Electron-dense Layer Research Articles

The chitinase genes TuCht4 and TuCht10 are indispensable for molting and survival of Tetranychus urticae

Insect chitinases (Chts) play a crucial role in the molting process, enabling continuous growth through sequential developmental stages. Based on their high homology to insect Chts, TuCht1 (group II), TuCht4 (group I) and TuCht10 (group IV) were identified, and their roles during molting process were investigated. TuCht1 was mainly expressed in the deutonymphal stage, while TuCht4 was mainly expressed in the nymphal stage and the highest expression level of TuCht10 was observed in the larvae. Feeding RNAi assays have shown that group I TuCht4 and group Ⅳ TuCht10 are involved in mite molting. Suppression of TuCht4 or TuCht10 resulted in high mortality, molting abnormalities and the absence of distinct electron dense layers of chitinous horizontal laminae in the cuticle, as demonstrated by scanning electron microscopy and transmission electron microscopy. The nanocarrier mediated RNAi had significantly higher RNAi efficiency and caused higher mortality. The results of the present study suggest that chitinase genes TuCht4 and TuCht10 are potential targets for dietary RNAi, and demonstrates a nanocarrier-mediated delivery system to enhance the bioactivity of dsRNA, providing a potential technology for green pest management.

Ultrastructural and glycoproteomic characterization of Prevotella intermedia: Insights into O-glycosylation and outer membrane vesicles.

Prevotella intermedia, a Gram-negative bacterium from the Bacteroidota phylum, is associated with periodontitis. Other species within this phylum are known to possess the general O-glycosylation system. The O-glycoproteome has been characterized in several species, including Tannerella forsythia, Porphyromonas gingivalis, and Flavobacterium johnsoniae. In our study, we used electron cryotomography (cryoET) and glycoproteomics to reveal the ultrastructure of P. intermedia and characterize its O-glycoproteome. Our cryoET analysis unveiled the ultrastructural details of the cell envelope and outer membrane vesicles (OMVs) of P. intermedia. We observed an electron-dense surface layer surrounding both cells and OMVs. The OMVs were often large (>200 nm) and presented two types, with lumens being either electron-dense or translucent. LC-MS/MS analyses of P. intermedia fractions led to the identification of 1655 proteins, which included 62 predicted T9SS cargo proteins. Within the glycoproteome, we identified 443 unique O-glycosylation sites within 224 glycoproteins. Interestingly, the O-glycosylation motif exhibited a broader range than reported in other species, with O-glycosylation found at D(S/T)(A/I/L/M/T/V/S/C/G/F/N/E/Q/D/P). We identified a single O-glycan with a delta mass of 1531.48 Da. Its sequence was determined by MS2 and MS3 analyses using both collision-induced dissociation and high-energy collisional dissociation fragmentation modes. After partial deglycosylation with trifluoromethanesulfonic acid, the O-glycan sequence was confirmed to be dHex-dHex-HexNAc (HPO3 -C6 H12 O5 )-dHex-Hex-HexA-Hex(dHex). Bioinformatic analyses predicted the localization of O-glycoproteins, with 73 periplasmic proteins, 53 inner membrane proteins, 52 lipoproteins, 26 outer membrane proteins, and 14 proteins secreted by the T9SS.

Morphology and wall ultrastructure of a unique megaspore, Flabellisporites zhaotongensis Sui, McLoughlin et Feng sp. nov., from the upper Permian of Southwest China

A new lycopsid megaspore species with intricate ornamentation, Flabellisporites zhaotongensis Sui, McLoughlin et Feng sp. nov., is described from the Lopingian Xuanwei Formation of Yunnan Province, Southwest China, using scanning and transmission electron microscopy. This trilete megaspore is characterized by elevated membraneous flanges adorned with multifurcate spines, the longest of which are discrete ribbon-like appendages that basally converge to form a membrane around the equator; and evenly spaced single or bifurcate spines with sharp tips covering the remaining surfaces. Ultrastructural analysis reveals that the megaspore wall consists of four layers: (1) a thin and dense foot layer; (2) an inner spongy layer with small circular or elongate sporopollenin grains with parallel arrangement; (3) an outer, more porous, spongy layer consisting of larger and better interconnected sporopollenin units, that form a grid-like structure in certain cases; and (4) an electron-dense outermost layer forming the sculptural elements. Both morphological and ultrastructural characteristics indicate that the new megaspore species belongs to Isoetales. Our discovery represents the oldest occurrence of Flabellisporites, indicating the origin of this morpho-lineage before the end-Permian mass extinction, and enriches the known diversity of isoetalean lycopsids in the late Permian Cathaysian Flora.

