Electron microscopy of germinating ascospores ofSaccharomyces cerevisiae

The wall of mature ascospores ofSaccharomyces cerevisiae showed in sections under the electron microscope a dark outer layer and a lighter inner layer. The latter was composed of a greyish inner part and a light outer part. During germination, the spore grew out at one side and the dark outer layer was broken. Of the light inner layer, the inner greyish part became the wall of the vegetative cell, but the extented part of the cell had a new wall.     

The tapetum inSchizaea pectinata (Schizaeaceae) and a comparison with the tapetum inPsilotum nudum (Psilotaceae)

A combination tapetum consisting of a cellular, parietal component and a plasmodial component occurs inSchizaea pectinata. A single, tapetal initial layer divides to form an outer parietal layer which maintains its cellular integrity until late in spore wall development. The inner tapetal layer differentiates into a plasmodium which disappears after the outer exospore has developed. In the final stages of spore wall development, granular material occurs in large masses and is dispersed as small granules throughout the sporangial loculus. No tapetal membrane develops. Comparisons are drawn with the combination tapetum found inPsilotum nudum.     

Physiology and fine structure of sporangiospore germination in Piptocephalis unispora prior to infection

Germination of the sporangiospore of Piptocephalis unispora Benjamin, observed by means of light and electron microscopy, involved the formation of a new inner wall which became continous with the inner layer of the wall of the germ tube. The outer wall layer of the germ tube was continous with the original inner wall layer of the dormant spore. Preliminary details of appressorium structure were noted. Nutritional experiments indicated that sporangiospores required external sources of utilisable nitrogen and carbon compounds for maximal swelling and germ tube production. Limited development occurred when either nutrient was supplied singly. Comparison of germination of the asexual spore with that in other Mucorales, especially the Kickxellaceae, has been made, and the merosporangial status in P. unispora discussed.Non-Standard Abbreviations CH casein hydrolysate - Q spore quotient     

Cell wall structure of the agarophytes Gracilaria tikvahiae and G. cornea (Rhodophyta) and penetration by the epiphyte Ulva lactuca (Chlorophyta)

Use of light, transmission, and scanning electronmicroscopes revealed that the epidermal cell wall ofthe red algal agarophytes Gracilaria tikvahiaeMcLachlan and G. cornea J. Agardh consists of adecklamelle and outer and inner wall layers. The twospecies differed, with G. cornea having asignificantly thicker outer wall and a more diffusedecklamelle. After induction, the zooids of Ulvalactuca would attach to glass slides and the twospecies of Gracilaria via an adhesion pad. Within a few days, 3–5 celled germlings penetrated thedecklamelle and outer wall layer of both basiphytes. By the time the epiphyte germlings reached the 15celled stage, they had penetrated the inner walllayer. The differences in epidermal cell wallconstruction between the two basiphytes may play arole in the ability of zooids of U. lactuca toattach in nature where epiphytization of G.cornea is infrequent.     

Ultrastructure of spore development in <Emphasis Type="Italic">Scutellospora heterogama</Emphasis>

The ultrastructural detail of spore development in Scutellospora heterogama is described. Although the main ontogenetic events are similar to those described from light microscopy, the complexity of wall layering is greater when examined at an ultrastructural level. The basic concept of a rigid spore wall enclosing two inner, flexible walls still holds true, but there are additional zones within these three walls distinguishable using electron microscopy, including an inner layer that is involved in the formation of the germination shield. The spore wall has three layers rather than the two reported previously. An outer, thin ornamented layer and an inner, thicker layer are both derived from the hyphal wall and present at all stages of development. These layers differentiate into the outer spore layer visible at the light microscope level. A third inner layer unique to the spore develops during spore swelling and rapidly expands before contracting back to form the second wall layer visible by light microscopy. The two inner flexible walls also are more complex than light microscopy suggests. The close association with the inner flexible walls with germination shield formation consolidates the preferred use of the term ‘germinal walls’ for these structures. A thin electron-dense layer separates the two germinal walls and is the region in which the germination shield forms. The inner germinal wall develops at least two sub-layers, one of which has an appearance similar to that of the expanding layer of the outer spore wall. An electron-dense layer is formed on the inner surface of the inner germinal wall as the germination shield develops, and this forms the wall surrounding the germination shield as well as the germination tube. At maturity, the outer germinal wall develops a thin, striate layer within its substructure.     

