Adding a complex microbial agent twice to the composting of laying-hen manure promoted doxycycline degradation with a low risk on spreading tetracycline resistance genes. - Related Documents




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803401.0000Adding a complex microbial agent twice to the composting of laying-hen manure promoted doxycycline degradation with a low risk on spreading tetracycline resistance genes. Poultry manure is a reservoir for antibiotics and antibiotic resistance genes and composting is an effective biological treatment for manure. This study explored the effect of using two methods of adding a complex microbial agent to the composting of laying-hen manure on doxycycline degradation and tetracycline resistance genes elimination. The results showed that incorporating a complex microbial agent at 0.8% (w/w) on the 0(th) and 11th day (group MT2) effectively degraded doxycycline with a final degradation rate of 46.83 ± 0.55%. The half-life of doxycycline in this group was 21.90 ± 0.00 days and was significantly lower than that of group MT1 (1.6% (w/w) complex microbial agent added on the 0(th) day) and group DT (compost without complex microbial agent). But there was no significant difference in the final degradation rate of doxycycline between group DT and group MT1. The addictive with the complex microbial agent changed the microbial community structure. Bacteroidetes, Firmicutes and Proteobacteria were the dominant phyla during composting. Aerococcus, Desemzia, Facklamia, Lactobacillus, Streptococcus, and Trichococcus were the bacteria related to the degradation of doxycycline. Moreover, the incorporation of a complex microbial agent could decrease the risk on spreading tetracycline resistance genes. The single addition promoted the elimination of tetM, whose possible hosts were Enterococcus, Lactobacillus, Staphylococcus, and Trichococcus. Adding the complex microbial agent twice promoted the elimination of tetX, which was related to the low abundance of Chryseobacterium, Flavobacterium and Neptunomonas in group MT2. Redundancy analysis showed that the bacterial community, residual doxycycline and physiochemical properties have a potential effect on the variation in tetracycline resistance genes levels. Overall, adding the complex microbial agent twice is an effective measure to degrade doxycycline.202032806409
803710.9997Dosage effects of lincomycin mycelial residues on lincomycin resistance genes and soil microbial communities. Lincomycin mycelial residues (LMRs) are one kind of byproduct of the pharmaceutical industry. Hydrothermal treatment has been used to dispose of them and land application is an attractive way to reuse the treated LMRs. However, the safe dose for soil amendment remains unclear. In this study, a lab-scale incubation experiment was conducted to investigate the influence of the amendment dosage on lincomycin resistance genes and soil bacterial communities via quantitative PCR and 16S rRNA sequencing. The results showed that introduced lincomycin degraded quickly in soil and became undetectable after 50 days. Degradation rate of the high amendment amount (100 mg kg(-1)) was almost 4 times faster than that of low amendment amount (10 mg kg(-1)). Moreover, the introduced LMRs induced the increase of lincomycin resistance genes after incubation for 8 days, and two genes (lmrA and lnuB) showed a dosage-related increase. For example, the abundance of gene lmrA was 17.78, 74.13 and 128.82 copies g(-1) soil for lincomycin concentration of 10, 50 and 100 mg kg(-1), respectively. However, the abundance of lincomycin resistance genes recovered to the control level as the incubation period extended to 50 days, indicating a low persistence in soil. In addition, LMRs application markedly shifted the bacterial composition and significant difference was found between control soil, 10 mg kg(-1) and 50 mg kg(-1) lincomycin amended soil. Actually, several genera bacteria were significantly related to the elevation of lincomycin resistance genes. These results provided a comprehensive understanding of the effects of lincomycin dosage on the fate of resistance genes and microbial communities in LMRs applied soil.202031662263
