Pyroligneous acid mitigated dissemination of antibiotic resistance genes in soil

Application of compost amended with biochar on the distribution of antibiotic resistance genes in a soil-cucumber system-from the perspective of high-dose fertilization

The transfer of antibiotic resistance genes (ARGs) from soils to vegetables negatively impacts human health. This study explored the effects of the high-dose (18.73 t/ha) application of traditional compost (TC) and composts produced through the co-composting of traditional materials with large-sized (5-10 mm) biochar-amended compost (LBTC) or small-sized (< 0.074 mm) biochar-amended compost (SBTC) on the distribution of ARGs in a soil-cucumber system were explored. Results indicated that the SBTC group had the highest soil nitrogen, phosphorus, and potassium contents, followed by the LBTC, TC, and control treatment groups. These findings aligned with the quality and weight of harvested cucumbers. Bacterial community diversity decreased in compost-fertilized soils. Compared with their preexperimental values in soils, the total absolute abundances of ARGs and mobile genetic elements (MGEs) increased by 23.88 and 6.66 times, respectively, in the control treatment group; by 5.59 and 5.23 times, respectively, in the TC group; by 5.50 and 1.81 times, respectively, in the LBTC group; and by 5.49 and 0.47 times, respectively, in the SBTC group. Compared with those in the control treatment group, the absolute abundance of ermB, ermT, gyrA, qnrS, tetC, and intI1 decreased by 6-100% in the soil of the SBTC group. Compost application to soils significantly decreased ARG abundance in cucumbers; SBTC had the most significant effect and reduced the number of host bacteria at the phylum level from four to three. Nutrient levels in soils were important factors influencing the migration of ARGs from soils to cucumbers. In summary, when compared to other composts, the high-dose (18.73 t/ha) application of SBTC is more effective at reducing the risk of the accumulation and transfer of ARGs in the soil-cucumber system.

Microplastics enhance the prevalence of antibiotic resistance genes in mariculture sediments by enriching host bacteria and promoting horizontal gene transfer

Microplastics (MPs) and antibiotic resistance genes (ARGs) pose significant challenges to the One Health framework due to their intricate and multifaceted ecological and environmental impacts. However, the understanding of how MP properties influence ARG prevalence in mariculture sediments remains limited. Herein, the polystyrene (PS) and polyvinyl chloride (PVC) MPs with different sizes (20-120 μm and 0.5-2.0 mm) were selected to evaluate their impacts and underlying mechanisms driving ARGs dissemination. The results showed that PS and PVC MPs increased the relative abundance of ARGs by 1.41-2.50-fold and 2.01-2.84-fold, respectively, compared with control, particularly high-risk genes. The polymer type effect was identified as more influential than the size effect in driving the sediment resistome evolution. PVC shifted the microbial community assembly from stochastic to deterministic processes, thus enriching ARG host pathogens. Furthermore, the highly hydrophobic PS not only recruited the host bacteria colonization but also facilitated ARG exchange within the plastisphere. The exogenous additives released by PVC (e.g., heavy metals, bisphenol A, and tridecyl ester) and the particles synergistically promoted ARG conjugative transfer by inducing oxidative stress and enhancing cell membrane permeability. These findings revealed how MPs characteristics facilitated the spread of ARGs in marine benthic ecosystems, underscoring the importance of mitigating MPs pollution to maintain mariculture ecosystem health, prevent zoonotic diseases, and balance global mariculture with ecological health.

Antibiotic resistance in urban soils: Dynamics and mitigation strategies

Antibiotic resistance (AR) is a critical global health issue with significant clinical and economic implications. AR occurs when microorganisms develop mechanisms to withstand the effects of antibiotics, reducing treatment efficacy and increasing the risk of mortality and healthcare costs. While the connection between antibiotic use in clinical and agricultural settings and the emergence of AR is well-established, the role of urban soils as reservoirs and spreaders of AR is underexplored. This review examines the complex dynamics of AR in urban soils, highlighting the various sources of antibiotics, including domestic wastewater, industrial effluents, urban agricultural practices, but also microplastics and domestic animal excrements. The selective pressure exerted by these anthropogenic sources promotes the proliferation of antibiotic-resistant bacteria, particularly through horizontal gene transfer, which facilitates the transmission of resistance genes among soil microorganisms in urban environments. About that, the presence of antibiotics in urban soils poses a significant threat to public health by potentially transferring resistance genes to human pathogens through multiple pathways, including direct contact, food consumption, and water ingestion. Furthermore, AR in urban soils disrupts microbial community dynamics, impacting soil fertility, plant growth, and overall environmental quality. Therefore, this review aims to address gaps in understanding AR in urban soils, offering insights into its implications for human health and ecosystem integrity. By identifying these gaps and suggesting evidence-based strategies, this review proposes valid and sustainable solutions to mitigate and counteract the spread of AR in urban environments.

