Shifts of bacterial community and molecular ecological network at the presence of fluoroquinolones in a constructed wetland system

Interaction of sulfate-reducing bacteria and methanogenic archaea in urban sewers, leads to increased risk of proliferation of antibiotic resistance genes

Sewers are considered a potential reservoir of antibiotic resistance. However, the generation of antibiotic resistance genes (ARGs) in microbial communities in pipeline biofilms under antibiotic stress remains unexplored. In this study, the biodegradation efficiency of tetracycline (TCY) and sulfamethoxazole (SMX) was evaluated in a pilot reactor of the sewers. The results showed that under TCY and SMX stress, the degradation efficiency of sewage water was inhibited. The most abundant ARGs detected in the biofilm samples were TCY-related genes (e.g., tetW/N/W, tetC, and tetM), accounting for 34.1%. The microbial community composition varied, and the correlation analysis showed that antibiotic stress had a certain impact on the biological metabolic activity and function of the urban sewers. The community structure and diversity of biofilms enabled the evaluation of the bioconversion of antibiotics. Notably, Anaerocella and Paludibacter directly influenced the methanogenesis and sulfate reduction processes, playing a key role in the interaction between sulfate-reducing bacteria and methanogenic archaea. These microorganisms facilitated the proliferation of ARGs (tet and sul) in the biofilms through horizontal gene transfer. This study provides insight into the front-end control of ARGs, further improving sewage treatment plant processes and reducing the environmental and health risks caused by antibiotic abuse.

Trade-off between electrochemical and microbial nutrient eliminations in iron anode-assisted constructed wetlands: The specificity of voltage level

Holistic understanding of electrocatalytic behaviors and microbiological mechanisms respond to voltage level (VL) benefits constructing performance-pathway-community linkages in iron anode-assisted constructed wetlands (IACWs). Herein, five solar-driven IACWs at 0, 1, 5, 10, and 15 V were established to treat secondary effluent for 109 days across moderate to low water temperatures (WTs). Results showed that total nitrogen (TN) (4.87-54.42%) and total phosphorus (TP) (20.66-97.35%) removals both ascended as VL raised, which primarily occurred in the cathodic regions and anodic upstream, respectively. More sustainable nitrogen elimination was achieved at lower VLs (≤ 5 V). Electrochemical contribution quantification revealed that electrochemical denitrogenation strengthened as VL improved (144.3-965.7 mg m-2 d-1), whereas severe anodic hardening and cathodic clogging in later operation impaired the dominant electrochemical denitrification at higher VLs (≥ 10 V). In contrast, microbial denitrogenation followed hump-shaped variational pattern with rising VL (peaked at 5 V). Microbial community and function analyses further clarified that despite VL elevation induced denitrifying microbiota evolution and up-regulated functional gene abundance, microbial denitrification function was significantly constrained at higher VLs. Particularly, the highest network complexity (at 1 V) and modularity (at 5 V) bred IACWs to better withstand low WT and high iron concentration. Overall, 5 V balanced electrochemical and microbial denitrogenation to obtain persistently effective TN removal. Additionally, intensified electro-coagulation dephosphorization was verified to remove most TP via adsorption and co-precipitation. This work provided a preferred VL regulation strategy to facilitate in situ sustainable nutrient purification of low-polluted wastewater in IACWs.

Assessment of Bacterial Community Structure, Associated Functional Role, and Water Health in Full-Scale Municipal Wastewater Treatment Plants

The present study collected wastewater samples from fourteen (14) full-scale wastewater treatment plants (WWTPs) at different treatment stages, namely, primary, secondary, and tertiary, to understand the impact of WWTP processes on the bacterial community structure, their role, and their correlation with environmental variables (water quality parameters). The findings showed that the bacterial communities in the primary, secondary, and tertiary treatment stages are more or less similar. They are made up of 42 phyla, 84 classes, 154 orders, 212 families, and 268 genera. Proteobacteria, Bacteroidetes, Cloacimonetes, Firmicutes, Euryarchaeota, Verrucomicrobia, Cyanobacteria, Desulfomicrobium, Thauera, Zavarzinia, and Nitrospirae, among others, dominated the bacterial community structure in all treatment stages. The biochemical oxygen demand was 7-12 times, chemical oxygen demand (COD) was 6 times, and total suspended solids (TSS) was 3.5 times higher in the wastewater than what the Central Pollution Control Board (CPCB) in New Delhi, India, allows as standard discharge. The correlation analysis using the Pearson r matrix and canonical correspondence analysis (CCA) also confirmed the fact that these water quality parameters (especially BOD and COD) play a pivotal role in deciphering the community structure in WWTPs.

High-generation tetracyclines shifted microbial community composition and induced the emergence of antibiotic resistant bacteria in soil

Tetracyclines (TCs) have been widely detected in agricultural soil due to their widespread use in animal husbandry. The impact of low-generation TCs, i.e., the first- and second- generations, on soil ecosystem has attracted widespread attention. However, the dynamic response of soil microbial community to high-generation TCs, i.e., the third- and fourth- generations, remains largely unknown. Herein, we characterized the variations in the composition, diversity and succession of microbial community and the proliferation of antibiotic resistance genes (ARGs) under the stress of four generations of TCs in brown soil and red soil. The results demonstrated that the exposure of low- and high- generation TCs consistently decreased the alpha diversity and stimulated the succession rate of microbial community in soil. High-generation TCs strongly shifted microbial community composition by reducing community resilience. The complexity of microbial networks and cross-module associations were strengthened to cope with the stress of high-generation TCs in soil. The abundance of ARGs was exacerbated by 1.75 times in response to the fourth-generation TCs compared to control in brown soil. The potential bacterial hosts of ARGs were more diverse in brown soil exposed to high-generation TCs, but the dominant hosts were not changed. These results highlight the potential ecological risk of the newly developed antibiotics, which is helpful for a comprehensive risk assessment of emerging contaminants.

