Cadmium removal and 2,4-dichlorophenol degradation by immobilized Phanerochaete chrysosporium loaded with nitrogen-doped TiO2 nanoparticles

Phanerochaete chrysosporium has been identified as an effective bioremediation agent for its biosorption and degradation ability. However, the applications of P. chrysosporium are limited owing to its long degradation time and low resistance to pollutants. In this research, nitrogen-doped TiO₂ nanoparticles were loaded on P. chrysosporium to improve the remediation capacity for pollutants. The removal efficiencies were maintained at a high level: 84.2 % for Cd(II) and 78.9 % for 2,4-dichlorophenol (2,4-DCP) in the wide pH range of 4.0 to 7.0 in 60 h. The removal capacity of immobilized P. chrysosporium loaded with nitrogen-doped TiO₂ nanoparticles (PTNs) was strongly affected by the initial Cd(II) and 2,4-DCP concentrations. The hyphae of PTNs became tight, and a large amount of crystals adhered to them after the reaction. Fourier transform infrared spectroscopy showed that carboxyl, amino, and hydroxyl groups on the surface of PTNs were responsible for the biosorption. In the degradation process, 2,4-DCP was broken down into o-chlorotoluene and 4-hexene-1-ol. These results showed that PTNs is promising for simultaneous removal of Cd(II) and 2,4-DCP from wastewater.     

Enhanced aerobic granulation and nitrogen removal by the addition of zeolite powder in a sequencing batch reactor

The aim of this study was to evaluate the impact of zeolite powders on feasibility of rapid aerobic granulation in the column-type sequencing batch reactors. After 90 days' operation, aerobic granular sludge was formed in both reactors by altering influent chemical oxygen demand/nitrogen (COD/N) ratios. R1 with zeolite powders had better removal capabilities of COD and total nitrogen than R2, which was without zeolite powders. Mixed liquor volatile suspended solid concentrations of the two reactors were 7.36 and 5.45 g/L, while sludge volume index (SVI₃₀) values were 34.9 and 47.9 mg/L, respectively. The mean diameters of aerobic granular sludge in the above two reactors were 2.5 and 1.5 mm, respectively. Both reactors achieved the largest simultaneous nitrification and denitrification (SND) efficiency at an influent COD/N ratio of 8; however, R1 exhibited more excellent SND efficiency than R2. The obtained results could provide a novel technique for rapid aerobic granulation and N removal simultaneously, especially when treating nitrogen-rich industrial wastewater.     

钝齿棒杆菌argR基因缺失株构建及其缺失对精氨酸生物合成途径相关基因转录水平的影响

[目的]钝齿棒杆菌AS 1.542中argR基因编码的蛋白ArgR在精氨酸生物合成途径中扮演负调控的角色,但其对相关基因在转录水平的影响还未见报道.因此,本课题组构建了钝齿棒杆菌argR基因缺失株,并在转录水平上比较野生株与缺失株精氨酸生物合成途径相关基因的变化.[方法]采用无痕敲除的方法构建了钝齿棒杆菌argR基因缺失株,并采用荧光定量PCR方法分析缺失株和野生株精氨酸生物合成途径相关基因在转录水平的变化.[结果]利用pK18mobsacB质粒中蔗糖致死基因sacB反向筛选标记及PCR方法成功筛选到钝齿棒杆菌argR基因缺失株;荧光定量PCR结果表明,argR基因缺失株精氨酸生物合成途径中相关基因在转录水平获得大量提高,平均约上调162.13倍.[结论]钝齿棒杆菌精氨酸生物合成途径的相关基因受负调控蛋白ArgR的显著调控,但其基因的敲除并没有引起精氨酸产量发生明显的变化.     

一养殖场中质粒介导喹诺酮类药物耐药基因qnrS的流行特性

摘要:【目的】研究质粒介导喹诺酮类药物耐药基因qnrS在一养殖场中的流行特点。【方法】分离养殖场不同来源样品中的大肠杆菌菌株,利用美国临床标准委员会(CLSI)推荐的药敏纸片法测定菌株耐药情况,通过质粒接合试验获得qnrS阳性接合子,测定qnrS对喹诺酮类药物最小抑菌浓度(MIC)值的影响及其与其它类抗生素耐药性的相关性,利用脉冲场凝胶电泳分析该场中qnrS阳性菌株遗传进化关系。【结果】环境源菌株qnrS的阳性率为29.2%,显著高于禽源菌株基因检出率(13.4%),新进的雏鸡可迅速从养殖场中获得 qnrS基因并在鸡群中流行。qnrS基因可使接合子对喹诺酮类药物MIC值不同程度升高,并且与其它五类抗生素具有相关性,不同qnrS阳性菌株间遗传关系较远,但也存在同一克隆株的流行。【讨论】qnrS基因主要通过质粒的播散等进行水平传播,同时也存在同一克隆株的流行传播。qnrS基因多样性及其水平传播方式造成了它的广泛流行,加强对耐药基因的监测及研究对减少多重耐药菌株的产生具有重要意义。     

