduced soil multifunctionality, while low concentrations of petroleum hydrocarbons (13-408 mg•kg-1, light contamination) might increase soil multifunctionality. In addition, light petroleum hydrocarbon contamination increased the richness and evenness of microbial community (p < 0.01), enhanced the microbial interactions and widened the niche breadth of keystone genus, while high petroleum hydrocarbon contamination reduced the richness of the microbial community (p < 0.05), simplified the microbial co-occurrence network, and increased the niche overlap of keystone genus. Conclusion: Our study demonstrates that light petroleum hydrocarbon contamination has a certain improvement effect on soil multifunctionalities and microbial characteristics. While high contamination shows an inhibitory effect on soil multifunctionalities and microbial characteristics, which has significance for the protection and management of petroleum hydrocarbon-contaminated soil.

Nitrite-resistance mechanisms on wastewater treatment in denitrifying phosphorus removal process revealed by machine learning, co-occurrence, and metagenomics analysis.

Nitrite is a key intermediate in nitrogen metabolism that determines microbial transformations of N and P, greenhouse gas (N2O) emissions, and system nutrient removal efficiency. However, nitrite also exerts toxic effects on microorganisms. A lack of understanding of high nitrite-resistance mechanisms at community- and genome-scale resolutions hinders the optimization for robustness of wastewater treatment systems. Here, we established nitrite-dependent denitrifying and phosphorus removal (DPR) systems under a gradient concentration of nitrite (0, 5, 10, 15, 20, and 25 mg N/L), relying on 16S rRNA gene amplicon and metagenomics to explore high nitrite-resistance mechanism. The results demonstrated that specific taxa were adopted to change the metabolic relationship of the community through phenotypic evolution to resist toxic nitrite contributing to the enhancement of denitrification and inhibition of nitrification and phosphorus removal. The key specific species, Thauera enhanced denitrification, whereas Candidatus Nitrotoga decreased in abundance to maintain partial nitrification. The extinction of Candidatus Nitrotoga induced a simpler restructuring-community, forcing high nitrite-stimulating microbiome to establish a more focused denitrification rather than nitrification or P metabolism in response to nitrite toxicity. Our work provides insights for understanding microbiome adaptation to toxic nitrite and giving theoretical support for operation strategy of nitrite-based wastewater treatment technology.

Anthropogenic land-use activities within watersheds reduce comammox activity and diversity in rivers.

Nitrogen cycling plays a key role in maintaining river ecological functions which are threatened by anthropogenic activities. The newly discovered complete ammonia oxidation, comammox, provides novel insights into the ecological effects of nitrogen on that it oxidizes ammonia directly to nitrate without releasing nitrite as canonical ammonia oxidization conducted by AOA or AOB which is believed to play an important role in greenhouse gas generation. Theoretically, contribution of commamox, AOA and AOB to ammonia oxidization in rivers might be impacted by anthropogenic land-use activities through alterations in flow regime and nutrient input. While how land use pattern affects comammox and other canonical ammonia oxidizers remains elusive. In this study, we examined the ecological effects of land use practices on the activity and contribution of three distinctive groups of ammonia oxidizers (AOA, AOB, comammox) as well as the composition of comammox bacterial communities from 15 subbasins covering an area of 6166 km2 in North China. The results showed that comammox dominated nitrification (55.71%-81.21%) in less disturbed basins characterized by extensive forests and grassland, while AOB became the major player (53.83%-76.43%) in highly developed basins with drastic urban and agricultural development. In addition, increasing anthropogenic land use activities within the watershed lowered the alpha diversity of comammox communities and simplified the comammox network. Additionally, the alterations of NH4+-N, pH and C/N induced by land use change were found to be crucial drivers in determining the distribution and activity of AOB and comammox. Together, our findings cast a new light on aquatic-terrestrial linkages from the view of microorganism-mediated nitrogen cycling and can further be applied to target watershed land use management.

[Contribution Analysis of External Source Pollution Load and Environmental Capacity Estimation of Reservoirs in Central Yunnan Plateau].

