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A Campylobacter jejuni homolog of the LcrD/FlbF family of proteins is necessary for flagellar biogenesis.

ABSTRACT: A Campylobacter jejuni homolog of the lcrD/flbF family of genes was cloned and sequenced. The nucleotide sequence of the gene, called flbA, predicted a protein of 78,864 Da, with significant homology to a group of related proteins including the Yersinia pestis LcrD, Salmonella typhimurium InvA, and Caulobacter crescentus FlbF proteins. The greatest homology was seen with the C. crescentus FlbF protein, with an overall amino acid sequence homology of 57%. An insertion mutation in the C. jejuni 81-176 flbA gene was constructed. The resultant strain did not synthesize flagellin and was nonmotile.

SUBMITTER: Miller S

PROVIDER: S-EPMC280941 | biostudies-other | 1993 Jul

REPOSITORIES: biostudies-other

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A Campylobacter jejuni homolog of the LcrD/FlbF family of proteins is necessary for flagellar biogenesis.

Miller S S Pesci E C EC Pickett C L CL

Infection and immunity 19930701 7

A Campylobacter jejuni homolog of the lcrD/flbF family of genes was cloned and sequenced. The nucleotide sequence of the gene, called flbA, predicted a protein of 78,864 Da, with significant homology to a group of related proteins including the Yersinia pestis LcrD, Salmonella typhimurium InvA, and Caulobacter crescentus FlbF proteins. The greatest homology was seen with the C. crescentus FlbF protein, with an overall amino acid sequence homology of 57%. An insertion mutation in the C. jejuni 81 ...[more]

PMID: 8514397

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Project description:UNLABELLED:Many polarly flagellated bacteria require similar two-component regulatory systems (TCSs) and ?(54) to activate transcription of genes essential for flagellar motility. Herein, we discovered that in addition to the flagellar type III secretion system (T3SS), the Campylobacter jejuni flagellar MS ring and rotor are required to activate the FlgSR TCS. Mutants lacking the FliF MS ring and FliG C ring rotor proteins were as defective as T3SS mutants in FlgSR- and ?(54)-dependent flagellar gene expression. Also, FliF and FliG required each other for stability, which is mediated by atypical extensions to the proteins. A FliF mutant that presumably does not interact with the T3SS protein FlhA did not support flagellar gene transcription, suggesting that FliF-T3SS interactions are essential to generate a signal sensed by the cytoplasmic FlgS histidine kinase. Furthermore, the flagellar T3SS was required for FlgS to immunoprecipitate with FliF and FliG. We propose a model whereby the flagellar T3SS facilitates FliF and FliG multimerization into the MS ring and rotor. As a result, these flagellar structures form a cytoplasmic complex that interacts with and is sensed by FlgS. The synthesis of these structures appears to be a regulatory checkpoint in flagellar biogenesis that the FlgS kinase monitors to initiate signal transduction that activates ?(54) and expression of genes required for the next stage of flagellation. Given that other polar flagellates have flagellar transcriptional hierarchies that are organized similarly as in C. jejuni, this regulatory checkpoint may exist in a broad range of bacteria to influence similar TCSs and flagellar gene transcription. IMPORTANCE:Despite the presence of numerous two-component regulatory systems (TCSs) in bacteria, direct signals sensed by TCSs to activate signal transduction are known for only a minority. Polar flagellates, including Pseudomonas, Vibrio, Helicobacter, and Campylobacter species, require a similar TCS and ?(54) for flagellar gene transcription, but the activating signals for these TCSs are unknown. We explored signals that activate the Campylobacter jejuni FlgSR TCS to initiate ?(54)-dependent flagellar gene transcription. Our discoveries suggest that the FlgS histidine kinase monitors the formation of the flagellar type III secretion system and the surrounding MS and C rings. The synthesis of these structures creates a regulatory checkpoint in flagellar biogenesis that is sensed by FlgS to ensure proper transcription of the next set of genes for subsequent steps in flagellation. Given the conservation of flagellar-associated TCSs and transcriptional cascades in polar flagellates, this regulatory checkpoint in flagellar biogenesis likely impacts flagellation in a broad range of bacteria.

Project description:Spatial and numerical regulation of flagellar biosynthesis results in different flagellation patterns specific for each bacterial species. Campylobacter jejuni produces amphitrichous (bipolar) flagella to result in a single flagellum at both poles. These flagella confer swimming motility and a distinctive darting motility necessary for infection of humans to cause diarrheal disease and animals to promote commensalism. In addition to flagellation, symmetrical cell division is spatially regulated so that the divisome forms near the cellular midpoint. We have identified an unprecedented system for spatially regulating cell division in C. jejuni composed by FlhG, a regulator of flagellar number in polar flagellates, and components of amphitrichous flagella. Similar to its role in other polarly-flagellated bacteria, we found that FlhG regulates flagellar biosynthesis to limit poles of C. jejuni to one flagellum. Furthermore, we discovered that FlhG negatively influences the ability of FtsZ to initiate cell division. Through analysis of specific flagellar mutants, we discovered that components of the motor and switch complex of amphitrichous flagella are required with FlhG to specifically inhibit division at poles. Without FlhG or specific motor and switch complex proteins, cell division occurs more often at polar regions to form minicells. Our findings suggest a new understanding for the biological requirement of the amphitrichous flagellation pattern in bacteria that extend beyond motility, virulence, and colonization. We propose that amphitrichous bacteria such as Campylobacter species advantageously exploit placement of flagella at both poles to spatially regulate an FlhG-dependent mechanism to inhibit polar cell division, thereby encouraging symmetrical cell division to generate the greatest number of viable offspring. Furthermore, we found that other polarly-flagellated bacteria produce FlhG proteins that influence cell division, suggesting that FlhG and polar flagella may function together in a broad range of bacteria to spatially regulate division.

Dataset Information

A Campylobacter jejuni homolog of the LcrD/FlbF family of proteins is necessary for flagellar biogenesis.

Publications

A Campylobacter jejuni homolog of the LcrD/FlbF family of proteins is necessary for flagellar biogenesis.

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