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876500.9960Pseudomonas chlororaphis IRHB3 assemblies beneficial microbes and activates JA-mediated resistance to promote nutrient utilization and inhibit pathogen attack. INTRODUCTION: The rhizosphere microbiome is critical to plant health and resistance. PGPR are well known as plant-beneficial bacteria and generally regulate nutrient utilization as well as plant responses to environmental stimuli. In our previous work, one typical PGPR strain, Pseudomonas chlororaphis IRHB3, isolated from the soybean rhizosphere, had positive impacts on soil-borne disease suppression and growth promotion in the greenhouse, but its biocontrol mechanism and application in the field are not unclear. METHODS: In the current study, IRHB3 was introduced into field soil, and its effects on the local rhizosphere microbiome, disease resistance, and soybean growth were comprehensively analyzed through high-throughput sequencing and physiological and molecular methods. RESULTS AND DISCUSSION: We found that IRHB3 significantly increased the richness of the bacterial community but not the structure of the soybean rhizosphere. Functional bacteria related to phosphorus solubilization and nitrogen fixation, such as Geobacter, Geomonas, Candidatus Solibacter, Occallatibacter, and Candidatus Koribacter, were recruited in rich abundance by IRHB3 to the soybean rhizosphere as compared to those without IRHB3. In addition, the IRHB3 supplement obviously maintained the homeostasis of the rhizosphere microbiome that was disturbed by F. oxysporum, resulting in a lower disease index of root rot when compared with F. oxysporum. Furthermore, JA-mediated induced resistance was rapidly activated by IRHB3 following PDF1.2 and LOX2 expression, and meanwhile, a set of nodulation genes, GmENOD40b, GmNIN-2b, and GmRIC1, were also considerably induced by IRHB3 to improve nitrogen fixation ability and promote soybean yield, even when plants were infected by F. oxysporum. Thus, IRHB3 tends to synergistically interact with local rhizosphere microbes to promote host growth and induce host resistance in the field.202438380096
876710.9960Poly-γ-glutamic acid enhanced the drought resistance of maize by improving photosynthesis and affecting the rhizosphere microbial community. BACKGROUND: Compared with other abiotic stresses, drought stress causes serious crop yield reductions. Poly-γ-glutamic acid (γ-PGA), as an environmentally friendly biomacromolecule, plays an important role in plant growth and regulation. RESULTS: In this project, the effect of exogenous application of γ-PGA on drought tolerance of maize (Zea mays. L) and its mechanism were studied. Drought dramatically inhibited the growth and development of maize, but the exogenous application of γ-PGA significantly increased the dry weight of maize, the contents of ABA, soluble sugar, proline, and chlorophyll, and the photosynthetic rate under severe drought stress. RNA-seq data showed that γ-PGA may enhance drought resistance in maize by affecting the expression of ABA biosynthesis, signal transduction, and photosynthesis-related genes and other stress-responsive genes, which was also confirmed by RT-PCR and promoter motif analysis. In addition, diversity and structure analysis of the rhizosphere soil bacterial community demonstrated that γ-PGA enriched plant growth promoting bacteria such as Actinobacteria, Chloroflexi, Firmicutes, Alphaproteobacteria and Deltaproteobacteria. Moreover, γ-PGA significantly improved root development, urease activity and the ABA contents of maize rhizospheric soil under drought stress. This study emphasized the possibility of using γ-PGA to improve crop drought resistance and the soil environment under drought conditions and revealed its preliminary mechanism. CONCLUSIONS: Exogenous application of poly-γ-glutamic acid could significantly enhance the drought resistance of maize by improving photosynthesis, and root development and affecting the rhizosphere microbial community.202234979944
691120.9960Linking bacterial life strategies with the distribution pattern of antibiotic resistance genes in soil aggregates after straw addition. Straw addition markedly affects the soil aggregates and microbial community structure. However, its influence on the profile of antibiotic resistance genes (ARGs), which are likely associated with changes in bacterial life strategies, remains unclear. To clarify this issue, a soil microcosm experiment was incubated under aerobic (WS) or anaerobic (AnWS) conditions after straw addition, and metagenomic sequencing was used to characterise ARGs and bacterial communities in soil aggregates. The results showed that straw addition shifted the bacterial life strategies from K- to r-strategists in all aggregates, and the aerobic and anaerobic conditions stimulated the growth of aerobic and anaerobic