Assessing the efficacy of bleaching powder in disinfecting marine water: Insights from the rapid recovery of microbiomes. - Related Documents




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763301.0000Assessing the efficacy of bleaching powder in disinfecting marine water: Insights from the rapid recovery of microbiomes. Single-bleaching powder disinfection is a highly prevalent practice to disinfect source water for marine aquaculture to prevent diseases. However, due to the decay of active chlorine and the presence of disinfectant resistance bacteria (DRB), the effects of bleaching powder on prokaryotic community compositions (PCCs) and function in marine water remain unknown. In the present study, the source water in a canvas pond was treated with the normal dose of bleaching powder, and the impact on PCCs and functional profiles was investigated using 16S rRNA gene amplicon sequencing. The bleaching powder strongly altered the PCCs within 0.5 h, but they began to recover at 16 h, eventually achieving 76% similarity with the initial time at 72 h. This extremely rapid recovery was primarily driven by the decay of Bacillus and the regrowth of Pseudoalteromonas, both of which are DRB. Abundant community not only help PCCs recover but also provide larger functional redundancy than rare community. During the recovery of PCCs, stochastic processes drove the community assembly. After 72 h, five out of seven identified disinfectant resistance genes related to efflux pump systems were highly enriched, primarily in Staphylococcus and Bacillus. However, 15 out of the 16 identified antibiotic resistance genes (ARGs) remained unchanged compared to the initial time, indicating that bleaching powder does not contribute to ARGs removal. Overall, the findings demonstrate that single-bleaching powder disinfection cannot successfully meet the objective of disease prevention in marine aquaculture water due to the extremely rapid recovery of PCCs. Hence, secondary disinfection or novel disinfection strategies should be explored for source water disinfection.202337295228
763210.9999Metagenomic insights into the rapid recovery mechanisms of prokaryotic community and spread of antibiotic resistance genes after seawater disinfection. Disinfectants, such as bleaching powder, are widely employed in marine aquaculture worldwide to control the bacterial pathogens and eliminate antibiotic resistance genes (ARGs). Nevertheless, the rapid recovery of prokaryotic community compositions (PCCs) after disinfection may significantly influence the overall efficacy of disinfection. Presently, little is known about the rapid recovery mechanisms of PCCs and its impact on the removal of ARGs in seawater. In this study, 16S rRNA gene sequencing and metagenomic analysis were used to address the above concerns through simulating the disinfection process in aquaculture. The results showed that recovery of PCCs began within 16 h. The underlying mechanisms of the rapid recovery of PCCs were the synergistic interactions between microbes and the residues of disinfection-resistant bacteria (DRB). Disinfection resistance genes (DRGs) related to efflux pump serve as the primary molecular foundation providing DRB to resist disinfection. Among the 78 annotated ARGs, only 10 ARGs exhibited a significant decrease (P < 0.05) after 72 h, implying the ineffective removal of ARGs by bleaching powder. Furthermore, bacterial co-resistance to disinfectants and antibiotics was observed. Genome analysis of two highly resistant DRB from Pseudomonadaceae revealed that both DRB carried 16 DRGs, aiding the recovery of PCCs and the spread of ARGs. These findings provide novel insights in the mechanisms of the rapid recovery of PCCs and bacterial co-resistance to disinfectants and antibiotics, which can be crucial for the management of pathogens and antibiotic resistance in seawater.202539637691
751020.9997Impacts of antibiotics on biofilm bacterial community and disinfection performance on simulated drinking water supply pipe wall. Overuse of antibiotics is accelerating the spread of resistance risk in the environment. In drinking water supply systems, the effect of antibiotics on the resistance of biofilm is unclear, and there have been few studies in disinfectant-containing systems. Here, we designed a series of drinking water supply reactors to investigate the effects of antibiotics on biofilm and bacteria in the water. At low concentrations, antibiotics could promote the growth of bacteria in biofilm; among the tested antibiotics (tetracycline, sulfadiazine and chloramphenicol), tetracycline had the strongest ability to promote this. And the antibiotic resistant bacteria (ARB) could inhibit the growth of bacteria in drinking water. Results have shown that antibiotics enhanced the bacterial chlorine resistance in the effluent, but reduced that in the biofilm. Furthermore, metagenomic analysis showed that antibiotics reduced the richness of biofilm communities. The dominant phyla in the biofilm were Proteobacteria, Planctomycetes, and Firmicutes. In tetracycline-treated biofilm, the dominant phylum was Planctomycetes. In sulfadiazine- and chloramphenicol-treated groups, bacteria with complex cell structures preferentially accumulated. The dominant class in biofilm in the ARB-added group was Gammaproteobacteria. The abundance of antibiotic resistant genes (ARGs) was correlated with biofilm community structure. This study shows that antibiotics make the biofilm community structure of drinking water more resistant to chlorine. ARGs may be selective for certain bacteria in the process, and there may ultimately be enhanced chlorine and antibiotic resistance of effluent bacteria in drinking water.202134256291
