Involvement of 6S RNA in Oxidative Stress Response.

6S RNA, a small non-coding RNA present in almost all bacteria, inhibits transcription via direct binding to RNA polymerase holoenzymes. The mechanism of 6S RNA action was investigated to a large extent in , however, lack of 6S RNA (Δ) was demonstrated to be unfavorable but not essential for cell survival under various growth conditions. In the present study, we revealed, for the first time, a lethal phenotype of the Δ strain in the presence of high concentrations of HO. This phenotype was rescued by complementation of the gene on a plasmid. We performed comparative qRT-PCR analyses on an enlarged set of mRNAs of genes associated with the oxidative stress response, allowing us to identify four genes known to be involved in this pathway (, , and ) that had decreased mRNA levels in the Δ strain. Finally, we performed comparative proteomic analyses of the wild-type and Δ strains, confirming that Δ bacteria have reduced levels of the proteins AhpC and Tpx involved in HO reduction. Our findings substantiate the crucial role of the riboregulator 6S RNA for bacterial coping with extreme stresses.