The fate of antibiotic resistance genes and their potential hosts during bio-electrochemical treatment of high-salinity pharmaceutical wastewater

Antibiotic resistance genes risks in relation to host pathogenicity and mobility in a typical hospital wastewater treatment process

Hospital wastewaters (HWWs) serve as critical reservoirs for disseminating antibiotic resistance genes (ARGs) and antibiotic resistant bacteria (ARB). However, the dynamics and noteworthy shifts of ARGs and their associated pathogenicity, mobility, and resistome risks during HWWs treatment processes remain poorly understood. Utilizing metagenomic sequencing and assembly, we identified 817 ARG subtypes conferring resistance to 20 classes of antibiotics across 18 HWW samples from influent to effluent. Genes encoding resistance to multidrug, aminoglycoside and beta_lactam were the most prevalent ARG types, reflecting patterns observed in clinical settings. On-site treatment efforts decreased the relative abundance of ARGs by 77.4% from influent to secondary sedimentation, whereas chlorine disinfection significantly increased their abundance in the final effluent. Deterministic processes primarily drove the taxonomic assembly, with Proteobacteria being the most abundant phylum and serving as the primary host for 15 ARG types. Contig-based analysis further revealed 114 pathogenic ARB, with Escherichia coli, Pseudomonas alcaligenes, and Pseudomonas aeruginosa exhibiting multidrug-resistant. The contributions of host bacteria and pathogenic ARB varied throughout wastewater treatment. In addition, 7.10%-31.0 % ARGs were flanked by mobile genetic elements (MGEs), predominantly mediated by transposase (74.1%). Notably, tnpA exhibited the highest potential for ARG dissemination, frequently co-occurring with beta-lactam resistance genes (35.2%). Considering ARG profiles, pathogenic hosts, and transferability, raw influent exhibited the highest antibiotic resistome risk index (ARRI), followed by the final effluent. Chlorine disinfection exacerbated resistome risks by inducing potential pathogenic ARB and mobile ARGs, posing threats to the receiving environment. This study delineates ARG occurrence patterns, highlights mechanisms of ARG carriage and horizontal gene transfer, and provides insights for assessing resistance risks and prioritizing interventions in clinical settings.

Fate and mitigation of antibiotics and antibiotic resistance genes in microbial fuel cell and coupled systems

Microbial fuel cells (MFCs), known for their low energy consumption, high efficiency, and environmental friendliness, have been widely utilized for removing antibiotics from wastewater. Compared to conventional wastewater treatment methods, MFCs produce less sludge while exhibiting superior antibiotic removal capacity, effectively reducing the spread of antibiotic resistance genes (ARGs). This study investigates 1) the mechanisms of ARGs generation and proliferation in MFCs; 2) the influencing factors on the fate and removal of antibiotics and ARGs; and 3) the fate and mitigation of ARGs in MFC and MFC-coupled systems. It is indicated that high removal efficiency of antibiotics and minimal amount of sludge production contribute the mitigation of ARGs in MFCs. Influencing factors, such as cathode potential, electrode materials, salinity, initial antibiotic concentration, and additional additives, can lead to the selection of tolerant microbial communities, thereby affecting the abundance of ARGs carried by various microbial hosts. Integrating MFCs with other wastewater treatment systems can synergistically enhance their performance, thereby improving the overall removal efficiency of ARGs. Moreover, challenges and future directions for mitigating the spread of ARGs using MFCs are suggested.

Deciphering the reduction of antibiotic resistance genes (ARGs) during medium-chain fatty acids production from waste activated sludge: Driven by inhibition of ARGs transmission and shift of microbial community

Medium-chain fatty acids (MCFAs) production from waste activated sludge (WAS) by chain extension (CE) is a promising technology. However, the effects and mechanisms of CE process on the fate of antibiotic resistance genes (ARGs) remain unclear. In this study, the results showed that the removal efficiency of ARGs was 81.15 % in CE process, suggesting its efficacy in reducing environmental risks. Further, the observed decrease in mobile genetic elements (MGEs) indicated that CE process restricted the horizontal gene transfer (HGT). Complementing this, the increase in soluble organic matters and extracellular 16 S rDNA confirmed that MCFAs production caused bacterial damage. Decreased intracellular ARGs and increased extracellular ARGs further revealed that MCFAs production impaired ARGs hosts, thereby limiting the vertical gene transfer (VGT) of ARGs. Shift of microbial community combined with co-occurrence network analysis demonstrated that functional bacteria without host potential for ARGs were enriched, but potential ARGs and MGEs hosts decreased, showing the role of functional bacterial phylogeny and selection pressure of MCFAs in reducing ARGs. Finally, partial least squares path model was used to systematic verify the mechanism of ARGs removal in CE process, which was attributed to the inhibition of ARGs transmission (HGT and VGT) and shift of microbial community.

Recovery mechanism of heterotrophic ammonia assimilation system under chromium hexavalent stress

Heterotrophic ammonia assimilation (HAA), an innovative technology for high-salinity wastewater treatment, demonstrates self-recovery capability following Cr (VI) stress. This study investigated the inhibitory effects and self-restoration mechanisms of Cr (VI) at various stress levels. The removal efficiencies of NH4+-N and Cr (VI) in the HAA gradually decreased with increasing influent Cr (VI) concentration. Exposure to Cr (VI) increased the amounts of high-molecular-weight proteins in soluble microbial products and stimulated the generation of extracellular polymeric substances. Heterotrophic functional microorganisms with Cr (VI) tolerance, such as Marinobacter and Planktosalinus, were enriched. An assimilation pathway gene (glnA) and a Cr (VI)-related gene (atoB) were also upregulated. After ceasing Cr (VI) addition, the HAA system demonstrated a 17.1 % increase in the removal efficiency of NH4+-N, which was attributable to its self-recovery ability. This study provides a scientific and theoretical foundation for the HAA process in resisting the impact of heavy-metal-containing wastewater and self-recovery.

Insights into microbial contamination and antibiotic resistome traits in pork wholesale market: An evaluation of the disinfection effect of sodium hypochlorite

Chlorine and its derivatives, such as sodium hypochlorite (NaClO) and chlorine dioxide, are frequently employed as disinfectants throughout the pork supply chain in China. Nevertheless, the extensive use of NaClO has the potential to cause the creation of 'chlorine-tolerant bacteria' and accelerate the evolution of antibiotic resistance. This study evaluated the efficacy of NaClO disinfection by examining alterations in the microbiome and resistome of a pork wholesale market (PWM), and bacteria isolation and analysis were performed to validate the findings. As expected, the taxonomic compositions of bacteria was significantly different before and after disinfection. Notably, Salmonella enterica (S. enterica), Salmonella bongori (S. bongori), Escherichia coli (E. coli), Klebsiella pneumoniae (K. pneumoniae), and Pseudomonas aeruginosa (P. aeruginosa) were observed on all surfaces, indicating that the application of NaClO disinfection treatment in PWM environments for pathogenic bacteria is limited. Correlations were identified between antibiotic resistance genes (ARGs) associated with aminoglycosides (aph(3'')-I, aph(6')-I), quinolone (qnrB, abaQ), polymyxin (arnA, mcr-4) and disinfectant resistance genes (emrA/BD, mdtA/B/C/E/F). Furthermore, correlations were found between risk Rank I ARGs associated with aminoglycoside (aph(3')-I), tetracycline (tetH), beta_lactam (TEM-171), and disinfectant resistance genes (mdtB/C/E/F, emrA, acrB, qacG). Importantly, we found that Acinetobacter and Salmonella were the main hosts of disinfectant resistance genes. The resistance mechanisms of the ARGs identified in PWM were dominated by antibiotic deactivation (38.7%), antibiotic efflux (27.2%), and antibiotic target protection (14.4%). The proportion of genes encoding efflux pumps in the PWM resistome increased after disinfection. Microbial cultures demonstrated that the traits of microbial contamination and antibiotic resistane were consistent with those observed by metagenomic sequencing. This study highlights the possibility of cross-resistance between NaClO disinfectants and antibiotics, which should not be ignored.

Source apportionment and predictable driving factors contribute to antibiotics profiles in Changshou Lake of the Three Gorges Reservoir area, China

Lakes, crucial antibiotic reservoirs, lack thorough exploration of quantitative relationships between antibiotics and influencing factors. Here, we conducted a comprehensive year-long investigation in Changshou Lake within the Three Gorges Reservoir area, China. The concentrations of 21 antibiotics spanned 35.6-200 ng/L, 50.3-348 ng/L and 0.57-57.9 ng/g in surface water, overlying water and sediment, respectively. Compared with abundant water period, surface water and overlying water displayed significantly high antibiotic concentrations in flat and low water periods, while sediment remained unchanged. Moreover, tetracyclines, fluoroquinolones and erythromycin posed notable risks to algae. Six primary sources were identified using positive matrix factorization model, with aquaculture contributing 21.2%, 22.7% and 25.4% in surface water, overlying water and sediment, respectively. The crucial predictors were screened through machine learning, redundancy analysis and Mantel test. Our findings emphasized the pivotal roles of water quality parameters, including water temperature (WT), pH, dissolved oxygen, electrical conductivity, inorganic anions (NO3⁻, Cl⁻ and F⁻) and metal cations (Ca, Mg, Fe, K and Cr), with WT influencing greatest. Total nitrogen (TN), cation exchange capacity, K, Al and Cd significantly impacted sediment antibiotics, with TN having the most pronounced effect. This study can promise valuable insights for environmental planning and policies addressing antibiotic pollution.

