Black soldier fly-based bioconversion of biosolids: Microbial community dynamics and fate of antibiotic resistance genes. - Related Documents




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694201.0000Black soldier fly-based bioconversion of biosolids: Microbial community dynamics and fate of antibiotic resistance genes. Biosolids as by-products of wastewater treatment can contain a large spectrum of pathogens and antibiotic resistance genes (ARGs). Insect-based bioconversion using black soldier fly larvae (BSFL) is an emerging technology that has shown to reduce significant amounts of biosolids quickly and produce larvae biomass containing low heavy metal concentrations. However, to the best of our knowledge, this is the first study investigating the transfer of pathogens and ARGs from biosolids into the process' end-products, BSFL and frass. We hypothesized that BSF-based bioconversion can decrease the abundance of pathogenic bacteria and ARGs in biosolids. In this study, we performed BSFL feeding trials with biosolids blended or not blended with wheat bran, and wheat bran alone as a low bioburden diet (control). We conducted 16S rRNA amplicon sequencing to monitor changes of the BSFL-associated microbial community and the fate of biosolids-associated pathogens. A diverse set of ARGs (ermB, intl1, sul1, tetA, tetQ, tetW, and blaCTX-M-32) were quantified by qPCR and were linked to changes in substrate- and BSFL-associated microbiomes. BSF-based bioconversion of biosolids-containing substrates led to a significant reduction of the microbial diversity, the abundance of several pathogenic bacteria and the investigated ARGs (< 99 %). Feeding with a high bioburden biosolid diet resulted in a higher microbial diversity, and the accumulation of pathogenic bacteria and ARGs in the BSFL. Results of this study demonstrated that BSF-based bioconversion can be a suitable waste management technology to (1) reduce significant amounts of biosolids and (2) reduce the presence of pathogens and ARGs. However, the resulting larvae biomass would need to undergo further post-treatment to reduce the pathogenic load to allow them as animal feed.202438679091
694310.9998Insights into the reduction of antibiotic-resistant bacteria and mobile antibiotic resistance genes by black soldier fly larvae in chicken manure. The increasing prevalence of antibiotic-resistant bacteria (ARB) from animal manure has raised concerns about the potential threats to public health. The bioconversion of animal manure with insect larvae, such as the black soldier fly larvae (BSFL, Hermetia illucens [L.]), is a promising technology for quickly attenuating ARB while also recycling waste. In this study, we investigated BSFL conversion systems for chicken manure. Using metagenomic analysis, we tracked ARB and evaluated the resistome dissemination risk by investigating the co-occurrence of antibiotic resistance genes (ARGs), mobile genetic elements (MGEs), and bacterial taxa in a genetic context. Our results indicated that BSFL treatment effectively mitigated the relative abundance of ARB, ARGs, and MGEs by 34.9%, 53.3%, and 37.9%, respectively, within 28 days. Notably, the transferable ARGs decreased by 30.9%, indicating that BSFL treatment could mitigate the likelihood of ARG horizontal transfer and thus reduce the risk of ARB occurrence. In addition, the significantly positive correlation links between antimicrobial concentration and relative abundance of ARB reduced by 44.4%. Moreover, using variance partition analysis (VPA), we identified other bacteria as the most important factor influencing ARB, explaining 20.6% of the ARB patterns. Further analysis suggested that antagonism of other bacteria on ARB increased by 1.4 times, while nutrient competition on both total nitrogen and crude fat increased by 2.8 times. Overall, these findings provide insight into the mechanistic understanding of ARB reduction during BSFL treatment of chicken manure and provide a strategy for rapidly mitigating ARB in animal manure.202337832484
694520.9998Mitigation of antibiotic resistome in swine manure by black soldier fly larval conversion combined with composting. The increasing prevalence of antibiotic resistance genes (ARGs) in animal manure has attracted considerable attention because of their potential contribution to the development of multidrug resistance worldwide. Insect technology may be a promising alternative for the rapid attenuation of ARGs in manure; however, the underlying mechanism remains unclear. This study aimed to evaluate the effects of black soldier fly (BSF, Hermetia illucens [L.]) larvae conversion combined with composting on ARGs dynamics in swine manure and to uncover the mechanisms through metagenomic analysis. Compared to natural composting (i.e. without BSF), BSFL conversion combined with composting reduced the absolute abundance of ARGs by 93.2 % within 28 days. The rapid degradation of antibiotics and nutrient reformulation during BSFL conversion combined with composting indirectly altered manure bacterial communities, resulting in a lower abundance and richness of ARGs. The number of main antibiotic-resistant bacteria (e.g., Prevotella, Ruminococcus) decreased by 74.9 %, while their potential antagonistic bacteria (e.g., Bacillus, Pseudomonas) increased by 128.7 %. The number of antibiotic-resistant pathogenic bacteria (e.g., Selenomonas, Paenalcaligenes) decreased by 88.3 %, and the average number of ARGs carried by each human pathogenic bacterial genus declined by 55.8 %. BSF larvae gut microbiota (e.g., Clostridium butyricum, C. bornimense) could help reduce the risk of multidrug-resistant pathogens. These results provide insight into a novel approach to mitigate multidrug resistance from the animal industry in the environment by using insect technology combined with composting, in particular in light of the global "One Health" requirements.202336966826
