Enhanced UV sensitivity of Thiobacillus ferrooxidans resulting from caffeine and acriflavine treatment of irradiated cells

This study was aimed at identifying the roles of caffeine and acriflavine, two repair inhibitors, on UV sensitivity of iron-oxidizing Thiobacillus fer rooxidans ATCC 13728. The UV-dose response survival curve was inflected in nature, suggesting the population heterogeneity of the isolate. Caffeine an d acriflavine potentiated the UV-induced killing of the organism. With the increase in concentrations of these compounds. the extent of survival decre ased. Similarly, the inhibitory effects of caffeine and acriflavine increas ed with the increase in dose of UV-irradiation. The cells irradiated with 1 0 s (equivalent to 5.6 x 10(-5) J/m(2)/s) of UV-exposure tended to become r esistant to the inhibitory effects of caffeine and acriflavine, as evidence d by the time course study of recovery. The cells appear to stage a dramati c recovery from UV damage in the presence of caffeine (3.0 mg/ml) and acrif lavine (20 mug/ml) over a period of 25-30h and 35-40h respectively, when gr own in the presence of energy sources.