Alkylation of metals and the activity of metal‐alkyls†

The biochemical basis for resistance to metal ion toxicity is emerging though it is complicated by the different resistance mechanisms. Several strategies for resistance to toxic metal ions have been identified:

1. The development of energy driven efflux pumps which keep toxic element levels low in the interior of the cell. Such mechanisms have been described for Cd(II) and As(V).

2. Oxidation (e.g. AsO^2‐ to AsO₄ ^3‐) or reduction (e.g. Hg²⁺ to Hg⁰) can enzymatically and intracellularly convert a more toxic form of an element to a less toxic form.

3. The biosynthesis of intracellular polymers which serve as traps for the removal of metal ions from solution such as traps have been described for cadmium, calcium, nickel and copper.

4. The binding of metal ions to cell surfaces.

5. The precipitation of insoluble metal complexes (e.g. metal sulfides and metal oxides) at cell surfaces.

6. Biomethylation and transport through cell‐membranes by diffusion controlled processes.

In this short review I shall discuss the implications of biomethylation as a detoxification mechanism for microorganisms as well as for certain higher organisms.     

Gas chromatography with atomic absorption detection for the determination of alkyl selenide compounds in the breath of mice after administration of different selenium compounds

Quantitative determination of dimethylselenide and dimethyldiselenide in the breath of mice after addition of different selenium compounds to the drinking water is described. Breath samples are collected with a cryogenic trap and analyzed by gas chromatography with atomic absorption spectrometric detection. Detection limits down to 0.2 ng/100 g body weight are obtained.

The pulmonary excretion of selenium metabolites after oral administration via drinking water or after intraperitoneal injection appears to be negligible. The bioconversion of the different selenium species is discussed.     

预氯化对管道生物膜净水效能影响及性能恢复

以环状膜生物反应器BAR模拟实际输水管道,研究了预氯化对管壁生物膜净水效能的影响及其性能恢复过程.结果表明:冲击性加氯后生物膜中异养菌数量迅速降低,几乎检测不出氨氧化细菌,然而,短时的冲击利于生物膜更新,增加了细菌生长潜能,恢复运行240h及144h之后预氯化生物膜中异养菌和氨氧化细菌数量均高于对照组.氯冲击明显降低了生物膜对氨氮的去除效果,余氯为0.5,1.5,3.0mg/L的BAR对氨氮去除率由对照组的79.01%分别降到32.10%、14.46%和9.88%,并出现了显著的亚硝酸盐氮积累,恢复运行120h和216h,管道生物膜即可恢复对氨氮和亚硝酸盐氮的去除效果.余氯量达到1.5mg/L时造成出水总磷浓度升高,恢复运行264h之后4台BAR对总磷的去除率均达到20%以上.氯对生物膜的氧化作用使得出水高锰酸盐指数升高,运行192h之后生物膜净水效果恢复.     

海洋石油降解酵母的分离鉴定与降解特性

以原油为唯一碳源,采用富集培养、平板涂布分离、平板划线纯化及摇瓶复筛等方法,从表层海水或海泥中分离得到2株具有较强石油降解能力的菌株SYB-5和SYB-2. 根据菌落及菌体形态、生理生化特征和分子生物学分析、鉴定显示,SYB-5为季也蒙毕赤酵母(Meyerozyma guilliermondii/Pichia guilliermondii),SYB-2为长孢洛德酵母(Lodderomyces elongisporus). 对2株酵母菌的石油降解性能的研究结果表明,SYB-5和SYB-2以原油组分作为碳源,以(NH₄)₂SO₄和(NH₄)₃PO₄作为氮源,在ρ(NaCl)为30g/L、氧气充足的条件下,生长的最适温度分别为36和32℃,pH均为7.0. 在最适生长条件下,培养5d后的原油降解率分别达到45.8%和34.4%. 当2株菌混合培养时,培养5d的原油降解率可提高到53.9%,培养8d时达到56.4%,说明2株菌利用原油作碳源生长时具有协同作用.      

Degradation kinetics of terephthalic acid wastewater with the hybrid strains constructed with Phanerochaete chrysosporium

The degradation kinetic parameters in terephthalic acid (TPA) wastewater for the hybrid strains of Fhh and Fhhh obtained through the protoplast fusion of the fungi Phanerochaete chrysosporium (PC) and Saccharomyces cerevisiae Y99, and the native bacteria YZ1 were measured in this research. The highest level of the specific degradation rate for Fhhh and Fhh during 20h reaction were 0.2238 and 0.2163 h^‐1, which were higher than that of their three parental strains and that of the anaerobic bacteria reported. It suggested that the abilities of growth and degradation for Fhh and Fhhh in TPA wastewater were better than their three parental strains. They could create potentials for the purification of TPA wastewater with higher efficiency.     