695430.9997Temporal effects of repeated application of biogas slurry on soil antibiotic resistance genes and their potential bacterial hosts. Biogas slurry, a liquid end product of animal manure fermentation, is widely used as fertilizer in crop fields. Land application may introduce antibiotics and related resistance genes from livestock production into agricultural soil. Nevertheless, changes in antimicrobial resistance in soil where biogas slurry has been repeatedly applied are not fully understood. In the present study, 13 veterinary antibiotics were analyzed in soils that were repeatedly sprayed with biogas slurry, and simultaneously, temporal changes in antibiotic resistance genes (ARGs) and bacterial community composition were investigated using a real-time quantitative PCR assay and MiSeq sequencing. Long-term repeated application of biogas slurry did not result in excessive accumulation of antibiotic residuals in the soil but increased the abundance of ARGs and facilitated ARG transfer among potential hosts. Although the quantitative PCR assay showed a decreasing trend for the relative abundance of ARGs over time, a relevance network analysis revealed highly complex bacteria-ARG co-occurrence after long-term application, which implied that repeated application might intensify horizontal gene transfer (HGT) of ARGs among different bacterial hosts in soil. The increased relative abundance of the intl1 gene supported the shift in ARG-bacteria co-occurrence. Furthermore, ordination analysis showed that the distributions of antibiotic resistance bacteria (ARB) and ARGs were closely related to application duration than to the influence of antibiotic residuals in the biogas slurry-treated soil environment. Additionally, natural level of ARG abundance in untreated soils indirectly suggested the presence/absence of antibiotics was not a key determinant causing the spread of antimicrobial resistance. This study provides improved insight into the effects of long-term repeated application of biogas slurry on the shift in ARG abundances and bacteria-ARG co-occurrence in soils, highlighting the need to focus on the influence of changed soil environment on the ARG transfer.202031818620
694440.9997Rapidly mitigating antibiotic resistant risks in chicken manure by Hermetia illucens bioconversion with intestinal microflora. Antibiotic resistance genes (ARGs) in animal manure are an environmental concern due to naturally occurring bacteria being exposed to these wastes and developing multidrug resistance. The bioconversion of manure with fly larvae is a promising alternative for recycling these wastes while attenuating ARGs. We investigated the impact of black soldier fly (BSF, Hermetia illucens) larval bioconversion of chicken manure on the persistence of associated ARGs. Compared with traditional composting or sterile larval treatments (by 48.4% or 88.7%), non-sterile BSF larval treatments effectively reduced ARGs and integrin genes by 95.0% during 12 days, due to rapid decreases in concentrations of the genes and associated bacteria as they passed through the larval gut and were affected by intestinal microbes. After larval treatments, bacterial community composition differed significantly, with the percentage of Firmicutes possibly carrying ARGs reduced by 65.5% or more. On average, human pathogenic bacteria populations declined by 70.7%-92.9%, effectively mitigating risks of these bacteria carrying ARGs. Environmental pH, nitrogen content and antibiotic concentrations were closely related to both bacterial community composition and targeted gene attenuation in larval systems. Selective pressures of larval gut environments with intestinal microbes, larval bacteriostasis and reformulation of manure due to larval digestion contributed to ARG attenuation.201830318817