729930.9996Short-term exposure to benzalkonium chloride in bacteria from activated sludge alters the community diversity and the antibiotic resistance profile. The continuous introduction of cleaning products containing benzalkonium chloride (BAC) from household discharges can mold the microbial communities in wastewater treatment plants (WWTPs) in a way still poorly understood. In this study, we performed an in vitro exposure of activated sludge from a WWTP in Costa Rica to BAC, quantified the changes in intI1, sul2, and qacE/qacEΔ1 gene profiles, and determined alterations in the bacterial community composition. The analysis of the qPCR data revealed elevated charges of antibiotic resistance genes in the microbial community; after BAC's exposure, a significant increase in the qacE/qacEΔ1 gene, which is related to ammonium quaternary resistance, was observed. The 16S rRNA gene sequences' analysis showed pronounced variations in the structure of the bacterial communities, including reduction of the alpha diversity values and an increase of the relative abundance of Alphaproteobacteria, particularly of Rhodospseudomonas and Rhodobacter. We confirmed that the microbial communities presented high resilience to BAC at the mg/mL concentration, probably due to constant exposure to this pollutant. They also presented antibiotic resistance-related genes with similar mechanisms to tolerate this substance. These mechanisms should be explored more thoroughly, especially in the context of high use of disinfectant.202134874898
719040.9996Dynamics of microbial community and tetracycline resistance genes in biological nutrient removal process. The occurrence of antibiotics in wastewater has become a serious concern due to the possible development of antibiotic resistant bacteria in wastewater treatment process. In order to understand the dynamics of microbial community and tetracycline resistance genes in biological nutrient removal (BNR) process, three lab-scale sequencing batch reactors (SBRs) were operated under the stress of tetracycline. Results indicated that microbial community structure was altered, and tetracycline efflux pump genes were enhanced over 150-day operation in the presence of trace tetracycline of 20 and 50 μg L(-1), respectively. Furthermore, when the initial tetracycline concentrations were increased to 2 and 5 mg L(-1), substantial enhancement of tetracycline resistance was observed, accompanied with a sharp shift in microbial community structure. In this study, horizontal gene transfer was found to be the main mechanism for the development of tetracycline resistance genes under the long-terms stress of trace tetracycline. About 90.34% of the observed variations in tetracycline resistance genes could be explained by the dynamics of potential hosts of tetracycline resistance genes and class 1 integron. It should be noticed that the functional bacteria (e.g. Nitrospira, Dechloromonas, Rhodobacter and Candidatus_Accumulibacter) responsible for nutrient removal were positively correlated with tetracycline resistance, which might promote the prevalence of tetracycline resistance during biological wastewater treatment. Consequently, this study provided in-depth insights into the occurrence and prevalence of tetracycline resistance genes and their microbial hosts in BNR process.201930849601
756450.9996Formation, characteristics and microbial community of aerobic granular sludge in the presence of sulfadiazine at environmentally relevant concentrations. The growing occurrence of antibiotics in water environment is causing increasing concern. To investigate the impact of frequently detected sulfadiazine on the formation of aerobic granular sludge, four sequencing batch reactors (SBRs) were set up with different environmentally relevant concentrations of sulfadiazine. Results showed that sulfadiazine pressure could lead to larger and more compact sludge particles and cause slight effect on reactor performance. Presence of sulfadiazine apparently increased the extracellular polymeric substances (EPS) secretion of microorganisms. Quantitative polymerase chain reaction (qPCR) showed that the abundances of sulfanilamide resistance genes in sludge increased with addition of sulfadiazine significantly. Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) was used to predict functional genes, results showed that sulfadiazine led to an increase of specific functional genes. Thereby, it concluded that microorganisms could change the community structure by acclimating of functional bacteria and antibiotic resistance species to adapt to the antibiotic stress.201829197771
