Transcriptional Activity of Arsenic-Reducing Bacteria and Genes Regulated by Lactate and Biochar during Arsenic Transformation in Flooded Paddy Soil. - Related Documents




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854201.0000Transcriptional Activity of Arsenic-Reducing Bacteria and Genes Regulated by Lactate and Biochar during Arsenic Transformation in Flooded Paddy Soil. Organic substrates and biochar are important in controlling arsenic release from sediments and soils; however, little is known about their impact on arsenic-reducing bacteria and genes during arsenic transformation in flooded paddy soils. In this study, microcosm experiments were established to profile transcriptional activity of As(V)-respiring gene (arrA) and arsenic resistance gene (arsC) as well as the associated bacteria regulated by lactate and/or biochar in anaerobic arsenic-contaminated paddy soils. Chemical analyses revealed that lactate as the organic substrate stimulated microbial reduction of As(V) and Fe(III), which was simultaneously promoted by lactate+biochar, due to biochar's electron shuttle function that facilitates electron transfer from bacteria to As(V)/Fe(III). Sequencing and phylogenetic analyses demonstrated that both arrA closely associated with Geobacter (>60%, number of identical sequences/number of the total sequences) and arsC related to Enterobacteriaceae (>99%) were selected by lactate and lactate+biochar. Compared with the lactate microcosms, transcriptions of the bacterial 16S rRNA gene, Geobacter spp., and Geobacter arrA and arsC genes were increased in the lactate+biochar microcosms, where transcript abundances of Geobacter and Geobacter arrA closely tracked with dissolved As(V) concentrations. Our findings indicated that lactate and biochar in flooded paddy soils can stimulate the active As(V)-respiring bacteria Geobacter species for arsenic reduction and release, which probably increases arsenic bioavailability to rice plants.201829188998
791110.9995Biochar induced inhibitory effects on intracellular and extracellular antibiotic resistance genes in anaerobic digestion of swine manure. Distribution of intracellular (iARGs) and extracellular ARGs (eARGs) in manure anaerobic digestion (AD) process coupled with two types of biochar (BC and BP) were investigated. And the effects of biochar on the conjugation transfer of ARGs were explored by deciphering the interaction of biochar with bacterial stress responses, physiological metabolism and antibiotic resistances. Results showed that AD process could effectively remove all the detected eARGs with efficiency of 47.4-98.2%. The modified biochar (BP) with larger specific surface area (SSA) was propitious to decrease the absolute copy number of extracellular resistance genes. AD process could effectively remove iARGs by inhibiting the growth of host bacteria. The results of structural equation models (SEM) indicated that biochar put indirect influences on the fate of ARGs (λ = -0.23, P > 0.05). Analysis on oxidative stress levels, antioxidant capacity, DNA damage-induced response (SOS) response and energy generation process demonstrated that biochar induced the oxidative stress response of microorganisms and enhanced the antioxidant capacity of bacteria. The elevated antioxidant capacity negatively affected SOS response, amplified cell membrane damage and further weakened the energy generation process, resulted in the inhibition of horizontal transfer of ARGs.202235609652
789220.9994Nitrite Production by Nitrifying Bacteria in Urban Groundwater Used in a Chlorinated Public Bath System in Japan. In contrast to pathogens, the effects of environmental microbes on the water quality in baths have not yet been examined in detail. We herein focused on a public bath in which groundwater was pumped up as bath water and disinfected by chlorination. Ammonia in groundwater is oxidized to nitrite, thereby reducing residual chlorine. A batch-culture test and bacterial community ana-lysis revealed that ammonia-oxidizing bacteria accumulated nitrite and had higher resistance to chlorination than nitrite-oxidizing bacteria. These results demonstrate that the difference in resistance to chlorination between ammonia-oxidizing and nitrite-oxidizing bacteria may lead to the accumulation of nitrite in baths using groundwater.202236198516
