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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 15 (1995), S. 0 
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: It is crucial to the reproducibility of results and their proper interpretation that the conditions under which experiments are carried out be defined with rigour and consistency, in this review we attempt to clarify the differences and interrelationships among steady, balanced and exponential states of culture growth. Basic thermodynamic concepts are used to introduce the idea of steady-state growth in open, biological systems. The classical, sometimes conflicting, definitions of steady-state and balanced growth are presented, and a consistent terminology is proposed. The conditions under which a culture in balanced growth is also in exponential growth and in steady-state growth are indicated. It is pointed out that steady-state growth always implies both balanced and exponential growth, and examples in which the converse does not hold are described. More complex situations are then characterized and the terminology extended accordingly. This leads to the notion of normal growth and growth that can be synchronous or otherwise unbalanced but still reproducible, and to the condition of approximate steady state manifested by growth in batch culture and by asymmetrically dividing cells, which is analysed in some detail.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 32 (1999), S. 0 
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Bacterial membrane and nucleoids were stained concurrently by the lipophilic styryl dye FM 4-64 [N-(3-triethylammoniumpropyl)-4-(6-(4-(diethylamino)phenyl) hexatrienyl)pyridinium dibromide] and 4′,6-diamidino-2-phenylindole (DAPI), respectively, and studied using fluorescence microscopy imaging. Observation of plasmolysed cells indicated that FM 4-64 stained the inner membrane preferentially. In live Escherichia coli pbpB cells and filaments, prepared on wet agar slabs, an FM 4-64 staining pattern developed in the form of dark bands. In dividing cells, the bands occurred mainly at the constriction sites and, in filaments, between partitioning nucleoids. The FM 4-64 pattern of dark bands in filaments was abolished after inhibiting protein synthesis with chloramphenicol. It is proposed that the staining patterns reflect putative membrane domains formed by DNA–membrane interactions and have functional implications in cell division.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Cell cycle events have been proposed to be triggered by the formation of membrane domains in the process of coupled transcription, translation and insertion (‘transertion’) of nascent membrane and exported proteins. Disruption of domain structure should lead to changes in membrane dynamics. Membrane viscosity of Escherichia coli and Bacillus subtilis decreased after inhibition of protein synthesis by chloramphenicol or puromycin, or of RNA initiation by rifampicin, but not after inhibition of RNA elongation by streptolydigin or amino acid starvation of a stringent strain. The decrease caused by inhibitors of protein synthesis was prevented by streptolydigin if added simultaneously, but was not reversed if added later. The drug-induced decrease in membrane viscosity is energy dependent: it did not happen in KCN-treated cells. All treatments decreasing membrane viscosity also induced nucleoid compaction and fusion. Inhibition of macromolecular synthesis without membrane perturbation caused nucleoids to expand. Changes in membrane dynamics were also displayed during a nutritional shift-down transition that causes imbalance in macromolecular syntheses. The results are consistent with the transertion model, predicting dissipation of membrane domains by termination of protein synthesis or detachment of polysomes from DNA; domain structure is conserved if the transertion process is ‘frozen’.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: To detect and characterize membrane domains that have been proposed to exist in bacteria, two kinds of pyrene-labelled phospholipids, 2-pyrene-decanoyl-phosphatidylethanolamine (PY-PE) and 2-pyrene-decanoyl-phosphatidylglycerol (PY-PG) were inserted into Escherichia coli or Bacillus subtilis membrane. The excimerization rate coefficient, calculated from the excimer-to-monomer ratio dependencies on the probe concentration, was two times higher for PY-PE than for PY-PG at 37°C. This was ascribed to different local concentrations rather than to differences in mobility. The extent of mixing between the two fluorescent phospholipids, estimated by formation of their heteroexcimer, was found very low both in E. coli and B. subtilis, in contrast to model membranes. In addition, these two pyrene derivatives exhibited different temperature phase transitions and different detergent extractability, indicating that the surroundings of these phospholipids in bacterial membrane differ in organization and order. Inhibition of protein synthesis, leading to condensation of nucleoid and presumably to dissipation of membrane domains, indeed resulted in increased formation of heteroexcimers, broadening of phase transitions and equal detergent extractability of both probes. It is proposed that in bacterial membranes these phospholipids are segregated into distinct domains that differ in composition, proteo–lipid interaction and degree of order; the proteo-lipid domain being enriched by PE.
    Type of Medium: Electronic Resource
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