Reduction of tobacco alkaloid bioaccumulation in pea shoots: A comparative study of biochar derived from cow dung and maize straw

Tobacco alkaloids in tobacco-cultivated soils pose potential risks for succeeding crops, due to their allelopathy and toxicity. Effects of biochar on the dissipation of tobacco alkaloids in soil-crop systems remain poorly understood. In this study, a 40-day pot experiment was conducted to explore the effect of cow dung biochar (CDBC) and maize straw biochar (MSBC) on the uptake of nicotine and nornicotine by pea (Pisum sativum L.) and their dissipation in an agricultural soil. The results revealed that the bioaccumulation of nicotine and nornicotine by pea shoots in the soils added with CDBC and MSBC at 1.5% and 3.0% significantly decreased by 46.97-79.13% and 33.64-71.59%, respectively. CDBC more effectively decreased the uptake and bioaccumulation of nicotine and nornicotine by pea shoots than MSBC due to the higher soil pH and nutrient content. In addition, the enhanced relative abundances of soil nicotine-degrading bacteria belonging to the genera Arthrobacter and Gemmatimonas also contributed to the decreasing uptake of nicotine by pea plants. The decreased bioavailability in the soils due to the increased adsorption was the key factor for the reduced bioaccumulation of tobacco alkaloids. This study provides guidance to protect subsequent crops in tobacco-cultivated soil from tobacco alkaloids with biochar.

Saline-alkali soil amended with biochar derived from maricultural-solid-waste: Ameliorative effect and mechanism

At present, it is estimated that approximately 800 million hectares of arable land worldwide is saline-alkali soil, which has become one of the major limiting factors restricting global agricultural productivity. Meanwhile, the residual food and excreta of mariculture animals, accompanied by potential eutrophication pollution, remain an unresolved issue due to salinity. In this study, the ameliorative effects of biochar (BC700) prepared from maricultural-solid-waste on the biological properties and physicochemical of saline-alkali soil and Salicornia europaea L growth were investigated. Supplements of 1, 3 and 5% BC700 significantly increased the total nitrogen, available phosphorus, available potassium and organic carbon in soil by 2.00-68.30%, 26.74-64.96%, 7.74-52.53% and 3.43-64.96%, respectively. And BC700 significantly reduced soil pH. This occurred with enhanced soil urease, sucrase and alkaline phosphatase activities and alterations to the bacterial community structure, thus improving P and N cycling and the soil physicochemical properties. In addition, BC700 has weakened the competition between saline soil microorganisms and also changed the key species of microbial networks. Co-utilization of BC700 and S. europaea cultivation could increase the stability of the soil microbial community while the growth of the plant was significantly promoted by 19.8-25.4%. Supplements of 3% BC700 are recommended as an eco-friendly and effective treatment for the recycling of mariculture wastes for the improvement of saline-alkali soils.

Effect of Combined Application of Wood Vinegar Solution and Biochar on Saline Soil Properties and Cotton Stress Tolerance

Biomass pyrolysis by-products, such as biochar (BC) and wood vinegar (WV), are widely used as soil conditioners and efficiency enhancers in agriculture. A pot experiment was conducted to examine the effects of WV, both alone and in combination with BC, on soil properties in mildly saline soil and on cotton stress tolerance. The results demonstrated that BC and WV application, either individually or together, increased soil nutrient content. The combined application was more effective than the individual applications, resulting in a 5.18-20.12% increase in organic matter, a 2.65-15.04% increase in hydrolysable nitrogen, a 2.23-58.05% increase in effective phosphorus, and a 2.71-29.38% increase in quick-acting potassium. Additionally, the combined application of WV and BC led to greater improvements in cotton plant height, net photosynthetic rate (Pn), leaf nitrate reductase (NR), superoxide dismutase (SOD), and catalase (CAT) activities compared to the application of BC or WV alone. The enhancements in this study varied across different parameters. Plant height showed an increase of 14.32-21.90%. Net photosynthetic rate improved by 13.56-17.60%. Leaf nitrate reductase increased by 5.47-37.79%. Superoxide dismutase and catalase showed improvements of 5.82-64.95% and 10.36-71.40%, respectively (p < 0.05). Moreover, the combined treatment outperformed the individual applications of WV and BC, resulting in a significant decrease in MDA levels by 2.47-51.72% over the experimental period. This combined treatment ultimately enhanced cotton stress tolerance. Using the entropy weight method to analyze the results, it was concluded that the combined application of WV and BC could enhance soil properties in mildly saline soils, increase cotton resistance, and hold significant potential for widespread application.

Effects of nitrogen fertilization on the fate of high-risk antibiotic resistance genes in reclaimed water-irrigated soil and plants

High-risk antibiotic resistance genes (ARGs) in reclaimed water-irrigated soil pose a potential threat to ecosystem and human health. Inorganic fertilization - including with nitrogen, a key ingredient in agricultural production - may affect the ARG profile in soil. However, little is known about nitrogen fertilization's influence on ARGs profiles in the soil-plant system. This study investigated the effects of different nitrogen fertilizer types (CO(NH2)2, NO3--N (NaNO3) and NH4+-N (NH4HCO3)) and different nitrogen fertilizer application rates (low, medium, high) on the distribution of high-risk ARGs in reclaimed water-irrigated soil and plants using quantitative PCR, high-throughput sequencing and metagenomic sequencing. Soil microcosms results revealed that nitrogen fertilization significantly affected the pattern of high-risk ARGs in soil, and also affected high-risk ARGs abundance and transfer capacity in plants. Compared with nitrogen fertilizer application rate, nitrogen fertilizer types significantly contributed to enhancing the soil resistome, with the order of CO(NH2)2 > NO3--N ≈ NH4+-N. The medium application of NO3--N and NH4+-N significantly reduced high-risk ARGs abundance in the leaf endophyte. Bacterial community mainly drove the variation of ARGs in nitrogen-fertilized soil-plant system, and class I integron and metal resistance genes (MRGs) also had direct effects on these high-risk ARGs. A similar high-risk ARGs pattern was also found in field plot experiments, and several dangerous pathogens were observed as the main high-risk ARGs potential hosts in nitrogen-fertilized soil. Based on an economic assessment, application of NH4+-N (NH4HCO3) could reduce costs by $1,312.83 ha-1 compared with NO3--N (NaNO3). These results showed that the more important role of nitrogen type might be an effective and economical way to control high-risk ARGs spread in soil-plant system under reclaimed water irrigation.