To explore the source of the pollution load and its contribution rate in the upper reaches of the plateau reservoir and to analyze the water environment capacity of the reservoir, we selected the Chaishitan Reservoir in the Yunnan Plateau as the research object, applied the pollutant discharge coefficient method to estimate the source of external pollution in the upstream basin of the reservoir, used the simultaneous monitoring data of hydrology and water quality to calculate pollution load into the reservoir, and used the eutrophication model to calculate the maximum capacity of TN and TP in the reservoir under different water quality target scenarios. The results showed that:① the main characteristic pollutants in Chaishitan Reservoir and the above basin were TN and TP. ② COD and TP in the upper reaches of the reservoir mainly came from rural non-point source pollution, with contribution rates of 49.40% and 50.11%, respectively; NH4+-N and TN mainly came from urban domestic pollution sources, with contribution rates of 45.76% and 33.77%, respectively. Among the contributions of rural non-point source pollution, the contribution rates of COD and TP in Luliang District were 34.82% and 36.82%, respectively. The contributions of COD, NH4+-N, TN, and TP to urban domestic pollution were the highest in Qilin District, all of which were up to 65%. ③ The inflows of COD, NH4+-N, TN, and TP were 28050.90, 2465.16, 4680.54, and 870.93 t·a-1, respectively. The inflow of TN and TP pollution load was 4637.80 t·a-1 and 125.04 t·a-1, respectively. ④ When the target of water quality was Class Ⅲ, and the requirements of the Water Function Zoning of Yunnan province were met, the environmental capacities of TN and TP were 1102.62 t·a-1 and 54.85 t·a-1, respectively. Rural non-point source pollution and urban domestic pollution sources were the main sources of pollution in the upper reaches of Chaishitan Reservoir, which were priority control sources. These research results can provide a scientific theoretical basis for pollution source treatment in the plateau reservoir basin.

Toxicity Characterization of Environment-Related Pollutants Using a Biospectroscopy-Bioreporter-Coupling Approach: Potential for Real-World Toxicity Determination and Source Apportionment of Multiple Pollutants.

Exposure to environmental pollutants occurs ubiquitously and poses many risks to human health and the ecosystem. Although many analytical methods have been developed to assess such jeopardies, the circumstances applying these means are restricted to linking the toxicities to compositions in the pollutant mixtures. The present study proposes a novel analytical approach, namely, biospectroscopy-bioreporter-coupling (BBC), to quantify and apportion the toxicities of metal ions and organic pollutants. Using a toxicity bioreporter ADPWH_recA and Raman spectroscopy, both bioluminescent signals and spectral alterations had similar dosage- and time-response behavior to the toxic compounds, validating the possibility of coupling these two methods from practical aspects. Raman spectral alterations successfully distinguished the biomarkers for different toxicity mechanisms of individual pollutants, such as ring breathing mode of DNA/RNA bases (1373 cm-1) by Cr, reactive oxygen species-induced peaks of proteins (1243 cm-1), collagen (813 cm-1), and lipids (1255 cm-1) by most metal ions, and indicative fingerprints of organic toxins. The support vector machine model had a satisfactory performance in distinguishing and apportioning toxicities of individual toxins from all input data, achieving a sensitivity of 88.54% and a specificity of 97.80%. This work set a preliminary database for Raman spectral alterations of whole-cell bioreporter response to multiple pollutants. It proved the state-of-the-art concept that the BBC approach is feasible to rapidly quantify and precisely apportion toxicities of numerous pollutant mixtures.

Ecological water replenishment to the Yongding River, China: effects of different water sources on inorganic ions and organic matter characteristics.