Enhanced metronidazole removal in seawater using a single-chamber bioelectrochemical system

The aim of this study was to investigate the removal of metronidazole (MNZ) from seawater using a bioelectrochemical system (BES). Single-chamber BES (i.e., S-BES) and dual-chamber BES (i.e., D-BES) were constructed with carbon brush as the anode and cathode. With the inoculum of sea mud and 2 g/L of glucose as the substrate in seawater, S-BES and D-BES were acclimated to test the MNZ removal. Results showed that S-BES could remove almost 100 % of 200 mg/L MNZ within 120 h and remain stable within 10 cycles of operation (∼50 d) under the applied voltage of 0.8 V. The MNZ removal reached ∼100 % and 60.2 % in the cathodic and anodic chambers of D-BES fed by 100 mg/L MNZ under 0.8 V, respectively. The MNZ concentration of 200 mg/L significantly inhibited the sulfur metabolism, decreased the ratio of live to dead cells in the electrode biofilms, and thus reduced the SO42- removal in the S-BES. The MNZ degradation and S2- oxidation was mainly attributed to the cathodic and anodic biofilms of S-BES, respectively. Three degradation pathways of MNZ were proposed based on the identified intermediates and results of density functional theory calculations. The synergies among different genus species in the bacterial communities of biofilms, and between anodic and cathodic reactions could be responsible for the high performance of S-BES. Results from this study should be not only useful for the MNZ removal but also for effective MNZ inhibition of sulfate-reducing bacteria induced microbiologically influenced corrosion in seawater.

Synergistic Control of Trimethoprim and the Antimicrobial Resistome in Electrogenic Microbial Communities

Synergistic control of the risks posed by emerging antimicrobials and antibiotic resistance genes (ARGs) is crucial for ensuring ecological safety. Although electrogenic respiration can enhance the biodegradation of several antimicrobials and reduce ARGs accumulation, the association mechanisms of antimicrobial biodegradation (trimethoprim, TMP) with the fate of the antimicrobial resistome remain unclear. Here, the biotransformation pathway of TMP, microbial associations, and functional gene profiles (e.g., degradation, antimicrobial resistance, and electron transfer) were analyzed. The results showed that the microbial electrogenic respiration significantly enhanced the biodegradation of TMP, especially with a cosubstrate sodium acetate supply. Electroactive bacteria enriched in the electrode biofilm positively correlated with potential TMP degraders dominated in the planktonic communities. These cross-niche microbial associations may contribute to the accelerated catabolism of TMP and extracellular electron transfer. Importantly, the evolution and dissemination of overall ARGs and mobile genetic elements (MGEs) were significantly weakened due to the enhanced cometabolic biodegradation of TMP. This study provides a promising strategy for the synergistic control of the water ecological risks of antimicrobials and their resistome, while also highlighting new insights into the association of antimicrobial biodegradation with the evolution of the resistome in an electrically integrated biological process.

Impact of salinity on anaerobic ceramic membrane bioreactor for textile wastewater treatment: Process performance, membrane fouling and machine learning models

Anaerobic membrane bioreactor (AnMBR) shows great potential for textile wastewater treatment, but high salinity in the influent may undermine its performance. This study evaluated the impact of salinity on the treatment performance of an upflow anaerobic sludge blanket (UASB) configured AnMBR using a flat sheet ceramic membrane. The salinity was stepwise increased (0, 5, 10 and 20 g/L) in four phases of the AnMBR operation. Results indicated that increased salinity jeopardized the COD removal efficiency of AnMBR from 92% to 73%, but had a marginal effect on dye removal efficacy (90-96%). Low salinity (5 g/L) boosted the biogas production whilst high salinity (>10 g/L) had a negative impact. Additionally, the increase of salinity resulted in the soluble microbial production (SMP) concentration soar and membrane fouling rate increase, peaking at a salinity of 10 g/L (Phase III) and recovering back to a lower level at a salinity of 20 g/L (Phase IV). This indicated a transition occurrence at a salinity of 10 g/L (Phase III). The microbial diversity analyses further suggested a transition from salinity-sensitive microbes (Aminiphilus, Caldatribacterium, Mesotoga, Methanobrevibacter, Methanobacterium, Methanosaeta) to salinity-tolerant microbes (Longilinea, Ignavibacterium, Rhodovarius, Bosea and Flexilinea). This transition can be associated with the increase SMP concentration and more severe membrane fouling in Phase III, which were mitigated after a new equilibrium was reached when the microbial consortium acclimatized to the high salinity. Finally, a machine learning model of the Adaboost algorithm was established to predict COD removal under different salinities. Importantly, this study revealed that AnMBR process performance and membrane operation can be maintained for high salinity textile wastewater treatment with a halophilic microbial community growth under high-salinity selection pressure.

Evolution of aniline degradation and nitrogen removal performance in electro-enhanced sequence batch reactor under salinity stress: Sludge characteristics and microbial diversity

To explore the influence mechanism of different concentrations of salinity on the electro-enhanced aniline biodegradation system, a control group and experimental groups (0%-NaCl, 0.5%-NaCl, 1.5%-NaCl, 2.5%-NaCl, 3.5%-NaCl) were established. The experimental results showed that the electric field strengthened the denitrification performance, while salinity had little effect on the degradation efficiency of aniline and chemical oxygen demand (COD). The removal rate of TN reached 79.6% and 74.9% in 0.5%-NaCl and 1.5%-NaCl, respectively, which were superior than 0%-NaCl. As salinity increased, the nitrogen removal effect was negatively affected. Microbial diversity analysis indicated that the microbial community structure was uniform in the control group, 0%-NaCl, and 0.5%-NaCl, with the dominant genus OLB8 ensuring the nitrogen removal performance. In contrast, in the 2.5%-NaCl and 3.5%-NaCl experimental groups, the organic degrading bacteria were still active, while nitrifiers and denitrifiers were severely damaged. In conclusion, this study suggested that low concentrations of salinity can improve the decontamination performance of the electro-enhanced aniline biodegradation system, while high concentrations of salinity could lead to the collapse of the decontamination mechanism.

Characterizing sediment functional traits and ecological consequences respond to increasing antibiotic pollution

Current studies have shown that the taxonomic structures of ecologically important microbial communities are altered by antibiotic exposure, but the resulting effects on functional potentials and subsequent biogeochemical processes are poorly understood. However, this knowledge is indispensable for developing an accurate projection of nutrient dynamics in the future. Using metagenomic analyses, here we explored the responses of taxonomical and functional structures of a sediment microbial community, and their links with key biogeochemical processes to increasing antibiotic pollution from the pristine inlet to the outfall sites along an aquaculture discharge channel. We identified sharply contrasting sedimentary microbial communities and functional traits along increasing antibiotic pollution. Functional structures exhibited steeper distance-decay relationships than taxonomical structures along both the antibiotic distance and physicochemical distance, revealing higher functional sensitivity. Sediment enzyme activities were significantly and positively coupled with the relative abundances of their coding genes, thus the abundances of genes were indicative of functional potentials. The nitrogen cycling pathways were commonly inhibited by antibiotics, but not for the first step of nitrification, which could synergistically mitigate nitrous oxide emission. However, antibiotic pollution stimulated methanogens and inhibited methanotrophs, thereby promoting methane efflux. Furthermore, microbes could adapt to antibiotic pollution through enriched potential of sulfate uptake. Antibiotics indirectly affected taxonomic structures through alterations in network topological features, which in turn affected sediment functional structures and biogeochemical processes. Notably, only 13 antibiotics concentration-discriminatory genes contributed an overall 95.9% accuracy in diagnosing in situ antibiotic concentrations, in which just two indicators were antibiotic resistance genes. Our study comprehensively integrates sediment compositional and functional traits, biotic interactions, and enzymatic activities, thus generating a better understanding about ecological consequences of increasing antibiotics pollution. KEY POINTS: • Contrasting functional traits respond to increasing antibiotic pollution. • Antibiotics pollution stimulates CH₄ efflux, while mitigating N₂O emission and may drive an adaptive response of enriched sulfate uptake. • Indicator genes contribute 95.9% accuracy in diagnosing antibiotic concentrations.