Illuminating the role of powder carrier materials in shaping sludge aggregation in wastewater treatment: Insights from extended operation performance to microbial response mechanism

This study uncovered the response of novel micro-granule wastewater treatment technology to different powder carrier materials. Characteristics and distinctions among different systems were assessed based on process performance, sludge aggregation capacity, and microbial metabolism. Zeolite carrier system exhibited remarkable nitrogen removal efficiency of 89.6 ± 0.9 %, while diatomite carriers, in conjunction with intermittent aeration, enhanced simultaneous nitrification and denitrification from 2.6 % to 27.1 %. Iron-based carriers demonstrated efficient phosphorus removal (94.7 ± 1.2 %) through both chemical and microbial pathways. Specific surface area, pore structure and biocompatibility of powder carriers determined the formation and size of micro-granules. Tryptophan-like substances, C-(C/H), and Npr in extracellular polymeric substances strongly correlated with sludge hydrophobicity and granulation. Significant enrichment in norank_Comamonadaceae and Nitrosomonas in zeolite powder carrier system promoted partial nitrification and endogenous denitrification. Differences in metabolic pathways elucidated the up-regulation of amino acid synthesis, energy metabolism, and membrane transport as potential mechanisms driving micro-granule formation and efficient treatment performance.

Ciprofloxacin affects nutrient removal in manganese ore-based constructed wetlands: Adaptive responses of macrophytes and microbes

Ciprofloxacin (CIP) has received considerable attention in recent decades due to its high ecological risk. However, little is known about the potential response of macrophytes and microbes to varying levels of CIP exposure in constructed wetlands. Therefore, lab-scale manganese ore-based tidal flow constructed wetlands (MO-TFCWs) were operated to evaluate the responses of macrophytes and microbes to CIP over the long term. The results indicated that total nitrogen removal improved from 79.93% to 87.06% as CIP rose from 0 to 4 mg L-1. The chlorophyll content and antioxidant enzyme activities in macrophytes were enhanced under CIP exposure, but plant growth was not inhibited. Importantly, CIP exposure caused a marked evolution of the substrate microbial community, with increased microbial diversity, expanded niche breadth and enhanced cooperation among the top 50 genera, compared to the control (no CIP). Co-occurrence network also indicated that microorganisms may be more inclined to co-operate than compete. The abundance of the keystone bacterium (involved in nitrogen transformation) norank_f__A0839 increased from 0.746% to 3.405%. The null model revealed drift processes (83.33%) dominated the community assembly with no CIP and 4 mg L-1 CIP. Functional predictions indicated that microbial carbon metabolism, electron transfer and ATP metabolism activities were enhanced under prolonged CIP exposure, which may contribute to nitrogen removal. This study provides valuable insights that will help achieve stable nitrogen removal from wastewater containing antibiotic in MO-TFCWs.

Insights into the response mechanisms of activated sludge system under long-term dexamethasone stress

Dexamethasone (DEX) is a hormone drug that is often detected in wastewater treatment plants, but its impact on activated sludge systems is unknown. This study explored the long-term effects of DEX on nutrient removal, microbial activities, microbial assembly, and microbial interactions in the activated sludge system. During the 90-day DEX exposure experiment, both chemical oxygen demand and total nitrogen removal efficiencies were initially inhibited and then recovered. Microbial activities, i.e., specific oxygen uptake rate and denitrification, did not differ significantly from that of the control reactor (p > 0.05), possibly due to the secretion of extracellular polymers that act as a protective barrier against excess reactive oxygen species induced by DEX. This barrier protects cell membrane integrity and ensures stable treatment performance. Analysis of microbial assembly identified the drift of stochastic processes (from 92.7 % to 51.8 %) and homogeneous selection of deterministic processes (from 1.6 % to 38.7 %) as the main driving forces of microbial community structure succession under long-term DEX stress. Although long-term exposure to 1000 μg/L DEX did not significantly increase the abundance levels of functional bacteria (Nitrosomonas and 996-1) and key genes (AmoCAB and Hao), the ammonia oxidation capacity of the activated sludge system was enhanced. Analysis of microbial interactions indicated that streamlining of functional subnetworks and increased cooperation were the primary reasons. This is the first study to explore the long-term effects of DEX on activated sludge and provide insights into microbial interaction and assembly. Moreover, the findings of this study broaden our knowledge and lay an experimental foundation for reducing risks associated with hormone drugs.

Heavy metal contamination impacts the structure and co-occurrence patterns of bacterial communities in agricultural soils

Heavy metal (HM) contamination caused by mining and smelting activities can be harmful to soil microbiota, which are highly sensitive to HM stress. Here, we explore the effects of HM contamination on the taxonomic composition, predicted function, and co-occurrence patterns of soil bacterial communities in two agricultural fields with contrasting levels of soil HMs (i.e., contaminated and uncontaminated natural areas). Our results indicate that HM contamination does not significantly influence soil bacterial α diversity but changes the bacterial community composition by enriching the phyla Gemmatimonadetes, Planctomycetes, and Parcubacteria and reducing the relative abundance of Actinobacteria. Our results further demonstrate that HM contamination can strengthen the complexity and modularity of the bacterial co-occurrence network but weaken positive interactions between keystone taxa, leading to the gradual disappearance of some taxa that originally played an important role in healthy soil, thereby possibly reducing the resistance of bacterial communities to HM toxicity. The predicted functions of bacterial communities are related to membrane transport, amino acid metabolism, energy metabolism, and carbohydrate metabolism. Among these, functions related to HM detoxification and antioxidation are enriched in uncontaminated soils, while HM contamination enriches functions related to metal resistance. This study demonstrated that microorganisms adapt to the stress of HM pollution by adjusting their composition and enhancing their network complexity and potential ecological functions.

