植物电子显微镜的负染和投影技术

电子显微镜技术是目前生物学研究中重要的手段之一。运用电镜开展研究,不仅要有高分辨本领的仪器,而且要有精心制备的样品。由于生物样品的电子散射力很低,如不经过特殊处理,样品的反差极弱,观察精细结构几乎不可能。因此,样品制备的质量在利用电镜的研究中具有极其重要的地位。制备样品的技术包括超薄切片、负染、投影、复型等,本文着重介绍负染和投影技术。     

禾本科植物超薄切片应注意的问题

在透射电镜的生物样品制备方法中,超薄切片技术是最基本、最常用的制备技术,一般来说,植物样品的超薄切片比动物样品难度要大,而在植物材料中,禾本科植物材料的制样又特别困难,因为禾本科植物(如水稻、小麦、玉米、高梁、甘蔗等)质地坚硬,细胞壁角质化,并且充满硅质,它们对固定液的渗透具有不可忽视的障碍作用,按常规的生物样品制备方法常常失败或效果不佳。样品制备的好坏,很大程度上依赖于操作者的经验和操作技术,作者近几年来对禾本科植物叶片做了一些超薄切片工作,体会到要获得较理想的超薄切片,必须十分认真地对待制样过程中的每一操作步骤,任何环     

鄂尔多斯盆地延长组长7优质烃源岩中超微化石的发现及意义

运用扫描电子显微镜及能谱分析仪,对鄂尔多斯盆地里57井等钻孔共计49个三叠系延长组长7优质烃源岩(油页岩)样品进行了微体、超微化石的直接观察与研究.发现了6种形态的微体、超微化石,其中有3种超微化石仅在很少的样品中见到,化石数量呈现剧烈变化的特征,记录了在相似古地理环境下一个或多个物种短暂勃发与消亡的演变过程,揭示了湖...     

苏北盆地阜宁组钙质超微化石由来初探

对苏北盆地4个钻孔300余块心样品进行了分析,在阜宁组的8块样品中发现了钙质超微化石,计3属1种及3个比较种,化石属种单调,保存较 ,受到严重的溶蚀或增生,结合这些种类的分布时代和产出层位,很难排除苏北盆地阜宁组钙质超微化石再沉积的属性。     

低温电镜技术及其在植物（动物）材料研究中的应用

通过一些实例介绍了高压冷冻,冷冻置换和冷冻超薄切片等低温电镜样品制备技术,并且与传统方法对照,说明低温电镜技术的优越性,其中,发菜（Nostoc flagelliforme)营养细胞的冷冻超薄切片（未经化学固定,脱水）所显示的超微结构更客观地反映了生物样品的自然生理状态。此外,应用高压冷冻和冷冻置换的免疫标记电镜技术,首次对发菜营养细胞中的DNA进行定位,明确了核区的位置及范围。     

前寒武纪沉积碎屑岩中有机质壁微体化石的分析处理及观察方法

前寒武纪是地球演化历史上的重要时期,随着早期生命起源、构造演化、油气勘探等研究的不断深入,前寒武纪越来越受到关注。微体化石是研究前寒武纪生命演化和地层对比的重要窗口,尤其是在新元古代大冰期之前的地层中,主要保存的是体型较小、类型多样的微体化石,而宏体化石则凤毛麟角,仅有为数不多的类型。在许多前寒武纪碎屑岩地层中,以布尔吉斯页岩型方式保存的有机质壁微体化石,是其中保存的唯一的化石类型。但因这些有机质壁微体化石在围岩中遭受了长时间地成岩、变质、风化和剥蚀等作用,在化石处理过程中非常容易破碎,导致获取保存完整的微体化石较为困难,给属种鉴定、生物多样性评估和生物地层对比等研究带来诸多不便。本文主要介绍一种从粉砂岩-泥岩中获取有机质壁微体化石的处理方法,包括样品的碎样、酸处理、富集、挑选、制片和拍照等各流程的详细步骤,以及在分析处理中存在的问题和注意事项。     

