Presence Of Sheath Research Articles

Structure, morphogenesis of calyptra and nomenclatural identity of Trichodesmium erythraeum Ehr. (Cyanobacteria) newly recorded off the Southwest coast of Bangladesh

Trichodesmium erythraeum Ehrenberg 1830 (Cyanobacteria) has been described and newly recorded from three km off the west coast of the St. Martin’s Island (SMI), Cox’s Bazar, Bangladesh. The Red Sea algal bloom was narrowly elliptical raft-like loose aggregates 20-40 cm long, 4-8 cm wide and 2-3 cm thick. Volume of small and large Sea sawdust were 160×10-6 to 960×10-6 m3 consisting of 25-153 millions flat tuft or spindlelike colonies measured 830-1500 μm long and 155-260 μm wide with 13-16 filaments laterally in the median region. Sheath was present around each trichome even covering the tip cell wall the feature has so far not been reported for the Trichodesmium spp. Because of most likely sticky nature of the sheath 300-600 μm long filaments of 195-450 formed compact colonies without colonial sheath around. In interior filaments cells were rectangular 7-10 μm long and 6.3-10 μm wide with abundant gas vacuoles, bluish-green red, no diazocytes developed and without calyptrae. Cells of peripheral filaments were without gas vacuoles, cytoplasm disorganized, appearing necrotic with glycogen granules, and produced convex to sickle-shaped four-layered calyptra consisting of outermost sheath followed by outer extra thick wall, tip cell wall and inner extra thick wall on the tip cell. Calyptra was also produced on tip cells of tapered filaments. Presence of sheath around each trichome binding all filaments into a colony without colonial sheath described here, and presence of nitrogenase containing diazocytes in interior filaments, both temporal and spatial segregation of N2 fixation and photosynthesis within the photoperiod described and discussed in literature made the authors to consider T. erythraeum Ehr. a distinct taxon under family Microcoleacece.
 Bangladesh J. Plant Taxon. 27(2): 273-282, 2020 (December)

Several problems of the polyphasic approach in the modern cyanobacterial system

The taxonomic criteria for cyanobacteria were substantially changed with the introduction of electron microscopy and molecular analyses. The system must be modified according to the results following from these studies and the genetic diversification in various clades must be used as an obligatory basic method for cyanobacterial classification. However, cytomorphological and ecological data cannot be neglected. It is necessary to discover always the relations, correlations, interactions, and coincidences between the genetic basis and morphological and ecological markers. They can have various taxonomic values in various clades and their importance must be re-evaluated in different taxa, but they cannot be omitted. Therefore, cryptic, morpho-, and ecospecies also appear based on different kinds and combinations of characters. The “polyphasic approach” is a methodological procedure that has been a means of dealing with all these problems. From this approach, the modern cyanobacterial system resulted in which numerous genera were divided into more generic entities, as well as making problematic the use of some traditional expressive characters, such as unicellularity vs. filamentous forms, the presence of sheaths, type of branching, presence of aerotopes, etc. The nomenclatural rules for phototrophic organisms must be respected even in this new system.

An entomological survey and determination of vectoral infection rates for lymphatic filariasis in Ogoniland, Niger Delta, Nigeria

A combined field and laboratory investigation was conducted in five communities of Ogoniland to determine the status of lymphatic filariasis in relation to mosquito vectors for both dry and wet seasons of the year. The human bait method was employed twice weekly in the morning hours (6.00 am-7.30 am), and evening hours (6.00 pm- 8.30 pm), for collection of mosquitoes that probed into the skin using an aspirator. The mosquitoes collected were taken to the laboratory for identification, and dissected in 0.9% saline using standard procedure, while the microfilariae were identified using presence of sheath at their posterior region. The infection rate was obtained by expressing the percentage of the numbers positive against the numbers caught, while ATP of the mosquitoes were obtained using the values of microfilarial density, thus addition of monthly transmission potential (MTP) will give ATP of the vector species. Three mosquito species – A. gambiaesl, A. nili, and Culex p. fatigans, were identified as major vectors of the disease. The estimated annual vector biting and filarial prevalence rates for these mosquito species are 2, 220 and 22.2% for A. gambiae sl, 256 and 11.5% for A. nili and 7,747 and 24.3% for Culex p. fatigans. The mean microfilarial (mf) density in these vectors were 3.1 for A. gambiae sl, 0.6 for A. nili and 3.3. for Culex p. fatigans, with annual transmission potential (ATP) of 37, 4, and 50 for A. gambiae sl, A. nili, and Culex p. fatigans respectively. From the result of this study, it appears that Culex species showed greatest vectoral capacity in the transmission of lymphatic filariasis in the study area. The low microfilarial (mf) density in the human population, population density of the vectors and unsuitable ecological conditions may indicate a low endemicity of lymphatic filariasis in the study. The presence of this parasite may become health risk for the rural communities of the study area especially after a long period of infection.Keywords: Lymphatic filariasis; mosquitoe; annual transmission potential.