695150.9997The vertical migration of antibiotic-resistant genes and pathogens in soil and vegetables after the application of different fertilizers. The prevalence of bacterial resistance caused by the application of animal manure has become an important environmental issue. Herein, the vertical migration of antibiotic resistance genes (ARGs) and pathogens in soil and vegetables after the application of different fertilizers was explored. The results showed that the application of composted manure considerably enhanced the abundance of most ARGs and pathogens, especially in surface soil and pakchoi roots. Moreover, the soil ARGs increased partially from log 1.93 to log 4.65 after the application of composted manure, and six pathogens were simultaneously detected. It was observed that the increase in soil depth decreased most ARGs and pathogens by log 1.04-2.24 and 53.98 %~85.54 %, respectively. This indicated that ARGs and pathogens still existed in the deep soil (80-100 cm). Moreover, total organic carbon had a significant influence on the pathogen distribution, whereas bacterial communities primarily drove the vertical migration of ARGs rather than environmental factors. Although most of the ARG-host associations observed in the surface soil were disappeared in deep soil as revealed by network analysis, some co-occurrence pattern still occurred in deep soil, suggesting that some ARGs might be carried to deep soil by their host bacteria. These results were novel in describing the vertical migration of ARGs in the environment after the application of different fertilizers, providing ideas for curbing their migration to crops.202234400159
702560.9997Aerobic composting as an effective cow manure management strategy for reducing the dissemination of antibiotic resistance genes: An integrated meta-omics study. Livestock manure is considered as an important source for spreading antibiotic resistance genes (ARGs) into the environment, and therefore poses a direct threat to public health. Whereas the effects of reused manure on soil microbial communities and ARGs have been studied extensively, comprehensive characterizations of microbial communities and ARGs of manure produced by different management methods are not well understood. Here, we analyzed the fate of microbial communities and ARGs of cow manure treated by three conventional management strategies: aerobic composting, mechanical drying and precipitation, applying an integrated-omics approach combining metagenomics and metaproteomics. Integrated-omics demonstrated that composted manure contained the lowest diversity of microbial community and ARGs compared with manure treated by other two strategies. Quantitative PCR methods revealed that the abundances of ARGs were reduced by over 83 % after composting for 14 days, regardless of the season. Besides, the potential ARG hosts Acinetobacter and Pseudomonas dominating mechanical drying process were sharply decreased in abundances after composting. The significant co-occurrence networks among bacteria, ARGs and transposase gene tnpA-01 in composting samples indicated the important role of these bacteria in the dissemination of ARGs. These findings offer insight into potential strategies to control the spread of ARGs during livestock manure reuse.202031884359
702670.9997Organic fertilizer potentiates the transfer of typical antibiotic resistance gene among special bacterial species. The propagation of antibiotic resistance genes (ARGs) in environments has evoked many attentions, however, how to identify their host pathogenic bacteria in situ remains a great challenge. Here we explored the bacterial host distribution and dissemination of a typical ARG, sul1 gene, in agricultural soils through the simultaneous detection of sul1 and its host 16S rRNA gene by emulsion paired isolation and concatenation PCR (epicPCR). Compared to chemical fertilizer, organic fertilizer (chicken manure) led to a higher prevalence of sul1 gene in the soil, and dominant bacterial hosts of sul1 gene were classified into Proteobacteria and Bacteroidetes phyla. Additionally, significant higher diversity of antibiotic resistance bacteria (ARB), higher rate of horizontal gene transfer (HGT), higher rate of mobile genetic elements (MGE) and higher proportion of pathogens were all observed in the treatment of organic fertilizer. This study alerts potential health risks of manure applications in agricultural soils.202235483268
745280.9997Elevation of antibiotic resistance genes at cold temperatures: implications for winter storage of sludge and biosolids. Prior research suggests that cold temperatures may stimulate the proliferation of certain antibiotic resistance genes (ARGs) and gene transfer elements during storage of biosolids. This could have important implications on cold weather storage of biosolids, as often required in northern climates until a time suitable for land application. In this study, levels of an integron-associated gene (intI1) and an ARG (sul1) were monitored in biosolids subject to storage at 4, 10 and 20°C. Both intI1 and sul1 were observed to increase during short-term storage (<2 months), but the concentrations returned to background within 4 months. The increases in concentration were more pronounced at lower temperatures than ambient temperatures. Overall, the results suggest that cold stress may induce horizontal gene transfer of integron-associated ARGs and that biosolids storage conditions should be considered prior to land application. SIGNIFICANCE AND IMPACT OF THE STUDY: Wastewater treatment plants have been identified as the hot spots for the proliferation and dissemination of antibiotic resistance genes (ARGs) and antibiotic resistant bacteria (ARB) to the environment through discharge of treated effluent to water bodies as well as application of biosolids to land. Identifying critical control points within the treatment process may aid in the development of solutions for the reduction of ARGs and ARB and curbing the spread of antibiotic resistance. This study found increases in ARGs during biosolids storage and identifies changes in operational protocols that could help reduce ARG loading to the environment when biosolids are land-applied.201425196177