798430.9994Distinct response of nitrogen metabolism to exogenous cadmium (Cd) in river sediments with and without Cd contamination history. The role of metal resistance on nitrogen metabolism function and community resilience against Cd is important for elucidating the evolutionary dynamics of key ecological functions in river ecosystems. In this study, the response of nitrogen transforming function to Cd exposure in river sediments from the Yangtze River Basin with varying levels of heavy metal contamination history (Cd-contaminated and Cd-free sediments) was compared to understand how Cd influenced nitrogen metabolism under varying metal resistance conditions. The results showed that chronic and persistent Cd pollution of sediments caused an elevation of transport efflux metal resistance genes (MRGs) and a reduction in the uptake MRGs, leading to a stronger tolerance to Cd for Cd-contaminated sediment than Cd-free ones. Specifically, denitrification, anaerobic ammonium oxidation (anammox) and dissimilatory nitrate reduction to ammonium (DNRA) respectively responded to Cd through different mechanisms. Exogenous Cd (5-100 mg kg(-1)) influenced denitrification rates (-70 %-100 % deviation to control group) by regulating key genera (Thiobacillus, Magnetospirillum, Sideroxydans etc.) and gene clusters for denitrification. Both adaptive nature of anammox bacteria and co-regulation of key genera (Candidatus_Scalindua, Candidatus_Jettenia, Planctomyces etc.) and gene hzsA were drivers of differential responses in sediments from various contamination history. Environmental factors rather than contamination history, key genera or genes were probably critical ones determining Cd-resistance in DNRA, being more tolerant to Cd in sediments with higher TOC and NH(4)(+). Stimulation of N(2)O reduction process (genera Gemmatimonas and Gemmatirosa and genes nosZ) in Cd-contaminated sediments by exogenous Cd lowered N(2)O emission risk, whereas the reverse was true for Cd-free sediments. These results enrich our understanding about the linkages among MRGs and nitrogen reduction functions in river.202539793158
795340.9994Rapid impact of phenanthrene and arsenic on bacterial community structure and activities in sand batches. The impact of both organic and inorganic pollution on the structure of soil microbial communities is poorly documented. A short-time batch experiment (6 days) was conducted to study the impact of both types of pollutants on the taxonomic, metabolic and functional diversity of soil bacteria. For this purpose sand spiked with phenanthrene (500 mg kg(-1) sand) or arsenic (arsenite 0.66 mM and arsenate 12.5 mM) was supplemented with artificial root exudates and was inoculated with bacteria originated from an aged PAH and heavy-metal-polluted soil. The bacterial community was characterised using bacterial strain isolation, TTGE fingerprinting and proteomics. Without pollutant, or with phenanthrene or arsenic, there were no significant differences in the abundance of bacteria and the communities were dominated by Pseudomonas and Paenibacillus genera. However, at the concentrations used, both phenanthrene or arsenic were toxic as shown by the decrease in mineralisation activities. Using community-level physiological profiles (Biolog Ecoplates™) or differential proteomics, we observed that the pollutants had an impact on the community physiology, in particular phenanthrene induced a general cellular stress response with changes in the central metabolism and membrane protein synthesis. Real-time PCR quantification of functional genes and transcripts revealed that arsenic induced the transcription of functional arsenic resistance and speciation genes (arsB, ACR3 and aioA), while no transcription of PAH-degradation genes (PAH-dioxygenase and catechol-dioxygenase) was detected with phenanthrene. Altogether, in our tested conditions, pollutants do not have a major effect on community abundance or taxonomic composition but rather have an impact on metabolic and functional bacterial properties.201424189653