808260.9996Deciphering the toxic effects of antibiotics on denitrification: Process performance, microbial community and antibiotic resistance genes. The extensive application of antibiotics, and the occurrence and spread of antibiotic resistance genes (ARGs) shade health risks to human and animal. The long-term effects of sulfamethoxazole (SMX) and tetracycline (TC) on denitrification process were evaluated in this study, with the focus on nitrogen removal performance, microbial community and ARGs. Results showed that low-concentration SMX and TC (<0.2 mg L(-1)) initially caused a deterioration in nitrogen removal performance, while higher concentrations (0.4-20 mg L(-1)) of both antibiotics had no further inhibitory influences. The abundances of ARGs in both systems generally increased during the whole period, and most of them had significant correlations with intI1, especially efflux-pump genes. Castellaniella, which was the dominant genus under antibiotic pressure, might be potential resistant bacteria. These findings provide an insight into the toxic effects of different antibiotics on denitrification process, and guides future efforts to control antibiotics pollution in ecosystems.202032250829
761170.9996Response of microorganisms in biofilm to sulfadiazine and ciprofloxacin in drinking water distribution systems. Effects of sulfadiazine and ciprofloxacin on microorganisms in biofilm of drinking water distribution systems (DWDSs) were studied. The results verified that the increases of 16S rRNA for total bacteria and bacterial genus Hyphomicrobium were related to the promotion of antibiotic resistance genes (ARGs) and class 1 integrons (int1) in DWDSs with sulfadiazine and ciprofloxacin. Moreover, the bacteria showed higher enzymatic activities in DWDSs with sulfadiazine and ciprofloxacin, which resulted in more production of extracellular polymeric substances (EPS). The higher contents of EPS proteins and secondary structure β-sheet promoted bacterial aggregation and adsorption onto surface of pipelines to form biofilm. EPS can serve as a barrier for the microorganisms in biofilm. Therefore, the biofilm bacterial communities shifted and the 16S rRNA for total bacteria increased in DWDSs with antibiotics, which also drove the ARGs promotion. Furthermore, the two antibiotics exhibited stronger combined effects than that caused by sulfadiazine and ciprofloxacin alone.201930471500
729880.9996Chronic exposure to triclosan sustains microbial community shifts and alters antibiotic resistance gene levels in anaerobic digesters. Triclosan, an antimicrobial chemical found in consumer personal care products, has been shown to stimulate antibiotic resistance in pathogenic bacteria. Although many studies focus on antibiotic resistance pertinent to medical scenarios, resistance developed in natural and engineered environments is less studied and has become an emerging concern for human health. In this study, the impacts of chronic triclosan (TCS) exposure on antibiotic resistance genes (ARGs) and microbial community structure were assessed in lab-scale anaerobic digesters. TCS concentrations from below detection to 2500 mg kg(-1) dry solids were amended into anaerobic digesters over 110 days and acclimated for >3 solid retention time values. Four steady state TCS concentrations were chosen (30-2500 mg kg(-1)). Relative abundance of mexB, a gene coding for a component of a multidrug efflux pump, was significantly higher in all TCS-amended digesters (30 mg kg(-1) or higher) relative to the control. TCS selected for bacteria carrying tet(L) and against those carrying erm(F) at concentrations which inhibited digester function; the pH decrease associated with digester failure was suspected to cause this selection. Little to no impact of TCS was observed on intI1 relative abundance. Microbial communities were also surveyed by high-throughput 16S rRNA gene sequencing. Compared to the control digesters, significant shifts in community structure towards clades containing commensal and pathogenic bacteria were observed in digesters containing TCS. Based on these results, TCS should be included in studies and risk assessments that attempt to elucidate relationships between chemical stressors (e.g. antibiotics), antibiotic resistance genes, and public health.201627291499
750190.9996Enhanced sensitivity of extracellular antibiotic resistance genes (ARGs) to environmental concentrations of antibiotic. As emerging contaminants, antibiotics are frequently present in various environments, particularly rivers, albeit often at sublethal concentrations (ng/L∼μg/L). Assessing the risk associated with these low levels, which are far below the lethal threshold for most organisms, remains challenging. In this study, using microcosms containing planktonic bacteria and biofilm, we examined how antibiotic resistance genes (ARGs) in different physical states, including intracellular ARGs (iARGs) and extracellular ARGs (eARGs) responded to these low-level antibiotics. Our findings reveal a positive correlation between sub-lethal antibiotic exposure (ranging from 0.1 to 10 μg/L) and increased