Pleuralins are involved in theca differentiation in the diatom Cylindrotheca fusiformis

Diatom cells are encased within a silica-based cell wall (frustule) that serves as armour-like protection for the enclosed protoplast. Maintaining the integrity of the frustule requires a precise coupling between the biogenesis of new frustule components and the cell cycle. Thus far, the molecular mechanisms by which this coupling is achieved are unknown. This study demonstrates that pleuralins (formerly HEPs), a previously characterized family of diatom cell wall proteins, are involved in cell cycle-dependent frustule development. The frustule is made up of two, overlapping half-shells termed the epitheca and hypotheca. Both thecae are morphologically identical, yet immunolocalisation with anti-pleuralin antibodies demonstrates that their protein composition is clearly different. During interphase, pleuralins are associated only with the epitheca, where they are confined to the inner surface of the terminal elements (pleural bands) in the region of overlap with the hypotheca. At cell division, pleuralins also become associated with the newly formed pleural bands of the hypotheca. Remarkably, this process is concomitant with the functional conversion of the parental hypotheca into the epitheca of one of the progeny cells. These results indicate that developmentally controlled association of pleuralins with the frustule is involved in hypotheca-epitheca differentiation, which is a crucial process to ensure proper frustule development.     

THE POLYMORPHIC DIATOM PHAEODACTYLUM TRICORNUTUM: ULTRASTRUCTURE OF ITS MORPHOTYPES1,2

The ultrastructure of the oval, fusiform and triradiate morphotypes of Phaeodactylum tricornutum Bohlin is described. The organization and structure of the cytoplasmic organelles is similar in all three morphotypes, except that the vacuoles occupy the extra volume created by the arms of the fusiform and triradiate cells. The frustule in fusiform and triradiate cells is organic; in the oval type it may be organic or one of the valves may have a silica frustule surrounded by an organic wall. In all cells, the organic cell wall has up to 10 silica bands (13 nm wide) embedded in its surface in the girdle region, lacks girdle bands, and has an outer corrugated cell wall layer, except in the girdle region. Cell division, organic wall formation and silica deposition are described in detail. Four types of oval cells are also described. The relation to other diatoms is discussed.     

Filament formation in the diatomSkeletonema costatum

Summary Skeletonema costatum consists of cells joined by open gutter-like connecting spines (strutted tubuli) which form from the margin of the valve face. The intercellular spaces occupied by tubuli are alternately enclosed by finely perforate bands of wall material. The intercellular bands are in the form of overlapping, open ended cylinders attached to the epitheca in the region of the cell girdle. A model is proposed for filament formation explaining the origin of alternating walled and unwalled intercellular spaces.     

A STRESS‐INDUCED PROTEIN ASSOCIATED WITH THE GIRDLE BAND REGION OF THE DIATOM THALASSIOSIRA PSEUDONANA (BACILLARIOPHYTA)1

We report the characterization of a cell‐surface protein isolated from the centric diatom Thalassiosira pseudonana Hasle and Heimdal. This protein has an apparent molecular weight of 150 kDa, is highly acidic, and is intimately associated with the cell wall. Although originally identified in cells experiencing copper toxicity, it is also induced by silicon and iron limitation but not by phosphate or nitrate limitation. Using immunofluorescence techniques, the 150‐kDa protein was localized to the girdle band region and covered the elongated girdle band region of morphologically aberrant cells suffering from copper toxicity. Although having biochemical similarities to girdle band associated proteins identified in pennate diatoms known as pleuralins, the 150‐kDa protein is not a sequence homolog and is predicted to have a number of unique features, such as chitin binding domains and a possible RGD cell attachment motif. Results presented here suggest that this protein is normally cell cycle regulated and may be involved in stabilizing cells during the division process.     