801220.9997Sensitive response mechanism of ARGs and MGEs to initial designed temperature during swine manure and food waste co-composting. The rapid aerobic composting process has been used to reduce organic wastes, but the associated risks of antibiotic resistance genes (ARGs) need to evaluate in an efficient way. The primary objective of this work was to explore the underlying mechanism of initial adjustment in composting temperature on the variation of ARGs, mobile genetic elements (MGEs), and microbial composition during co-composting. The co-composting was initially externally heated (T2) for 5 days. The results showed that ARGs abundance in conventional composting (T1) was reduced by 49.36%, while multidrug was enriched by 86.16% after a period of 30 days. While in T2 ARGs were removed by 79.46% particularly the fraction of sulfonamide, multidrug, and vancomycin resistance genes were >90% without rebounding of any ARGs. Whereas, MGEs were reduced by 68.12% and 93.62% in T1 and T2, while the half-lives of ARGs and MGEs were lower in T2 compared to T1 (86.3%,86.7%). T2 also affected the metabolism function by regulating carbohydrate metabolism (9.62-10.39%) and amino acid metabolism (9.92-10.93%). Apart from this, the potential human pathogenic bacteria Pseudomonas was reduced by 90.6% in T2 and only 32.9% in T1 respectively. Network analysis showed that Ureibacillus, Weissella, Corynebacterium, Escherichia-Shigella, Acinetobacter were the main host of multiple genes. Structural equation models exhibited that bacterial communities were mainly responsible for the enrichment of ARGs in T1, whereas, it was directly affected by MGEs in T2. Similarly, ARGs variation was directly related to composting temperature. With this simple strategy, ARGs associated risk can be significantly reduced in composting.202336208781
801430.9997Contributions of the microbial community and environmental variables to antibiotic resistance genes during co-composting with swine manure and cotton stalks. Understanding the main drivers that affect the spread of antibiotic resistance genes (ARGs) during the composting process is important for the removal of ARGs. In this study, three levels of tylosin (25, 50, and 75 mg kg(-1) on a dry weight basis) were added to swine manure plus a control, which was composted with cotton stalks. Each treatment was repeated in triplicate and the ARG profiles were determined with different levels of tylosin. The top 35 genera and ARGs profiles were clustered together based on the composting time. Combined composting parameters (temperature, pH, NH(4)(+)-N, NO(3)-N, and moisture content) accounted for 78.4% of the total variation in the changes in the potential host bacteria. In addition, the selected five composting parameters and six phyla (including 25 potential host bacterial genera) explained 46.9% and 30.7% of the variation in the ARG profiles according to redundancy analysis, respectively. The variations in ARGs during the composting process were mainly affected by the dynamics of potential host bacteria rather than integrons and the selective pressure due to bio-Cu and bio-Zn.201829990821
809040.9997Swine Manure Composting With Compound Microbial Inoculants: Removal of Antibiotic Resistance Genes and Their Associations With Microbial Community. In this study, compound microbial inoculants, including three Bacillus strains and one Yeast strain, were inoculated into swine manure composting to explore the effects on antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs), microbial community structure, and pathogenic bacteria. The results indicated that the abundances of the detected ARGs ranged from 3.6 × 10(3) to 1.13 × 10(8) copies/g. The ARGs with the highest abundance was sul2, and the lowest was blaCTX. Composting removes most of the ARGs and MGEs by 22.8-99.7%. These ARGs were significantly reduced during the thermophilic phase of compost. The removal rate of ARGs at the different layers of compost pile was different as follows: middle layer > upper layer > lower layer. But some ARGs proliferated significantly in the maturation phase of compost, especially the sulfonamide resistance genes. Compound microbial inoculants increased the temperature of compost, accelerated water loss, nitrogen fixation, and increased the removal rate of β-lactamase resistance genes, the transposon gene tn916 and part of tetracycline resistance genes by 3.7-23.8% in compost. Compound microbial inoculants changed the community structure and increased the Bacillus abundance in the thermophilic phase of compost. And it was helpful for removing pathogens during composting. The addition of compound microbial inoculants causes the decrease of Firmicutes and the increase of Bacteroidetes, which may be related to the removal and proliferation of ARGs.202033250880