r-strategist bacteria, respectively. The WS decreased the relative abundances of dominant ARGs such as QnrS5, whereas the AnWS increased their abundance. After straw addition, the macroaggregates consistently exhibited a higher number of significantly altered bacteria and ARGs than the silt+clay fractions. Network analysis revealed that the WS increased the number of aerobic r-strategist bacterial nodes and fostered more interactions between r-and K-strategist bacteria, thus promoting ARGs prevalence, whereas AnWS exhibited an opposite trend. These findings provide a new perspective for understanding the fate of ARGs and their controlling factors in soil ecosystems after straw addition. ENVIRONMENTAL IMPLICATIONS: Straw soil amendment has been recommended to mitigate soil fertility degradation, improve soil structure, and ultimately increase crop yields. However, our findings highlight the importance of the elevated prevalence of ARGs associated with r-strategist bacteria in macroaggregates following the addition of organic matter, particularly fresh substrates. In addition, when assessing the environmental risk posed by ARGs in soil that receives crop straw, it is essential to account for the soil moisture content. This is because the species of r-strategist bacteria that thrive under aerobic and anaerobic conditions play a dominant role in the dissemination and accumulation of ARG.202438643583
876830.9959Selective regulation of endophytic bacteria and gene expression in soybean by water-soluble humic materials. BACKGROUND: As part of the plant microbiome, endophytic bacteria play an essential role in plant growth and resistance to stress. Water-soluble humic materials (WSHM) is widely used in sustainable agriculture as a natural and non-polluting plant growth regulator to promote the growth of plants and beneficial bacteria. However, the mechanisms of WSHM to promote plant growth and the evidence for commensal endophytic bacteria interaction with their host remain largely unknown. Here, 16S rRNA gene sequencing, transcriptomic analysis, and culture-based methods were used to reveal the underlying mechanisms. RESULTS: WSHM reduced the alpha diversity of soybean endophytic bacteria, but increased the bacterial interactions and further selectively enriched the potentially beneficial bacteria. Meanwhile, WSHM regulated the expression of various genes related to the MAPK signaling pathway, plant-pathogen interaction, hormone signal transduction, and synthetic pathways in soybean root. Omics integration analysis showed that Sphingobium was the genus closest to the significantly changed genes in WSHM treatment. The inoculation of endophytic Sphingobium sp. TBBS4 isolated from soybean significantly improved soybean nodulation and growth by increasing della gene expression and reducing ethylene release. CONCLUSION: All the results revealed that WSHM promotes soybean nodulation and growth by selectively regulating soybean gene expression and regulating the endophytic bacterial community, Sphingobium was the key bacterium involved in plant-microbe interaction. These findings refined our understanding of the mechanism of WSHM promoting soybean nodulation and growth and provided novel evidence for plant-endophyte interaction.202438178261
856140.9959Three-dimensional synergistic mechanism ofphysical injury, microbiota dysbiosis, and gene transfer in the gut of Cipangopaludina cathayensisunder microplastics and roxithromycin exposure. Microplastics (MPs) and antibiotics pose a combined threat to aquatic organisms by impairing gut health and promoting the spread of antibiotic resistance genes (ARGs). In this study, Cipangopaludina cathayensis was exposed for 28 days to polystyrene MPs, roxithromycin (ROX), and their combination to assess impacts on intestinal barrier integrity, microbiota composition, and ARG proliferation. MPs alone caused significant mucosal damage, villus atrophy, epithelial shedding, and reduced digestive enzyme activities. ROX exposure altered microbiota structure by increasing Bacteroidetes and reducing Firmicutes. Co-exposure (CM group) exacerbated epithelial injury and enzyme inhibition but partially restored balance through enrichment of SCFA-producing, anti-inflammatory bacteria. ARG levels in the CM group rose by over 1000 %, with notable increases in multidrug resistance genes (e.g., blaOXA10) and integrons (e.g., cIntI-1), mainly linked to Bacteroides and Proteobacteria. Transcriptomic data indicated oxidative stress and epithelial disruption under MPs, and upregulation of efflux and integron genes with ROX. Combined exposure triggered DNA repair and SOS pathways, facilitating horizontal gene transfer. These findings highlight a three-dimensional synergistic mechanism-physical damage, microbial dysbiosis, and gene transfer-that amplifies ARG dissemination and intestinal toxicity, underscoring the need to assess ecological risks of composite pollutants in freshwater systems.These processes form a self-reinforcing loop in which physical epithelial damage promotes microbial dysbiosis, which in turn facilitates ARG proliferation through increased permeability and immune disruption.202541067103