Magnetron Amplifier-Type Helix Loaded Waveguide Analysis Based on Dispersion Relation

The theory of tenuous hollow relativistic electron beam in the magnetron-type helix loaded waveguide was presented in the presence of sheath and axial magnetic field. The dispersion relation was obtained with the aid of the proper boundary conditions. The effects of electron beam, helix, and vane parameters on the gain and Doppler-shifted frequency were investigated numerically. The numerical results show that the presence of the vane considerably increases the gain. It has been shown that the maximum values of the gain occur at lower harmonics and the maximum values of the Doppler-shifted frequency occur at higher harmonics. The results show that the gain of the system increases when the helix move away from the vane.

Microfilariae coexisting with a follicular lesion in thyroid aspirate smears in an uncommon case of a retrosternal thyroid mass, clinically presenting as malignancy

To the Editor, Filarial infection is a public health problem in the tropical regions of South-east Asia, including the Indian subcontinent that includes certain areas of heavy infestation, like Madhya Pradesh, Bihar, Jharkhand, along with others. It is caused by the nematodes Wuchereria bancrofti, Brugia malayi, Brugia tumori and others, transmitted through a mosquito Culex fastigens. Its disease manifestations include lymphoedema and superficial swellings.[1–3] Varied sites of involvement documented on aspirate smears include breast, epididymis, spermatic cord, lungs, etc.[4–6] Over the years, it has been uncommonly identified in the thyroid.[7–13] Herein, we present an uncommon case of a retrosternal thyroid mass that clinically presented as malignancy and on aspiration cytology disclosed a follicular lesion with coexisting microfilariae. A 55-year-old gentleman from Ranchi (Jharkhand, India) was referred to our hospital with complaints of anterior neck swelling since 2 months, associated with dysphagia to solids and alteration of voice for a month. He had been a tobacco chewer for 30 years. He also disclosed history of aspiration a month ago, along with breathlessness. On clinical examination, his general condition was good. On local examination, a soft swelling was noted over his right thyroid and isthmus and a 10×7 cm hard swelling was noted over his left thyroid, extending into the retro sternum that did not move with deglutition. Left vocal cord palsy was noted. There was no stridor. Clinically, he was presumed with a diagnosis of stage IV carcinoma thyroid. He underwent laboratory and radiological investigations, including an outside computed tomography (CT) scan, followed by fine-needle aspiration cytology (FNAC) on three occasions, including twice at our hospital. His hemoglobin was normal i.e. 12 gm/dl (Normal: 13-17 gm/dl). Total leukocyte count was high i.e., 13.7×10e9/L (Normal: 4-10×10e9/L), including absolute neutrophilia. Percentage and absolute eosinophil counts were normal 4.73% and 0.65×10e9/L (Normal: 1-6% and 0.2-1×10e9/L). Basophil percentage was marginally high i.e., 0.33% (Normal: 0-0.2%). His thyroid function tests were within normal limits. There was no access for thyroid scan results. Limited accessible imaging findings included a CT scan report that disclosed a left thyroid lobe lesion, eroding the thyroid cartilage, trachea and thoracic inlet. His chest X-ray was normal. FNAC was performed by multiple passes in the thyroid using a 23-gauge needle. Smears were fixed in alcohol stained with Papanicolaou (Pap), while air-dried smears were stained with Giemsa stain. The initial smears were reported as papillary carcinoma thyroid. Repeat smears were hypercellular, comprising benign appearing follicular cells in focal acinar formations, flat monolayered sheets and focal papillaroid arrangements, lacking anatomical edge. Cells exhibited focal nuclear overlapping, focal grooves and fine chromatin clearing in rare cells. No nuclear elongation, uniform nucleomegaly or intranuclear inclusions were noted within the hypercellular smears. Besides, there were sheets of cystic macrophages and Hurthle cells in a background of thick and thin colloid. Diagnosis of an atypical follicular lesion of undetermined significance was considered. On critical examination, microfilariae of W. bancrofti were identified that displayed presence of sheath and were deficient in somatic nuclei at the posterior end of the body that was curved. A few rhomboid-shaped Charcot Leyden (CL) crystals were noted. There were no inflammatory cells. The previous smears were reviewed and a final diagnosis of microfilarial infestation, along with follicular lesion (of undetermined significance) was offered. [Figure ​[Figure1a1a–e] Figure 1 a) Hypercellular smear showing clusters of follicular cells. Pap stain ×100; b) Follicular cells with surrounding macrophages. Pap stain ×400; c) Cells showing focal nuclear overlapping. Pap stain ×1000; d) Flat monolayered sheet ... Following, the patient succumbed to death within a week. However, post-mortem examination could not be performed.