The Potential of Wood Vinegar to Replace Antimicrobials Used in Animal Husbandry-A Review

The indiscriminate use of antimicrobials in animal husbandry can result in various types of environmental contamination. Part of the dose of these products is excreted, still active, in the animals' feces and urine. These excreta are widely used as organic fertilizers, which results in contamination with antimicrobial molecules. The impacts can occur in several compartments, such as soil, groundwater, and surface watercourses. Also, contamination by antimicrobials fed or administrated to pigs, chickens, and cattle can reach the meat, milk, and other animal products, which calls into question the sustainability of using these products as part of eco-friendly practices. Therefore, a search for alternative natural products is required to replace the conventional antimicrobials currently used in animal husbandry, aiming to mitigate environmental contamination. We thus carried out a review addressing this issue, highlighting wood vinegar (WV), also known as pyroligneous acid, as an alternative antimicrobial with good potential to replace conventional products. In this regard, many studies have demonstrated that WV is a promising product. WV is a nontoxic additive widely employed in the food industry to impart a smoked flavor to foods. Studies have shown that, depending on the WV concentration, good results can be achieved using it as an antimicrobial against pathogenic bacteria and fungi and a valuable growth promoter for poultry and pigs.

The distribution profiles of tetracycline resistance genes in rice: Comparisons using four genotypes

The potential transmission of antibiotic resistance genes (ARGs) from the rhizosphere to plants and humans poses a significant concern. This study aims to investigate the distribution of tetracycline resistance genes (TRGs) in rice using four genotypes and identify the primary source of TRGs in grains. Quantitative polymerase chain reaction (qPCR) was employed to determine the abundance of seven TRGs and intI1 in four rice varieties and three partitions during the jointing and heading stages, respectively. The analysis of the bacterial community was conducted to elucidate the underlying mechanism of the profiles of TRGs. It was observed that tetZ was predominantly present in the rhizosphere and endoroot, whereas tetX became dominant in grains. The relative abundances of TRGs and intI1 exhibited significant variations across both the variety and partition. However, no significant differences were observed in grains, where the abundances of TRGs were several orders of magnitude lower compared to those in the rhizosphere. Nevertheless, the potential risk of the dissemination of TRGs to humans, particularly those carried by potential pathogens in grains, warrants attention. The increased likelihood of TRGs accumulation in the rhizosphere and endoroot of hybrid rice varieties, as opposed to japonica varieties, may be attributed to the heightened metabolic activities of their roots. The significant associations observed between intI1 and TRGs, coupled with the substantial alterations in potential hosts for intI1 across various treatments, indicate that intI1-mediated horizontal gene transfer plays a role in the diverse range of bacterial hosts for TRGs. The study also revealed that rhizosphere bacteria during the jointing stage serve as the primary contributors of TRGs in grains through the endoroot junction. The findings indicate that Japonica rice varieties exhibit superior control over TRGs compared to hybrid varieties, emphasizing the need for early interventions throughout the entire growth period of rice.

Elucidating the role of two types of essential oils in regulating antibiotic resistance in soil

Although several approaches for reducing antibiotic resistance genes (ARGs) in soil have been proposed, the application of environmentally friendly approaches is now attracting much more attention. In the present study, two types of essential oils (EOs), namely lavender essential oil (LEO) and oregano essential oil (OEO), were selected to investigate their roles in regulating ARGs in soil. In a 28-day microcosm experiment, it was found that the different types and doses of EOs significantly changed the composition of microbial communities. The LEO treatments enriched more taxa belonging to Actinobacteria than the control, whereas the low dose of OEO reduced Actinobacteria enrichment. Besides, the control and the treatments with a high dose of LEO and OEO all significantly enriched the functional pathways related to Human Diseases, which were positively associated with ARGs. However, the low dose of these EOs helped to reduce the pathways. Because of inhibition of the functional pathways and ARG hosts, the low dose of OEO reduce the ARGs related to antibiotic efflux by 71.8% and the resistance genes to multidrug by 56.4%, but these roles did not occur in LEO treatments. These outcomes provide practical and theoretical support for the application of EOs in remediating ARG-contaminated soils.

Understanding the multifunctionality of pyroligneous acid from waste biomass and the potential applications in agriculture

Efforts have been directed to the development of environmentally friendly processes and manufacturing of green products, use of renewable energy and more sustainable agricultural practices. Pyroligneous acid (PA) is a byproduct of biomass pyrolysis that consists of a complex mixture of bioactive substances. The complexity and richness of PA composition have opened a window for PA application in agriculture and mitigation of environmental pollution. This review brings a brief historical on the use of PA and regulatory policies adopted in Brazil, China, Japan and Thailand for PA application in agriculture. The composition and stability of PAs of several origins are presented, together with a discussion of the use of PA to boost plant growth and crop productivity, remove toxic metals from soil, inhibit soil ureases, mitigate the emission of greenhouse gases, control phytopathogen proliferation and weed dissemination. A great variety of biomass types are reported as feedstock to produce PA with distinct chemically diverse and active substances at wide-ranging concentrations. PA has been shown to successfully improve farming practices in a more sustainable fashion. The disclosure of the mechanisms of action that drive the PA's effects, together with the pursue of safety and efficacy data in a case-by-case way to address toxicity and shelf stability, will be valuable to expand the use of PA worldwide for food production.