696050.9957Effortless rule: Effects of oversized microplastic management on lettuce growth and the dynamics of antibiotic resistance genes from fertilization to harvest. The complexity of soil microplastic pollution has driven deeper exploration of waste management strategies to evaluate environmental impact. This study introduced oversized microplastics (OMPs, 1-5 mm) during membrane composting to produce organic fertilizers, and conducted a 2 × 2 pot experiment: exogenous OMPs were added when normal fertilizer (no OMPs intervention) was applied, while artificial removal of OMPs was implemented when contaminated fertilizer (with OMPs) was used. The study assessed the effects of these management strategies on lettuce growth, soil environments, and potential biological safety risks related to the spread and expression of high-risk antibiotic resistance genes (ARGs) in humans. Results showed that both exogenous OMPs addition and removal negatively affected plant height and harvest index, with shifts in the rhizosphere microbial community identified as a key factor rather than soil nutrients. Exogenous OMPs altered rhizosphere and endophytic microbial communities, and plant growth-promoting bacteria were transferred to the surface of OMPs from rhizosphere soil. In contrast, bacteria such as Truepera, Pseudomonas, and Streptomyces in compost-derived OMPs supported lettuce growth, and their removal negated these effects. Some endophytic bacteria may promote growth but pose public health risks when transmitted through the food chain. OMPs in composting or planting significantly enhanced the expression of target ARGs in lettuce, particularly bla(TEM). However, simulated digestion results indicated that OMPs reduced the expression of six key ARGs, including bla(TEM), among the ten critical target ARGs identified in this context. Notably, the removal management strategies raised five of them posing potential risks from lettuce consumption. This study highlights that both introducing and removing OMPs may pose ecological and food safety risks, emphasizing the need for optimized organic waste management strategies to mitigate potential health hazards.202540157188
693860.9956Assessment of the Effects of Biodegradable and Nonbiodegradable Microplastics Combined with Pesticides on the Soil Microbiota. Microplastics (MPs) and pesticides pose significant threats to the health of soil ecosystems. This study investigated the individual and combined effects of biodegradable polylactic acid (PLA) and nonbiodegradable polyethylene terephthalate (PET) microplastics alongside glyphosate and imidacloprid pesticides on soil microbial communities and antibiotic resistance genes (ARGs) via microcosm experiments. Compared with the control, PLA significantly increased microbial alpha diversity and enhanced microbial functions related to environmental information processing and metabolism. However, PLA also selectively enriched populations of beneficial and potentially pathogenic bacteria, whereas PET had comparatively weaker effects. Crucially, PLA exposure resulted in substantially higher total abundance and ecological risk levels of soil ARGs than did PET. Coexposure with pesticides further amplified these effects, with PLA demonstrating notable synergistic interactions with both glyphosate and imidacloprid. These findings challenge the conventional assumption that biodegradable MPs such as PLA are environmentally safer than nonbiodegradable MPs, thus highlighting their potential to induce more complex and potentially severe ecological risks under co-contamination scenarios with pesticides.202541175058
793970.9956Metagenomic insights into the distribution, mobility, and hosts of extracellular antibiotic resistance genes in activated sludge under starvation stress. Extracellular antibiotic resistance genes (eARGs) are important emerging environmental pollutants in wastewater treatment plants (WWTPs). Nutritional substrate deficiency (i.e., starvation) frequently occurs in WWTPs owing to annual maintenance, water quality fluctuation, and sludge storage; and it can greatly alter the antibiotic resistance and extracellular DNA content of bacteria. However, the fate and corresponding transmission risk of eARGs in activated sludge under starvation stress remain largely unknown. Herein, we used metagenomic sequencing to explore the effects of starvation scenarios (carbon, nitrogen, and/or phosphorus deficiency) and environmental conditions (alternating anaerobic-aerobic, anaerobic, anoxic, and aerobic) on the distribution, mobility, and