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Tserendorj Gegeensuvd Marinova Elena Lechterbeck Jutta Behling Hermann Wick Lucia Fischer Elske Sillmann Marion Märkle Tanja Rösch Manfred 《Vegetation History and Archaeobotany》2021,30(1):35-46
Vegetation History and Archaeobotany - A system of farming with an alternation of land use between being cultivated or left fallow as grassland (Feldgraswirtschaft) developed in southwestern... 相似文献
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Sven Hammerschmidt Astrid Müller Hanna Sillmann Martina Miihlenhoff Raymond Borrow rew Fox Jos van Putten Wendell D. Zollinger Rita Gerardy-Schahn Matthias Frosch 《Molecular microbiology》1996,20(6):1211-1220
A mechanism of capsular polysaccharide phase variation in Neisseria meningitidis is described. Meningococcal cells of an encapsulated serogroup B strain were used in invasion assays. Only unencapsulated variants were found to enter epithelial cells. Analysis of one group of capsule-deficient variants indicated that the capsular polysaccharide was re-expressed at a frequency of 10?3. Measurement of enzymatic activities involved in the biosynthesis of the α-2,8 polysialic acid capsule showed that polysialyltransferase (PST) activity was absent in these capsule-negative variants. Nucleotide sequence analysis of siaD revealed an insertion or a deletion of one cytidine residue within a run of (dC)7 residues at position 89, resulting in a frameshift and premature termination of translation. We analysed unencapsulated isolates from carriers and encapsulated case isolates collected during an outbreak of meningococcal disease. Further paired blood-culture isolates and unencapsulated nasopharyngeal isolates from patients with meningococcal meningitis were examined. In all unencapsulated strains analysed we found an insertion or deletion within the oligo-(dC) stretch within siaD, resulting in a frameshift and loss of capsule formation. All encapsulated isolates, however, had seven dC residues at this position, indicating a correlation between capsule phase variation and bacterial invasion and the out-break of meningococcal disease. 相似文献
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