Wheat straw pyrochar more efficiently decreased enantioselective uptake of dinotefuran by lettuce and dissemination of antibiotic resistance genes than hydrochar in an agricultural soil

Remediation of soils pollution caused by dinotefuran, a chiral pesticide, is indispensable for ensuring human food security. In comparison with pyrochar, the effect of hydrochar on enantioselective fate of dinotefuran, and antibiotic resistance genes (ARGs) profiles in the contaminated soils remain poorly understood. Therefore, wheat straw hydrochar (SHC) and pyrochar (SPC) were prepared at 220 and 500 °C, respectively, to investigate their effects and underlying mechanisms on enantioselective fate of dinotefuran enantiomers and metabolites, and soil ARG abundance in soil-plant ecosystems using a 30-day pot experiment planted with lettuce. SPC showed a greater reduction effect on the accumulation of R- and S-dinotefuran and metabolites in lettuce shoots than SHC. This was mainly resulted from the lowered soil bioavailability of R- and S-dinotefuran due to adsorption/immobilization by chars, together with the char-enhanced pesticide-degrading bacteria resulted from increased soil pH and organic matter content. Both SPC and SHC efficiently reduced ARG levels in soils, owing to lowered abundance of ARG-carrying bacteria and declined horizontal gene transfer induced by decreased dinotefuran bioavailability. The above results provide new insights for optimizing char-based sustainable technologies to mitigate pollution of dinotefuran and spread of ARGs in agroecosystems.

Augmented dissemination of antibiotic resistance elicited by non-antibiotic factors

The emergence and rapid spread of antibiotic resistance seriously compromise the clinical efficacy of current antibiotic therapies, representing a serious public health threat worldwide. Generally, drug-susceptible bacteria can acquire antibiotic resistance through genetic mutation or gene transfer, among which horizontal gene transfer (HGT) plays a dominant role. It is widely acknowledged that the sub-inhibitory concentrations of antibiotics are the key drivers in promoting the transmission of antibiotic resistance. However, accumulating evidence in recent years has shown that in addition to antibiotics, non-antibiotics can also accelerate the horizontal transfer of antibiotic resistance genes (ARGs). Nevertheless, the roles and potential mechanisms of non-antibiotic factors in the transmission of ARGs remain largely underestimated. In this review, we depict the four pathways of HGT and their differences, including conjugation, transformation, transduction and vesiduction. We summarize non-antibiotic factors accounting for the enhanced horizontal transfer of ARGs and their underlying molecular mechanisms. Finally, we discuss the limitations and implications of current studies.

Effect of composted pig manure, biochar, and their combination on antibiotic resistome dissipation in swine wastewater-treated soil

The prevalence of antibiotic resistance genes (ARGs), owing to irrigation using untreated swine wastewater, in vegetable-cultivated soils around swine farms poses severe threats to human health. Furthermore, at the field scale, the remediation of such soils is still challenging. Therefore, here, we performed field-scale experiments involving the cultivation of Brassica pekinensis in a swine wastewater-treated soil amended with composted pig manure, biochar, or their combination. Specifically, the ARG and mobile genetic element (MGE) profiles of bulk soil (BS), rhizosphere soil (RS), and root endophyte (RE) samples were examined using high-throughput quantitative polymerase chain reaction. In total, 117 ARGs and 22 MGEs were detected. Moreover, we observed that soil amendment using composted pig manure, biochar, or their combination decreased the absolute abundance of ARGs in BS and RE after 90 days of treatment. However, the decrease in the abundance of ARGs in RS was not significant. We also observed that the manure and biochar co-application showed a minimal synergistic effect. To clarify this observation, we performed network and Spearman correlation analyses and used structure equation models to explore the correlations among ARGs, MGEs, bacterial composition, and soil properties. The results revealed that the soil amendments reduced the abundances of MGEs and potential ARG-carrying bacteria. Additionally, weakened horizontal gene transfer was responsible for the dissipation of ARGs. Thus, our results indicate that composted manure application, with or without biochar, is a useful strategy for soil nutrient supplementation and alleviating farmland ARG pollution, providing a justification for using an alternative to the common agricultural practice of treating the soil using only untreated swine wastewater. Additionally, our results are important in the context of soil health for sustainable agriculture.

Conjugation-mediated transfer of antibiotic resistance genes influenced by primary soil components and underlying mechanisms

Soil is the main natural reservoir of antibiotic resistant bacteria and antibiotic resistance genes (ARGs). Their dissemination and proliferation were largely motivated by conjugative transfer, while the influence of soil components on bacterial conjugative transfer and the underlying mechanisms remain poorly understood. In the present study, two Escherichia coli strains were exposed to soil minerals (quartz, kaolinite and montmorillonite) and organic matters (humic acid, biochar and soot) respectively to investigate their impact on ARGs conjugation. The results showed that quartz had no significant effect on conjugation; montmorillonite promoted the growth of the donor, but inhibited the recipient and conjugant; kaolinite and three organic matters significantly promoted the production of conjugant, while biochar promoted and then inhibited it with time prolong. Within the range of bacterial concentration involved in this study, the concentration of conjugant increased with the ratio of the concentration of donor and recipient (R_D/R), indicating that the variation of conjugant production was mainly mediated by changing R_D/R. Further observation of biochar treatment group showed that the bacterial responses such as cell membrane permeability, cell surface hydrophobicity and biofilm formation ability shifted with the exposure time, which might be a potential factor affecting conjugative transfer. Collectively, our findings suggest that the type and exposure time of soil components jointly affected conjugation, while the change of R_D/R and related bacterial responses are the main underlying mechanisms.

