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  • 1
    Electronic Resource
    Electronic Resource
    Behavioural responses of bacteria to light and oxygen (1997)
    Springer
    Archives of microbiology 168 (1997), S. 249-261 
    Details
    ISSN: 1432-072X
    Keywords: Key words Bacterial behaviour ; Bacterial motility ; Aerotaxis ; Photoresponses ; Photoaxis ; Chemotaxis ; Electron transport ; Flagella
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Motile bacteria have long been known to swim towards or away from specific environmental stimuli such as nutrients, oxygen or light. Although there has been a detailed description of chemosensory responses in enteric species for several years, there has been little information on the mechanisms involved in responses to stimuli affecting electron transport as these usually also change the electrochemical proton gradient – at least transiently – and, thus, directly change flagellar rotation. There have, however, been major advances recently. Halobacterium salinarium uses a retinal-based sensory system to sense changes in specific wavelengths of light and to signal via a transmembrane sensory protein, which turns out to be homologous to the transmembrane chemoreceptors of Escherichia coli. A FAD-binding protein, also related to these receptors, signals changes in respiratory electron transport in E. coli. Rhodobacter sphaeroides cells do not respond to light or oxygen specifically, but sense a change in the rate of electron transfer, probably again using an electron-transport-chain-linked redox sensor, signalling through a common sensory pathway. These recent studies reveal that bacteria not only sense a range of environmental stimuli but also integrate the signals through common pathways to produce a balanced flagellar response.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002030050496
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Swimming changes and chemotactic responses in Rhodobacter sphaeroides do not involve changes in the steady state membrane potential or respiratory electron transport (1990)
    Springer
    Archives of microbiology 153 (1990), S. 614-618 
    Details
    ISSN: 1432-072X
    Keywords: Motility ; Chemotaxis ; Rhodobacter sphaeroides ; Membrane potential ; Electron transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of the chemoattractants acetate, propionate, pyruvate and potassium on the steady state membrane potential and the rate of respiratory electron transport was examined in Rhodobacter sphaeroides. Under conditions where the membrane potential makes up most of the proton motive force, all attractants increased the steady state membrane potential in the dark. However, only potassium was able to consistently increase the steady state membrane potential in the light. All of the attractants were able to increase the mean swimming speed of cells at high light levels for prolonged periods, showing that the increase in mean speed cannot be caused by an increase in the membrane potential. Measurement of chemotaxis in wells showed a positive response to propionate in the dark, at low light (10 – 20 μmol photons m−2 s−1) and in high light (700 μmol photons m−2 s−1). The demonstration of chemotaxis in the dark precluded any direct role of photosynthetic electron transport in chemotaxis. The response at high light, where there was no induced change in membrane potential, confirmed that the steady state membrane potential was not involved in tactic signalling. Acetate, propionate and pyruvate at appropriate concentrations stimulated the rate of respiratory electron transport in the dark, while potassium had no effect. In low light, all three organic acids caused a significant stimulation of respiratory electron transport but potassium caused a significant inhibition. In high light, only pyruvate and propionate caused a significant increase in the rate of respiratory electron transport. Chemoattractants can therefore produce a significant positive tactic response when respiratory electron transport is either unaffected or inhibited. These data show that neither a change in the bulk steady state membrane potential nor the rate of respiratory electron transport causes either the change in swimming behaviour or acts as a chemotactic signal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00245274
    Location Call Number Limitation Availability
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    Paper (German National Licenses)
    Fulltext
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