Peculiarities of the regulation of the Brucella flagellum

Cornélis, Pierre

doi:10.1099/mic.0.049635-0

Cited by 3 publications

(3 citation statements)

References 19 publications

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“…This indicates that Las flagellin is functional and may be involved in filament production within Las. Although a Las flagellum has not yet been observed, our results imply that the Las bacterium may produce a functional flagellum in certain stages of its life as do other member of the order Rhizobiales, such as Brucella meltinsis that produces a polar flagellum transiently at the end of the exponential growth phase [24]. As with most other members of the Rhizobiacea, Las retains a complete set of flagellar biosynthesis genes despite having a significantly reduced genome (Fig.…”

Section: Discussionmentioning

confidence: 73%

The Destructive Citrus Pathogen, ‘Candidatus Liberibacter asiaticus’ Encodes a Functional Flagellin Characteristic of a Pathogen-Associated Molecular Pattern

et al. 2012

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Huanglongbing (HLB) is presently the most devastating citrus disease worldwide. As an intracellular plant pathogen and insect symbiont, the HLB bacterium, ‘Candidatus Liberibacter asiaticus’ (Las), retains the entire flagellum-encoding gene cluster in its significantly reduced genome. Las encodes a flagellin and hook-associated protein (Fla) of 452 amino acids that contains a conserved 22 amino acid domain (flg22) at positions 29 to 50 in the N-terminus. The phenotypic alteration in motility of a Sinorhizobium meliloti mutant lacking the fla genes was partially restored by constitutive expression of FlaLas. Agrobacterium-mediated transient expression in planta revealed that FlaLas induced cell death and callose deposition in Nicotiana benthamiana, and that the transcription of BAK1 and SGT1, which are associated with plant innate immunity, was upregulated. Amino acid substitution experiments revealed that residues 38 (serine) and 39 (aspartate) of FlaLas were essential for callose induction. The synthetic flg22Las peptide could not induce plant cell death but retained the ability to induce callose deposition at a concentration of 20 µM or above. This demonstrated that the pathogen-associated molecular pattern (PAMP) activity of flg22 in Las was weaker than those in other well-studied plant pathogenic bacteria. These results indicate that FlaLas acts as a PAMP and may play an important role in triggering host plant resistance to the HLB bacteria.

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Section: Discussionmentioning

confidence: 73%

The Destructive Citrus Pathogen, ‘Candidatus Liberibacter asiaticus’ Encodes a Functional Flagellin Characteristic of a Pathogen-Associated Molecular Pattern

et al. 2012

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“…As the flagellum is potentially an adhesive structure, it would be interesting to observe if this appendage is localized at the new or the old pole in Brucella. One of the most surprising observations with regard to the Brucella flagellar genes is the absence of classical genes encoding the membrane chemoreceptors, proteins of the signal transduction pathway and the flagellar motor [12]. Moreover, the deletant strains for ftcR, fliF, flgE and fliC flagellar genes still produce an empty sheated structure [19].…”

Section: The Flagellum Of Brucellamentioning

confidence: 99%

The Brucella pathogens are polarized bacteria

Henst

Barsy

Zorreguieta

et al. 2013

Microbes and Infection

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“…Interestingly, the B. melitensis 16M Δ ftcR strain was defective in the production of FlgE and FliC flagellar proteins, and fliF promoter activity was reduced during vegetative growth compared to that of the wild-type (WT) strain [ 22 ]. Moreover, observing the Δ ftcR strain using electron microscopy revealed a major defect in the flagellar structure under growth conditions in which the WT strain was flagellated, suggesting that FtcR is a key regulator required for switching flagellar gene expression in Brucella [ 22 , 23 , 24 ]. Genomic sequencing of isolated, non-motile Brucella has detected nonfunctional flagellar genes [ 24 ].…”

Section: Introductionmentioning

confidence: 99%

The Flagellar Transcriptional Regulator FtcR Controls Brucella melitensis 16M Biofilm Formation via a betI-Mediated Pathway in Response to Hyperosmotic Stress

Guo

Deng

Song

et al. 2022

IJMS

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The expression of flagellar proteins in Brucella species likely evolved through genetic transference from other microorganisms, and contributed to virulence, adaptability, and biofilm formation. Despite significant progress in defining the molecular mechanisms behind flagellar gene expression, the genetic program controlling biofilm formation remains unclear. The flagellar transcriptional factor (FtcR) is a master regulator of the flagellar system’s expression, and is critical for B. melitensis 16M’s flagellar biogenesis and virulence. Here, we demonstrate that FtcR mediates biofilm formation under hyperosmotic stress. Chromatin immunoprecipitation with next-generation sequencing for FtcR and RNA sequencing of ftcR-mutant and wild-type strains revealed a core set of FtcR target genes. We identified a novel FtcR-binding site in the promoter region of the osmotic-stress-response regulator gene betI, which is important for the survival of B. melitensis 16M under hyperosmotic stress. Strikingly, this site autoregulates its expression to benefit biofilm bacteria’s survival under hyperosmotic stress. Moreover, biofilm reduction in ftcR mutants is independent of the flagellar target gene fliF. Collectively, our study provides new insights into the extent and functionality of flagellar-related transcriptional networks in biofilm formation, and presents phenotypic and evolutionary adaptations that alter the regulation of B. melitensis 16M to confer increased tolerance to hyperosmotic stress.

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Peculiarities of the regulation of the Brucella flagellum

Cited by 3 publications

References 19 publications

The Destructive Citrus Pathogen, ‘Candidatus Liberibacter asiaticus’ Encodes a Functional Flagellin Characteristic of a Pathogen-Associated Molecular Pattern

The Destructive Citrus Pathogen, ‘Candidatus Liberibacter asiaticus’ Encodes a Functional Flagellin Characteristic of a Pathogen-Associated Molecular Pattern

The Brucella pathogens are polarized bacteria

The Flagellar Transcriptional Regulator FtcR Controls Brucella melitensis 16M Biofilm Formation via a betI-Mediated Pathway in Response to Hyperosmotic Stress

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