Hormetic Effect of Pyroligneous Acids on Conjugative Transfer of Plasmid-mediated Multi-antibiotic Resistance Genes within Bacterial Genus

Spread of antibiotic resistance genes (ARGs) by conjugation poses great challenges to public health. Application of pyroligneous acids (PA) as soil amendments has been evidenced as a practical strategy to remediate pollution of ARGs in soils. However, little is known about PA effects on horizontal gene transfer (HGT) of ARGs by conjugation. This study investigated the effects of a woody waste-derived PA prepared at 450°C and its three distillation components (F1, F2, and F3) at different temperatures (98, 130, and 220°C) on conjugative transfer of plasmid RP4 within Escherichia coli. PA at relatively high amount (40-100 μL) in a 30-mL mating system inhibited conjugation by 74-85%, following an order of PA > F3 ≈ F2 ≈ F1, proving the hypothesis that PA amendments may mitigate soil ARG pollution by inhibiting HGT. The bacteriostasis caused by antibacterial components of PA, including acids, phenols, and alcohols, as well as its acidity (pH 2.81) contributed to the inhibited conjugation. However, a relatively low amount (10-20 μL) of PA in the same mating system enhanced ARG transfer by 26-47%, following an order of PA > F3 ≈ F2 > F1. The opposite effect at low amount is mainly attributed to the increased intracellular reactive oxygen species production, enhanced cell membrane permeability, increased extracellular polymeric substance contents, and reduced cell surface charge. Our findings highlight the hormesis (low-amount promotion and high-amount inhibition) of PA amendments on ARG conjugation and provide evidence for selecting an appropriate amount of PA amendment to control the dissemination of soil ARGs. Moreover, the promoted conjugation also triggers questions regarding the potential risks of soil amendments (e.g., PA) in the spread of ARGs via HGT.

Soil Component: A Potential Factor Affecting the Occurrence and Spread of Antibiotic Resistance Genes

In recent years, antibiotic resistance genes (ARGs) and antibiotic-resistant bacteria (ARB) in soil have become research hotspots in the fields of public health and environmental ecosystems, but the effects of soil types and soil components on the occurrence and spread of ARGs still lack systematic sorting and in-depth research. Firstly, investigational information about ARB and ARGs contamination of soil was described. Then, existing laboratory studies about the influence of the soil component on ARGs were summarized in the following aspects: the influence of soil types on the occurrence of ARGs during natural or human activities and the control of exogenously added soil components on ARGs from the macro perspectives, the effects of soil components on the HGT of ARGs in a pure bacterial system from the micro perspectives. Following that, the similarities in pathways by which soil components affect HGT were identified, and the potential mechanisms were discussed from the perspectives of intracellular responses, plasmid activity, quorum sensing, etc. In the future, related research on multi-component systems, multi-omics methods, and microbial communities should be carried out in order to further our understanding of the occurrence and spread of ARGs in soil.

Spread and driving factors of antibiotic resistance genes in soil-plant system in long-term manured greenhouse under lead (Pb) stress

Livestock manure is often used as fertilizer in greenhouses, resulting in simultaneous enrichment of heavy metals and antibiotic resistance genes (ARGs) in soils. The soil-plant system is a non-negligible way to spread ARGs; however, the effects of lead (Pb) on the spread of ARGs and their driving factors in the greenhouse soil-plant system remain unclear. In this present study, the occurrence of ARGs in greenhouse soils and their spread into plants under Pb stress were studied. Overall, Pb promoted the accumulation of ARGs in root endophytes at 10, 50, and 100 mg/kg as well as in soils at 10 and 200 mg/kg, but reduced the total relative abundance of ARGs in leaf endophytes. Particularly, Pb increased the mobile genetic elements (MGEs) relative abundance and endophytic bacterial community diversity in roots, consistent with the change in the total relative abundance of ARGs. Network analysis revealed that bacterial community and MGEs may jointly affect the migration of ARGs in the soil-plant system of greenhouses. Overall, this study extended our knowledge of how Pb can promote the transmission of ARGs to plant roots from greenhouse soils receiving long-term manure applications, which must be considered when assessing the risk of ARGs to public health.

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

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

Antibiotic resistant genes in the environment-exploring surveillance methods and sustainable remediation strategies of antibiotics and ARGs

Antibiotic Resistant Genes (ARGs) are an emerging environmental health threat due to the potential change in the human microbiome and selection for the emergence of antibiotic resistant bacteria. The rise of antibiotic resistant bacteria has caused a global health burden. The WHO (world health organization) predicts a rise in deaths due to antibiotic resistant infections. Since bacteria can acquire ARGs through horizontal transmission, it is important to assess the dissemination of antibioticresistant genes from anthropogenic sources. There are several sources of antibiotics, antibiotic resistant bacteria and genes in the environment. These include wastewater treatment plants, landfill leachate, agricultural, animal industrial sources and estuaries. The use of antibiotics is a worldwide practice that has resulted in the evolution of resistance to antibiotics. Our review provides a more comprehensive look into multiple sources of ARG's and antibiotics rather than one. Moreover, we focus on effective surveillance methods of ARGs and antibiotics and sustainable abiotic and biotic remediation strategies for removal and reduction of antibiotics and ARGs from both terrestrial and aquatic environments. Further, we consider the impact on public health as this problem cannot be addressed without a global transdisciplinary effort.