750890.9997Residual chlorine persistently changes antibiotic resistance gene composition and increases the risk of antibiotic resistance in sewer systems. During the COVID-19 pandemic, excessive amounts of disinfectants and their transformation products entered sewer systems worldwide, which was an extremely rare occurrence before. The stress of residual chlorine and disinfection by-products is not only likely to promote the spread of antibiotic resistance genes (ARGs), but also leads to the enrichment of chlorine-resistant bacteria that may also be resistant to antibiotics. Therefore, the potential impact of such discharge on ARG composition should be studied and the health risks should be assessed. Thus, this study combined high-throughput 16S rRNA gene amplicon sequencing and metagenomic analysis with long-term batch tests that involved two stages of stress and recovery to comprehensively evaluate the impact of residual chlorine on the microbial community and ARG compositions in sewer systems. The tests demonstrated that the disturbance of the microbial community structure by residual chlorine was reversible, but the change in ARG composition was persistent. This study found that vertical propagation and horizontal gene transfer jointly drove ARG composition succession in the biofilm, while the driving force was mainly horizontal gene transfer in the sediment. In this process, the biocide resistance gene (BRG) subtype chtR played an important role in promoting co-selection with ARGs through plasmids and integrative and conjugative elements. Moreover, it was further shown that the addition of sodium hypochlorite increased the risk of ARGs to human health, even after discontinuation of dosing, signifying that the impact was persistent. In general, this study strengthens the co-selection theory of ARGs and BRGs, and calls for improved disinfection strategies and more environmentally friendly disinfectants.202337738943
7457100.9997Metagenomic Insights Into the Changes of Antibiotic Resistance and Pathogenicity Factor Pools Upon Thermophilic Composting of Human Excreta. In times of climate change, practicing a form of sustainable, climate-resilient and productive agriculture is of primordial importance. Compost could be one form of sustainable fertilizer, which is increasing humus, water holding capacity, and nutrient contents of soils. It could thereby strengthen agriculture toward the adverse effects of climate change, especially when additionally combined with biochar. To get access to sufficient amounts of suitable materials for composting, resources, which are currently treated as waste, such as human excreta, could be a promising option. However, the safety of the produced compost regarding human pathogens, pharmaceuticals (like antibiotics) and related resistance genes must be considered. In this context, we have investigated the effect of 140- and 154-days of thermophilic composting on the hygienization of human excreta and saw dust from dry toilets together with straw and green cuttings with and without addition of biochar. Compost samples were taken at the beginning and end of the composting process and metagenomic analysis was conducted to assess the fate of antibiotic resistance genes (ARGs) and pathogenicity factors of the microbial community over composting. Potential ARGs conferring resistance to major classes of antibiotics, such as beta-lactam antibiotics, vancomycin, the MLS(B) group, aminoglycosides, tetracyclines and quinolones were detected in all samples. However, relative abundance of ARGs decreased from the beginning to the end of composting. This trend was also found for genes encoding type III, type IV, and type VI secretion systems, that are involved in pathogenicity, protein effector transport into eukaryotic cells and horizontal gene transfer between bacteria, respectively. The results suggest that the occurrence of potentially pathogenic microorganisms harboring ARGs declines during thermophilic composting. Nevertheless, ARG levels did not decline below the detection limit of quantitative PCR (qPCR). Thresholds for the usage of compost regarding acceptable resistance gene levels are yet to be evaluated and defined.202235432262
