产嗜铁素砷抗性微生物在砷污染环境中的作用

在砷污染环境中,许多微生物进化出了砷抗性,对地球环境中砷的命运起着决定性的作用。其次,由于自然条件下铁有效浓度低,微生物一般会表达嗜铁素,协助微生物吸收铁。嗜铁素除了与铁结合外,还可与多种金属离子形成稳定的复合物,促进环境中砷酸盐的溶解和亚砷酸盐的氧化。最后,产嗜铁素微生物有促进植物生长和促进或减弱植物吸收砷的可能性。因此,产嗜铁素砷抗性微生物可能具有在砷污染环境的修复中发挥作用的潜力。     

地下水微生物功能群及生物地球化学循环

地下水系统是地球关键带的重要组成部分,为微生物提供了特殊的栖息环境和复杂的生存条件,进而演化出复杂的生物地球化学过程.随着多技术、多学科的交叉融合及发展,近几十年地下水微生物功能群及生物地球化学循环研究取得了引人瞩目的 重要进展.本文从地下水中的微生物群功能分区、微生物介导的地球化学元素循环、污染与修复中的生物地球化学...     

砷耦合还原的微生物协同机制及其环境效应

砷(arsenic, As)是一种常见的有毒污染元素,微生物介导的砷形态转变是砷生物地球化学循环的重要组成部分。在砷的各类微生物代谢过程中,砷的耦合还原对环境影响较大,也是容易被忽视的过程。本文主要从砷的生物地球化学循环出发,介绍了甲烷氧化、厌氧铵氧化、铁(Fe)-硫(S)氧化与砷耦合还原的微生物协同机制,有机质、pH值以及氧化还原电位是影响砷耦合还原的主要因素。砷经耦合还原后,毒性和迁移性大大增加,可能会增加砷污染的风险。因此,进一步明确碳(C)、氮(N)、Fe、S等这些元素在砷耦合过程中的影响以及挖掘出更多的微生物耦合还原过程,在防治砷污染方面具有重要意义。     

大洋最小含氧带生物地球化学循环及微生物多样性研究进展

大洋的最小含氧带(oxygen minimum zones,OMZs)具有特殊的水动力和氧含量特征,该区域是氮流失的主要场所,也是各类生化反应发生的重要区域.OMZs的存在会对浮游生物的丰度、多样性、分布模式及呼吸方式产生较大影响.大洋OMZs中存在广泛的反硝化、厌氧氨氧化、甲烷厌氧氧化和隐性厌氧硫氧化作用等都是海洋物...     

深海微生物高压适应与生物地球化学循环

深海是典型的高压环境,嗜压微生物是深海生态系统中的重要类群.随着深海采样技术的发展及高压微生物特殊培养设备的开发,已从深海环境中分离到一系列嗜压微生物,包括一些常压环境不能生长的严格嗜压菌.对这些嗜压菌的研究,不仅对微生物适应极端高压环境的机制有一定了解,而且发现了一些特殊的代谢产物.研究微生物高压嗜压机理,还有助于探索地球生命的温度压力极限及生命起源和演化等科学问题.从深海嗜压微生物多样性、深海微生物高压环境适应机理及深海微生物在生物地球化学循环中的作用等方面对嗜压微生物的研究进展进行综述.     

植物在硅生物地球化学循环过程中的作用

硅是地球上重要的矿质元素,在许多生物地球化学过程中起着重要作用。传统认为硅的循环主要受岩石风化、矿物溶解和水体沉积的影响。实际上,植物在硅的生物地球化学循环中起着重要作用。植物体本身就是一个相当大的硅库,它们能以无定型硅(SiO2.nH2O)的形式积累硅,称作生物硅(BSi)、植硅石或蛋白石。陆地植物每年以BSi的形式固定约1.68×109～5.60×109t的硅,通过枯枝落叶返回到土壤中的BSi有92.5%被植物再吸收,7.5%进入土壤库。陆地植物从土壤BSi库吸收的硅量远超过从岩石风化释放吸收的硅量,植物-土壤内循环的有效性强烈地影响着陆地生态系统中的硅向河流和海洋的输送。在海洋中,硅藻通过吸收、溶解和沉积在很大程度上影响着海洋里的硅循环,硅藻每年固定的硅约为5.60×109～7.84×109t,同样,在向海底沉积的过程中,97%的BSi重新被硅藻吸收,每年只有1.43×108～2.55×108t(约3%)沉积到海底。可见,植物在陆地生态系统和水生生态系统硅的循环中均起着非常重要的作用,研究硅的全球生物地球化学循环时必须考虑到植物的作用。     

三极冰川冰尘微生物及其介导的碳氮生物地球化学循环研究进展

冰尘是散落在冰川表面由矿物质、有机质和微生物组成的聚合体,其主要来源包括远源输送来的细粉尘和气溶胶组分、局地源的粗冰碛物及来自周围生态系统的土壤和植物碎屑等。冰尘对太阳辐射具有较强的吸收作用,可降低冰面反照率、促进冰川融化。冰尘也是迄今为止生物多样性最高的冰川表面微生物栖息地,生活着细菌、真菌、藻类等。冰尘微生物是冰川表面地球化学循环的主要驱动者,微生物分解转化冰尘内有机质,降低冰川表面反照率影响冰川物质平衡。基于冰尘的重要性,本文综述了南极、北极、青藏高原第三极冰川冰尘的物理和化学特征及其影响因素,冰尘微生物群落组成及其介导的碳氮生物地球化学循环过程,并展望了冰尘微生物研究的前景。     