673650.9994Biotic pathways of reciprocal responses between antibiotic resistance genes and inorganic nitrogen cycling genes in amoxicillin-stressed compost ecosystems. This study explored the transformation of inorganic nitrogen, the expression levels of antibiotic resistance genes (ARGs), and the regulatory mechanisms of key species on ARGs and inorganic nitrogen cycling genes (INCGs) under different levels of amoxicillin (AMX) stress. High level of AMX inhibited the accumulation of NH(4)(+)-N, which increased by 531 % relative to the initial. Moreover, AMX to some extent increased the levels of nirS and nirK, which could potentially result in nitrogen loss and the accumulation of NO(2)(-). Actinobacteria might serve as potential hosts for ARGs during sludge composting. This stress induced a complex response between INCGs and ARGs more complex due to key species. Under high-level AMX pressure, most species associated with ARGs likely derived from nitrogen cycling functional species. To conclude, high levels of AMX stress might lead to nitrogen cycling imbalance and the dissemination of antibiotic resistance genes in composting systems.202438387840
790960.9994Simultaneous efficient removal of tetracycline and mitigation of antibiotic resistance genes enrichment by a modified activated sludge process with static magnetic field. To address the increasing issue of antibiotic wastewater, this study applied a static magnetic field (SMF) to the activated sludge process to increase the efficiency of tetracycline (TC) removal from swine wastewater and to reveal its enhanced mechanisms. The results demonstrated that the SMF-modified activated sludge process could achieve almost complete TC removal at sludge loading rates of 0.3 mg TC/g MLSS/d. Analysis of zeta potential and extracellular polymeric substances composition of the activated sludge revealed that SMF increased electrostatic interactions between TC and activated sludge and made activated sludge has much more binding sites, finally resulting in the increased TC biosorption. Metagenomic analysis showed that SMF promoted the enrichment of ammonia-oxidizing bacteria, TC-degrading bacteria, and aromatic compounds-degrading bacteria; it also enhanced ammonia monooxygenase- and cytochrome P450-mediated TC metabolism while upregulating functional genes associated with oxidase, reductase, and dehydrogenase - all contributing to increased TC biodegradation. Additionally, SMF mitigated the enrichment and spread of antibiotic resistance genes (ARGs) by decreasing the abundance of potential hosts of ARGs and inhibiting the upregulation of genes encoding ABC transporters and putative transposase. Based on these findings, this study demonstrates that magnetic field is an enhancement strategy with great potential to relieve the harmful impacts of the growing antibiotic wastewater problem on human health and the ecosystem.202439038424
854170.9994Insights into the response of anammox process to oxytetracycline: Impacts of static magnetic field. The long-term effects of oxytetracycline (OTC) with a high concentration on the anaerobic ammonium oxidation (Anammox) process were evaluated, and the role of static magnetic field (SMF) was further explored. The stress of OTC at 50 mg/L had little effect on the nitrogen removal of anammox process at the first 16 days. With the continuous addition of OTC and the increase of nitrogen loading, the OTC inhibited the nitrogen removal and anammox activity severely. During the 32 days of recovery period without OTC addition, the nitrogen removal was further deteriorated, indicating the inhibition of OTC on anammox activity was irreversible and persistent. The application of SMF alleviated the inhibition of OTC on anammox to some extent, and the specific anammox activity was enhanced by 47.1% compared to the system without SMF during the OTC stress stage. Antibiotic efflux was the major resistance mechanism in the anammox process, and tetA, tetG and rpsJ were the main functional antibiotic resistance genes. The addition of OTC weakened the metabolic interactions between the anammox bacteria and the symbiotic bacteria involved in the metabolism of cofactors and secondary metabolites, leading to the poor anammox activity. The adaptability of microbes to the OTC stress was improved by the application of SMF, which can enhance the metabolic pathways related to bacterial growth and resistance to environmental stress.202337586490