Altuibacter lentus gen. nov., sp. nov., a novel member of family Flavobacteriaceae isolated from deep seawater of the South China Sea

A novel chemoheterotrophic, aerobic, Gram-negative, rod-shaped, yellow-pigmented, bacterial strain JLT2010^T was isolated from deep seawater of the South China Sea. Phylogenetic analysis based on the 16S rRNA gene sequences revealed that strain JLT2010^T belongs to the family Flavobacteriaceae and is most closely related to Ulvibacter antarcticus IMCC3101^T with 95.7 % similarity. Some phenotypic characteristics such as the absence of flexirubin-type pigments, growth at 37 °C, hydrolysis of casein differentiated strain JLT2010^T from the genus Ulvibacter as well as other genera in the family Flavobacteriaceae. The DNA G+C content of the strain JLT2010^T was found to be 35.7 mol% and the major respiratory quinone was found to be MK-6. On the basis of phenotypic and phylogenetic features, JLT2010^T is classified as a novel genus and species within the family Flavobacteriaceae, for which the name Altuibacter lentus gen. nov., sp. nov. is proposed. The type strain is JLT2010^T (=JCM 18884^T = CGMCC 1.12167^T).     

A chronocoulometric aptasensor based on gold nanoparticles as a signal amplification strategy for detection of thrombin

A sensitive chronocoulometric aptasensor for the detection of thrombin has been developed based on gold nanoparticle amplification. The functional gold nanoparticles, loaded with link DNA (LDNA) and report DNA (RDNA), were immobilized on an electrode by thrombin aptamers performing as a recognition element and capture probe. LDNA was complementary to the thrombin aptamers and RDNA was noncomplementary, but could combine with [Ru(NH₃)₆]³⁺ (RuHex) cations. Electrochemical signals obtained by RuHex that bound quantitatively to the negatively charged phosphate backbone of DNA via electrostatic interactions were measured by chronocoulometry. In the presence of thrombin, the combination of thrombin and thrombin aptamers and the release of the functional gold nanoparticles could induce a significant decrease in chronocoulometric signal. The incorporation of gold nanoparticles in the chronocoulometric aptasensor significantly enhanced the sensitivity. The performance of the aptasensor was further increased by the optimization of the surface density of aptamers. Under optimum conditions, the chronocoulometric aptasensor exhibited a wide linear response range of 0.1–18.5 nM with a detection limit of 30 pM. The results demonstrated that this nanoparticle-based amplification strategy offers a simple and effective approach to detect thrombin.     

N-Alkyldeoxynojirimycin derivatives with novel terminal tertiary amide substitution for treatment of bovine viral diarrhea virus (BVDV), Dengue,and Tacaribe virus infections

Novel N-alkyldeoxynojirimycins (NADNJs) with two hydrophobic groups attached to a nitrogen linker on the alkyl chain were designed. A novel NADNJ containing a terminal tertiary carboxamide moiety was discovered that was a potent inhibitor against BVDV. Further optimization resulted in a structurally more stable lead compound 24 with a submicromolar EC₅₀ against BVDV, Dengue, and Tacaribe; and low cytotoxicity.     

Glutamate transporter type 3 knockout leads to decreased heart rate possibly via parasympathetic mechanism

Parasympathetic tone is a dominant neural regulator for basal heart rate. Glutamate transporters (EAAT) via their glutamate uptake functions regulate glutamate neurotransmission in the central nervous system. We showed that EAAT type 3 (EAAT3) knockout mice had a slower heart rate than wild-type mice when they were anesthetized. We design this study to determine whether non-anesthetized EAAT3 knockout mice have a slower heart rate and, if so, what may be the mechanism for this effect. Young adult EAAT3 knockout mice had slower heart rates than those of their littermate wild-type mice no matter whether they were awake or anesthetized. This difference was abolished by atropine, a parasympatholytic drug. Carbamylcholine chloride, a parasympathomimetic drug, equally effectively reduced the heart rates of wild-type and EAAT3 knockout mice. Positive immunostaining for EAAT3 was found in the area of nuclei deriving fibers for vagus nerve. There was no positive staining for the EAATs in the sinoatrial node. These results suggest that EAAT3 knockout mice have a slower heart rate at rest. This effect may be caused by an increased parasympathetic tone possibly due to increased glutamate neurotransmission in the central nervous system. These findings indicate that regulation of heart rate, a vital sign, is one of the EAAT biological functions.