Ecological water replenishment is considered to be an important project to adjust river ecosystems with water shortages and degradation, and its impact on the water quality of the target river section deserves attention. By investigating the characteristics of inorganic ions and organic components of the Beijing section of the Yongding River (YDR) from upstream to downstream, the sources of inorganic ions and dissolved organic matter (DOM) during an ecological water replenishment event were analysed and discussed. This study illustrated the hydrochemical response to different supplemental water sources in three sections of the YDR (mountain gorge section (MGS), urban plain section (UPS), and suburb plain section (SPS)). The results showed that the total dissolved solids (TDS) and ion concentrations were significantly different (p < 0.001) in the three river sections due to different supplemental water sources. The highest concentration of TDS was found in the UPS (870.92 mg/L) replenished by reclaimed water, while the lowest concentration of TDS was found in the SPS (306.95 mg/L) replenished by the water of the South-to-North Water Diversion Project (SNWD). Despite the differences in the water sources of replenishment, the optical parameters of DOM and fluorescent components showed similar protein-like dominated endogenous source characteristics in the three river sections of the YDR, which was due to the influence of reservoir water (MGS and SPS) and reclaimed water (UPS). Our study emphasizes the importance of understanding the impact of different water sources on the water replenishment process, which provides a scientific reference for the management of ecological water replenishment.

Base type determines the effects of nucleoside monophosphates on microalgae-bacteria symbiotic systems.

Microalgae are promising sources of clean energy. Bioflocculation by cocultured bacteria is an effective way to harvest microalgae. As a key foundation for microorganisms, phosphorus is theoretically effective in shaping microalgae production and flocculation. In this study, the impacts of 23 nucleoside monophosphates on Auxenochlorella pyrenoidosa growth, lipid synthesis, and self-settlement and on the symbiotic bacterial system were investigated. Adenosine monophosphate was the most effective in enhancing microalgae development (2.14-3.16 × 108 cells/mL) and lipid production (average 10.48%) and resulted in a low settling velocity. Samples were divided into two groups, purine and pyrimidine feeding, according to a random forest analysis (OOB = 0%, p < 0.001). Purine feeding resulted in the highest soluble extracellular protein and polysaccharide secretion (p < 0.01). KEGG ortholog count prediction of functional genes related to biofilm formation was conducted using PICRUSt2, and significant upregulation (FC ≥ 1.77, p < 0.05) of the extracellular polymeric substance formation functional group was observed in the adenosine and guanosine treatments. The symbiotic bacterial community structure differed substantially between purine- and pyrimidine-feeding systems. In summary, these results indicated that the effect of nucleoside monophosphates on the microalgae-bacteria system is determined by the base type (purine or pyrimidine) rather than the molecular structure (cyclic or noncyclic).

Water quality degradation drives the release and fractionation transformation of trace metals in sediment.

The behavior and stability of trace metals in sediment are important to the ecology of rivers. Deteriorated water quality from domestic wastewater discharge has been studied extensively, but the effect of domestic wastewater on trace metals in sediment is poorly understood. To investigate this, we simulated the water quality degradation process through leaching experiments using domestic wastewater as the leaching solution. The results indicated that domestic wastewater does not negatively influence the stability and fractionation of trace metals in this experimental model, the existence of phosphate was the pacing factor for this phenomenon. Single-factor control treatment groups showed that a leaching solution with pH < 6, NaCl, NH4Cl, NaNO3, and humic acid promoted the dissolution of trace metals from sediment, whereas NaH2PO4 inhibited this process and increased their stability in sediment. The response of trace metals behavior to NaCl, NH4Cl, and extreme pH levels was more sensitive than NaNO3 and HA. Chloride ions can form relatively stable compounds with trace metals, reducing the activity of trace metals in the solution and promoting the release of trace metals from sediment, but it has positive effect on Pb and Zn stability and negative effect on Cu. Extreme pH conditions (pH > 10) and higher concentrations of leaching solutions (NaCl, NH4Cl, NaNO3, and HA) led to an increase in the Cu leaching concentration from sediment and the transformation to unstable fractions, while the impact on the stability of Zn and Pb was beneficial or had little effect. These experiment groups indicated that phosphate is beneficial to the stability of trace metals even at the condition of water degradation and can decrease the ecological risk caused by trace metals.

Characterizing the spatiotemporal distribution of dissolved organic matter (DOM) in the Yongding River Basin: Insights from flow regulation.