6987110.9997Chemical fertilizers promote dissemination of ARGs in maize rhizosphere: An overlooked risk revealed after 37-year traditional agriculture practice. Bacterial communities in soil and rhizosphere maintain a large collection of antibiotic resistance genes (ARGs). However, few of these ARGs and antibiotic resistant bacteria (ARB) are well-characterized under traditional farming practices. Here we compared the ARG profiles of maize rhizosphere and their bulk soils using metagenomic analysis to identify the ARG dissemination and explored the potential impact of chemical fertilization on ARB. Results showed a relatively lower abundance but higher diversity of ARGs under fertilization than straw-return. Moreover, the abundance and diversity of MGEs were significantly promoted by chemical fertilizer inputs in the rhizosphere compared to bulk soil. Machine learning and bipartite networks identified three bacterial genera (Pseudomonas, Bacillus and Streptomyces) as biomarkers for ARG accumulation. Thus we cultured 509 isolates belonging to these three genera from the rhizosphere and tested their antimicrobial susceptibility, and found that multi-resistance was frequently observed among Pseudomonas isolates. Assembly-based tracking explained that ARGs and four class I integrons (LR134330, LS998783, CP065848, LT883143) were co-occurred among contigs from Pseudomonas sp. Chemical fertilizers may shape the resistomes of maize rhizosphere, highlighting that rhizosphere carried multidrug-resistant Pseudomonas isolates, which may pose a risk to animal and human health. This study adds knowledge of long-term chemical fertilization on ARG dissemination in farmland systems and provides information for decision-making in agricultural production and monitoring.202438844214
7506120.9997Risk assessment and dissemination mechanism of antibiotic resistance genes in compost. In recent years, the excessive of antibiotics in livestock and poultry husbandry, stemming from extensive industry experience, has resulted in the accumulation of residual antibiotics and antibiotic resistance genes (ARGs) in livestock manure. Composting, as a crucial approach for the utilization of manure resources, has the potential to reduce the levels of antibiotics and ARGs in manure, although complete elimination is challenging. Previous studies have primarily focused on the diversity and abundance of ARGs in compost or have solely examined the correlation between ARGs and their carriers, potentially leading to a misjudgment of the actual risk associated with ARGs in compost. To address this gap, this study investigated the transfer potential of ARGs in compost and their co-occurrence with opportunistic pathogenic bacteria by extensively analyzing metagenomic sequencing data of compost worldwide. The results demonstrated that the potential risk of ARGs in compost was significantly lower than in manure, suggesting that composting effectively reduces the risk of ARGs. Further analysis showed that the microbes shifted their life history strategy in manure and compost due to antibiotic pressure and formed metabolic interactions dominated by antibiotic-resistant microbes, increasing ARG dissemination frequency. Therefore, husbandry practice without antibiotic addition was recommended to control ARG evolution, dissemination, and abatement both at the source and throughout processing.202337562342
7415130.9997Transfer and accumulation of antibiotic resistance genes and bacterial pathogens in the mice gut due to consumption of organic foods. Over the last few decades, organic food demand has grown largely because of increasing personal health concerns. Organic farming introduces antibiotic resistance genes (ARGs) and antibiotic-resistant bacteria (ARB) into foods. However, potential effects of organic foods on the gut microbiome and ARGs have been overlooked. Using high-throughput quantitative PCR and 16S rRNA high-throughput sequencing technology, we examined 132 ARGs from major classes, eight transposase genes, universal class I integron-integrase gene (intI), clinical class I integron-integrase gene (cintI), and the bacterial community in mouse gut after 8 weeks with an either organic or inorganic lettuce and wheat diet. A total of 8 types of major ARGs and 10 mobile genetic elements (MGEs) were detected in mice gut, including tetracycline, multidrug, sulfonamide, aminoglycoside, beta-lactamase, chloramphenicol, MLSB and vancomycin resistance genes. We found that abundance and diversity of ARGs, mobile gene elements, and potential ARB in the gut increased with time after consumption of organic foods, whereas no significant changes were observed in inorganic treated groups. Moreover, MGEs, including IS613, Tp614 and tnpA_03 were found to play an important role in regulating ARG profiles in the gut microbiome following consumption of organic foods. Importantly, feeding organic food increased the relative abundance of the potentially antibiotic-resistant pathogens, Bacteroides and Streptococcus. Our results confirm that there is an increasing risk of ARGs and ARB in the gut microbiome, which highlights the importance of organic food industries taking into account the potential accumulation and transmission of ARGs as a risk factor.202438215844
