Occurrence and distribution of antibiotic resistance genes in the sediments of the East China Sea bays

The coastal area of the East China Sea has experienced rapid urbanization and industrialization in China since 1980 s, resulting in severe pollution of its environments.Antibiotic resistance genes(ARGs) are regarded as a kind of emerging pollutant with potential high risk. The sediment samples were collected from Hangzhou Bay(HB),Xiangshan Bay(XB), and Taizhou Bay(TB) to investigate the spatial occurrence and distribution of 27 ARGs and class I integron–integrase gene(intI1) in the coastal area of the East China Sea. The PCR results showed the frequent presence of 11 ARGs and intI1 in the sediments of the three bays. The qPCR results further showed that sulfonamide resistance was the most prevalent ARG type and antibiotic target replacement and protection were the most important resistance mechanisms in the sediments. Regarding the subtype of ARGs, sulI, tetW, and dfrA13 were the most abundant ARGs, in which sulI was higher in TB(based on both the absolute and relative abundances) and dfrA13 was higher in HB(based on the relative abundances). The network analysis revealed that intI1 had significant correlations with tetC, sulI, sulII, and blaPSE-1. Oil was the key connected factor, which had positive connections with sulI, sulII, and blaPSE-1. In addition, the joint effect of heavy metals and nutrients organic pollutants might be crucial for the fate of ARGs in the coastal sediments.     

Low nutrient levels as drinking water conditions can reduce the fitness cost of efflux pump-mediated ciprofloxacin resistance in Pseudomonas aeruginosa

The long-term persistence of antibiotic resistance in the environment, especially in drinking water, is a public health concern. Expression of an efflux pump, an important mechanism of resistance to antibiotics, usually confers a fitness cost in bacteria. In this study, we aimed to determine why antibiotic resistance conferred by overexpression of an efflux pump persisted in low-nutrient environments(TOC 10 mg/L) such as drinking and source water in which antibiotic selective pressure might be very low or even absent.Competition experiments between wild-type Pseudomonas aeruginosa and ciprofloxacinresistant mutants revealed that the fitness cost of ciprofloxacin resistance significantly decreased(p 0.05) under low-nutrient(0.5 mg/L total organic carbon(TOC)) relative to high-nutrient(500 mg/L TOC) conditions. Mechanisms underlying this fitness cost were analyzed. The mexD gene expression in resistant bacteria(cip_3 strain) was significantly lower(p 0.05) in low-nutrient conditions, with 10 mg/L TOC((8.01 ± 0.82)-fold), than in high-nutrient conditions, with 500 mg/L TOC((48.89 ± 4.16)-fold). Moreover, rpoS gene expression in resistant bacteria((1.36 ± 0.13)-fold) was significantly lower(p 0.05) than that in the wild-type strain((2.78 ± 0.29)-fold) under low-nutrient conditions(10 mg/L TOC),suggesting a growth advantage. Furthermore, the difference in metabolic activity between the two competing strains was significantly smaller(p 0.05) in low-nutrient conditions(5 and 0.5 mg/L TOC). These results suggest that nutrient levels are a key factor in determining the persistence of antibiotic resistance conferred by efflux pumps in the natural environment with trace amounts or no antibiotics.     

Distribution and relationship between antimicrobial resistance genes and heavy metals in surface sediments of Taihu Lake, China

Heavy metals, pharmaceuticals, and other wastes released into the environment can significantly influence environmental antibiotic resistance. We investigated the occurrence of 22 antimicrobial resistance genes(ARGs) and 10 heavy metal concentrations, and the relationship between ARGs and heavy metals in surface sediment from seven sites of Lake Taihu. The results showed significant correlations(p 0.05) between sediment ARG levels,especially for tetracycline and sulfonamides(e.g., tet(A), tet(D), tet(E), tet(O), sul1, sul2 and int-1) and specific heavy metals(Fe, Mn, Cr, Cu, Zn, among others) in the Lake. In the surface sediments, heavy metals showed an interaction with resistance genes, but the strength of interaction was diminished with increasing depth. For most of the heavy metals, the concentration of elements in the top sediments was higher than that in other depths.Tetracycline resistance genes(tet(A), tet(B), tet(D), tet(E) and tet(O), β-lactam resistance genes(SHV, TEM, CTX, OXA and OXY) and sulfonamide resistance genes(sulA, sul1, sul2, sul3 and int-1) were detected. They showed a trend which inferred a statistically significant increase followed by decreases in the relative abundance of these ARGs(normalized to 16 S rRNA genes) with increasing depth. This study revealed that tet(A), tet(O), TEM, OXY, int-1, sul1 and sul3 were widespread in surface sediments with high abundance, indicating that these genes deserve more attention in future work.     

