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  • 1
    ISSN: 1572-9699
    Keywords: ABC-transporter ; decarboxylation ; energetics ; lactic acid bacteria ; multidrug resistance ; secondary transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Lactic acid bacteria play an essential role in many food fermentation processes. They are anaerobic organisms which obtain their metabolic energy by substrate phosphorylation. In addition three secondary energy transducing processes can contribute to the generation of a proton motive force: proton/substrate symport as in lactic acid excretion, electrogenic precursor/product exchange as in malolactic and citrolactic fermentation and histidine/histamine exchange, and electrogenic uniport as in malate and citrate uptake in Leuconostoc oenos. In several of these processes additional H+ consumption occurs during metabolism leading to the generation of a pH gradient, internally alkaline. Lactic acid bacteria have also developed multidrug resistance systems. In Lactococcus lactis three toxin excretion systems have been characterized: cationic toxins can be excreted by a toxin/proton antiport system and by an ABC-transporter. This cationic ABC-transporter has surprisingly high structural an d functional analogy with the human MDR1-(P-glycoprotein). For anions an ATP-driven ABC-like excretion systems exist.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 31 (1995), S. 311-316 
    ISSN: 1059-910X
    Keywords: EM-tomography ; Reconstructions ; Back projection ; Section collapse ; Distortion of Z dimensions ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Using back projection for reconstruction and tilt series of Epon or Lowicryl embedded and sectioned material, we demonstrated: (1) a reduction in thickness of 50% for Epon and 80% for Lowicryl sections, and (2) a non-uniform density distribution along the electron-optical axis in sections. The highest density was found at the vacuum exposed side of the section. The formvar side of the section showed a similar increase in density, but not to the same extent. Minimalization of electron exposure, even without pre-exposure, did not affect the reconstructed thickness, nor did it affect the non-uniform density distribution. However, parallax measurements showed that at 150K, collapse of Epon sections does not take place. For EM-tomography of plastic embedded material our findings imply that at the top and bottom portion of the sections the dimensions of the reconstructed structures are distorted, but that in the middle portion the dimensions are reliably retained. © 1995 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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