hosts of eARGs in activated sludge. The results showed that 30 days of starvation reduced the absolute abundances of eARGs by 40.9%-88.2%, but high-risk dual and multidrug resistance genes persisted. Starvation, particularly the simultaneous lack of carbon, nitrogen, and phosphorus under aerobic conditions, effectively alleviated eARGs by reducing the abundance of extracellular mobile genetic elements (eMGEs). Starvation also altered the profile of bacterial hosts of eARGs and the bacterial community composition, the latter of which had an indirect positive effect on eARGs via changing eMGEs. Our findings shed light on the response patterns and mechanisms of eARGs in activated sludge under starvation conditions and highlight starvation as a potential strategy to mitigate the risk of previously neglected eARGs in WWTPs.202337060877
853880.9955Metagenomic ecotoxicity assessment of trace difenoconazole on freshwater microbial community. Difenoconazole, a typical triazole fungicide, inhibits the activity of cytochrome P450 enzyme in fungi, and is extensively used in protecting fruits, vegetables, and cereal crops. However, reports elucidating the effects of difenoconazole on aquatic microbial communities are limited. Our study showed that difenoconazole promoted microalgae growth at concentrations ranging from 0.1 to 5 μg/L, which was similar with its environmental residual concentrations. Metagenomic analysis revealed that the aquatic microbial structure could self-regulate to cope with difenoconazole-induced stress by accumulating bacteria exhibiting pollutant degrading abilities. In the short-term, several functional pathways related to xenobiotic biodegradation and analysis were upregulated to provide ability for aquatic microbial community to process xenobiotic stress. Moreover, most disturbed ecological functions were recovered due to the redundancy of microbial communities after prolonged exposure. Furthermore, the risks associated with the dissemination of antibiotic resistance genes were enhanced by difenoconazole in the short-term. Overall, our study contributes to a comprehensive understanding of the difenoconazole-induced ecological impacts and the behavior of aquatic microbial communities that are coping with xenobiotic stress.202235090847
795590.9955Fluoroquinolone antibiotics disturb the defense system, gut microbiome, and antibiotic resistance genes of Enchytraeus crypticus. Antibiotic residues from animal manure cause soil pollution and can pose a threat to soil animals. In this study, the toxicological effects of fluoroquinolone antibiotics on Enchytraeus crypticus, including defence response, gut microbiome, and antibiotic resistance genes (ARGs), were studied. The cytochrome P450 enzyme activity and reactive oxygen species levels increased, activating the defense response. The superoxide dismutase and glutathione S-transferase activity, and the expression of immune defense molecules such as coelomic cytolytic factor, lysozyme, bactericidal protein fetidins and lysenin changed. Furthermore, the diversity of the gut microbiome decreased, and the relative abundance of Bacteroidetes decreased significantly at the phylum level but increased in pathogenic and antibiotic-secreting bacteria (Rhodococcus and Streptomyces) at the genus level. However, the soil microbiome was not significantly different from that of the control group. The relative abundance of ARGs in the gut and soil microbiome significantly increased with enrofloxacin concentration, and the fluoroquinolone ARGs were significantly increased in both the soil (20.85-fold, p < 0.001) and gut (11.72-fold, p < 0.001) microbiomes. Subtypes of ARGs showed a positive correlation with Rhodococcus, which might increase the risk of disease transmission and the probability of drug-resistant pathogens. Furthermore, mobile genetic elements significantly promote the spread of ARGs.202234736185
8644100.9955Biotic and abiotic drivers of soil carbon, nitrogen and phosphorus and metal dynamic changes during spontaneous restoration of Pb-Zn mining wastelands. The biotic and abiotic mechanisms that drive important biogeochemical processes (carbon, nitrogen, phosphorus and metals dynamics) in metal mine revegetation remains elusive. Metagenomic sequencing was used to explored vegetation, soil properties, microbial communities, functional genes and their impacts on soil processes during vegetation restoration in a typical Pb-Zn mine. The results showed a clear niche differentiation between bacteria, fungi and archaea. Compared to bacteria and fungi, the archaea richness were more tightly coupled with natural restoration changes. The relative abundances of CAZyme-related, denitrification-related and metal resistance genes reduced, while nitrification, urease, inorganic phosphorus solubilisation, phosphorus transport, and phosphorus regulation -related genes increased. Redundancy analysis, hierarchical partitioning analysis, relative-importance analysis and partial least squares path modelling, indicated that archaea diversity, primarily influenced by available lead, directly impacts carbon dynamics. Functional genes, significantly affected by available cadmium, directly alter nitrogen dynamics. Additionally, pH affects phosphorus dynamics through changes in bacterial diversity, while metal dynamics are directly influenced by vegetation. These insights elucidate natural restoration mechanisms in mine and highlight the importance of archaea in soil processes.202540054196
