Performance and mechanism of tetracycline removal by the aerobic nitrate-reducing strain Pseudomonas sp. XS-18 with auto-aggregation

Efficient nitrogen removal by the aerobic denitrifying bacterium Pseudomonas stutzeri RAS-L11 under triple stresses of high alkalinity, high salinity, and tetracycline: From performance to mechanism

Efficient aerobic denitrification bacteria are rarely reported under triple stresses of high alkalinity, high salinity, and tetracycline. Here, strain Pseudomonas stutzeri RAS-L11 was isolated, under the optimal reaction conditions of C/N = 6, sodium acetate as carbon source, and pH 7.0-11.0. Moreover, RAS-L11 showed perfect nitrogen removal performance under dual and triple stresses. Specifically, the mean removal efficiency of total dissolved nitrogen for different medium (nitrate, nitrite, ammonia, nitrate and ammonia, and nitrite and ammonia) reached 92.35 %, 66.85 %, 71.33 %, 89.42 %, and 68.76 % under triple stresses. Nitrogen balance results indicated that biomass nitrogen accounted for a small percentage (4.48 % to 20.79 %). Furthermore, the nitrogen metabolism pathways and tetracycline, salinity, and alkaline tolerance-associated genes were also confirmed. Strain RAS-L11 achieved 42.67-70.72 % NO3--N and 83.72-88.53 % NH4+-N removal efficiencies in both sterilized and actual systems treating pharmaceutical wastewater. Our characterization of the RAS-L11 provides a reference for nitrogen removal of pharmaceutical wastewater.

Impacts of sulfamethoxazole on heterotrophic nitrification-aerobic denitrification bacteria and its response strategies: Insights from physiology to proteomics

The effects of sulfonamide antibiotics on heterotrophic nitrification-aerobic denitrification (HN-AD) and the response mechanisms of HN-AD bacteria are not fully understood. This study investigated the physiological changes and proteomic responses of the HN-AD bacteria Pseudomonas stutzeri (P. stutzeri) under varying concentrations of sulfamethoxazole (SMX). Results indicated that SMX inhibited the growth and HN-AD performance of P. stutzeri in a concentration-dependent manner. SMX exposure led to decreased motility, reduced electron transfer system activity, and diminished activities of key denitrifying enzymes, accompanied by increased levels of intracellular reactive oxygen species and compromised cell membrane integrity. Additionally, the production of extracellular polymeric substances and self-aggregation ability of P. stutzeri initially increased and then decreased with rising SMX concentrations. Proteomic analysis revealed that SMX primarily suppressed pathways involved in bacterial chemotaxis, ABC transporters, two-component systems, fatty acid metabolism, and nitrogen metabolism. In response, P. stutzeri upregulated pathways associated with starch and sucrose metabolism, carotenoid biosynthesis, styrene degradation, O-antigen nucleotide sugar biosynthesis, and the pentose phosphate pathway. These findings provide insights into the effects of sulfonamide antibiotics on HN-AD bacteria and their response mechanisms, offering references for the application of HN-AD processes in treating antibiotic-containing wastewater.

The denitrification ability and nitrogen metabolism pathway of aerobic denitrifier Marinobacter alkaliphilus SBY-1 under low C/N ratios

Mariculture tail water is characterized as the low C/N ratios and thus blocks the conventional heterotrophic denitrification process due to insufficient carbon source. Therefore, oligotrophic marine bacteria with heterotrophic nitrification and aerobic denitrification (HN-AD) are urgently required to bioaugment aerobic biological filter. In this study, Marinobacter alkaliphilus SBY-1 was isolated and confirmed optimal nitrate removal capacity at a rate of 716 mg/L·d without ammonia production or nitrite accumulation under initial nitrate concentration of 800 mg/L, pH 7, salinity 20 ‰, sodium acetate as the carbon source, and low C/N ratios of 3.6. SBY-1 also demonstrated heterotrophic nitrification capability with a maximum ammonia removal rate reaching 69.21 % when ammonia was used as the nitrogen source. The enzymes involved in the HN-AD process including ammonia monooxygenase (AMO), nitrate reductase (NR), and nitrite reductase (NIR) were all detected in SBY-1 with superior activity observed for NR and NIR. Additionally, analysis of EPS and auto-aggregation revealed that SBY-1 exhibited excellent auto-aggregation ability under high influent nitrogen concentration conditions, making it more suitable for biofilm formation and further application in biofilm-based denitrification process. Genome analysis identified genes associated with Nar, Nap, Nas, Nir, Nif, Nrt, Nrf, Nor, Nos which confirmed that SBY-1 possessed a complete HN-AD pathway for nitrogen metabolism. The predicted nitrogen metabolism pathway of SBY-1 was NO3--N → NO2--N → NO→N2O → N2. These findings provide new insights into the efficient removal of nitrate by SBY-1 under lower C/N conditions.