Ovipositor ultrastructure of the striped bitterling Acheilognathus yamatsutae (Teleostei: Acheilognathinae) during spawning season

The ovipositor of striped bitterling Acheilognathus yamatsutae was subjected to ultrastructure and histochemical analysis during spawning season using light and electron microscopy. Although the ovipositor of A. yamatsutae is a long cylindrical tube with smooth external surface, it was possible to confirm the presence of well-developed fingerprint structure using scanning electron microscopy. Internal aspect analysis of ovipositor revealed formation of 5–8 longitudinal folds. Cross section analysis revealed that the ovipositor is composed of an outer epithelial layer, a mid connective tissue layer, and an inner epithelial layer. The outer epithelial layer contains 7–9 cell layers composed mainly of epithelial and mucous cells. Result of AB–PAS (pH 2.5) and AF–AB reaction showed that mucous cells contained mainly acidic carboxylated mucosubstances. The connective tissue layer was loose and made mainly of collagen fibers and some muscle fibers, along with blood vessels and a small number of chromatophores. The inner epithelial layer, which is a single layer, is composed of columnar epithelia. Observation under transmission electron microscope enabled distinction of the outer epithelial layer into superficial, intermediate and basal layers. Although the types of cells in the superficial tissue layer were diverse, they all shared the development of glycocalyx covered microridges. The majority of epithelial cells in the intermediate layer were cuboidal shaped, while those in the basal layer were columnar. Two types (A and B) of secretory cells were observed in the outer epithelial layer. The connective tissue layer had two types of chromatophores including xantophore and melanophore, in addition to a well-developed nerve fiber bundles. Columnar epithelial cells, mitochondria-rich cells and rodlet cells were observed in the inner epithelial layer. Microvilli were well developed on the free surface of columnar epithelial cells.     

Architecture of the cell wall of a green alga,Oocystis apiculata

Summary The cell wall of a green alga,Oocystis apiculata, was visualized by electron microscopy after preparation of samples by rapid-freezing and deep-etching techniques. The extracellular spaces clearly showed a random network of dense fibrils of approximately 6.4 nm in diameter. The cell wall was composed of three distinct layers: an outer layer with a smooth appearance and many protuberances on its outermost surface; a middle layer with criss-crossed cellulose microfibrils of approximately 15–17 nm in diameter; and an inner layer with many pores between anastomosing fibers of 8–10 nm in diameter. Both the outer and the inner layer seemed to be composed of amorphous material. Cross-bridges of approximately 4.2 nm in diameter were visualized between adjacent microfibrils by the same techniques. The cross-bridges were easily distinguished from cellulose microfibrils by differences in their dimensions.     

Zero order kinetics of cell wall turnover inStaphylococcus aureus

Cells exponentially grown from four strains ofS. aureus (SG 511, H, 52A5G, and248 PN-1) and uniformly labeled in their walls with³H-N-acetylglucosamine, were found to turn over their old walls at constant rates of up to 25% per generation. Wall turnover was not observed to follow first order kinetics, thus ruling out the implication that maintenance of normal wall thickness was achieved by a random distribution of new wall components in the old wall. Instead, wall turnover in all cases strictly followed zero order kinetics, indicating that newly synthesized wall material was placed layer by layer beneath the inner surface of the old cell wall. This finding correlates with evidence obtained from earlier electron microscopic investigations into the regeneration of the staphylococcal cell wall after chloramphenicol treatment. Based on the experimental data presented, a simplified model for wall turnover of the growing staphylococcal cell was proposed. The model also takes into account the finding, derived from additional experiments with strainSG 511, that the total cell wall turned over at a somewhat higher rate than the old portions of the wall. The rates of cell wall turnover found inS. aureus SG 511 are the highest reported to date for pathogenic bacteria. The medical implications of this finding were discussed.     

中华白花丹参与其近缘种的形态分类鉴定

该研究采用光学显微镜和扫描电镜相结合的方法,对中华白花丹参(Salvia sinealba)与其近缘种丹参(S.miltiorrhiza)及山东丹参(S.shandongensis)根的解剖学、叶表皮、花及花粉粒进行了系统地比较研究。结果表明:中华白花丹参(S.sinealba)根的中央部位有多数薄壁细胞,在根横切面射线薄壁细胞间及韧皮部外侧与次生皮层部位有多数裂隙;叶片上表皮细胞外平周壁具有细密平行丝状褶皱(SEM);花冠白色;花粉粒椭圆形,外壁具网状雕纹,网眼较大,多角形,少为单穿孔。上述这些显著的特征,不仅为中华白花丹参在植物分类学上的地位提供了形态解剖学依据,而且为近缘种丹参及山东丹参的分类鉴定提供了佐证,同时也为中华白花丹参这一特有新资源的保护和开发利用提供了资料。     

