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  • 1
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The mechanisms that determine chromosome structure and chromosome partitioning in bacteria are largely unknown. Here we discuss two hypotheses: (i) the structure of the Escherichia coli nucleoid is determined by DNA binding proteins and DNA supercoiling, representing a compaction force on the one hand, and by the coupled transcription/translation/ translocation of plasma membrane and cell wall proteins, representing an expansion force on the other hand; (ii) the two forces are important for the partitioning process of chromosomes.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 191-195 
    ISSN: 0006-3592
    Keywords: control analysis ; Lactococcus lactis ; gene expression ; flux ; oligonucleotide ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In this article, we review some of the expression systems that are available for Metabolic Control Analysis and Metabolic Engineering, and examine their advantages and disadvantages in different contexts. In a recent approach, artificial promoters for modulating gene expression in micro-organisms were constructed using synthetic degenerated oligonucleotides. From this work, a promoter library was obtained for Lactococcus lactis, containing numerous individual promoters and covering a wide range of promoter activities. Importantly, the range of promoter activities was covered in small steps of activity change. Promoter libraries generated by this approach allow for optimization of gene expression and for experimental control analysis in a wide range of biological systems by choosing from the promoter library promoters giving, e.g., 25%, 50%, 200%, and 400% of the normal expression level of the gene in question. If the relevant variable (e.g., the flux or yield) is then measured with each of these constructs, then one can calculate the control coefficient and determine the optimal expression level. One advantage of the method is that the construct which is found to have the optimal expression level is then, in principle, ready for use in the industrial fermentation process; another advantage is that the system can be used to optimize the expression of different enzymes within the same cell. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58:191-195, 1998.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-6881
    Keywords: Oxidative phosphorylation ; respiration ; ATP ; fluxes ; Metabolic Control Analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Strains carrying deletions in theatp genes, encoding the H+-ATPase, were unable to grow on nonfermentable substrates such as succinate, whereas with glucose as the substrate the growth rate of anatp deletion mutant was surprisingly high (some 75–80% of wild-type growth rate). The rate of glucose and oxygen consumption of these mutants was increased compared to the wild-type rates. In order to analyze the importance of the H+-ATPase at its physiological level, the cellular concentration of H+-ATPase was modulated around the wild-type level, using genetically manipulated strains. The control coefficient by the H+-ATPase with respect to growth rate and catabolic fluxes was measured. Control on growth rate was absent at the wild-type concentration of H+-ATPase, independent of whether the substrate for growth was glucose or succinate. Control by the H+-ATPase on the catabolic fluxes, including respiration, was negative at the wild-type H+-ATPase level. Moreover, the turnover number of the individual H+-ATPase enzymes increased as the H+-ATPase concentration was lowered. The negative control by the H+-ATPase on catabolism may thus be involved in a homeostatic control of ATP synthesis and, to some extent, explain the zero control by the H+-ATPase onE. coli growth rate.
    Type of Medium: Electronic Resource
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