The Role of the Exo-Xis Region in Oxidative Stress-Mediated Induction of Shiga Toxin-Converting Prophages

Abstract EN

Previous studies indicated that these genetic elements could be involved in the regulation of lysogenization and prophage induction processes.

The effects were dramatic in Shiga toxin-converting phage Φ24B after treatment with oxidative stress-inducing agent, hydrogen peroxide, while they were less pronounced in bacteriophage λ and in both phages irradiated with UV.

The hydrogen peroxide-caused prophage induction was found to be RecA-dependent.

Importantly, in hydrogen peroxide-treated E.

coli cells lysogenic for either λ or Φ24B, deletion of the exo-xis region resulted in a significant decrease in the levels of expression of the S.O.S.

regulon genes.

Moreover, under these conditions, a dramatic decrease in the levels of expression of phage genes crucial for lytic development (particularly xis, exo, N, cro, O, Q, and R) could be observed in Φ24B-, but not in λ-bearing cells.

We conclude that genes located in the exo-xis region are necessary for efficient expression of both host S.O.S regulon in lysogenic bacteria and regulatory genes of Shiga toxin-converting bacteriophage Φ24B.