6998140.9997Field-based evidence for the enrichment of intrinsic antibiotic resistome stimulated by plant-derived fertilizer in agricultural soil. Animal manures have been demonstrated to enhance antibiotic resistance in agricultural soils. However, little is known about the effects of plant-derived fertilizer on soil antibiotic resistome. Herein, metagenomic sequencing was used to investigate the effects of a plant-derived fertilizer processed from sugarcane and beet on soil antibiotic resistance genes (ARGs) in a soybean field along crop growth stages. ARG profiles in the soils amended by plant-derived fertilizer were compared with those in the soils amended by chicken manure. The abundance and diversity of total ARGs in the soils amended by plant-derived fertilizer were significantly (P < 0.05) elevated at the sprout stage, to a level comparable to that in the manured soils. Whereas, unlike chicken manure mainly introducing manure-borne ARGs to soil, the plant-derived fertilizer was indicated to mainly enrich multidrug resistance genes in soil by nourishing indigenous bacteria. ARGs with abundances in amended soils significantly (P < 0.05) higher than in unamended soils at the sprout stage of soybean were considered as enriched ARGs. Decrease in the abundance of the enriched ARGs was observed in both the amended soils from the sprout to the harvest. Network analysis further identified Proteobacteria and Bacteroidetes as the primary bacterial taxa involved in the temporal variation of the enriched ARGs in the soils amended by plant-derived fertilizer, while in manured soils were Firmicutes and Actinobacteria. As revealed by multivariate statistical analyses, variation of the enriched ARGs in the soils amended by plant-derived fertilizer was majorly attributed to the response of co-occurred bacteria to depleting nutrients, which was different from the failed establishment of manure-borne bacteria in the manured soils. Our study provided field-based evidence that plant-derived fertilizer stimulated the intrinsic antibiotic resistome, and proposed attention to the un-perceived risk since some clinically relevant ARGs originate and evolve from natural resistome.202437778843
7455150.9997Lagoon, Anaerobic Digestion, and Composting of Animal Manure Treatments Impact on Tetracycline Resistance Genes. Increased demand for animal protein is met by increased food animal production resulting in large quantities of manure. Animal producers, therefore, need sustainable agricultural practices to protect environmental health. Large quantities of antimicrobials are used in commercial food animal production. Consequently, antimicrobial-resistant bacteria and the resistance genes emerge and are excreted through feces. Manure management is essential for the safe disposal of animal waste. Lagoons, with or without covers, and anaerobic digesters, with the primary purpose of methane production, and composting, with the primary purpose of producing organic fertilizer, are widely used methods of manure treatment. We reviewed manure management practices and their impact on tetracycline resistance genes. Lagoons are maintained at ambient temperatures; especially uncovered lagoons are the least effective in removing tetracycline resistance genes. However, some modifications can improve the performance of lagoons: sequential use of uncovered lagoons and the use of covered lagoons resulted in a one-log reduction, while post-treatments such as biofiltration following covered lagoon treatment resulted in 3.4 log reduction. Mesophilic digestion of animal manure did not have any significant effect; only a 0.7 log reduction in tet(A) was observed in one study. While thermophilic anaerobic digesters are effective, if properly operated, they are expensive for animal producers. Aerobic thermophilic composting is a promising technology if optimized with its economic benefits. Composting of raw animal manure can result in up to a 2.5 log reduction, and postdigestion composting can reduce tetracycline resistance gene concentration by >80%. In general, manure management was not designed to mitigate antimicrobial resistance; future research is needed to optimize the economic benefits of biogas or organic fertilizer on the one hand and for the mitigation of foodborne pathogens and antimicrobial resistance on the other.202235326854
6950160.9997Ceftiofur in swine manure contributes to reducing pathogens and antibiotic resistance genes during composting. Aerobic composting is a common way for the disposal of feces produced in animal husbandry, and can reduce the release of antibiotic resistance genes (ARGs) from feces into the environment. In this study, we collected samples from two distinct treatments of swine manure compost with and without ceftiofur (CEF), and identified the ARGs, mobile genetic elements (MGEs), and bacterial community by metagenomic sequencing. The impacts of CEF on the bacterial community composition and fate of ARGs and MGEs were investigated. With increasing composting temperature and pH, the concentration of CEF in the manure decreased rapidly, with a degradation half-life of 1.12 d and a 100% removal rate after 10 d of aerobic composting. Metagenomics demonstrated that CEF in the manure might inhibit the growth of Firmicutes and Proteobacteria, thereby reducing some ARGs and MGEs hosted by these two bacteria, which was further confirmed by the variations of ARGs and MGEs. A further redundancy analysis suggested that pH and temperature are key environmental factors affecting ARG removal during composting, and intI1 and bacterial communities also have significant influence on ARG abundance. These results are of great significance for promoting the removal of some ARGs from animal manure by controlling some key environmental factors and the type of antibiotics used in animals.202438685300
