Insight into the evolution of microbial community and antibiotic resistance genes in anammox process induced by copper after recovery from oxytetracycline stress

Mechanistic insight into Cu(II)-mediated transformation of oxytetracycline on Fe-bearing smectite: Evidence from kinetic modeling

Heavy metals like Cu(II) and oxytetracycline (OTC) frequently coexist in livestock manure and wastewater due to their widespread use as feed additives, forming Cu(II)-OTC complexes that influence OTC transport and transformation in groundwater. This study investigates Cu(II)-mediated OTC transformation on Fe-bearing smectite under dark, anoxic conditions. Results show that OTC adsorption on Fe-bearing smectite undergoes further transformation. Cu(II)-OTC complexes significantly enhance OTC adsorption, accounting for 23.6%, 99.4%, and 92.9% of total OTC at pH 3, 5, and 8.5, respectively, but inhibit OTC transformation. FTIR, XPS, and UPLC-QTOF analyses reveal redox reactions between Cu(II)-OTC complexes and Fe-bearing smectite, reducing Fe(III) to Fe(II). Transformation primarily involves the tricarbonylamide group at pH 3 and 5, extending to the dimethylamino group at pH 8.5. A kinetic model of OTC transformation identifies two key parameters: the transformation rate (k') and the reactive site quantity (Srxn). The k' varies with pH as follows: pH 3 < pH 8.5 < pH 5, while Fe concentration exhibits an inverse relationship with k', suggesting that mineral dissolution reduces the redox activity of Fe-bearing smectite. Furthermore, a linear correlation between the fraction of redox-active Cu(II)-OTC complexes and Srxn indicates that Cu(II) complexation occupies reactive sites on Fe-bearing smectite, inhibiting transformation. These findings highlight the importance of considering heavy metal-antibiotic interactions when assessing groundwater risks.

Multidimensional Insights into Organics Stress on Anammox systems: From a "Molecule-Cell-Ecology" Perspective

Anaerobic ammonium oxidation (anammox) is efficient and cost-effective for treating high-strength ammonia wastewater, but the organics in wastewater will affect its stability. To address this challenge, it is crucial to gain a deep understanding of the inhibitory effects and mechanisms of organics stress on anammox bacteria. The review provided a comprehensive classification of organics and evaluated their specific effects on the anammox system according to their respective characteristics. Based on the micro to macro perspective, the "molecule-cell-ecology" inhibitory mechanism of organics on anammox bacteria was proposed. The molecular observation systematically summarized the binding process and action sites of organics with anammox bacteria. At the cellular observation, the mechanisms of organics effects on extracellular polymeric substances, membranes, and anammoxosome of anammox bacteria were also expounded. At the ecological observation, the dynamic changes in coexisting populations and their role in organics transformation were further discussed. Further revelations on response mechanisms and inhibition mitigation strategies were proposed to broaden the applicability of anammox systems for organic wastewater. This review offered a multidimensional understanding of the organics inhibitory mechanism of anammox bacteria and provided a theoretical foundation for anammox systems.

Research on intensive nitrogen removal of municipal sewage by mainstream anaerobic ammonia oxidation process

The anaerobic ammonia oxidation (anammox) process is a pivotal nitrogen removal technique, playing a significant role in the field of wastewater treatment. The paper commences by delineating the merits of the anammox process in comparison to conventional nitrification-denitrification techniques. Subsequently, it delves into the characteristics of different sludge morphologies process of the behavior of anammox bacteria and their reactions to environmental factors. Revising the issues associated with managing urban sewage in mainstream areas., it discusses the issues faced by the anammox process under reduced nitrogen loads, such as restricted activity due to decreased the levels of ammonia nitrogen and nitrite concentrations, as well as the impact of environmental factors like low temperature, organic matter, and sulfur ions. Following this, a comprehensive review of various types of coupled anammox processes is provided, highlighting the advantages and characteristics of partial nitrification (PN), partial denitrification (PD), methane-dependent nitrite/nitrate reduction (DAMO), sulfur-driven autotrophic denitrification (SAD), iron ammonia oxidation (feammox) and algae photoautotrophy coupling techniques, emphasizing their significance in system stability and resource utilization efficiency. Future research directions include exploring the applicability of the anammox process under various temperature conditions and addressing NO3--N issues in effluent. The findings from these studies will offer valuable insights for further enhancing the optimization of the anammox process in mainstream urban wastewater treatment.