Vegetative survival of some wall and soil blue-green algae under stress conditions

Lyngbya major (a wall alga), survived throughout year, maximally to >80 % at atmospheric temperature (AT) of 17-36 degrees C and relative humidity (RH) 60-100 % in rainy and spring seasons, but the survival was 43-64 % in winter when AT decreased to 5 degrees C and RH was 65-98 %, and 15-23 % in summer when AT reached 48 degrees C and RH was 23-60 %. All soil algae (Lyngbya birgei, Aphanothece pallida, Gloeocapsa atrata, Oscillatoria subbrevis, O. animalis) survived >90 % in rainy season when soil moisture content (SMC) was 89-100 %. Lowering of SMC to a minimum of 55 % in spring and 39 % in winter led L. birgei, O. subbrevis and O. animalis to survive from 75, 66, and 65 %, respectively, in spring and 12, 14, and 20 % in winter, and A. pallida and G. atrata not at all in both seasons. All soil algae did not survive in summer when SMC was 12-30 %. Myxosarcina burmensis survived only in rainy and spring seasons when pond water temperature (PWT) was 19-25 degrees C and 18-26 degrees C, respectively, and not in winter and summer when PWT was 2-14 degrees C and 25-36 degrees C, respectively. L. major and A. pallida survived almost equally well under both submerged and air-exposed conditions for 15 d but less if submerged for more time than air-exposed on moist soil surface, while L. birgei, G. atrata, O. subbrevis, and O. animalis survived submergence in liquid medium better and longer than air-exposure on moist soil surface. Pond alga M. burmensis survived submergence better than air-exposure, true to its aquatic habitat. All algae survived less and died without forming any resistant cells when exposed to physical and physiological water stress (imposed by growing them on highly agarized media or in salinized liquid media), light stress (at 0, 2 and 10 micromol m(-2) s(-1) light intensity) or following UV shock (0.96-3.84 kJ/m(2)). A. pallida and G. atrata cells did not divide on 8 % agarized solid media, in > or =0.3 mol/L salinized liquid media, and in darkness. The presence of sheath over L. major and L. birgei filament cells and mucilage cover over A. pallida and G. atrata cells protect them against physical desiccation to some extent but not against UV shock.

Experimental observation of magnetosome chain collapse in magnetotactic bacteria: Sedimentological, paleomagnetic, and evolutionary implications

