Ultraviolet-B inhibition of motility in green and dark bleachedEuglena gracilis |
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Authors: | Dr Donat-P Häder Maria A Häder |
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Institution: | (1) Department of Botany, Friedrich-Alexander-Universität, Erlangen, FRG |
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Abstract: | The motility of green and dark bleachedEuglena gracilis was studied under artificial and solar UV-B radiation. The percentage of motile cells in the population was drastically impaired after exposure to unfiltered sunlight for only a few hours. Dark bleached cells were even more affected than green organisms. The effect is caused mainly by the solar UV-B component, since filtering the sunlight by either a layer of ozone or a UV-B-absorbing filter substantially increased the survival rate. Addition ofp-quinone, a scavenger of free radicals produced in a type I photodynamic reaction, did not relieve the UV-B effects, but was cytotoxic at higher concentrations. Likewise, 1,4-diazobicyclo2,2,2]octane and imidazole, which quench singlet oxygen (1O2) generated in a type II photodynamic reaction, did not prolong the survival in UV-B irradiation. D2O, which, in contrast, prolongs the lifetime of1O2, is tolerated by the cells but does not aggravate the UV-B inhibition. Thus, photodynamic processes of both type I and II can be ruled out as possible mechanisms of UV-B inhibition of motility inEuglena gracilis. |
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