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High sensitivity of Deinococcus radiodurans to photodynamically-produced singlet oxygen
Purpose:
To study the sensitivity of two bacterial cell systems to photodynamic treatment and X-ray irradiation as part of a project to establish efficient procedures for waste water disinfection.
Materials And Methods:
Stationary-phase cells of Deinococcus radiodurans (Gram-positive) and Escherichia coli (Gram-negative) were exposed to visible light in a buffer solution containing up to 5 microg/ml sensitizer rose bengal (RB) and to X-rays at dose rates of 32.8 Gy/min or 14.6 Gy/min, respectively.
Results:
Survival of both cell types decreased with increasing exposure time to visible light and increasing concentration of RB, and therefore with an increase in singlet oxygen production. Surprisingly, D. radiodurans, the most resistant cell system to ionizing radiation, was more sensitive to photodynamic treatment than E. coli by about a factor of 100.
Conclusions:
The main target of singlet oxygen reaction is the cell membrane. The repair of such damage in D. radiodurans is less effective than in E. coli.