Difference of Microbial Community in the Stream Adjacent to the Mixed Antibiotic Effluent Source

Released antibiotics from source to stream can influence bacterial communities and potentially alter the ecosystem. This research provides a comprehensive examination of the sources, distribution, and bacterial community dynamics associated with varied antibiotic release sources adjacent to the stream. The residual of antibiotics from different sources was determined, and the bacterial community structure was examined to reveal the differences in the bacteria community in the stream. The residual of antibiotics was quantified with liquid chromatography-tandem mass spectrometry (LC-MS/MS), and the Illumina MiSeq platform was utilized to sequence bacterial 16S rRNA genes, providing comprehensive insights into the bacterial community structure in the sediment across five different sites. Results indicated that the presence and distribution of antibiotics were significantly influenced by released sources. In the case of the bacterial community, the Proteobacteria and Firmicutes were the most dominant phyla in the sediment, and especially, the Firmicutes showed higher abundance in sites mostly affected by livestock sources. Additionally, livestock gut bacteria such as Clostridium saudiense, Proteiniclasticum ruminis, and Turicibacter sanguinis were prevalent in antibiotic-contaminated sites adjacent to livestock facilities. Overall, this study provides critical insights into the effect of antibiotic contamination by verifying the relationship between the occurrence of antibiotic residuals and the alteration in the bacterial community in the stream.

Impact analysis of hydraulic loading rate and antibiotics on hybrid constructed wetland systems: Insight into the response to decontamination performance and environmental-associated microbiota

Hybrid constructed wetlands (HCWs) are a promising solution for water ecology and environmental treatment, not only for conventional types of water pollution but also for antibiotics. Among the critical parameters for wetlands, the hydraulic loading rate (HLR) is especially important given the challenges of antibiotics treatment and frequent extreme rainfall. To investigate the removal performance of different HLRs on nutrients and antibiotics, as well as the response of antibiotics to nutrient removal, and the impact of HLRs on microbial communities, new HCWs with vertical flow constructed wetlands (VFCWs) and floating constructed wetlands (FCWs) in series were built. The results of the study showed that: (1) HCWs are highly effective in removing chemical oxygen demand (COD), NH4+-N, NO2--N, and total phosphorus (TP) at low HLR (L_HLR), with removal efficiencies as high as 97.8%, 99.6%, 100%, and 80.5%. However, high HLR (H_HLR) reduced their removal efficiencies; (2) The average removal efficiency of fluoroquinolones (FQs) under different HLRs was consistently high, at 99.9%, while the average removal efficiency of macrolides (MLs) was 96.3% (L_HLR) and 88.4% (H_HLR). The removal efficiency of sulfonamides (SAs) was susceptible to HLRs, and the removal of antibiotics occurred mainly in the rhizosphere zone of wetland; (3) High concentrations of antibiotics in HCWs were found to inhibit and poison plant growth and to reduce the removal efficiency of TP by 12%. However, they had a minor effect on the removal efficiency of carbon and nitrogen nutrients; (4) H_HLR altered the diversity and abundance of microbial communities in different compartments of the wetland and also reduced the relative abundance of Bacillus, Hydrogenophaga, Nakamurella, Denitratisoma and Acidovorax genera, which are involved in denitrification and phosphorus removal processes. This alteration in microbial communities was one of the main reasons for the reduced performance of nitrogen and phosphorus removal.

How efficiently does a metabolically enhanced system with denitrifying anaerobic methane oxidizing microorganisms remove antibiotics?

In this work, the novel N-damo (Nitrite dependent anaerobic methane oxidation) process was investigated at high biomass activities for its potential to remove simultaneously nitrite and methane, as well as selected antibiotics commonly found in sewage in trace amounts. For this purpose, two MBRs were operated at three high nitrite loading rates (NLRs), namely 76 ± 9.9, 161.5 ± 11.4 and 215.2 ± 24.2 mg N-NO⁻2 L-1 d-1, at long-term operation. The MBRs performance achieved a significantly high nitrite removal activity for an N-damo process (specific denitrifying activity of up to 540 mg N-NO⁻2 g-1 VSS d-1), even comparable to heterotrophic denitrification values. In this study, we have implemented a novel operational strategy that sets our work apart from previous studies with similar bioreactors. Specifically, we have introduced Cerium as a trace element in the feeding medium, which serves as a key differentiating factor. It allowed maintaining a stable reactor operation at high NLRs. Microbial community composition evidenced that both MBRs were dominated with N-damo bacteria (67-87% relative abundance in period III and I, respectively). However, a decrease in functional N-damo bacteria (Candidatus Methylomirabilis) abundance was observed during the increase in biomass activity and concentration, concomitantly with an increase of the other minor families (Hypomicrobiaceae and Xanthobacteraceae). Most of the selected antibiotics showed high biotransformation such as sulfamethoxazole, trimethoprim, cefalexin and azithromycin, whereas others such as roxithromycin and clarithromycin were only partially degraded (20-35%). On the contrary, ciprofloxacin showed almost no removal. Despite the metabolic enhancement, no apparent increase on the antibiotic removal was observed throughout the operation, suggesting that microbiological composition was of greater influence than its primary metabolic activity on the removal of antibiotics.

Insight into pharmaceutical and personal care products removal using constructed wetlands: A comprehensive review

Pharmaceutical and personal care products (PPCPs) were regarded as emerging environmental pollutants due to their ubiquitous appearance and high environmental risks. The wastewater treatment plants (WWTPs) became the hub of PPCPs receiving major sources of PPCPs used by humans. Increasing concern has been focused on promoting cost-effective ways to eliminate PPCPs within WWTPs for blocking their route into the environment through effluent discharging. Among all advanced technologies, constructed wetlands (CWs) with a combination of plants, substrates, and microbes attracted attention due to their cost-effectiveness and easier maintenance during long-term operation. This study offers baseline data for risk control and future treatment by discussing the extent and dispersion of PPCPs in surface waters over the past ten years and identifying the mechanisms of PPCPs removal in CWs based on the up-to-present research, with a special focus on the contribution of sediments, vegetation, and the interactions of microorganisms. The significant role of wetland plants in the removal of PPCPs was detailed discussed in identifying the contribution of direct uptake, adsorption, phytovolatilization, and biodegradation. Meanwhile, the correlation between the physical-chemical characteristics of PPCPs, the configuration operation of wetlands, as well as the environmental conditions with PPCP removal were also further estimated. Finally, the critical issues and knowledge gaps before the real application were addressed followed by promoted future works, which are expected to provide a comprehensive foundation for study on PPCPs elimination utilizing CWs and drive to achieve large-scale applications to treat PPCPs-contaminated surface waters.

