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Euglena: the photoreceptor system for phototaxis.

J J Wolken

    The Journal of Protozoology
    |November 1, 1977
    PubMed
    Summary

    Researchers explored Euglena

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    Area of Science:

    • Cell Biology
    • Biophysics
    • Photobiology

    Background:

    • Euglena exhibits phototaxis, the ability to move towards or away from light.
    • The precise photoreceptor structures and molecular mechanisms underlying Euglena phototaxis have been a subject of investigation.
    • Understanding these mechanisms can provide insights into sensory biology and light-responsive systems in microorganisms.

    Purpose of the Study:

    • To investigate the ultrastructure of the photoreceptor complex in Euglena responsible for phototaxis.
    • To identify the photoreceptor molecule and elucidate the photochemical processes involved in light detection.
    • To compare the Euglena phototaxis system with known sensory mechanisms.

    Main Methods:

    • Electron microscopy was employed to examine the photoreceptor structures (eyespot, paraflagellar body, flagellum).
    • Optical diffraction and image filtering were used to analyze the paraflagellar body's structure.
    • Microspectrophotometry and biochemical analysis (flavin analysis) were performed to identify the photoreceptor molecule and its spectral properties.

    Main Results:

    • The paraflagellar body was identified as the photoreceptor, possessing a highly ordered crystalline lamellar structure.
    • Optical diffraction suggested the paraflagellar body is composed of rods arranged helically.
    • Action spectra and in situ measurements indicated that a flavoprotein is the photoreceptor molecule, with a photochemical scheme involving photo-excited flavin and cytochrome proposed.

    Conclusions:

    • The photoreceptor structure and photochemistry in Euglena phototaxis are consistent with a flavoprotein acting as the primary photoreceptor.
    • The proposed photochemical model involves flavin and cytochrome, suggesting a sophisticated light-sensing mechanism.
    • The Euglena phototaxis system shares similarities with photoneuro sensory cells, highlighting convergent evolution in sensory biology.

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