Gametogenesis and auxospore development in actinocyclus (bacillariophyta)

cGametogenesis and auxospore development have been studied in detail in surprisingly few centric diatoms. We studied the development of sperm, eggs and auxospores in Actinocyclus sp., a radially symmetrical freshwater diatom collected from Japan, using LM and electron microscopy of living cultures and thin sections. Actinocyclus represents a deep branch of the 'radial centric' diatoms and should therefore contribute useful insights into the evolution of sexual reproduction in diatoms. Spermatogenesis was examined by LM and SEM and involved the formation of two spermatogonia (sperm mother-cells) in each spermatogonangium through an equal mitotic division. The spermatogonia produced a reduced 'lid' valve, resembling a large flat scale with irregular radial thickenings. Sperm formation was merogenous, producing four sperm per spermatogonium, which were released by dehiscence of the 'lid' valve. The sperm were spindle-shaped with numerous surface globules and, as usual for diatoms, the single anterior flagellum bore mastigonemes. One egg cell was produced per oogonium. Immature eggs produced a thin layer of circular silica scales before fertilization, while the eggs were still contained within the oogonium. Sperm were attracted in large numbers to each egg and were apparently able to contact the egg surface via a gap formed between the long hypotheca and shorter epitheca of the oogonium and a small underlying hole in the scale-case. Auxospores expanded isodiametrically and many new scales were added to its envelope during expansion. Finally, new slightly-domed initial valves were produced at right angles to the oogonium axis, after a strong contraction of the cell away from the auxospore wall. At different stages, Golgi bodies were associated with chloroplasts or mitochondria, contrasting with the constancy of Golgi-ER-mitochondrion (G-ER-M) units in some other centric diatoms, which has been suggested to have phylogenetic significance. Electron-dense bodies in the vacuole of Actinocyclus are probably acidocalcisomes containing polyphosphate.     

Pattern morphogenesis in cell walls of diatoms and pollen grains: a comparison

Summary Mechanisms acting in pattern morphogenesis in the cell walls of two distant groups of plants, pollen of spermatophytes and diatoms, are compared in order to discriminate common principles from plant group- and wall material-specific features. The exinous wall in pollen is sequentially deposited on the exocellular side of the plasmalemma, while the siliceous wall in diatoms is formed intracellularly within an expanding silica deposition vesicle (SDV) which is attached to the internal face of the plasmalemma. Two levels of patterning occur in diatom and pollen walls: the overall pattern stabilises the wall mechanically and is apparently initiated in both groups by the parent cell, and a microtubule-dependent aperture and portula pattern created by the new mitotic (diatoms) or meiotic (pollen) cells. The parent wall in diatoms, and also the callosic wall in microspores, functions as anchor surfaces for transient, species-specific patterned adhesions of the plasmalemma to these walls, involved in pattern and shape creation. Patterned adhesion and exocytosis is blocked in pollen walls where the plasmalemma is shielded by the endoplasmic reticulum at the sites of the future apertures. In diatoms, wall patterning is uncoupled from the formation of a siliceous wall per se when the SDV and its wall is formed without contact to the the plasmalemma. Conversely, a blue-print pattern laid out in advance along the plasmalemma can be found in several diatoms. This highlights the key function of the plasmalemma and its associated membrane skeleton (fibrous lamina), and its orchestrated co-operation with elements of the radial filamentous cytoskeleton (actin?) in pattern formation. The role of microtubules during generation of the overall pattern may be primarily a transport and stabilizing function. Auxiliary organelles (spacer vesicles, endoplasmic reticulum, mitochondria) involved in diatoms for shaping the SDV, and a mechanism adhering and disconnecting this SDV together with spacer organelles in a species-specifically controlled sequence to and from the plasmalemma, are unnecessary for pollen wall patterning. The precise positioning of the portula pattern in diatom walls is discussed with respect to their role as permanent anchors of the cytoplasm to its wall, and in providing spatial information for nucelar migration and the next cell division, whereas apertures in pollen are for single use only.Abbreviations AF actin filaments - C/Ca callose - CF cleavage furrow - cPL cleavage plasmalemma - DV dense vesicles - ER endoplasmic reticulum - ET epitheca - HT hypotheca - mPL folded plasmalemma - MT microtubules - MTOC microtubule organising centre - PEV primexine (matrix) vesicles - PL plasmalemma - SDV silica deposition vesicle - Si silica - SL SDV-membrane - SPV spacer vesicles Dedicated to Prof. Dr. Dr. h.c. Eberhard Schnepf on the occasion of his retirement     