Fate of ofloxacin in rural wastewater treatment facility: Removal performance, pathways and microbial characteristics

Ofloxacin (OFL) with high biological activity and antimicrobial degradation is a kind of the typical high concentration and environmental risk antibiotics in rural sewage. In this paper, a combined rural sewage treatment facility based on anaerobic baffled reactor and integrated constructed wetlands was built and the removal performance, pathway and mechanism for OFL and conventional pollutants were evaluated. Results showed that the OFL and TN removal efficiency achieved 91.78 ± 3.93 % and 91.44 ± 4.15 %, respectively. Sludge adsorption was the primary removal pathway of OFL. Metagenomics analysis revealed that Proteobacteria was crucial in OFL removal. baca was the dominated antibiotic resistance genes (ARGs). Moreover, carbon metabolism with a high abundance was conductive to detoxify OFL to enhance system stability and performance. Co-occurrence network analysis further elucidated that mutualism was the main survival mode of microorganisms. Denitrifers Microbacterium, Geobacter and Ignavibacterium, were the host of ARGs and participated in OFL biodegradation.

Microbial communities in tree root-compartment niches under Cd and Zn pollution: Structure, assembly process and co-occurrence relationship

Woody plants have showed great potential in remediating severely contaminated soils by heavy metals (HMs) due to their cost-efficient and ecologically friendly trait. It is believed the root-associated microbiota plays a vital role in phytoremediation for HMs. However, the ecological process controlling the assembly and composition of tree root-associated microbial communities under HMs stress remains poorly understood. Herein, we profiled the bulk soil, rhizosphere and endosphere microbial communities of trees growing in heavily Cd and Zn polluted soil. The microbiota was gradually filtered from bulk soil to the tree roots and was selectively enriched in roots with specific taxa, such as Proteobacteria and Ascomycota. The microbial community assembly along the soil-root continuum was mainly controlled by deterministic processes from bulk soil to the endosphere, with the normalized stochasticity ratio (NST) indices of 67.16-31.05 % and 30.37-15.02 % for bacteria and fungi, respectively. Plant selection pressure sequentially increased from bulk soil to rhizosphere to endosphere, with the reduced bacterial alpha diversity accompanying the consequently reduced complexity of the co-occurrence network. Together, the findings provide new evidence for horizontal transmission of endophytic microbiome from soil to the host, which can shed light on the future screening and application of microbial-assisted phytoremediation.

Functional stability correlates with dynamic microbial networks in anammox process

Understanding the relationship between dynamic microbial networks and functional stability is critical for the stable operation of anammox systems. Here, by operating an anammox reactor under constant condition over 250 days, it was found that the relative abundance of Planctomycetota gradually decreased while Chloroflexi and Proteobacteria increased, with stochasticity predominating the bacterial assembly as the reactor operation. Network analysis revealed a successional dynamic pattern of microbial interaction despite stable performance. The variation of subnetworks indicated Chloroflexi and Proteobacteria alternately played important role in anammox microbial network, and the negative relationship between anammox bacteria and heterotrophs could achieve a balance to keep functional stability under long-term operation. Furthermore, the identified keystone species mainly belonged to heterotrophs that were critical in maintaining network structure and system function. The results of this study revealed clear changing patterns of microbial community and network succession, which could provide valuable reference for other stably operated bioreactors.

Comparison of nitrogen removal performance and mechanism from low-polluted wastewater by constructed wetlands with two oxygen supply strategies: Tidal flow and intermittent aeration

Due to dissolved oxygen (DO) limited nitrogen removal efficiency in constructed wetlands (CWs), two representative oxygen-suppling CWs, i.e., tidal flow constructed wetlands (TFCWs) and intermittently aerated constructed wetlands (IACWs) were proposed to compare the effect of oxygen supply strategies on the nitrogen removal performance and mechanism. Results showed that the removal efficiencies of NH₄⁺-N and COD in IACWs were as high as 90.35-97.14% and 91.14-92.44%, respectively. In terms of TN, TFCWs (83.82%) showed a significantly higher removal efficiency than IACWs, and this result was derived with the flooded/drained phase (FP/DP) ratio of 21 h:3 h in TFCWs, because rhythmic FP and DP formed a high oxygen gradient at different depths of the system, which intensified the nitrification and denitrification simultaneously. The potential nitrifying and denitrifying bacteria (e.g., Nitrospira, Azospira, Haliangium, Bradyrhizobium and Arenimonas) were enriched more significantly in TFCWs compared with IACWs, as well as Bacillus for simultaneous nitrification and denitrification, which promoted nitrogen transformation together. Also, the results of molecular ecological network analysis showed that bacterial community structure in IACWs was more complex and robust than in TFCWs, because there were obviously more nodes and links as well as a higher proportion of negative interference. However, the relationship between genera in TFCWs was closer depending on shorter path distances, and the keystone genus (Nitrosomonas) in related to nitrification was considered to play an important role in nitrogen transformation performance.

Comparison of epiphytic and intestinal bacterial communities in freshwater snails (Bellamya aeruginosa) living on submerged plants

The combination of submerged plants and snails can combat eutrophication of freshwater systems by suppressing algal growth and assimilating nutrients. By consuming epiphytes, snails can benefit the growth of submerged plants. However, the efficiency of this phytoremediation strategy may depend on the microbes associated with the plants and snails. In this study, we compared the epiphytic bacterial communities on submerged plants (Vallisneria natans and Cabomba caroliniana) and intestinal bacterial communities of a snail, Bellamya aeruginosa, found on these plants using 16S rRNA gene sequencing. Epiphytic bacterial communities were similar between the two plant species and snails shared a high proportion of snail intestinal bacterial OTUs (75%) and genera (85%) with plants they grazed on. However, significant variations of Bray-Curtis distances differentiated epiphytic and intestinal bacterial communities. In addition, between the top 50 genera shared by intestinal and epiphytic bacterial communities, more Spearman correlations were detected within bacterial communities associated with snails than between communities associated with plants (190 vs. 143), and the correlations in epiphytic bacterial networks were more concentrated on certain genera, indicating they possessed distinct bacterial networks. This suggests the bacterial communities associated with snails do not depend strongly on the plant they graze on, which may be important for better understanding the role of snails in aquatic eco-restoration.

