ssrA (tmRNA) plays a role in Salmonella enterica serovar Typhimurium pathogenesis

Escherichia coli ssrA encodes a small stable RNA molecule, tmRNA, that has many diverse functions, including tagging abnormal proteins for degradation , supporting phage growth, and modulating the activity of DNA binding prote ins. Here we show that ssrA plays a role in Salmonella enterica serovar Typ himurium pathogenesis and in the expression of several genes known to be in duced during infection, Moreover, the phage-like attachment site, attL, enc oded within ssrA, serves as the site of integration of a region of Salmonel la-specific sequence; adjacent to the 5' end of ssrA is another region of S almonella-specific sequence with extensive homology to predicted proteins e ncoded within the unlinked Salmonella pathogenicity island SPI4. S. enteric a serovar Typhimurium ssrA mutants fail to support the growth of phage P22 and are delayed in their ability to form viable phage particles following i nduction of a phage P22 lysogen, These data indicate that ssrA plays a role in the pathogenesis of Salmonella, serves as an attachment site for Salmon ella-specific sequences, and is required for the growth of phage P22.