抗砷性微生物及其抗砷分子机制研究进展

砷(Arsenic, As)是一种剧毒类金属(Metalloid), 在自然环境中主要以三价亚砷酸盐[Arsenite, AsO2-, As(III)]和五价砷酸盐[Arsenate, AsO43-, As(V)]的无机形式广泛存在。许多微生物在含砷环境的长期适应过程中, 进化了多种不同的砷解毒抗性机制。目前研究发现主要存在4种类型的砷抗性机理, 包括: As(III)氧化, 细胞质As(V)还原, 呼吸性As(V)还原, As(III)甲基化, 这些机制赋予微生物砷抗性并在砷的转化和地球化学循环中起着极     

生物地球化学锰循环中的微生物胞外电子传递机制

微生物是生物地球化学元素循环的重要驱动者,在锰等变价金属元素的氧化还原过程中起着至关重要的作用。近年来,Mn(Ⅲ)的发现以及在一些环境中的广泛存在,丰富了人们对Mn(Ⅲ)以及自然界锰循环过程的认识。研究发现,锰的生物地球化学循环,尤其是锰还原过程,与微生物胞外电子传递紧密相关,且目前已知的5种胞外电子传递机制均与锰还原有关联。因此,本文综述了锰的生物地球化学循环及其意义,并从微生物胞外电子传递的机制、微生物介导锰氧化、微生物介导锰还原等3个方面来介绍参与锰循环的微生物多样性;以及微生物地球化学锰循环的环境意义。对微生物参与锰循环过程的研究不仅可以进一步丰富相关理论,同时也能推动生物除锰、污染物原位修复及生物冶金等应用领域的发展。     

Microfracture Surface Geochemistry and Adherent Microbial Population Metabolism in TCE-Contaminated Competent Bedrock

A TCE-contaminated competent bedrock site in Portsmouth, NH was used to determine if a relation existed between microfracture surface geochemistry and the ecology and metabolic activity of attached microbes relative to terminal electron accepting processes (TEAPs) and TCE biodegradation. The bedrock is a metasandstone and metashale of the Silurian Kittery Formation. Eleven microfractures (MF 01-11) were extracted from cores of competent rock from 2 boreholes (BBC5 and BBC6) at depths > 21.3 m below ground. The host rock had 3 nominal pore width sizes (131.1, 1.136, and 0.109 μ m), a porosity of 0.8%, and a permeability of < 1 μ d. Microfracture surface precipitates were polycrystalline with grain sizes ranging from 10 to 100 μ m. Petrography and XRD revealed that carbonates and quartz were the dominant microfracture surface precipitates. Mineral distribution was heterogeneous at the 10 μ m scale. Oxidized and reduced iron species were identified with XPS on the microfracture precipitate surfaces. Carbon functional groups characteristic of NOM were also identified. SIMS mass fragment fingerprints suggested that TCE, PCE and/or VC were possibly adsorbed to NOM on the microfracture surfaces. Packer waters were alkaline (131–190 mg/L as CaCO₃, pH 8.8 to 9.6), mildly reducing (Eh of ?208 to 160 mV, DO of 0.4 to 2.5 mg/L), with low NPDOC values (0.8–1.7 mg/L), and measurable Fe (II) (0.1 mg/L) and Fe (III) (0.02 to 0.3 mg/L). Sulfate was the dominant anion in the packer sample water (110–120 mg/L). No sulfide was detected. H ₂ was present in a number of the BBC wells at the site (2.2–7.3 nM). Amplification with specific primer sets of seven microfractures from BBC5 showed the presence of bacteria, Archaea, anaerobic dehalorespirers (Dehalococcoides sp.), sulfate reducing bacteria, and iron reducing bacteria (Geobacteraceae). Redox zonation may exist relative to spatial distance from within the microfracture network to the open fracture system. The microfracture surface precipitates, frequently spatially complex and comprised of a variety of C-, Fe- and S-containing minerals, may be another region for redox zonation. Fe was the dominant microfracture surface element and active Fe cycling is suspected. However, the primer data suggest that the microfracture network may have been more reducing than the open fracture system. In this case, the microfracture network may constitute a zone where more reductive metabolic processes occur, making this system similar to biogeochemical redox zones found in other environments.     

Oxidation of As(III) by the Bacterial Community of a Marine Sediment Monitored by Microcalorimetry

Oxidation of arsenic(III) by the bacterial community of a contaminated sediment (from the Estaque marina, Marseille, France) was studied using microcalorimetry. A low, but reproducible, heat output was detectable during microbial As(III) oxidation. The heat produced was of the same order of magnitude as the heat value calculated from the standard molar enthalpy change for the As(III) oxidation by oxygen. Parameters associated with the biogeochemical cycles of arsenic, iron and carbon were studied in parallel. Amendment with arsenite delayed CO₂ production and increased the rate of Fe(II) oxidation in the sediment. These results suggest a correlation between arsenic and iron biogeochemical cycles and mineralization of organic matter.