浅议峡东陡山沱组的“瓶状微化石”

通过对峡东晚震旦世陡山沱组岩石样品的化学浸解处理、连续切片研究及大量薄片观察,作者认为先前报道的陡山沱组“瓶状微化石”,即所谓最古老的原生动物的外壳遗骸,实际上并非什么瓶状微化石,而是一种有蓝藻（可能还有细菌）参与的沉积构造。     

应用于电镜生物制样的几项技术

随着电镜技术的不断发展,生物制样方法也日益丰富,虽然透射电镜超薄切片样品制备、扫描电镜常规及“O-D-O”冷冻断裂样品制备等方法已成为规范的手段,并被广为应用,但广大生物工作者对这些规范方法中的个别处理步骤,仍在探索用新的处理技术取代、完善或丰富它们。笔者基于自己工作实践并综合有关文献,对以下几项技术作些介绍。     

电镜上的生物样品制备技术

电子显微镜为我们提供了很高的分辨本领,使我们能观察到生物样品的超微结构,丰富了人们对微观世界的认识,推动了生物学从细胞水平发展到分子水平。生物超微结构研究的新成就,是跟样品制备技术的不断提高和逐步完善分不开的。但目前已有的样品制备技术还远不能充分利用电镜本身的巨大发展,例如,目前用超薄切片法只能     

南海西沙群岛西科1井早中新世—第四纪生物礁地层中钙质超微化石的发现及其意义

西科1井0.10—1267.80m岩芯中钙质超微化石丰度低,属种比较单调。分析831个样品,仅在48个样品中发现钙质超微化石,共鉴定10属17种及1个未定种,主要化石种为Calcidiscus leptoporus,C.macintyrei,Coccolithus pelagicus,Cyclicargolithus floridanus,Gephyrocapsa caribbeanica,G.oceanica,Helicosphaera carteri,H.euphratis,Pontosphaera multipora,Pseudoemiliania lacunosa,Reticulofenestra minuta,R.minutula,Sphenolithus abies,S.moriformis和S.neoabies等。根据钙质超微化石生物事件及组合特征,结合有孔虫和大型底栖钙藻等研究结果,对西科1井0.10—1267.80m地层进行了划分,大致可划分为5段:1)0.10—212.20m地层属于第四系NN21—NN19带;2)214.29—328.69m归属于更新统NN18带至上新统;3)330.97—598.12m属于上新统NN15带至上中新统;4)599.53—1231.62m归属于中中新统至下中新统;5)1233.62—1267.80m为下中新统。由于化石丰度和分异度均较低,未建立完整的钙质超微化石带序列。根据钙质超微化石标志种及组合特征,确定研究井段的地层时代为早中新世至第四纪。西科1井生物礁地层中钙质超微化石的发现,对该井生物地层的划分起到了十分关键的作用。     

Experimental precipitation of apatite pseudofossils resembling fossil embryos

Certain phosphatic grains preserved in the rock record are interpreted as microfossils representing a diversity of microorganisms from bacteria to fossil embryos. In addition to bona fide primary biological features, phosphatic microfossils and fossil embryos commonly exhibit features that result from abiotic precipitation or diagenetic alteration. Distinguishing between abiotic and primary biological features can be difficult, and some features thought to represent biological tissue could instead be artifacts that are unrelated to the original morphology of a preserved organism. Here, we present experimentally generated, abiotically produced mineral precipitates that morphologically resemble biologically produced features, some of which may be observed in the rock record or noted in extant organisms, including embryos. These findings extend the diversity of biomorphic features known to result from abiotic precipitation.     

