A small untranslated RNA which is induced in response to oxidative stress in Escherichia coli. Acts as a global regulator to activate or repress the expression of as many as 40 genes, including the fhlA-encoded transcriptional activator and the rpoS-encoded sigma(s) subunit of RNA polymerase. OxyS is bound by the Hfq protein, that increases the OxyS RNA interaction with its target messages.