Removal of chloramphenicol and resistance gene changes in electric-integrated vertical flow constructed wetlands

The performance of an electric-integrated vertical flow constructed wetland (E-VFCW) for chloramphenicol (CAP) removal, changes in microbial community structure, and the fate of antibiotic resistance genes (ARGs) were evaluated. CAP removal in the E-VFCW system was 92.73% ± 0.78% (planted) and 90.80% ± 0.61% (unplanted), both were higher than the control system which was 68.17% ± 1.27%. The contribution of anaerobic cathodic chambers in CAP removal was higher than the aerobic anodic chambers. Plant physiochemical indicators in the reactor revealed electrical stimulation increased oxidase activity. Electrical stimulation enhanced the enrichment of ARGs in the electrode layer of the E-VFCW system (except floR). Plant ARGs and intI1 levels were higher in the E-VFCW than in the control system, suggesting electrical stimulation induces plants to absorb ARGs, reducing ARGs in the wetland. The distribution of intI1 and sul1 genes in plants suggests that horizontal transfer may be the main mechanism dispersing ARGs in plants. High throughput sequencing analysis revealed electrical stimulation selectively enriched CAP degrading functional bacteria (Geobacter and Trichlorobacter). Quantitative correlation analysis between bacterial communities and ARGs confirmed the abundance of ARGs relates to the distribution of potential hosts and mobile genetic elements (intI1). E-VFCW is effective in treating antibiotic wastewater, however ARGs potentially accumulate.

Spatial distribution of airborne bacterial communities in caged poultry houses

Microbial aerosols in intensive broiler houses whose species and concentrations are closely related to human health are ubiquitous. Based on 16S rRNA gene sequencing, the aim of this study was to investigate the spatial distribution and diversity of bacterial aerosols in the air of broiler houses. Significant spatial variations in airborne bacterial concentrations were observed inside the poultry farmhouse. The results indicated that bacteria in the air samples could be grouped into a total of 1,674 OTUs. Alpha diversity analysis showed that the diversity of the microbial community at the entry of the broiler house was higher than that at the middle or the rear (p < 0.01). The Sankey diagram illustrated species dynamic changes in Proteobacteria, Firmicutes, and Actinobacteria among the different locations. From the aspect of LEfSe (LDA Effect Size) analysis, we discovered that the abundance of Planctomycetes was significantly higher in the entry than in the rear and middle. This study shows the spatial distribution of the entire bacterial community in intensive broiler houses, which offers a new perspective for studying airborne total bacteria in those environments.Implications: The bacteria contained in air aerosols from poultry houses are closely connected to animal health and production. This study aimed to investigate the spatial distribution and diversity of bacterial aerosols in the air of broiler houses. The results observed that bacterial aerosol concentrations in the examined broilers house varied greatly at different positions, and a significantly higher exposure to bacterial aerosol was observed at the middle than at the other positions (p < 0.05). The alpha diversity analysis showed that the diversity of the microbial community at the entry of the broiler house was higher than that at the middle or the rear (P<0.01). Sankey diagram illustrated species dynamic changes of Proteobacteria, Firmicutes and Actinobacteria among the different locations. The microbial communities in genus level in the samples of entry and rear were closer, while the species diversity of middle and rear samples in chicken house was highly similar (P>0.05). Altogether, results revealed that the effects of spatial factors on the diversity and abundance of bacteria in the air of closed-cage broiler houses, which poses a potential threat to the health of animals and workers in those environments.

Study on the removal characteristics and degradation pathways of highly toxic and refractory organic pollutants in real pharmaceutical factory wastewater treated by a pilot-scale integrated process

Introduction

Pharmaceutical wastewater frequently contains high levels of toxic pollutants. If they are discharged untreated, they pose a threat to the environment. The traditional activated sludge process and the advanced oxidation process do not sufficiently remove toxic and conventional pollutants from pharmaceutical wastewater treatment plants (PWWTPs).

Methods

We designed a pilot-scale reaction system to reduce toxic organic pollutants and conventional pollutants from pharmaceutical wastewater during the biochemical reaction stage. This system included a continuous stirred tank reactor (CSTR), microbial electrolysis cells (MECs), an expanded sludge bed reactor (EGSB), and a moving bed biofilm reactor (MBBR). We used this system to further investigate the benzothiazole degradation pathway.

Results and discussion

The system effectively degraded the toxic pollutants (benzothiazole, pyridine, indole, and quinoline) and the conventional chemicals (COD, NH4+-N, TN). During the stable operation of the pilot-scale plant, the total removal rates of benzothiazole, indole, pyridine, and quinoline were 97.66, 94.13, 79.69, and 81.34%, respectively. The CSTR and MECs contributed the most to the removal of toxic pollutants, while the EGSB and MBBR contributed less to the removal of the four toxic pollutants. Benzothiazoles can be degraded via two pathways: the benzene ring-opening reaction and the heterocyclic ring-opening reaction. The heterocyclic ring-opening reaction was more important in degrading the benzothiazoles in this study.

Conclusion

This study provides feasible design alternatives for PWWTPs to remove both toxic and conventional pollutants at the same time.

Differential impacts of salinity on antibiotic resistance genes during cattle manure stockpiling are linked to mobility potentials revealed by metagenomic sequencing

Livestock manure is an important source of antibiotic resistance genes (ARGs), and its salinity level can change during stockpiling. To understand how the salinity changes affect the fate of ARGs, cattle manure was adjusted of salinity and stockpiled in laboratory microcosms at low (0.3% salt), moderate (3.0%) and high salinity levels (10.0%) for 44 days. Amongst the five ARGs (tetO, bla_TEM, sul1, tetM, and ermB) and the first-class integrase (intI1) monitored by qPCR, the relative abundance of tetO and bla_TEM exhibited no clear trend in response to salinity levels, while that of sul1, tetM, ermB and intI1 showed clear downward trends over time at the lower salinity levels (0.3% and 3%) but not at the high salinity level (10%). Metagenomic contig construction of cattle manure samples revealed that sul1, tetM and ermB genes were more likely to associate with mobile genetic elements (MGEs) than tetO and bla_TEM, suggesting that their slower decay at higher salinity levels was either caused by horizontal gene transfer or co-selection of ARGs and osmotic stress resistant determinants. Further analysis of metagenomic contigs showed that osmotic stress resistance can also be located on MGEs or in conjunction with ARGs.

Sulfur: a neglected driver of the increased abundance of antibiotic resistance genes in agricultural reclaimed subsidence land located in coal mines with high phreatic water levels

Due to the shallow burial of groundwater in coal mines with a high phreatic water level, a large area of subsidence lakes is formed after the mine collapses. Agricultural and fishery reclamation activities have been carried out, which introduced antibiotics and exacerbated the contamination of antibiotic resistance genes (ARGs), but this has received limited attention. This study analyzed ARG occurrence in reclaimed mining areas, the key impact factors, and the underlying mechanism. The results show that sulfur is the most critical factor impacting the abundance of ARGs in reclaimed soil, which is due to changes in the microbial community. The species and abundance of ARGs in the reclaimed soil were higher than those in the controlled soil. The relative abundances of most ARGs increased with the depth of reclaimed soil (from 0 to 80 cm). In addition, the microbial structures of the reclaimed and controlled soils were significantly different. Proteobacteria, was the most dominant microbial phylum in the reclaimed soil. This difference is likely related to the high abundance of sulfur metabolism functional genes in the reclaimed soil. Correlation analysis showed that the differences in ARGs and microorganisms in the two soil types were highly correlated with the sulfur content. High levels of sulfur promoted the proliferation of sulfur-metabolizing microbial populations such as Proteobacteria and Gemmatimonadetes in the reclaimed soils. Remarkably, these microbial phyla were the main antibiotic-resistant bacteria in this study, and their proliferation created conditions for the enrichment of ARGs. Overall, this study underscores the risk of the abundance and spread of ARGs driven by high-level sulfur in reclaimed soils and reveals the mechanisms.

Leaching risk of antibiotic resistance contamination from organic waste compost in rural areas

Composting is an important decentralized technology for treating multiple biodegradable organic wastes in rural areas. However, compared to industrial composting (i.e., time and temperature protocols), rural composting is less well-controlled, and the risk of antibiotic resistance genes (ARGs) in these composts needs to be determined. We performed a quantitative determination of ARGs and both prokaryotes and eukaryotes to investigate the liquid-solid leaching ratio and the relationship between ARGs and microbial communities in solid and water extracts of composts collected from rural areas. We observed a high level of sulfonamides resistance genes and tetracyclines resistance genes (10^-4-10^-2 copies/16S copies). Tet-C and tet-X show the strongest leaching potential in rural organic waste composts with complex hosts in solid and liquid phases. This study showed high ARG abundances in compost solid and water extracts, highlighting the leaching risk of compost ARGs when exposed to runoff or groundwater during open storage and field application.