Artificial flow regulation is an important measure to alleviate water shortages and improve the ecological quality of river basins. Dissolved organic matter (DOM) plays a crucial role in the carbon cycle and regulates biogeochemical and ecological processes in aquatic systems. Among the numerous studies on the effects of anthropogenic activities on the quality and quantity of river DOM, few studies have focused on the influence of different artificially regulated flow on the composition, source, and fate of fluvial DOM. This study aims to elucidate the impact of different artificial regulation modes of river flows on the source, migration, and transformation of DOM. The optical properties of DOM were used to explore the temporal and spatial distribution characteristics of DOM in the Yongding River Basin, where artificial regulation of river flows by cross-basin and inner-basin water transfers were implemented. Excitation-emission matrix fluorescence spectroscopy coupled with parallel factor analysis revealed four fluorescent substances of DOM in the water: one microbial humic-like (C1), one terrestrial humic-like (C2), one non-point source pollution humic-like (C4), and one tryptophan-like (C3) substance. Due to cross-basin water transfer from the Yellow River, the flow is the highest (21.79 m3/s) during spring, which was the reason that the signal of C2 was stronger during spring (71.45 QSU) compared to summer (57.12 QSU) and autumn (51.78 QSU). Due to inner-basin water transfer from upstream reservoirs, C3 derived from autochthonous sources were higher during autumn (130.81 QSU) than during spring (77.17 QSU) and summer (93.16 QSU). With no water transfer, more C1 were present at higher temperatures during summer (141.51 QSU) than during spring (126.73 QSU) and autumn (128.8 QSU). Moreover, C4 originating from urban and/or agricultural non-point source runoff increased during summer (57.07 QSU) than during spring (33.29 QSU) and autumn (52.27 QSU) because of increased rainfall. The different modes of artificial regulation of river flows changed the hydrological characteristics of the basin, which in turn altered the temporal and spatial distribution characteristics of the quantity and quality of DOM. The finding of this study can help promote the development of appropriate management strategies for artificial regulation of river flows in the basin. Furthermore, this study provides a basis for investigating the effects of different artificial flow regulations on the carbon cycles and ecological risks of rivers in the basin.

Nitrifiers Cooperate to Produce Nitrous Oxide in Plateau Wetland Sediments.

The thawing of dormant plateau permafrost emits nitrous oxide (N2O) through wetlands; however, the N2O production mechanism in plateau wetlands is still unclear. Here, we used the 15N-18O double tracer technique and metagenomic sequencing to analyze the N2O production mechanism in the Yunnan-Kweichow and Qinghai-Tibet plateau wetlands during the summer of 2020. N2O production activity was detected in all 16 sediment samples (elevation 1020-4601 m: 2.55 ± 0.42-26.38 ± 3.25 ng N g-1 d-1) and was promoted by nitrifier denitrification (ND). The key functional genes of ND (amoA, hao, and nirK) belonged to complete ammonia oxidizing (comammox) bacteria, and the key ND species was the comammox bacterium Nitrospira nitrificans. We found that the comammox bacterial species N. nitrificans and the ammonia oxidizing bacterial (AOB) species Nitrosomonas europaea cooperate to produce N2O in the plateau wetland sediments. Furthermore, we inferred that environmental factors (elevation and total organic matter (TOM)) influence the cooperation pattern via N. nitrificans, thus affecting the N2O production activity in the plateau wetland sediments. Our findings advance the mechanistic understanding of nitrifiers in biogeochemical cycles and global climate change.

Leaching Characteristics of Heavy Metals in the Baghouse Filter Dust from Direct-Fired Thermal Desorption of Contaminated Soil.

After thermal desorption, the total amount of heavy metals (HMs) is enriched in baghouse filter dust. To further understand the related environmental impact, the leaching characteristics under various conditions must be explored. Therefore, this study aimed to examine the leaching characteristics of seven HMs in the dust generated in the direct-fired thermal desorption process and to compare the differences in heavy metal leaching characteristics in the soil before and after thermal desorption. The leaching characteristics and bioaccessibility of seven HMs-arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), lead (Pb), nickel (Ni), and zinc (Zn)-were analyzed in dust and in soil before and after thermal desorption. The activity of HMs in dust was strong. Therefore, environmental effects and effects on human health should be considered in the treatment of soil and dust after thermal desorption.