719750.9997The response of copper resistance genes, antibiotic resistance genes, and intl1/2 to copper addition during anaerobic digestion in laboratory. Heavy metal pollution can serve as a selective pressure for antibiotic resistance genes in polluted environments. Anaerobic fermentation, as a recommended wastewater treatment method, is an effective mitigation measure of antibiotic resistance diffusion. To explore the influence of copper on anaerobic fermentation, we exposed the fermentation substrate to copper in a laboratory setup. We found that the relative abundance of 8 genes (pcoD, tetT, tetA, tetB, tetO, qnrS, ermA and ermB) increased at the late stage of fermentation and their abundance was linked to copper content. Corynebacterium and Streptococcus were significantly positively correlated with ermA, ermB, tetA and tetB (P < 0.05). The relative abundance of tetT was significantly positively correlated with Terrisporobacter, Clostridium_sensu_stricto_1 and Turicibacter (P < 0.05). We screened 90 strains of copper resistant bacteria from blank, medium and high copper test groups on days 25, 31 and 37. The number of fragments carried by a single strain increased with time while intl1, ermA and ermB existed in almost all combinations of the multiple fragments we identified. The relative abundance of these three genes were linearly correlated with Corynebacterium and Streptococcus. The antibiotic resistance genes carried by class 1 integrons gradually increased with time in the fermentation system and integrons carrying ermA and ermB most likely contributed to host survival through the late stages of fermentation. The genera Corynebacterium and Streptococcus may be the primary carriers of such integrated mobile gene element and this was most likely the reason for their rebound in relative abundance during the late fermentation stages.202133418156
718960.9997Comparative effects of different antibiotics on antibiotic resistance during swine manure composting. This study explored commonly-used antibiotics (lincomycin, chlorotetracycline, sulfamethoxazole, and ciprofloxacin) and their collective effects on antibiotic resistance during composting. In the first 7 days, ciprofloxacin showed the greatest influence on the physicochemical factors among the studied antibiotics; the removal of antibiotic resistance genes (ARGs) in the multiple-antibiotic treatment was significantly less than single-antibiotic treatments; especially, the largest removal of ribosomal protection genes (tetW and tetO) occurred in single ciprofloxacin treatment. In the end of composting, similar removal ratio (29.71-99.79%) of ARGs was achieved in different treatments (p greater than 0.05); Chloroflexi became the main phylum and it was closely associated with ARGs removal based on the network analysis. Potential host bacteria of ARGs varied with different antibiotics; in particular, the presence of multiple antibiotics increased potential host bacteria of ermA, sul1 and tetO. Above all, collective effects of different antibiotics led to the enrichment of antibiotic resistance in the composting.202032712514
801370.9997New insight into fates of sulfonamide and tetracycline resistance genes and resistant bacteria during anaerobic digestion of manure at thermophilic and mesophilic temperatures. This study investigated the variations in antibiotic (sulfonamide and tetracycline) resistance genes (ARGs) and resistant bacteria (ARB) during manure anaerobic digestion (AD) at 35 ℃ and 55 ℃, and discussed the mechanisms of variations in ARGs. The AD lasted for 60 days, five ARGs and intI1 each decreased in abundance after AD at the thermophilic temperature, while only half decreased at the mesophilic temperature. On days 10, 30, and 60, sulfonamide and tetracycline ARB were screened on selective media. During thermophilic AD, ARB numbers reduced by 4-log CFUs per gram dry manure, but only by approximately 1-log CFU at the mesophilic temperature. However, ARB composition analysis showed that at either temperature, no significant reduction in identified ARB species was observed. Furthermore, 72 ARB clones were randomly selected to detect the ARGs they harbored, and the results showed that each ARG was harbored by various hosts, and no definitive link existed between ARGs and bacterial species. In addition, by comparison with the identified host by culture method, the host prediction results based on the correlation analysis between ARGs and the bacterial community was proven to be unreliable. Overall, these findings indicated that relationships between ARB and ARGs were intricate.202031685315
801880.9997Analysis for microbial denitrification and antibiotic resistance during anaerobic digestion of cattle manure containing antibiotic. This study investigated the effects of tylosin (0, 10, and 100 mg/kg dry weight) on the denitrification genes and microbial community during the anaerobic digestion of cattle manure. N(2) emissions were reduced and N(2)O emissions were increased by 10 mg/kg tylosin. Adding 100 mg/kg tylosin increased the emission of both N(2)O and N(2). The different responses of denitrifying bacteria and genes to tylosin may have been due to the presence of antibiotic resistance genes (ARGs). Network analysis indicated that denitrification genes and ARGs had the same potential host bacteria. intI1 was more important for the horizontal transfer of denitrification genes and ARGs during anaerobic digestion than intI2. The anaerobic digestion of manure containing tylosin may increase nitrogen losses and the associated ecological risk.201931326686