Biogenic silica: A promoter of cell wall strengthening and induced resistance against sheath blight disease in rice via salicylic acid signaling and phenolic metabolism

Sheath blight disease has recently spread in Egypt; particularly, there are no sources of cultivar resistance to the disease worldwide, so silicon has a vital role as part of the management of sheath blight disease in rice. The aim of the study is to use different sources of silica as compared to fungicides to control sheath blight on rice. In addition, resistance mechanisms between the host and pathogen after treating the host with silica were investigated. The results of study show white rice husk ash (WRHA) application was more effective in stopping the development of rice sheath blight disease, had less dense mycelium growths, increasing silica cell content, and there are more guard cells around the stoma on the leaves' surface. The epidermal cell walls of treated plants with WRHA were generally thicker than those of uninoculated ones. Electron-dense silicon layers were easily discernible in the epidermal cell walls of silicon-treated plants. Ultra-structural changes in the chloroplast were observed and revealed that treated leaves with WRHA were full and clear. Silica incorporated into the soil and sprayed on rice plants at the vegetative growth stages played a significant role in inducing rice resistance to sheath blight disease. Gene expression analysis demonstrated an accumulation of salicylic acid (SA)-linked transcriptions on diverse sources of silica treatment. Two days following the inoculation, these genes, OsNPR1 and OsWRKY45, recorded 14.45 and 11.52-fold changes, respectively, with rice treated by WRHA. Phenolic metabolisms were increased in rice plants treated with WRHA and inoculated with Rhizoctonia pathogen.

Detection and evaluation of different morphological forms of Mycoplasma hominis in human semen.

Recently discovered microcolonial forms of Mycoplasma hominis ( M. hominis ) and their impact on human spermatogenesis are studied. The spermatozoa of 125 fertile men (sperm donors; from Reprobank [Reproductive Tissue Bank, Moscow, Russia]) and of 93 patients with fertility problems (from the Federal State Budgetary Institution "Research Centre for Medical Genetics [RCMG]", Moscow, Russia) were used. Classical colonies of M. hominis and microcolonies were detected by molecular biological methods, culture of bacteria, and transmission electron microscopy. The unique structure of microcolonial cells, in which the cytoplasmic cylinder is surrounded by concentric electron-dense and electron-light layers with a periodicity of 12-14 nm, and the ability of microcolonial cells to attach to spermatozoa are shown. In patients with lower sperm quality, microcolonies of M. hominis were detected 2.5 times more frequently than classical colonies. The detection of microcolonies in the ejaculate and the frequent isolation of microcolonies from sperm samples of patients with fertility problems suggest that microcolonial cells may be one cause of infertility.

Two new isoetalean (Lycopsida) megaspore species representing the earliest occurrence of Henrisporites from upper Permian strata of Southwest China

Two distinctive lycopsid megaspore species, Henrisporites yunnanensis Sui, McLoughlin et Feng sp. nov. and H. qujingensis Sui, McLoughlin et Feng sp. nov., are described from the Lopingian Xuanwei Formation of Yunnan Province, Southwest China, using scanning and transmission electron microscopy. Henrisporites yunnanensis is characterized by prominent membranous triradiate labra with ragged margins, a broad irregularly serrated membranous zona with radiating spiny extensions, and ramified or unbranched spines on the spore surface, those on the distal surface especially having capillate termini. Punctatisporites-type microspores occur adhering to the megaspore surface. The megaspore wall incorporates four layers, viz., from inside to outside: (1) a thin and dense foot layer especially thickened at the laesurae lips; (2) a moderately-thick layer with small circular and loosely distributed sporopollenin grains with parallel arrangement; (3) a thick spongy layer consisting of elongate, curved and interconnected sporopollenin units perpendicular to the inner layers; and (4) an electron-dense outermost layer forming the ornamentation. Henrisporites qujingensis has lower membranous labra, a generally continuous membranous zona with radiate spiny margins but, in some cases, dissected into single fimbria, and bearing sparsely distributed and locally forked stubby spines over the spore surface. Henrisporites qujingensis also has a four-layered wall. The innermost thin foot layer is covered by a loose layer of tiny parallel sporopollenin grains. A thick spongy layer is developed exterior to the second layer and comprises elongate, curved, and intersecting sporopollenin units forming a porous zone. The outermost layer consists of varied sculptural processes with contrasting densities between the proximal and distal surfaces. The morphological and ultrastructural characteristics suggest that these new megaspores belong to Isoetales. Our discovery represents the earliest global occurrence of Henrisporites, which has been documented exclusively from the Mesozoic in previous studies.

