Hydrolysis mechanism of carbendazim hydrolase from the strain Microbacterium sp. djl-6F

The carbendazim(MBC) hydrolyzing enzyme gene was cloned and heterologously expressed in Escherichia coli BL21(DE3) from a newly isolated MBC-degrading bacterium strain Microbacterium sp. strain djl-6F. High performance liquid chromatography-mass spectrometry(HPLC-MS)analysis revealed that purified MheI-6F protein catalyzes direct hydrolysis of MBC into2-aminobenzimidazole(2-AB) with a high turnover rate and moderate affinity(Kmof6.69 μmol/L and kcatof 160.88/min) without the need for any cofactors. The optimal catalytic condition of MheI-6F was identified as 45°C, pH 7.0. The enzymatic activity of MheI-6F was found to be diminished by metal ions, and strongly inhibited by sodium dodecyl sulfate(SDS).Through generating amino acid mutations in MheI-6F, Cys16 and Cys222 were identified as the catalytic groups that are essential for the hydrolysis of MBC. This is the first report on the biodegradation of MBC at the enzymatice level.     

Photodegradation of 17α-ethynylestradiol in dissolved humic substances solution: Kinetics, mechanism and estrogenicity variation

17α-Ethynylestradiol(EE2) in natural waters may cause adverse effects on organisms due to its high estrogenic potency. Laboratory studies were performed to study the effects of a local humic acid(LHA), fulvic acid(LFA) and Aldrich humic acid(AHA) on the photochemical behavior and estrogenic potency of EE2. Here photolytic experiments demonstrated that pure aqueous EE2 could undergo direct and self-sensitized photodegradation at a global rate of 0.0068 hr~(-1).Photodegradation rate of EE2 in 5.0 mg/L dissolved humic substances(DHS) was determined to be 0.0274, 0.0296 and 0.0254 hr~(-1) for LHA, LFA and AHA, respectively. Reactive oxygen species(ROS) and triplet dissolved humic substances(~3DHS*) scavenging experiments indicated that the promotion effect of DHS on EE2 photodegradation was mainly aroused by the reactions of HOU(35%–50%),~1O_2(10%) andDHS*(22%–34%). However, the photodegradation of EE2 could also be inhibited when DHS exceeded the threshold of 10 mg/L. Three hydroxylation products of EE2 were identified using GC–MS and their formation pathways were also proposed. In vitro estrogenicity tests showed that EE2 was transformed into chemicals without estrogenic potency. These findings could extend our knowledge on the photochemical behaviors of steroid estrogens in sunlit natural waters.     

白塔堡河不同粒级有机物的三维荧光特征解析

利用三维荧光扫描(3DEEM)和体积积分法(FRI),分析了辽河流域白塔堡河在春汛期水中溶解性有机物(DOM)、小粒径有机物(0.22~0.7μm)和大粒径有机物(>0.7μm)的分布。结果显示:白塔堡河中有机物以芳香类蛋白质和溶解性微生物代谢产物为主,腐植酸类物质含量极少;5类组分在不同粒径有机物中分布相似,在0.22μm以下的DOM中分布最多;溯源分析显示,DOM来源较单一,表现出较强的内源生物降解特性,而颗粒状有机物则表现出内源和陆源的双重特性;多元统计分析显示,白塔堡河点位有机物分布基本上呈现区域性分布特征。     

Visual Modflow模型在地下水污染模拟预测中的应用研究

选取中国东北部某地级市地下水源地补给区,研究地下水运动规律及水中所含污染物迁移转化规律,结合气象、水文、地质、水质等资料,在地下水水均衡计算的基础上,应用地下水有限差分软件Visual Modflow建立了地下水水流水质预测模型,并校正模型.提出的建议对研究区地下水多为战略用水,多属风险防控区,其次是需加强地下水环境准入,以生态红线标准管理,以及加快落实工业污染源、垃圾填埋场等污染防治责任.通过模型预测出未来一定时间段内的地下水流及水质变化情况,为当地政府提出地下水污染防治对策和措施提供了理论依据.     

A giant spider from the Jurassic of China reveals greater diversity of the orbicularian stem group

A large female spider, Nephila jurassica, was described from Middle Jurassic strata of north-east China and placed in the modern genus Nephila (family Nephilidae) on the basis of many morphological similarities, but, as with many ancient fossils, the single specimen lacked synapomorphies of the family (Selden et al. 2011). In order to test the placement within the nephilid phylogenetic tree, Kuntner et al. (2013) calibrated the molecular phylogeny using N. jurassica in three different scenarios based on inferred mitochondrial substitution rates. They concluded that N. jurassica fitted better as a stem orbicularian than a nephilid. Now, a giant male spider has been discovered at the same locality that yielded N. jurassica. The two sexes are considered conspecific based on their similar morphological features, size, and provenance. The male cannot be accommodated in Nephilidae because of its pedipalp morphology, so the new genus Mongolarachne and family Mongolarachnidae are erected for the species. Comparison with possibly related families show that Mongolarachnidae is most likely on the orbicularian stem, close to other cribellate orbicularians (e.g., Deinopoidea), which suggests a greater diversity of cribellate orbicularians during the Middle Jurassic.     

