我国藻菌生物成因的金矿研究

生物成矿作用分为生物直接成矿作用和生物间接成矿作用,生物直接成矿作用的标志结构为生物有机胶体结构。生物间接成矿作用的标志结构为“矿交代生物”结构,我国陕西二台子－半仓沟金矿,四川东北寨金矿、川甘拉尔玛金矿和云南金厂金矿等均为典型为实例,矿石中普遍含有多种金属矿物生物结构,还含多种生物有机组分。成矿物质具有多源性特征,硫同位素具混合型特征,矿床成型机制可与“人工碳吸附系统”聚金机制相类比,含金层位可     

Biomineralization of Uranium: A Simulated Experiment and Its Significance

A simulated experimental reduction of U^v1 and the synthesis of uraninite by a sulfate-reducing bacteria,Desulfovibrio desulfuricans DSM 642, are first reported. The simulated physicochemical experimental conditions were:35℃, pH=7.0-7.4, corresponding to the environments of formation of the sandstone-hosted interlayer oxidation-zone type uranium deposits in Xinjiang, NW China. Uraninite was formed on the surface of the host bacteria after a one-week‘s incubation. Therefore, sulfate-reducing bacteria, which existed extensively in Jurassic sandstone-producing environments,might have participated in the biomineralization of this uranium deposit. There is an important difference in the orderdisorder of the crystalline structure between the uraninite produced by Desulfovibrio desulfuricans and naturally occurring uraninite. Long time and slow precipitation and growth of uraninite in the geological environment might have resulted in larger uraninite crystals, with uraninite nanocrystals arranged in order, whereas the experimentally produced uraninite is composed of unordered uraninite nanocrystals which, in contrast, result from the short time span of formation and rapid precipitation and growth of uraninite. The discovery has important implications for understanding genetic significance in mineralogy, and also indicates that in-situ bioremediation of U-contaminated environments and use of biotechnology in the treatment of radioactive liquid waste is being contemplated.     

深海嗜热异化铁还原菌Caloranaerobacter ferrireducens DY22619T对不同铁氧化物的铁还原特性

异化铁还原微生物在铁元素的地球化学循环中具有重要意义。深海热液活动是大洋铁元素的重要来源,目前深海热液环境中铁代谢相关微生物研究很少。本文对一株分离自深海热液区的嗜热异化铁还原菌新种Caloranaerobacter ferrireducens DY22619T的铁还原特性进行分析,比较了该菌对无定形羟基氧化铁、无定形铁氧化物和针铁矿3种不同铁氧化物的铁还原速率;并利用透射电镜对矿化产物进行矿物形貌、组成元素和晶型的分析。研究发现该菌生长在指数期至稳定期时,铁还原速率最快,其中对无定形羟基氧化铁和无定形铁氧化物的还原速率较高,达2.82 μmol/h和2.15 μmol/h;透射电镜结果表明,该菌可将3种不同胞外铁氧化物均还原矿化形成颗粒状磁铁矿,由针铁矿矿化形成的磁铁矿少但粒径最大,而由无定形铁氧化物形成的磁铁矿晶面不同于另外两种铁氧化物。结果表明,该菌有很强的铁还原和矿化能力,能厌氧呼吸还原三价铁氧化物,但是铁氧化物的性质对该菌胞外铁还原能力和矿化形成的磁铁矿的性质有重要影响。本研究为认识深海热液环境中异化铁还原菌在铁元素的地球化学循环和生物成矿过程提供了参考。     

大洋铁锰结核的微生物成矿过程及其研究进展

深海铁锰结核作为世界上潜在的巨大金属宝库已成为当今开发海底矿藏的热点,因而深入了解铁锰结核成矿过程成为其开发利用的先决条件。研究发现多金属铁锰结核中的铁锰矿物不仅仅是由单纯的物理作用形成的,同时也包含了海洋生物驱动的生物矿化的过程。本文介绍了运用分子生物学、矿物学和地球化学等多学科的研究方法对大洋中铁锰的生物成矿过程和成矿特征的研究。深海铁锰结核的生长速率缓慢且其生长演化伴随着微生物群落的活动,因此结核的生长过程同时也记录着不同时期微生物群落结构的变化并生成了大量的微生物化石。在铁和锰的生物矿化过程中,细菌可以通过酶促反应氧化Fe（Ⅱ）和Mn（Ⅱ）,同时可能伴随生物能量的生成,此外微生物还可以通过非酶促反应的方式促进Fe和Mn的富集沉淀。这些研究表明生物矿化作用在大洋铁锰结核成矿过程中有巨大贡献,对大洋铁锰结核的生物成因过程提供更加全面准确的理解,从而为今后进一步充实大洋铁锰结核的生物矿化理论及其开发利用提供依据。     