prevalence (measured as ARG copies/16s rDNA) of both iARGs and eARGs in planktonic bacteria. Notably, eARGs demonstrated greater sensitivity to antibiotic exposure compared to iARGs, with a lower threshold (0.1 μg/L for eARGs versus 1 μg/L for iARGs) for abundance increase. Moreover, ARGs in biofilms demonstrates higher sensitivity to antibiotic exposure compared to planktonic bacteria. To elucidate the underlying mechanisms, we established an integrated population dynamics-pharmacokinetics-pharmacodynamics (PD-PP) model. This model indicates that the enhanced sensitivity of eARGs is primarily driven by an increased potential for plasmid release from cells under low antibiotic concentrations. Furthermore, the accumulation of antibiotic in biofilms induces a greater sensitivity of ARG compared to the planktonic bacteria. This study provides a fresh perspective on the development of antibiotic resistance and offers an innovative approach for assessing the risk of sublethal antibiotic in the environment.202438797215
7022100.9996Fate of antibiotics, antibiotic-resistant bacteria, and cell-free antibiotic-resistant genes in full-scale membrane bioreactor wastewater treatment plants. The removal of antibiotics, antibiotic-resistant bacteria (ARB), and cell-free antibiotic-resistant genes (ARGs) and the microbial community of ARB were investigated in detail to understand their fate and provide valuable information on the feasibility of full-scale membrane bioreactor (MBR). The potential risks of cell-free ARGs to the receiving environment were discovered. High influent antibiotic concentration could inhibit the microbial activity of MBR sludge, whereas good antibiotic removal could be maintained because of relatively long solid retention time and high biomass retention. Approximately 61.8%-77.5% of the total antibiotics were degraded, and 22.5%-38.2% of the total antibiotics were adsorbed by MBR sludge on average. The individual antibiotic removal presented intense discrepancy because of the chemical construction and distribution coefficient of antibiotics. Aeromonas exhibited specific antibiotic resistance to ampicillin and erythromycin, Escherichia became the predominant genera in kanamycin-ARB and tetracycline-ARB, and Klebsiella and Bacteroides were the particular genera that exhibited distinct antibiotic resistance to ciprofloxacin. A significant correlation was found between cell-free ARG abundance and ARB content, and relatively high effluent cell-free ARG abundance facilitated the proliferation and transmission of ARB. The impacts of the receiving environment to eliminate the ecological risks and severe threats to human health should be investigated because of the low decay ratio and long-term persistence of cell-free ARGs.202031986335
7584110.9996Responses 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.202236205764
7030120.9996Metagenomic profiling of antibiotic resistance genes/bacteria removal in urban water: Algal-bacterial consortium treatment system. Antibiotic resistance genes (ARGs) have exhibited significant ecological concerns, especially in the urban water that are closely associated with human health. In this study, with presence of exogenous Chlorella vulgaris-Bacillus licheniformis consortium, most of the typical ARGs and MGEs were removed. Furthermore, the relative abundance of potential ARGs hosts has generally decreased by 1-4 orders of magnitude, revealing the role of algal-bacterial consortium in cutting the spread of ARGs in urban water. While some of ARGs such as macB increased, which may be due to the negative impact of algicidal bacteria and algal viruses in urban water on exogenous C. vulgaris and the suppression of exogenous B. licheniformis by indigenous microorganisms. A new algal-bacterial interaction might form between C. vulgaris and indigenous microorganisms. The interplay between C. vulgaris and bacteria has a significant impact on the fate of ARGs removal in urban water.202438801952
7013130.9996Bacterial Community Shift Drives Antibiotic Resistance Promotion during Drinking Water Chlorination. For comprehensive insights into the effects of chlorination, a widely used disinfection technology, on bacterial community and antibiotic resistome in drinking water, this study applied high-throughput sequencing and metagenomic approaches to investigate the changing patterns of antibiotic resistance genes (ARGs) and bacterial community in a drinking water treatment and distribution system. At genus level, chlorination could effectively remove Methylophilus, Methylotenera, Limnobacter, and Polynucleobacter, while increase the relative abundance of Pseudomonas, Acidovorax, Sphingomonas, Pleomonas, and Undibacterium in the drinking water. A total of 151 ARGs within 15 types were detectable in the drinking water, and chlorination evidently increased their total relative abundance while reduced their diversity in the opportunistic bacteria (p < 0.05). Residual chlorine was identified as the key contributing factor driving the bacterial community shift and resistome alteration. As the dominant persistent ARGs in the treatment and distribution system, multidrug resistance genes (mainly encoding resistance-nodulation-cell division transportation system) and bacitracin resistance gene bacA were mainly carried by chlorine-resistant bacteria Pseudomonas and Acidovorax, which mainly contributed to the ARGs abundance increase. The strong correlation between bacterial community shift and antibiotic resistome alteration observed in this study may shed new light on the mechanism behind the chlorination effects on antibiotic resistance.201526397118
