Ultrastructure ofCyanoptyche gloeocystis f.dispersa (Glaucocystophyceae)

Cyanoptyche gloeocystis f.dispersa (Geitler)Starmach is a palmelloid colonial alga that contains prokaryotic blue-green endocytobionts (cyanelles) instead of chloroplasts. The periphery of the host cell shows a peculiar lacunae system with underlying microtubules. Vegetative cells possess two rudimentary flagella. Zoospores are dorsiventrally shaped with two heterokont and heterodynamic flagella which originate from a subapical depression. This depression can also be seen in vegetative cells. Both flagella possess non-tubular mastigonemes. Main reserve product is starch lying freely in the cytoplasm. Cyanelles, enclosed singly in a host vesicle, are provided with a remnant cell wall. Thylakoids are arranged concentrically. The central part of each cyanelle harbours its DNA and one large polyhedral body, probably a carboxysome.Cyanoptyche gloeocystis f.dispersa shares all taxonomically essential characters with the monadoidCyanophora, the palmelloidGloeochaete, and the coccoidGlaucocystis. All of them are members of the cyanelle-bearing small algal classGlaucocystophyceae. Members of this class serve as model organisms for the evolution of chloroplasts from cyanophycean ancestors.Dedicated to Prof. DrLothar Geitler on the occasion of his 90th birthday.     

A light and electron microscopic study of the quadriflagellate green algaSpermatozopsis exsultans

The green flagellateSpermatozopsis exsultans Korshikov has been studied in culture by light and electron microscopy. The organism is naked, bears four flagella and is conspicuously spirally twisted. The ultrastructure and location of cell organelles (except the flagellar apparatus) has been investigated in detail using an absolute configuration analysis. With the exception of a doubling of the flagella and of the secondary cytoskeletal microtubule system,S. exsultans has the exact same complement of organelles occupying the same relative positions as has been described forS. similis. The two species are therefore correctly placed in the same genus. The usefulness of absolute orientations of cell organelles for green algal taxonomy and phylogeny is stressed.Dedicated to Prof.M. Mix on the occasion of her 60th birthday.     

Allomyces neo-moniliformis gametogenesis

Summary InAllomyces neo-moniliformis meiosis takes place during resting sporangium germination. The meiospores are characteristically binucleate and biflagellate as described byEmerson (1938) andTeter (1944). A variation in the number of nuclei and flagella per meiospore from two is correlated with germination of the resting sporangia under reduced oxygen tension. The meiospores are extremely poor swimmers and are typically amoeboid. At encystment the gamma bodies of the cell are mobilized and appear involved in cyst wall synthesis. A single mitotic division of each nucleus gives rise to four nuclei. Gamete cleavage is as described for spore cleavage inBlastocladiella (Lessie andLovett 1968). The assembly of the nuclear cap and side body complex of the spore are extremely late processes in gametogenesis. The gametes are released when the single papilla dissolves. The gametes fuse in pairs and after zygote formation the cell is uninucleate with two flagella. The biflagellate zygote is an active swimming cell. The presence of homothallism or hetero-thallism inA. neo-moniliformis is discussed.     

Flagellation and taxonomy ofAcetobacter andAcetomonas

Summary Leifson's findings, that motile, acetate-oxidizing acetic acid bacteria (Acetobacter) have peritrichous flagella, and that motile, non-acetate oxidizing ones (Acetomonas) have polar flagella, of notably short wavelength, are fully confirmed and photographically illustrated. It is not confirmed, however, that the peritrichous flagella ofAcetobacter are always of “orthodox” type with a wavelength of about 2.9 μ, nor that they always tend to be few in number. In one strain ofA. aceti they were numerous, and the wavelength was as short (1.4 μ) as that considered byLeifson to be uniquely confined to the polar flagella ofAcetomonas. Furthermore the polar flagella of the latter genus seem not always to be multitrichous, strains having been found with only a single polar flagellum.     

The spermatozoon flagella in Diphyllobothrium latum (fish tapeworm)

Summary The spermatozoon flagella of the fish tapeworm (Diphyllobothrium latum) is studied. The flagella consist of two axial filament complexes, which represent the unusual nine-plus-one pattern. The inside of the spermatozoon sheath is lined by single filaments. The mechanism of formation of this type of flagella is discussed. The spermatozoon flagella of the flatworms hitherto described seems to show some deviating features as compared with those in other species.It is a pleasure to acknowledge the skilful technical assistance of Miss Tellervo Huima. This study is supported by Finnish Medical Research Council.     

