Da Tian

Positive relationship detected between soil bioaccessible organic pollutants and antibiotic resistance genes at dairy farms in Nanjing, Eastern China.

Co-contaminated soils by organic pollutants (OPs), antibiotics and antibiotic resistance genes (ARGs) have been becoming an emerging problem. However, it is unclear if an interaction exists between mixed pollutants and ARG abundance. Therefore, the potential relationship between OP contents and ARG and class 1 integron-integrase gene (intI1) abundance was investigated from seven dairy farms in Nanjing, Eastern China. Phenanthrene, pentachlorophenol, sulfadiazine, roxithromycin, associated ARG genes, and intI1 had the highest detection frequencies. Correlation analysis suggested a stronger positive relationship between the ARG abundance and the bioaccessible OP content than the total OP content. Additionally, the significant correlation between the bioaccessible mixed pollutant contents and ARG/intI1 abundance suggested a direct/indirect impact of the bioaccessible mixed pollutants on soil ARG dissemination. This study provided a preliminary understanding of the interaction between mixed pollutants and ARGs in co-contaminated soils.

Effect of biochar amendment on the control of soil sulfonamides, antibiotic-resistant bacteria, and gene enrichment in lettuce tissues.

Considering the potential threat of vegetables growing in antibiotic-polluted soil with high abundance of antibiotic-resistant genes (ARGs) against human health through the food chain, it is thus urgent to develop novel control technology to ensure vegetable safety. In the present work, pot experiments were conducted in lettuce cultivation to assess the impedance effect of biochar amendment on soil sulfonamides (SAs), antibiotic-resistant bacteria (ARB), and ARG enrichment in lettuce tissues. After 100 days of cultivation, lettuce cultivation with biochar amendment exhibited the greatest soil SA dissipation as well as the significant improvement of lettuce growth indices, with residual soil SAs mainly existing as the tightly bound fraction. Moreover, the SA contents in roots and new/old leaves were reduced by one to two orders of magnitude compared to those without biochar amendment. In addition, isolate counts for SA-resistant bacterial endophytes in old leaves and sul gene abundances in roots and old leaves also decreased significantly after biochar application. However, neither SA resistant bacteria nor sul genes were detected in new leaves. It was the first study to demonstrate that biochar amendment can be a practical strategy to protect lettuce safety growing in SA-polluted soil with rich ARB and ARGs.

Human migration activities drive the fluctuation of ARGs: Case study of landfills in Nanjing, eastern China

Landfills are perfect sites to study the effect of human migration on fluctuation of antibiotic resistance genes (ARGs) as they are the final destination of municipal waste. For example, large-scale human migration during the holidays is often accompanied by changes in waste dumping having potential effects on ARG abundance. Three landfills were selected to examine fluctuation in the abundance of fifteen ARGs and Intl1 genes for 14 months in Nanjing, eastern China. Mass human migration, the amount of dumped waste and temperature exerted the most significant effects on bimonthly fluctuations of ARG levels in landfill sites. As a middle-sized cosmopolitan city in China, millions of college students and workers migrate during holidays, contributing to the dramatic increases in waste production and fluctuation in ARG abundances. In line with this, mass migration explained most of the variation in waste dumping. The waste dumping also affected the bioaccessibility of mixed-compound pollutants that further positively impacted the level of ARGs. The influence of various bioaccessible compounds on ARG abundance followed the order: antibiotics>nutrients>metals>organic pollutants. Concentrations of bioaccessible compounds were more strongly correlated with ARG levels compared to total compound concentrations. Improved waste classification and management strategies could thus help to decrease the amount of bioaccessible pollutants leading to more effective control for urban ARG dissemination.

Feasibility of lettuce cultivation in sophoroliplid-enhanced washed soil originally polluted with Cd, antibiotics, and antibiotic-resistant genes.

Vegetable cultivation in soils polluted with heavy metals, antibiotics and a high abundance of antibiotic-resistance genes (ARGs) can seriously threaten human health through the food chain. Therefore, novel techniques that not only remediate soil, but also ensure food security are urgently required. In the present study, two successive washings with 20gL(-1) of sophoroliplid solution plus ultrasonication (35kHz) were effective in extracting 71.2% Cd, 88.2% tetracycline, 96.6% sulfadiazine, and 100% roxithromycin. Simultaneously, relative abundance of ARGs (tetM, tetX, sulI, and sulII) was decreased to 10(-7)-10(-8) (ARG copies/16S copies). Further, lettuce cultivation in the 2nd washed soil showed significant improvement in vegetable growth indices (fresh/dry weight, root surface area, chlorophyll content and soluble protein content) and a decrease in isolate counts for antibiotic-resistant bacterial endophytes and ARG abundance in lettuce tissues. This combined cleanup strategy provides an environmentally friendly technology for ensuring vegetable security in washed soils.

