Interaction between bacteria and the domoic-acid-producing diatom Pseudo-nitzschia multiseries (Hasle) Hasle; can bacteria produce domoic acid autonomously?

The interaction between bacteria and phytoplankton is increasingly becoming recognised as an important factor in the physiology of toxin production and the dynamics of harmful algal blooms (HABs). Bacteria can play a direct or indirect role in the production of biotoxins once solely attributed to microalgae. Evidence implicating bacteria as an autonomous source paralytic shellfish poisoning biotoxins raises the question of autonomous bacterial toxigenesis of the neurotoxin domoic acid (DA), the cause of amnesic shellfish poisoning. Here, we examine whether the previously observed bacterial enhancement of DA production by Pseudo-nitzschia multiseries (Hasle) Hasle may be attributable to independent biotoxin production by the extra-cellular bacteria associated with this diatom. The growth and toxicity of six cultures of xenic P. multiseries clone CLN-1 were followed for 24 days. Up to day 14 (mid-stationary phase), DA production was not statistically different among culture flasks. On day 14, P. multiseries cells were removed by gentle filtration from a set of triplicate flasks, leaving the bacteria in the filtrate. Following the removal of the algal cells, DA in the filtrate ceased to increase. Instead, DA levels continuously declined. A follow-up experiment determined that this was likely caused by photodegradation rather than by bacterial degradation. We conclude that after removing P. multiseries cells, the extra-cellular bacteria remaining in the filtrate were incapable of autonomous DA toxigenesis, even in the presence of P. multiseries exudates. However, scanning electron microscopy revealed that P. multiseries cells harboured epiphytic bacteria, the importance of which can still not be ruled out in DA production.     

The effect of irradiance and irradiation time on the size of initial cells in vegetative cell enlargement of Coscinodiscus wailesii (Centrales, Bacillariophyceae) in culture

The effect of irradiance and irradiation time were examined on rates of pseudo-auxospore formation and the size of initial cells in vegetative cell enlargement of the giant diatom Coscinodiscus wailesii Gran in culture. The mean rate of pseudo-auxospore formation ranged from 25.9% to 47.8% between experimental incubation conditions. No significant difference was detected in rates among different irradiances and irradiation times, and parent cell sizes. However, the mean valve diameter of the initial cells of the diatom was affected by an interaction between the light conditions and the diameter of the parent cells. Initial cells size tended to be larger with combined conditions of higher irradiance levels and longer irradiation time. There appears to be a relationship (a steady increase, although not a straight line) between the total daily irradiance and the valve diameter of the initial cells. The mean valve diameter of initial cells from larger parent cells was significantly larger than those from smaller parent cells under the same light conditions.     

Manna scale,Trabutina mannipara (Hemprich & Ehrenberg) (Homoptera: Coccoidea: Pseudococcidae)*

Abstract. The mealybug Trabutina mannipara (Hemprich & Ehrenberg, 1829) is described and illustrated, and a neotype female selected from topotypic material collected in the Sinai Peninsula. A lectotype female is designated for Trabutina palestina Bodenheimer (1927) which is shown to be a junior synonym of T.mannipara.     

Thalassiosira pseudonana (Cyclotella nana) (Hustedt) Hasle et Heimdal (Bacillariophyceae): A genetically tractable model organism for studying diatom biology,including biological silica formation

In 2004, Thalassiosira pseudonana was the first eukaryotic marine alga to have its genome sequenced. Since then, this species has quickly emerged as a valuable model species for investigating the molecular underpinnings of essentially all aspects of diatom life, particularly bio-morphogenesis of the cell wall. An important prerequisite for the model status of T. pseudonana is the ongoing development of increasingly precise tools to study the function of gene networks and their encoded proteins in vivo. Here, we briefly review the current toolbox for genetic manipulation, highlight specific examples of its application in studying diatom metabolism, and provide a peek into the role of diatoms in the emerging field of silica biotechnology.     

The development and structure of vegetative and reproductive organs ofBinghamia californica (Rhodophyta)

Although the species has been known for more than 70 years, no published accounts have been made of the details of development of the reproductive structures ofBinghamia californica J. Ag., a member of the Rhodymeniales of limit d distribution in the eastern and western Pacific. The present studies indicate that there is a close relationship in vegetative structure and in the ontogeny of the reproductive structure toLomentaria, especially toL. hakodatensis Yendo. This study is dedicated to Professor Yositeru Nakamura on the occasion of his academic retirement.     