Production and Potential Application of Pyroligneous Acids from Rubberwood and Oil Palm Trunk as Wood Preservatives through Vacuum-Pressure Impregnation Treatment

The development of low-environmental-impact technologies for the elimination of biological damage is one of the vital goals of the wood protection industry. The possibility of utilizing pyroligneous acid as a wood preservative can be a great solution to extend the application of the currently fast-growing timber species, which has lower natural durability against biological damage. In this study, the effectiveness of pyroligneous acid as a wood preservative was evaluated by impregnating rubberwood with pyroligneous acid using vacuum-pressure treatment, and the treated woods were exposed to mould fungi, wood-decay fungi and termite attacks under laboratory conditions. Pyroligneous acids produced from rubberwood (RWPA) and oil palm trunk (OPTPA) at different pyrolysis temperatures were evaluated. To fully understand the effectiveness of pyroligneous acids as wood preservatives, different concentrations of pyroligneous acids were impregnated into rubberwood. Concentrations of 50% RWPA and 30% OPTPA were sufficient against mould and decay fungi on rubberwood. Rubberwood impregnated with pyroligneous acid acted as a slow-acting toxic bait to cause a high termite mortality rate due to toxic feeding and does not serve as a good repellent to prevent termites from feeding on the wood. In general, OPTPA has better biological durability compared to RWPA.

Detection and various environmental factors of antibiotic resistance gene horizontal transfer

Bacterial antibiotic resistance in water environments is becoming increasingly severe, and new antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) have also attracted the attention of researchers. The horizontal transfer of ARGs in water environments is considered one of the main sources of bacterial resistance in the natural environment. Horizontal gene transfer (HGT) mainly includes conjugation, natural transformation, and transduction, and conjugation has been investigated most. Several studies have shown that there are a large number of environmental factors that might affect the horizontal transfer of ARGs in water environments, such as nanomaterials, various oxidants, and light; however, there is still a lack of systematic and comprehensive reviews on the detection and the effects of the influence factors of on ARG horizontal transfer. Therefore, this study introduced three HGT modes, analysed the advantages and disadvantages of current methods for monitoring HGT, and then summarized the influence and mechanism of various factors on ARG horizontal transfer, and the possible reasons for the different effects caused by similar factors were mainly critically discussed. Finally, existing research deficiencies and future research directions of ARG horizontal transfer in water environments were discussed.

Effects of Pyroligneous Acid on Diversity and Dynamics of Antibiotic Resistance Genes in Alfalfa Silage

Antibiotic resistance genes (ARGs) are recognized as contaminants due to their potential risk for human and environment. The aim of the present study is to investigate the effects of pyroligneous acid (PA), a waste of biochar production, on fermentation characteristics, diversity, and dynamics of ARGs during ensiling of alfalfa using metagenomic analysis. The results indicated that PA decreased (P < 0.05) dry matter loss, pH value, gas production, coliform bacteria count, protease activity, and nonprotein-N, ammonia-N, and butyric acid contents and increased (P < 0.05) lactic acid content during ensiling. During fermentation, Bacteria, Firmicutes, and Lactobacillus were the most abundant at kingdom, phylum, and genus levels, respectively. Pyroligneous acid reduced the relative abundance of Bacteria and Firmicutes and increased that of Lactobacillus. The detected ARGs belonged to 36 drug classes, including mainly macrolides, tetracycline, lincosamides, and phenicol. These types of ARGs decreased during fermentation and were further reduced by PA. These types of ARGs were positively correlated (P < 0.05) with fermentation parameters like pH value and ammonia-N content and with bacterial communities. At the genus level, the top several drug classes, including macrolide, tetracycline, lincosamide, phenicol, oxazolidinone, streptogramin, pleuromutilin, and glycopeptide, were positively correlated with Staphylococcus, Streptococcus, Listeria, Bacillus, Klebsiella, Clostridium, and Enterobacter, the potential hosts of ARGs. Overall, ARGs in alfalfa silage were abundant and were influenced by the fermentation parameters and microbial community composition. Ensiling could be a feasible way to mitigate ARGs in forages. The addition of PA could not only improve fermentation quality but also reduce ARG pollution of alfalfa silage.

IMPORTANCE Antibiotic resistance genes (ARGs) are considered environmental pollutants posing a potential human health risk. Silage is an important and traditional feed, mainly for ruminants. ARGs in silages might influence the diversity and distribution of ARGs in animal intestinal and feces and then the manure and the manured soil. However, the diversity and dynamics of ARGs in silage during fermentation are still unknown. We ensiled alfalfa, one of the most widely used forages, with or without pyroligneous acid (PA), which was proved to have the ability to reduce ARGs in soils. The results showed that ARGs in alfalfa silage were abundant and were influenced by the fermentation parameters and microbial community. The majority of ARGs in alfalfa silage reduced during fermentation. The addition of PA could improve silage quality and reduce ARG pollution in alfalfa silage. This study can provide useful information for understanding and controlling ARG pollution in animal production.