Effect of Normalization Methods on Accuracy of Estimating Low- and High-Molecular Weight PAHs Distribution in the Soils of a Coking Plant.

Mapping spatial distribution of soil contaminants at contaminated sites is the basis of risk assessment. Hotspots can cause strongly skewed distribution of the raw contaminant concentrations in soil, and consequently can require suitable normalization prior to interpolation. In this study, three normalization methods including normal score, Johnson, and Box-Cox transformation were performed on the concentrations of two low-molecular weight (LMW) PAHs (i.e., acenaphthene (Ace) and naphthalene (Nap)) and two high-molecular weight (HMW) PAHs (i.e., benzo(a)pyrene (BaP) and benzo(b)fluoranthene (BbF)) in soils of a typical coking plant in North China. The estimating accuracy of soil LMW and HMW PAHs distribution using ordinary kriging with different normalization methods was compared. The results showed that all transformed data passed the Kolmogorov-Smirnov test, indicating that all three data transformation methods achieved normality of raw data. Compared to Box-Cox-ordinary kriging, normal score-, and Johnson-ordinary kriging had higher estimating accuracy of the four soil PAHs distribution. In cross-validation, smaller root-mean-square error (RMSE) and mean error (ME) values were observed for normal score-ordinary kriging for both LMW and HMW PAHs compared to Johnson- and Box-Cox-ordinary kriging. Thus, normal score transformation is suitable for alleviating the impact of hotspots on estimating accuracy of the four selected soil PAHs distribution at this coking plant. The findings can provide insights into reducing uncertainty in spatial interpolation at PAHs-contaminated sites.

Comparing with oxygen, nitrate simplifies microbial community assembly and improves function as an electron acceptor in wastewater treatment.

Biochemical oxidation and reduction are key processes in treating biological wastewater and they require the presence of electron acceptors. The functional impact of electron acceptors on microbiomes provides strategies for improving the treatment efficiency. This research focused on two of the most important electron acceptors, nitrate and oxygen. Molecule ecological network, null model, and functional prediction based on high-throughput sequencing were used to analyze the microbiomes features and assembly mechanism. The results revealed nitrate via the homogeneous selection (74.0%) decreased species diversity, while oxygen via the homogeneous selection (51.1%) and dispersal limitation (29.6%) increased the complexity of community structure. Microbes that were more strongly homogeneously selected for assembly included polyphosphate accumulating organisms (PAOs), such as Pseudomonas and variovorax in the nitrate impacted community; Pseudomonas, Candidatus_Accumulibacter, Thermomonas and Dechloromonas, in the oxygen impacted community. Nitrate simplified species interaction and increased the abundance of functional genes involving in tricarboxylic acid cycle (TCA cycle), electron transfer, nitrogen metabolism, and membrane transport. These findings contribute to our knowledge of assembly process and interactions among microorganisms and lay a theoretical basis for future microbial regulation strategies in wastewater treatment.

Brownification of freshwater promotes nitrogen-cycling microorganism growth following terrestrial material increase and ultraviolet radiation reduction.

Brownification is an increasingly concerning phenomenon faced by aquatic ecosystems in the changing environments, and the microbiome plays an irreplaceable role in material circulation and food web construction. Insight into the influence of brownification on microbial communities is crucial from an ecological standpoint. In this study, we simulated brownification using a the mesocosm system and explored the relationship between the characteristics of microbial communities and brownification using excitation-emission matrix (EEM) fluorescence spectroscopy and ultraviolet (UV) spectroscopy combined with high-throughput amplicon sequencing techniques. The results showed that brownification reduced the richness of the microbial community and selectively promoted the growth of nitrogen-cycling microorganisms, including hgcI_clade, Microbacteriaceae, and Limnohabitans. Brownification affected microbial communities by altering the carbon source composition and underwater spectrum intensity; UV, blue, violet, and cyan light were significantly (p < 0.05) correlated with microbial community richness, and random forest analysis revealed that UV, C1 (microbial humic-like), and C3 (terrestrial humic-like) were the major factors significantly influencing microbiome variation. We found that brownification affected microorganisms in shallow lakes, especially nitrogen cycling microorganisms, and propose that controlling terrestrial material export is an effective strategy for managing freshwater brownification.