8558110.9955Mitigating the vertical migration and leaching risks of antibiotic resistance genes through insect fertilizer application. The leaching and vertical migration risks of antibiotic resistance genes (ARGs) from fertilized soil to groundwater poses a significant threat to ecological and public safety. Insect fertilizer, particularly black soldier fly organic fertilizer (BOF), renowned for its minimal antibiotic resistance, emerge as a promising alternative for sustainable agricultural fertilization. This study employs soil-column leaching experiments to evaluate the impact of BOF on the leaching behavior of ARGs. Our results reveal that BOF significantly reduces the leaching risks of ARGs by 22.1 %-49.3 % compared to control organic fertilizer (COF). Moreover, BOF promotes the leaching of beneficial Bacillus and, according to random forest analysis, is the most important factor in predicting ARG profiles (3.02 % increase in the MSE). Further network analysis and mantel tests suggest that enhanced nitrogen metabolism in BOF leachates could foster Bacillus biofilm formation, thereby countering antibiotic-resistant bacteria (ARB) and mitigating antibiotic resistance. In addition, linear regression analysis revealed that Bacillus biofilm-associated genes pgaD (biofilm PGA synthesis protein), slrR (biofilm formation regulator), and kpsC (capsular polysaccharide export protein) were identified as pivotal in the elimination of ARGs, which can serve as effective indicators for assessing antibiotic resistance in groundwater. Collectively, this study demonstrates that BOF as an environmentally friendly fertilizer could markedly reduce the vertical migration risks of ARGs and proposes Bacillus biofilm formation related genes as reliable indicators for monitoring antibiotic resistance in groundwater.202540086570
6919120.9955Enhanced removal of antibiotic resistance genes during chicken manure composting after combined inoculation of Bacillus subtilis with biochar. This study explored the combined effects of Bacillus subtilis inoculation with biochar on the evolution of bacterial communities, antibiotic resistance genes (ARGs), and mobile genetic elements (MGEs) during the composting of chicken manure. The results showed that B. subtilis inoculation combined with biochar increased bacterial abundance and diversity as well as prolonged the compost thermophilic period. Promoted organic matter biodegradation and facilitated the organic waste compost humification process, reduced the proliferation of ARGs by altering the bacterial composition. Firmicutes and Actinobacteriota were the main resistant bacteria related to ARGs and MGEs. The decrease in ARGs and MGEs was associated with the reduction in the abundance of related host bacteria. Compost inoculation with B. subtilis and the addition of biochar could promote nutrient transformation, reduce the increase in ARGs and MGEs, and increase the abundance of beneficial soil taxa.202437778803
6934130.9955Impact of protist predation on bacterial community traits in river sediments. Sediment-associated microbial communities are pivotal in driving biogeochemical processes and serve as key indicators of ecosystem health and function. However, the ecological impact of protist predation on these microbial communities remains poorly understood. Here, sediment microcosms were established with varying concentrations of indigenous protists. Results revealed that protist predation exerted strong and differential effects on the bacterial community composition, functional capabilities, and antibiotic resistance profiles. Higher levels of protist predation pressure increased bacterial alpha diversity and relative abundance of genera associated with carbon and nitrogen cycling, such as Fusibacter, Methyloversatilis, Azospirillum, and Holophaga. KEGG analysis indicated that protist predation stimulated microbial processes related to the carbon, nitrogen, and sulfur cycles. Notably, the relative abundance and associated health risks of antibiotic resistance genes (ARGs), virulence factor genes (VFGs), and mobile genetic elements (MGEs) were affected by predation pressure. Medium protist predation pressure increased the relative abundance and potential risks associated with ARGs, whereas high protist concentrations led to a reduction in both, likely due to a decrease in the relative abundance of ARG-hosting pathogenic bacteria such as Pseudomonas, Acinetobacter, and Aeromonas. These findings provide comprehensive insights into the dynamics of bacterial communities under protist predation in river sediment ecosystems.202540885182
