Far-infrared irradiation-induced injuries to Escherichia coli at below the lethal temperature

Abstract

in phosphate-buffered saline irradiated with far-infrared (FIR) energy was injured and killed even under the condition where the bulk temperature of the suspension was maintained below the lethal temperature. Using four kinds of antibiotics (penicillin G, chloramphenicol, nalidixic acid and rifampicin), we investigated the FIR irradiation-induced damage to E. coli on the basis of the sensitivity changes to the antibiotics. FIR irradiation increased the organism’s sensitivity to rifampicin both below and above the lethal temperature. The increase in sensitivity to chloramphenicol was observed only when FIR irradiation occurred above the lethal temperature. These results suggest that the mechanism of FIR irradiation-induced death in E. coli differs according to whether the radiation exposure occurs above or below the lethal temperature. Journal of Industrial Microbiology & Biotechnology (2000) 24, 19–24.