Effect of ciprofloxacin on the one-stage partial nitrification and anammox biofilm system: A multivariate analysis focusing on size-fractionated organic components

The impact of ciprofloxacin (CIP) in the partial nitrification and anammox biofilm system was investigated by multivariate analysis, focusing on size-fractionated organic components. The CIP dose of 10 μg/L did not inhibit the total nitrogen (TN) removal efficiency, even though the abundance of antibiotic resistant genes (ARGs) (i.e., qnrD, qnrB, qnrA, qnrS, and arcA) was elevated. However, a gradual higher CIP dosing up to 100 μg/L inhibited the TN removal efficiency, while the abundance of ARGs was still increased. Moreover, both the TN removal efficiency and the abundant ARGs were dwindled at 470 μg/L of CIP. As the CIP dose increased from 0 to 100 μg/L, the abundance of high molecular weight (MW) fractions (14,000 to 87,000 Da; 1000 to 14,000 Da) and humic/fulvic acid-like components in the soluble extracellular polymeric substances (HSS) decreased, with more increases of low MW (84-1000 Da; less than 84 Da) fractions and soluble microbial by-products in soluble extracellular polymeric substances (SMPS). Continuously increasing the CIP dose till 470 μg/L, an inverse trend of the changes of these organic components was noted, along with clear reductions of the microbial diversity and richness, and the abundance of key functional genes responsible for nitrogen removal. The predominance of functional gene amoA (related with ammonia oxidizing bacteria) was more significantly with more distribution of SMPS with relatively low MW and less distribution of HSS with relatively high MW, as well as polymer decomposing microorganisms such as Bryobacteraceae and the unclassified Saprospirales.

Effect of streptomycin sulphate on the nitrification system in activated sludge: insight into nitrification characteristic, antibiotic resistance gene and microbial community

Wastewater with residual streptomycin sulphate usually contains high content of ammonia-nitrogen. However, the biological removal process of ammonia-nitrogen under streptomycin sulphate circumstance was unclear. In this study, short-term and long-term effects of streptomycin sulphate on biological nitrification systems, including AOB, NOB, SAOR, SNOR and SNPR, were evaluated comprehensively. The results indicated IC50 for AOB and NOB were 7.5 and 6.6 mg/L. SAOR and SNPR could be decreased to 3.43 ± 0.52 mg N/(g MLSS·h) and 0.24 ± 0.03 mg N/(g MLSS·h) while the addition of streptomycin sulphate was 10 mg/L. When streptomycin sulphate addition was stopped, nitrification ability recovered slightly, SAOR and SNPR increased to 9.37 ± 0.36 mg N/(g MLSS·h) and 1.66 ± 0.49 mg N/(g MLSS·h), respectively. The protein of EPS increased gradually during the acclimatization process, and the maximal protein value was 68.24 mg/g MLSS on the 100th day, however, no significant change of polysaccharose was observed during the acclimatization process. High abundance of ARGs and intI1 was detected in effluent and sludge of the biological treatment system. The maximal relative abundance of aadA1 in the sludge appeared on the 140th day, and increased by 0.99 orders of magnitude. Biological diversity decreased significantly during the acclimatization process, relative abundance of nitrosomonas was changed from 9.07% to 38.68% on the 61st day, while relative abundance of nitrobacter was changed from 1.30% to 0.64%. It should be noted that relative abundances of nitrosomonas and nitrobacter were reduced to 16.17% and 0.25% on the 140th day. This study would be helpful for nitrogen removal in wastewater with antibiotic.

Response of sulfide autotrophic denitrification process and microbial community to oxytetracycline stress

The coexistence of antibiotics with sulfide and nitrate is common in sewage. Thus, this study explored the removal performance of nitrate and sulfide, and the response of extracellular polymer substances (EPS) and the microbial community to the sulfide autotrophic denitrification (SAD) process under oxytetracycline (OTC) stress. In Phase Ⅰ, the SAD system showed favouranle performance (nitrate removal rate ＞ 92.57%, sulfide removal rate ＞ 97.75%). However, in Phase Ⅳ, at OTC concentrations of 10, 15, and 20 mg/L, the NRE decreased to 76.13%, 40.71%, 11.37%, respectively, and the SRE decreased to 97.58%, 97.09%, 92.84%, respectively. At OTC concentrations of 0, 10, 15, and 20 mg/L, the EPS content were 1.62, 1.75, 2.03, and 1.42 mg/gVSS, respectively. The results showed that SAD performance gradually deteriorated under OTC stress. In particular, when the OTC concentration was 20 mg/L, the EPS content was lower than that of the control test, which could be attributed to the occurrence of microbial death. Finally, high-throughput sequencing results showed that OTC exposure led to gradual domination by heterotrophic denitrifying bacteria.