798380.9993Insights into the associations of copper and zinc with nitrogen metabolism during manure composting with shrimp shell powder. The application of shrimp shell powder (SSP) in manure composting can promote the maturation of compost and reduce the associated environmental risk. This study investigated the response of adding SSP at different levels (CK: 0, L: 5%, M: 10%, and H: 15%) on heavy metal resistance genes (MRGs), nitrogen functional genes, enzymes, and microorganisms. SSP inhibited nitrification and denitrification via decreasing the abundances of functional genes and key enzymes related to Cu, Zn, and MRGs. The nitrate reductase and nitrous-oxide reductase in the denitrification pathway were lower under H. Phylogenetic trees indicated that Burkholderiales sp. had strong relationships with OTU396 and OTU333, with important roles in the nitrogen cycle and plant growth. Redundancy analysis and structural equation modeling showed the complex response between heavy metal and nitrogen that bio-Cu and bio-Zn had positive significantly relationships with nirK-type and amoA-type bacteria, and amoA-type bacteria might be hotspot of cueO.202234861387
798190.9993Dissolved biochar eliminates the effect of Cu(II) on the transfer of antibiotic resistance genes between bacteria. The proliferation of antibiotic resistance genes (ARGs) has posed significant risks to human and environmental health. Research has confirmed that Cu(II) could accelerate the conjugative transfer of ARGs between bacteria. This study found that adding dissolved biochar effectively weakened or eliminated the Cu(II)-facilitated efficient transfer of ARGs. The efficiency of conjugative transfer was promoted after treatment with Cu(II) (0.05 mg/L) or dissolved biochar at a pyrolysis temperature of 300 °C. When exposed to the combination of Cu(II) and dissolved biochar, the transfer frequency was significantly reduced; this occurred regardless of the Cu(II) concentration or pyrolysis temperature of dissolved biochar. In particular, when the Cu(II) concentration exceeded 0.5 mg/L, the transfer efficiency was entirely inhibited. Gene expression analysis indicated that different treatments affect transfer efficiency by regulating the expression of three global regulatory genes: korA, korB, and trbA. Among them, humic acid repressed the expression of these genes; however, Cu(II) formed complex with the humic acid-like components, gradually weakening the inhibitive effect of these components. The promotion of low molecule organic matters dominated, resulting in a dynamic decline in the transfer efficiency. This study provides a new environmental contaminant treatment approach to eliminate the heavy metal-facilitated transfer of ARGs between bacteria.202234583164
8544100.9993Closed fixed-bed bacteria-algae biofilm reactor: A promising solution for phenol containing wastewater treatment and resource transformation. This study focuses on treating phenolic wastewater with a novel closed fixed-bed bacteria-algae biofilm reactor (CF-BABR) to enhance resource transformation for phenolic substances. The CF-BABR showed strong impact - load resistance and stable degradation efficiency, fully degrading phenolic compounds at concentrations from 0 to 150 mg/L. From the inflow to the outflow, the effective sequences, abundance, and diversity of bacteria decreased. Chlorobaculum was the dominant bacterium for phenolic pollutant degradation. The abundance of fungi decreased gradually, while their diversity increased. Kalenjinia and Cutaneotrichosporon played a synergistic role in reducing pollutant toxicity. The high - concentration pollutants at the influent led to a higher abundance of microalgal communities, and Scenedesmaceae became the most dominant algal family, which was positively correlated with the degradation of phenolic compounds. Functional gene prediction indicated that the abundance of functional genes in bacteria decreased overall along the wastewater flow. Carbohydrate metabolism and amino acid metabolism were the most active secondary pathways. In fungi, the predicted gene functions had the highest abundance in the upstream region. Metabolic intermediates such as organic acids and derivatives, lipids and lipid - like molecules, and carboxylic acids and derivatives demonstrated the degradation effect of CF-BABR on phenolic compounds.202540194331
8574110.9993Impact of different manure-derived dissolved organic matters on the fate of arsenic-antibiotic in co-contaminated paddy soils. Manure application increases the transfer risk of antibiotic resistance to farmland. Especially, its impact remains unclear when it occurs in arsenic (As)-contaminated paddy soils, which is considered as a global environmental problem. In this work, we investigated the fate of antibiotic resistance genes (ARGs) in As-antibiotic co-contaminated paddy soils under the application of manure from different sources (pig manure, cow dung, and chicken manure). Differences in the aliphatic carbon and electron-donating capacities of these dissolved