Zygospores of the green alga Spirogyra: new insights from structural and chemical imaging.

Zygnematophyceae, a class of streptophyte green algae and sister group to land plants (Embryophytes) live in aquatic to semi-terrestrial habitats. The transition from aquatic to terrestrial environments requires adaptations in the physiology of vegetative cells and in the structural properties of their cell walls. Sexual reproduction occurs in Zygnematophyceae by conjugation and results in the formation of zygospores, possessing unique multi-layered cell walls, which might have been crucial in terrestrialization. We investigated the structure and chemical composition of field sampled Spirogyra sp. zygospore cell walls by multiple microscopical and spectral imaging techniques: light microscopy, confocal laser scanning microscopy, transmission electron microscopy following high pressure freeze fixation/freeze substitution, Raman spectroscopy and atomic force microscopy. This comprehensive analysis allowed the detection of the subcellular organization and showed three main layers of the zygospore wall, termed endo-, meso- and exospore. The endo- and exospore are composed of polysaccharides with different ultrastructural appearance, whereas the electron dense middle layer contains aromatic compounds as further characterized by Raman spectroscopy. The possible chemical composition remains elusive, but algaenan or a sporopollenin-like material is suggested. Similar compounds with a non-hydrolysable character can be found in moss spores and pollen of higher plants, suggesting a protective function against desiccation stress and high irradiation. While the tripartite differentiation of the zygospore wall is well established in Zygnematopyhceae, Spirogyra showed cellulose fibrils arranged in a helicoidal pattern in the endo- and exospore. Initial incorporation of lipid bodies during early zygospore wall formation was also observed, suggesting a key role of lipids in zygospore wall synthesis. Multimodal imaging revealed that the cell wall of the sexually formed zygospores possess a highly complex internal structure as well as aromatics, likely acting as protective compounds and leading to impregnation. Both, the newly discovered special three-dimensional arrangement of microfibrils and the integration of highly resistant components in the cell wall are not found in the vegetative state. The variety of methods gave a comprehensive view on the intricate zygospore cell wall and its potential key role in the terrestrial colonization and plant evolution is discussed.

Identification and characterization of epicuticular proteins of nematodes sharing motifs with cuticular proteins of arthropods.

Specific collagens and insoluble proteins called cuticlins are major constituents of the nematode cuticles. The epicuticle, which forms the outermost electron-dense layer of the cuticle, is composed of another category of insoluble proteins called epicuticlins. It is distinct from the insoluble cuticlins localized in the cortical layer and the fibrous ribbon underneath lateral alae. Our objective was to identify and characterize genes and their encoded proteins forming the epicuticle. The combination between previously obtained laboratory results and recently made available data through the whole-genome shotgun contigs (WGS) and the transcriptome Shotgun Assembly (TSA) sequencing projects of Ascaris suum allowed us to identify the first epicuticlin gene, Asu-epic-1, on the chromosome VI. This gene is formed of exon1 (55 bp) and exon2 (1067 bp), separated by an intron of 1593 bp. Exon 2 is formed of tandem repeats (TR) whose number varies in different cDNA and genomic clones of Asu-epic-1. These variations could be due to slippage of the polymerases during DNA replication and RNA transcription leading to insertions and deletions (Indels). The deduced protein, Asu-EPIC-1, consists of a signal peptide of 20 amino acids followed by 353 amino acids composed of seven TR of 49 or 51 amino acids each. Three highly conserved tyrosine motifs characterize each repeat. The GYR motif is the Pfam motif PF02756 present in several cuticular proteins of arthropods. Asu-EPIC-1 is an intrinsically disordered protein (IDP) containing seven predicted molecular recognition features (MoRFs). This type of protein undergoes a disorder-to-order transition upon binding protein partners. Three epicuticular sequences have been identified in A. suum, Ascaris lumbricoides, and Toxocara canis. Homologous epicuticular proteins were identified in over 50 other nematode species. The potential of this new category of proteins in forming the nematode cuticle through covalent interactions with other cuticular components, particularly with collagens, is discussed. Their localization in the outermost layer of the nematode body and their unique structure render them crucial candidates for biochemical and molecular interaction studies and targets for new biotechnological and biomedical applications.