Regulation mechanism of hydrazine and hydroxylamine in nitrogen removal processes: A Comprehensive review

As the new fashioned nitrogen removal process, short-cut nitrification and denitrification (SHARON) process, anaerobic ammonium oxidation (anammox) process, completely autotrophic nitrogen removal over nitrite (CANON) process, partial nitrification and anammox (PN/A) process and partial denitrification and anammox (PD/A) process entered into the public eye due to its advantages of high nitrogen removal efficiency (NRE) and low energy consumption. However, the above process also be limited by long-term start-up time, unstable operation, complicated process regulation and so on. As intermediates or by-metabolites of functional microorganisms in above processes, hydroxylamine (NH2OH) and hydrazine (N2H4) improved NRE of the above processes by promoting functional enzyme activity, accelerating electron transport efficiency and regulating distribution of microbial communities. Therefore, this review discussed effects of NH2OH and N2H4 on stability and NRE of above processes, analyzed regulatory mechanism from functional enzyme activity, electron transport efficiency and microbial community distribution. Finally, the challenges and limitations for nitric oxide (NO) and nitrous oxide (N2O) produced from regulation of NH2OH and N2H4 are discussed. In additional, perspectives on future trends in technology development are proposed.

Microbial interactions play a keystone role in rapid anaerobic ammonium oxidation sludge proliferation and biofilm formation

Two mature anaerobic ammonium oxidation (anammox) consortia with high/low relative abundance of anammox bacteria were inoculated for the rapid sludge proliferation and biofilm formation in this study, named up-flow anaerobic sludge blanket reactor (UASB1) (high) and UASB2 (low), respectively. Results showed that the nitrogen removal efficiency of UASB2 reached 90.94% after the 120-day operation, which was 13% higher than that of UASB1. Moreover, its biomass amounts were 22.18% (biofilm) and 40.96% (flocs) higher than that of UASB1, respectively. Ca. Kuenenia possessed relative abundances of 29.32% (flocs), 27.42% (biofilm) and 31.56% (flocs), 35.20% (biofilm) in the UASB1 and UASB2, respectively. The relative abundances of genes involved in anammox transformation (hzs, nir) and carbon metabolism (fdh, lgA/B/C, acs) were higher in the UASB2, indicating that Ca. Kuenenia might produce acetate and glycogen to enhance microbial interactions. These findings emphasized the importance of microbial interactions in anammox sludge proliferation and biofilm formation.

Stress of cupric ion and oxytetracycline in Chlorella vulgaris cultured in swine wastewater

Chlorella culturing has the advantages in treatment of wastewater including swine wastewater from anaerobic digesters due to the product of biolipids and the uptake of carbon dioxide. However, there often exist high concentrations of antibiotics and heavy metals in swine wastewater which could be toxic to chlorella and harmful to the biological systems. This study examined the stress of cupric ion and oxytetracycline (OTC) at various concentrations on the nutrient removal and biomass growth in Chlorella vulgaris culturing in swine wastewater from anaerobic digesters, and its biochemical responses were also studied. Results showed that dynamic hormesis of either OTC concentration or cupric ion one on Chlorella vulgaris were confirmed separately, and the presence of OTC not only did not limit biomass growth and lipids content of Chlorella vulgaris but also could mitigate the toxicity of cupric ion on Chlorella vulgaris in combined stress of Cu2+ and OTC. Extracellular polymeric substances (EPS) of Chlorella vulgaris were used to explain the mechanisms of stress for the first time. The content of proteins and carbohydrates in EPS increased, and the fluorescence spectrum intensity of tightly-bound EPS (TB-EPS) of Chlorella vulgaris decreased with increasing concentration of stress because Cu2+ and OTC may be chelated with proteins of TB-EPS to form non-fluorescent characteristic chelates. The low concentration of Cu2+ (≤1.0 mg/L) could enhance the protein content and promote the activity of superoxide dismutase (SOD) while these parameters were decreased drastically under 2.0 mg/L of Cu2+. The activity of adenosine triphosphatase (ATPase) and glutathione (GSH) enhanced with the increase of OTC concentration under combined stress. This study helps to comprehend the impact mechanisms of stress on Chlorella vulgaris and provides a novel strategy to improve the stability of microalgae systems for wastewater treatment.

