Enterohaemorrhagic E. coli (EHEC) is a pathotype of E. coli that causes outbreaks of haemorrhagic colitis and potentially fatal haemolytic uremic syndrome. The later is caused by the release of Shiga toxins encoded on lambdoid bacteriophage (Stx phage). Shiga toxins are transcribed from the phage later promoter (PR’) and are expressed during lytic induction of the bacteriophage. Previous work has shown that the Stx phages harbour at least 12 Hfq-dependent regulatory small RNAs (sRNAs). Here we demonstrate that under lysogenic conditions the Shiga toxin promoter PR’ transcribes a 214nt regulatory sRNA that terminates at tR’ (designated EcOnc65). The 214nt transcript is processed by RNase E into a functional 74nt sRNA that binds the sRNA chaperone, Hfq. Using sRNA interactome datasets (RNase E-CLASH), we have found that EcOnc65 interacts with the 5’ leader region of the stationary phase and general stress response sigma factor, RpoS. We have verified this interaction using MS2 affinity purification coupled with RNA sequencing (MAPS). Furthermore, using GFP translational fusions, we have shown that the interaction of EcOnc65 with RpoS causes a 5-fold activation of rpoS translation, indicating that EcOnc65 plays a role in adapting EHEC to stress. RpoS has previously been implicated in the regulation of the Stx2 phage and toxin release in EHEC, suggesting that EcOnc65 may modulate lytic induction of Stx phages. We are currently testing this hypothesis in ∆econc65 and ∆econc15 backgrounds. Shiga toxins protect EHEC from protozoan grazing in the environment and we are also testing survival of the ∆econc65 mutant in a protozoan predation model. The ability of EcOnc65 to modulate the RpoS stress response will have impacts on the virulence of EHEC and may also indirectly modulate Shiga toxin production.