Radio- and thermosensitivity of E. coli K1060 after thiol depletion by diethylmaleate.

The Escherichia coli auxotroph K1060 has been grown in a medium supplemented with either oleic acid (18:1) or linolenic acid (18:3) and its radiosensitivity and thermosensitivity established using bacterial cell survival as the assay system. No difference in radiosensitivity was observed when oleic and linolenic grown cells were exposed to gamma-radiation at room temperature. When heated at 49 degrees C linolenic grown cells were more sensitive than oleic grown cells. To investigate whether soluble -SH compounds, e.g., glutathione (GSH), were critical in protecting cells against radiation or heat, studies were performed using cells depleted of -SH by incubation with diethylmaleate (DEM). After reduction of water-soluble non-protein thiol compounds to 25% (10 mM DEM treatment) of control value, no major changes in radiosensitivity under oxic conditions were found. Radioresistance increased slightly when irradiation was performed under hypoxic conditions. Thermoresistance was clearly stimulated after DEM treatments between 1 and 10 mM DEM. The main conclusion of these experiments is that lowering the cellular level of reduced glutathione may not generally be correlated with a higher radio- and thermosensitivity.