Vibrational spectroscopy of fossils

Over the last two decades, there has an been increasing interest in applying vibrational spectroscopy in palaeontological research. For example, this chemical analytical technique has been used to elucidate the chemical composition of a wide variety of fossils, including Archaean putative microfossils, stromatolites, chitinozoans, acritarchs, fossil algae, fossil plant cuticles, putative fossil arthropods, conodonts, scolecodonts and dinosaur bones. The insights provided by these data have been equally far ranging: to taxonomically identify a fossil, to determine biogenicity of a putative fossil, to identify preserved biologically synthesized compounds and to elucidate the preservational mechanisms of fossil material. Vibrational spectroscopy has clearly been a useful tool for investigating various palaeontological problems. However, it is also a tool that has been misapplied and misinterpreted, and thus, this review is dedicated to providing a palaeontologist who is new to vibrational spectroscopy with a basic understanding of these techniques, and the types of chemical information that can be obtained. Two example applications of these techniques are discussed in detail, one looking into fossil palynomorph taxonomy and other into the enigmatic Burgess Shale‐type preservation.     

Multi-trichomous cyanobacterial microfossils from the Mesoproterozoic Gaoyuzhuang Formation, China: Paleoecological and taxonomic implications

Populations of the multi-trichomous microbial fossil Eoschizothrix composita n.gen. et sp. are preserved in growth position in silicified stratiform stromatolites of the Gaoyuzhuang Formation, Hebei Province, northern China. The microbial fossils consist predominantly of preserved sheaths, although several specimens retain shriveled remains of trichomes within sheaths. Comparisons with modern morphological counterparts, including shape, growth habit and orientation, degradational sequences, and habitat, support the interpretation of the multi-trichomous microfossils as cyanobacteria, which acted as frame-builders of ancient stromatolites. The distribution and orientation of multi-trichomous microfossils within a synsedimentary context reveal their behavioral responses to sedimentation regime. Horizontally spread, interwoven mats formed during periods of sedimentary stasis. During periods of rapid sediment influx, the filaments assumed an upright orientation, possibly to avoid accumulating particles. This is the first record of fossil stromatolite-building multi-trichomous cyanobacterial which underscores early morphological and functional diversification in cyanobacterial evolution.     

陕西西乡灯影组顶部的瓶状微化石

瓶状微化石被认为是某种未知海相原生动物外壳化石,最早出现于９００－８５０Ｍａ以前。本文记述的该类化石,产自陕西西乡三郎铺小湾里下寒武统灯影组顶部杨家沟段,相当于梅树村阶中－上部,计１０属,１３种和２未定种。所获化石个体数量及形态类型丰富。保存良好,并见有大量具公共壳壁的连体壳。此类连体壳的连接程度呈系列变化。可能代表处于分裂状态的生物体,如是则可为其原生动物解释提供一佐证,瓶状微化石在国外的地层分     

Fungal remains from the Late Riphean

The paper describes organic remains of one billion years old from the Lakhanda microbiota of the Uchur-Maya Region of southeastern Siberia. The microfossils were discovered on organic sapropelic films. The preserved morphological characters and some developmental stages of the ancient organisms, which are fixed in fossil state, suggest that some of them resembled zygomycetes. Other microfossils under consideration are comparable to reproductive structures of myxomycetes in the type of fusion of spheroid cells and formation of various types of aggregation (sori). Colonies of unicellular microfossils that are arranged in a branching pseudomycelium superficially resemble yeasts. The presence in the same biota of fungal remains belonging to the Myxomycota and Mycota, as well as members of xanthophyte vaucherian algae, indicates that various branches of eukaryotes might have developed in parallel even earlier than the Late Riphean.     