Studies on the biochemistry and fine structure of silicia shell formation in diatoms VII. Sequential cell wall development in the pennateNavicula pelliculosa

Summary The development of the wall of synchronized culture ofN. pelliculosa is described. The first step, modification of the 3-2 configuration of the girdle bands of the wall during interphase, occurs immediately before mitotic division by the addition of a third girdl band to the hypotheca. Following cytokenesis, the new valve is initiated when a primary central band is formed within a silica deposition vesicle. This band extends the length of the cell and contains a central nodule. Secondary arms extend from the central nodule, join with extensions of the primary central band, and constitute the raphe rib. Mounds or knolls are formed on the central nodule and disappear as the valve matures. Transapical ribs appear on both the primary central band and secondary arms, and cross extensions join to form the sieve plate areas. The wall appears to be released by a joining of the inner silicalemma and the plasmalemma. An organic coat covers the newly released wall. Two girdle bands are formed and released sequentially.     

Roscoffia minor sp. nov. (Peridiniales, Dinophyceae): A new, sand-dwelling, armored dinoflagellate from Hokkaido, Japan

A new, sand-dwelling, armored dinoflagellate, Roscoffia minor sp. nov., is described from Ishikari beach, Hokkaido, Japan. The dinoflagellate has been collected from sand samples taken both near the water's edge and further upshore (25 m from the water's edge at a depth of 1 m), indicating that it is a true sand-dwelling species. Roscoffia minor is heterotrophic and lacks both a chloroplast and an eye-spot. The cell consists of a flattened cap-shaped epitheca and a large hemispheroidal hypotheca, and it is quite different from cells of the typical armored dinoflagellates. The thecal plate formula is: Po, 3′, la, 5″, 3c, 3s, 5″, 1″″. Its distinct cell shape and the thecal plate arrangement indicate affinity to the monotypic genus Roscoffia. Roscoffia minor is distinguished from Roscoffia capitata, the type species, by its smaller size and the possession of a finger-like apical projection. The thecal arrangement of the epitheca is similar to those of the members of the family Podolampaceae, while the hypothecal arrangement is the same as that of members of the subfamily Diplopsalioideae (family Congruentidiaceae). The organism seems to be positioned somewhere intermediate between these two families, but the family to which this dinoflagellate should be affiliated could not be determined.     

MORPHOLOGY AND LIFE CYCLE EVENTS IN PYROPHACUS STEINII (SCHILLER) WALL ET DALE (DINOPHYCEAE)

Cells of Pyrophacus steinii (Schiller) Wall et Dale are round and lens shaped and have an anteroposteriorly compressed theca. The epitheca has a truncated, conical horn and a hexagonally shaped apical pore plate with two arched slits positioned off center. The cingulum is equatorial, narrow, and deep. The hypotheca is flat. The sulcus is narrow, slightly curved, and recessed and does not reach the cell's antapex. The plate formula in these specimens of P. steinii is Po, 8', Oa, 13", 13C, 12"', 3p, 3"", and 8S with a difference in the number of precingular (13") and postcingular (12"') plates. No additional posterior intercalary plates were present (Oap). Pregametic stages of P. steinii were observed during cell division via binary fission, with formation of two cells and multiple division with formation of four and eight cells. These newly formed cells were pale in color and were enclosed in double-layered hyaline membrane. Gametes with gymnodinoid morphology were observed within the parental cells. Planozygotes are large and round and enclosed in double-layered hyaline membrane. Mature cell forms are brown with a microgranular cytoplasm, storage bodies, and a red accumulation body. The hypnozygote exhibits triple-layered hyaline membrane, irregularly shaped and comparable with bulbous processes of Tuberculodinium vancampoae Rossigol resting cysts. Division within a hypnocyst of P. steinii involves shedding the parental theca and the development and emergence of two daughter cells with the size and morphology of pregametic cells.     