725290.9997Aerobic Composting and Anaerobic Digestion Decrease the Copy Numbers of Antibiotic-Resistant Genes and the Levels of Lactose-Degrading Enterobacteriaceae in Dairy Farms in Hokkaido, Japan. Efficient methods for decreasing the spread of antimicrobial resistance genes (ARGs) and transfer of antimicrobial-resistant bacteria (ARB) from livestock manure to humans are urgently needed. Aerobic composting (AC) or anaerobic digestion (AD) are widely used for manure treatment in Japanese dairy farms. To clarify the effects of AC and AD on antimicrobial resistance, the abundances of antimicrobial (tetracycline and cefazolin)-resistant lactose-degrading Enterobacteriaceae as indicator bacteria, copy numbers of ARGs (tetracycline resistance genes and β-lactamase coding genes), and concentrations of residual antimicrobials in dairy cow manure were determined before and after treatment. The concentration of tetracycline/cefazolin-resistant lactose-degrading Enterobacteriaceae was decreased over 1,000-fold by both AC and AD. ARGs such as tetA, tetB, and bla (TEM) were frequently detected and their copy numbers were significantly reduced by ∼1,000-fold by AD but not by AC. However, several ARG copies remained even after AD treatment. Although concentrations of the majority of residual antimicrobials were decreased by both AC and AD, oxytetracycline level was not decreased after treatment in most cases. In addition, 16S rRNA gene amplicon-based metagenomic analysis revealed that both treatments changed the bacterial community structure. These results suggest that both AC and AD could suppress the transmission of ARB, and AD could reduce ARG copy numbers in dairy cow manure.202134659165
8031100.9996Anaerobic Digestion of Tetracycline Spiked Livestock Manure and Poultry Litter Increased the Abundances of Antibiotic and Heavy Metal Resistance Genes. Anaerobic digestion is used for the treatment of animal manure by generating biogas. Heavy metals cause environmental pollutions and co-select for antimicrobial resistance. We evaluated the impact of mesophilic anaerobic digestion of cattle manure (CM), swine manure (SM) and poultry litter (PL) on the concentrations of seven tetracycline [tet(A), tet(B), tet(G), tet(M), tet(O), tet(Q), and tet(W)], macrolide [erm(B)], methicillin (mecA and mecC), copper (copB, pcoA, pcoD, and tcrB) and zinc (czrC) resistance genes, and three bacterial species (E. coli, Enterococcus spp. and Staphylococcus aureus). The total bacterial population and total abundance of the seven tet genes significantly increased in the three manure types after digestion. Concentration of tet(M) was strongly correlated with that of erm(B) and enterococci. As concentration of tetracyclines declined during anaerobic digestion, that of four tet genes (A, B, Q, and W) and 16S rRNA increased, that of tet(M) decreased, and that of tet(G) and tet(O) did not change. Concentrations of copB and pcoA did not change; while that of pcoD did not change in the PL, it increased in the SM and CM. While the concentration of enterococci remained unchanged in CM, it significantly increased in the PL and SM. Concentrations of tcrB significantly increased in the three manure types. While concentrations of S. aureus significantly increased in the CM and PL, that of SM was not affected. Concentrations of mecC significantly increased in all manure types after digestion; while mecA concentrations did not change in the SM, they significantly increased in CM and PL. While concentration of czrC remained low in the CM, it increased in the PL but declined in the SM. In conclusion, while mesophilic anaerobic digestion of animal manure decreased concentration of tetracyclines, it increased the concentrations of total bacteria, tet genes, E. coli, enterococci and S. aureus and methicillin resistance genes. It did not have any effect on concentrations of heavy metals; concentrations of heavy metal resistance genes either increased or remained unaffected depending on the animal species. This study showed the need for post-digestion treatments of animal manure to remove bacteria, antibiotic resistance genes, heavy metals and their resistance genes.202033391245
7190110.9996Dynamics 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