Response of microbial interactions in activated sludge to chlortetracycline

Chlortetracycline (CTC) has attracted increasing attention due to its potential environmental risks. However, its effects on bacterial communities and microbial interactions in activated sludge systems remain unclear. To verify these issues, a lab-scale sequencing batch reactor (SBR) exposed to different concentrations of CTC (0, 0.05, 0.5, 1 mg/L) was carried out for 106 days. The results showed that the removal efficiencies of COD, TN, and TP were negatively affected, and the system functions could gradually recover at low CTC concentrations (≤0.05 mg/L), but high CTC concentrations (≥0.5 mg/L) caused irreversible damage. CTC significantly altered bacterial diversity and the overall bacterial community structure, and stimulated the emergence of many taxa with antibiotic resistance. Molecular ecological network analysis showed that low concentrations of CTC increased network complexity and enhanced microbial interactions, while high concentrations of CTC had the opposite effect. Sub-networks analysis of dominant phyla (Bacteriodota, Proteobacteria, and Actionobacteriota) and dominant genera (Propioniciclava, a genus from the family Pleomorphomonadaceae and WCHB1-32) also showed the same pattern. In addition, keystone species identified by Z-P analysis had low relative abundance, but they were important in maintaining the stable performance of the system. In summary, low concentrations of CTC enhanced the complexity and stability of the activated sludge system. While high CTC concentrations destabilized the stability of the overall network and then caused effluent water quality deterioration. This study provides insights into our understanding of response in the bacteria community and their network interactions under tetracycline antibiotics in activated sludge system.

Photocatalytic degradation of lomefloxacin antibiotics using hydrothermally synthesized magnesium titanate under visible light-driven energy sources

Antibiotics in water system pose a human health risk due to the rise of antibacterial activity in the environmental web. Advanced oxidation processes are the potential to become an effective treatment technology for targeting antibiotics. This study demonstrates the visible light photocatalysis of lomefloxacin using magnesium titanate (MgTiO₃). The nanomaterial was subjected to computational analysis to study morphology, functional, and optical characteristics through FESEM, XRD, FTIR, BET, UV-Vis, etc. Importantly, MgTiO₃ had band gap energy of 3.09 eV. The photocatalytic studies were performed to observe different parameters affecting lomefloxacin degradation such as initial concentration, catalyst dosage, and pH. The nanomaterial exhibited the maximum lomefloxacin degradation. The study revealed that 30 mg/L of catalyst was optimum to degrade 10 mg/L of lomefloxacin with 30-W LED irradiation up to 150 min. Reactive species, namely, electron, hole, hydroxyl, and superoxide radicals, comprised the primary photocatalytic mechanism for lomefloxacin degradation. Ultimately, the summative result from this study highlights the suitability of the photocatalytic system to treat persistent antibiotics in aqueous environment.

Trace antibiotics increase the risk of antibiotic resistance genes transmission by regulating the biofilm extracellular polymeric substances and microbial community in the sewer

Sewer is considered a potential hotspot for antibiotic resistance, but the occurrence and proliferation of antibiotic resistance genes (ARGs) under trace antibiotics exposure have received little attention. This work evaluated the effects of tetracycline (TC) and sulfamethoxazole (SMX) individually and in combination in the sewer system and revealed the related mechanisms of ARG proliferation. The relative abundance of tetA and sul1 increased the most under TC and SMX stress, respectively, whereas sul1 increased the most under combined stress. Intl1 was abundant in both the liquid phase and the biofilm, and redundancy analysis confirmed that horizontal gene transfer was the main reason for the proliferation of ARGs. The increase in extracellular polymeric substances (EPS) secretion and the enhancement of the main hydrophobic functional groups facilitated the accumulation of biofilms, which promoted the proliferation of ARGs in biofilms. The relative abundance of most ARGs in the liquid phase was significantly correlated with EPS, protein and tryptophan-like substances. Furthermore, the microbial community structure and diversity affected the proliferation and spread of ARGs in the sewer. These findings contribute to our further understanding of the proliferation and development of ARGs in the sewer and lay the foundation for the front-end control of ARGs.

A Review on Microorganisms in Constructed Wetlands for Typical Pollutant Removal: Species, Function, and Diversity

Constructed wetlands (CWs) have been proven as a reliable alternative to traditional wastewater treatment technologies. Microorganisms in CWs, as an important component, play a key role in processes such as pollutant degradation and nutrient transformation. Therefore, an in-depth analysis of the community structure and diversity of microorganisms, especially for functional microorganisms, in CWs is important to understand its performance patterns and explore optimized strategies. With advances in molecular biotechnology, it is now possible to analyze and study microbial communities and species composition in complex environments. This review performed bibliometric analysis of microbial studies in CWs to evaluate research trends and identify the most studied pollutants. On this basis, the main functional microorganisms of CWs involved in the removal of these pollutants are summarized, and the effects of these pollutants on microbial diversity are investigated. The result showed that the main phylum involved in functional microorganisms in CWs include Proteobacteria, Bacteroidetes, Actinobacteria and Firmicutes. These functional microorganisms can remove pollutants from CWs by catalyzing chemical reactions, biodegradation, biosorption, and supporting plant growth, etc. Regarding microbial alpha diversity, heavy metals and high concentrations of nitrogen and phosphorus significantly reduce microbial richness and diversity, whereas antibiotics can cause large fluctuations in alpha diversity. Overall, this review can provide new ideas and directions for the research of microorganisms in CWs.