VALVE AND BAND MORPHOLOGY OF SOME FRESHWATER DIATOMS. IV. OUTER SURFACE MUCILAGE OF NAVICULA CONFERVACEA VAR. CONFERVACEA1

The development of the mucilage on the outer surface of Navicula confervacea (Kütz.) Grun., a raphed, filamentous diatom, was studied with scanning electron microscopy. This nonstructural cell wall material, present on the surface after critical-point drying and absent after acid cleaning, was of two types: strands and papillae. Strands were associated with the raphe system, areolae, elongated pores of the mantle, and all girdle sutures. Organic papillae were a common feature of valves, valvo-copulae and pleurae, but their origin and distribution could not be explained since they often occurred between the obvious openings in the frustule. Strands from the raphe and areolae may function in attaching terminal cells to a substrate and adjacent cells to each other. Other strands of the girdle arise from sutures during cell enlargement and continue to lengthen and intertwine until the individual frustules within a filament are obscured. Strands from sutures might originate from the advalvar row of pores of the girdle bands since these pores lie along the suture, but direct observation of this was not made. Secretion between, the bands also cannot be ruled out. Although mucilaginous papillae may sometimes occur at random on the entire surface of frustules, there is also a distinct, narrow multiseriate row of them around the edge of valves without marginal spines.     

MECHANISM OF GAMETE FUSION IN DINOPHYSIS FORTII (DINOPHYCEAE,DINOPHYTA): LIGHT MICROSCOPIC AND ULTRASTRUCTURAL OBSERVATIONS1

A variety of studies have examined the sexual life cycle of species belonging to the genus Dinophysis Ehrenberg. Here, we used TEM to investigate the mechanism of cellular fusion during the sexual life cycle in Dinophysis fortii Pavillard. We observed that fusion always occurred between a normal‐sized cell and a small cell following attachment of their ventral margins. After cell attachment, the small cell moved toward the epitheca of the normal‐sized cell, and the cingular and sulcal lists of the small cell shrunk or were almost lost. The epitheca of the normal‐sized cell then opened between the cingulum plates and the upper cingular list, after which the small cell was gradually engulfed. This is the first ultrastructural observation in a dinoflagellate of a larger cell opening its epitheca to engulf the smaller gamete. In another case, the normal‐sized cell did not open the epitheca, the cell wall of the attached small cell underwent extensive extracellular digestion, and the cytoplasm appeared to flow into the normal‐sized cell via the periflagellar area. Inflow of the nucleus was not observed in this case, suggesting that it represented a failure of sexual fusion. In both cases, membranous separations between the cytoplasm of the two cells were not observed. At the beginning of the fusion process, the nucleus of the small cell was substantially deformed. The planozygote, formed upon completion of sexual fusion, sometimes had two longitudinal flagella, but was identical to a normal vegetative cell in its cellular shape, as already mentioned by previous authors.     

Frustule morphogenesis of raphid pennate diatom <Emphasis Type="Italic">Encyonema ventricosum</Emphasis> (Agardh) Grunow

Diatoms stand out among other microalgae due to the high diversity of species-specific silica frustules whose components (valves and girdle bands) are formed within the cell in special organelles called silica deposition vesicles (SDVs). Research on cell structure and morphogenesis of frustule elements in diatoms of different taxonomic groups has been carried out since the 1950s but is still relevant today. Here, cytological features and valve morphogenesis in the freshwater raphid pennate diatom Encyonema ventricosum (Agardh) Grunow have been studied using light and transmission electron microscopy of cleaned frustules and ultrathin sections of cells, and scanning electron and atomic force microscopy of the frustule surface. Data have been obtained on chloroplast structure: the pyrenoid is spherical, penetrated by a lamella (a stack of two thylakoids); the girdle lamella consists of several short lamellae. The basic stages of frustule morphogenesis characteristic of raphid pennate diatoms have been traced, with the presence of cytoskeletal elements near SDVs being observed throughout this process. Degradation of the plasmalemma and silicalemma is shown to take place when the newly formed valve is released into the space between sister cells. The role of vesicular transport and exocytosis in the gliding of pennate diatoms is discussed.     