Fate of antibiotics and antibiotic resistance genes in a full-scale restaurant food waste treatment plant: Implications of the roles beyond heavy metals and mobile genetic elements

Is our food safe and free of the crisis of antibiotics and antibiotic resistance(AR)?And will the derived food waste(FW) impose AR risk to the environment after biological treatment? This study used restaurant FW leachates flowing through a 200 tons-waste/day biological treatment plant as a window to investigate the fate of antibiotics and antibiotic-resistance genes(ARGs) during the acceptance and treatment of FW. Sulfonamides(sulfamethazine, sulfamethoxazole) and quinolones(ciprofloxacin, enrofloxacin, ofloxacin) were detected during FW treatment, while tetracyclines, macrolides and chloramphenicols were not observable. ARGs encoding resistance to sulfonamides, tetracyclines and macrolides emerged in FW leachates.Material flow analysis illustrated that the total amount of antibiotics(except sulfamethazine) and ARGs were constant during FW treatment processes. Both the concentration and total amount of most antibiotics and ARGs fluctuated during treatment, physical processes(screening, centrifugation, solid–liquid and oil–water separation) did not decrease antibiotic or ARGs concentrations or total levels permanently; the affiliated wastewater treatment plant appeared to remove sulfonamides and most ARGs concentrations and total amount. Heavy metals Ni,Co and Cu were important for disseminating antibiotics concentrations and MGEs for distributing ARGs concentrations. Humic substances(fulvic acids, hydrophilic fractions), C-associated and N-associated contents were essential for the distribution of the total amounts of antibiotics and ARGs. Overall, this study implied that human food might not be free of antibiotics and ARGs, and FW was an underestimated AR pool with various determinants. Nonetheless, derived hazards of FW could be mitigated through biological treatment with well-planned daily operations.     

混凝沉淀-UF工艺去除二级出水中ARGs效能研究

为了研究混凝沉淀-UF工艺对城市污水处理厂二级出水中ARGs（抗生素抗性基因）去除的影响,以PACl（聚合氯化铝）和PFS（聚合硫酸铁）作为混凝剂,采用qPCR（实时荧光定量聚合酶链式反应）和EEM（三维荧光光谱）等分析混凝沉淀-UF工艺对ARGs的削减及其影响因素.结果表明:① PACl、PFS投加量（分别以Al、Fe计,下同）分别为0.85、0.50 mmol/L时,与直接UF工艺相比,混凝沉淀-UF工艺对水中各类ARGs的去除量高2~3个数量级,其中PACl-UF工艺的效果更好,去除量为2.51~3.52个数量级;对水中DOC（溶解性有机碳）、富里酸类及溶解性微生物代谢产物的去除效果更好,DOC去除率由18%升至36%.②直接UF、PACl-UF、PFS-UF 3种工艺膜进、出水的线性拟合结果显示,ARGs浓度与ρ（DOC）、16S rDNA浓度均呈显著正相关.研究显示,混凝沉淀-UF工艺可以有效去除二级出水中的ARGs,且有机物、16S rDNA的去除有助于ARGs的削减.      

大气臭氧污染对冬小麦气孔吸收通量的影响机制及其时空格局

近地层臭氧作为一种二次污染物,其不断增加的浓度及其对作物的影响已经成为各国政府和公众关注的焦点.本文以冬小麦为研究对象,基于大田OTC试验,对OTC内气象因子和气孔导度进行连续观测.引进气孔导度模型,并进行本地参数化研究,结合通量模型,研究冬小麦气孔臭氧吸收通量的变化特征,并对江苏省各市冬小麦气孔导度和O_3吸收通量的时空分布进行模拟.结果表明,O_3浓度增加会限制其叶片气孔导度,浓度越高,限制作用越明显;利用修订后的气孔导度模型对冬小麦叶片气孔导度进行模拟,表明模型解释了实测气孔导度90%、77%和83%的变异性.结合通量模型对冬小麦气孔O_3通量进行模拟,则CK(约为53.67 n L·L~(-1))、100 n L·L~(-1)和150 n L·L~(-1)O_3浓度处理下冬小麦在整个O_3熏期的累积吸收通量分别为6.42、12.27和13.90 mmol·m-2;江苏地区冬小麦在其生长季期间O_3浓度呈逐渐增加的趋势,冬小麦平均气孔导度的大小表现为:中期后期前期的时间变化特点,在整个中期时段气孔O_3累积吸收通量最多.     