Calcined Eggshell Waste for Mitigating Soil Antibiotic-Resistant Bacteria/Antibiotic Resistance Gene Dissemination and Accumulation in Bell Pepper

The combined accumulation of antibiotics, heavy metals, antibiotic-resistant bacteria (ARB)/antibiotic resistance genes (ARGs) in vegetables has become a new threat to human health. This is the first study to investigate the feasibility of calcined eggshells modified by aluminum sulfate as novel agricultural wastes to impede mixed contaminants from transferring to bell pepper (Capsicum annuum L.). In this work, calcined eggshell amendment mitigated mixed pollutant accumulation in bell pepper significantly, enhanced the dissipation of soil tetracycline, sulfadiazine, roxithromycin, and chloramphenicol, decreased the water-soluble fractions of antibiotics, and declined the diversity of ARB/ARGs inside the vegetable. Moreover, quantitative polymerase chain reaction analysis detected that ARG levels in the bell pepper fruits significantly decreased to 10(-10) copies/16S copies, indicating limited risk of ARGs transferring along the food chain. Furthermore, the restoration of soil microbial biological function suggests that calcined eggshell is an environmentally friendly amendment to control the dissemination of soil ARB/ARGs in the soil-vegetable system.

Impact of bioaccessible pyrene on the abundance of antibiotic resistance genes during Sphingobium sp.- and sophorolipid-enhanced bioremediation in soil.

Soils are exposed to various types of chemical contaminants due to anthropogenic activities; however, research on persistent organic pollutants and the existence of antibiotic resistance genes (ARGs) is limited. To our knowledge, the present work for the first time focused on the bioremediation of soil co-contaminated with pyrene and tetracycline/sulfonamide-resistance genes. After 90 days of incubation, the pyrene concentration and the abundance of the four ARGs (tetW, tetM, sulI, and sulII) significantly decreased in different treatment conditions (p<0.05). The greatest pyrene removal (47.8%) and greatest decrease in ARG abundance (from 10(-7) to 10(-8) ARG copies per 16S rRNA copy) were observed in microcosms with a combination of bacterial and sophorolipid treatment. Throughout the incubation, pyrene bioaccessibility constantly declined in the microcosm inoculated with bacteria. However, an increased pyrene bioaccessibility and ARG abundance at day 40 were observed in soil treated with sophorolipid alone. Tenax extraction methods and linear correlation analysis indicated a strong positive relationship between the rapidly desorbing fraction (Fr) of pyrene and ARG abundance. Therefore, we conclude that bioaccessible pyrene rather than total pyrene plays a major role in the maintenance and fluctuation of ARG abundance in the soil.

Dynamic interplay between microbial denitrification and antibiotic resistance under enhanced anoxic denitrification condition in soil

Mixed contamination of nitrate and antibiotics/antibiotic-resistant genes (ARGs) is an emerging environmental risk to farmland soil. This is the first study to explore the role of excessive anthropogenic nitrate input in the anoxic dissipation of soil antibiotic/ARGs. During the initial 10 days of incubation, the presence of soil antibiotics significantly inhibited NO3- dissipation, N2O production rate, and denitrifying genes (DNGs) abundance in soil (pxa0<xa00.05). Between days 10 and 30, by contrast, enhanced denitrification clearly prompted the decline in antibiotic contents and ARG abundance. Significantly negative correlations were detected between DNGs and ARGs, suggesting that the higher the DNG activity, the more dramatic is the denitrification and the greater are the antibiotic dissipation and ARG abundance. This study provides crucial knowledge for understanding the mutual interaction between soil DNGs and ARGs in the enhanced anoxic denitrification condition.