Effect of biochar and hydrochar from cow manure and reed straw on lettuce growth in an acidified soil

Soil acidification has become a major environmental and economic concern worldwide. Char materials (e.g biochar, hydrochar) have attracted considerable attention as soil amendments to restore degraded soil. However, the comparative study of biochar and hydrochar on plant growth in acidified soil is limited. In this study, a microcosmic experiment was used to compare the effect of biochar and hydrochar from cow manure (CBC, CHC) and reed straw (RBC, RHC) on the growth of lettuce in the acidified soil. CBC and RHC significantly increased and decreased the biomass of lettuce by 18.7% and 32.5% in the acidified soil, respectively. The increase of the lettuce growth by CBC primarily attributed to the enhancement of soil properties (SOM and pH) and soil nutrient content (Olsen-P, K, Ca, Mg, Zn, Fe and Mn). Moreover, CBC enhanced the microbial activity and complexity and increased the abundance of beneficial genera like Gemmatimonas, Ramlibacter and Haliangium, which improved soil health and might indirectly benefited the lettuce growth. Our findings highlighted the priority of char materials feedstock and preparation technology for remediating the acidified soil.

Effect of nitrilotriacetic acid and tea saponin on the phytoremediation of Ni by Sudan grass (Sorghum sudanense (Piper) Stapf.) in Ni-pyrene contaminated soil

Phytoremediation is commonly used in the remediation of soils co-contaminated by heavy metals and polycyclic aromatic hydrocarbons (PAHs) because of its economy and effectiveness. Sudan grass (Sorghum sudanense (Piper) Stapf.) has well-developed roots and strong tolerance to heavy metals, so it has been widely concerned. In this study, nitrilotriacetic acid (NTA) and tea saponin (TS) were used as enhancers and combined with Sudan grass for improving the remediation efficiency of Ni-pyrene co-contaminated soil. The results of the pot experiment in soils showed that enhancers promoted the enrichment of Ni in plants. With the function of enhancers, more inorganic and water-soluble Ni were converted into low-toxic phosphate-bonded and residual Ni, so as to reinforce the tolerance of Sudan grass to Ni. In the pot experiment based on vermiculite, it was found that enhancers increased the accumulation of Ni in cell wall by 49.71-102.73%. Enhancers also had the positive effect on the relative abundance of Proteobacteria, Patescibacteria and Bacteroidetes that could tolerate heavy metals at phylum level. Simultaneously, the study found that pyrene reduced the exchangeable Ni in soils. More Ni entered the organelles and transfer to more high-toxic forms in Sudan grass when pynere coexisted. The study manifested that enhancers improved the phytoremediation effect of Ni significantly, yet the co-existence of pyrene weakened the process. Our results provided meaningful references for remediating actual co-contaminated soil of heavy metals and PAHs.

Metagenomics revealed the mobility and hosts of antibiotic resistance genes in typical pesticide wastewater treatment plants

Pesticide showed a crucial selective pressure of antibiotic resistance genes (ARGs) in the environmental dimension, especially in the pesticide wastewater treatment process, where the information on the mobility and hosts of ARGs was very important but limited. This study tried to clarify the mobile antibiotic resistome and ARG hosts in three typical pesticide wastewater treatment plants (PWWTPs) through metagenomics. Results showed that ARGs associated with antibiotic efflux and multi-drug resistance generally dominated in the PWWTPs, and the relative abundance of ARGs was generally higher in the water phase than that in sludge phase. The mobile antibiotic resistome accounted for 43.6% ± 16.2% and 44.8% ± 18.0% of the total relative abundance of ARGs in the water phase and sludge phase, respectively. The tnpA, IS91 and intI1 were the dominant mobile genetic elements (MGEs) closely associated with ARGs. MCR-5 and MCR-9 were first identified in the PWWTPs and located together with the tnpA, tnpA2 and int2. The potential human pathogens belonging to Citrobacter, Pseudomonas, Enterobacter, Acinetobacter, and Kluyvern were the major ARG hosts in the PWWTPs. Statistical analysis indicated that microbial community contributed the most to the occurrence of antibiotic resistome, and the reduction of the major ARG hosts was crucial from the perspective of ARGs control.

Potential threat of antibiotics resistance genes in bioleaching of heavy metals from sediment

Bioleaching is considered a promising technology for remediating heavy metals pollution in sediments. During bioleaching, the pressure from the metals bioleached is more likely to cause the spread of antibiotic resistance genes (ARGs). The changes in abundance of ARGs in two typical heavy metal bioleaching treatments using indigenous bacteria or functional bacteria agent were compared in this study. Results showed that both treatments successfully bioleached heavy metals, with a higher removal ratio of Cu with functional bacteria agent. The absolute abundances of most ARGs decreased by one log unit after bioleaching, particularly tetR (p = 0.02) and tetX (p = 0.04), and intI1 decreased from 10⁶ to 10⁴ copies/g. As for the relative abundance, ARGs in the non-agent treatment increased from 3.90 × 10^-4 to 1.67 × 10^-3 copies/16S rRNA gene copies (p = 0.01), and in the treatment with agent, it reached 6.65 × 10^-2 copies/16S rRNA gene copies, and intI1 relative abundance was maintained at 10^-3 copies/16S rRNA gene copies. The relative abundance of ARGs associated with efflux pump mechanism and ribosomal protection mechanism increased the most. The co-occurrence network indicated that Cu bioleached was the environmental factor determining the distribution of ARGs, Firmicutes might be the potential hosts of ARGs. Compared to bioleaching with indigenous bacteria, the addition of functional bacteria agent engendered a decrease in microbial alpha diversity and an increase in the amount of Cu bioleached, resulting in a higher relative abundance of ARGs. Heavy metal pollution can be effectively removed from sediments using the two bioleaching treatments, however, the risk of ARGs propagation posed by those procedures should be considered, especially the treatment with functional bacteria agents. In the future, an economical and efficient green technology that simultaneously reduces both the absolute abundance and relative abundance of ARGs should be developed.