Identification of Lipopeptide Iturin A Produced by Bacillus amyloliquefaciens NCPSJ7 and Its Antifungal Activities against Fusarium oxysporum f. sp. niveum.

Bacillus amyloliquefaciens NCPSJ7 showed potential fungicidal activities for the effective control of fungal infection. From the PCR test, the key genes (srfAA, sfp, fenD, bmyB, ituD, and ituC) were detected in B. amyloliquefaciens NCPSJ7. These genes were closely related to the lipopeptides (LPs) synthesis. Next, three LPs families were identified with liquid chromatography–mass spectrometry (LC/MS), including iturin A, fengycin A, and surfactin. After purification with C18, the main active antifungal compound was proven to be C14-iturin A by ESI-HRMS, which has significant activities against fungi. These results proved that C14-iturin A played an important role in inhibiting the growth of fungi for B. amyloliquefaciens NCPSJ7. Furthermore, the isolated LP could inhibit mycelial growth and conidia germination at 30 μg/mL. SEM allowed us to observe that mycelial morphology and conidia germination were also affected. The mycelial ultrastructure TEM observations showed that the external electron-dense outer layer cell wall, which mainly consisted of glycoproteins, was affected. Furthermore, swollen mitochondria, enriched glycogen, and increased vacuoles were also found. LP also affected the intact wall and membranes, leading to their increased permeability, which was proved by propidium iodide (PI) staining and conductivity measurements. Meanwhile, the ergosterol, which has an affinity for iturin A, also increased. These results indicated that LP caused fungal dysfunction and membrane permeability increase, leading to fungal inhibition. Identifying and studying LPs is important in exploring the fungicidal activities of B. amyloliquefaciens, which promotes the use of B. amyloliquefaciens NCPSJ7 as a potential candidate for biocontrol.

Light and electron microscopic morphology of the fertilized egg and fertilized egg envelope of Poropanchax normani, Poeciliidae, Teleostei

We examined the morphology of the fertilized egg and the fine structure of fertilized egg envelopes of Poropanchax normani belonging to the family Poeciliidae, also known as Norman’s lampeye using light and electron microscopes. The fertilized eggs with narrow perivitelline space were found to be spherical and demersal, additionally containing small oil droplets in the vitelline membrane. Further, a bundle of adhesive filaments was observed to be present on one side of the fertilized egg. These filaments possessed remarkably high elasticity and were approximately 1-3 mm in length. The size of the fertilized egg was determined to be about 1.49 ± 0.07 mm (n = 30). The outer surface appeared smooth, and adhesive filaments originating at different location of the surface of the envelope were found to be distributed around the egg envelope and were joined together to form a single long bundle in scanning electron microscopic observation. A peak-like structure formed of several straight wrinkles was observed around the micropyle. However, the complete structure of the micropyle could not be studied due to the depth at which it was located. Additionally, the total thickness of the egg envelope was ascertained to be approximately12.5–14.5 μm. The egg envelope consisted of two distinct layers, an outer electron dense layer and an inner lamellar layer, further consisting of 10 sublayers of varying thicknesses. Collectively, it was observed that the morphological characteristics of the fertilized egg, fine structures surrounding the micropyle, outer surface, adhesive structure consisting adhesive filaments, and sections of fertilized egg envelope displayed species specificity.