Effects of Enrofloxacin on Nutrient Removal by a Floating Treatment Wetland Planted with Iris pseudacorus: Response and Resilience of Rhizosphere Microbial Communities

Constructed wetlands (CWs), including floating treatment wetlands (FTWs), possess great potential for treating excessive nutrients in surface waters, where, however, the ubiquitous presence of antibiotics, e.g., enrofloxacin (ENR), is threatening the performance of CWs. In developing a more efficient and resilient system, we explored the responses of the FTW to ENR, using tank 1, repeatedly exposed to ENR, and tank 2 as control. Plant growth and nutrient uptake were remarkably enhanced in tank 1, and similar phosphorus removal rates (86~89% of the total added P) were obtained for both tanks over the experimental period. Contrarily, ENR apparently inhibited N removal by tank 1 (35.1%), compared to 40.4% for tank 2. As ENR rapidly decreased by an average of 71.6% within a week after each addition, tank 1 took only 4 weeks to adapt and return to a similar state compared to that of tank 2. This might be because of the recovery of microbial communities, particularly denitrifying and antibiotic-resistance genes containing bacteria, such as Actinobacteria, Patescibacteria, Acidovorax and Pseudomonas. After three ENR exposures over six weeks, no significant differences in the nutrient removal and microbial communities were found between both tanks, suggesting the great resilience of the FTW to ENR.

Simultaneously advanced removal of nitrogen and phosphorus in a biofilter packed with ZVI/PHBV/sawdust composite: Deciphering the succession of dominant bacteria and keystone species

In this study, a biofilter was developed with a ZVI/PHBV/sawdust (ZPS) composite for treating simulative secondary effluent from wastewater treatment plants. Results showed that effluent concentrations of NO₃^--N and TP in the ZPS biofilter were stable below 2.0 mg/L and 0.1 mg/L, corresponding to 95% NO₃^--N removal and 99% TP removal, respectively. Microbial community analysis revealed that the transformation of dominant taxa from Dechloromonas to Clostridium sensu stricto_7 from 30 d to 120 d suggested that the ZVI-induced succession of dominant fermentation bacteria ensured the stable carbon supply for denitrification. Co-occurrence network analysis showed that the ZVI directly enhanced the interaction of microbial community. Fe-related bacteria occupied a key position in the rare species, which might maintain the function of iron-mediated organic matter decomposition and denitrification. These findings provide an alternative for advanced removal of nitrogen and phosphorus in biofilters packed with ZPS composites.

Microbial community profiles in soils adjacent to mining and smelting areas: Contrasting potentially toxic metals and co-occurrence patterns

Mining and smelting activities have introduced severe potentially toxic metals (PTMs) contamination into surrounding soil settings. Influences of PTMs on microbial diversity have been widely studied. However, variations of microbial communities, network structures and community functions in different levels of PTMs contaminated soils adjacent to mining and smelting aera are still poorly investigated. In this study, microbial communities of soils around different levels of PTMs contamination were comprehensively studied by 16S rRNA gene amplicons high-throughput sequencing. Microbial interactions and module functions were also exploited to ascertain the discrepancies of PTMs concentration levels on microbial ecological functions. Results indicated that the microbial community composition was significantly distinct attributed to the phylum Protebacteria (p = 0.002) dominating in soil with high level PTMs contents but Actinobacteria (p = 0.002) in low level of PTMs-contaminated soil. Microbial α diversity was not significantly influenced by different levels of PTMs contaminations. Microorganisms proactively responded to PTMs content levels by means of strengthening network complexities and modularities among microbe-microbe interactions. The functions of main network modules were predicted associating membrane transport, amino acid metabolism, energy metabolism and carbohydrate metabolism. The PTMs detoxification and anti-oxidation were significantly strengthened at the high level of PTMs contamination. The present study demonstrated that modification of microbial community by the adaptive adjustment of microbial compositions and strengthening their network complexity and modularity.

Effects of water flow on performance of soil microbial fuel cells: Electricity generation, benzo[a]pyrene removal, microbial community and molecular ecological networks

Soil microbial fuel cells with water flow (W-SMFCs) as a driven force of substrate transport were constructed. Electricity generation, benzo[a]pyrene (BaP) removal, microbial communities and microbial molecular ecological networks were compared between W-SMFCs and their control reactors (without water flow, C-SMFCs) in 240 days of operation. The W-SMFCs started up faster than C-SMFCs (37 days vs. 50 days) and output higher startup voltage (148.45 mV vs. 111.90 mV). The water flow caused higher removal efficiency of BaP at sites >1 cm from the anode (S _{> 1 cm}) than at sites <1 cm from the anode (S _{< 1 cm}) in W-SMFCs, whereas in C-SMFCs, the removal efficiency of BaP at S_{< 1 cm} was higher than that at S_{> 1 cm}. The removal efficiency of BaP at S_{> 1 cm} in W-SMFCs was up to 1.7 times higher than that at S_{> 1 cm} in C-SMFCs on the 91^st day. After 240 days of operation, the biodegradation efficiency of absolute BaP amount was 45.95% in W-SMFCs, being 20% higher than that in C-SMFCs (38.17%). Moreover, the water flow caused highly tight interaction among the microbial species, which could be beneficial to BaP biodegradation. Conclusively, the water flow in soil was very beneficial for startup and biodegradation of BaP in SMFCs.

Ecological impact of antibiotics on bioremediation performance of constructed wetlands: Microbial and plant dynamics, and potential antibiotic resistance genes hotspots

Constructed wetlands (CWs) are nature-based solutions for treating domestic and livestock wastewater which may contain residual antibiotics concentration. Antibiotics may exert selection pressure on wetland's microbes, thereby increasing the global antibiotics resistance problems. This review critically examined the chemodynamics of antibiotics and antibiotics resistance genes (ARGs) in CWs. Antibiotics affected the biogeochemical cycling function of microbial communities in CWs and directly disrupted the removal efficiency of total nitrogen, total phosphorus, and chemical oxygen demand by 22%, 9.3%, and 24%, respectively. Since changes in microbial function and structure are linked to the emergence and propagation of antibiotic resistance, antibiotics could adversely affect microbial diversity in CWs. The cyanobacteria community seemed to be particularly vulnerable, while Proteobacteria could resist and persist in antibiotics contaminated wetlands. Antibiotics triggered excitation responses in plants and increased the root activities and exudates. Microbes, plants, and substrates play crucial roles in antibiotic removal. High removal efficiency was exhibited for triclosan (100%) > enrofloxacin (99.8%) > metronidazole (99%) > tetracycline (98.8%) > chlortetracycline (98.4%) > levofloxacin (96.69%) > sulfamethoxazole (91.9%) by the CWs. This review showed that CWs exhibited high antibiotics removal capacity, but the absolute abundance of ARGs increased, suggesting CWs are potential hotspots for ARGs. Future research should focus on specific bacterial response and impact on microbial interactions.