Supplemental materials are available for this article. Go to the publisher's online edition of Geomicrobiology Journal to view the supplemental file.     

Arsenic in the Evolution of Earth and Extraterrestrial Ecosystems

If you were asked to speculate about the form extra-terrestrial life on Mars might take, which geomicrobial phenomenon might you select as a model system, assuming that life on Mars would be ‘primitive’? Give your reasons.     

Enthalpies and Entropies of Cd and Zn Adsorption onto Bacillus licheniformis and Enthalpies and Entropies of Zn Adsorption onto Bacillus subtilis from Isothermal Titration Calorimetry and Surface Complexation Modeling

Determining the thermodynamic driving force of metal-bacteria surface complexation is important for understanding why, from a thermodynamic perspective, these spontaneous reactions occur. We therefore determined the Gibbs energies, enthalpies, and entropies of Cd and Zn complexation onto Bacillus licheniformis and of Zn complexation onto Bacillus subtilis using surface complexation modeling and isothermal titration calorimetry. Our results indicated that Cd and Zn complexation onto Bacillus licheniformis is entropically driven at low pH and enthalpically driven at circumneutral pH. Zn complexation onto Bacillus subtilis is entropically driven, which suggests that Bacillus licheniformis has different donor ligands dominating reactivity around circumneutral pH.     

Effects of Metabolism and Physiology on the Production of Okenone and Bacteriochlorophyll a in Purple Sulfur Bacteria

Purple sulfur bacteria (PSB) are important photoautotrophs inhabiting chemoclines in euxinic and meromictic lakes. These organisms are the only producers of the carotenoid, okenone, a compound that has been targeted as a biomarker for photic zone euxinia, particularly in ancient sedimentary environments. Although the natural occurrence and geochemistry of this compound has been studied previously, this is the first systematic and comprehensive report on the microbial physiology of okenone production in pure cultures. Four strains/species: Marichromatium purpuratum DSMZ 1591, Marichromatium purpuratum DSMZ 1711, Thiocapsa marina DSMZ 5653, and FGL21 (isolated from Fayetteville Green Lake, New York) were chosen because they produce okenone and Bacteriochlorophyll a (Bchl a). We developed a new, in vivo technique for the quantification of okenone allowing for more rapid and accurate quantification. The ratio of okenone to Bchl a differs among species and strains of PSB, varying from 0.463 ± 0.002 to 0.864 ± 0.002. Photoheterotrophically grown PSB have statistically significant, lowered okenone:Bchl a ratios, decreasing from 0.784 ± 0.009 under autotrophic metabolism to 0.681 ± 0.002, which we interpret to indicate a decreased requirement for okenone when PSB are provided with a complex (> C1) carbon source. The variation in okenone production raises the question on whether okenone expression is constitutive or inducible. The broader implication is that concentrations of okenone in sediments are dependent on metabolism and species composition, and not solely on PSB cell density.     

Limestone Corrosion by Neutrophilic Sulfur-Oxidizing Bacteria: A Coupled Microbe-Mineral System

Subsurface karst aquifers receiving sulfidic water can host complex chemolithotrophic microbial communities that are capable of dissolving limestone, forming new karstic habitat. Neutrophilic sulfur-oxidizing bacteria use reduced sulfur compounds as energy rich substrate, potentially producing sulfuric acid as a geochemically reactive byproduct. The physicochemical relationship between a biofilm forming on a limestone surface and the extent of microbial influence on dissolution rate, however, are unknown. We investigated the rate of Madison limestone dissolution by sulfur-oxidizers both in the field at Lower Kane Cave, WY (LKC), and in the laboratory using continuous flow culture reactors and microbial mat collected from LKC. In the field, a microbial consortium rapidly colonized limestone chips forming a thick biofilm, with deep etching of mineral surfaces underneath. In the laboratory we found that a microbial biofilm oxidizing thiosulfate on the limestone surface accelerated dissolution rate up to 7 times faster than the abiotic baseline rate. In contrast, experiments done with H₂S or a mixture of H₂S and thiosulfate had no effect on dissolution rate. We hypothesize that the laboratory mat community dominated by Thiothrix sp. oxidizes thiosulfate to sulfate and H⁺, while H₂S is partially oxidized to S°. When all sulfur substrate is withheld, the community oxidizes stored intracellular sulfur, briefly accelerating limestone dissolution even in the absence of external supplied substrate. Accelerated corrosion occurs only in the reactive micro-environment under the biofilm, disconnected from the bulk reactor solution. When experiments are repeated where the microbial population is separated from the limestone by a dialysis membrane barrier, measured pH drop is greater, but there is only slight enhancement of rate. This work confirms our working hypothesis that neutrophilic sulfur-oxidizers colonize and rapidly dissolve limestone surfaces, possibly to buffer the production of excess acidity.