POLARELLA GLACIALIS, GEN. NOV., SP. NOV. (DINOPHYCEAE): SUESSIACEAE ARE STILL ALIVE!

The culture CCMP 1383, obtained from sea-ice brine collected in McMurdo Sound (Ross Sea, Antarctica), is a small gymnodinioid dinoflagellate. This species is very abundant in the upper land-fast sea ice, where it can both grow and overwinter as a spiny encysted stage. The motile vegetative stage and the cyst produced in the culture were studied by scanning electron microscopy (SEM) and transmission electron micrscopy (TEM). The amphiesma of the vegetative cells is constituted by thin vesicles that are organized into nine latitudinal series of plates: three in the epitheca, two in the cingulum, and four in the hypotheca. The same tabulation is reflected in the cyst wall by acicular processes arising from the center of paraplates, with the exception of the paracingulum, in which acicular processess are absent. On the basis of the peculiar plate pattern of this dinoflagellate, we establish the new genus Polarella and the new species Polarella glacialis (family Suessiaceae, order Suessiales). This species has a remarkable similarity with fossil Suessiaceae cysts dating back to the Triassic and Jurassic and represents, up to now, the only extant member of the subfamily Suessiaceae. Phylogenetic analysis based on the small-subunit ribosomal RNA gene confirmed the placement of this species in the order Suessiales and its close relationship with the genus Symbiodinium Freudenthal.     

Micro‐photoluminescence of single living diatom cells

Diatoms are single‐celled microalgae that possess a nanostructured, porous biosilica shell called a frustule. This study characterized the micro‐photoluminescence (μ‐PL) emission of single living cells of the photosynthetic marine diatom Thalassiosira pseudonana in response to UV laser irradiation at 325 nm using a confocal Raman microscope. The photoluminescence (PL) spectrum had two primary peaks, one centered at 500–510 nm, which was attributed to the frustule biosilica, and a second peak at 680 nm, which was attributed to auto‐fluorescence of photosynthetic pigments. The portion of the μ‐PL emission spectrum associated with biosilica frustule in the single living diatom cell was similar to that from single biosilica frustules isolated from these diatom cells. The PL emission by the biosilica frustule in the living cell emerged only after cells were cultivated to silicon depletion. The discovery of the discovery of PL emission by the frustule biosilica within a single living diatom itself, not just its isolated frustule, opens up future possibilities for living biosensor applications, where the interaction of diatom cells with other molecules can be probed by μ‐PL spectroscopy. Copyright © 2016 John Wiley & Sons, Ltd.     