Optimization of C50 Carotenoids Production by Open Fermentation of Halorubrum sp. HRM-150

C₅₀ carotenoids, as unique bioactive molecules, have many biological properties, including antioxidant, anticancer, and antibacterial activity, and have a wide range of potential uses in the food, cosmetic, and biomedical industries. The majority of C₅₀ carotenoids are produced by the sterile fermentation of halophilic archaea. This study aims to look at more cost-effective and manageable ways of producing C₅₀ carotenoids. The basic medium, carbon source supplementation, and optimal culture conditions for Halorubrum sp. HRM-150 C₅₀ carotenoids production by open fermentation were examined in this work. The results indicated that Halorubrum sp. HRM-150 grown in natural brine medium grew faster than artificial brine medium. The addition of glucose, sucrose, and lactose (10 g/L) enhanced both biomass and carotenoids productivity, with the highest level reaching 4.53 ± 0.32 μg/mL when glucose was added. According to the findings of orthogonal studies based on the OD₆₀₀ and carotenoids productivity, the best conditions for open fermentation were salinity 20-25%, rotation speed 150-200 rpm, and pH 7.0-8.2. The up-scaled open fermentation was carried out in a 7 L medium under optimum culture conditions. At 96 h, the OD₆₀₀ and carotenoids productivity were 9.86 ± 0.51 (dry weight 10.40 ± 1.27 g/L) and 7.31 ± 0.65 μg/mL (701.40 ± 21.51 μg/g dry weight, respectively). When amplified with both universal bacterial primer and archaeal primer in the open fermentation, Halorubrum remained the dominating species, indicating that contamination was kept within an acceptable level. To summarize, open fermentation of Halorubrum is a promising method for producing C₅₀ carotenoids.

The fate of antibiotic resistance genes and their association with bacterial and archaeal communities during advanced treatment of pig farm wastewater

Advanced wastewater treatment plants are widely used in most large-scale pig farms in southern China. However, the fate of antibiotic resistance genes (ARGs) and their association with bacterial and archaeal communities during advanced wastewater treatment remain unclear. In this study, the profiles of ARGs in typical advanced wastewater treatment plants were surveyed using metagenomic analysis. The results showed that 279- 326 different subtypes of ARGs were detected in raw wastewater, with a total abundance of 5.98 ± 0.48 copies per bacterial cell. During the advanced wastewater treatment, the abundance and number of ARGs were significantly reduced. Microbial communities (bacteria and archaea) contributed the most to the variation in ARG abundance and composition (PCA axis_1), accounting for 10.8 % and 15.7 %, respectively, followed by mobile genetic elements (MGEs) and physicochemical factors. Special attention should be given to potential pathogenic bacteria such as Escherichia, Streptococcus, Enterococcus and Staphylococcus and archaea such as Methanocorpusculum, Candidatus Methanoplasma and Candidatus Methanomethylophilus, which were important potential ARG hosts. Bacterial communities may indirectly affect ARG variation by affecting archaeal communities. These findings indicated that ARG levels in pig farm wastewater can be effectively reduced during advanced treatment and highlighted the important role played by archaea, which should not be ignored.

Exploring the impact of biochar supplement on the dynamics of antibiotic resistant fungi during pig manure composting

The purpose of this study was to investigate antibiotic resistant fungal (ARF) communities in pig manure (PM) composting employing two different biochar (coconut shell-CSB and bamboo biochar-BB) as amendment. Three treatments (Control, 10% CSB and 10% BB) were designed and indicated with T1 to T3. Experimental results declared that the fungal abundance significantly reduced among the both biochar applied treatments but three dominant phyla Ascomycota, Basidiomycota and Mucoromycota were still relatively greater abundance present. There were significant differences (p < 0.05) in the relative abundance and diversity of fungi among all three treatments. Interestingly, biochar addition regulated the overall fungal community in final compost. Compared with the control group, the abundance of fungi was positively mobilized, and especially CSB showed a better effect. Conclusively, biochar has potential to inhibit and reduce the ARGs population and mobility in compost. Thus, these findings offer new insight to understand the succession of ARFs during PM composting.

Source prevention of halogenated antibiotic resistance genes proliferation: UV/sulfite advanced reduction process achieved accurate and efficient elimination of florfenicol antibacterial activity

The production and consumption of halogenated antibiotics, such as florfenicol (FLO), remain high, accompanied by a large amount of antibiotic-containing wastewater, which would induce the potential proliferation and transmission of antibiotic resistance genes (ARGs) in conventional biological systems. This study revealed that the introduction of reductive species (mainly H) by adding sulfite during UV irradiation process accelerated the decomposition rate of FLO, increasing from 0.1379 min^-1 in the single UV photolytic system to 0.3375 min^-1 in the UV/sulfite system. The enhanced photodecomposition in UV/sulfite system was attributed to the improved dehalogenation performance and additional removal of sulfomethyl group at the site of the benzene ring, which were the representative structures consisting of FLO antibacterial activity. Compared with single UV photolysis, UV/sulfite advanced reduction process saved the light energy requirement by 40 % for the evolutionary suppression of floR, and its corresponding class of ARGs in subsequent biotreatment system was controlled at the level of the negative group. Compared with UV/H₂O₂ and UV/persulfate systems, the decomposition rate of FLO in the UV/S system was the highest and preserved the corresponding carbon source of the coexisting organic compounds for the potential utilization of microbial metabolism in subsequent biotreatment process. These results demonstrated that UV/sulfite advanced reduction process could be adopted as a promising pretreatment option for the source prevention of representative ARGs proliferation of halogenated antibiotics in subsequent biotreatment process.

Electroactive Ultrafiltration Membrane for Simultaneous Removal of Antibiotic, Antibiotic Resistant Bacteria, and Antibiotic Resistance Genes from Wastewater Effluent

To combat the spread of antibiotic resistance into the environment, we should adequately manage wastewater effluent treatment to achieve simultaneous removal of antibiotics, antibiotic resistant bacteria (ARB), and antibiotic resistance genes (ARGs). Herein, we fabricate a multifunctional electroactive poly(vinylidene fluoride) ultrafiltration membrane (C/PVDF) by phase inversion on conductive carbon cloth. The membrane possesses not only excellent retention toward ARB and ARGs but also exhibits high oxidation capacity as an electrode. Notably, sulfamethoxazole degradation involving hydroxylation and hydrolysis by the anode membrane is predominant, and the degradation efficiency is up to 81.5% at +4 V. Both electro-filtration processes exhibit significant ARB inactivation, anode filtration is superior to cathode filtration. Moreover, the degradation of intracellular ARGs (iARGs) located in the genome is more efficient than those located in the plasmid, and these degradation efficiencies at -2 V are higher than +2 V. The degradation efficiencies of extracellular ARGs (eARGs) are opposite and are lower than iARGs. Compared with regular filtration, the normalized flux of electroactive ultrafiltration membrane is improved by 18.0% at -2 V, 15.9% at +2 V, and 30.4% at +4 V during treating wastewater effluent, confirming its antifouling properties and feasibility for practical application.

Responses of microbial community and antibiotic resistance genes to co-existence of chloramphenicol and salinity

In recent years, the risk from environmental pollution caused by chloramphenicol (CAP) has emerged as a serious concern worldwide, especially for the co-selection of antibiotic resistance microorganisms simultaneously exposed to CAP and salts. In this study, the multistage contact oxidation reactor (MCOR) was employed for the first time to treat the CAP wastewater under the co-existence of CAP (10-80 mg/L) and salinity (0-30 g/L NaCl). The CAP removal efficiency reached 91.7% under the co-existence of 30 mg/L CAP and 10 g/L NaCl in the influent, but it fluctuated around 60% with the increase of CAP concentration and salinity. Trichococcus and Lactococcus were the major contributors to the CAP and salinity shock loads. Furthermore, the elevated CAP and salinity selection pressures inhibited the spread of CAP efflux pump genes, including cmlA, tetC, and floR, and significantly affected the composition and abundance of antibiotic resistance genes (ARGs). As the potential hosts of CAP resistance genes, Acinetobacter, Enterococcus, and unclassified_d_Bacteria developed resistance against high osmotic pressure and antibiotic environment using the efflux pump mechanism. The results also revealed that shifting of potential host bacteria significantly contributed to the change in ARGs. Overall, the co-existence of CAP and salinity promoted the enrichment of core genera Trichococcus and Lactococcus; however, they inhibited the proliferation of ARGs. KEY POINTS: • Trichococcus and Lactococcus were the core bacteria related to CAP biodegradation • Co-existence of CAP and salinity inhibited proliferation of cmlA, tetC, and floR • The microorganism resisted the CAP using the efflux pump mechanism.

Anaerobic electrochemical membrane bioreactor effectively mitigates antibiotic resistance genes proliferation under high antibiotic selection pressure

The spread of antibiotics and antibiotic resistance genes (ARGs) in environments has posed potential threats to public health. Unfortunately, conventional biological wastewater treatment technologies generally show insufficient removal of antibiotics and ARGs. Bioelectrochemical systems, which can effectively degrade refractory organic pollutants via enhancing microbial metabolisms through electrochemical redox reaction, may provide an alternative for the control of antibiotics and ARGs. Herein, an anaerobic electrochemical membrane bioreactor (AnEMBR) was conducted by combining bioelectrochemical system and anaerobic membrane bioreactor to treat antibiotic-containing wastewater. The AnEMBR at open circuit showed stable CH4 production and high removal of COD and chlortetracycline (CTC) in treating 2.5-15 mg/L CTC. However, increasing CTC to 45 mg/L completely inhibited the methanogenesis of AnEMBR at open circuit. After applying external voltage in AnEMBR, the performances of AnEMBR were significantly improved (e.g., increased CH4 production and CTC removal). Moreover, CTC exposure significantly increased the relative abundances of ARGs in sludge, supernatant, and effluent in AnEMBR at open circuit. Applying voltage greatly attenuated the total relative abundances of ARGs in the supernatant and effluent of AnEMBR compared to those at open circuit. This could be attributed to the enrichment of tetracycline degradation gene tetX, which greatly enhanced the removal of CTC by the AnEMBR and thus reduced the selective pressure of CTC on the microorganisms in supernatant and effluent for ARGs proliferation. These results would provide an effective wastewater treatment technology for treating high-level antibiotic-containing wastewater to mitigate the potential risk of ARGs and antibiotics spread in receiving water body.