8091120.9996Changes in antibiotic resistance genes and mobile genetic elements during cattle manure composting after inoculation with Bacillus subtilis. This study explored the effects of Bacillus subtilis at four levels (0, 0.5%, 1%, and 2% w/w compost) on the variations in ARGs, mobile genetic elements (MGEs), and the bacterial community during composting. The composting process had a greater impact on ARGs than Bacillus subtilis. The main ARG detected was sul1. The addition of Bacillus subtilis at 0.5% reduced the relative abundances of ARGs, MGEs, and human pathogenic bacteria (by 2-3 logs) in the mature products. Network and redundancy analyses suggested that intI1, Firmicutes, and pH were mainly responsible for the changes in ARGs, thus controlling these factors might help to inhibit the spread of ARGs.201931442833
7192130.9996Sulfamethoxazole and COD increase abundance of sulfonamide resistance genes and change bacterial community structures within sequencing batch reactors. The abundant microbial community in biological treatment processes in wastewater treatment plants (WWTPs) may potentially enhance the horizontal gene transfer of antibiotic resistance genes with the presence of antibiotics. A lab-scale sequencing batch reactor was designed to investigate response of sulfonamide resistance genes (sulI, sulII) and bacterial communities to various concentrations of sulfamethoxazole (SMX) and chemical oxygen demand (COD) of wastewater. The SMX concentrations (0.001 mg/L, 0.1 mg/L and 10 mg/L) decreased with treatment time and higher SMX level was more difficult to remove. The presence of SMX also significantly reduced the removal efficiency of ammonia nitrogen, affecting the normal function of WWTPs. All three concentrations of SMX raised both sulI and sulII genes with higher concentrations exhibiting greater increases. The abundance of sul genes was positive correlated with treatment time and followed the second-order reaction kinetic model. Interestingly, these two genes have rather similar activity. SulI and sulII gene abundance also performed similar response to COD. Simpson index and Shannon-Weiner index did not show changes in the microbial community diversity. However, the 16S rRNA gene cloning and sequencing results showed the bacterial community structures varied during different stages. The results demonstrated that influent antibiotics into WWTPs may facilitate selection of ARGs and affect the wastewater conventional treatment as well as the bacteria community structures.201728211331
7191140.9996The impact of antimicrobials on the efficiency of methane fermentation of sewage sludge, changes in microbial biodiversity and the spread of antibiotic resistance. The study was designed to simultaneously evaluate the influence of high doses (512-1024 µg/g) the most commonly prescribed antimicrobials on the efficiency of anaerobic digestion of sewage sludge, qualitative and quantitative changes in microbial consortia responsible for the fermentation process, the presence of methanogenic microorganisms, and the fate of antibiotic resistance genes (ARGs). The efficiency of antibiotic degradation during anaerobic treatment was also determined. Metronidazole, amoxicillin and ciprofloxacin exerted the greatest effect on methane fermentation by decreasing its efficiency. Metronidazole, amoxicillin, cefuroxime and sulfamethoxazole were degraded in 100%, whereas ciprofloxacin and nalidixic acid were least susceptible to degradation. The most extensive changes in the structure of digestate microbiota were observed in sewage sludge exposed to metronidazole, where a decrease in the percentage of bacteria of the phylum Bacteroidetes led to an increase in the proportions of bacteria of the phyla Firmicutes and Proteobacteria. The results of the analysis examining changes in the concentration of the functional methanogen gene (mcrA) did not reflect the actual efficiency of methane fermentation. In sewage sludge exposed to antimicrobials, a significant increase was noted in the concentrations of β-lactam, tetracycline and fluoroquinolone ARGs and integrase genes, but selective pressure was not specific to the corresponding ARGs.202133831706
7961150.9996Effect of tetracycline on ammonia and carbon removal by the facultative bacteria in the anaerobic digester of a sewage treatment plant. This study was conducted to see the effect of tetracycline on nitrogen assimilation and carbon removal in an anaerobic digester of a sewage plant. Samples of sewage were collected from an anaerobic digester sludge. Consortium of nitrogen assimilating bacteria were isolated from the sample and its ability to assimilate ammonia at different concentrations of tetracycline was measured along with carbon removal. The results indicate that while high concentrations of tetracycline of more than 100 mg/L delayed the growth of the bacteria, the resistant bacteria grew after a lag period and the removal of nitrogen and carbon was unaffected even at the highest tetracycline concentration of 250 mg/L tested in this study.201830025323