NANOSTRUCTURE OF THE DIATOM FRUSTULE AS REVEALED BY ATOMIC FORCE AND SCANNING ELECTRON MICROSCOPY

The cell wall (frustule) of the freshwater diatom Pinnularia viridis (Nitzsch) Ehrenberg is composed of an assembly of highly silicified components and associated organic layers. We used atomic force microscopy (AFM) to investigate the nanostructure and relationship between the outermost surface organics and the siliceous frustule components of live diatoms under natural hydrated conditions. Contact mode AFM imaging revealed that the walls were coated in a thick mucilaginous material that was interrupted only in the vicinity of the raphe fissure. Analysis of this mucilage by force mode AFM demonstrated it to be a nonadhesive, soft, and compressible material. Application of greater force to the sample during repeated scanning enabled the mucilage to be swept from the hard underlying siliceous components and piled into columns on either side of the scan area by the scanning action of the tip. The mucilage columns remained intact for several hours without dissolving or settling back onto the cleaned valve surface, thereby revealing a cohesiveness that suggested a degree of cross-linking. The hard silicified surfaces of the diatom frustule appeared to be relatively smooth when living cells were imaged by AFM or when field-emission SEM was used to image chemically cleaned walls. AFM analysis of P. viridis frustules cleaved in cross-section revealed the nanostructure of the valve silica to be composed of a conglomerate of packed silica spheres that were 44.8 ± 0.7 nm in diameter. The silica spheres that comprised the girdle band biosilica were 40.3 ± 0.8 nm in diameter. Analysis of another heavily silicified diatom, Hantzschia amphioxys (Ehrenberg) Grunow, showed that the valve biosilica was composed of packed silica spheres that were 37.1 ± 1.4 nm and that silica particles from the girdle bands were 38.1 ± 0.5 nm. These results showed little variation in the size range of the silica particles within a particular frustule component (valve or girdle band), but there may be differences in particle size between these components within a diatom frustule and significant differences are found between species.     

Dissection of the frustules of the diatom Synedra acus under the action of picosecond impulses of submillimeter laser irradiation

Diatom algae realize highly intriguing processes of biosynthesis of siliceous structures in living cells under moderate conditions. Investigation of diatom physiology is complicated by frustule (siliceous exoskeleton). Frustules consist of valves and girdle bands which are adhered to each other by means of organic substances. Removal of the frustule from the lipid membrane of diatom cells would open new possibilities for study of silicon metabolism in diatoms. We found that submillimeter laser irradiation produced by a free-electron laser causes splitting of diatom frustules without destruction of cell content. This finding opens the way to direct study of diatom cell membrane and to isolation of cell organelles, including silica deposition vesicles. We suppose that the dissection action of the submillimeter irradiation results from unusual ultrasonic waves produced by the short (30–100 ps) but high-power (1 MW) terahertz laser impulses at 5.6 MHz frequency.     

Morphology and molecular phylogeny of the benthic dinoflagellates (Dinophyceae,Peridiniales) Amphidiniopsis crumena n. sp. and Amphidiniopsis nileribanjensis n. sp.

Amphidiniopsis is a benthic, heterotrophic and thecate dinoflagellate genus that has a smaller epitheca and larger hypotheca. The genus contains 24 described species, but is considered to be polyphyletic based on morphological characters and molecular phylogenetics. In this study, two new species were discovered from two distant sampling localities, Amphidiniopsis crumena sp. nov. from Japan, and Amphidiniopsis nileribanjensis sp. nov., from Australia. These species have a uniquely shaped, additional second postcingular plate. Both species are dorsoventrally flattened, an apical hook is present, and have six postcingular plates. The plate formula is: APC 4′ 3a 7″ ?C 4?S 6″′ 2″″. The cells of these species were examined with LM and SEM, and molecular phylogenic analyses were performed using 18S and 28S rDNA. These species are distinguished by the presence of spines on the hypotheca and touching of the sixth postcingular plate and the anterior sulcal plate. Their shape and disposition of several thecal plates also differ. Molecular phylogenetic analyses showed that the two new species formed a monophyletic clade and did not belong to any morphogroup proposed by previous studies. Considering the morphological features and the molecular phylogenetic results, a new morphogroup is proposed, Amphidiniopsis morphogroup VI (‘crumena group’).     

Amphidiniopsis uroensis sp. nov. and Amphidiniopsis pectinaria sp. nov. (Dinophyceae): Two new benthic dinoflage llates from Japan