Effects of sulfamethoxazole on nitrogen removal and molecular ecological network in integrated vertical-flow constructed wetland

Response of nitrogen removal efficiency and microbial interactions to organic pollution has been a major issue in wastewater treatment system. However, the nitrogen removal efficiency and interactions among microbial community under antibiotics press is still unclear. Thus, the effect of sulfamethoxazole (SMX) on nitrogen removal and microbial responses of IVCWs was investigated through recorded the nitrogen removal efficiency before and after adding SMX and random matrix theory (RMT)-based network analysis. Results showed that better NH₄⁺-N removal (>90%) after a long period of operation were achieved in IVCWs, but NO₃^--N was accumulated. However, nitrate removal rates were significantly increased after long-term exposure (60 d) to 100 μgL^-1 SMX (from 27.35% to 35.57%) with relatively high SMX removal (53.50%). Surprisingly, the ammonia nitrogen removal rate (90.07-92.70%) were not significantly affected by SMX in IVCWs. Moreover, the bacterial richness was decreased and the bacterial community structures were altered by the presence of SMX, especially those of nitrogen-transforming microorganisms. Molecular ecological network analysis suggested that SMX had positive influences on denitrifying bacteria interactions but reduced the network complexity and microbial interactions on whole molecular network, and among-module connections were weakened obviously at SMX.

Bacterial diversity assessment of world's largest sewage-fed fish farms with special reference to water quality: a Ramsar site

Bacterial community structure is one of the essential components of aquaculture dynamics and plays an important role in maintaining wetland health. The present work is an effort to study the structure of bacterial communities in the world's largest sewage-fed fish farms, the East Kolkata Wetlands (EKWs), along with their predicted functional metabolic pathways and correlation with environmental variables. Sequencing data analysis revealed the abundance of genera such as Arcobacter (0-50%), Pseudomonas (0-15%), Sulfurospirillum (0-9%), Cloacibacterium (0-6%), hgcI clade (7-29%), C39 (0-9%), V6 (3-36%), Fluiivicola (1-6%) and Cyanobium (3-8%) in the EKWs. Further, water quality analysis of three treatment groups, i.e. Sewage, Sewage F-1 and Sewage F-2, revealed that dissolved oxygen (DO), biochemical oxygen demand (BOD) and chemical oxygen demand (COD) differed significantly and violated the standard prescribed norms (Central Pollution Control Board, CPCB, New Delhi) for fishery propagation and irrigation in India. Further, the correlation matrix analysis between the abundance of bacterial genera and environmental variables indicated that DO, BOD and COD were mainly responsible for bacterial community structure and their proliferation in the EKWs. Our results indicated that the abundance of genera such as Arcobacter, Pseudomonas, Sulfurospirillum and Cloacibacterium has an inverse relationship with BOD and COD. Our observations based on the bacterial community structure and deteriorated water quality indicate the ineffective functioning and poor management of this man-made constructed wetland.

Effect of substrate types on contaminant removals, electrochemical characteristics and microbial community in vertical flow constructed wetlands for treatment of urban sewage

The purpose of this study was to investigate the influence of substrates (quartz sand and coke) on the removal of pollutants (COD, NH₄⁺-N and TP), electrochemical characteristics and microbial communities of vertical flow constructed wetlands (VFCW) under high pollutant loads. During operation, the removal rates of COD, NH₄⁺-N and TP by VFCW-C (coke as substrate) were higher than that of VFCW-Q (quartz sand as substrate) by 9.73-19.41%, 5.03%-13.15% and 8.83%-14.58%, respectively. And the resistances of the VFCW-Q and VFCW-C were increased by 1228.9 Ω and 38.3 Ω, while their potentials were dropped from 182.4 mV to 377.9 mV-85.6 mV and 222.0 mV, respectively. The dominant bacteria at the bottoms of VFCW-Q and VFCW-C were individually aerobic denitrifying bacteria (ADNB; 14.98%)/ammonia oxidizing bacteria (AOB; 5.73%) and organics aerobic degrading bacteria (OADB; 12.48%)/ammonia oxidizing bacteria (AOB; 7.24%), while the predominant bacteria at their tops were separately ADNB (11.36%)/OADB (10.52%)/AOB (4.69%) and ADNB (15.09%)/AOB (8.86%) and OADB (3.20%) The removal of pollutants by VFCW-Q and VFCW-C may be mainly attributed to substrate adsorption and microbial degradation.

Current intensities altered the performance and microbial community structure of a bio-electrochemical system

A novel integrated bio-electrochemical system with sulfur autotrophic denitrification (SAD) and electrocoagulation (BESAD-EC) system was established to remove nitrate (NO₃^--N) and phosphorus from contaminated groundwater. The impacts of a current intensity gradient on the system's performance and microbial community were investigated. The results showed that NO₃^--N and total phosphorus (TP) could be effectively removed with maximum NO₃^--N reduction and TP removal efficiencies of 94.2% and 75.8% at current intensities of 200 and 400 mA, respectively. Lower current intensities could improve the removal efficiencies of NO₃^--N (≤200 mA) and phosphorus (≤400 mA), while higher current intensity (600 mA) caused the inhibition of nutrients removal in the system. MiSeq sequencing analysis revealed that low electrical stimulation improved the diversity and richness of microbial community, while high electrical stimulation reduced their diversity and richness. The relative abundance of some genus involved in denitrification and phosphorus removal processes such as Rhizobium, Hydrogenophaga, Denitratisoma and Gemmobacter, significantly (P < 0.05) reduced under high current conditions. This could be one of the main reasons for the deterioration of denitrification and phosphorus removal performance. The results of this study could be helpful to enhance the nutrient removal performance of bio-electrochemical systems in groundwater treatment processes.

