Naegleria fowleri: Light and electron microscopy study of mitosis (original) (raw)
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Protistology, 2019
Nucleophaga amoebae belongs to the phylum Rozellomycota (Opisthokonta), a widespread clade of parasites, considered as intermediate link between fungi and microsporidia. This organism is an obligate intranuclear parasite of the free-living amoeba Thecamoeba quadrilineata. The life cycle of this organism is difficult to study, many details require further clarification, and available light-microscopic images are limited in number and quality. We performed real-time observations on the process of parasite propagation in amoeba culture using Eppendorf Cell Imaging Plates and Differential Interference Contrast (DIC) microscopy. Development of the parasite was traced from the engulfment of spores by the amoeba cell to the production of a new generation of spores. Nucleophaga cells proliferate inside the host nucleus. The earliest intranuclear developmental stages that we observed were rounded uninucleate cells located at the margin of the host nucleolus. Growth resulted in formation of a large multinucleate plasmodium, which further became segregated into numerous individual uninucleate sporoblasts. After a period of maturation, sporoblasts transformed into the rounded spores enclosed in the sporophorous vesicle, probably formed by the remnants of the membrane of the plasmodium. At the final stage of the developmental cycle the amoeba cell died, its envelope, as well as the nuclear membrane broke, and the spores were released into the environment. The developmental cycle took approximately 5 days. Infected amoebae never divided, so we can suggest that the infection suppressed mitosis in the host cell.
The ultrastructure of mitotic nuclei of Blastocrithidia triatomae
Zeitschrift für Parasitenkunde (Berlin, Germany), 1983
The fine structure of mitotic nuclei of the flagellate Blastocrithidia triatomae has been studied by serial thin sections and three-dimensional reconstructions. The sequence of changes during the four stages of mitosis are described. A set of three dense plaques is constantly found in the equatorial stage of mitosis. The microtubular spindle is organized around these plaques. The plaques split into halves at the end of the equatorial stage, and the half-plaques migrate to the spindle ends. Elongation of the mitotic nucleus occurs after the division of the plaques. This elongation is associated with the formation of an interpolar bundle of microtubules. The equatorial spindle is formed by 26-28 microtubules and is 1.5 micrometers long. The nucleolus attaches itself to the nuclear envelope and persists up to the elongational stage; then it disintegrates and is reorganized in daughter nuclei. Mitotic events in B. triatomae are essentially similar to those in Trypanosoma cruzi epimastig...
Entamoeba histolytica: ultrastructure of the chromosomes and the mitotic spindle
Experimental parasitology, 2006
We have analyzed by transmission electron microscopy the mitotic process of Entamoeba histolytica trophozoites in an asynchronous population of axenically cultured parasites. Our observations showed that nuclear microtubules, initially located at random in the karyosome during prophase, formed in subsequent stages a mitotic spindle closely related to the nuclear membrane at the polar regions of dividing nuclei. In late prophase and in anaphase, chromosomes appeared as dense bodies 0.1-0.5 microm. At least 15 chromosomes appeared in favorable planes of section, arranged as an incomplete elliptical circle, in close contact with microtubules. There was no morphological evidence of structures resembling the kinetochores of higher eukaryotes. When cut in cross-section, the mitotic spindle was made of 28-35 microtubular rosette assemblies. The latter probably correspond to a similar number of chromosomes, as has been shown by others with pulse-field electrophoresis and fluorescence micros...
Journal of Cell Science
Light-microscopy observation of the dinoflagellate Prorocentrum micans after silver-staining of the argyrophilic proteins of the nucleolar organizing region (Ag-NOR staining) showed the presence of nucleolar material throughout the vegetative cell cycle, and in particular during all the mitotic stages. This contrasts with the case in most higher eukaryotes, in which nucleoli disappear at the end of prophase and are reconstituted in daughter cells during telophase. Electron-microscope (EM) observations after conventional or fast-freeze fixation revealed that during interphase several functional nucleoli with three compartments (NORs, the fibrillogranular and the preribosomal granular compartments) are present in a nucleus in which the envelope is persistent and the chromosomes are always compact. During early prophase, when chromosomes are beginning to split, the nucleoli remain functional, whereas in late prophase they contain only a NOR and the granular component, and the chromosom...
