Porewater oxidation,dissolved phosphate and the iron curtain

The process of dissolved phosphate removal from aqueous solution, which occurs during oxidation of soluble ferrous compounds to insoluble ferric forms, was examined in soils of two tidal freshwater marshes. Sites of amorphous iron deposition and sorption or co-precipitation of phosphate were found to be in surface soils and along creekbanks, where both ion diffusion and porewater advection move dissolved iron and phosphate from reduced to oxidized regions. Profiles of extractable iron and total phosphorus from creekbank and interior soils were consistent with hypothesized differences between a high and a low marsh. Porewater concentrations of dissolved phosphate were higher in creekbank soils of the high marsh, compared with water actually discharging from the creekbank during tidal exposure. We propose that an iron curtain of ferric hydroxides functions as a barrier to diffusive and advective movement of dissolved phosphate along surfaces of tidal freshwater marshes, and has important implications for the distribution and availability of phosphorus in other types of wetlands and aqueous systems.     

Assessment of Heavy Metal Mobility in Dredged Sediments: Porewater Analysis,Single and Sequential Extractions

Dredged sediments from the Leie catchment (Belgium) that were deposited on land between 70 and 10 years ago were characterized according to their physico-chemical properties, total metal concentrations and porewater composition. Actual and potential heavy metal availability was assessed by means of single extractions with 0.01 M CaCl ₂ , 0.05 M EDTA and 0.43 M acetic acid. A modified version of the BCR (Community Bureau of Reference) extraction procedure, adapted to the elevated acid neutralizing capacity of the sediments, was applied. Information on element mobility was assessed and the used methodologies were critically evaluated.

The favorable physico-chemical characteristics of dredged sediments from the catchment of the Leie River (N-Belgium) indicated a rather low actual heavy metal mobility. Based on CaCl ₂ and EDTA extractions, the distribution of Cd, Zn and Ni between the solution and sorbed phase could be described as a function of pH and organic carbon content. Cd and Zn were found to be the elements with the highest potential availability, while Cu and Ni displayed a medium availability. It is stressed that different types of extractions deal with heavy metal mobility in a different way and that the measurement of “key-factors” such as the pH of the extracts can be helpful for the interpretation of the results.     

An in situ method for cultivating microorganisms using a double encapsulation technique

The lack of cultured microorganisms represents a bottleneck for advancement in microbiology. The development of novel culturing techniques is, therefore, a crucial step in our understanding of microbial diversity in general, and the role of such diversity in the environment, in particular. This study presents an innovative method for cultivating microorganisms by encapsulating them within agar spheres, which are then encased in a polysulfonic polymeric membrane and incubated in a simulated or natural environment. This method stimulates growth of the entrapped microorganisms by allowing them access to essential nutrients and cues from the environment. It allows for the discovery of microorganisms from dilutions that are 10–100-fold greater than possible with conventional plating techniques. Analysis of microorganisms grown in such spheres incubated in and on a number of different substrates yielded numerous novel ribotypes. For example, spheres incubated on the mucus surface of a Fungiid coral yielded numerous ribotypes, with only 50% sharing similarity (85–96%) to previously identified microorganisms. This suggests that many of the species represent novel ribotypes. Hence, the technique reported here advances our ability to retrieve and successfully culture microorganisms and provides an innovative tool to access unknown microbial diversity.     

产油微生物利用餐厨垃圾生产油脂的研究进展

餐厨垃圾中含有丰富的营养物质,经生物转化过程可以合成对人类有用的化学品.某些产油微生物可以处理餐厨垃圾生产油脂,同时合成高附加值代谢产物如多不饱和脂肪酸、角鲨烯和类胡萝卜素等.这不仅能够降低生产成本,而且提高了产物的经济价值,具有极大的工业化应用潜力.文中主要概括了目前餐厨垃圾的处理研究现状,综述了产油微生物发酵餐厨垃...     