Mechanosensitive Channels in the Cell Body of Chlamydomonas

Mechanosensitive channels appear ubiquitous but they have not been well characterized in cells directly responding to mechanical stimuli. Here, we identified tension-sensitive channel currents on the cell body of Chlamydomonas, a protist that shows a marked behavioral response to mechanical stimulation. When a negative pressure was applied to the cell body with a patch clamp electrode, single-ion-channel currents of 2.4 pA in amplitude were observed. The currents were inhibited by 10 μm gadolinium, a general blocker of mechanosensitive channels. The currents were most likely due to Ca²⁺ influxes because the current was absent in Ca²⁺-free solutions and the reversal potential was 98 mV positive to the resting potential. The distribution of channel-open times conformed to a single exponential component and that of closed times to two exponential components. This mechanosensitive channel was similar to the one found in the flagella in the following respects: both channels were inhibited by Gd³⁺ at 10 μm but not at 1 μm; both passed Ca²⁺ and Ba²⁺; their kinetic parameters for channel opening were similar. These observations raise the possibility that identical mechanosensitive channels may function both in the behavioral control through the mechanoreception by the flagella and in the regulation of cellular physiology in response to mechanical perturbation on the cell body. Received: 13 May 1998/Revised: 2 September 1998     

<Emphasis Type="Italic">Sulfolobus tengchongensis</Emphasis> sp. nov., a novel thermoacidophilic archaeon isolated from a hot spring in Tengchong,China

A novel thermoacidophilic strain, designated RT8-4, was isolated from an acidic hot spring in Tengchong, Yunnan, China, and characterized phenotypically and phylogenetically. Cells of strain RT8-4 are irregular cocci with peritrechous flagella. The strain grows aerobically in either a lithotrophic or a heterotrophic mode. No anaerobic growth is apparent. Growth on elemental sulfur occurs through the oxidation of sulfur. Strain RT8-4 is capable of utilizing tryptone, d-xylose, d-arabinose, d-galactose, maltose, sucrose, d-fructose, or l-glutamic acid as the sole source of carbon. d-Glucose and d-mannose are not utilized. RT8-4 grows optimally at 85 °C and pH 3.5. The G+C content of the genome of RT8-4 is 34.4 mol%. Phylogenetic analysis based on 16S rDNA sequence as well as DNA–DNA hybridization and phenotypic characterization identifies strain RT8-4 as a novel species in the genus Sulfolobus. It is proposed that strain RT8-4 be designated as Sulfolobus tengchongensis sp. nov. The type strain is RT8-4^T.Communicated by K. Horikoshi     

Gloeomonas oderChlamydomonas? Elektronenmikroskopische Untersuchungen anGloeomonas simulans

The fine structure ofGloeomonas simulans Fott (1957) was studied electron microscopically to ascertain whether it belongs to the genusChlamydomonas rather than toGloeomonas. Most cytoplasmic elements and the cell wall do not differ from otherChlamydomonadaceae but its flagellar rootlet system is unique: Each of the two flagella has an accessory basal body; its basis is accompanied by two inner and two outer bands which are connected distally (one inner and one outer band on each side) resp. proximally (the two outer bands); the latter form a long (up to 3–5 µm) connecting band between the two flagellar bases. The nucleus contains fibrillar bundels.—The unique flagellar rootlet system seems to provide a better basis for the generic classification ofGloeomonas than the position of the contractile vacuoles or the size of the apical papilla, and strongly suggests the exclusion ofG. simulans fromChlamydomonas.

Zweiter Beitrag einer vonEttl (1965a) begonnenen Publikationsreihe.     