Mechanisms of inhibition and recovery under multi-antibiotic stress in anammox: A critical review

With the escalating global concern for emerging pollutants, particularly antibiotics, microplastics, and nanomaterials, the potential disruption they pose to critical environmental processes like anaerobic ammonia oxidation (anammox) has become a pressing issue. The anammox process, which plays a crucial role in nitrogen removal from wastewater, is particularly sensitive to external pollutants. This paper endeavors to address this knowledge gap by providing a comprehensive overview of the inhibition mechanisms of multi-antibiotic on anaerobic ammonia-oxidizing bacteria, along with insights into their recovery processes. The paper dives deeply into the various ways antibiotics interact with anammox bacteria, focusing specifically on their interference with the bacteria's extracellular polymers (EPS) - crucial components that maintain the structural integrity and functionality of the cells. Additionally, it explores how anammox bacteria utilize quorum sensing (QS) mechanisms to regulate their community structure and respond to antibiotic stress. Moreover, the paper summarizes effective removal methods for these antibiotics from wastewater systems, which is crucial for mitigating their inhibitory effects on anammox bacteria. Finally, the paper offers valuable insights into how anammox communities can recuperate from multi-antibiotic stress. This includes strategies for reintroducing healthy bacteria, optimizing operational conditions, and using bioaugmentation techniques to enhance the resilience of anammox communities. In summary, this paper not only enriches our understanding of the complex interactions between antibiotics and anammox bacteria but also provides theoretical and practical guidance for the treatment of antibiotic pollution in sewage, ensuring the sustainability and effectiveness of wastewater treatment processes.

Unraveling the effects and mechanisms of antibiotics on aerobic simultaneous nitrogen and phosphorus removal by Acinetobacter indicus CZH-5

The effects of antibiotics, such as tetracycline, sulfamethoxazole, and ciprofloxacin, on functional microorganisms are of significant concern in wastewater treatment. This study observed that Acinetobacter indicus CZH-5 has a limited capacity to remove nitrogen and phosphorus using antibiotics (5 mg/L) as the sole carbon source. When sodium acetate was supplied (carbon/nitrogen ratio = 7), the average removal efficiencies of ammonia-N, total nitrogen, and orthophosphate-P increased to 52.46 %, 51.95 %, and 92.43 %, respectively. The average removal efficiencies of antibiotics were 84.85 % for tetracycline, 39.32 % for sulfamethoxazole, 18.85 % for ciprofloxacin, and 23.24 % for their mixtures. Increasing the carbon/nitrogen ratio to 20 further improved the average removal efficiencies to 72.61 % for total nitrogen and 97.62 % for orthophosphate-P (5 mg/L antibiotics). Additionally, the growth rate and pollutant removal by CZH-5 were unaffected by the presence of 0.1-1 mg/L antibiotics. Transcriptomic analysis revealed that the promoted translation of aceE, aarA, and gltA genes provided ATP and proton -motive forces. The nitrogen metabolism and polyphosphate genes were also affected. The expression of acetate kinase, dehydrogenase, flavin mononucleotide enzymes, and cytochrome P450 contributed to antibiotic degradation. Intermediate metabolites were investigated to determine the reaction pathways.

Biotransformation characteristics of tetracycline by strain Serratia marcescens MSM2304 and its mechanism evaluation based on products analysis and genomics