Development of the resting sporangia ofSynchytrium endobioticum,the causal agent of potato wart disease

Summary An ultrastructural study of the development of the resting sporangium ofSynchytrium endobioticum (Schilb.) Perc. infecting potato cells is presented. The resting sporangium is found to have a single large, centrally placed nucleus with a prominent nucleolus through its entirein situ development. The cytoplasmic organization of the resting sporangium is further characterized by numerous membrane-bound lipid bodies and osmiophilic bodies. The latter have a characteristic sieve-like appearance, probably because certain storage components have been extracted during preparation for electron microscopy. Because of the similar location and appearance of these osmiophilic bodies it is suggested that they are identical to what has earlier (based on light microscopy) been described as chromatin granules; and the ultrastructural studies presented here show that nucleolar discharge which was described from light microscopic observations as leading to chromatin granules in the cytoplasm, and finally forming the nuclei of the zoospores (bally 1912,curtis 1921,percival 1910) simply does not occur.The appearance of dense fibrillar-like structures on the sporangial surface at an early stage of resting sporangium development ultrastructurally distinguishes the resting sporangium from the zoosporangium. The development of the layered portion of the thick sporangial wall is shown to be due to the fusion of vacuoles containing pre-made wall fibrils with the cell membrane. It is suggested that the inner compact wall layer which is essentially substructureless is formed by the membrane itself.The characteristic wings of the matureS. endobioticum resting sporangium originate from the potato host cell wall. Remnants of host cell organelles in the outermost layer of the resting sporangium wall show that degradation of the host cell cytoplasm contributes to wall formation of the parasite.     

Discharge papilla development in the phycomycete Allomyces

The process of discharge papilla (DP) formation in Allomyces macrogynus was studied by light and electron microscopy. The plug of the DP was first deposited between the plasmalemma and the wall of the zoosporangium (ZS). The wall above the plug subsequently was eroded away. Deposition of a new inner wall layer in the sporangium held the plug in place and thickening of the layer formed a collar around the plug. Further deposition of material after this stage resulted in the characteristic pulley-shape. The plug material appeared homogeneous in electron micrographs but there was evidence of an outer layer. Digestion of the plug at the time of spore release was from within.Abbreviations DP discharge papilla - ZS zoosporangium     

Comparative studies onChlorella cell walls: Induction of protoplast formation

Among 12 strains ofChlorella ellipsoidea, C. vulgaris, andC. saccharophila tested, 4 strains (1,C. ellpsoidea; 2,C. vulgaris; 1,C. saccharophila) formed osmotically labile protoplasts after treatment with mixtures of polysaccharide degrading enzymes. The relationship between enzymatical digestibility and structure or composition ofChlorella cell walls were studied by electron microscopy and staining techniques with some specific dyes. The cell wall structures of the 12Chlorella strains were grouped into three types: (1) with a trilaminar outer layer, (2) with a thin outer monolayer, and (3) without an outer layer. Protoplasts were formed only from the strains with a cell wall of Type 2. In the strains with a cell wall of Type 1, the outer layer protected the inner major microfibrillar layer against enzymatic digestion. The cell wall of Type 3 was totally resistant to the enzymes; the chemical composition of the cell wall would be somewhat different from that of other types.     

Synthesis of the inner cell wall layer of the chlamydomonad flagellate,Gloeomonas kupfferi

Summary An antibody to the inner wall layer ofGloeomonas kupfferi was isolated and used in a developmental analysis of cell wall processing, secretion and extracellular assembly. The focus of the processing of this matrix layer is the endomembrane system, in particular the Golgi apparatus (GA) and contractile vacuole (CV). During interphase, inner wall materials are processed in the GA, packaged in trans face vesicles and transported to the CV, the final internal depository of wall precursors until release to the cell surface. During cell division, significant changes occur in the inner wall layer processing. Early on in cytokinesis, the GA does not label with our antibody, suggesting that other wall layers are being processed. In later stages of cytokinesis, the GA changes in morphology and begins to produce inner wall layer materials. These wall precursors are shuttled to the CV where they are released around the daughter cell protoplasts. The first wall layer that is formed around daughter cells is the crystalline median wall layer. Once assembled, the inner wall layer condenses upon the crystalline layer and grows in size.     

