Upon completion of the basal body , the anti-sigma factor FlgM is secreted , allowing the alternative sigma factor FliA to initiate transcription of genes under control of fliC .
In this investigation , we observed that ( i ) the in-vitro generation times of flgM mutant and wild-type strains of S. typhimurium were indistinguishable , as were the amounts of flagellin produced by the strains ; ( ii ) the 50 % lethal doses of fliA mutant and wild-type strains of S. typhimurium were similar in orally infected mice ; and ( iii ) inactivation of the FliA-regulated flagellin gene fliC in an flgM S. typhimurium mutant resulted in a virulent phenotype .