Purification, characterization and application of dual coagulants containing chitosan and different Al species in coagulation and ultrafiltration process

The objective of this study was to investigate the effect of different Al species and chitosan (CS) dosages on coagulation performance, floc characteristics (floc sizes, strength and regrowth ability and fractal dimension) and membrane resistance in a coagulation–ultrafiltration hybrid process. Results showed that different Al species combined with humic acid in diverse ways. Al_a had better removal efficiency, as determined by UV₂₅₄ and dissolved organic carbon, which could be further improved by the addition of CS. In addition, the optimal dosage of different Al species was determined to be 4.0 mg/L with the CS concentration of 1.0 mg/L, by orthogonal coagulation experiments. Combining Al_a/Al_b/Al_c with CS resulted in larger flocs, higher recovery, and higher fractal dimension values corresponding to denser flocs; in particular, the floc size at the steady state stage was four times larger than that obtained with Al species coagulants alone. The results of ultrafiltration experiments indicated that the external fouling percentage was significantly higher than that of internal fouling, at around 85% and 15%, respectively. In addition, the total membrane resistance was significantly decreased due to CS addition.     

梅花鹿养殖场抗生素抗性基因分布特征

梅花鹿养殖是近年来我国南方地区出现的新兴养殖业.为探究梅花鹿养殖对养殖环境抗生素抗性基因的影响,采用高通量荧光定量PCR研究了抗生素抗性基因在养殖场区对照土壤、梅花鹿新鲜粪便、梅花鹿粪便堆肥产物和施用堆肥菜地土壤中的分布、丰度和多样性.结果表明,抗性基因的绝对丰度梅花鹿粪便堆肥产物梅花鹿新鲜粪便施用堆肥菜地土壤养殖场区对照土壤,抗生素抗性基因在4种环境样品中具有不同分布格局;梅花鹿养殖场环境中抗性基因丰度与可移动基因元件丰度显著相关(P0.05),表明可移动基因元件可能加快了抗性基因的水平转移过程,促进了抗性基因的迁移、传播和富集,加剧了养殖环境抗生素抗性基因污染.     

海洋大气环境中含稀土耐候钢暴露1年的耐蚀性能研究

目的研究普通耐候钢和含稀土耐候钢(Cu-P-RE钢)的耐蚀性能。方法通过腐蚀速率测试、电子探针、金相制作等技术手段探讨稀土对耐候钢耐蚀性能的影响。结果在耐候钢中加入稀土后,含稀土耐候钢比普通耐候钢的锈层更加连续致密、裂纹孔洞数量减少。结论含稀土锈层对腐蚀介质的物理阻挡作用相应改善,可有效抑制腐蚀介质对钢基体的进一步腐蚀,对基体的保护能力增强。稀土元素的存在有利于降低耐候钢在青岛海洋大气环境下的腐蚀速率,改善耐候钢的耐大气腐蚀性能。     

适用于DOT4制动液环境丙烯酸氨基烤漆的制备与性能研究

目的提高丙烯酸氨基烤漆的耐DOT4制动液性能,并保留其良好的耐冲击性能。方法通过制备高酸价的丙烯酸树脂并与一定量的高分子量的环氧树脂(E20)共混改性后,与氨基树脂混合加热固化制备涂层,分别采用DOT4制动液高温浸泡法、划格法和冲击试验测涂层的耐制动液、附着力和耐冲击性能。结果成功制备了酸价为60 mg KOH/g与固含量为60%高酸价丙烯酸树脂。当高酸价丙烯酸树脂以质量比为3:1的比例与氨基树脂混合并加入4%的E20时制备的涂层具有优异的综合性能,涂层的附着力为0级,耐冲击性能为50 kg·cm,在100℃的DOT4制动液中浸泡7 h后,涂层不脱落,不起泡。结论该方法适用于提高丙烯酸氨基烤漆的耐DOT4制动液性能。