Microbial biotransformation is a recommended and reliable method in face of formidable tetracycline (TC) with broad-spectrum antibacterial activity. Herein, comprehensive characteristics of a newfound strain and its molecular mechanism in process of TC bioremediation were involved in this study. Specifically, Serratia marcescens MSM2304 isolated from pig manure sludge grew well in presence of TC and achieved optimal removal efficiency of 61% under conditions of initial TC concentration of 10 mg/L, pH of 7.0, cell inoculation amount of 5%, and tryptone of 10 g/L as additional carbon. The pathways of biotransformation include EPS biosorption, cell surface biosorption and biodegradation, which enzymatic processes of biodegradation were occurred through TC adsorbed by biofilms was firstly broken down by extracellular enzymes and part of TC migrated towards biofilm interior and degraded by intracellular enzymes. Wherein extracellular polysaccharides in extracellular polymeric substances (EPS) from biofilm of strain MSM2304 mainly performed extracellular adsorption, and changes in position and intensity of CO, =CH and C-O-C/C-O of EPS possible further implied TC adsorption by it. Biodegradation accounting for 79.07% played a key role in TC biotransformation and could be fitted well by first-order model that manifesting rapid and thorough removal. Potential biodegradation pathway including demethylation, dihydroxylation, oxygenation, and ring opening possibly involved in TC disposal process of MSM2304, TC-degrading metabolites exhibited lower toxicity to indicator bacteria relative to parent TC. Whole genome sequencing as underlying molecular evidence revealed that TC resistance genes, dehydrogenases-encoding genes, monooxygenase-encoding genes, and methyltransferase-encoding genes of strain MSM2304 were positively related to TC biodegradation. Collectively, these results favored a theoretical evaluation for Serratia marcescens MSM2304 as a promising TC-control agent in environmental bioremediation processes.

Removal of nitrate nitrogen by Pseudomonas JI-2 under strong alkaline conditions: Performance and mechanism

The nitrate nitrogen removal characteristics of Pseudomonas JI-2 under strong alkaline conditions and the composition and functional groups of extracellular polymeric substance were analyzed. Furthermore, nontargeted metabonomics and bioinformatics technology were used to investigate the alkaline tolerance mechanism. JI-2 removed 11.05 mg N/(L·h) of nitrate with the initial pH, carbon to nitrogen ratio and temperature were 11.0, 8 and 25 °C respectively. Even when the pH was maintained at 11.0, JI-2 could still effectively remove nitrate. JI-2 contains a large number of Na+/H+ antiporters, such as Mrp, Mnh (mnhACDEFG) and Pha (phaACDEFG), which can stabilize the intracellular acid-base environment, and SlpA can enable quick adaptation to alkaline conditions. Moreover, JI-2 responds to the strong alkaline environment by secreting more polysaccharides, acidic functional groups and compatible solutes and regulating key metabolic processes such as pantothenate and CoA biosynthesis and carbapenem biosynthesis. Therefore, JI-2 can survive in strong alkaline environments and remove nitrate efficiently.

The performance and mechanism of tetracycline and ammonium removal by Pseudomonas sp. DX-21

To remove ammonium and tetracycline (TC) from wastewater, a new strain, DX-21, was isolated and exhibited simultaneous removal ability. The performance of DX-21 in TC removal, its removal mechanism, and the potential toxicities of the degradation products were investigated with genomics, mass spectrometry, density functional theory calculations, quantitative structure-activity relationship analyses, and Escherichia coli exposure experiments. DX-21 exhibited removal of ammonium (9.64 mg·L-1·h-1) via assimilation, and TC removal (0.85 mg·L-1·h-1) primarily occurred through cell surface bio-adsorption and biodegradation. Among the 12 identified degradation products, the majority exhibited lower toxicities than TC. Moreover, potential degradation pathways were proposed, including hydroxylation and deamination. Furthermore, DX-21 possessed TC resistance genes, various oxygenases and peroxidases that could potentially contribute to TC degradation. DX-21 colonized activated sludge and significantly enhanced the biodegradation of TC. Therefore, DX-21 showed potential for treating wastewater containing both ammonium and TC.

Performance and mechanism of nitrate removal by the aerobic denitrifying bacterium JI-2 with a strong autoaggregation capacity

Here, a new strain JI-2 of the strongly autoaggregating aerobic denitrifying bacteria was screened. The nitrate removal ability and autoaggregation mechanism of JI-2 were analyzed using the nitrogen balance and genomics technology. The nitrate removal rate was 27.05 mg N/(L·h) at pH 9.0 and C/N 8.0. The strain JI-2 removes nitrate via the aerobic denitrification and dissimilation pathways and removes ammonium via the assimilation pathway. 66.81 % nitrate was converted to cellular components under aerobic conditions. Complex nitrogen metabolism genes were detected in strain JI-2. C-di-GMP mediates the motility behavior of JI-2 by binding the FleQ and PilZ proteins, and regulating the expression of PslA. Furthermore, the mechanism of autoaggregation was verified by extracellular polymeric substance analysis. Meanwhile, the nitrate removal rates of strain JI-2 was 11.13-12.50 mg N/(L·h) in wastewater. Thus, strain JI-2 has good prospects for application in the treatment of nitrate wastewater.