Magnetotactic bacteria precipitate intracellular crystals of single-domain magnetite (Fe3O4) and/or greigite (Fe3S4), which have often been implicated in carrying the natural remanent magnetization (NRM) of freshwater and marine sediments. In vivo, the magnetic crystals are usually aligned in chains such that their moments add together, generating net cellular moments high enough to rotate the cells passively to align with the geomagnetic field. A magnetostatic/biophysical analysis demonstrates that this arrangement is out of dynamic equilibrium and would collapse spontaneously without a support mechanism. Past rock magnetic analyses of shallow water marine carbonates suggest that partial collapse does occur during diagenesis and dolomitization.To calibrate this effect we induced magnetosome chain collapse in Magnetospirillum magnetotacticum strain MS-1 by progressive sonification and treatment with detergents and monitored the changes with rock magnetic analysis and TEM. Although it has been speculated that the cell wall and associated membrane structures act to prevent magnetosome chain collapse, our data indicate that magnetosome linearity persists long after cells are disrupted. This is consistent with prior observations that in some magnetotcocci the magnetosome chains pass through the cell interior, precluding continuous contact with the cell wall and implying additional support structures exist in some species.Using TEM tomographic reconstructions prepared with a magnetic technique that prevents chain collapse, we examined the three dimensional ultrastructure of magnetosomes without the problem of post-mortem magnetosome motion. This method revealed the presence of an intracellular organic sheath beyond that of actin-like filaments reported recently that follows the chain of magnetosomes, which we postulate evolved to hold the crystals in place and enhances their ability to preserve NRM in sediments. As the genomes of two magnetotactic bacteria contain several apparent homologues of known eukaryotic cytoskeletal proteins, natural selection for magnetotaxis may have played a role in the evolution of precursors to the eukaryotic cytoskeleton. The presence of this sheath is also consistent with the observation of electron translucent material associated with putative magnetofossil chains in ALH84001.

Spirirestis rafaelensis gen. et sp. nov. (Cyanophyceae), a new cyanobacterial genus from arid soils

A new cyanobacterial genus and species, Spirirestis rafaelensis , is described from soils of a semi-arid Utah juniper community in the San Rafael Swell, Utah, U.S.A. Multiple isolates of the organism have only been recovered from well-crusted, protected, and totally undisturbed soils at this site; it has not been recovered from any of the other 40 sites we have examined in the Sonoran, Mojave, Chihuahuan, Colorado Plateau, or Great Basin deserts during the last eight years. Spirirestis shares morphological characters with members of both the Scytonemataceae and Microchaetaceae, principally heterocyte formation, false branching, and presence of sheath. However, unlike the trichomes of all previously described genera in these families, most trichomes of Spirirestis are tightly spiraled. 16S rRNA sequence data suggest that Spirirestis is more closely related to members of the Microchaetaceae than to members of the Scytonemataceae or Rivulariaceae. The data also support the maintenance of Microchaetaceae and Scytonemataceae as separate families.

Genetics of mutations affecting the development of a barley floral bract.

Two groups of mutants that affect the morphology of the lemma, a floral bract of barley, are described. The first comprises phenotypes associated with mutant alleles of calcaroides loci. On the lemma of these mutants, a well-organized neomorphic structure is formed, termed the sac. We provide a morphological description of wild-type (WT) and mutant lemmas, based on scanning electron microscopy (SEM), showing that both consist of similar tissues, but that the mutant is characterized by reversed growth polarity. The sac is a unique structure among grasses, and it is remarkable that recessive mutations at five different genetic loci lead to the same organ. The second group of mutants carry recessive alleles of two leafy lemma genes, both of which are necessary to cause the transformation of the lemma into a structure having all characteristics of a vegetative leaf, as shown by SEM analysis. The presence of sheath, blade, and ligule in the mutant lemma suggests that wild-type lemma development is interrupted at a leaf-like stage. The genes cal a, b, C, d, 23, lel1, and lel2 have now been mapped at precise positions on linkage groups 2, 7, 7, 3, 7, 5, and 7, respectively. The mutants considered in this article are unaffected in other floral organs. A model for lemma development is suggested.

