重金属胁迫培养对2种细菌生长曲线的影响

[目的]研究重金属胁迫培养对2种细菌生长曲线的影响.[方法]以大肠杆菌和枯草芽孢杆菌2种典型细菌为试验材料,采用传统培养方法,选择5种重金属离子Cu2+、Hg2+、Pb2+、Cd2+、Cr6+在不同浓度下对其进行胁迫培养,通过测定2种细菌的生长曲线,研究外源性重金属对2种细菌生长的影响.[结果]Hg2+、Cd2+毒性较强,2种细菌的增殖在高浓度时受到抑制,G+比G-更为敏感;当重金属浓度＞50 mg/L后,5种重金属的对2种细菌的毒性顺序为Hg2+＞Cd2+＞Cu2+＞Cr6+≈Pb2+.[结论]该研究结果为进一步研究重金属对环境及生态系统的影响奠定基础.     

“工业排放重金属监测技术”项目通过技术验收

正近日,"863"计划资源环境技术领域"工业排放重金属监测技术"项目通过技术验收。该项目开发了工业排放重金属监测技术和产品,在工业环境空气重金属的X射线荧光监测方法、固体废弃物重金属的激光诱导击穿光谱检测技术、废水重金属监测新型电极和复杂水样预处理、烟气重金属采样与快速分析技术等方面取得了实     

基于ArcGIS土壤重金属迁移模型研究进展

工业生产活动的增加造成了土壤和地下水中的重金属污染不断加剧。由于重金属在土壤中滞留时间长、迁移性差,且难以生物降解,导致土壤中重金属元素含量超标。土壤重金属迁移规律复杂,治理难度大,修复费用高,研究土壤重金属迁移模型,以可视化形式精准判定污染区域,可以为科学污染防治和土壤资源保护提供依据。全面阐述土壤重金属迁移扩散模型的研究进展,探讨基于ArcGIS二次开发的相关研究,包括土壤污染风险评估、修复及重金属迁移等。同时,分析现有研究不足之处,展望未来土壤重金属迁移模型的发展趋势。     

某铅锌冶炼企业废水处理工艺及应用

根据铅锌冶炼企业废水产生特点,采用生物制剂去除重金属与双膜法脱盐相结合的处理工艺,并实现出水回用;与传统的石灰法等工艺相比,生物制剂处理后废水中铅、砷、镉等重金属离子去除率明显提高,且含重金属污泥量大大减少。     

重金属废水处理技术研究进展

废水中的重金属具有难降解性、长期积累性、毒害性、代谢困难及隐蔽性等特点,对生态环境和人类健康都构成了风险。目前常用的重金属废水处理方法包括稀释法、化学沉淀法、混凝-絮凝法及吸附法,本文对这些方法的除重金属机理、应用优缺点及进展进行了详细介绍,指出其普遍存在运行成本高、处理不彻底、可能造成二次污染等问题。认为废水处理-重金属回收等联合处理技术才能够解决目前复合污染问题,并取得良好的经济和社会效益;还应加强水处理技术机理研究,同时完善重金属废水修复工艺,开发出适用于实际排放的重金属含量范围内废水处理技术。另外,需在易受污染区域建立长期的重金属废水环境检测生态站,为重金属废水修复提供基础保障;应注重水处理技术评价的环境效应,避免二次污染。     

铁基材料修复重金属污染农田土壤的研究进展

铁基材料可通过降低重金属的有效态比例,降低土壤重金属的生物可利用性,控制重金属毒性危害,具有来源广、生产成本低、稳固效果优良等优势。参阅国内外相关文献,对铁基材料在农田土壤修复过程中存在的作用机理如吸附沉淀、还原、氧化等,以及影响因素如土壤水分、pH、有机质含量和离子竞争等进行了阐述。对铁基材料在土壤重金属污染的修复潜力以及未来研究方向进行了相关展望。     

矿山开采区周边含重金属污染物土壤治理与修复探究

由于矿山开采区周边土壤重金属污染严重,为此提出矿山开采区周边含重金属污染物土壤治理与修复探究。首先从措施、制度、管理等方面提出了矿山开采区周边含重金属污染物土壤治理策略,然后通过扩大矿山开采区周边植物种植面积和引入生物学防控技术,吸附土壤中重金属污染物,起到矿山开采区周边含重金属污染物土壤修复作用。     