7389170.9997Temporal changes of antibiotic-resistance genes and bacterial communities in two contrasting soils treated with cattle manure. The emerging environmental spread of antibiotic-resistance genes (ARGs) and their subsequent acquisition by clinically relevant microorganisms is a major threat to public health. Animal manure has been recognized as an important reservoir of ARGs; however, the dissemination of manure-derived ARGs and the impacts of manure application on the soil resistome remain obscure. Here, we conducted a microcosm study to assess the temporal succession of total bacteria and a broad spectrum of ARGs in two contrasting soils following manure application from cattle that had not been treated with antibiotics. High-capacity quantitative PCR detected 52 unique ARGs across all the samples, with β-lactamase as the most dominant ARG type. Several genes of soil indigenous bacteria conferring resistance to β-lactam, which could not be detected in manure, were found to be highly enriched in manure-treated soils, and the level of enrichment was maintained over the entire course of 140 days. The enriched β-lactam resistance genes had significantly positive relationships with the relative abundance of the integrase intI1 gene, suggesting an increasing mobility potential in manure-treated soils. The changes in ARG patterns were accompanied by a significant effect of cattle manure on the total bacterial community compositions. Our study indicates that even in the absence of selective pressure imposed by agricultural use of antibiotics, manure application could still strongly impact the abundance, diversity and mobility potential of a broad spectrum of soil ARGs. Our findings are important for reliable prediction of ARG behaviors in soil environment and development of appropriate strategies to minimize their dissemination.201626712351
7034180.9997Meta-analysis reveals the processes and conditions of using biochar to control antibiotic resistance genes in soil. Soil is a significant reservoir of antibiotic resistance genes (ARGs) and an important habitat for pathogens associated with many clinical infections and plant disease outbreaks. Although scientists have found that biochar can reduce ARGs in soil, the understanding of how biochar removes soil ARGs and the influencing factors remains limited. Here, a meta-analysis of 65 published studies was conducted to illuminate the mechanisms through which biochar remediates ARG-contaminated soils. In biochar-amended soil, the antibiotic content significantly decreased by 24.1 %, while the abundances of mobile genetic elements and ARG host bacteria declined by 23.5 % and 12.1 %, respectively. The reduced antibiotic content, suppressed mobile genetic elements, and altered bacterial community structure collectively led to a 41.8 % reduction in soil ARG abundance. In addition, wood-derived biochar pyrolyzed at 300-500 °C exhibited a substantial advantage in the remediation of ARGs. Furthermore, biochar application decreased the abundance of ARGs in alkaline and neutral soil more markedly than that in acidic soil. The results of this research confirmed the positive mitigating effect of biochar on ARGs in soil, providing valuable insights for the prevention and control of ARG pollution.202540359860
7020190.9997Microbiome, resistome and mobilome of chlorine-free drinking water treatment systems. Drinking water treatment plants (DWTPs) are designed to remove physical, chemical, and biological contaminants. However, until recently, the role of DWTPs in minimizing the cycling of antibiotic resistance determinants has got limited attention. In particular, the risk of selecting antibiotic-resistant bacteria (ARB) is largely overlooked in chlorine-free DWTPs where biological processes are applied. Here, we combined high-throughput quantitative PCR and metagenomics to analyze the abundance and dynamics of microbial communities, antibiotic resistance genes (ARGs), and mobile genetic elements (MGEs) across the treatment trains of two chlorine-free DWTPs involving dune-based and reservoir-based systems. The microbial diversity of the water increased after all biological unit operations, namely rapid and slow sand filtration (SSF), and granular activated carbon filtration. Both DWTPs reduced the concentration of ARGs and MGEs in the water by circa 2.5 log gene copies mL(-1), despite their relative increase in the disinfection sub-units (SSF in dune-based and UV treatment in reservoir-based DWTPs). The total microbial concentration was also reduced (2.5 log units), and none of the DWTPs enriched for bacteria containing genes linked to antibiotic resistance. Our findings highlight the effectiveness of chlorine-free DWTPs in supplying safe drinking water while reducing the concentration of antibiotic resistance determinants. To the best of our knowledge, this is the first study that monitors the presence and dynamics of antibiotic resistance determinants in chlorine-free DWTPs.202336989799