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

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

Individual and combined applications of biochar and pyroligneous acid mitigate dissemination of antibiotic resistance genes in agricultural soil

Remediation of agricultural soils polluted with antibiotic resistance genes (ARGs) is important for protecting food safety and human health. However, the feasibility of co-application of biochar and pyroligneous acid, two multifunctional soil amendments, for mitigating dissemination of soil ARGs is unknown. Thus, a woody biochar (BC450) and its by-product, pyroligneous acid (PA450) simultaneously produced at 450 °C from blended wood wastes, were used to compare their individual and combined effects on soil ARG abundance using a 65-day pot experiment planted with leafy vegetable Brassica chinensis L. The individual and combined applications of PA450 and BC450 significantly reduced the absolute abundance of ARGs by 65.7-81.4% and 47.5-72.9% in the corresponding rhizosphere and bulk soil. However, the co-application showed little synergistic effect, probably due to the counteractive effect of BC450 on the PA450-mitigated soil ARG proliferation, resulted from the promoted soil bacterial growth and/or adsorption of antimicrobial components of PA450 by BC450. The decreased abundances of mobile genetic element intI1 and Tn916/1545 in the PA450 treatments demonstrated the potential of PA450 for weakening horizontal gene transfer (HGT). Furthermore, weakened HGT by individual PA450, lowered availability of heavy metals by individual BC450, and different bacterial community (e.g., reduced ARGs bacterial host) together with improved soil properties from co-application of PA450 and BC450 all contributed to the reduced ARG level. This study highlighted the feasibility of co-applications of biochar and pyroligneous acid amendment for mitigating soil ARG pollution. These findings provide important information for developing eco-friendly technologies using biochar and pyroligneous acid in remediating ARG-contaminated soils.

Biochar decreased enantioselective uptake of chiral pesticide metalaxyl by lettuce and shifted bacterial community in agricultural soil

A 35-day microcosmic experiment was conducted with lettuce (Lactuca sativa L.) and two metalaxyl (MET) enantiomers (R-MET and S-MET) to understand the roles of biochar in the enantioselective fate of chiral pesticides in soil-plant ecosystems. Wood waste-derived biochar (WBC) amendment effectively decreased the shoot concentrations of R-MET/S-MET and their metabolites R-MET/S-MET acid by 57.7-86.3% and 13.3-32.5%, respectively. The reduced uptake was mainly attributed to the decreased bioavailability of R-MET and S-MET. A lower fraction of R-MET was accumulated by the lettuce in the WBC-amended soils relative to the control, suggesting a decrease in the enantioselective uptake of the chiral pesticide MET in the presence of biochar. Regardless of the WBC amendment, no enantiomerization of MET or MET acid occurred. The application of WBC stimulated soil bacterial diversity, shifted the bacterial community, and enhanced the abundance of pesticide degrading bacteria (e.g., Luteimonas, Methylophilus, and Hydrogenophaga), which were responsible for the enantioselective degradation of MET in the soil. This work expands our understanding of the enantioselective fate of chiral pesticides in the biochar-amended soil ecosystems. These findings can be used to develop biochar-based technologies to remediate soils contaminated with these chiral pesticides to ensure food safety.

Influence of Pyroligneous Acid on Fermentation Parameters, CO2 Production and Bacterial Communities of Rice Straw and Stylo Silage

Carbon dioxide (CO₂) is a primary greenhouse gas and the main cause of global warming. Respiration from plant cells and microorganisms enables CO₂ to be produced during ensiling, a method of moist forage preservation applied worldwide. However, limited information is available regarding CO₂ emissions and mitigation during ensiling. Pyroligneous acid, a by-product of plant biomass pyrolysis, has a strong antibacterial capacity. To investigate CO₂ production and the influence of pyroligneous acid, fresh stylo, and rice straw were ensiled with or without 1% or 2% pyroligneous acid. Dynamics of the fermentation characteristics, CO₂ production, and bacterial communities during ensiling were analyzed. Pyroligneous acid increased the lactic acid content and decreased the weight losses, pH, ammonia-N content, butyric acid content, and coliform bacterial numbers (all P < 0.05). It also increased the relative abundance of Lactobacillus and decreased the relative abundances of harmful bacteria such as Enterobacter and Lachnoclostridium. Adding pyrolytic acids reduced the gas production, especially of CO₂. It also increased the relative abundances of CO₂-producing bacterial genera and of genera with the potential for CO₂ fixation. In conclusion, adding pyroligneous acid improved the fermentation quality of the two silages. During ensiling, CO₂ production was correlated with bacterial community alterations. Using pyroligneous acid altered the bacterial community to reduce CO₂ production during ensiling. Given the large production and demand for silage worldwide, application of pyroligneous acid may be an effective method of mitigating global warming via CO₂ emissions.