锰矿区土壤重金属污染问题与应对研究

土壤重金属污染是现阶段重要的环境污染问题,对人们的生活工作产生了重要的影响。某城市矿业活动的频繁导致土壤重金属超标,严重影响了当地的生态环境。为此,以某城市锰矿区土壤重金属环境污染情况为例,通过数据采集、测定、分析等,借助科学的土壤污染评价分析方法,分析该地区锰矿区土壤重金属污染问题,并针对锰矿区土壤重金属污染问题提出相应的解决策略,旨在减少环境重金属污染。     

重金属污染土壤修复技术研究进展

本文通过文献分析,介绍了重金属污染土壤常用的物理修复技术、生物修复技术和化学修复技术等技术原理、应用进展及制约因素等,并指出了重金属污染土壤修复技术的研究方向和发展趋势,为重金属污染土壤修复技术的理论研究和应用提供参考。     

河南涉重金属重点行业污染防控工作方案出炉

正10月11日,河南省环保厅印发《河南省涉重金属重点行业污染防控工作方案》,明确提到,到2020年底,全省重点行业重点重金属排放量比2013年下降12%;集中解决威胁群众健康和农产品质量安全的突出重金属污染问题,进一步遏制重金属污染造成的环境风险;建立健全企事业单位重金属污染物排放总量控制制度。为实现上述目标,《方案》提出了严格涉重金属行业项目环境准入、开展涉镉等重金属行业企业排     

Gene cloning and characterization of recombinant RNase HII from a hyperthermophilic archaeon

We have cloned the gene encoding RNase HII (RNase HIIPk) from the hyperthermophilic archaeon Pyrococcus kodakaraensis KOD1 by screening of a library for clones that suppressed the temperature-sensitive growth phenotype of an rnh mutant strain of Escherichia coli. This gene was expressed in an rnh mutant strain of E. coli, the recombinant enzyme was purified, and its biochemical properties were compared with those of E. coli RNases HI and HII. RNase HIIPk is composed of 228 amino acid residues (molecular weight, 25,799) and acts as a monomer. Its amino acid sequence showed little similarity to those of enzymes that are members of the RNase HI family of proteins but showed 40, 31, and 25% identities to those of Methanococcus jannaschii, Saccharomyces cerevisiae, and E. coli RNase HII proteins, respectively. The enzymatic activity was determined at 30 degreesC and pH 8.0 by use of an M13 DNA-RNA hybrid as a substrate. Under these conditions, the most preferred metal ions were Co2+ for RNase HIIPk, Mn2+ for E. coli RNase HII, and Mg2+ for E. coli RNase HI. The specific activity of RNase HIIPk determined in the presence of the most preferred metal ion was 6. 8-fold higher than that of E. coli RNase HII and 4.5-fold lower than that of E. coli RNase HI. Like E. coli RNase HI, RNase HIIPk and E. coli RNase HII cleave the RNA strand of an RNA-DNA hybrid endonucleolytically at the P-O3' bond. In addition, these enzymes cleave oligomeric substrates in a similar manner. These results suggest that RNase HIIPk and E. coli RNases HI and HII are structurally and functionally related to one another.     

Acinetobacter isolates from environmental sampling in hospitals (author's transl)

By environmental culturing Acinetobacter could be isolated from human sources and wet sites as well as from air and dry surfaces. In variety "anitratus" strains from patients and hospital personal resistance against antibiotics and metal salts was more dominant than in other strains. Acinetobacter strains were more tolerant of dryness than E. coli but less than Micrococcus luteus. By repeated contacts Acinetobacteres could be recovered from contaminated surfaces of polyvinyl chloride in significantly higher numbers than from paving tile.     

Relative effects of bacterial and protozoan predators on survival of Escherichia coli in estuarine water samples

The relative effect of protozoan and bacterial predators on the survival of Escherichia coli in estuarine water samples was examined. Predacious protozoa exerted their major influence on E. coli destruction during the first 2 days of a 10-day-decline period. Inhibition of protozoa after day 2 had little effect on E. coli survival. Bacterial predators also contributed to E. coli destruction but in natural estuarine water samples were maintained at lower levels due to "grazing" by predacious protozoa.     

