RESUMEN
Microplastics (MPs) and antibiotic resistance genes (ARGs) are two types of contaminants that are widely present in the soil environment. MPs can act as carriers of microbes, facilitating the colonization and spread of ARGs and thus posing potential hazards to ecosystem safety and human health. In the present study, we explored the microbial networks and ARG distribution characteristics in different soil types (heavy metal (HM)-contaminated soil and agricultural soil planted with different plants: Bidens pilosa L., Ipomoea aquatica F., and Brassica chinensis L.) after the application of MPs and evaluated environmental factors, potential microbial hosts, and ARGs. The microbial communities in the three rhizosphere soils were closely related to each other, and the modularity of the microbial networks was greater than 0.4. Moreover, the core taxa in the microbial networks, including Actinobacteriota, Proteobacteria, and Myxococcota, were important for resisting environmental stress. The ARG resistance mechanisms were dominated by antibiotic efflux in all three rhizosphere soils. Based on the annotation results, the MP treatments induced changes in the relative abundance of microbes carrying ARGs, and the G1-5 treatment significantly increased the abundance of MuxB in Verrucomicrobia, Elusimicrobia, Actinobacteria, Planctomycetes, and Acidobacteria. Path analysis showed that changes in MP particle size and dosage may indirectly affect soil enzyme activities by changing pH, which affects microbes and ARGs. We suggest that MPs may provide surfaces for ARG accumulation, leading to ARG enrichment in plants. In conclusion, our results demonstrate that MPs, as potentially persistent pollutants, can affect different types of soil environments and that the presence of ARGs may cause substantial environmental risks.
Asunto(s)
Farmacorresistencia Microbiana , Ipomoea , Microplásticos , Microbiología del Suelo , Contaminantes del Suelo , Contaminantes del Suelo/toxicidad , Microplásticos/toxicidad , Ipomoea/genética , Ipomoea/efectos de los fármacos , Farmacorresistencia Microbiana/genética , Rizosfera , Polietileno , Genes Bacterianos/efectos de los fármacos , Brassica/genética , Brassica/efectos de los fármacos , Brassica/microbiología , Bacterias/efectos de los fármacos , Bacterias/genética , Bacterias/clasificación , Suelo/química , Metales Pesados/toxicidad , Microbiota/efectos de los fármacosRESUMEN
Soil deficiency, cyclic erosion, and heavy metal pollution have led to fertility loss and ecological function decline in mining areas. Fertilization is an important way to rapidly replenish soil nutrients, which have a major influence on the soil nitrogen cycling process, but different fertilization regimes have different impacts on soil properties and microbial functional potentials. Here, metagenomic sequencing was used to investigate the different responses of key functional genes of microbial nitrogen cycling to fertilization regimes and explore the potential effects of soil physicochemical properties on the key functional genes. The results indicated that AC-HH (ammonium chloride-high frequency and concentration) treatment significantly increased the gene abundance of norC (13.40-fold), nirK (5.46-fold), and napA (5.37-fold). U-HH (urea-high frequency and concentration) treatment significantly increased the gene abundance of hao (6.24-fold), pmoA-amoA (4.32-fold) norC (7.00-fold), nosZ (3.69-fold), and nirK (6.88-fold). Functional genes were distributed differently among the 10 dominant phyla. The nifH and nifK genes were distributed only in Proteobacteria. The hao gene was distributed in Gemmatimonadetes, Nitrospirae and Proteobacteria. Fertilization regimes caused changes in functional redundancy in soil, and nirK and nirB, which are involved in denitrification, were present in different genera. Fertilization regimes with high frequency and high concentration were more likely to increase the gene abundance at the genus level. In summary, this study provides insights into the taxon-specific response of soil nitrogen cycling under different fertilization regimes, where changes in fertilization regimes affect microbial nitrogen cycling by altering soil physicochemical properties in a complex dynamic environment.
Asunto(s)
Metagenómica , Suelo , Suelo/química , Microbiología del Suelo , Bacterias/genética , Fertilización , NitrógenoRESUMEN
Microplastic contamination has received much attention, especially in agroecosystems. However, since edible crops with different genetic backgrounds may present different responses to microplastics, more research should be conducted and focused on more edible crops. In the current study, pot experiments were conducted to investigate the potential impact of polyethylene microplastic (PE) (particle sizes: 0.5 µm and 1.0 µm, addition levels: 0 (control), 0.5% and 1.0% (w/w)) addition on the physiological and biochemical variations of I. aquatica F.. The results indicated that PE addition caused an increase in the soil pH and NH4+-N and soil organic matter contents, which increased by 10.1%, 29.9% and 50.1% when PE addition at A10P0.5 level (10 g (PE) kg-1 soil, particle size: 0.5 µm). While, PE exposure resulted in a decrease in soil available phosphorus and total phosphorus contents, which decreased by 53.9% and 10.5% when PE addition at A10P0.5 level. In addition, PE addition altered the soil enzyme activities. Two-way ANOVA indicated that particle size had a greater impact on the variations in soil properties and enzyme activities than the addition level. PE addition had a strong impact on the rhizosphere microbial and root endophyte community diversity and structure of I. aquatica F.. Two-way ANOVA results indicated that the particle size and addition level significantly altered the α-diversity indices of both rhizosphere microbial and root endophyte (P < 0.05, P < 0.01 or P < 0.001). Moreover, PE was adsorbed by I. aquatica F., which was clearly observed in the transverse roots and significantly increased the H2O2, ·O2-, malondialdehyde and ascorbic acid contents in both the roots and aerial parts of I. aquatica F., leading to a decrease in I. aquatica F. biomass. Overall, the current study enriches the understanding of the effect of microplastics on edible crops.