FLAGELLAR DEVELOPMENT AND REGENERATION IN VOLVOX CARTERI (CHLOROPHYTA)1

The biflagellate somatic cells of Volvox carteri f. nagariensis lyengar exhibit an asymmetric pattern of flagellar development. Initiallt each somatic cell has two short (4 μm) flagella but after several hours one flagellum on each cell elongates unitl it reaches a length of 12 μm. Due to the regular arrangement of somatic cells in the Volvox spheroid it is apparent that the same flagellum on each somatic is the first to elongale. The asymmetric flagellar length is maintained for about 8 h after which the second flagellum on each somatic cell elongates. When the second flagellum attains the same length (12 μm) as the first flagellum, both flagella elongale at the same rate until reaching a final length of 22 μm. Experimental removal of somatic cell flagella results in their regeneration. Somatis cells regenerate both flagella simultaneously and full length flagella are produced in about 2 h. The intial rate of flagellar regeneration is about ten times faster than the intial rate of flagllar growth in development. Cycloheximide, an inhibitor of protein synthesis, has no effect on the initial rate of flagellar regeneration but the flagella produced in the presence of the drug are half the length of flagella produced in its absence. Somatic cells are able to regenerate flagella up to the time of α and β tubulin, the major structural proteins of the flagellar axoneme, and other cellular proteins.     

The ultrastructure of zoospores ofAphanomyces euteiches and of their encystment and subsequent germination

Summary The ultrastructure ofAphanomyces euteiches during the periods of zoospore motility, encystment, and germination has been studied. The motile spore has two heterokont flagella inserted laterally into the groove of the zoospore body where each is attached to a kinetosome. The kinetosomes and flagella are anchored into the zoospore body by rootlets comprised of two rows of microtubules with up to 12 microtubules in the outer row and are attached by fine threads to a striate fiber bundle. Secondary microtubules are attached at right angles at regular intervals along the rootlets. An unidentified body, 1.25m in diameter, containing helical fibers 16 nm in diameter is present in each zoospore. This body is situated near the two kinetosomes on the side of the pyriform nucleus opposite the contractile vacuole. The Golgi complex is between the nucleus and the contractile vacuole. The latter is surrounded by a 0.5–1.0m wide zone of Golgi proliferated vesicles. Ribosomes are generally absent from this region. Endoplasmic reticulum containing tubules within the expanded cisternae are also present. Vesicles with striated electron opaque inclusions and vesicles containing a granular cortex and center that developed in previous stages of zoosporogenesis were also present. During encystment of the zoospore the latter vesicles disappear. The two flagella are shed at this time leaving a membrane-bounded granular knob protruding from each of the kinetosome terminal plates. The contractile vacuole becomes disorganized and the zoospore assumes a spherical shape. Cyst wall deposition begins immediately and is completed in 30 minutes. The spore begins to germinate 1 hour following initiation of encystment with the appearance of a bulge in the cyst wall which elongates into a germ tube. Mitotic nuclear division follows.Research supported by the College of Agricultural and Life Sciences Station Project No. 1281.Research assistant and Professor. The advice and assistance of G. A. deZoeten, G. R.Gaard, and S.Vicen are most gratefully acknowledged.     

Monoclonal antibodies to surface and cytoskeletal components of the spermatozoid ofPteridium aquilinum

Summary Detergent extracted spermatozoids of the fernPteridium aquilinum were used as mixed antigen preparations for raising monoclonal antibodies in order to obtain reagents for detecting as yet uncharacterized components of the plant cytoskeleton. Selected antibodies were studied by immunofluorescence microscopy of developing spermatids and mature spermatozoids. Some reacted directly with fixed cells, others required permeabilization treatments with cold methanol or Triton X-100. AntibodiesPas2D9 andPas6D7 bind to glycoprotein antigenic determinants that are exposed on the surface of the plasma membrane. Several antibodies interact with cytoskeletal components.Pas1D3,Pas5D8 andPas5F4 bind to the cytoskeleton of permeabilized cells including the flagella. Three react specifically with the flagellar band or associated components:Pas2G6 reacts with the whole flagellar band but shows a prominent binding to basal bodies,Pas5E2 binds exclusively to basal bodies, andPas5E7 detects mitochondria associated with the flagellar band. Cross-reactions to wheat root tip cells at different stages of the cell cycle are described inMarc andGunning (1988).Abbreviations MLS multilayered structure - MT microtubule - MAb monoclonal antibody - MAP microtubule associated protein     

Desulfitobacterium sp. strain PCE1, an anaerobic bacterium that can grow by reductive dechlorination of tetrachloroethene or ortho-chlorinated phenols