8036160.9996Abundances of Tetracycline Resistance Genes and Tetracycline Antibiotics during Anaerobic Digestion of Swine Waste. The impact of anaerobic digestion of animal waste on the persistence of antibiotic resistance genes (ARGs) and antibiotics is not widely studied. Two identical, 800-L digesters seeded with swine slurry were followed up to 100 d in three separate trials. The trials received varying amounts of antibiotic-free corn ( L.) mixed with water to maintain the digestion process. Biogas production, seven tetracycline resistance () genes, and three tetracyclines and their transformation products were measured. Biogas production proportionally increased as the feeding loads increased between trials. In Trial 1, log gene copies showed small but statistically significant ( < 0.01) increases during digestion. In Trial 2, anaerobic digestion did not have a significant ( > 0.05) effect except for significant reductions in B ( < 0.0001) and G ( = 0.0335) log gene copies. In Trial 3, which received the highest amount of corn mix, log copies of the 16S ribosomal RNA and the genes significantly ( < 0.0001) reduced over time during digestion. Up to 36 μg L tetracycline, 112 μg L chlortetracycline, 11.9 mg L isochlortetracycline, and 30 μg L 4-epitetracycline were detected both in the liquid and solid digestates. Results of this study revealed that although anaerobic digestion of swine waste can produce useful biogas, it does not result in complete removal of bacteria, ARGs, and antibiotics regardless of differences in the feeding loads between trials. Further effluent and sludge treatments are required prior to their downstream use in crop production to minimize emergence and environmental dissemination of antimicrobial-resistant bacteria through animal manure.201930640349
7964170.9996Fate of sulfonamide resistance genes during sludge anaerobic fermentation: Roles of sludge components and fermentation pHs. This study assessed potential effects of two neglected factors (sludge components and pH values) on the fate of sulfonamide (sul) resistance genes during sludge anaerobic fermentation. It was found that sludge with different contents of protein, carbohydrate and humic acid caused no significant changes in the abundances of sul genes. Nevertheless, sul genes were sensitive to pHs (4-10), and the maximum attenuations (0.8-1.1 log unit) were obtained at pH 10. Mechanism exploration indicated that pHs drove the community evolution of sulfonamide resistant bacteria (SRB), most of which were affiliated to the pH-enriched phyla but not the pH-enriched dominant genera. In addition, the relative abundances of SRB were decreased under both acidic and alkaline conditions. Furthermore, the abundances of intI 1 as well as the sul-carrying abilities of plasmid and extracellular DNA were all reduced at test pHs, indicating that the potential of horizontal gene transfer among bacteria was restricted.201931226672
8035180.9996Effects of hydrothermal treatment on the reduction of antibiotic-resistant Escherichia coli and antibiotic resistance genes and the fertilizer potential of liquid product from cattle manure. In this study, the reduction in the abundance of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) and the fertilizer potential of liquid products from hydrothermally treated cattle manure were investigated. Hydrothermal treatment (HTT) was conducted under different reaction temperatures (125, 150, 175 and 200 °C) and retention times (60, 90 and 120 min). The total organic carbon (TOC) and total nitrogen (TN) of the liquid product increased with increasing reaction temperature. The germination index (GI), a measure of the percentage of germination, exceeded 90 % at 125, 150, and 175 °C in diluted samples, while it decreased to 18 % at 200 °C. Although a longer retention time contributed to an increase in TOC of liquid products, it did not increase the GI values. The liquid product should be diluted or adjusted before use as fertilizer to prevent phytotoxicity. In our analysis of ARB and ARGs, E. coli and antibiotic-resistant E. coli were completely reduced after HTT, except for the operating conditions of 125 °C and 60 min. Although both a higher reaction temperature and longer retention time tended to be better for the reduction of ARGs and intI1, it was found that the longer retention time is much more effective than the higher reaction temperature. The reduction of target ARGs and intI1 was 2.9-log under175 °C and 120 min. Comprehensively considering the fertilizer potential of liquid product and the reduction of ARB and ARGs, 175 °C of reaction temperature and 120 min of retention time of operating conditions for HTT were recommended.202438744164
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