Asunto(s)
Ipomoea , Microplásticos , Plásticos/farmacología , Endófitos , Polietileno/farmacología , Rizosfera , Peróxido de Hidrógeno/farmacología , Suelo/química , Fósforo/farmacologíaRESUMEN
In the present study, CaFe-layered double hydroxide corn straw biochar (CaFe-LDH@CSB) was applied to the rhizosphere soil of both pakchoi (Brassica campestris L. ssp. Chinensis Makino, B. campestris L.) and water spinach (Ipomoea aquatic F., I. aquatic F.) to explore and clarify the potential mechanism by which CaFe-LDH@CSB helps vegetables reduce heavy metal (HM) uptake and alleviate oxidative stress. Pot experiments were conducted with CaFe-LDH@CSB applied at four levels: control (CK), T1 (5 g kg-1), T2 (10 g kg-1) and T3 (20 g kg-1). The results indicated that the application of CaFe-LDH@CSB significantly increased pH and decreased the acid-soluble forms of Cd, Pb, Zn and Cu in the rhizosphere soil of both B. campestris L. and I. aquatic F.; decreases of 39.4%, 18.0%, 10.0% and 33.3% in B. campestris L. and of 26.6%, 49.1%, 13.2% and 36.8% in I. aquatic F., respectively, were observed at the T3 level. Moreover, CaFe-LDH@CSB application reduced HM uptake by B. campestris L. and decreased HM-induced oxidative stress through the regulation of soil physicochemical properties and microbial abundance. For B. campestris L., variations in Sordariomycetes helped alleviate the accumulation of HMs in the aerial part, while GSH and -SH from the nonenzymatic system played an important role in scavenging H2O2 in leaves, thus helping B. campestris L. alleviate HM-induced oxidative stress. For I. aquatica F., variations in Vicinamibacteria and Mortierellomycetes helped alleviate the accumulation of HMs in plants, while GSH and PCs from nonenzymatic systems played an important role in removing ·O2- in leaves, thereby helping I. aquatica F. alleviate HM-induced oxidation stress. Our study indicated that the application of CaFe-LDH@CSB improved the rhizosphere soil environment and rebuilt the soil microbial community, helping B. campestris L. and I. aquatica F. alleviate HM-induced oxidative stress and promoting the growth of both vegetables.
Asunto(s)
Brassica , Ipomoea , Metales Pesados , Contaminantes del Suelo , Brassica/química , Zea mays , Cadmio/farmacología , Rizosfera , Peróxido de Hidrógeno , Metales Pesados/análisis , Estrés Oxidativo , Suelo/química , Verduras , Contaminantes del Suelo/análisisRESUMEN
Biochar is an emerging eco-friendly and high-efficiency heavy metal (HM) adsorbent that exhibits satisfactory HM remediation effects in both water and soil environments. However, few studies have investigated the mechanisms and application of biochar in the remediation of combined HM-contaminated environments. Therefore, in the present study, a novel corn straw biochar-loaded calcium-iron layered double hydroxide composite (CaFe-LDH@CSB) was synthesized via the coprecipitation method and applied as a remediation adsorbent to remove HMs in both water and soil environments. The results indicated that the HM adsorption mechanism of CaFe-LDH@CSB in the aquatic phase involved a chemical endothermic adsorption process of functional group-complexed monolayers, dominated by precipitation, ion exchange, complexation and π bond interactions. The maximum adsorption capacity for Cd(II), Pb(II), Zn(II) and Cu(II) in the aqueous phase reached 24.58, 240.96, 57.57 and 39.35 mg g-1, respectively. In addition, application of CaFe-LDH@CSB in the combined HM-contaminated soil treatment helped to increase the soil pH, which increased by 5.1-17.9% in low-contamination (LC) soil and by 7.0-13.9% in high-contamination (HC) soil. Moreover, application of CaFe-LDH@CSB effectively decreased the acid-soluble fraction of HMs and increased the HM residual fraction. The immobilization mechanism of CaFe-LDH@CSB in the soil was concluded to involve pore filling, functional group action and electrostatic interactions. Overall, this study provided a novel LDH biochar composite that can be effectively applied in the remediation of combined HM-contaminated water and soil environments.