Snapshot of an early Paleoproterozoic ecosystem: Two diverse microfossil communities from the Turee Creek Group,Western Australia

Eighteen microfossil morphotypes from two distinct facies of black chert from a deep‐water setting of the c. 2.4 Ga Turee Creek Group, Western Australia, are reported here. A primarily in situ, deep‐water benthic community preserved in nodular black chert occurs as a tangled network of a variety of long filamentous microfossils, unicells of one size distribution and fine filamentous rosettes, together with relatively large spherical aggregates of cells interpreted as in‐fallen, likely planktonic, forms. Bedded black cherts, in contrast, preserve microfossils primarily within, but also between, rounded clasts of organic material that are coated by thin, convoluted carbonaceous films interpreted as preserved extracellular polymeric substance (EPS). Microfossils preserved within the clasts include a wide range of unicells, both much smaller and larger than those in the nodular black chert, along with relatively short, often degraded filaments, four types of star‐shaped rosettes and umbrella‐like rosettes. Large, complexly branching filamentous microfossils are found between the clasts. The grainstone clasts in the bedded black chert are interpreted as transported from shallower water, and the contained microfossils thus likely represent a phototrophic community. Combined, the two black chert facies provide a snapshot of a microbial ecosystem spanning shallow to deeper‐water environments, and an insight into the diversity of life present during the rise in atmospheric oxygen. The preserved microfossils include two new, distinct morphologies previously unknown from the geological record, as well as a number of microfossils from the bedded black chert that are morphologically similar to—but 400–500 Ma older than—type specimens from the c. 1.88 Ga Gunflint Iron Formation. Thus, the Turee Creek Group microfossil assemblage creates a substantial reference point in the sparse fossil record of the earliest Paleoproterozoic and demonstrates that microbial life diversified quite rapidly after the end of the Archean.     

Fossilization of Acidophilic Microorganisms

This study examines fossil microorganisms found in iron-rich deposits in an extreme acidic environment, the Tinto River in SW Spain. Both electron microscopy (SEM and TEM) and non-destructive in situ microanalytical techniques (EDS, EMP and XPS) were used to determine the role of permineralization and encrustation in preserving microorganisms forming biofilms in the sediments. Unicellular algae were preserved by silica permineralization of their cell walls. Bacterial biofilms were preserved as molds by epicellular deposition of schwertmannite around them. In the case of fungi and filamentous algae, we observed permineralization of cell structures by schwertmannite in the sediments. The extracellular polymeric matrix around the cells was also preserved through permineralization of the fibrillar component. The process of permineralization and deposition of iron-rich precipitates present in the acidic waters of Rio Tinto served to preserve many microfossils in an oxidizing environment, in which organic compounds would not normally be expected to persist. Studies of microbial fossil formation mechanisms in modern extreme environments should focus on defining criteria to identify inorganic traces of microbial life in past environments on Earth or other planets.     

The fossil bat assemblage of Sima del Elefante Lower Red Unit (Atapuerca,Spain): First results and contribution to the palaeoenvironmental approach to the site

The fossil bat assemblage from the Lower Red Unit of Sima del Elefante (TELRU) in Atapuerca (Burgos, Spain) has been exhaustively analysed for the first time. Bat fossil assemblages are of particular relevance to palaeoenvironmental approaches to sites. Here we integrate our new data on the chiropteran fauna with the data provided previously by other authors on the basis of the small-vertebrate assemblages and the palynology of the site. Our results are consistent with the earlier results in that they indicate a generally warmer climate than at present in the area and stable environmental conditions throughout the major part of the TELRU sequence. However, fossil bat assemblages sometimes lead to problems when they are used in landscape reconstruction. These problems are discussed here and should be taken into account in future works.     

华北高于庄组硅化微体化石组合的古环境

华北中元古代高于庄组 ( 1 4- 1 5亿年 )的硅质叠层石中保存了完好的多种微生物化石。从这些叠层石的微细构造分析 ,成岩早期硅质矿物的交代作用为微体化石的原位保存起了很重要的作用。除部分居住者和浮游的分子外 ,两种丝状蓝藻 ( Siphonophycus inornatum和Eoschizothric composita)和两种球状蓝藻 ( Coccostratusdispergens和 Eoentophysalisbelcherensis)是这些藻席的主要建造者。以球状蓝藻 Eoentophysalis为主的藻席可能发育于潮下高能环境中 ;而以多种丝状蓝藻为主的藻席可能反映了当时的沉积环境为中—高潮间带的局部静止小水体