A strictly anaerobic bacterium, strain PCE1, was isolated from a tetrachloroethene-dechlorinating enrichment culture. Cells of the bacterium were motile curved rods, with approximately four lateral flagella. They possessed a gram-positive type of cell wall and contained cytochrome c. Optimum growth occurred at pH 7.2–7.8 and 34–38° C. The organism grew with l-lactate, pyruvate, butyrate, formate, succinate, or ethanol as electron donors, using either tetrachloroethene, 2-chlorophenol, 2,4,6-trichlorophenol, 3-chloro-4-hydroxy-phenylacetate, sulfite, thiosulfate, or fumarate as electron acceptors. Strain PCE1 also grew fermentatively with pyruvate as the sole substrate. l-Lactate and pyruvate were oxidized to acetate. Tetrachloroethene was reductively dechlorinated to trichloroethene and small amounts (< 5%) of cis-1,2-dichloroethene and trans-1,2-dichloroethene. Chlorinated phenolic compounds were dechlorinated specifically at the ortho-position. On the basis of 16S rRNA sequence analysis, the organism was identified as a species within the genus Desulfitobacterium, which until now only contained the chlorophenol-dechlorinating bacterium, Desulfitobacterium dehalogenans. Received: 31 August 1995 / Accepted: 14 November 1995     

Amino acid immobilization of fungal motile cells

Summary A 0.2 M mixture of L-leucine and L-lysine, a pair of amino acids which Machlis (1969) had shown could attract the zoospores of Allomyces in much lower concentrations, was found to immobilize zoospores by stopping flagellar motion. While the age of the spores does not affect the response to the amino acid mixture, the time for 100% immobilization does increase with increasing numbers of spores. Viability of the spores is not altered by treatment with the mixture of L-leucine and L-lysine and subsequent germling development is highly synchronized.Several other amino acid mixtures had a similar effect upon the Allomyces' flagellum. Indeed, L-lysine by itself seems to be the most effective compound tested. Immobilization of flagella in other fungi, algae, and one protozoan was also caused by treatment with L-leucine and L-lysine. Nothing is known of the mechanism of action of this amino acid treatment.     

The cell biology of peritrichous flagella in Bacillus subtilis

Bacterial flagella are highly conserved molecular machines that have been extensively studied for assembly, function and gene regulation. Less studied is how and why bacteria differ based on the number and arrangement of the flagella they synthesize. Here we explore the cell biology of peritrichous flagella in the model bacterium Bacillus subtilis by fluorescently labelling flagellar basal bodies, hooks and filaments. We find that the average B. subtilis cell assembles approximately 26 flagellar basal bodies and we show that basal body number is controlled by SwrA. Basal bodies are assembled rapidly (< 5 min) but the assembly of flagella capable of supporting motility is rate limited by filament polymerization (> 40 min). We find that basal bodies are not positioned randomly on the cell surface. Rather, basal bodies occupy a grid‐like pattern organized symmetrically around the midcell and that flagella are discouraged at the poles. Basal body position is genetically determined by FlhF and FlhG homologues to control spatial patterning differently from what is seen in bacteria with polar flagella. Finally, spatial control of flagella in B. subtilis seems more relevant to the inheritance of flagella and motility of individual cells than the motile behaviour of populations.     

Dealing with several flagella in the same cell

Flagella are sophisticated organelles found in many eukaryotic microbes where they perform functions related to motility, signal detection, or cell morphogenesis. In many cases, several flagella are present per cell, and these can have a different composition, length, age, or function, raising the question of how this is managed. When the flagella are equivalent and constructed simultaneously such as in Chlamydomonas or Naegleria, we propose an equal access model where molecular components have free access to each organelle. By contrast, Trypanosoma and Leishmania contain temporally distinct organelles and elongate a new flagellum whilst maintaining the existing one. The equal access model could function providing that the mature flagellum is “locked” so that it can no longer be elongated or shortened. Alternatively, access of flagellar components could be restricted at the level of the basal body, the transition zone, or the loading on intraflagellar transport trains. In organisms that contains flagella of different age and composition such as Giardia, a temporal dimension is necessary, with the production of protein components of flagella spreading over one or more cell cycles. In the future, deciphering the molecular mechanisms involved in these processes should reveal new insights in flagellum assembly and function.     