Germination and parasitation of the resting sporangia ofSynchytrium endobioticum

Summary The cytoplasmic organization of the long-lived, thick walled resting stage of the sporangium ofSynchytrium endobioticum (Schilb.) Perc. is described. The cytoplasm of the resting sporangium contains a large number of closely packed lipid bodies and irregular electron dense bodies, which are interspaced with fine channels of cytoplasm. These ultrastructural observations are discussed in relation to the hypothesis ofBally (1912) andCurtis (1921) that zoospore primordia are already present during the resting stage. It is shown that the zoospore primordium is actually a lipid body and an osmiophilic body and the strands postulated to connect the individual zoospore primordia are actually the fine channels of cytoplasm.A new inner wall layer is laid down prior to the start of the germination. It is this wall layer which will protrude to form the vesicle in which sporogenesis takes place. The germination process observed, protrusion of a vesicle through a crack in the sporangial wall, the migration of the sporangial content into the vesicle, and the formation of a single, membrane-bound sporangium within this vesicle, is in full agreement with the recent light microscopic studies ofSharma andCammack (1976). These observations support the transfer ofS. endobioticum from the subgenusMesochytrium to the subgenusMicrosynchytrium (bothsensu Karling 1964).A major objective of the study, to obtain ultrastructural evidence for the location of the meiotic divisions in the life cycle, was not fulfilled.Three different fungi were observed to parasitize the resting sporangium ofS. endobioticum. These infections are discussed in relation to other mycoparasites of plant pathogenic fungi. The possibility of using a mycoparasite for the biological control of potato wart disease is considered to be without practical relevance.     

Putative neurotransmitters in the retinae of three urodele species (Triturus alpestris,Salamandra salamandra,Pleurodeles waltli)

Summary The immunocytochemical localization of several substances with putative neurotransmitter or modulator properties was investigated in the retinae of three urodele species. Gamma-aminobutyric acid-like immunoreactive labelling appeared in different types of amacrine and horizontal cells. In addition, labelled fibres in the optic nerve were detected. It was not possible to determine whether these fibres were ganglion-cell axons or part of an efferent projection. Endogenous serotonin was found in several populations of amacrine cells including stratified and diffuse types. Glucagon-like immunoreactivity appeared in one bistratified amacrine cell type, and neurotensin-like immunoreactivity was detected in a single monostratified amacrine cell type. Metenkephalin-like-immunoreactive labelling was rare but found in several sublaminae of the inner plexiform layer. Thus each peptide-like-immunoreactive cell type makes up a distinct and unique population of cells and probably has a special functional role in retinal processing. There are striking similarities in the peptide-like immunoreactive patterns of Triturus alpestris and Necturus maculosus whereas in Ambystomatidae the peptide-like-immunoreactive systems appear to be differently organized. This supports the hypothesis that Salamandridae and Proteidae are more closely related to each other than to the Ambystomatidae.Abbreviations GABA gamma-aminobutyric acid - GCL ganglion cell layer - Glu glucagon - HRP horseradish peroxidase - INL inner nuclear layer - IPL inner plexiform layer - IR immunoreactive or immunoreactivity - M-enk metenkephalin - Neu neurotensin - OFL optic fibre layer - ONL outer nuclear layer - OPL outer plexiform layer - Ser serotonin This work forms part of the doctoral thesis of Gaby Gläsener, Faculty of Biology, Technical University of Darmstadt, Federal Republic of Germany. Supported by a research grant from the Deutsche Forschungsgemeinschaft (Hi 306/1-1)     

Two new species of <Emphasis Type="Italic">Neosartorya</Emphasis> from Amazonian soil,Brazil

Neosartorya indohii and N. tsurutae, two new Neosartorya species isolated from tropical rainforest soil in the Amazonian area, Brazil, are described and illustrated. Neosartorya indohii is characterized by its spreading growth on Czapeks and malt extract agars, light yellow cleistothecia, broadly lenticular ascospores with two conspicuously serrate-incised equatorial crests and tuberculate convex surfaces, and globose to subglobose conidia with a smooth wall. Neosartorya tsurutae is characterized by its spreading growth on Czapeks and malt extract agars, white cleistothecia, broadly lenticular ascospores with four equatorial crests and rugulose-ruminate convex surfaces, and ovoid to broadly ellipsoidal conidia with a smooth wall.     