8486140.9954Multidrug-resistant plasmid modulates ammonia oxidation efficiency in Nitrosomonas europaea through cyclic di-guanylate and acyl-homoserine lactones pathways. Antibiotic resistance genes present a major public health challenge and have potential implications for global biogeochemical cycles. However, their impacts on biological nitrogen removal systems remain poorly understood. In the ammonia-oxidizing bacteria Nitrosomonas europaea ATCC 19718 harboring the multidrug-resistant plasmid RP4, a significant decrease in ammonia oxidation efficiency was observed, accompanied by markedly elevated levels of cyclic di-guanylate (c-di-GMP) and acyl-homoserine lactones (AHLs), compared to plasmid-free controls. The results demonstrated that c-di-GMP facilitates the secretion of AHLs, while elevated levels of AHLs inhibit the ammonia oxidation efficiency of Nitrosomonas europaea ATCC 19718. These results revealed that RP4 plasmid significantly impaired ammonia oxidation efficiency through the c-di-GMP and AHLs pathways. Our findings indicate that the multidrug-resistant plasmid RP4 adversely affects the nitrogen metabolism of ammonia-oxidizing bacteria, potentially disrupting the nitrogen biogeochemical cycle and posing substantial ecological and environmental risks.202640945801
8537150.9954Auxin inhibited colonization of antibiotic resistant bacteria in soybean sprouts and spread of resistance genes to endophytic bacteria: Highlighting energy metabolism and immunity mechanism. Antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) are widely in vegetables, posing health risk. Plant auxins are commonly used to enhance vegetable yield, yet the regulatory mechanisms governing their impact on ARGs transmission to endophytic bacteria remain poorly understood. This study tracked ARB colonization and ARGs spread into endophytic bacteria in soybean sprouts exposed to gibberellin (GA) and 6-benzyladenine (BA). The application of GA and BA during the imbibition, sprouting, and germination periods of soybean sprouts all inhibited the transfer of ARB and ARGs. The enrichment of ARB and ARGs in different tissues of soybean sprouts was ranked as seed coat > hypocotyl > cotyledon. BA and GA enhanced the stability of plant cell wall-cell membrane system, promoted energy metabolism in plants, and activated the immunity mechanism. Especially, the plant hormone signal transduction pathway under GA exposure explained 44.8 % and 96.7 % of inhibition on ARB colonization and ARGs transfer, respectively; the plant-pathogen interaction pathway dominated the inhibition of antibiotic resistance under BA exposure, which explained 51 % and 65.9 % of inhibition on ARB colonization and ARGs transfer. These findings provide new insights into ARB colonization in soybean sprouts and the transmission of ARGs to endophytic bacteria under auxin stress.202540252322
6910160.9954Fallow practice mitigates antibiotic resistance genes in soil by shifting host bacterial survival strategies. Soil is a key reservoir of antibiotic resistance genes (ARGs), with cropland soils potentially transferring ARGs through the food chain, posing risks to human health. However, the profile of soil ARGs under different crop rotation patterns, particularly fallow practice aimed at enhancing soil fertility, remains inadequately understood. This study characterized the dynamic distribution of ARGs and survival strategies of ARGs host bacteria in two crop rotation patterns (rice-wheat rotation, RW, and rice-fallow rotation, RF), as well as the factors impacting the ARGs profiles. The results demonstrated ARGs abundance was significantly reduced by 45.04 % in the RF system, especially those related to multidrug resistance. In the RF system, the higher content of soil organic matter (SOM) serves as the primary nutrient source, driving a shift in host bacterial survival strategies toward K-strategists. Concurrently, the depletion of SOM restricts the proliferation of host bacteria, ultimately leading to a reduction in the abundance of ARGs. In contrast, fertilizer application in the RW system leads to NO(3)(-)-N accumulation, thereby favoring the proliferation of r-strategist bacteria that carry ARGs and exacerbating ARGs abundance in the soil. This study suggests that fallow could be an important field management practice for mitigating soil ARGs contamination in cropland.202540555016