Effects of ammonia on electrochemical active biofilm in microbial electrolysis cells for synthetic swine wastewater treatment

When facing wastewater with high organic and ammonia, e. g. swine wastewater, microbial electrolysis cell (MEC) is emerging for energy extraction as hydrogen and methane. However, the effects of highly concentrated ammonia on MEC haven't been fully evaluated. In this study, single-chamber MECs were operated with acetate and sucrose as substrates under various ammonia concentrations. The current generally increased with ammonia loading from 80 to 3000 mg L^-1. Yet, the substrate consumption in MECs was inhibited with ammonia concentrations above 1000 mg L^-1. As a combined result, the energy recovery efficiency of MECs was stable. The electrochemical activity of anode biofilm reached the peak under 1000 mg L^-1 ammonia and was restricted under higher ammonia loadings. Under neutral pH, the NH₄⁺ increases the cell membrane permeability, which benefited the electrochemical activity of exoelectrogens to a proper extent. Nevertheless, the toxic ammonia also accelerated the anode biomass loss and stimulated the extracellular polymeric substance (EPS) secretion. Due to the current increase, the abundance of exoelectrogens generally raised with ammonia loading from 80 to 3000 mg L^-1. However, except for anode biomass loss, the carbon and methane metabolism pathways were inhibited in acetate-fed MEC, while the glycolysis acted as the rate-limiting step for substrate degradation in sucrose-fed conditions. This study systematically examined the influences of high ammonia loading on MEC performances, bio-community and anode electrochemical activities, and evaluated practical feasibility and application inch of MECs for the energy recovery and pollutant removal of high concentration organic and ammonia wastewater.

(Micro) nanoplastics promote the risk of antibiotic resistance gene propagation in biological phosphorus removal system

Microplastics (MPs), nanoplastics (NPs) and antibiotic resistance genes (ARGs), as emerging pollutants, have been frequently detected in wastewater treatment plants. However, the behavior of phosphorus and ARGs under MP and NP (MP/NP) pressure in biological phosphorus removal (BPR) system is still unknown. This study investigated the effects of MP/NPs on phosphorus removal and ARGs propagation in BPR system. Results showed that MP/NPs had no influence on phosphorus removal, but significantly promoted the amplification of tetracycline resistance genes (TRGs). Moreover, the TRG abundance were more facilitated by MPs than NPs, and the TRGs of efflux pump and enzymatic modification mechanism were mainly enriched. Meanwhile, MP/NPs increased the transmission risk of multiple resistance genes and mobile gene elements (MGEs). Microbial communities demonstrated the main polyphosphate accumulating organisms shifted from Acinetobacter to unclassified_Gammaproteobacteria, which explained why phosphorus removal efficiency was unaffected with MP/NP addition. Correlation analysis revealed there was no significant correlation between ARGs and MGEs (intI1 and intI2), but the abundances of potential hosts of ARGs were significantly increased with MP/NP addition, implying microbial community structure changes rather than gene horizontal transfer was the main factor promoting ARG propagation under MP/NP pressure.

Metagenomics and network analysis elucidating the coordination between fermentative bacteria and microalgae in a novel bacterial-algal coupling reactor (BACR) for mariculture wastewater treatment

To achieve the goal of treating mariculture wastewater economically and efficiently, a novel bacterial-algal coupling reactor (BACR) integrating acidogenic fermentation and microalgae cultivation was firstly investigated for mariculture wastewater treatment. Volatile fatty acids (VFAs) generated in the dark chamber migrated into the photo chamber for microalgal utilization, which alleviated the pH drop and feedback inhibition of the acidogenic fermentation. The maximum dry cell weight (DCW) of microalgae was 1.46 g/L, and pollutants such as chemical oxygen demand (COD), ammonium (NH₄⁺-N) and total phosphorus (TP) in the BACR were effectively removed under the mixotrophic culture condition. Furthermore, bacterial community profiles and functional genes in the BACR and single acidogenic fermentation reactor were identified. Compared with the single acidogenic fermentation reactor, most of the fermentative bacteria (e.g., Ruminococcus, Christensenellaceae R-7 group, Exiguobacterium, Pseudomonas and Levilinea) were enriched by the BACR. From the genetic perspective, the abundances of dominant genes (ackA, acs and atoD) associated with acetic, propionic and butyric acid production were greatly enhanced in the BACR. In the fatty acid biosynthesis pathway (ko00061), three kinds of high-abundance acetyl-CoA carboxylase genes and eight kinds of downstream functional genes were up-regulated in the BACR. Finally, based on co-occurrence network analysis, the coordination between fermentative bacteria and microalgae in the BACR was revealed. This study provided a deep insight into the advantage and potential of the BACR in mariculture wastewater treatment.

Increase of antibiotic resistance genes via horizontal transfer in single- and two-chamber microbial electrolysis cells

Microbial electrolysis cells (MECs) have been applied for antibiotic degradation but simultaneously induced antibiotic resistance genes (ARGs), thus representing a risk to disseminate antibiotic resistance. However, few studies were on the potential and risk of ARGs transmission in the MECs. This work assessed conjugative transfer of ARGs under three tested conditions (voltages, cell concentration, and donor/recipient ratio) in both single- and two-chamber MECs. The results indicated that voltages (> 0.9 V) facilitated the horizontal frequency of ARGs in the single-chamber MECs and anode chamber of two-chamber MECs. The donor cell number (donor/recipient ratio was 2:1) increased the transfer frequency of ARGs. Furthermore, voltages ranged from 0.9 to 2.5 V increased reactive oxygen species (ROS) production and cell membrane permeability in MECs. These findings offer new insights into the roles of ARG transfer under different applied voltages in the MECs, which should not be ignored for horizontal transfer of antibiotic resistance.

Organic fertilizer potentiates the transfer of typical antibiotic resistance gene among special bacterial species

The propagation of antibiotic resistance genes (ARGs) in environments has evoked many attentions, however, how to identify their host pathogenic bacteria in situ remains a great challenge. Here we explored the bacterial host distribution and dissemination of a typical ARG, sul1 gene, in agricultural soils through the simultaneous detection of sul1 and its host 16S rRNA gene by emulsion paired isolation and concatenation PCR (epicPCR). Compared to chemical fertilizer, organic fertilizer (chicken manure) led to a higher prevalence of sul1 gene in the soil, and dominant bacterial hosts of sul1 gene were classified into Proteobacteria and Bacteroidetes phyla. Additionally, significant higher diversity of antibiotic resistance bacteria (ARB), higher rate of horizontal gene transfer (HGT), higher rate of mobile genetic elements (MGE) and higher proportion of pathogens were all observed in the treatment of organic fertilizer. This study alerts potential health risks of manure applications in agricultural soils.

Enhancing robustness of halophilic aerobic granule sludge by granular activated carbon at decreasing temperature

High salinity seriously inhibits the growth and metabolism of microorganisms, resulting in poor settleability, excessive biomass loss and low treatment efficiency of biological wastewater treatment systems. The development of halophilic aerobic granular sludge (HAGS) is a feasible strategy for addressing this challenge. However, there are problems with the granulation of HAGS and the stability of granules at decreasing temperatures. In this study, granular activated carbon (GAC) with a large specific surface area and good biocompatibility was used to enhance the robustness of HAGS. The results showed that the addition of GAC shortened the granulation time from 60 d (control system) to 35 d (GAC-addition system). The proteins contents of extracellular polymeric substances (EPS) in the GAC-addition system was significantly higher (p < 0.05) than that in the control system during granulation. Satisfactory NH₄⁺-N and chemical oxygen demand (COD) removal efficiencies reached more than 96% in both systems at 18-26 °C. When the operating temperature was lower than 15 °C, the GAC-addition system exhibited better NH₄⁺-N removal performance (>80%) than the control system (<60%). Moreover, the abundance of almost all nitrogen metabolism-related genes in the GAC-addition system was higher than that in the control system. During the granulation process, the enrichment of functional microorganisms, including family Flavobacteriaceae, Rhodobacteraceae, and Cryomorphaceae, may promote the production of EPS by significantly upregulating (p < 0.05) the metabolic pathway "Signaling Molecules and Interaction" in the GAC-addition system. The overexpression of the nitrogen assimilation gene glnA in heterotrophic bacteria (Halomonas and Marinobacterium) may promote the conversion of inorganic nitrogen to extracellular proteins to adapt to the decreased operational temperature. Our findings confirm that GAC addition is a simple but effective strategy to accelerate granulation and enhance the robustness of HAGS in saline wastewater treatment.

