Previous research shows that some sRNAs directly or indirectly regulate virulence genes, or affect adaptive stress responses that are important for bacterial survival in a host. Several studies indicate that many sRNAs are involved in bacterial pathogenesis, including, RNAIII of S. aureus and CsrBCD of V. cholerae. These sRNAs adapt the expression of virulence genes to stress and metabolic requirements. Padalon-Brauch TASIN-1 hydrochloride pointed out that genetic islands encoding sRNA genes play an important role in networks that regulate bacterial adaptation to environmental changes and stress conditions, thereby controlling virulence. However, very little is known about Shigella sRNAs. Approximately 60 sRNAs are known, but the function of only two sRNAs has been studied in Shigella. The S. flexneri virulence gene icsA is critical for the intra- and inter-cellular spreading of the pathogen. This gene encodes an invasion protein, which induces host actin polymerization at one pole of the cell. RnaG is transcribed in cis on the complementary strand of icsA and regulates at the transcriptional level. S. flexneri requires iron for survival and the genes for iron uptake and homeostasis are regulated by the Fur protein. RyhB expression is repressed by Fur. Oglesby et al. showed that the acid sensitivity defect of the S. flexneri fur mutant is due to RyhB repression of ydeP, which encodes a putative oxidoreductase. Murphy & Payne found that RyhB can repress many virulence genes, including those encoding the type III secretion apparatus,GW806742X secreted effector proteins, and specific chaperones. This phenomenon occurs via RyhB-dependent repression of the transcriptional activator VirB and iron is implicated as an environmental factor contributing to the complex regulation of Shigella virulence determinants. We have identified and validated nine novel sRNAs in Shigella by combining sRNA identification with tiled microarray probe correlation analysis, transcriptional terminator prediction, and northern blot analysis, but the function of these sRNAs requires further analysis. We also detected 29 novel sORF candidates in Sf301 and BLASTX indicated that most encoded hypothetical proteins.