Abstract OR-5: Helicobacter pylori Surface Structures

Background: Helicobacter pylori, which infects at least half of the human population, is an etiopathogenetic factor in the development of chronic gastritis (CG), gastric and duodenal ulcer disease (UD), and is also considered a risk factor in the occurrence of some forms of stomach cancer. Various surface structures of H. pylori are important pathogenic factors. Methods: Reference (NCTC 11637, NCTC 11639) and freshly isolated H. pylori strains as well as samples of the gastric mucosa were examined using transmission (TEM) and scanning electron microscopy (SEM) by means of “JEM-100 В” (JEOL, Japan) and “Quanta 200 3D” (FEI Company, USA) systems, respectively. Samples for SEM fixed with formalin and not subjected to dehydration were sprayed with an electrically conductive layer of gold. Samples for TEM were prepared using negative contrast (NC) with ammonium molybdate and ultrathin sections (US) contrasted by Reynolds; fixation by Ito-Karnovsky was used in both cases. Accelerating voltage at TEM and SEM was 80 and 10 kV, respectively. Results: Three types of H. pylori surface structures were found: flagella, fimbria, and vesicles. Flagella were found both in the material of cultures maintained in vitro and in each native sample of the gastric mucosa. SEM images suggest the involvement of flagella in biofilm formation. On longitudinal sections of the flagellum, the outer electron-dense layer and the inner content in the form of a filament were visualized; on cross sections, the flagellum looked like an annular structure with a centrally located point accumulation of electron-dense matter. Paradoxically, the H. pylori forms with a defective cell wall also possessed flagella. Freely located flagellar sheaths without central filament were often found in vitro only. Fimbriae were found exclusively in negatively contrasted pure bacterial cultures material. In addition, vesicles detaching from the surface of bacterial cells were found both in the material of aging H. pylori pure cultures and in native samples of the gastric mucosa under CG and UD. A small part of the vesicles retains their connection with the cell wall, while detached vesicles are present in excess in the surrounding space. Massive detachment of vesicles leads to the formation of spheroplasts, devoid of an outer membrane. Conclusion: H. pylori has a representative set of surface structures that play an important role in the onset and development of the infectious process in the gastroduodenal area.

Ultrastructure of epithallial cells and trichocyte initials in Amphiroa (Corallinales, Rhodophyta), and possible systematic value of trichocyte development in corallines

ABSTRACT To better understand the dynamics of the coralline algal thallus surface, scanning and transmission electron microscopy were used to examine the structure and development of epithallial cells and trichocyte initials in three species of Amphiroa. Epithallial cells possessed several distinctive organic wall layers. A densely fibrillar, moderately electron-dense layer completely surrounded each epithallial cell. Inward of this layer on the distal cell face, irregular deposits of wall material projected into the cell lumen. Outward on the distal cell surface, an electron-dense layer tapered from a central conical projection. This cone of distal wall material originated before the epithallial cell that ultimately bore it, having been deposited by an initial cell to sever its connection with a senescing epithallial cell in advance of epithallial cell replacement. This wall feature provided an indication of epithallial cell regeneration. Trichocyte initials were present beneath the layer of epithallial cells. The calcified sidewall of the epithallial cell overlaying the trichocyte chamber contained a channel that terminated in a pore through which the shaft of a trichocyte could pass. Lateral to the trichocyte initial, uncalcified walls still bearing pit plugs once shared by the initial cell and multiple generations of lost and regenerated trichocytes were compressed against the side of the trichocyte chamber. A single section of one trichocyte chamber showed 17 remnant pit plugs, indicating a high frequency of trichocyte turnover. Comparisons drawn from the published literature suggest that trichocyte development has the potential to serve as a source of systematic characters for coralline algae.

Exumbrellar Surface of Jellyfish: A Comparative Fine Structure Study with Remarks on Surface Reflectance