Environmental free radicals efficiently inhibit the conjugative transfer of antibiotic resistance by altering cellular metabolism and plasmid transfer

Spread of antibiotic-resistant genes (ARGs) is a global public safety issue and inhibition their transfer is imperative. In this study, a novel strategy using environmental free radical exposure was developed to inhibit conjugative transfer of ARGs (RP4 plasmid) in aqueous solutions. Long-time free radical (·OH, 1O2, and O2·-) exposure significantly suppressed the conjugative transfer frequency of ARGs between Escherichia coli (E. coli) strains, and ·OH was more likely to attack ARG, thereby inhibiting the conjugate transfer frequency, compared to 1O2 and O2·-. Compared with the control, the conjugative transfer frequency significantly decreased from 4.08 × 10-5 to 1.2 × 10-8 after 10 min free radical exposure, confirming that the transfer and proliferation of ARGs were well inhibited. Correspondingly, the number of transconjugant significantly decreased by 61.7% after 10 min free radical exposure. Significant reductions in reactive oxygen species levels (ROS content and enzyme levels) and DNA damage-induced responses in the donor strains were observed after 10 min free radical exposure. Concurrently, intercellular contact was also weakened via inhibiting the synthesis of polysaccharides in extracellular polymeric substances. Moreover, the expressions of plasmid transfer genes were down-regulated after 10 min exposure due to the shortage of adenosine-triphosphate supply. This study firstly disclosed the underneath mechanisms for depressing ARGs transfer and dissemination via environmental free radical exposure.

Three-dimensional biofilm electrode reactors (3D-BERs) for wastewater treatment

Three-dimensional biofilm electrode reactors (3D-BERs) are highly efficient in refractory wastewater treatment. In comparison to conventional bio-electrochemical systems, the filled particle electrodes act as both electrodes and microbial carriers in 3D-BERs. This article reviews the conception and basic mechanisms of 3D-BERs, as well as their current development. The advantages of 3D-BERs are illustrated with an emphasis on the synergy of electricity and microorganisms. Electrode materials utilized in 3D-BERs are systematically summarized, especially the critical particle electrodes. The configurations of 3D-BERs and their integration with wastewater treatment reactors are introduced. Operational parameters and the adaptation of 3D-BERs to varieties of wastewater are discussed. The prospects and challenges of 3D-BERs for wastewater treatment are then presented, and the future research directions are proposed. We believe that this timely review will help to attract more attentions on 3D-BERs investigation, thus promoting the potential application of 3D-BERs in wastewater treatment.

Abundance, diversity and diffusion of antibiotic resistance genes in cat feces and dog feces

The ARG profiles in pet feces, such as cat and dog feces, and their potential threat to environmental safety are still unclear. In this study, ARGs in 45 cat and 28 dog fecal samples were detected, and a diffusion experiment was performed to assess the risk of ARGs diffusion into the air. The results showed that the abundances of ARGs in cat feces and dog feces were high, and the abundance in dog feces (0.89 ± 0.17 copies/bacterial cell) was significantly higher than that in cat feces (0.46 ± 0.09 copies/bacterial cell) (P < 0.05). The bacterial community, especially Firmicutes and Desulfobacterota in cat feces, and Proteobacteria in dog feces, was the main factor affecting the variation in the ARG profiles, contributing to 31.6% and 32.4% of the variation in cat feces and dog feces, respectively. Physicochemical factors (especially NH₄⁺-N) and age also indirectly affected the variation in the ARG profiles by affecting the bacterial community. In addition, the ARGs in cat feces and dog feces diffused into the air, but there was no evidence that this diffusion posed a threat to environmental safety and human health. These results can provide reference data for healthy animal breeding and the prevention and control of ARG pollution.

Source-specific risk apportionment and critical risk source identification of antibiotic resistance in Fenhe River basin, China

A comprehensive understanding of the sources and distribution of antibiotic resistance risk is essential for controlling antibiotic pollution and resistance. Based on surface water samples collected from the Fenhe River basin in the flood season, using the positive matrix factorization (PMF) model, the risk quotient (RQ) method and the multiple attribute decision making (MADM) method, the resistance risk and source-specific resistance risk of antibiotics were analyzed in this study. The results showed that sulfonamides (SAs) were the dominant antibiotics with a mean concentration of 118.30 ng/L, whereas tetracyclines (TCs) and macrolides (MLs) had the highest detection frequencies (100%). The significant resistance risk rate of antibiotics in the entire river basin was 48%, but no high risk occurred. The significant resistance risk rate of quinolones (QNs) was the highest (100%), followed by that of MLs and TCs. Owing to human activities, the most serious resistance risk occurred in the midstream of the river basin. The resistance risk was the lowest upstream. The antibiotics were mainly contributed by six sources. Pharmaceutical wastewater was the main source, accounting for 30%, followed by livestock discharge (22%). The resistance risk from the six sources showed clear differences, but none of the sources caused a high risk of antibiotic resistance. Pharmaceutical wastewater poses the greatest risk of antibiotic resistance in the Fenhe River basin and is widely distributed. The second greatest source was livestock discharge, which was mainly concentrated in the upstream and midstream areas. The critical sources upstream, midstream, and downstream were all pharmaceutical wastewater, whereas the sequences of other sources were different because different areas were affected by different human activities. The proposed method might provide an important reference for the identification the key source of antibiotics and management of antibiotic pollution, as well as help for the management of antibiotics in Fenhe and Shanxi Province.

A Modified Lysimeter Study for Phyto-Treatment of Moderately Saline Wastewater Using Plant-Derived Filter Bedding Materials

The present study focuses on determining the phyto-treatment efficiency for treatment of moderately saline wastewater using organic raw materials, such as rice husk, coconut husk, rice straw, and charcoal. The moderately saline wastewater with total dissolved solids (TDS) concentration up to 6143.33 ± 5.77 mg/L was applied to the lysimeters at the rate of 200 m3 ha-1 day-1 in five different lysimeter treatments planted with Eucalyptus camaldulensis (T1, T2, T3, T4, and T5). T1 was a control without any filter bedding material, whereas rice straw, rice husk, coconut husk, and charcoal were used as filter bedding materials in the T2, T3, T4, and T5 treatment systems, respectively. Each treatment showed significant treatment efficiency wherein T3 had the highest removal efficiency of 76.21% followed by T4 (67.57%), T5 (65.18%), T2 (46.46%), and T1 (45.5%). T3 and T4 also showed higher salt accumulation, such as sodium (Na) and potassium (K). Further, the pollution load in terms of TDS and chemical and biological oxygen demand significantly reduced from leachate in the T3 and T4 treatments in comparison with other treatments. Parameters of the soil, such as electrical conductivity, exchangeable sodium percentage, and cation exchange capacity did not show values corresponding to high salinity or sodic soils, and therefore, no adverse impact on soil was observed in the present study. Also, Eucalyptus camaldulensis plant species showed good response to wastewater treatment in terms of growth parameters, such as root/shoot weight and nitrogen, phosphorus, and potassium (NPK) uptake, plant height, biomass, and chlorophyll content. Root and shoot dry weight were in the order T3 (51.2 and 44.6 g)>T4 (49.3 and 43.5 g) > T5 (47.6 and 40.5 g) > T2 (46.9 and 38.2 g) > T1 (45.6 and 37.1 g). Likewise, the total chlorophyll content was highest in T3 (12.6 μg/g) followed by T4 (12.3 μg/g), T5 (11.9 μg/g), T2 (11.5 μg/g), and the control, that is, T1 (11.0 μg/g). However, the most promising results were obtained for T3 and T4 treatments in comparison with the control (T1), which implies that, among all organic raw materials, coconut and rice husks showed the highest potential for salt accumulation and thereby wastewater treatment. Conclusively, the findings of the study suggest that organic raw material-based amendments are useful in managing the high salts levels in both plants and leachates.

Antibiotic-metal complexes in wastewaters: fate and treatment trajectory

Unregulated usage, improper disposal, and leakage from pharmaceutical use and manufacturing sites have led to high detection levels of antibiotic residues in wastewater and surface water. The existing water treatment technologies are insufficient for removing trace antibiotics and these residual antibiotics tend to interact with co-existing metal ions and form antibiotic-metal complexes (AMCs) with altered bioactivity profile and physicochemical properties. Typically, antibiotics, including tetracyclines, fluoroquinolones, and sulphonamides, interact with heavy metals such as Fe²⁺, Co²⁺, Cu²⁺, Ni²⁺, to form AMCs which are more persistent and toxic than parent compounds. Although many studies have reported antibiotics detection, determination, distribution and risks associated with their environmental persistence, very few investigations are published on understanding the chemistry of these complexes in the wastewater and sludge matrix. This review, therefore, summarizes the structural features of both antibiotics and metals that facilitate complexation in wastewater. Further, this work critically appraises the treatment methods employed for antibiotic removal, individually and combined with metals, highlights the knowledge gaps, and delineates future perspectives for their treatment.

