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  • 1
    Electronic Resource
    Electronic Resource
    Extracellular fibril production by freshwater algae and cyanobacteria (1992)
    Springer
    Microbial ecology 23 (1992), S. 53-74 
    Details
    ISSN: 1432-184X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In order to study the ability of freshwater algae and cyanobacteria to form extracellular fibrils, a screening test using ruthenium red (RR) staining was carried out on 28 species. Five of these were examined for growth and production of fibrillar material in culture media of different phosphate (P;) contents. RR-staining and uronic acid determinations at various stages of algal growth were complemented by electron microscopy of the cells and of fibrillar material released into the medium. The lower Pi concentrations enhanced growth of Micrasterias radiata, Eremosphaera sp., and Microcystis aeruginosa, and had little or no effect on growth of a Xanthidium sp. and Scenedesmus quadricauda. Extracellular uronic acid production, which was higher in low Pi medium in M. radiata, M. aeruginosa, and Xanthidium sp., could reach levels of 50 mg/liter or more. Algae with high proportions of RR-positive cells (M. radiata, Eremosphaera sp., Xanthidium sp., and M. aeruginosa) produced high levels of slime-like material and distinct fibrils that were often seen attached to the cell surface and only slowly released into the medium. No such material was found in cultures (or supernatants) of Sc. quadricauda, which also produced relatively low amounts of polyuronic acids. Specific types of filaments, often forming “fascicles” with rectangular arrays of globular particles were observed by negative staining electron microscopy of some algal cultures. RR-positive material was also observed in the cytoplasm and on the cell walls and surfaces of M. radiata and M. aeruginosa.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00165907
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  • 2
    Electronic Resource
    Electronic Resource
    A physical relationship between soil microbes and the surface of the wheat root (1975)
    Springer
    Naturwissenschaften 62 (1975), S. 41-41 
    Details
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00594051
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Fine structure of excystment of the quadriflagellate algaPolytomella agilis (1976)
    Springer
    Protoplasma 90 (1976), S. 155-171 
    Details
    ISSN: 1615-6102
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Populations of mature resting cysts of the algaPolytomella agilis were purified from asynchronously encysting cultures and incubated in fresh culture medium to promote excystment. Up to 90 percent of the cysts germinated, with approximately 50 percent excysting between 3 and 7 hours of incubation. Each germinating cyst releases a single, fully differentiated, swimming cell. The entire excystment process of individual cysts was followed by light microscopy to establish the time course of release and cells at comparable stages of excystment were examined by electron microscopy. During the first 3 hours of incubation the cysts increase in size, presumably due to uptake of water, and a polarity is established in the cytoplasm which makes it possible to identify the site of subsequent release. Release involves a selective degradation of a portion of the cyst wall at this site followed by a physical rupturing of the weakened area. Details of the structural alterations in the wall and cytoplasm are described. The cytoplasmic organelles observed to dedifferentiate during encystment (preceding paper) are completely redifferentiated during excystment. The emergent cell is flagellated and possesses the elongate form typical of the swimming cell.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01276485
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  • 4
    Electronic Resource
    Electronic Resource
    Fine structure of encystment of the quadriflagellate alga,Polytomella agilis (1976)
    Springer
    Protoplasma 90 (1976), S. 139-154 
    Details
    ISSN: 1615-6102
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The differentiation of resting cysts of the algaPolytomella agilis was examined by electron microscopy. During encystment the free-swimming, quadriflagellate unicells lose their flagella, sink to the bottom of the culture, and form a thick cell wall. Populations of cells at various stages of encystment were collected on microscope slides placed at the bottom of the culture flasks. The mature cyst wall consists of four layers which are laid down sequentially next to the plasma membrane. Freeze-etching has shown that the first layer of wall deposited consists of fibrils which are formed partly embedded within the plasma membrane. A proliferation of rough endoplasmic reticulum and Golgi bodies is seen in early stages of encystment followed by a reduction in size or number of these organelles and of plastids in the maturing cyst. Microtubular structures, including the basal bodies, dedifferentiate and are not observed in the later stages of encystment. The redifferentiation of the swimming cell during excystment is described in the companion paper.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01276484
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  • 5
    Electronic Resource
    Electronic Resource
    Acid stress and lake bacteria: Ultrastructural and physiological correlates of some acid and copper stresses (1988)
    Springer
    Hydrobiologia 160 (1988), S. 241-247 
    Details
    ISSN: 1573-5117
    Keywords: acid stress ; bacteria ; biodegradation ; cell envelope ; copper stress ; ultrastructural/physiological correlates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A description is given of concurrent changes in bacterial ultrastructure and physiology in relation to applied stresses of acid and/or copper: the environmentally-relevant correlations are explored as a potential tool for ascertaining mechanisms of acid rain damage. Ultrastructural analysis permits a differentiation, on a gross scale, between different levels of acid and combined acid/copper stresses in laboratory experiments on enrichment cultures of lacustrine microbial populations rich in Gram-negative bacteria. For the dominant morphotypes of Gram-negative bacteria, changes in the cell envelope (and its extensions) correlate also with changes in activity of envelope-associated enzymes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00007138
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  • 6
    Electronic Resource
    Electronic Resource
    The ultrastructural indicators of aquatic ecosystem health (1992)
    Springer
    Journal of aquatic ecosystem stress and recovery 1 (1992), S. 309-317 
    Details
    ISSN: 1573-5141
    Keywords: ultrastructure ; indicator ; picoplankton ; viruses ; algae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Analyses by transmission electron microscopy (TEM) of the smallest organisms in surface waters can be used to assess ecosystem health; the evidence for this statement is reviewed and recommendations are made for optimal use of TEM technology in providing such assessments. Those groups of small organisms currently being considered as indicators of ecosystem health (viruses, bacteria, autotrophic picoplankton, and autotrophic nanoplankton) are reviewed briefly as subjects for monitoring by TEM. New information on direct counting by TEM of viral femtoplankton indicates that viruses can be present in numbers 103 to 107 times greater than previously estimated by the traditional counts of plaque-forming units using various host bacteria. Such concentrations indicate that virus infections may exert ecological control over planktonic microbes. Ultrastructural research on prokaryotic picoplankton suggests that TEM analyses of cells in ultra-thin sections can be used to speciate the picoplankton and to diagnose them for cytological modifications related to environmental stress. Considering their great importance, episodically, to primary productivity and to modulating the speciation of higher levels in the food web, such picoplankton ultrastructural analyses could be pursued with profit as a diagnostic tool. For decades, the ultrastructure of some eukaryotic nanoplankton has been known to vary in specific ways to specific stresses in laboratory experiments. An extension of these structure-function correlations is potentially a useful tool to provide indicators of ecosystem health. The barriers to progress in such research are now understood and can be overcome.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00044172
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