organic matters (DOM) regulated the transformation of iron and As by both biotic and abiotic processes. The regulation by pig manure was stronger than that by cow dung and chicken manure. DOM regulation increased the abundance of As-related functional genes (arsC, arrA, aioA, and arsM) in the soil and accelerated the transformation of As speciation, the highest proportion of As(III) being 45%-61%. Meanwhile, the continuous selection pressure provided by the highly toxic As(III) increased the risk of ARGs and mobile genetic elements (MGEs) via horizontal gene transfer. As-resistant bacteria, including Bacillus, Geobacter, and Desulfitobacterium, were finally considered as potential host bacteria for ARGs and MGEs. In summary, this study clarified the synergistic mechanism of As-antibiotic on the fate of ARGs in co-contaminated paddy soils, and provided practical guidance for the proper application of organic fertilizers.202235491001
8514120.9993Graphene oxide influences transfer of plasmid-mediated antibiotic resistance genes into plants. As an emerging contaminant, antibiotic resistance genes (ARGs) are raising concerns about its significant threat to public health. Meanwhile, graphene oxide (GO), which also has a potential ecological damage with increasingly entering the environment, has a great influence on the transfer of ARGs. However, little is known about the effects mechanisms of GO on the migration of antibiotic resistance genes (ARGs) from bacteria into plants. In this study, we investigated the influence of GO on the transfer of ARGs carried by RP4 plasmids from Bacillus subtilis into rice plants. Our results showed that the presence of GO at concentrations ranging from 0 to 400 mg L(-1) significantly reduced the transfer of ARGs into rice roots by 13-71 %. Moreover, the migration of RP4 from the roots to aboveground parts was significantly impaired by GO. These effects may be attributed to several factors. First, higher GO concentrations led to low pH in the culture solution, resulting in a substantial decrease in the number of antibiotic-resistant bacteria. Second, GO induced oxidative stress in rice, as indicated by enhanced Evans blue dye staining, and elevated levels of malondialdehyde, nitric oxide, and phenylalanine ammonia-lyase activity. The oxidative stress negatively affected plant growth, as demonstrated by the reduced fresh weight and altered lignin content in the rice. Microscopic observations confirmed the entry of GO into root cells but not leaf mesophyll cells. Furthermore, potential recipients of RP4 plasmid strains in rice after co-cultivation experiments were identified, including Bacillus subtilis, Bacillus amyloliquefaciens, and Bacillus cereus. These findings clarify the influence of GO on ARGs in the bacteria-plant system and emphasize the need to consider its potential ecological risks.202437979849
7960130.9993Diversity evolution of functional bacteria and resistance genes (CzcA) in aerobic activated sludge under Cd(II) stress. An activated sludge sequencing batch reactor (SBR) was used to treat divalent cadmium (Cd(II)) wastewater for 60 d to investigate the overall treatment performance, evolution of the bacterial community, and abundance of the Cd(II) resistance gene CzcA and shifts in its potential host bacteria. During stable operation with a Cd(II) concentration of 20 mg/L, the average removal efficiencies of Cd(II) and chemical oxygen demand (COD) were more than 85% and that of total phosphorus was greater than 70%, while the total nitrogen (TN) was only about 45%. The protein (PN) content in the extracellular polymeric substances (EPS) increased significantly after Cd(II) addition, while polysaccharides displayed a decreasing trend (p < 0.05), indicating that EPS prefer to release PN to adsorb Cd(II) and protect bacteria from damage. Three-dimensional fluorescence spectral analysis showed that fulvic acid-like substances were the most abundant chemical components of EPS. The addition of Cd(II) adversely affected most denitrifying bacteria (p < 0.05), which is consistent with the low TN removal. In addition, quantitative polymerase chain reaction analysis revealed that CzcA gene abundance decreased as the Cd(II) concentration increased, possibly because expression of the CzcA gene was inhibited by Cd(II) stress. The majority of CzcA gene sequences were carried by Pseudomonas, making it the dominant genus among Cd(II)-resistant bacteria.201931514000
