SOS genes contribute to Bac8c induced apoptosis-like death in Escherichia coli

Antimicrobial peptides are one of the promising substitutes for conventional antibiotics. To examine their potential usefulness for controlling bacterial infections, the present study aimed to determine the induction of the self-destruction of Escherichia coli mediated by bac8c, which was modified from template peptide bactenecin. The potential of bac8c (RIWVIWRR) was reflected by the change in physiological following exposure, which led to the accumulation of reactive oxygen species (ROS) with an imbalance in the antioxidant system and damage to the intracellular lipids. In addition, bac8c-mediated death exhibited typical features to bacterial apoptosis-like death (ALD). The pathway was not enhanced in the absence of autocleavage of RecA and LexA, the SOS response proteins. We observed that elevated levels of intracellular ROS induced ALD, but this effect was insufficient before preceding RecA activation and LexA autocleavage. Furthermore, dinF, which encodes a member of the toxic compound extrusion (MATE) family, was evaluated to examine the role of the ALD pathway. dinF protein was required to accelerate the ALD-mediated bac8c in combination with RecA. Taken together, bac8c-mediated cell death underlies the severe SOS response, leading to RecA activation, LexA proteolysis, and dinF overexpression. Since then, overproduction of intracellular ROS facilitated the cell death.