6946140.9996Persistence of Salmonella Typhimurium and antibiotic resistance genes in different types of soil influenced by flooding and soil properties. Salmonella is a zoonotic foodborne bacterial pathogen that can seriously harm health. Persistence of Salmonella and antibiotic resistance genes (ARGs) in different types of soil under flooding and natural conditions are rare explored. This study investigated the dynamic changes of the Salmonella, ARGs and bacterial communities in three types of soils applied with pig manure in lab scale. Abundance of the Salmonella Typhimurium in soils reduced to the detection limit varied from 40 to 180 days, most of the Salmonella did not survive in soil for more than 90 days. Flooding and soil texture (content of sand) promote the decline rate of Salmonella. No Salmonella was found have acquired resistance gene from the soil or manure after 90 days. 64 ARGs and 11 MGEs were quantified, abundance of these genes and risky ARGs both gradually decline along with the extension of time. Most of the extrinsic ARGs cannot colonize in soil, cellular protection and antibiotic deactivation were their main resistance mechanism. Multidrug resistance and efflux pump were the dominant class and mechanism of soil intrinsic ARGs. Flooding can affect the ARGs profiles by reducing the types of extrinsic ARGs invaded into soil and inhibit the proliferation of intrinsic genes. Soil sand content, soil moisture and nutrition concentrations had significant direct effect on the abundance or profile of ARGs. Soil bacterial community structures also changed along with the extension of time and affected by flooding. Network analyses between ARGs and bacteria taxa revealed that Actinobacteria and Myxococcia were the main hosts of intrinsic ARGs, some taxa may play a role in inhibiting extrinsic ARGs colonization in the soils. These findings unveil that saturate soil with water may play a positive role in reducing potential risk of Salmonella and ARGs in the farmland environment.202236436254
7301150.9996Water flow paths are hotspots for the dissemination of antibiotic resistance in soil. Antibiotic resistance genes in soil pose a potential risk for human health. They can enter the soil by irrigation with untreated or insufficiently treated waste water. We hypothesized that water flow paths trigger the formation of antibiotic resistance, since they transport antibiotics, multi-resistant bacteria and free resistance genes through the soil. To test this, we irrigated soil cores once or twice with waste water only, or with waste water added with sulfamethoxazole (SMX) and ciprofloxacin (CIP). The treatments also contained a dye to stain the water flow paths and allowed to sample these separately from unstained bulk soil. The fate of SMX and CIP was assessed by sorption experiments, leachate analyses and the quantification of total and extractable SMX and CIP in soil. The abundance of resistance genes to SMX (sul1 and sul2) and to CIP (qnrB and qnrS) was quantified by qPCR. The sorption of CIP was larger than the dye and SMX. Ciprofloxacin accumulated exclusively in the water flow paths but the resistance genes qnrB and qnrS were not detectable. The SMX concentration in the water flow paths doubled the concentration of the bulk soil, as did the abundance of sul genes, particularly sul1 gene. These results suggest that flow paths do function as hotspots for the accumulation of antibiotics and trigger the formation of resistance genes in soil. Their dissemination also depends on the mobility of the antibiotic, which was much larger for SMX than for CIP.201829874749
7560160.9996The effect of bacterial functional characteristics on the spread of antibiotic resistance genes in Expanded Granular Sludge Bed reactor treating the antibiotic wastewater. To explore the fate and spreading mechanism of antibiotics resistance genes (ARGs) in antibiotics wastewater system, a laboratory-scale (1.47 L) Expanded Granular Sludge Bed (EGSB) bioreactor was implemented. The operating parameters temperature (T) and hydraulic retention time (HRT) were mainly considered. This result showed the removal of ARGs and COD was asynchronous, and the recovery speed of ARGs removal was slower than that COD removal. The decreasing T was attributed to the high growth rate of ARGs host bacteria, while the shortened HRT could promote the horizontal and vertical gene transfer of ARGs in the sludge. The analysis result of potential bacterial host showed more than half of the potential host bacteria carried 2 or more ARGs and suggested an indirect mechanism of co-selection of multiple ARGs. Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) was used to investigate the functional characteristics of bacterial community. This result showed the bacterial functional genes contributed 40.41% to the abundance change of ARGs in the sludge, which was higher that of bacterial community. And the function genes of "aromatic hydrocarbon degradation", "Replication, recombination and repair proteins" and "Flagellar assembly" were mainly correlated with the transfer of ARGs in the sludge. This study further revealed the mechanism of ARGs spread in the EGSB system, which would provide new ideas for the development of ARGs reduction technology.202134488144