6935170.9953Effects of soil protists on the antibiotic resistome under long term fertilization. Soil protists are key in regulating soil microbial communities. However, our understanding on the role of soil protists in shaping antibiotic resistome is limited. Here, we considered the diversity and composition of bacteria, fungi and protists in arable soils collected from a long-term field experiment with multiple fertilization treatments. We explored the effects of soil protists on antibiotic resistome using high-throughput qPCR. Our results showed that long term fertilization had stronger effect on the composition of protists than those of bacteria and fungi. The detected number and relative abundance of antibiotic resistance genes (ARGs) were elevated in soils amended with organic fertilizer. Co-occurrence network analysis revealed that changes in protists may contribute to the changes in ARGs composition, and the application of different fertilizers altered the communities of protistan consumers, suggesting that effects of protistan communities on ARGs might be altered by the top-down impact on bacterial composition. This study demonstrates soil protists as promising agents in monitoring and regulating ecological risk of antibiotic resistome associated with organic fertilizers.202235609845
7911180.9953Biochar induced inhibitory effects on intracellular and extracellular antibiotic resistance genes in anaerobic digestion of swine manure. Distribution of intracellular (iARGs) and extracellular ARGs (eARGs) in manure anaerobic digestion (AD) process coupled with two types of biochar (BC and BP) were investigated. And the effects of biochar on the conjugation transfer of ARGs were explored by deciphering the interaction of biochar with bacterial stress responses, physiological metabolism and antibiotic resistances. Results showed that AD process could effectively remove all the detected eARGs with efficiency of 47.4-98.2%. The modified biochar (BP) with larger specific surface area (SSA) was propitious to decrease the absolute copy number of extracellular resistance genes. AD process could effectively remove iARGs by inhibiting the growth of host bacteria. The results of structural equation models (SEM) indicated that biochar put indirect influences on the fate of ARGs (λ = -0.23, P > 0.05). Analysis on oxidative stress levels, antioxidant capacity, DNA damage-induced response (SOS) response and energy generation process demonstrated that biochar induced the oxidative stress response of microorganisms and enhanced the antioxidant capacity of bacteria. The elevated antioxidant capacity negatively affected SOS response, amplified cell membrane damage and further weakened the energy generation process, resulted in the inhibition of horizontal transfer of ARGs.202235609652
7539190.9953Effect of booster disinfection on the prevalence of microbial antibiotic resistance and bacterial community in a simulated drinking water distribution system. Booster disinfection was often applied to control the microorganism's growth in long-distance water supply systems. The effect of booster disinfection on the changing patterns of antibiotic resistance and bacterial community was investigated by a simulated water distribution system (SWDS). The results showed that the antibiotic resistance bacteria (ARB) and antibiotic resistance genes (ARGs) were initially removed after dosing disinfectants (chlorine and chloramine), but then increased with the increasing water age. However, the relative abundance of ARGs significantly increased after booster disinfection both in buck water and biofilm, then decreased along the pipeline. The pipe materials and disinfectant type also affected the antibiotic resistance. Chlorine was more efficient in controlling microbes and ARGs than chloramine. Compared with UPVC and PE pipes, SS pipes had the lowest total bacteria, ARB concentration, and ARB percentage, mainly due to higher disinfectant residuals and a smoother surface. The significant correlation (r(s) = 0.77, p < 0.001) of the 16S rRNA genes was observed between buck water and biofilm, while the correlations of targeted ARGs were found to be weak. Bray-Curtis similarity index indicated that booster disinfection significantly changed the biofilm bacterial community and the disinfectant type also had a marked impact on the bacterial community. At the genus level, the relative abundance of Pseudomonas, Sphingomonas, and Methylobacterium significantly increased after booster disinfection. Mycobacterium increased after chloramination while decreased after chlorination, indicating Mycobacterium might resist chloramine. Pseudomonas, Methylobacterium, and Phreatobacter were found to correlate well with the relative abundance of ARGs. These results highlighted antibiotic resistance shift and bacterial community alteration after booster disinfection, which may be helpful in controlling potential microbial risk in drinking water.202437949160