Molecular and General Genetics MGG

, Volume 254, Issue 4, pp 440–448

Autogenous and global control of the flagellar master operon, flhD, in Salmonella typhimurium

  • K. Kutsukake

DOI: 10.1007/s004380050437

Cite this article as:
Kutsukake, K. Mol Gen Genet (1997) 254: 440. doi:10.1007/s004380050437


Expression of the flagellar master operon, flhD, is known to be affected by growth conditions and by mutations in a variety of genes. In the present work, the transcriptional control of the Salmonella typhimurium flhD operon was investigated in various genetic backgrounds. First, we examined the effect of mutations in the global regulators cAMP-CRP, H-NS, OmpR and RpoS. Mutations in the cya, crp or hns gene reduced but did not eliminate flhD expression. However, expression was completely inhibited in the cya hns and crp hns double mutants. These results indicate that cAMP-CRP and H-NS independently activate the flhD operon and that maximal expression is attained in the presence of both regulators. On the other hand, the ompR and rpoS mutations did not affect either the motility phenotype or flhD expression. We next examined the expression of a chromosomal flhD-lac fusion gene in the presence of a plasmid carrying the wild-type flhD operon. It was found that under this condition the chromosomal flhD operon was repressed or activated, depending on the intracellular activity of FliA, an alternative sigma factor specific for late flagellar operons. In the absence of FliA or in the presence of both FliA and its cognate anti-sigma factor FlgM, the flhD operon was autogenously repressed, whereas in the flgM mutant background it was autogenously activated in the presence of FliA. This autoregulation was still observed in the crp or hns mutant background, indicating that the autogenous control is achieved by a mechanism that is independent of the cAMP-CRP and H-NS regulatory pathways.

Key words Flagellar master operon   Autogenous regulation   FliA-FlgM regulatory system   cAMP-CRP   H-NS 

Copyright information

© Springer-Verlag Berlin Heidelberg 1997

Authors and Affiliations

  • K. Kutsukake
    • 1
  1. 1.Department of Applied Biochemistry, Faculty of Applied Biological Science, Hiroshima University, Kagamiyama 1-4-4 Higashi-Hiroshima, Hiroshima 739, JapanJP

Personalised recommendations