Antibiotic resistance and class 1 integron genes distribution in irrigation water-soil-crop continuum as a function of irrigation water sources

The increasing demand for fresh water coupled with the need to recycle water and nutrients has witnessed a global increase in wastewater irrigation. However, the development of antibiotic resistance hotspots in different environmental compartments, as a result of wastewater reuse is becoming a global health concern. The effect of irrigation water sources (wastewater, surface water, fresh water) on the presence and abundance of antibiotic resistance genes (ARGs) (bla_CTX-m-32, tet-W, sul1, cml-A, and erm-B) and class 1 integrons (intI1) were investigated in the irrigation water-soil-crop continuum using quantitative real-time PCR (qPCR). Sul1 and bla_CTX-m-32 were the most and least abundant ARGs in three environments, respectively. The abundance of ARGs and intI1 significantly decreased from wastewater to surface water and then fresh water. However, irrigation water sources had no significant effect on the abundance of ARGs and intI1 in soil and crop samples. Principal component analysis (PCA) showed that UV index and air temperature attenuate the abundance of ARGs and intI1 in crop samples whereas the air humidity and soil electrical conductivity (EC) promotes the ARGs and intI1. So that the climate condition of semi-arid regions significantly affects the abundance of ARGs and intI1 in crop samples. The results suggest that treated wastewater might be safely reused in agricultural practice in semi-arid regions without a significant increase of potential health risks associated with ARGs transfer to the food chain. However, further research is needed for understanding and managing ARGs transfer from the agricultural ecosystem to humans through the food chain.

A review of the bioelectrochemical system as an emerging versatile technology for reduction of antibiotic resistance genes

Antibiotic contamination and the resulting resistance genes have attracted worldwide attention because of the extensive overuse and abuse of antibiotics, which seriously affects the environment as well as human health. Bioelectrochemical system (BES), a potential avenue to be explored, can alleviate antibiotic pollution and reduce antibiotic resistance genes (ARGs). This review mainly focuses on analyzing the possible reasons for the good performance of ARG reduction by BESs and potential ways to improve its performance on the basis of revealing the generation and transmission of ARGs in BES. This system reduces ARGs through two pathways: (1) the contribution of BES to the low selection pressure of ARGs caused by the efficient removal of antibiotics, and (2) inhibition of ARG transmission caused by low sludge yield. To promote the reduction of ARGs, incorporating additives, improving the removal rate of antibiotics by adjusting the environmental conditions, and controlling the microbial community in BES are proposed. Furthermore, this review also provides an overview of bioelectrochemical coupling systems including the BES coupled with the Fenton system, BES coupled with constructed wetland, and BES coupled with photocatalysis, which demonstrates that this method is applicable in different situations and conditions and provides inspiration to improve these systems to control ARGs. Finally, the challenges and outlooks are addressed, which is constructive for the development of technologies for antibiotic and ARG contamination remediation and blocking risk migration.

Current available treatment technologies for saline wastewater and land-based treatment as an emerging environment-friendly technology: A review

Different industrial activities such as agro-food processing and manufacturing, leather manufacturing, and paper and pulp production generate highly saline wastewater. Direct discharge of saline wastewater has resulted in pollution of waterbodies by very high magnitudes. Consequently, an enormous number of pollutants such as heavy metals, salts, and organic matter are also released into the environment threatening the survival of human and biota. Saline wastewater also has significant effects on survival of plants, agricultural activities, and groundwater systems. Several treatments and disposal technologies are available for saline wastewater, but the selection of the most appropriate treatment and disposal technology still remains a major challenge with respect to the economic or technical constraints. Considering the sustainable management of saline wastewater, the present review is an attempt to compile the existing and emerging technologies for the treatment of saline wastewater. Among all the individual and hybrid technologies, land-based treatment systems are proven to be the most efficient technologies considering the energy demands, economic, and treatment efficiencies. Likewise, new and sustainable technologies are the need of hour integrating both the treatment and management and the resource recovery factors along with the ultimate goal of the protection in terms of human health and environmental aspect. PRACTITIONER POINTS: Physico-chemical treatment technologies for saline wastewater. Combined/Hybrid technologies for the treatment of saline wastewater. Land-based treatments as the environment friendly and sustainable method for saline wastewater treatment and disposal. Role of phytoremediation in land-based treatment.

Mechanisms of metabolic performance enhancement and ARGs attenuation during nZVI-assisted anaerobic chloramphenicol wastewater treatment

Anaerobic wastewater treatment is a promising technology for refractory pollutant treatment. The nano zero-valent iron (nZVI) assisted anaerobic system could enhance contaminant removal. In this work, we added nZVI into an anaerobic system to investigate the effects on system performances and metabolic mechanism for chloramphenicol (CAP) wastewater treatment. As nZVI concentrations increased from 0 to 1 g/L, the CAP removal efficiency was appreciably improved from 46.5% to 99.2%, while the CH₄ production enhanced more than 20 times. The enhanced CAP removal resulted from the enrichments of dechlorination-related bacteria (Hyphomicrobium) and other functional bacteria (e.g., Zoogloea, Syntrophorhabdus) associated with refractory contaminants degradation. The improved CH₄ production was ascribed to the increases in fermentative-related bacteria (Smithella and Acetobacteroides), homoacetogen (Treponema), and methanogens. The increased abundances of anaerobic functional genes further verified the mechanism of CH₄ production. Furthermore, the abundances of potential hosts of antibiotic resistance genes (ARGs) were reduced under high nZVI concentration (1 g/L), contributing to ARGs attenuation. This study provides a comprehensive analysis of the mechanism in metabolic performance enhancement and ARGs attenuation during nZVI-assisted anaerobic CAP wastewater treatment.

Role of bioelectrochemical systems for the remediation of emerging contaminants from wastewater: A review

Bioelectrochemical systems (BESs) are a unique group of wastewater remediating technology that possesses the added advantage of valuable recovery with concomitant wastewater treatment. Moreover, due to the application of robust microbial biocatalysts in BESs, effective removal of emerging contaminants (ECs) can be accomplished in these BESs. Thus, this review emphasizes the recent demonstrations pertaining to the removal of complex organic pollutants of emerging concern present in wastewater through BES. Owing to the recalcitrant nature of these pollutants, they are not effectively removed through conventional wastewater treatment systems and thereby are discharged into the environment without proper treatment. Application of BES in terms of ECs removal and degradation mechanism along with valuables that can be recovered are discussed. Moreover, the factors affecting the performance of BES, like biocatalyst, substrate, salinity, and applied potential are also summarized. In addition, the present review also elucidates the occurrence and toxic nature of ECs as well as future recommendations pertaining to the commercialization of this BES technology for the removal of ECs from wastewater. Therefore, the present review intends to aid the researchers in developing more efficient BESs for the removal of ECs from wastewater.

High-Throughput Single-Cell Technology Reveals the Contribution of Horizontal Gene Transfer to Typical Antibiotic Resistance Gene Dissemination in Wastewater Treatment Plants

The spread of antibiotic resistance genes (ARGs) has gained much attention worldwide, while the contribution of vertical gene transfer (VGT) and horizontal gene transfer (HGT) is still elusive. Here, we improved an emerging high-throughput single-cell-based technology, emulsion, paired isolation, and concatenation polymerase chain reaction (epicPCR), by lengthening the sequence of ARG in the fused ARG-16S rRNA fragments to cover the variance of both ARG and its hosts. The improved epicPCR was applied to track the hosts of a widely detected ARG, sul1 gene, in five urban wastewater treatment plants (UWTPs) during two seasons. The sul1 host bacteria were highly diverse and mostly classified as Proteobacteria and Bacteroidetes. Clear seasonal divergence of α-diversity and interaction networks were present in the host community. The consensus phylogenetic trees of the sul1 gene and their host demonstrated incorrespondence on the whole and regularity on abundant groups, suggesting the important role of both HGT and VGT, respectively. The relative importance of these two ways was further measured; HGT (54%) generally played an equal or even more important role as VGT (46%) in UWTPs. The application of the improved epicPCR technology provides a feasible approach to quantify the relative contributions of VGT and HGT in environmental dissemination of ARGs.

Contribution of microplastic particles to the spread of resistances and pathogenic bacteria in treated wastewaters

Microplastic Particles (MPs) are ubiquitous pollutants widely found in aquatic ecosystems. Although MPs are mostly retained in wastewater treatment plants (WWTPs), a high number of MPs reaches the open waters potentially contributing to the spread of pathogenic bacteria and antibiotic resistance genes in the environment. Nowadays, a limited number of studies have focused on the role of MPs as carriers of potentially pathogenic and antibiotic resistant bacteria in WWTPs. Thus, an investigation on the community composition (by 16S rRNA gene amplicon sequencing) and the abundance of antibiotic and metal resistance genes (by qPCR) of the biofilm on MPs (the plastisphere) and of planktonic bacteria in treated (pre- and post-disinfection) wastewaters was performed. MPs resulted to be very similar in terms of type, color, size, and chemical composition, before and after the disinfection. The bacterial community on MPs differed from the planktonic community in terms of richness, composition, and structure of the community network. Potentially pathogenic bacteria generally showed higher abundances in treated wastewater than in the biofilm on MPs. Furthermore, among the tested resistance genes, only sul2 (a common resistance gene against sulfonamides) resulted to be more abundant in the plastisphere than in the planktonic bacterial community. Our results suggest that the wastewater plastisphere could promote the spread of pathogenic bacteria and resistance genes in aquatic environment although with a relatively lower contribution than the wastewater planktonic bacterial community.