A microbiological identification and recovery actions of critical symptoms of anammox image bacteria

Currently, the risks posed by bacteria are becoming increasingly important. It now appears that the cell wall of Anammox image bacteria is very different from what has been generally considered for many years. Not every textbook contains the peptidoglycan on the cell wall of Anammox image bacteria - the sugar-protein chain that strengthens the cells of most bacteria. Most researchers in this Anammox image bacteria diseased identification wanted to find out what gave the Anammox image cell its stability. It used powerful cryo-electron microscopes to examine the bacterial cell wall and find the exact structure of the peptidoglycan. A new algorithm is proposed to discover that Anammox image bacteria contain peptidoglycan, which completes a theory in microbiology. The identification of different diseases is listed, and the proposed model compares the exact results while comparing the parameters like accuracy, precision, recall, and F1-Score. Keywords: Anammox image bacteria, cell wall, cell stability, cryo-electron, microscope images, accuracy, precision, recall, F1-score.

Distribution and dynamics of antibiotic resistance genes in a three-dimensional multifunctional biofilm during greywater treatment

Antibiotic resistance genes (ARGs) have been identified as serious threats to public health. Despite the widespread in various systems, dynamics of ARGs in three-dimensional multifunctional biofilm (3D-MFB) treating greywater are largely undefined. This work tracked the distributions and dynamics of eight target genes (intI1, korB, sul1, sul2, tetM, ermB, bla_CTX-M and qnrS) in a 3D-MFB during greywater treatment. Results showed that hydraulic retention times at 9.0 h achieved the highest linear alkylbenzene sulfonate (LAS) and total nitrogen removal rates at 99.4% and 79.6%, respectively. ARGs presented significant liquid-solid distribution feature, but non-significant with biofilm position. Intracellular ARGs (predominant by intI1, korB, sul1 and sul2) at bottom biofilm were 210- to 4.2 × 10⁴- fold higher than that in cell-free liquid. Extracellular polymeric substances (EPS)-attached LAS showed linear relationship with most of ARGs (R² > 0.90, P < 0.05). Sphingobacteriales, Chlamydiales, Microthrixaceae, SB-1, Cryomorphaceae, Chitinophagaceae, Leadbetterella and Niabella were tightly bound up with target ARGs. Key is that EPS-attached LAS considerably determines the occurrence of ARGs, and microbial taxa play an important role in the dissemination of ARGs in the 3D-MFB.

A review of anammox metabolic response to environmental factors: Characteristics and mechanisms

Anaerobic ammonium oxidation (anammox) is a promising low carbon and economic biological nitrogen removal technology. Considering the anammox technology has been easily restricted by environmental factors in practical engineering applications, therefore, it is necessary to understand the metabolic response characteristics of anammox bacteria to different environmental factors, and then guide the application of the anammox process. This review presented the latest advances of the research progress of the effects of different environmental factors on the metabolic pathway of anammox bacteria. The effects as well as mechanisms of conventional environmental factors and emerging pollutants on the anammox metabolic processes were summarized. Also, the role of quorum sensing (QS) mediating the bacteria growth, gene expression and other metabolic process in the anammox system were also reviewed. Finally, interaction and cross-feeding mechanisms of microbial communities in the anammox system were discussed. This review systematically summarized the variations of metabolic mechanism response to the external environment and cross-feeding interactions in the anammox process, which would provide an in-depth understanding for the anammox metabolic process and a comprehensive guidance for future anammox-related metabolic studies and engineering applications.

Advanced insights on removal of antibiotics by microalgae-bacteria consortia: A state-of-the-art review and emerging prospects

Antibiotics abuse has triggered a growing environmental problem, posing a major threat to both ecosystem and human health. Unfortunately, there are still several shortcomings to current antibiotics removal technologies. Microalgae-bacteria consortia have been shown to be a promising antibiotics treatment technology owing to advantages of high antibiotics removal efficiency, low operational cost, and carbon emission reduction. This review aims to introduce the removal mechanisms, influencing factors, and future research perspectives for using microalgae-bacteria consortia to remove antibiotics. The interaction mechanisms between microalgae and bacteria are comprehensively revealed, and their exclusive advantages have been summarized in a "Trilogy" strategy, including "reinforced physical contact", "upgraded substance utilization along with antibiotics degradation", and "robust biological regulation". What's more, the relationship between different interaction mechanisms is emphatically analyzed. The important influencing factors, including concentration and classes of antibiotics, environmental conditions, and operational parameters, of antibiotics removal were also assessed. Three innovative treatment systems (microalgae-bacteria fuel cells (MBFCs), microalgae-bacteria membrane photobioreactors (MB-MPBRs), and microalgae-bacteria granular sludge (MBGS)) along with three advanced techniques (metabolic engineering, machine learning, and molecular docking and dynamics) are then introduced. In addition, concrete implementing schemes of the above advanced techniques are also provided. Finally, the current challenges and future research directions in using microalgae-bacteria consortia to remove antibiotics have been summarized. Overall, this review addresses the current state of microalgae-bacteria consortia for antibiotics treatment and provides corresponding recommendations for enhancing antibiotics removal efficiency.

