Exposure of Escherichia coli to intestinal myoelectrical activity-related electric field induces resistance against subsequent UV254nm (UVC) irradiation

Survival of Escherichia coli K-12 AB 1157 irradiated with INC (UV254nm) was enhanced after pre-treatment with a low-tension electric field (EF). The E F used was identical to the electrical field generated by the small intesti ne (myoelectrical migrating complex - MMC), registered in a healthy calf an d transmitted into the memory of an EF generator. The EF emitted by the gen erator was transmitted via electrodes placed in shaken bacterial cultures. The protective effects of the EF on the E. coli survival after exposure to UV were: (i) observed only for the dnaJ(+)dnaK(+) strain, and not for the D elta dnaJdnaK heat shock mutant; (ii) strictly dependent on the temperature at which the bacteria were grown; (iii) most obvious when the bacteria wer e incubated at 37 degreesC. Moreover, the MMC-related EF and a higher tempe rature (40 degreesC) show a similar protective effect against UV-irradiatio n. The results point to the involvement of the heat shock response in the l ow-tension EF-induced protection of bacterial cells against UVC-irradiation . Additionally, treatment with the MMC-related EF affects total protein con tents and their pattern in E. coli cells. The EF-treatment did not show any influence on the level of the argE3(ochre) --> Arg(+) reversions. (C) 2001 Elsevier Science B.V. All rights reserved.