Leptospirosis risk increases with changes in species composition of rat populations

Rats are major reservoirs of leptospirosis and considered as a main threat to biodiversity. A recent introduction of Rattus rattus to the island of Futuna (Western Polynesia) provided the opportunity to test if a possible change in species composition of rat populations would increase the risk of leptospirosis to humans. We trapped rodents on Wallis and Futuna and assessed Leptospira carriage in 357 rodents (Rattus norvegicus, R. rattus, Rattus exulans, and Mus domesticus) from 2008 to 2012. While Leptospira prevalence in rodents and the composition of rat populations on Futuna fluctuated with rainfall, the biomass of Leptospira-carrying rodents has been continuously rising from 2008 to 2012. Our results suggest that the introduction of R. rattus increases the risk to humans being infected with leptospirosis by rats.     

Leadership and employees’ perceived safety behaviours in a nuclear power plant: A structural equation model

Leadership is considered an essential element in guaranteeing the safe running of organizations. The purpose of the present study is to find out how leader behaviours influence employees’ safety behaviours (perceived safety behaviours) in the nuclear field. In an attempt to answer this question, the authors of this research have considered the way this influence is exercised, taking into consideration some important factors like safety culture and safety climate. To achieve this, the empowerment leadership model, based on a behavioural approach to leadership, was used. The sample was made up of 566 employees from a Spanish nuclear power plant. The results indicated that when safety culture was strong, leader behaviour generated a higher safety climate among the members, which predicted their perceived safety behaviours. Support was found for a structural model linking leadership and safety behaviour to safety culture and safety climate. The implications of these findings for the theory of safety and the way they can be put into practice are outlined.     

Sorption of hydrophobic pesticides on a Mediterranean soil affected by wastewater, dissolved organic matter and salts

Irrigation with treated wastewaters as an alternative in countries with severe water shortage may influence the sorption of pesticides and their environmental effects, as wastewater contains higher concentrations of suspended and dissolved organic matter and inorganic compounds than freshwater. We have examined the sorption behaviour of three highly hydrophobic pesticides (the herbicide pendimethalin and the insecticides α-cypermethrin and deltamethrin) on a Mediterranean agricultural soil using the batch equilibration method. We considered wastewater, extracts from urban sewage sludge with different dissolved organic carbon contents, and inorganic salt solutions, using Milli Q water as a control. All pesticides were strongly retained by soil although some sorption occurred on the walls of the laboratory containers, especially when wastewater and inorganic salt solutions were used. The calculation of distribution constants by measuring pesticide concentrations in soil and solution indicated that pendimethalin sorption was not affected whereas α-cypermethrin and deltamethrin retention were significantly enhanced (ca. 5 and 2 times, respectively) when wastewater or salt solutions were employed. We therefore conclude that the increased sorption of the two pesticides caused by wastewater cannot be only the result of its dissolved organic carbon content, but also of the simultaneous presence of inorganic salts in the solution.     

Temporal dynamics of Trichodesmium erythraeum (Cyanophyta) in the National Park "Sistema Arrecifal Veracruzano" in the Gulf of Mexico

Trichodesmium erythraeum Ehrenberg ex Gomont is a microalga worldwide distributed in tropical seas. This filamentous microalga was detected in phytoplankton samples collected in the Protected NaturalArea "Parque Nacional SistemaArrecifal Veracruzano", and because of its ecological importance, its temporal dynamics was studied using net samples (30 microm) collected in one year period. Samples were studied with a light microscope recording the presence, morphological characteristics, life form and relative abundance. Trichodesmium erythraeum occurred as single filaments and was rare in April 2007 and March 2008; as single filaments from May to August and December 2007; as single filaments and small aggregates in September 2007 and January 2008; in aggregates of large size (> 3mm) and high relative abundance in October 2007; and was absence in November 2007 and April 2008. Although the relative abundance of the species was not important comparing with other members of phytoplankton, its occurrence was frequent with a bloom at the beginning of the north winds period. The observed temporal dynamics of this microalga in this coral reef region comes up on the alert in the monitoring red tides programs being implemented in Veracruz coast.