8819140.9993Responses of Bacillus sp. under Cu(II) stress in relation to extracellular polymeric substances and functional gene expression level. The production and composition of extracellular polymeric substances (EPS), as well as the EPS-related functional resistance genes and metabolic levels of Bacillus sp. under Cu(II) stress, were investigated. EPS production increased by 2.73 ± 0.29 times compared to the control when the strain was treated with 30 mg L(-1) Cu(II). Specifically, the polysaccharide (PS) content in EPS increased by 2.26 ± 0.28 g CDW(-1) and the PN/PS (protein/polysaccharide) ratio value increased by 3.18 ± 0.33 times under 30 mg L(-1) Cu(II) compared to the control. The increased EPS secretion and higher PN/PS ratio in EPS strengthened the cells' ability to resist the toxic effect of Cu(II). Differential expression of functional genes under Cu(II) stress was revealed by Gene Ontology pathway enrichment analysis and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis. The enriched genes were most obviously upregulated in the UMP biosynthesis pathway, the pyrimidine metabolism pathway, and the TCS metabolism pathway. This indicates an enhancement of EPS regulation-related metabolic levels and their role as a defense mechanism for cells to adapt to Cu(II) stress. Additionally, seven copper resistance genes were upregulated while three were downregulated. The upregulated genes were related to the heavy metal resistance, while downregulated genes were related to cell differentiation, indicating that the strain had initiated an obvious resistance to Cu(II) despite its severe cell toxicity. These results provided a basis for promoting EPS-regulated associated functional genes and the application of gene-regulated bacteria in heavy metal-containing wastewater treatment.202337195605
7515150.9993Bacterial metal resistance genes and metal bioavailability in contaminated sediments. In bacteria a metal may be defined as bioavailable if it crosses the cytoplasmic membrane to reach the cytoplasm. Once inside the cell, specific metal resistance systems may be triggered. In this research, specific metal resistance genes were used to estimate metal bioavailability in sediment microbial communities. Gene levels were measured by quantitative PCR and correlated to metals in sediments using five different protocols to estimate dissolved, particle-adsorbed and occluded metals. The best correlations were obtained with czcA (a Cd/Zn/Co efflux pump) and Cd/Zn adsorbed or occluded in particles. Only adsorbed Co was correlated to czcA levels. We concluded that the measurement of czcA gene levels by quantitative PCR is a promising tool which may complement the classical approaches used to estimate Cd/Zn/Co bioavailability in sediment compartments.201424662000
8543160.9993Soil bacteria, genes, and metabolites stimulated during sulfur cycling and cadmium mobilization under sodium sulfate stress. Sodium sulfate stress is known to improve cadmium (Cd) mobilization in soil and microbial sulfur oxidation, Cd resistance, and the accumulation of stress tolerance-associated metabolites has been correlated with increased soil Cd availability and toxicity. In this study, aerobic soil microcosms with Cd-contamination were stimulated with sodium sulfate to investigate its effects on soil microbial community structure, functional genes, and associated metabolite profiles. Metagenomic analysis revealed that sulfur oxidizing and Cd-resistant bacteria carried gene clusters encoding sox, dsr, and sqr genes, and znt, czc, and cad genes, respectively. Exposure to sodium sulfate resulted in the reprogram of soil metabolites. In particular, intensification of sulfur metabolism triggered an up-regulation in the tricarboxylic acid (TCA) cycle, which promoted the secretion of carboxylic acids and their precursors by soil bacteria. The accumulation of organic acids induced in response to high sodium sulfate dosages potentially drove an observed increase in Cd mobility. Pseudomonas and Erythrobacter spp. exhibited a high capacity for adaptation to heavy metal- or sulfur-induced stress, evident by an increased abundance of genes and metabolites for sulfur cycling and Cd resistance. These results provide valuable insights towards understanding the microbial mechanisms of sulfur transformation and Cd dissolution under saline stress.202134214562