Ultrastructural study of spore wall morphogenesis inOphioglossum thermale kom. var.nipponicum (Miyabe et Kudo) nishida

Spore wall morphogenesis ofOphioglossum thermale var.nipponicum was examined by transmission electron microscopy. The spore wall of this species consists of three layers: endospore, exospore, and perispore. The spore wall development begins at the tetrad stage. At first, the outer undulating lamellar layer of the exospore (Lo) is formed on the spore plasma membrane in advance of the inner accumulating lamellar layer (Li) of the exospore. Next, the homogeneous layer of the exospore (H) is deposited on the outer lamellar layer. Both lamellar layers may be derived from spore cytoplasm; and the homogeneous layer, from the tapetum. Then the endospore (EN) is formed. It may be derived from spore cytoplasm. The membranous perispore (PE), derived from the tapetum, covers the exospore surface as the final layer. Though the ornamentation of this species differs distinctly from that ofO. vulgatum, the results mentioned above are fundamentally in accordance with the data obtained fromO. vulgatum (Lugardon, 1971). Therefore, the pattern of spore wall morphogenesis appears to be very stable in the genusOphioglossum.     

Ultrastructure of infection-thread development during the infection of soybean by Rhizobium japonicum

The location and topography of infection sites in soybean (Glycine max (L.) Merr.) root hairs spot-inoculated with Rhizobium japonicum have been studied at the ultrastructural level. Infections commonly developed at sites created when the induced deformation of an emerging root hair caused a portion of the root-hair cell wall to press against an adjacent epidermal cell, entrapping rhizobia within the pocket between the two host cells. Infections were initiated by bacteria which became embedded in the mucigel in the enclosed groove. Infection-thread formation in soybean appears to involve degradation of mucigel material and localized disruption of the outer layer of the folded hair cell wall by one or more entrapped rhizobia. Rhizobia at the site of penetration are separated from the host cytoplasm by the host plasmalemma and by a layer of wall material that appears similar or identical to the normal inner layer of the hair cell wall. Proliferation of the bacteria results in an irregular, wall-bound sac near the site of penetration. Tubular infection threads, bounded by wall material of the same appearance as that surrounding the sac, emerge from the sac to carry rhizobia roughly single-file into the hair cell. Growing regions of the infection sac or thread are surrounded by host cytoplasm with high concentrations of organelles associated with synthesis and deposition of membrane and cell-wall material. The threads follow a highly irregular path toward the base of the hair cell. Threads commonly run along the base of the hair cell for some distance, and may branch and penetrate into subjacent cortical cells at several points in a manner analagous to the initial penetration of the root hair.     

黑龙江悬钩子属植物叶表皮形态结构的研究

利用扫描电子显微镜对黑龙江悬钩子属植物的叶表皮形态结构进行比较研究。结果显示:(1)悬钩子属植物叶的上表皮细胞呈多边形,垂周壁平直,或无规则形,垂周壁浅波纹;下表皮细胞无规则形,垂周壁浅波纹或深波纹。(2)表皮毛类型有单细胞直立不分支、卷曲不分支,头状腺毛和盾状腺毛四种类型。(3)气孔器均分布于下表皮,且气孔器类型为无规则形;气孔外拱盖单层、内缘平滑或不规则波状。研究表明,黑龙江悬钩子属植物的叶表皮微形态学特征表现出一定差异性,对种间的划分和鉴定具有一定的分类学意义。     

紫萁孢子囊发育中多糖和脂滴的细胞化学观察

采用光镜、透射电镜和细胞化学技术,对紫萁孢子囊发育过程中孢壁的超微结构和孢子囊内多糖和脂滴的分布及其动态变化进行研究,以探讨紫萁孢子囊发育过程中多糖和脂滴的代谢特征,为蕨类孢子发生的研究提供基础资料。结果表明:(1)紫萁孢子囊由1层囊壁细胞、2层绒毡层和产孢组织构成。(2)紫萁孢子壁由发达而分2层的外壁(外壁内层和外壁外层)和薄的不连续的周壁构成,由外壁形成棒状纹饰的轮廓;孢子外壁内层由多糖类物质构成,外壁外层和周壁均含有脂类物质。(3)在紫萁孢原细胞中观察到少量脂滴;随着紫萁孢壁的形成,囊壁细胞中淀粉粒的大小逐渐变小、数目先增加后减少,它们转运到内层绒毡层原生质团并转化为孢粉素前体物质,再穿过原生质团内膜表面进入囊腔,成为孢粉素团块或以小球形式填加到孢子表面形成孢壁。(4)紫萁孢子囊将多糖类营养物质转化为脂类,以脂滴的形式储藏在孢子中。