Biological cyanide destruction mediated by microorganisms

Many microorganisms have an inherent capacity to degrade the toxic organic compounds that enter the environment as a result of pollution and natural activities. Significant degradation of these compounds may take many years and it is frequently necessary to consider methods that can accelerate this process. There have been several demonstrations of enhanced biological degradation of toxic wastes, both in the laboratory and under field conditions. The prospects for enhanced biological cyanide degradation are reviewed. Compared with bench-scale processes, there are very few reports of field-scale processes for cyanide bioremediation. The implementation of such field-scale degradation requires inputs from biology, hydrology, geology, chemistry and civil engineering. A conceptual framework is emerging that can be adapted to develop new processes for bioremediation of toxic organic wastes. In terms of cyanide biodegradation, this framework incorporates identification of microbes, determination of the optimal conditions for degradation, establishment of the metabolic pathways involved in cyanide degradation, identification and localization of the genes involved, identification of suitable microbial strains for practical application and development of practical engineering processes. The present review addresses the progress that has been made in each of these aspects of cyanide biodegradation. It also examines the existing field applications of biological cyanide degradation and makes recommendations for future research.Dr S.K. Dubey is and Dr D.S. Holmes was with the Department of Biology, Clarkson University, Potsdam, NY 13699, USA. Dr D.S. Holmes is now affiliated with Centro de Estudios Cientifigos de Santiago, Av. Presedente Errazuriz 3132, Casilla 16443, Santiago 9, Chile.     

微生物改善烟叶品质研究进展

从微生物缩短烟叶发酵时间、降低烟叶有害成分、增加烟叶香气等方面概述了微生物在改善烟叶品质方面的研究进展,并对其在烟叶上的应用前景作了分析。     

Degradation of 4,5-dichloroguaiacol by soil microorganisms

No microorganisms could be isolated from chemostats or from a soil column fed with 4,5-dichloroguaiacol as the only carbon source. If guaiacol was added to chemostats with 4,5-dichloroguaiacol, either soil microbial consortia or guaiacol-degrading bacteria could dechlorinate the 4,5-dichloroguaiacol provided it was <0.2mm. A microbial consortium from farm soil removed 4,5-dichloroguaiacol under aerobic or anoxic conditions, with or without chlorolignin. Dichlorocatechol was the only 4,5-dichloroguaiacol-derived metabolite detected. In aerobic incubations, 4,5-dichlorocatechol was further degraded whereas under anoxic conditions it accumulated.     

基因工程菌发酵生产L-乳酸研究进展

乳酸是重要的工业平台化学品。随着聚乳酸产业的兴起,对高质量L-乳酸的需求量也不断增加。为了进一步降低L-乳酸发酵成本,提高菌株的工业适应性,各种现代生物技术已经应用到L-乳酸发酵菌种的改造上来。文中简要综述了近年来使用乳酸菌、酵母、大肠杆菌及米根霉等基因工程菌株发酵生产L-乳酸的技术进展。     

Spectroscopic characterization of microorganisms by Fourier transform infrared microspectroscopy

Spectroscopic fingerprints of bacteria were investigated by Fourier transform infrared (FTIR) microspectroscopy for the elucidation of chemical composition and structural information during growth. Good differentiation of six microorganisms was achieved down to the strain level. The inherent compositional and structural differences of cell envelopes and cytoplasm were investigated and utilized to obtain more detailed analysis of the spectroscopic features. Bands or regions of key functional groups were also identified in the original spectra. Microspectroscopic monitoring of bacterial growth demonstrated that FTIR spectroscopy cannot only provide molecular fingerprints of the cell envelope, but also compositional and metabolic information of the cytoplasm under different physiological conditions. This approach could be an effective alternative to traditional nutritional and biochemical methods to monitor and assess the effects of inhibitors and other environmental factors on microbial cell growth.     

生物冶金中耐盐浸矿微生物的研究进展

耐盐浸矿微生物是指在发挥矿物浸出功能时对所处的含盐环境具有一定耐受能力的一类浸矿微生物。耐盐浸矿微生物因其可以适应不同浓度的氯化钠等盐,因而在淡水资源缺乏地区的生物冶金中具有广泛的应用价值。本文从耐盐浸矿微生物的种类、耐盐机制及其在矿物生物浸出中的应用现状进行了系统性综述,为耐盐浸矿微生物的研究和应用提供参考。     