Enteropathogenic, enterotoxigenic and enteroinvasive Escherichia coli isolated from acute gastroenteritis patients in Lagos, Nigeria

Enteropathogenic, enterotoxigenic and enteroinvasive Escherichia coli were isolated from 52 (4.8%) of 1,082 patients with acute gastroenteritis reporting at the Lagos University Teaching Hospital, Lagos, Nigeria between October 1979 and March, 1981. Of the 52 strains of E. coli isolated, 35 (67.3%) were enteropathogenic, 12 (23.1%) were enterotoxigenic and five (9.6%) were enteroinvasive. E. coli 0111 (25.7%) was the most predominant among the serotypes of the "classical" enteropathogenic strains found in this study. Diarrhoea associated with enteropathogenic E. coli occurred only in children aged less than five years, whereas enterotoxigenic and enteroinvasive E. coli were found primarily in adults. The study has highlighted for the first time the important role that enterotoxigenic and enteroinvasive E. coli strains could play in acute diarrhoeal diseases in Lagos, Nigeria.     

Prevalence of the "high-pathogenicity island" of Yersinia species among Escherichia coli strains that are pathogenic to humans

The fyuA-irp gene cluster contributes to the virulence of highly pathogenic Yersinia (Yersinia pestis, Yersinia pseudotuberculosis, and Yersinia enterocolitica 1B). The cluster encodes an iron uptake system mediated by the siderophore yersiniabactin and reveals features of a pathogenicity island. Two evolutionary lineages of this "high pathogenicity island" (HPI) can be distinguished on the basis of DNA sequence comparison: a Y. pestis group and a Y. enterocolitica group. In this study we demonstrate that the HPI of the Y. pestis evolutionary group is disseminated among species of the family Enterobacteriaceae which are pathogenic to humans. It prevails in enteroaggregative Escherichia coli and in E. coli blood culture isolates (93 and 80%, respectively), but is rarely found in enteropathogenic E. coli, enteroinvasive E. coli, and enterotoxigenic E. coli isolates. In contrast, the HPI was absent from enterohemorrhagic E. coli, Shigella, and Salmonella enterica strains investigated. Polypeptides encoded by the fyuA, irp1, and irp2 genes located on the HPI could be detected in E. coli strains pathogenic to humans. However, these E. coli strains showed a reduced sensitivity to the bacteriocin pesticin, whose uptake is mediated by the FyuA receptor. Escherichia strains do not possess the hms gene locus thought to be a part of the HPI of Y. pestis. Deletions of the juA-irp gene cluster affecting solely the fyuA part of the HPI were identified in 3% of the E. coli strains tested. These results suggest horizontal transfer of the HPI between Y. pestis and some pathogenic E. coli strains.     

Escherichia coli Removal Efficacy of a Marshland Upwelling System

The Marshland Upwelling System (MUS), a decentralized wastewater treatment strategy for coastal dwellings, was examined to assess its ability to remove Escherichia coli from raw sewage as a step towards total treatment. Wastewater was intermittently injected down a 4.6-m injection well into the surrounding salt marsh at 0.9, 1.9, and 3.8 lpm over the 13-month evaluation period. Optimal E. coli removal and hydraulic performance was achieved at the 1.9-lpm flow rate with influent concentrations of 260,000±370,000 E. coli/100 mL reduced to a mean effluent count of 0.4±10.6 E. coli/100 mL. Escherichia coli concentrations declined exponentially with only 0.9-m travel distance needed to reduce influent concentrations by 1 order of magnitude. Predicted surface concentrations were less than 1 E. coli/100 mL. The probability of effluent counts exceeding the U.S. Environmental Protection Agency standard of 126 E. coli/100 mL for recreational waters was 5.5×10?12%. Increasing flows to 3.8 lpm initiated localized hydraulic dysfunction as indicated by elevated injection pressures and transient increases in bacterial counts. Based on these findings, the MUS can provide an effluent of acceptable bacterial quality under specified operating parameters and the site-specific hydrogeological conditions analyzed.     

The occurrence of ambient temperature-regulated adhesins, curli, and the temperature-sensitive hemagglutinin tsh among avian Escherichia coli

Escherichia coli establishes a secondary respiratory tract infection in birds following inhalation of contaminated dust and litter particles. Escherichia coli express adhesins under conditions reflective of the ambient temperatures present in poultry houses. These microbial adhesins allow E. coli to attach to cell types that it initially encounters in the respiratory tract. Ambient temperature-regulated adhesins represent a new class of bacterial hemagglutinins that include pili and the thin, aggregative, flexible filaments known as "curli." This study examines the occurrence of the ambient temperature-regulated adhesins, curli (crl, csgA), and an avian-specific, temperature-sensitive hemagglutinin, tsh, among avian and mammalian E. coli isolates. The avian hemagglutinin gene tsh was present in approximately 46% of clinical avian E. coli isolates. This gene was not detected among commensal E. coli isolated from healthy broiler chickens. Unlike tsh, curli genes were ubiquitous among E. coli. However, curli were observed in only half of the avian E. coli examined by electron microscopy. Curli were not present among several nonavian E. coli positive for crl and csgA. Approximately 25% of avian E. coli isolates agglutinated chicken erythrocytes when bacteria were grown at room temperature. Hemagglutination was not specific to E. coli isolated from poultry. Presence of either tsh or curli genes was not indicative of an isolate's ability to agglutinate chicken red blood cells. No discernible structures were observed mediating attachment of the bacteria to chicken red blood cells. An additional avian-specific hemagglutinin appears to be present among avian E. coli.     