8538170.9993Metagenomic ecotoxicity assessment of trace difenoconazole on freshwater microbial community. Difenoconazole, a typical triazole fungicide, inhibits the activity of cytochrome P450 enzyme in fungi, and is extensively used in protecting fruits, vegetables, and cereal crops. However, reports elucidating the effects of difenoconazole on aquatic microbial communities are limited. Our study showed that difenoconazole promoted microalgae growth at concentrations ranging from 0.1 to 5 μg/L, which was similar with its environmental residual concentrations. Metagenomic analysis revealed that the aquatic microbial structure could self-regulate to cope with difenoconazole-induced stress by accumulating bacteria exhibiting pollutant degrading abilities. In the short-term, several functional pathways related to xenobiotic biodegradation and analysis were upregulated to provide ability for aquatic microbial community to process xenobiotic stress. Moreover, most disturbed ecological functions were recovered due to the redundancy of microbial communities after prolonged exposure. Furthermore, the risks associated with the dissemination of antibiotic resistance genes were enhanced by difenoconazole in the short-term. Overall, our study contributes to a comprehensive understanding of the difenoconazole-induced ecological impacts and the behavior of aquatic microbial communities that are coping with xenobiotic stress.202235090847
8535180.9993Metagenomics combined with DNA-based stable isotope probing provide comprehensive insights of active triclosan-degrading bacteria in wastewater treatment. The biotransformation of triclosan (TCS) during wastewater treatment occurred frequently, while little researches are known the identity of microorganisms involved in the biodegradation process. In this work, DNA-based stable isotope probing (DNA-SIP) was occupied to investigate the TCS assimilation microbes originated from a full-scale cyclic activated sludge system in Beijing. Results of TCS removal pathway showed that the TCS removal in nitrification process was mainly contributed by the metabolism of heterotrophic bacteria, accounting for about 18.54%. DNA-SIP assay indicated that Sphingobium dominated the degradation of TCS. Oligotyping analysis further indicated that oligotype GCTAAT and ATGTTA of Sphingobium played important roles in degrading TCS. Furthermore, the Kyoto Encyclopedia of Genes and Genomes functional abundance statistics based on PICRUSt2 showed that glutathione transferase was the most prevalent enzyme involved in TCS metabolism, and TCS might be removed through microbial carbon metabolism. Metagenomics made clear that Sphingobium might play irrelevant role on the propagation of antibiotics resistance genes (ARGs), even though, it could degrade TCS. Thauera and Dechloromonas were identified as the key hosts of most ARGs. This study revealed the potential metabolic pathway and microbial ecology of TCS biodegradation in nitrification process of wastewater treatment system.202133069997
7565190.9993Microalgae Enhances the Adaptability of Epiphytic Bacteria to Sulfamethoxazole Stress and Proliferation of Antibiotic Resistance Genes Mediated by Integron. The transmission of ARGs in the microalgae-associated epiphytic bacteria remains unclear under antibiotic exposure, apart from altering the microbial community structure. In this study, Chlorella vulgaris cocultured with bacteria screened from surface water was examined to explore the spread of ARGs in the presence of sulfamethoxazole (SMX). The extracellular polymers released by Chlorella vulgaris could reduce antibiotic-induced collateral damage to bacteria, thus increasing the diversity of the microalgae-associated epiphytic bacteria. The abundances of sul1 and intI1 in the phycosphere at 1 mg/L SMX dose increased by 290 and 28 times, respectively. Metagenomic sequencing further confirmed that SMX bioaccumulation stimulated the horizontal transfer of sul1 mediated by intI1 in the microalgae-associated epiphytic bacteria, while reactive oxygen species (ROS)-mediated oxidative stress induced the SOS response and thus enhanced the transformation of sul1 in the J group. This is the first study to verify that microalgae protect bacteria from antibiotic damage and hinder the spread of ARGs mediated by SOS response, while the transfer of ARGs mediated by integron is promoted due to the bioaccumulation of SMX in the phycosphere. The results contribute to present comprehensive understanding of the risk of ARG proliferation by the presence of emerging contaminants residues in river.202439417646