An ultrastructural study of the flagellateTetraselmis cordiformis stein (Chlorophyceae) with emphasis on the flagellar apparatus

Summary The ultrastructure of the freshwater flagellateTetraselmis cordiformis Stein (Chlorophyceae) was investigated. The general morphology could be described as typical prasinophycean (Prasinophyceae sensu Christensen) and the organism shares all generic characteristics ofPlatymonas West. The flagellar apparatus has been examined in detail. The four flagella emerge from an apical trough in the theca and are arranged in a zig-zag row. They are covered by three types of scales. Four cruciate flagellar roots of compound type are present. One part is microtubular (4-2-4-2 system) and the other prominent part is fibrillar with distinctive cross striations. The four roots are short and terminate at the bottom of the apical through, where they attach the flagellar apparatus to the theca. The four-stranded root shows no changes in root tubule configuration. In addition to the cruciate root system there are two massive rhizoplasts. The rhizoplasts exhibit different striation patterns along their length. Taxonomic implications and flagellar root system structure as it relates to current theories of evolution in green algae are discussed.     

Bacterial flagella: Do they rotate or do they propagate waves of bending?

Conclusion Whether the flagellum is rigid or nearly so or whether there are moving helical lines of contraction (Astbury et al. 1955,Lowy andSpencer 1968), incompatible sets of bonds at different radii (Klug 1967), subunits which alter their configurational states (Asakura 1966, 1970) or slip between subunits carried by edge dislocations (Harris andScriven 1971, 1973), the prevention of apparent rotation of the flagellum will result in actual rotation of the body. The differences between the two classes of mechanisms have a scale beyond the power of resolution of the light microscope. Because of this it is most unlikely that direct observation of a moving bacterium will provide evidence favouring any one of the mechanisms. The mechanism of movement of bacterial flagella remains unknown.     

The rhizobia of lupinus densiflorus Benth., with some remarks on the classification of root nodule bacteria

Summary Four strains of rhizobia from Lupinus densiflorus Benth. were found to differ from the normal slow-growing strains of Rhizobium lupini by a rapid growth on agar medium, a somewhat different pattern of carbon metabolism, good growth in simple synthetic media, and also in their host plant relationships. Three strains had subpolar flagella like other lupine rhizobia, and the same was found to be predominant in a fourth strain previously described as having peritrichous flagellation.Two strains formed effectively nitrogen-fixing root nodules in Lotus corniculatus and Anthyllis vulneraria where the other two formed semieffective or ineffective nodules. All four strains formed ineffective nodules in Lotus uliginosus and Ornithopus sativus. The slow-growing strains of Rh. lupini mostly produce ineffective nodules in Lotus corniculatus but have now been seen to be effective in Lotus uliginosus.Instead of trying to define Rh. lupini as a cross-inoculation group it seems preferable to abandon it as a species and to transfer the fastgrowing strains to Rhizobium leguminosarum sensu Graham (1964) and De Ley and Rassel (1965), in spite of their predominantly subpolar flagellation. The familiar slow-growing strains would remain in the broad group of slow-growing root nodule bacteria with purely subpolar flagellation, called Phytomyxa japonica by Graham (1964) and Rhizobium japonicum by De Ley and Rassel (1965).     

Ducellieria chodati — Alge oder Pilz?

Ducellieria chodati Teiling is an organism rarely mentioned from plankton samples. Its propagation was unknown, and all earlier authors have failed to see that it is a colourless organism. Because of its structure and some chemical reactions,Ducellieria was thought to be a member of theXanthophyceae. Many living coenobia ofD. chodati from several Austrian lakes and some steps of their reproduction have been studied: Zoospores with two unequal flagella are released. After a mobile phase they settle on coniferous pollen grains drifting in water. Inside the pollen grain, a tube or flask is developed from which zoospores are released again after one or two days. These aggregate to form newDucellieria coenobia. These observations suggest thatDucellieria chodati belongs to thePhycomycetes, perhaps to theSaprolegniales.

     

Saprospira grandis: A Flexibacterium That Can Catch Bacterial Prey by ``Ixotrophy'

Abstract A marine, multicellular, filamentous flexibacterium, Saprospira grandis Gross, can not only live heterotrophically on dissolved organic substrata, but can subsist on other microbes and can even catch motile bacteria by their flagella before killing and digesting them. Received: 7 October 1996; Accepted: 2 January 1997