Effect of a loss-of-function mutation in sicP on the expression of sptP. The levels of C2,3O in S. typhimurium SB550, which carries an sptP::xylE gene fusion, and in its derivative strain SB748, which carries a loss-of-function mutation in sicP, were measured as indicated in Materials and Methods. Units are expressed as micromoles of C2,3O per minute per microgram of protein.