7581170.9996Enhanced performance of anaerobic digestion of cephalosporin C fermentation residues by gamma irradiation-induced pretreatment. Antibiotic fermentation residues is a hazardous waste due to the existence of residual antibiotics and antibiotic resistance genes (ARGs), probably leading to the induction and spread of antibiotic resistant bacteria (ARB) in the environment, which could pose potential harm to the ecosystem and human health. It is urgent to develop an effective technology to remove the residual antibiotics and ARGs. In this study, the anaerobic digestion combined with gamma irradiation was applied for the disposal and utilization of cephalosporin C fermentation residues. The experimental results showed that the antibacterial activities of cephalosporin C against Staphylococcus aureus were significantly decreased after anaerobic digestion. The removal of tolC, a multidrug resistant gene, was improved up to 100% by the combination of gamma irradiation and anaerobic digestion compared to solely anaerobic digestion process, which may be due to the changes of microbial community structures induced by gamma irradiation.202031590081
7445180.9996Efficient removal of antibiotic resistance genes and of enteric bacteria from reclaimed wastewater by enhanced Soil Aquifer Treatments. Soil Aquifer Treatment (SAT) is a robust technology to increase groundwater recharge and to improve reclaimed water quality. SAT reduces dissolved organic carbon, contaminants of emerging concern, nutrients, and colloidal matter, including pathogen indicators, but little is known about its ability to reduce loads of antibiotic resistance genes (ARGs) from reclaimed waters. Here we test six pilot SAT systems to eliminate various biological hazards from the secondary effluents of a wastewater treatment plant (WWTP), equipped with reactive barriers (RBs) including different sorptive materials. Using flow cytometry, qPCR and 16S rRNA gene amplicon sequencing methods, we determined that all six SAT systems reduced total loads of bacteria by 80 to 95 % and of clinically relevant ARGs by 85 to 99.9 %. These efficiencies are similar to those reported for UV/oxidation or membrane-based tertiary treatments, which require much more energy and resources. The presence and composition of reactive barriers, the season of sampling (June 2020, October 2020, and September 2021), or the flow regime (continuous versus pulsating) did not affect ARG removal efficiency, although they did alter the microbial community composition. This suggests that an adequate design of the SAT reactive barriers may significantly increase their performance. Under a mechanistic point of view, we observed an ecological succession of bacterial groups, linked to the changing physical-chemical conditions along the SAT, and likely correlated to the removal of ARGs. We concluded that SAT is as cost-efficient technology able to dramatically reduce ARG loads and other biological hazards from WWTP secondary effluents.202439244046
7201190.9996Evolution of microbial community and drug resistance during enrichment of tetracycline-degrading bacteria. Recently, the microbial degradation of tetracycline has been widely reported. However, its potential risks in treating wastewater containing high concentrations of tetracycline have not been fully evaluated. In this study, the evolution of the microbial community and drug resistance was traced during the enrichment of tetracycline-degrading bacteria. The results showed that some minor compositions such as Shewanella, Bacillus, and Pseudomonas in the seed sludge became the predominant genera in the enrichment cultures when continuously using tetracycline as the sole carbon source, especially some possible pathogenic bacteria increased significantly in this process. The abundances of most TRGs/16S rDNA were increased after enrichment, although the relative abundance of tetA and tetL genes decreased to some extent. From the enrichment culture, 7 predominant tetracycline-degrading strains were isolated, of which TD-1 (Bacillus) and TD-5 (Shewanella) presented high degradation efficiencies (6-day degradation rate > 95%, half-life period of tetracycline ≈ 24 h). In addition, multiple TRGs, mobile genetic elements (MGEs) and even gene cassettes were found in each tetracycline-degrading isolate. The findings suggested that some risks such as the pathogenicity of isolates and the spread of ARGs should be considered when the biodegradation method is used to treat wastewater polluted with high concentrations of tetracycline.201930660087