Effect of preferential UV photolysis on the source control of antibiotic resistome during subsequent biological treatment systems

The environmental spread of antibiotic resistance genes (ARGs) from the direct application of traditional biological treatment systems for antibiotics in water is a potential public health threat. UV photolysis has been proved to be an efficient pretreatment method for antibacterial activity elimination, but the fate of antibiotic resistome in subsequent bioreactors fed with pretreated florfenicol (FLO) in synthetic wastewater is still unknown. Antibacterial activity in synthetic wastewater was effectively eliminated by UV irradiation pretreatment, and the diversity and abundance of detected ARGs in both aerobic and anaerobic bioreactors were significantly lower than those without pretreatment. Meanwhile, UV irradiation pretreatment shaped the structure and composition of sludge microbial communities in the subsequent bioreactors closer to those of the FLO-free groups. The relative abundances of Pseudomonas and Escherichia-Shigella working as the potential hosts of ARGs were significantly reduced in aerobic and anaerobic bioreactors, respectively. The significantly positive correlation between floR and intI1 and the decrease of intI1 abundance in UV photolytic pretreatment groups indicated that the horizontal transfer of floR was decreased. The study provides new insights into the effect of preferential UV photolysis as a pretreatment method on the source control of antibiotic resistome in subsequent biological treatment process.

Responses of aerobic granular sludge to fluoroquinolones: Microbial community variations, and antibiotic resistance genes

In this study, aerobic granular sludge (AGS) was operated under high levels of ammonium for removing three fluoroquinolones (FQs), i.e., ciprofloxacin (CFX), ofloxacin (OFX), and norfloxacin (NFX) at 3, 300, and 900 µg/L, respectively. Two key objectives were to investigate the differential distribution of antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs) in sludge fractions and to evaluate correlations between ARGs and MGEs to nitrifying and denitrifying bacteria. AGS showed excellent stability under the exposure of FQs, with nitrite-oxidizing bacteria (NOB) more sensitive to FQs than ammonium-oxidizing bacteria (AOB). Specific oxygen utilization rates (SOUR) showed a reduction of 26.9% for NOB but only 4.0% of the reduced activity of AOB by 3 μg/L FQs. AGS performed better removal efficiencies for CFX and NFX than OFX, and the efficiencies increased with their elevated concentrations, except at 900 μg/L FQs. The elevated FQ concentrations led to a significant enrichment of intI1 and genus Thauera, while qnrD and qnrS showed no accumulation. Compared to nitrifiers, FQs relevant ARGs and the intI1 gene preferred to exist in denitrifiers, and the abundance of denitrifiers behaved a decreasing trend with the sludge size. Two quinoline-degrading bacteria were found in the AGS system, i.e., Alicycliphilus and Brevundimonas, possibly carrying qnrS and qnrD, respectively. Their relative abundance increased with the sludge size, which was 2.18% in sludge <0.5 mm and increased to 3.70% in sludge >2.0 mm, suggesting that the AGS may be a good choice in treating FQs-containing wastewater.

Effects of two ecological earthworm species on tetracycline degradation performance, pathway and bacterial community structure in laterite soil

This study explored the change of tetracycline degradation efficiency, metabolic pathway, soil physiochemical properties and degraders in vermiremediation by two earthworm species of epigeic Eisenia fetida and endogeic Amynthas robustus. We found a significant acceleration of tetracycline degradation in both earthworm treatments, and 4-epitetracycline dehydration pathway was remarkably enhanced only by vermiremediation. Tetracycline degraders from soils, earthworm intestines and casts were different. Ralstonia and Sphingomonas were potential tetracycline degraders in soils and metabolized tetracycline through direct dehydration pathway. Degraders in earthworm casts (Comamonas, Acinetobacter and Stenotrophomonas) and intestines (Pseudomonas and Arthrobacter) dehydrated 4-epitetracycline into 4-epianhydrotetracycline. More bacterial lineages resisting tetracycline were found in earthworm treatments, indicating the adaptation of soil and intestinal flora under tetracycline pressure. Earthworm amendment primarily enhanced tetracycline degradation by neutralizing soil pH and consuming organic matters, stimulating both direct dehydration and epimerization-dehydration pathways. Our findings proved that vermicomposting with earthworms is effective to alter soil microenvironment and accelerate tetracycline degradation, behaving as a potential approach in soil remediation at tetracycline contaminated sites.

Metagenomic analysis reveals the shared and distinct features of the soil resistome across tundra, temperate prairie, and tropical ecosystems

BACKGROUND

Soil is an important reservoir of antibiotic resistance genes (ARGs), but their potential risk in different ecosystems as well as response to anthropogenic land use change is unknown. We used a metagenomic approach and datasets with well-characterized metadata to investigate ARG types and amounts in soil DNA of three native ecosystems: Alaskan tundra, US Midwestern prairie, and Amazon rainforest, as well as the effect of conversion of the latter two to agriculture and pasture, respectively.

RESULTS

High diversity (242 ARG subtypes) and abundance (0.184-0.242 ARG copies per 16S rRNA gene copy) were observed irrespective of ecosystem, with multidrug resistance and efflux pump the dominant class and mechanism. Ten regulatory genes were identified and they accounted for 13-35% of resistome abundances in soils, among them arlR, cpxR, ompR, vanR, and vanS were dominant and observed in all studied soils. We identified 55 non-regulatory ARGs shared by all 26 soil metagenomes of the three ecosystems, which accounted for more than 81% of non-regulatory resistome abundance. Proteobacteria, Firmicutes, and Actinobacteria were primary ARG hosts, 7 of 10 most abundant ARGs were found in all of them. No significant differences in both ARG diversity and abundance were observed between native prairie soil and adjacent long-term cultivated agriculture soil. We chose 12 clinically important ARGs to evaluate at the sequence level and found them to be distinct from those in human pathogens, and when assembled they were even more dissimilar. Significant correlation was found between bacterial community structure and resistome profile, suggesting that variance in resistome profile was mainly driven by the bacterial community composition.

CONCLUSIONS

Our results identify candidate background ARGs (shared in all 26 soils), classify ARG hosts, quantify resistance classes, and provide quantitative and sequence information suggestive of very low risk but also revealing resistance gene variants that might emerge in the future. Video abstract.

Exploring simultaneous nitrous oxide and methane sink in wetland sediments under anoxic conditions

Methane (CH₄) and nitrous oxide (N₂O) are the most powerful greenhouse gases globally; recent emissions exceed previous estimates. The potential link between N₂O reduction and CH₄ oxidation in anoxic wetland sediments would be a sink for both gases, which has attracted broad attention. To explore the simultaneous N₂O and CH₄ biotransformation, wetland sediments were used to inoculate an enrichment reactor, continuously fed with CH₄ and N₂O for 500 days. After enrichment, the CH₄ oxidation rate reached 2.8 μmol·g^-1_dw·d^-1, which was 800-fold higher than the rate of the wetland sediments used as inoculum. Moreover, stable isotopic tracing proved CH₄ oxidation was driven by N₂O consumption under anoxic conditions. Genomic sequencing showed that the microbial community was dominated by methanotrophs. Species of Methylocaldum genus, belonging to γ-Proteobacteria class, were significantly enriched, and became the predominant methanotrophs. Quantitative analysis indicated methane monooxygenase and nitrous oxide reductase increased by 38- and 8-fold compared to the inoculum. As to the potential mechanisms, we propose that N₂O-driven CH₄ oxidation was mediated by aerobic methanotrophs solely or along with denitrifying bacteria under hypoxia. Electrons and energy are generated and transferred in the oxidative phosphorylation pathway. Our findings expand the range of electron acceptors associated with CH₄ oxidation as well as elucidate the significant role of methanotrophs relative to both carbon and nitrogen cycles.

Antibiotics in wastewater: From its occurrence to the biological removal by environmentally conscious technologies

In this critical review, we explored the most recent advances about the fate of antibiotics on biological wastewater treatment plants (WWTP). Although the occurrence of these pollutants in wastewater and natural streams has been investigated previously, some recent publications still expose the need to improve the detection strategies and the lack of information about their transformation products. The role of the antibiotic properties and the process operating conditions were also analyzed. The pieces of evidence in the literature associate several molecular properties to the antibiotic removal pathway, like hydrophobicity, chemical structure, and electrostatic interactions. Nonetheless, the influence of operating conditions is still unclear, and solid retention time stands out as a key factor. Additionally, the efficiencies and pathways of antibiotic removals on conventional (activated sludge, membrane bioreactor, anaerobic digestion, and nitrogen removal) and emerging bioprocesses (bioelectrochemical systems, fungi, and enzymes) were assessed, and our concern about potential research gaps was raised. The combination of different bioprocess can efficiently mitigate the impacts generated by these pollutants. Thus, to plan and design a process to remove and mineralize antibiotics from wastewater, all aspects must be addressed, the pollutant and process characteristics and how it is the best way to operate it to reduce the impact of antibiotics in the environment.