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Chapter 79 : Gene Expression and Virulence in : the Flagellar Regulon

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Gene Expression and Virulence in : the Flagellar Regulon, Page 1 of 2

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Abstract:

In this chapter, the authors aimed to characterize the cascade of regulation to obtain more information about mechanisms of gene regulation and about virulence of . To analyze the cascade of flagellar gene regulation, the authors identified, cloned and characterized the regulators which may be involved in regulation. Specific mutants of the identified regulators were generated and analyzed for flagellar gene expression. The authors also showed, that the sigma-54 activator protein FleQ is the master regulator of the flagellar regulon. Recently, the ability to analyze flagellar gene expression by transcriptome analysis using wild-type strain Paris and the isogenic mutant strain was developed. The regulation of the flagellum is linked to the expression of the virulent phenotype of . Phenotypic characteristics which are associated with the virulence of have the ability to lyse human erythrocytes, to infect host cells, and to replicate inside host cells. It was shown recently that mutations in Toll-like receptor 5, which mediates the flagellin-dependant recognition of bacteria by the innate immune system in humans, is associated with the incidence of infection. These results together indicate that various phenotypes associated with the flagellar regulon are of importance for virulence of , demonstrating the importance of research into the flagellar regulon.

Citation: Heuner K, Jacobi S, Albert C, Steinert M, Brüggemann H, Buchrieser C. 2006. Gene Expression and Virulence in : the Flagellar Regulon, p 327-332. In Cianciotto N, Kwaik Y, Edelstein P, Fields B, Geary D, Harrison T, Joseph C, Ratcliff R, Stout J, Swanson M (ed), . ASM Press, Washington, DC. doi: 10.1128/9781555815660.ch79

Key Concept Ranking

Legionella pneumophila
0.45815694
Innate Immune System
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Figures

Image of FIGURE 1
FIGURE 1

Schematic drawing of a flagellum and the flagellar operon structure of Paris (modified from reference ). Underlined genes are found together in one chromosomal region. Bars represent the direction of putative operons in I to IV, classes of the regulatory cascade (see also Fig. 2 ); black dot, σ promoter element; white dot, σ promoter element; grey dot, σ promoter element; grey square, class III promoter, putatively FleR/RpoN-dependant; IM, inner membrane; OM, outer membrane; PG, peptidoglycan layer.

Citation: Heuner K, Jacobi S, Albert C, Steinert M, Brüggemann H, Buchrieser C. 2006. Gene Expression and Virulence in : the Flagellar Regulon, p 327-332. In Cianciotto N, Kwaik Y, Edelstein P, Fields B, Geary D, Harrison T, Joseph C, Ratcliff R, Stout J, Swanson M (ed), . ASM Press, Washington, DC. doi: 10.1128/9781555815660.ch79
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Image of FIGURE 2
FIGURE 2

Proposed cascade of the flagellar regulon of cascade was generated from data retrieved by analyzing flagellar mutant strains and by transcriptome analysis (see text). FleQ is the master regulator of the flagellar genes. FliA seems to be transcribed independently of FleQ and is the direct regulator of the class IV genes. Dotted bars represent an unknown mode of regulation (direct or indirect). *, indicates regulation activity has to be approved by experiments using specific mutant strains; +, positive regulation; ∼, negative regulation; CsrA, carbon storage regulator; FlaA, flagellin; FlaR, transcriptional regulator (LysR family); FleQ and FleR, σ activator protein; FliA, alternative σ factor; LetA and LetS, two-component system; RpoN, alternative σ factor; RpoS, alternative sigma factor. (modified from references and ).

Citation: Heuner K, Jacobi S, Albert C, Steinert M, Brüggemann H, Buchrieser C. 2006. Gene Expression and Virulence in : the Flagellar Regulon, p 327-332. In Cianciotto N, Kwaik Y, Edelstein P, Fields B, Geary D, Harrison T, Joseph C, Ratcliff R, Stout J, Swanson M (ed), . ASM Press, Washington, DC. doi: 10.1128/9781555815660.ch79
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Image of FIGURE 3
FIGURE 3

Hemolysis assay of sheep red blood cells with different flagellar mutant strains at postexponential phase. The contact-dependent hemolysis assay was carried out at different time points during growth as stated recently ( ), but the incubation time was reduced to 4 h. Hemolysis values of different mutants are expressed as a percentage of hemolysis by wild-type Corby (defined as 100%). Corby and JR32 wild-type strains and mutant strain (black columns); flagellar mutant strains and mutant (white columns); complemented strains with the corresponding gene (striped columns). A minimum of three independent experiments in triplicate were performed. Error bars represent standard deviation. Asterisks represent values for mutant strains statistically different from wild-type hemolysis with a value of < 0.05 as determined with the two-sided Student’s /-test.

Citation: Heuner K, Jacobi S, Albert C, Steinert M, Brüggemann H, Buchrieser C. 2006. Gene Expression and Virulence in : the Flagellar Regulon, p 327-332. In Cianciotto N, Kwaik Y, Edelstein P, Fields B, Geary D, Harrison T, Joseph C, Ratcliff R, Stout J, Swanson M (ed), . ASM Press, Washington, DC. doi: 10.1128/9781555815660.ch79
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References

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