Biodegradation of hexachlorocyclohexane (HCH) by microorganisms

The organochlorine pesticide Lindane is the -isomer of hexachlorocyclohexane (HCH). Technical grade Lindane contains a mixture of HCH isomers which include not only -HCH, but also large amounts of predominantly -, - and -HCH. The physical properties and persistence of each isomer differ because of the different chlorine atom orientations on each molecule (axial or equatorial). However, all four isomers are considered toxic and recalcitrant worldwide pollutants. Biodegradation of HCH has been studied in soil, slurry and culture media but very little information exists on in situ bioremediation of the different isomers including Lindane itself, at full scale. Several soil microorganisms capable of degrading, and utilizing HCH as a carbon source, have been reported. In selected bacterial strains, the genes encoding the enzymes involved in the initial degradation of Lindane have been cloned, sequenced, expressed and the gene products characterized. HCH is biodegradable under both oxic and anoxic conditions, although mineralization is generally observed only in oxic systems. As is found for most organic compounds, HCH degradation in soil occurs at moderate temperatures and at near neutral pH. HCH biodegradation in soil has been reported at both low and high (saturated) moisture contents. Soil texture and organic matter appear to influence degradation presumably by sorption mechanisms and impact on moisture retention, bacterial growth and pH. Most studies report on the biodegradation of relatively low ( 500 mg/kg) concentrations of HCH in soil. Information on the effects of inorganic nutrients, organic carbon sources or other soil amendments is scattered and inconclusive. More in-depth assessments of amendment effects and evaluation of bioremediation protocols, on a large scale, using soil with high HCH concentrations, are needed.     

Template mixing: a method of enhancing detection and interpretation of codominant RAPD markers

Ten codominant RAPD markers, ranging in size from about 300 to about 1350 bp, were identified in mapping populations of chickpea (Cicer arietinum L.) and diploid strawberry (Fragaria vesca L.). A distinguishing feature of all ten markers, and perhaps of codominant RAPD markers in general, was the presence in heterozygous individuals of a non-parental, heteroduplex band migrating more slowly than either of the respective parental bands. This non-parental band could also be generated by mixing parental DNAs before PCR (template mixing). As a means of identifying primers likely to detect codominant RAPD markers, parental and mixed-template (parent-parent) PCR-product gel lanes were compared for 20 previously untested RAPD primers (10-base oligomers). Four primers that produced a total of five non-parental, heteroduplex bands in mixed-template reactions were selected, and then used to detect a total of five segregating, codominant markers and nine dominant markers in the respective F₂ mapping population, a codominant marker frequency of 35.7%. When closely migrating fast and slow bands of codominant RAPDs were difficult to differentiate, parent-progeny template mixing was used to deliberately generate heteroduplex bands in fast- or slow-band F₂ homozygotes, respectively, allowing confirmation of marker phenotype.     

红树林土壤微生物的研究：过去、现在、未来

红树林土壤生境的独特性决定了其中微生物的多样性及其资源的珍稀性,对于红树林土壤微生物的研究正在成为热点。然而由于传统研究方法等因素的限制,至今人们对红树林土壤微生物的系统了解仍较为有限。近年来,基于16S rRNA,18S rRNA基因的各种分子微生物学技术的迅速发展,红树林土壤微生物的研究亦面临着崭新的局面。文中主要从红树林土壤微生物物种的多样性、生理生化类型的多样性及其在治理污染环境、生物修复作用中的可能性、有效性等方面阐述了红树林土壤微生物的研究进展,并以更合理、有效地开发利用红树林土壤微生物资源为目标,展望了21世纪,以新理念、新技术、新方法进行红树林土壤微生物研究及资源开发的巨大前景。     

Influence of phosphorus on the colonization of barley rhizosphere by microorganisms

The mineral phosphorus supply produced two outbreaks in the bacterial population of the barley rhizosphere and rhizoplane but inhibited the growth of fungal mycelium. The inhibition of mycelial growth might be due to the exudation of specific inhibitors by barley roots, since the most pronounced inhibition was observed at high doses of supplementary phosphorus.     

Skeletal modification by microorganisms and their environments

Abstract

Microstructural post mortem changes to skeletal tissues by microorganisms are driven by several factors including the death history of an animal, its decomposition trajectory, and the depositing environment itself. The study we describe here brings together material from recent and fossil contexts that are depositionally distinct from a terrestrial-marine transitionary shoreline environment. We compare these changes with those of marine environments previously identified in the Mary Rose material, and those of continental waters (lakes) previously identified in the Cerro de la Garita (Concud) site, and we document this against bacterially related changes observed from terrestrial contexts. A new microstructural change identified in material from terrestrial sites is also described relating to rootlet damage. By considering microstructural change in skeletal tissues, it is maybe possible to ascribe environmental context, or, to better understand the complexity of material presented by transitionary environments.     

