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The interaction dynamics of a negative feedback loop regulates flagellar number in Salmonella enterica serovar Typhimurium

Lookup NU author(s): Christine Aldridge, Kritchai Poonchareon, Dr Phillip AldridgeORCiD


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P>Each Salmonella enterica serovar Typhimurium cell produces a discrete number of complete flagella. Flagellar assembly responds to changes in growth rates through FlhD(4)C(2) activity. FlhD(4)C(2) activity is negatively regulated by the type 3 secretion chaperone FliT. FliT is known to interact with the flagellar filament cap protein FliD as well as components of the flagellar type 3 secretion apparatus. FliD is proposed to act as an anti-regulator, in a manner similar to FlgM inhibition of sigma 28 activity. We have found that efficient growth-dependent regulation of FlhD(4)C(2) requires FliT regulation. In turn, FliD regulation of FliT modulates the response. We also show that, unlike other flagellar-specific regulatory circuits, deletion of fliT or fliD did not lead to an all-or-nothing response in FlhD(4)C(2) activity. To investigate why, we characterized the biochemical interactions in the FliT : FliD : FlhD(4)C(2) circuit. When FlhD(4)C(2) was not bound to DNA, FliT disrupted the FlhD(4)C(2) complex. Interestingly, when FlhD(4)C(2) was bound to DNA it was insensitive to FliT regulation. This suggests that the FliT circuit regulates FlhD(4)C(2) activity by preventing the formation of the FlhD(4)C(2):DNA complex. Our data would suggest that this level of endogenous regulation of FlhD(4)C(2) activity allows the flagellar system to efficiently respond to external signals.

Publication metadata

Author(s): Aldridge C, Poonchareon K, Saini S, Ewen T, Soloyva A, Rao CV, Imada K, Minamino T, Aldridge PD

Publication type: Article

Publication status: Published

Journal: Molecular Microbiology

Year: 2010

Volume: 78

Issue: 6

Pages: 1416-1430

Print publication date: 14/10/2010

ISSN (print): 0950-382X

ISSN (electronic): 1365-2958

Publisher: Wiley-Blackwell Publishing Ltd.


DOI: 10.1111/j.1365-2958.2010.07415.x


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Funder referenceFunder name
Diawa Foundation
Royal Society (UK)
Ministry of Education, Science and Culture of Japan
Nareasuan University (Thailand)
CBET 0644744National Science Foundation
GM083601Public Health Service
GM054365Public Health Service