Feasibility of sulfate-calcined eggshells for removing pathogenic bacteria and antibiotic resistance genes from landfill leachates

High abundance of human pathogen and antibiotic resistance genes (ARGs) in landfill leachate has become an emerging threat against human health. Therefore, sulfate- and calcination-modified eggshells as green agricultural bioresource were applied to test the feasibility of removing pathogenic bacteria and ARGs from leachate. The highest removal of Escherichia coli (E. coil) and gentamycin resistant gene (gmrA) from artificial contaminated landfill leachate was achieved by the application of eggshell with combined treatment of sulfate and calcination. The 16S and gmrA gene copies of E. coil declined significantly from 1.78E8±8.7E6 and 4.12E8±5.9E6 copies mL-1 to 1.32E7±2.6E6 and 2.69E7±7.2E6 copies mL-1, respectively, within 24h dynamic adsorption equilibrium process (p<0.05). Moreover, according to the Langmuir kinetic model, the greatest adsorption amount (1.56×109 CFU E. coil per gram of modified eggshells) could be obtained at neutral pH of 7.5. The optimal adsorption eggshells were then screened to the further application in three typical landfill leachates in Nanjing, eastern China. Significant decrease in species and abundance of pathogenic bacteria and ARGs (tet, sul, erm, qnr, and ampC) indicated its great efficiency to purify landfill leachates. This study demonstrated that sulfate-calcined eggshells can be an environmentally-friendly and highly efficient bioadsorbent to the management of reducing dissemination risk of pathogen and ARGs in landfill leachate.

Induced biotransformation of lead (II) by Enterobacter sp. in SO 4 -PO 4 -Cl solution

Pb is a toxic heavy metal in contaminated soil and water, resulted from industrial activities, mine exploration, etc. Phosphate solubilizing bacteria are able to secrete organic acids and further to enhance the solubility of phosphates. Enterobacter. sp and geological fluorapatite (FAp) were applied to investigate the biotransformation of Pb2+ in solution with SO42-, PO43-, and Cl- species by ICP-OES, ATR-IR, XRD, and SEM. Enterobacter. sp can lower pH of the medium to ∼4. Meanwhile, >90% mobile Pb (declining from 1000 to 30u202fppm) was immobilized via the combination of Enterobacter. sp and FAp. With the addition of FAp and Pb, pyromorphite was precipitated, but with relatively low content. In contrast, abundant anglesite mineral was formed in such weakly acidic system. These anglesite crystals can even absorb phosphates particles onto their surface. Additionally, geochemical modeling confirms the formation of anglesite and cerussite under weekly acidic and alkalic condition respectively, especially when H2PO4- concentration <10-8 mM. Furthermore, the presence of Cl- in solution leads to the formation of chloropyromorphite when H2PO4- concentration >10-12 mM, especially under neutral environment. This study explored the biotransformation of Pb in SO4-PO4-Cl aqueous system and hence provided guidance on bioremediation of Pb by bacteria and FAp.

Feasibility of an enhanced washing process to extract PBDEs/heavy metals/antibiotics from antibiotic resistance gene-affected soil with aqueous DNA followed by microbial augmentation

PurposeRemediation of polybrominated diphenyl ethers (PBDEs)/heavy metals/antibiotics mixed contaminated soil with high abundance of antibiotic resistance genes (ARGs) has being greatly challenging.Materials and methodsAn elevated soil washing procedure was developed to investigate the potential of applying DNA solution to extract PBDEs, Cu, Pb, tetracycline, and sulfadiazine from a high abundance of ARG-affected soil, followed by microbial augmentation to restore the microbiological functioning of washed soil.Results and discussionTwo successive washings with 15xa0gxa0L−1 DNA solution plus ultrasonication (25xa0kHz for 15xa0min) were optimal for extracting 80.6xa0% BDE28, 85.2xa0% BDE47, 64.7xa0% Cu, 60.3xa0% Pb, 100xa0% tetracycline, and 100xa0% sulfadiazine. Simultaneously, the ARG abundance decreased to the level of 10−7–10−8 (ARGs copies/16S copies). Moreover, combined treatment with PBDE-degrading bacteria inoculation and nutrient application for 3xa0months to the second washed soil resulted in the further degradation of residual BDE28 and BDE47. Furthermore, the bacterial community composition was restored and the transfer risk of residual pollutants was limited, as indicated by high-throughput sequencing technology analysis and heavy metals stability model evaluation.ConclusionsThe combined cleanup technology is an environmentally friendly and effective technology to remediate mixed contaminated soils.