Histidine patch thioredoxins. Mutant forms of thioredoxin with metal chelating affinity that provide for convenient purifications of thioredoxin fusion proteins

A cluster of surface amino acid residues on Escherichia coli thioredoxin were systematically mutated in order to provide the molecule with an ability to chelate metal ions. The combined effect of two histidine mutants, E30H and Q62H, gave thioredoxin the capacity to bind to nickel ions immobilized on iminodiacetic acid- and nitrilotriacetic acid-Sepharose resins. Even though these two histidines were more than 30 residues apart in thioredoxin's primary sequence, they were found to satisfy the geometric constraints for metal ion coordination as a result of the thioredoxin tertiary fold. A third histidine mutation, S1H, provided additional metal ion chelation affinity, but the native histidine at position 6 of thioredoxin was found not to participate in binding. All of the histidine mutants exhibited decreased thermal stability as compared with wild-type thioredoxin; however, the introduction of an additional mutation, D26A, increased their melting temperatures beyond that of wild-type thioredoxin. The metal chelating abilities of these histidine mutants of thioredoxin were successfully utilized for convenient purifications of human interleukin-8 and -11 expressed in E. coli as soluble thioredoxin fusion proteins.     

Development of a biosensor for E. coli based on a flexural plate wave (FPW) transducer

To fulfill the need for rapid, cost-effective and sensitive methods for the detection of bacteria in medical diagnostics, food technology, biotechnology and environmental monitoring, a development of a bacterial sensor was initiated. Our approach of a biosensor for E. coli is based on an acousto-gravimetric flexural plate wave (FPW) transducer (gravimetric detection limit of less than 6 ng in a 32 microns thick sensitive layer in aqueous media), and an immunoaffinity layer on the transducer membrane for the molecular recognition of the target bacteria. An intermediate layer of covalently coupled poly (acrylic acid) yielded a major reduction of the non-specific binding to the metal surface. Such a biosensor, using antibodies against E. coli K12 and E. coli 15 outer surface antigens, yielded a detection range of 3.0 x 10(5) to 6.2 x 10(7) cells/ml for samples with the corresponding bacteria. To increase the sensitivity further, an amplification method using microspheres coupled with antibodies against E. coli was tested as a sandwich assay, and up to now a five-fold amplification of the signal has been achieved.     

Epidemiological study of latent and recent infection by Toxoplasma gondii in pregnant women from a regional population in the U.K

The last two amino acids in the nascent peptide influence translation termination in E. coli (Mottagui-Tabar et al., 1994; Bj?rnsson et al., 1996). We have compared the effects on termination in Escherichia coli, Bacillus subtilis and Salmonella typhimurium obtained by varying the -1 and -2 codons upstream of the weak UGAA stop signal. The peptide effect from the penultimate amino acid on translation termination in B. subtilis is similar to that seen in E. coli (with 66.5% RF-2 amino acid sequence similarity), whereas the influence in S. typhimurium (with 95.3% similarity to E. coli) is weaker. The effect of changing the -1 codon (P-site) is weaker in S. typhimurium as compared to those in E. coli and B. subtilis. RF-2s from E. coli and S. typhimurium have a threonine or alanine at position 246, respectively. This amino acid exchange in RF-2 can explain the difference in efficiency and toxicity during overexpression when E. coli and S. typhimurium are compared (Uno et al., 1996). However, B. subtilis RF-2 also has an alanine at that position, yet the sensitivity to the nascent peptide is similar to that in E. coli. Thus, the amino acid difference at position 246 in the RF-2 sequences cannot explain why termination in E. coli and B. subtilis is similar in peptide sensitivity while being different from that in S. typhimurium. Sequence alignments of RF-2 from the three bacteria show other regions of the molecule that could be involved in the functional interactions with the C-terminal end of the nascent peptide.