Cryo-EM of Caulobacter crescentus FljK flagellar filament
Ontology highlight
ABSTRACT:
SUBMITTER: Elizabeth R Wright
PROVIDER: EMPIAR-12076 | biostudies-other |
REPOSITORIES: biostudies-other
Publications
Atomic-level architecture of <i>Caulobacter crescentus</i> flagellar filaments provide evidence for multi-flagellin filament stabilization.
Sanchez Juan C JC Montemayor Eric J EJ Ploscariu Nicoleta T NT Parrell Daniel D Baumgardt Joseph K JK Yang Jie E JE Sibert Bryan B Cai Kai K Wright Elizabeth R ER
bioRxiv : the preprint server for biology 20230710
Flagella are dynamic, ion-powered machines with assembly pathways that are optimized for efficient flagella production. In bacteria, dozens of genes are coordinated at specific times in the cell lifecycle to generate each component of the flagellum. This is the case for <i>Caulobacter crescentus</i>, but little is known about why this species encodes six different flagellin genes. Furthermore, little is known about the benefits multi-flagellin species possess over single flagellin species, if an ...[more]
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Project description:The bacterial flagellum consists of a long extracellular filament that is rotated by a motor embedded in the cell envelope. While flagellar assembly has been extensively studied,1 the disassembly process remains less well understood. In addition to the programmed flagellar ejection that occurs during the life cycle of Caulobacter crescentus, we and others have recently shown that many bacterial species lose their flagella under starvation conditions, leaving relic structures in the outer membrane.2-7 However, it remains unknown whether the programmed flagellar ejection of C. crescentus leaves similar relics or not. Here, we imaged the various stages of the C. crescentus life cycle using electron cryo-tomography (cryo-ET) and found that flagellar relic subcomplexes, akin to those produced in the starvation-induced process, remain as a result of flagellar ejection during cell development. This similarity suggests that the programmed flagellar ejection of C. crescentus might share a common evolutionary path with the more general, and likely more ancient,3 starvation-related flagellar loss.
| S-EPMC9843737 | biostudies-literature
Project description:The bacterial flagellum is important for motility and adaptation to environmental niches. The sequence of events required for the synthesis of the flagellar apparatus has been extensively studied, yet the events that dictate where the flagellum is placed at the onset of flagellar biosynthesis remain largely unknown. We addressed this question for alphaproteobacteria by using the polarly flagellated alphaproteobacterium Caulobacter crescentus as an experimental model system. To identify candidates for a role in flagellar placement, we searched all available alphaproteobacterial genomes for genes of unknown function that cluster with early flagellar genes and that are present in polarly flagellated alphaproteobacteria while being absent in alphaproteobacteria with other flagellation patterns. From this in silico screen, we identified pflI. Loss of PflI function in C. crescentus results in an abnormally high frequency of cells with a randomly placed flagellum, while other aspects of cell polarization remain normal. In a wild-type background, a fusion of green fluorescent protein (GFP) and PflI localizes to the pole where the flagellum develops. This polar localization is independent of the flagellar protein FliF, whose oligomerization into the MS ring is thought to define the site of flagellar synthesis, suggesting that PflI acts before or independently of this event. Overproduction of PflI-GFP often leads to ectopic localization at the wrong, stalked pole. This is accompanied by a high frequency of flagellum formation at this ectopic site, suggesting that the location of PflI is a sufficient marker for a site for flagellar assembly.
| S-EPMC2258662 | biostudies-literature
Project description:Surface appendages such as flagella and type IV pili mediate a broad range of bacterial behaviors including motility, attachment, and surface sensing. While many species harbor both flagella and type IV pili, little is known about how or if their synthesis is coupled. Here, we show that deletions of genes encoding different flagellum machinery components result in a reduction of pilus synthesis in Caulobacter crescentus. First, we show that different flagellar mutants exhibit different levels of sensitivity to a pilus-dependent phage and that less cells within populations of flagellar mutants make pili. Furthermore, we find that single cells within flagellar mutant populations produce less pili per cell. We demonstrate that these gene deletions result in reduced transcription of pilus-associated genes and have a broad effect on global transcription profiles. Finally, we show that the decrease in pilus production is due to a reduction in the pool of pilin subunits that are polymerized into pilus fibers. These data demonstrate that mutations in flagella gene components affect not only motility but can also have considerable and unexpected consequences on other aspects of cell biology.
2019-07-05 | GSE126478 | GEO
Project description:Bacteria carry out sophisticated developmental programs to colonize exogenous surfaces. The rotary flagellum, a dynamic machine that drives motility, is a key regulator of surface colonization. The specific signals recognized by flagella and the pathways by which those signals are transduced to coordinate adhesion remain subjects of debate. Mutations that disrupt flagellar assembly in the dimorphic bacterium Caulobacter crescentus stimulate the production of a polysaccharide adhesin called the holdfast. Using a genomewide phenotyping approach, we compared surface adhesion profiles in wild-type and flagellar mutant backgrounds of C. crescentus We identified a diverse set of flagellar mutations that enhance adhesion by inducing a hyperholdfast phenotype and discovered a second set of mutations that suppress this phenotype. Epistasis analysis of the flagellar signaling suppressor (fss) mutations demonstrated that the flagellum stimulates holdfast production via two genetically distinct pathways. The developmental regulator PleD contributes to holdfast induction in mutants disrupted at both early and late stages of flagellar assembly. Mutants disrupted at late stages of flagellar assembly, which assemble an intact rotor complex, induce holdfast production through an additional process that requires the MotAB stator and its associated diguanylate cyclase, DgcB. We have assigned a subset of the fss genes to either the stator- or pleD-dependent networks and characterized two previously unidentified motility genes that regulate holdfast production via the stator complex. We propose a model through which the flagellum integrates mechanical stimuli into the C. crescentus developmental program to coordinate adhesion.IMPORTANCE Understanding how bacteria colonize solid surfaces is of significant clinical, industrial and ecological importance. In this study, we identified genes that are required for Caulobacter crescentus to activate surface attachment in response to signals from a macromolecular machine called the flagellum. Genes involved in transmitting information from the flagellum can be grouped into separate pathways, those that control the C. crescentus morphogenic program and those that are required for flagellar motility. Our results support a model in which a developmental and a mechanical signaling pathway operate in parallel downstream of the flagellum and converge to regulate adhesion. We conclude that the flagellum serves as a signaling hub by integrating internal and external cues to coordinate surface colonization and emphasize the role of signal integration in linking complex sets of environmental stimuli to individual behaviors.
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