Productivity events of the marine diatom Thalassiosira tumida (Janisch) Hasle recorded in deglacial varves from the East Antarctic Margin

During the last deglaciation calving bay reentrants formed over several deep inner shelf basins around Antarctica as the ice sheets retreated. Marine diatoms flourished in spring and summer within the bays, providing exceptionally high silica flux rates to the basins on an annual basis. As a result, several hundred years of the late deglaciation are archived in many of these deep basins as continuously laminated diatom-rich marine sediments. The laminae are excellently preserved and offer a unique opportunity to study deglacial processes over the Antarctic shelf at very high resolution (subseasonal to seasonal at best). Annual palaeoenvironments from these sediments have been recently reconstructed. However, finer sedimentary detail is also apparent by the preservation of sublaminae of single diatom species, which represent discrete productivity events (blooms). In this paper, we focus on Thalassiosira tumida (Janisch) Hasle sublaminae preserved in the  5 m thick deglacial laminated sequence of NBP01-01 Jumbo Piston Core (JPC) 43B from Iceberg Alley ( 67°S, 63°E) on the Mac.Robertson Shelf, East Antarctic Margin. These T. tumida sublaminae are distinctive, occur several times throughout the deglacial sequence and are always preserved within summer laminae. Importantly they carry ecological and paleoceanographic information for deglacial Iceberg Alley and possibly the entire East Antarctic Margin. We describe and illustrate the T. tumida sublaminae using scanning electron microscope backscattered electron imagery of highly polished thin sections and secondary electron imagery of sublamina fracture surfaces. T. tumida sublaminae range in thickness from 0.57 to 21.07 mm (mean = 5.12; σ = 4.49) and are defined as discrete sedimentary intervals within a summer lamination where T. tumida is the dominant diatom species (abundance > 50%; but frequently > 80%) or is very abundant (abundance 40% to 49%). Based on the stratigraphic position of these sublaminae in the annual/seasonal succession and on published morphological, ecological and distributional data of living specimens in culture and in the field, we surmise an open-water, late summer bloom for T. tumida in deglacial Iceberg Alley, at sea-surface temperatures of 0 to − 1.69 °C, under low or fading light levels just prior to significant sea-ice formation. We suggest that the sublaminae formed by a combination of episodic T. tumida blooms (surface concentration), followed by rapid deposition (high flux) and optimal frustule preservation on the sea floor. Increased sublaminae frequency upcore suggests a lengthening of the summer season, while their complete cessation 43 years prior to the end of lamination deposition in outer Iceberg Alley (JPC43B) may be due to a coastward population shift.     

The effect of diet and temperature on reproductive rate in Arcella vulgaris Ehrenberg (Sarcodina: Testacida)

Summary The acceptability of bacterial, algal and fungal food cources as manifested by reproductive rate was investigated in Arcella vulgaris at 5°C intervals between 10°C-25°C. Bacteria and diets containing bacteria produced the highest rates of reproduction, a fungal diet induced the lowest rate of reproduction. On all diets reproductive rate increased with temperature up to 20°C, thereafter levelling out. Generation times were long, ranging from 64 h to 95 h, depending on diet and temperature. Consumption experiments using bacteria as food indicated that energy consumption was independent of temperature.     

Temporal and spatial changes of cellulose synthesis inClosterium acerosum (Schrank) Ehrenberg during cell growth

The amount and distribution of wall microfibril synthesis were investigated in the cell-division cycle ofClosterium acerosum. Electron-microscopic examination and a methylation analysis of alkali-extracted wall fragments showed that alkali-extracted wall was mainly composed of microfibrils and that the microfibrils ofC. acerosum were 4-linked glucans, i.e., cellulose. Cellulose synthesis was measured as incorporation of¹⁴C, fed to cells as NaHCO₃, into extracted wall fragments. Extensive cellulose synthesis was coincident with septum formation, continued for more than 6 h and then ceased. It was found by microautoradiography that cellulose synthesis after cell division was essentially restricted to the expanding new semicells. Such a restricted distribution of cellulose synthesis was maintained for more than 6 h after septum formation, i.e., for more than 2 h after the cessation of expansion; afterwards, cellulose synthesis in some, but not all, cells became extended to the old semicells, and then ceased. Considerable cellulose synthesis also took place in the band-like expanding part of non-divided cells, indicating that cell division was not necessarily required for the induction of cellulose synthesis and the latter was coupled with cell expansion. Extension of cellulose synthesis to old semicells was brought about in divided cells by treatment with 3 mM colchicine, 28 M vinblastine, 50 M isopropyl-N-phenylcarbamate or 1 M isopropyl-N(3-chlorophenyl)carbamate, indicating that microtubules are involved in the limitation of cellulose synthesis to the new semicells.Abbreviations CIPC isopropyl-N(3-chlorophenyl)carbamate - DPO 2,5-diphenyloxazole - IPC isopropyl-N-phenylcarbamate     