Preparation,characterization and toxic activity of oxovanadium(IV) mixed-ligand complexes

New oxovanadium(IV) mixed-ligand complexes of the general composition [VO(L)(A)], where KHL?=?potassium salt of salicylideneglycine, A¹?=?bis(benzylidene)ethylenediamine, A²?=?bis (acetophenone)ethylenediamine, A³?=?di(2-pyridyl)amine, A⁴?=?bis(benzylidene)-1,8-diaminonaphthalene, A⁵?=?thiophene-o-carboxaldene-aniline, A⁶?=?thiophene-o-carboxaldene-p-anisidine, have been synthesized by the interaction of these ligands with vanadyl sulphate. The mixed-ligand complexes have been characterized on the basis of elemental analysis, magnetic measurements, electronic and infrared spectra. An octahedral structure has tentatively been assigned to all of the mixed-ligand complexes. The mixed-ligand complexes show higher toxic activity against the Salmonella typhi, Escherichia coli and Serratia mercescen as compared to the ligands, vanadyl sulphate and control (dimethyl sulphoxide). The mixed-ligand complexes were also tested against a standard drug (tetracycline).     

活性污泥SBR系统对四环素耐药菌和总四环素的去除特性

通过模拟运行SBR工艺,比较不同四环素进水浓度、运行周期以及氧环境条件对四环素耐药菌及痕量四环素的去除特性.结果表明,痕量四环素的存在会对活性污泥中微生物耐药性产生影响,SBR进水四环素浓度为250μg.L-1时活性污泥中的微生物会逐步变成耐药微生物,而进水中不含四环素时,耐药的微生物会逐步变成非耐药微生物.总四环素的去除效果在好氧条件下周期为12 h时最好,达到90%以上.好氧条件下周期为8 h时每克污泥增加的四环素耐药菌数最多,约为2.89×109CFU.g-1;好氧条件下周期为20 h时为最少,约为1.0×108CFU.g-1,有利于缓解四环素耐药菌的产生.     

活性污泥丝状膨胀早期预警的研究进展

活性污泥法是目前处理污水的一种有效方法,在应用过程中,频频发生的污泥膨胀现象成为影响污水处理效率的难题,对污泥膨胀进行早期预警调控研究,已成为该领域关注的热点问题.本文阐述了丝状菌引起的污泥膨胀预警研究的进展情况,从污泥常规指标测定、形态观察和分子生态学3个方面对丝状污泥膨胀的预警方法进行了综述,对各种方法的优点与不足展开讨论,并在此基础上归纳出一些改进的措施,展望了丝状污泥膨胀预警的应用前景.     

硫酸盐还原菌促进市政污泥厌氧发酵产乙酸

添加各浓度钼酸盐考察不同抑制水平下硫酸盐还原菌(SRB)对市政污泥发酵产酸的作用. 结果表明:在有硫酸盐存在时,未抑制SRB体系中ρ(乙酸)占ρ(总VFAs)的比例可达83%,无丙酸、丁酸积累;而在SRB高抑制水平体系中,ρ(乙酸)只占约40%. 随后以未添加硫酸盐体系为对照,研究了硫酸盐投加方式及在发酵中后期抑制SRB对产物中挥发性脂肪酸(VFAs)成分及其浓度的影响;同时,通过对dsrA酶的编码基因含量定量分析发现,随着硫酸盐的加入,SRB数量速增,产物中丙酸、丁酸先后转化为乙酸,且ρ(乙酸)占ρ(总VFAs)的比例可达90%以上. 添加SRB可作为实现污泥发酵定向累积乙酸的调控手段.      

生物铁-复合菌处理牛仔布印染废水

针对生化池1种或几种菌种启动慢、抗冲击负荷能力差和污泥处理效率低的问题,提出用生物铁法结合生物强化技术、投加复合优势菌的处理方法,应用于牛仔布染整废水处理,COD去除率、脱色率分别达到96%、99%,产泥量可减少80%以上,每吨水节约成本60%,吨水处理费用1.6~1.9元,无二次污染,可推广应用。