The exumbrellar surfaces of six pelagic cnidarians from three classes were ultra-structurally compared to reveal their structural diversity in relation to their gelatinous, transparent bodies. We examined two hydrozoans (Diphyes chamissonis and Colobonema sericeum), a cubozoan (Chironex yamaguchii), and three scyphozoans (Atolla vanhöffeni, Aurelia coerulea, and Mastigias papua). The exumbrellar surfaces of the mesoglea in D. chamissonis, Ch. yamaguchii, Au. coerulea, and M. papua were covered with a simple epidermis; the shapes of the epidermal cells were remarkably different among the species. The epidermal cells of Ch. yamaguchii and M. papua possessed an array of microvilli on the apical side. The array possibly reduced light reflectance and provided some other surface properties, as seen for the cuticular nipple array in tunicates, considering the length, width, and pitch of the microvilli. The reduction of light reflectance on the array of microvilli was supported by the simulation with rigorous coupled wave analysis (RCWA). Microvilli were sparse and did not form an array in metephyrae of Au. coerulea. The mesoglea matrix beneath the basal side of the epidermis was loose in all of the species. The exumbrellar side of the mesoglea was exposed only in the mesopelagic species, At. vanhöffeni and Co. sericeum, and electron-dense layer(s) covered the surface of the mesoglea. It is uncertain whether the exumbrellar epidermis is absent in these species or the epidermal cells are completely exfoliated during the sampling and handling processes. In the latter case, the electron-dense layer(s) on the mesoglea surface might originally underlie the epidermis.

Structural colours in diverse Mesozoic insects.

Structural colours, nature's most pure and intense colours, originate when light is scattered via nanoscale modulations of the refractive index. Original colours in fossils illuminate the ecological interactions among extinct organisms and functional evolution of colours. Here, we report multiple examples of vivid metallic colours in diverse insects from mid-Cretaceous amber. Scanning and transmission electron microscopy revealed a smooth outer surface and five alternating electron-dense and electron-lucent layers in the epicuticle of a fossil wasp, suggesting that multilayer reflectors, the most common biophotonic nanostructure in animals and even plants, are responsible for the exceptional preservation of colour in amber fossils. Based on theoretical modelling of the reflectance spectra, a reflective peak of wavelength of 514 nm was calculated, corresponding to the bluish-green colour observed under white light. The green to blue structural colours in fossil wasps, beetles and a fly most likely functioned as camouflage, although other functions such as thermoregulation cannot be ruled out. This discovery not only provides critical evidence of evolution of structural colours in arthropods, but also sheds light on the preservation potential of nanostructures of ancient animals through geological time.

Ultrastructure of the fertilized egg envelopes in Ancistrus cirrhosus, Loricariidae, Teleostei

We examined the morphology of fertilized egg and ultrastructures of fertilized egg envelopes of Ancistrus cirrhosus belong to Loricariidae using light and electron microscopes. The fertilized eggs formed a mass on the spawning place and were yellowish, spherical, non-transparent, demersal, adhesive, and a narrow perivitelline space. But, the adhesiveness of fertilized eggs was disappeared after spawning excluding contact parts. The micropyle with funnel shape was surrounded by 15–19 furrow lines of egg envelope in a spoke-like pattern. The outer surface of egg envelope has smooth side and inner surface of egg envelope was rough with grooves. Also, the total thickness of the fertilized egg envelope was about 32.58 ± 0.85 μm (n = 20), and the fertilized egg envelope consisted of three layers, an outer adhesive electron-dense layer, a middle layer with low electron density and an inner electron-dense layer with grooves in counter structure from other most teleost. Collectively, these morphological characteristics and adhesive property of fertilized egg, and ultrastructures of micropyle, outer surface, and section of fertilized egg envelope are showed species specificity.

Cutaneous T-Cell Lymphoma (CTCL) Cell Line-Derived Extracellular Vesicles Contain HERV-W-Encoded Fusogenic Syncytin-1

Cutaneous T-Cell Lymphoma (CTCL) Cell Line-Derived Extracellular Vesicles Contain HERV-W-Encoded Fusogenic Syncytin-1

Evidence of a Cellulosic Layer in Pandoravirus massiliensis Tegument and the Mystery of the Genetic Support of Its Biosynthesis