Isolation of membrane-associated folded chromosomes fromAnacystis nidulans
Zeitschrift für allgemeine Mikrobiologie, 1982
Particles containing folded DNA were isolated from the blue-green alga Anacystis nidulans. The structure of these particles is vesicle-like and similar to that of membrane-associated nuclear bodies which had been isolated form Escheiichia eoEi under comparable conditions. The sedimentation constant is between 8000 and 9000 Svedbergs. The DNA is inside the particles and is attached to the thylakoid membranes. The DNA of bacteria is packaged into a very small volume of about 1 pm3 in the cell and can be isolated by enzymic digestion of the cell wall and subsequent Iysis of the spheroplast by detergents. The lysis conditions can be varied in such a way that the DNA does not unfold and can be isolated in a condensed state. This so-called nuclear body or nucleoid contains in addition to DNA also RNA, proteins, and cell envelope material associated with the chromosome. Nucleoids have been isolated from Esclie
Southeast Asian Journal of Tropical Medicine and Public Health, 2011
Seven stains were studied to determine the best color and contrast for staining the developmental stages of free living pathogenic Acanthamoeba and Naegleria species. The acid-fast bacilli stain (AFB) produced a blue color without contrast; trichrome-eosin and modified Field's showed various color contrasts; Giemsa, iron-hematoxylin, modified AFB and Gram produced only one color which distinguished the nucleus, nucleolus, cytoplasm, food- and water-vacuoles. The motile organs (acanthopodia, pseudopodia, lobopodia and flagella) were also clearly differentiated but produced a similar color as the cytoplasm. These motile organelles were first induced by incubating at 37 C for at least 15 minutes and then fixing with methanol in order to preserve the protruding morphology prior to staining. The trichrome-eosin and iron-hematoxylin stains showed good color contrast for detecting all three stages, the trophozoite, cyst and flagellate; Giemsa and Gram stained the trophozoite and flagellate stages; the modified Field's and modified AFB stains stained only the trophozoite stage. Depending on the purpose, all these stains (except the AFB stain) can be used to identify the developmental stages of Acanthanweba and Naegleria for clinical, epidemiological or public health use.
Mapping the Single Origin of Replication in the Naegleria gruberi Extrachromosomal DNA Element
Protist, 2019
The genes encoding the ribosomal RNA (rRNA) subunits of the amoeba Naegleria gruberi are encoded in a relatively uncommon arrangement: on a circular extrachromosomal DNA element with each organism carrying about 4,000 copies of the element. As complete sequence analysis of the N. gruberi chromosomal DNA revealed no copy of the rRNA genes, these extrachromosomal elements must therefore replicate autonomously. We reported elsewhere the molecular cloning and the complete sequence analysis of the entire rRNA gene-containing element of N. gruberi (strain EG B). Using neutral/neutral two-dimensional agarose electrophoresis, the region in the element enclosing the single replication origin using DNA from asynchronous and axenically propagated N. gruberi populations was localized within a 2.1 kbp fragment located approximately 2,300 bp from the 18S rRNA gene and 3,700 bp from the 28S rRNA gene. The results indicate that replication occurs from a single origin via a theta-type mode of replication rather than by a rolling circle mode. Further, G-quadruplex elements, often located near DNA replication origins, occur in and near this fragment in a repeated sequence.
Electron microscopic visualization of transcribed genes in the nucleus of Amoeba proteus
Experimental Cell Research, 1978
An electron microscopic examination by Miller's technique of nuclei of Amoeba proteus has revealed two types of transcriptionally active genes. The putative nucleolar genes have an average length of 6.07 pm and are transcribed throughout their entire length. On occasion a second type of active gene is observed as discrete regions on long chromatin fibers. These regions measure 3.21 wrn and are not tandemly repeated. We have used Miller's technique [l-3, 131 to observe the transcriptionally active genes in the nucleus of the unicellular protozoan, Amoeba proteus. We report here preliminary observations on the morphology of two types of structures that are interpreted as transcriptionally active genes.
Systematics of Protosteloid Amoebae
2011
Among the protosteloid amoebae, life cycles vary dramatically (Figures 1, 2). All include both an amoeboid trophic stage and a fruiting stage (Figures 1, 2); however, some species also include flagellates and cysts. A few definitions are given below. Definitions Amoeboflagellate: an amoeba that can produce one or more flagella or an amoeba that has lost this ability yet retains the overall morphology of an amoeboflagellate (See Spiegel 1982 for a comparison between the flagellate cell of Planoprotostelium aurantium and the virtually identical nonflagellate cell of Protostelium mycophaga; and Spiegel et al. 1995a for an explanation of the concept of the nonflagellate amoeboflagellate). Complex life cycle: A life cycle that consists of one amoeboid state that develops into another where the second morphologically distinctive amoebal state cannot revert to the first by a simple physiological change [e.g. the flagellate/nonflagellate transition when water is added or removed]. Cyst: resistance structures that lack a stalk. Obligate Amoeba: an amoeba that cannot produce a flagellum and is morphologically distinct from any known amoeboflagellate (Spiegel and Feldman 1985); in life cycles with two amoebal stages, these are the amoebae that differentiate into fruiting bodies. Plasmodium: a specialized type of obligate amoeba with many, sometimes hundreds, of nuclei (Spiegel and Feldman 1985). Prespore cell: the beginning of the transition from amoeba or plasmodium to a fruiting body. CHAPTER 2 LINDLEY LA, STEPHENSON SL, SPIEGEL FW (2007) PROTOSTELIDS AND MYXOMYCETES ISOLATED FROM AQUATIC HABITATS. MYCOLOGIA 99(4): 504-509.