Microbial–silica interactions in Icelandic hot spring sinter: possible analogues for some Precambrian siliceous stromatolites

Silicified deposits, such as sinters, occur in several modern geothermal environments, but the mechanisms of silicification (and crucially the role of microorganisms in their construction) are still largely unresolved. Detailed examination of siliceous sinter, in particular sections of microstromatolites growing at the Krisuvik hot spring, Iceland, reveals that biomineralization contributes a major component to the overall structure, with approximately half the sinter thickness attributed to silicified microorganisms. Almost all microorganisms observed under the scanning electron microscope (SEM) are mineralized, with epicellular silica ranging in thickness from < 5 μm coatings on individual cells, to regions where entire colonies are cemented together in an amorphous silica matrix tens of micrometres thick. Within the overall profile, there appears to be two very distinct types of laminae that alternate repeatedly throughout the microstromatolite: ‘microbial’ layers are predominantly consisting of filamentous, intact, vertically aligned, biomineralized cyanobacteria, identified as Calothrix and Fischerella sp.; and weakly laminated silica layers which appear to be devoid of any microbial component. The microbial layers commonly have a sharply defined base, overlying the weakly laminated silica, and a gradational upper surface merging into the weakly laminated silica. These cyclic laminations are probably explained by variations in microbial activity. Active growth during spring/summer allows the microorganisms to keep pace with silicification, with the cell surfaces facilitating silicification, while during their natural slow growth phase in the dark autumn/winter months silicification exceeds the bacteria’s ability to compensate (i.e. grow upwards). At this stage, the microbial colony is probably not essential to microstromatolite formation, with silicification presumably occurring abiogenically. When conditions once again become favourable for growth, recolonization of the solid silica surface by free‐living bacteria occurs: cell motility is not responsible for the laminations. We have also observed that microbial populations within the microstromatolite, some several mm in depth, appear viable, i.e. they still have their pigmentation, the trichomes are not collapsed, cell walls are unbroken, cytoplasm is still present and they proved culturable. This suggests that the bulk of silicification occurred rapidly, probably while the cells were still alive. Surprisingly, however, measurements of light transmittance through sections of the microstromatolite revealed that photosynthetically active light (PAL) only transmitted through the uppermost 2 mm. Therefore the ‘deeper’ microbial populations must have either: (i) altered their metabolic pathways; (ii) become metabolically inactive; or (iii) the deeper populations may be dominated by different microbial assemblages from that of the surface. From these collective observations, it now seems unequivocal that microstromatolite formation is intimately linked to microbial activity and that the sinter fabric results from a combination of biomineralization, cell growth and recolonization. Furthermore, the similarities in morphology and microbial component to some Precambrian stromatolites, preserved in primary chert, suggests that we may be witnessing contemporaneous biomineralization processes and growth patterns analogous to those of the early Earth.     

Diversification of skeletal microstructures of organisms through the interval from the latest Precambrian to the Early Cambrian

From the latest Precambrian to the Early Cambrian was the most important phase throughout the evolutionary history of life on the earth. The diversification of latest Precambrian multicellular organisms was obvious and some of them began to form primary s…     

Prevalence of Bacillus sp. among the biofilm forming community on Ti surface in marine environment

Prevalence of bacterial species involved in biomineralization of manganese on titanium (Ti) surfaces in marine environment was revealed in this research work. This study involves one year sea water exposure of Ti and their periodical biofilm characterization was carried out to quantify the manganese oxidizing bacterial (MOB) presence in the biofilm formed on titanium surfaces. The total viable count study of Ti coupons exposed to sea water for one year resulted in 60% of the MOB in overall biofilm population. The biochemical characterization of MOB isolates were performed for the genus level identification of the seven bacterial isolates. Further, the seven strains were subjected to 16S rRNA gene sequencing. Evolutionary analysis was performed using MEGA 7 to obtain closely related strains within the groups. The manganese oxidizing ability of the bacterial isolates were determined with Leucoberbelin Blue Assay (LBB) and Atomic Absorption Spectroscopy studies (AAS). The results show that among the isolated marine MOB species, Bacillus sp. and Leptothrix sp. have the maximum Mn oxidizing property. The microtitre plate assay was performed to determine the biofilm forming ability of the isolated marine MOB species. All the results have confirmed the prevalence of Bacillus sp. among the biofilm colonizers on Ti surfaces when exposed in sea water.     