Response of soil microbial communities to petroleum hydrocarbons at a multi-contaminated industrial site in Lanzhou, China.

Total petroleum hydrocarbon (TPH) contamination poses threats to ecological systems and human health. Many studies have reported its negative impacts on soil microbes, but limited information is known about microbial change and response to multiple TPH contamination events. In this study, we investigated TPH contamination level, microbial community structure and functional genes at a multi-contaminated industrial site in Lanzhou, where a benzene spill accident caused the drinking water crisis in 2014. TPHs distribution in soils and groundwater indicated multiple TPH contamination events in history, and identified the spill location where high TPH level (6549 mg kg-1) and high ratio of low-molecular-weight TPHs (>80%) were observed. In contrast, TPH level was moderate (349 mg kg-1) and the proportion of low-molecular-weight TPHs was 44% in soils with a long TPH contamination history. After the spill accident, soil bacterial communities became significant diverse (p = 0.047), but the dominant microbes remained the same as Pseudomonadaceae and Comamonadaceae. The abundance of hydrocarbon-degradation related genes increased by 10-1000 folds at the site where the spill accident occurred in multi-contaminated areas and was significantly related to 2-ring PAHs. Such changes of microbial community and hydrocarbon-degradation related genes together indicated the resilience of soil indigenous microbes toward multiple contamination events. Our results proved the significant change of bacterial community and huge shift of hydrocarbon-degradation related genes after the spill accident (multiple contamination events), and provided a deep insight into microbial response at industrial sites with a long period of contamination history.

Occurrence of polycyclic aromatic compounds and potentially toxic elements contamination and corresponding interdomain microbial community assembly in soil of an abandoned gas station.

Bacteria, archaea and fungi usually coexist in various soil habitats and play important roles in biogeochemical cycle and remediation of contamination. Despite their significance, their combined bioassembly pattern, ecological interactions and driving factors in contaminated soils still remain obscure. To fill the gap, a systemic investigation on the characteristics of microbial community including bacteria, archaea and fungi, assembly patterns and environmental driving factors was conducted in an abandoned gas station soils which were contaminated by polycyclic aromatic compounds and potentially toxic elements for decades. The results showed that the soils were contaminated excessively by benzo[a]pyrene (0.46-2.00 mg/kg) and Dibenz[a,h]anthracene (0.37-1.30 mg/kg). Multitudinous contaminant-degrading/resistant microorganisms and unigenes were detected, indicating potential of the soils to mitigate the pollution. Compared with fungi and archaea, the bacteria had higher community diversity and were more responsive to seasonal shifts. Functional genes (nidB, nahAb, nahAa, adhP, adh, adhC, etc.) involved in biodegradation were highly enriched in summer (1.96% vs 1.80%). The co-occurrence network analysis showed summer communities exhibit a more robust network structure and positive interactions than winter communities. The fungi Neocucurbitaria, Penicillium, Fusarium, Chrysosporium, Knufia, Filobasidium, Wallemia and Rhodotorula were identified as the keystone taxa, indicating that fungi also had important positions in the interdomain molecular ecological networks of both seasons. The network topological properties and |ßNTI| (66.7%-93.3% greater than 2) results indicated the deterministic assembly processes of the microbial communities in the contaminated soil. Acenaphthylene, benzo[b]fluoranthene, indeno[1,2,3-cd]perylene, benzo[g,h,i]pyrene and 9-fluorenone were the key environmental factors driving the deterministic assembly processes of the interdomain microbial community in the contaminated soil. These findings extended our knowledge of interdomain microbial community assembly mechanisms and ecological patterns in natural attenuation and provide valuable guidance in associated bioremediation strategies.