动物细胞培养过程中的细胞自然凋亡

细胞培养过程中的细胞自然凋亡是细胞受环境压力的影响而发生的现象。随着细胞自然凋亡的分子生物学和生物化学研究的深入,对以动物细胞产品生产为目的的细胞培养产业将产生极有价值的影响。采用DNA重组技术把预防细胞自然凋亡的基因导入细胞和在培基中加入具有抗细胞自然凋亡的化合物等手段已用于预防或减缓细胞培养过程中的细胞自然凋亡。这些技术将大大延长细胞达到饱和密度后的培养时间,从而使细胞培养系统的生产效率得以显著提高。     

The composition and structure of the benthic diatom taxocene (Bacillariophyta) near Cape Fiolent (the Crimea,the Black Sea)

For the first time in the waters of the Cape Fiolent Reserve, a high species richness of benthic diatoms was revealed on natural substrates, 290 species and infraspecific taxa (IT), belonging to 281 species, 68 genera, 32 families, 19 orders, and 3 classes. A total of 68 species and 3 genera were previously registered as new for the flora of the Black Sea; 3 species and 1 taxonomic combination were previously described as new to science, as well as 4 species that did not occur in the Black sea in the past 50 and 100 years of research. Navicula (41 species and IT), Amphora (30), Nitzschia (29), Fallacia (20), Cocconeis (17) and Diploneis (16) were the most represented genera. Only one representative was identified in each of the orders Anaulales, Ardissoneales, Thalassionematales, Rhaphoneidales, and Rhopalodiales. The diversity assessment that was carried out using taxonomic distinctness indices, TaxDI, revealed that the structure of the phylogenetic diatom tree was formed by branches with various species saturation levels and different hierarchical subordination, but with the predominance of polyspecific taxa up to at genera level. The TaxDI values (Δ⁺ = 76.71; Λ⁺ = 361.52) indicate the low evenness and high variability of the structure of the benthic diatom taxocene near Cape Fiolent.     

Differential cell enlargement and its possible implication for resupination in Lemboglossum bictoniense (Orchidaceae)

Changes in the structural features of cell populations in the pedicel of Lemboglossum bictoniense (Bateman ex. Lindley) Halbinger were examined by means of light microscopy in relation to resupination, a twisting of the pedicel through 180^o prior to flower opening. Serial sections in transverse and longitudinal planes were taken from pre-resupinate and fully resupinate pedicels of flowers from a single inflorescence, and comparisons made between the tissues. The pedicel is a prismatic cylinder flattened on three sides, producing three distinct ribS. Each rib contains one central vascular bundle enclosed by cortical parenchyma. Intervening cortical parenchyma forms flanks external to a central core of three vascular bundles, each of which is split into three distinct traces at this level. Resupination is accompanied by axial and radial expansion of cortical parenchyma. Specialized raphide-bearing cells in the cortex expand axially doubling their length in the ground parenchyma. These raphide cells are localized in the rib cortex, and their expansion is reflected in greater elongation of the ribs relative to flank areas. The extra rib length is accommodated by a lateral displacement (twisting) of the ribs around the central axis of the pedicel. Tissue distortion is reduced by cell division, expansion of intercellular spaces and a radial contraction of pith parenchyma. Raphide cell elongation could be a contributing factor in pedicel twisting. The direction of resupination may be controlled by the organization of these cells into arcs on one or other side of the rib vascular bundle.     

Elaiophores in Gomesa bifolia (Sims) M.W. Chase & N.H. Williams (Oncidiinae: Cymbidieae: Orchidaceae): structure and oil secretion

Background and Aims

Oils are an unusual floral reward in Orchidaceae, being produced by specialized glands called elaiophores. Such glands have been described in subtribe Oncidiinae for a few species. The aims of the present study were to identify the presence of elaiophores in Gomesa bifolia, to study their structure and to understand how the oil is secreted. Additionally, elaiophores of G. bifolia were compared with those of related taxa within the Oncidiinae.

Methods

Elaiophores were identified using Sudan III. Their structure was examined by using light, scanning electron and transmission electron microscopy.

Key Results

Secretion of oils was from the tips of callus protrusions. The secretory cells each had a large, centrally located nucleus, highly dense cytoplasm, abundant plastids containing lipid globules associated with starch grains, numerous mitochondria, an extensive system of rough and smooth endoplasmatic reticulum, and electron-dense dictyosomes. The outer tangential walls were thick, with a loose cellulose matrix and a few, sparsely distributed inconspicuous cavities. Electron-dense structures were observed in the cell wall and formed a lipid layer that covered the cuticle of the epidermal cells. The cuticle as viewed under the scanning electron microscope was irregularly rugose.

Conclusions

The elaiophores of G. bifolia are of the epithelial type. The general structure of the secretory cells resembles that described for other species of Oncidiinae, but some unique features were encountered for this species. The oil appears to pass through the outer tangential wall and the cuticle, covering the latter without forming cuticular blisters.Key words: Elaiophore, Gomesa bifolia, Orchidaceae, Oncidiinae, oil secretion, anatomy, micromorphology, ultrastructure