Metal Resistance in Trees: The Role of Mycorrhizae

On metal contaminated soils, the colonization and survival of plants is known to occur primarily through the selection of genotypes with heritable resistance traits that occur naturally within some species and populations (Bradshaw and McNeilly 1982, Bradshaw 1984, Baker 1987, Shaw 1990, Ernst et al. 1992). Recent studies have pointed to the additional importance of phenotypic plasticity, itself under normal genetic control, which potentially allows the survival of individual plants in contaminated environments until favourable conditions are encountered either spatially or temporally (Bradshaw 1991, Dickinson et al. 1991); this may involve an alteration of gene expression within an individual plant (Dickinson et al. 1992, Turner and Dickinson 1993a, b). It has also been suggested, however, that the ability to withstand pollution stress may be due to mycorrhizal colonization of roots ameliorating the toxicity of heavy metals (Dickinson et al. 1991, Wilkins 1991). The evolutionary significance of this possibility has not really been considered, but there is considerably more opportunity for genetic change in the shorter lifecycle of a fungus than in even a short-lived higher plant. We argue that elucidation of genetic changes within mycorrhizal communities is crucial to a proper understanding of the survival of long-lived and non-tolerant plants in metal-contaminated soils. Mycorrhizae are found associated with most higher plants and the fossil record suggests that even the earliest land plants were heavily infected (Begon et al. 1990). Perennial species that are normally or occasionally arbuscular mycorrhizal occur in almost twice as many habitat types as those that are infrequently mycorrhizal, which suggests that mycorrhizae increase the niche width of plants (Peat and Fitter 1993). The widespread arbuscular mycorrhizae make up three quarters of the mycorrhizal associations recorded in the British flora; long-lived woody species are almost invariably mycorrhizal. Over 150 taxa of mycorrhizae have been found to be associated with Salix (willows) alone in Britain (Watling 1992). As obligate symbionts, mycorrhizal fungi receive carbon and perhaps other resources from the plant host but it is often difficult to demonstrate that infected plants receive any benefit from the association in the field (Dosskey et al. 1990, Stenstrom and Ek 1990, Colpaert et al. 1992, Colpaert and Van Assche 1993). However, benefits that have been identified include improved uptake of less mobile nutrients such as phosphate, improved water relations, protection from fungal pathogens and protection from soil toxins (Harley and Smith 1983, Fitter 1991, Abbott et al. 1992, Fitter and Merryweather 1992, Gadd 1993). It is thought that the detrimental effect of air pollution on mycorrhizae is a likely causal factor of forest decline in Europe and North America (Jakucs 1988, Fellner 1989), further indicating the likely importance of the symbiotic association. Communities of mycorrhizal fungi change with time after planting trees (Last et al. 1992), and the absence of sheathing (ecto-)mycorrhizae may account for poor establishment of planted trees on some soils, including metal-contaminated soils (Burton and Morgan 1984, Ernst et al. 1990, Kahle 1993). Other studies have shown that, despite an apparent protective role of mycorrhizae, tree roots in mineralized forest soils naturally enriched with metals have a reduced active mycorrhizal root tip count (Bell et al. 1988). Metal-tolerant fungi may be more abundant in soils with extremely high concentrations of metals, but metal-tolerant fungi can also be isolated from clean soil, which suggests that wide genetic variation for metal tolerance may exist in many normal mycorrhizal populations. Mycorrhizal isolates from nickel-, copperand zinc-contaminated soils that have been grown on axenic media containing elevated metals have been found not to grow any better than the same species isolated from clean soils; it appears to be the behaviour of the fungus in the presence of roots that is particularly critical (Brown and Wilkins 1985a,b, Jones and Hutchinson 1986a, b). Seedlings of birch, pine and spruce are less susceptible to toxic concentrations of zinc, copper, nickel and aluminium in the growth medium in the presence of sheath-

THE CAPSULES OR SHEATHS OF BACILLUS ACTINOIDES

The production of capsules or sheaths is subject to considerable variation in this species. Thus far coagulated serum has been found the only substrate to stimulate its appearance. It is not known whether the capsular substance is induced by the parasitism. The presence of sheaths within epithelial cells and their absence in cellular exudates suggest the inference that the sheath is a protective substance when the parasite multiplies in living cells. The complete absence of sheaths in some strains might make the recognition of this species difficult, but if its other characters both positive and negative are kept in mind, this difficulty will not be serious. Next in importance to fluctuations in the presence or absence of capsules is the change in metabolic processes leading to the production and accumulation of fatty substances in the cultures. The original capsular material resembles in its optical characters myelins. In the course of artificial cultivation fat granules make their appearance at the expense of the original myelin-like substance. This process may be regarded as a degenerative one in the sense that it accompanies the gradual loss of the function of secreting the capsular substance.