Successional Dynamics of Molecular Ecological Network of Anammox Microbial Communities under Elevated Salinity

Response of microbial interactions to environmental perturbations has been a central issue in wastewater treatment system. However, the interactions among anammox microbial community under salt perturbation is still unclear. Here, we used random matrix theory (RMT)-based network analysis to investigate the dynamics of networks under elevated salinity in an anammox system. Results showed that high salinity (20 and 30 g/L NaCl) inhibited anammox performance. Salinity led to closer and more complex networks for the overall network and subnetwork of Planctomycetes and Proteobacteria, especially under low salinity (5 g/L NaCl), which could serve as a strategy to survive under salt perturbation. Planctomycetes, most dominant phylum and playing crucial roles in anammox, possessed higher proportion of competitive relationships (64.3%) under 30 g/L NaCl. OTU 109 (closely related to Ignavibacterium), the only network hub detected in the anammox system, also had larger amount of competitive relationships (27.3%) than the control (0%) under 30 g/L NaCl. Similar result was found for the most abundant keystone bacteria Candidatus Kuenenia. These increasing competitions at different taxa level could be responsible for the deterioration of nitrogen removal. Besides, all the network topological features tended to reach the values of the original network, which showed the network of microbial community could gradually adapt to the elevated salinity. Microbial network analysis adds a different dimension for our understanding of the response in microbial community to elevated salinity.

Occurrence of antibiotics and antibiotic resistance genes in the Fuxian Lake and antibiotic source analysis based on principal component analysis-multiple linear regression model

In recent years, the dramatic increase in antibiotic use has led to the evolution of antibiotic resistant genes (ARGs), posing a potential risk to human and aquatic ecological safety. In this study, source contribution and correlations between twelve antibiotics and their corresponding ARGs were firstly investigated in surface water in the Fuxian Lake. The results showed that sulfamethoxazole (SMX) (0.98-14.32 ng L^-1) and ofloxacin (OFL) (0.77-7.3 ng L^-1) were the dominant antibiotics in surface water, whereas erythromycin-H₂O (EM-H₂O), SMX and OFL posed the medium risk to aquatic organisms. Meanwhile, the mean concentrations of MLs in inflowing rivers were 5.6 times more than those in the lake, which was related to dilution and degradation. Moreover, the facter1 (co-sources L (Living quarters), M (Mining area), A (Agricultural district) and T (tourist area)) contributed 78% of antibiotic concentrations, and the source L was predominant. The results also revealed the prevalence of intL1, sul1 and sul2 in all the sampling sites, and that the abundance of ARGs in the lake was significantly lower (P < 0.01) than that in inflowing rives. Additionally, significant correlations (p < 0.0001) between intL1 and sulfanilamide resistance genes (sul1, sul2) were detected, indicating that intL1 promoted the propagation and they originated from the same anthropogenic sources. Overall, our findings revealed the presence of antibiotics and ARGs and their inconsistent correlations in the Fuxian Lake, which provides a foundation to support further exploration of the occurrence and transmission mechanisms of antibiotics and ARGs.

Biodegradation of sulfonamides in both oxic and anoxic zones of vertical flow constructed wetland and the potential degraders

The pollution of wastewater with antibiotics and antibiotics resistance genes has attracted public concerns about ecosystem and global health. Swine wastewater can contain high concentrations of antibiotics, especially sulfonamides, even after full-scale wastewater treatment. In this study, mesocosm-scale vertical flow constructed wetlands (VF-CWs) were applied to abate nutrients and antibiotics in swine wastewater containing sulfonamides. VF-CWs performed well in the removal of both nutrients and antibiotics. Sulfonamides did not influence total organic carbon (TOC) and total phosphorus (TP) removal, and even slightly enhanced NH₄⁺-N removal. High removal efficiencies (26.42-84.05%) were achieved for sulfadiazine (SDZ), sulfamethoxazole (SMX) and sulfamethazine (SMZ). Together with lab-scale sorption and biodegradation experiments, microbial degradation was found to be the most important removal mechanism for sulfonamides in VF-CWs. Sulfonamides addition increased bacterial alpha-diversity and changed microbial community structure. Moreover, antibiotics promoted antibiotic-resistant or -degrading bacteria. Bacillus, Geobacter and other seven genera were correlated with sulfonamides reduction under either aerobic or anaerobic condition. In summary, VF-CW is a suitable alternative for swine wastewater treatment, and biodegradation plays the key role in sulfonamides abatement. Main findings of the work. This was the first work to combine bacterial community analysis with microcosm experiments to uncover the major removal mechanism of sulfonamides in constructed wetlands.

Distinct microbial communities and their networks in an anammox coupled with sulfur autotrophic/mixotrophic denitrification system

Organ carbon are often used to enhance denitrification in wastewater treatment. However, their possible effects on microbial interactions are very limited. In this work, an anaerobic ammonium oxidation (anammox) coupled with sulfur autotrophic/mixotrophic denitrification (SAD/SMD) system was used to investigate the changes in microbial interactions among the microbial communities under different nutrient condition. The removal efficiency of total nitrogen increased from 70% (SAD) to 97% (SMD). The Illumina sequencing analysis indicated that Planctomycetes was the most dominant bacterial phylum in anammox system. Thiobacillus and Sulfurimonas, two typical autotrophic denitrifiers, decreased significantly from 31.9% to 17.7%-12.2% and 9.3%, when the nutrient condition changed from SAD to SMD (P < 0.05). Meanwhile, some heterotrophic or mixotrophic denitrifying bacteria, including Gemmobacter, Pseudomonas and Thauera increased significantly (P < 0.05). Molecular ecological network (MEN) analysis showed that the addition of organic carbon substantially altered the overall architecture of the network. Compared with SAD, the SMD had shorter path lengths, indicating higher transfer efficiencies of information and materials among different microorganism. The addition of organic carbon increased the microbial interaction complexity of Proteobacteria. The links of Thiobacillus, which was a typical sulfur-oxidizing autotrophic denitrifying bacteria, significantly reduced (P < 0.05) with the addition of organic carbon, while the links of the heterotrophic bacteria Geobacter significantly increased (P < 0.05). This study provided new insights into our understanding of the shifts in the bacteria community and their microbial interactions under different nutrient conditions (SAD and SMD) in sulfur-supported denitrification system.