Two new armoured, heterotrophic sand‐dwelling marine dinoflagellates, Amphidiniopsis uroensis Toriumi, Yoshimatsu et Dodge sp. nov. and Amphidiniopsis pectinaria Toriumi, Yoshimatsu et Dodge sp. nov. were collected from Japanese sandy beaches, and their morphological features observed by light microscopy and scanning electron microscopy (SEM). The cell size of A. uroensis is 28–31 μm in length and 23–28 μm in width. The plate formula is Po 3′, 3a, 6″, 3c, 4s (+1 acc.), 5″′, 2″″. The thecal surface is ornamented with small processes, pores and spines, however, the surface of plate 2a is smooth. The epitheca possesses a narrow ridge that is extended along on the suture between 1′ and 3′. Plate 1″ connects with the right sulcal (Sd) and right sulcal accessory (Sda) plates, so the cingulum is incomplete. A nucleus is situated in the central part of the cell. There are a few small spines at the antapex. There are no stigma or chloroplasts. Amphidiniopsis pectinaria cells are 33–40 urn in length and 29–35 μm in width. The plate formula is Po 4′, 3a, 7″, 3c, 4s (+1 acc.), 5″′, 2″″. Plate 1″ connects directly with Sd and Sda plates, so the cingulum is incomplete. The thecal surface is ornamented with small processes, spines and pores. The epitheca is provided with a narrow ridge that is extended along on the suture between plates 1′, 4′ and 7″. The ornamentation on the antapical plates is unique. It is arranged in 10 straight rows on the hypotheca; each row has a strong spine at its posterior end. In addition, there is a long spine at the antapex. There are no stigma or chloroplasts. A nucleus is located in the central part of the cell.     

两种纤毛虫营养细胞和休眠细胞蛋白组成的比较分析

应用生化抽提和SDS-PAGE方法显示,膜状急纤虫(Tachysoma pellionella)的营养细胞含38条蛋白谱带,休眠细胞含29条蛋白谱带,两者共有谱带为26条,特有谱带各为12条和3条,相似度为77.6%;休眠细胞的包囊壁含22条蛋白谱带,细胞脱包囊后残留的包囊壁含15条蛋白谱带,两者共有谱带为14条,特有谱带各为8条和1条,相似度为76%。包囊游仆虫(Euplotes encysticus)的营养细胞和休眠细胞均含23条蛋白谱带,两者共有谱带为19条,特有谱带各为4条,相似度为82.6%;休眠细胞的包囊壁和细胞脱包囊后残留的包囊壁均含20条蛋白谱带,两者共有谱带为19条,特有谱带均为1条,相似度为95%。结果表明,两种纤毛虫的营养细胞向休眠细胞转化过程中,细胞结构的主要蛋白质成分发生了明显变化,这些变化与细胞在不同生理状态下结构的分化及其生命活动特征相关。形成“毛基体吸收型包囊”的急纤虫与形成“毛基体非吸收型包囊”的游仆虫相比较,前者营养期和休眠期细胞蛋白组成有更明显的差异,这可能与其细胞结构更大程度的脱分化有关;根据纤毛虫休眠细胞的包囊壁和细胞脱包囊后残留的包囊壁两者蛋白组成的差异推测,前者包囊壁可能含有与休眠细胞生命活动相联系的“活性”成分。     

Photoluminescence shift in frustules of two pennate diatoms and nanostructural changes to their pores

The diatom silicified cell wall (frustule) contains pore arrays at the micro‐ to nanometer scale that display efficient luminescence within the visible spectrum. Morphometric analysis of the size and arrangement of pores was conducted to observe whether any correlation exists with the photoluminescence (PL) of two diatom species of different ages. UV‐excited PL displays four clearly defined peaks within the blue‐region spectrum, on top of the broad PL characteristic of synthetic porous silicon dioxide, recorded for reference and where discrete lines are absent. A set of shifted emission lines was observed when diatom cultures reached adulthood. These discrete line shifts correlate with structural changes observed in adult frustules: reduction in pore diameter; appearance of pores within pores, 10 nm in size; an increase in the gap distance between stria; and the deposition of several girdle bands with a concomitant increase in the diatom waist length, as well as the appearance of pores on such bands. Destruction of the pores results in the disappearance of all discrete emission lines. The PL shifts are correlated with a substantial increment of Si–OH groups adsorbed on the frustule surface, as revealed by Fourier transform infrared spectroscopy. Copyright © 2014 John Wiley & Sons, Ltd.