A probable ATP-dependent RNA helicase with RNA-dependent ATPase activity. Involved in regulation of biofilm formation and hemolysis via its effects on stability of mRNA from the agrBDCA operon. Also involved in response to cold stress. ATP + H2O = ADP + H(+) + phosphate kcat 140 min(-1), in strain S30. Homodimer (Probable). Component of a possible RNA degradosome complex composed of cshA, eno, pfkA, pnp, rnjA, rnjB, rnpA and rny. Interacts specifically with enolase, phosphofructokinase and RNases RnpA and Y. In strain S30, cold-sensitive; decreased growth at 30 degrees Celsius, no growth at 20 degrees Celsius. Reduced biofilm formation, increased hemolytic activity, increased stability of mRNAs of the agrBDCA operon. A double agrA-cshA mutation has wild-type biofilm and hemolytic activity (all phenotypes in strain S30). All disruption phenotypes were also seen for deletion in strain SA564. Belongs to the DEAD box helicase family. CshA subfamily.