Improved method for direct screening of true lipase-producing microorganisms with particular emphasis on alkaline conditions

A rapid and effective method for direct detection, selection and testing of microorganisms able to produce both cell-bound and extracellular true lipases is described. The method is based on formation of clearance zones on turbid solid media with emulsified olive oil around or under the colonies, cell fractions or culture supernatant of lipase-producing organisms. The method was successfully applied for the screening and isolation of microorganisms producing alkaline lipases. The article is published in the original.     

Rapid method for the detection of genetically engineered microorganisms by polymerase chain reaction from soil and sediments

A rapid and sensitive method for the detection of genetically engineered microorganisms in soil and sediments has been devised by in vitro amplification of the target DNAs by a polymerase chain reaction. A cloned catechol 2,3-dioxygenase gene located on the recombinant plasmid pOH101 was transferred to Pseudomonas putida MMB2442 by triparental crossing and used as a target organism. For the polymerase chain reaction from soil and sediment samples, the template DNA was released from a 100-mg soil sample. Bacterial seeded soil samples were washed with Tris-EDTA buffer (pH 8.0) and treated with a detergent lysis solution at 100°C. After addition of 1% polyvinylpolypyrrolidine solution, the samples were boiled for 5 min. Supernatant containing nucleic acid was purified with a PCR purification kit. The purified DNA was subjected to polymerase chain reaction, using two specific primers designed for the amplification of catechol 2,3-dioxygenase gene sequences. The detection limit was 10² cells per gram of soil. This method is rapid and obviates the need for lengthy DNA purification from soil samples. Received 28 February 1997/ Accepted in revised form 23 November 1997     

A case study of airborne culturable microorganisms in a poultry slaughterhouse in Styria, Austria

According to Council Directive 90/679/EEC on the protection of workers from risks related to exposure to biological agents at work, nature, degree and duration of workers’ exposure to microorganisms must be determined. This directive has already been implemented in waste and wastewater management. The present case study investigates concentration and composition of microorganisms in a poultry slaughterhouse in the State of Styria, Austria. From June to November 2002, measurements were conducted at the sampling sites ‘moving rail’ and ‘gall bladder separation’ using the Andersen six stage viable cascade impactor and the SKC BioSampler. The results of this study were compared with other previous studies which were carried out using the same device (ACFM) and the same measurement methods. At the processing area of the ‘moving rail’, the median concentration of airborne mesophilic bacteria was 1.7×10⁶ CFU/m³ which is 8000 times higher than the background concentration of residential areas (approx. 210 CFU/m³). The airborne microorganisms concentration was 1.7×10⁴ CFU/m³ at composting plants which is 100 times lower than at a workplace of a poultry slaughterhouse. The study shows that poultry slaughterhouse employees are exposed to high concentrations of airborne microorganisms throughout the entire work time without using a respiratory protective device. For the protection of employees against airborne biological agents, relevant measures should be introduced to this field of work.     

微塑料与土壤环境中微生物互作研究进展

作为环境中广泛存在的污染物,微塑料(microplastics)的相关研究备受关注。基于已有研究,本文综合分析了微塑料与土壤微生物(soil microorganisms)的互作关系,微塑料会通过直接或间接的方式影响微生物群落结构与多样性,影响的程度取决于微塑料的类型、剂量和形状。土壤微生物会通过形成表面生物膜和群落选择效应来适应微塑料这一外来物所引起的变化。本文还特别关注了微塑料的生物降解机理,同时探究了影响这一过程的因素,微生物首先会定殖在微塑料表面,分泌多种胞外酶在特定位点发挥作用,将聚合物转化成低聚物或单体,解聚的小分子进入胞内进一步分解代谢,而影响这一降解过程的因素除了分子量、密度、结晶度等微塑料自身理化性质,还包括一些生物因素和非生物因素对相关微生物生长代谢和酶活性的作用。未来研究应注重与实际环境的联系,在深入探究微塑料生物降解研究的同时,开发解决微塑料污染问题的新技术。