无定形碳酸钙结合蛋白对鼠前成骨细胞MC3T3-E1碱性磷酸酶活性的影响

以 MC3T3-E1细胞系为实验材料,探讨了真核表达的重组蛋白 rACCBP 对成骨细胞的作用.结果表明:rACCBP 对 MC3T3-E1的分化具有抑制作用,用含有0.001 g/mL rACCBP 的 DMEM 培养液,培养8 d 后细胞的ALP 活性仅为7.187 U/mg,远低于参照的11.917 U/mg; rACCBP 削弱了 dexamethane 和 ascorbic acid 对 MC3T3-E1的诱导作用     

纳米磁铁矿链的仿生合成及其生物矿化意义

本文在不使用任何蛋白质或生物分子的情况下,以四方针铁矿和二价铁离子为铁源仿生合成磁铁矿纳米颗粒。实验 结果表明,在弱碱性条件下,合成的磁铁矿颗粒为35 nm左右的近似立方体,而且这些颗粒能够自发的定向排列,形成类 似趋磁细菌体内的磁小体链状结构。作者认为,由于磁铁矿晶体存在着固有的磁偶极,晶体之间的磁偶极作用力驱动着磁 铁矿颗粒自发组装成定向排列的链状结构。这就揭示了在趋磁细菌体内磁小体的矿化及组装链形成过程中,除了生物蛋白 影响外,磁小体颗粒之间的磁偶极吸引作用也可能是一个重要因素。生物蛋白和晶体化学因素可能在趋磁细菌体内生物矿 化过程中协同起作用。     

Carbonate deposition in a fluvial tufa system: processes and products (Corvino Valley – southern Italy)

In a multi‐scale approach to the study of the organic and mineral components in an active barrage‐type tufa system of southern Italy, neo‐formed deposits, in both natural depositional sites and on inorganic substrates placed in the stream for this study, were observed and compared through one year of monitoring. Dams and lobes representing the basic morpho‐facies of the deposits are composed of two depositional facies: vacuolar tufa (a mixture of phytoclastic and framestone tufa) and stromatolitic tufa (phytoherm boundstone tufa). Three petrographic components comprise both facies: micrite and microsparite, often forming peloidal to aphanitc, laminar and dendrolitic fabrics, and sparite, which occurs as isolated to coalescent fan‐shaped crystals forming botryoids or continuous crusts. All fabrics occurring in all depositional facies are organized into layers with a more or less well‐developed cyclicity, which has its best expression in stromatolitic lamination. The precipitation of all types of calcite (with Mg 1·0 to 3·2 mole % and Sr 0·5 to 0·8 mole %) takes place more or less constantly during all seasons, in spite of the low saturation state of the water (the saturation index range is 0·75 to 0·89) within the active depositional zone; the latter extends for a few hundred microns through the external surface of the deposit. The active depositional zone has a particular micro‐morphology composed of porous micro‐columns (50 to 150 μm in size), separated by interstitial channels. Mineral precipitation occurs upon both external surfaces and within internal cavities of the micro‐columns, while further point sites of precipitation occur suspended within the masses of cyanobacterial tufts. Sub‐spherical mineral units, ‘nano‐spheres’ (10 to 20 nm in diameter) are the basic biotic neo‐precipitate; they commonly form by replacing non‐living degrading organic matter and at point sites along the external surface of living cyanobacterial sheaths. Nano‐spheres agglutinate to form first rod‐shaped aggregates (100 to 200 nm) which then evolve into triads of fibres or polyhedral structures. Successively, both triads and polyhedral solids coalesce to form larger calcite crystals (mainly tetrahedrons tens of microns in size) that represent the fundamental bricks for the construction of the micro‐columns in the active depositional zone. Precipitation is attributed to the presence of a widespread biofilm that occurs in the active depositional zone; this is composed of a heterogeneous community comprising epilithic and endolithic filamentous cyanobacteria, green algae, unicellular prokaryotes, actinobacteria and fungi, with a variable amount of extracellular polymeric substances. No precipitation takes place where the biofilm is absent, indicating that the biological activities of the biofilm are crucial, with its living organisms and non‐living organic matter. Basic aggregates of neo‐precipitates do not form in association with any one particular type of organic matter substrate, but appear to be related to the seasonal temperature variation: polyhedral micro‐crystals mainly precipitate in the colder season, short triads in the intermediate seasons, and long triads in the warmest conditions. These three basic crystal aggregates have a petrographic counterpart, respectively, in the spar, microspar and micrite.