Nitrogen contribution and microbial community of size-fractionated anammox sludge in continuous stirred-tank reactors

In this study, the microbial diversity of size-fractionated anammox sludge in a well-mixed system and their contribution to nitrogen transformation were investigated. Results showed that small granules (0.2-1.0 mm) contributed to the major part of the nitrogen removal rate (56 %) due to its largest mixed liquor volatile suspended solids (1240 ± 80 mg·L^-1). However, large granules (>1.0 mm) possessed the highest relative abundances of Ca. Kuenenia stuttgartiensis and specific anammox activity, representing 49.34 % and 24.45 ± 0.01 mg-N·g^-1-mixed liquor volatile suspended solids·h^-1, respectively. The microbial diversity decreased as the increase of granular size, resulting in microbial community shifting to a simpler model. Metagenomic analysis showed that fine sludge might be the potential major for NO/N₂O production in the mature well-mixed system under inorganic conditions. This study provides guidance for the evaluation of nitrogen contribution by anammox size-fractionated sludge and the inhibition of the potential NO/N₂O emission in anammox processes.

Long-term effects of Cu(II) on denitrification in hydrogen-based membrane biofilm reactor: Performance, extracellular polymeric substances and microbial communities

Divalent copper (Cu(II)) frequently coexists with nitrate (NO₃^-) in industrial wastewater and the effect of Cu(II) on the autotrophic denitrification system using H₂ as the electron donor remains unknown. In this study, the hydrogen-based membrane biofilm reactor (H₂-MBfR) was operated continuously over 150 days to explore the effect of Cu(II) on the performance of autotrophic denitrification system and understand the key roles of EPS and microbial community. More than 95% of 20 mg-N/L NO₃^- was removed at 1-5 mg/L Cu(II), and the removal rate of NO₃^--N was stabilized to 82% at 10 mg/L Cu(II) after a short period, while NH₄⁺ and NO₂^- in effluent were hardly detected, indicated that high concentration of Cu(II) did not permanently inhibit the denitrification performance in H₂-MBfR. Colorimetric determination showed that Cu(II) stimulated the secretion of EPS, in which the protein (PN) content was much higher than polysaccharide (PS). The PN/PS ratios increased from 0.93 to 1.99, and the PN was more sensitive to copper invasion. The results of three-dimensional excitation-emission matrix illustrated that tryptophan was the main component of EPS chelating Cu(II) to reduce toxicity. The results of Fourier-transform infrared demonstrated that hydroxyl, carboxyl, and protein amide groups bound and reduced Cu(II). Furthermore, Cu(II) was effectively removed (>80%), and the results of distribution and morphology analysis of Cu(II) show that the electron-dense deposits of monovalent copper (Cu(I)) were found in EPS and biofilms and the reduction of Cu(II) to Cu(I) was an obvious self-defense reaction of biofilm to copper stress. The microbial richness and diversity decreased with the long-term exposure to Cu(II), while the relative abundance of denitrifiers Azospira and Dechloromonas increased. This study provides a scientific basis for the optimal design of treatment system for removal of nitrate and recovery of heavy metals simultaneously.

Inhibition of wastewater pollutants on the anammox process: A review

The anaerobic ammonium oxidation (anammox) process has been recognized as an efficient nitrogen removal technology. However, anammox bacteria are susceptible to surrounding environments and different pollutants, which limits the extensive application of the anammox process worldwide. Numerous researchers investigate the effects of various pollutants on the anammox process or bacteria, and related findings have also been reviewed with the focused on their inhibitory effects on process performance and microbial community. This review systemically summarized the recent advances in the inhibition, mechanism and recovery process of traditional and emerging pollutants on the anammox process over a decade, such as organics, metals, antibiotics, nanoparticles, etc. Generally, low-concentration pollutants exhibited a promotion on the anammox activity, while high-concentration pollutants showed inhibitory effects. The inhibitory threshold concentration of different pollutants varied. The combined effects of multipollutant also attracts more attentions, including synergistic, antagonistic and independent effects. Additionally, remaining problems and research needs are further proposed. This review provides a foundation for future research on the inhibition in anammox process, and promotes the proper operation of anammox processes treating different types of wastewaters.