Pandoraviruses are giant viruses of ameba with 1 μm-long virions. They have an ovoid morphology and are surrounded by a tegument-like structure lacking any capsid protein nor any gene encoding a capsid protein. In this work, we studied the ultrastructure of the tegument surrounding Pandoravirus massiliensis virions and noticed that this tegument is composed of a peripheral sugar layer, an electron-dense membrane, and a thick electron-dense layer consisting in several tubules arranged in a helicoidal structure resembling that of cellulose. Pandoravirus massiliensis particles were stained by Calcofluor white, a fluorescent dye of cellulose, and the enzymatic treatment of particles by cellulase showed the degradation of the viral tegument. We first hypothesized that the cellulose tegument could be synthesized by enzymes encoded by the virus. Bioinformatic analyses revealed in P. massiliensis, a candidate gene encoding a putative cellulose synthase, with a homology with the BcsA domain, one of the catalytic subunits of the bacterial cellulose synthase, but with a low level of homology. This gene was transcribed during the replicative cycle of P. massiliensis, but several arguments run counter to this hypothesis. Indeed, even if this gene is present in other pandoraviruses, the one of the strain studied is the only one to have this BcsA domain and no other enzymes involved in the synthesis of cellulose could be detected, although we cannot rule out that such genes could have been undetected among the large proportion of Orfans of pandoraviruses. As an alternative, we investigated whether P. massiliensis could divert the cellulose synthesis machinery of the ameba to its own account. Indeed, contrary to what is observed in the case of infections with other giant viruses such as mimiviruses, it appears that the transcription of the ameba, at least for the cellulose synthase gene, continues throughout the growth phase of particles of P. massiliensis. Finally, we believe that this scenario is more plausible. If confirmed, it could be a unique mechanism in the virosphere.

Ultrastructure of the fertilized egg envelopes in Hemigrammus erythrozonus, Characidae, Teleostei

We examined the morphology and ultrastructures of fertilized egg envelopes of glowlight tetra (Hemigrammus erythrozonus) belong to Characidae using light and electron microscopes.The fertilized eggs were spherical, transparent, demersal, adhesive, and have no oil droplet. The perivitelline space was well-developed and the micropyle was surrounded by 15–20 uplifted lines of egg envelope in a spoke like pattern. The outer surface of egg envelope was rough side with grooves. Also, the total thickness of the fertilized egg envelope was about 2.1–2.3 μm, and the fertilized egg envelope consisted of two layers, an outer adhesive electron-dense layer with grooves and three feather-like lamellae layers. Collectively, these morphological characteristics of fertilized egg and micropyle with spoke-like structure showed family Characidae specificity, and ultrastructures of outer surface and section of fertilized egg envelope showed species specificity.

Cell wall dynamics under conditions of diffuse growth in the thick-walled cortical tissue (prosoplectenchyma) of Ramalina usnea

AbstractA recent field study indicated that thalli of the beard lichen Ramalina usnea undergo diffuse (“intercalary”) growth throughout their length. We examined thallus sections with TEM to better understand how the highly thickened cell walls of the prosoplectenchymatous cortex behave under conditions of continued expansion. Cell protoplasts were surrounded by massive accumulations of structured electron-dense wall layers interspersed with amorphous, electron-transparent substances, visible as concentric rings in transverse section. Nearest the protoplast, electron-dense wall layers were distinct and more or less alternated with irregular deposits of electron-transparent material. With increasing distance from the protoplast, the electron-dense wall layers were increasingly disrupted and intermixed among the electron-transparent materials. New cell branches grew through the accumulated wall materials, interrupting the layers they penetrated while producing their own concentric wall layers. The differing amounts of cell wall material accumulated was further indication of the different relative ages of such neighbouring cells. These observations suggest that cell walls are disrupted by diffuse tissue expansion and continually replaced by new walls and wall materials deposited to their interior at the interface with the protoplast. This pattern of development, documented previously in R. menziesii and U. longissima, suggests that component cells of lichen prosoplectenchyma behave quite differently from those of diffusely expanding filaments studied in non-lichen-forming fungi, where a single, discrete cell wall is maintained throughout growth.

CNT-Based Label-Free Electrochemical Sensing of Native DNA with Allele Single Nucleotide Polymorphism

A label-free high-performance electrochemical sensing of single nucleotide polymorphism in native genomic DNA samples from cancer tissues, in oncogene-specific complementary DNA and in amplicons has been carried out on bundles of few-walled carboxylated carbon nanotubes, surface of which was coated with electron-dense layer of probe DNA. High selectivity and sensitivity of the novel DNA-nanosensor are ensured by the following features. Firstly, a complementary-hybridization signal is enhanced by resonance between plasmons in carbon nanotubes and dipole oscillations of hydrated nucleic acids located in near-electrode Helmholtz double layer of the impedance sensor. Secondly, a decoration of carbon nanotubes by adhered metal atoms in a high-spin state leads to Fermi level stabilization for the carbon nanotube bundles.