Dataset Information

The flagellar set Fla2 in Rhodobacter sphaeroides is controlled by the CckA pathway and is repressed by organic acids and the expression of Fla1.

ABSTRACT: Rhodobacter sphaeroides has two different sets of flagellar genes. Under the growth conditions commonly used in the laboratory, the expression of the fla1 set is constitutive, whereas the fla2 genes are not expressed. Phylogenetic analyses have previously shown that the fla1 genes were acquired by horizontal transfer from a gammaproteobacterium and that the fla2 genes are endogenous genes of this alphaproteobacterium. In this work, we characterized a set of mutants that were selected for swimming using the Fla2 flagella in the absence of the Fla1 flagellum (Fla2(+) strains). We determined that these strains have a single missense mutation in the histidine kinase domain of CckA. The expression of these mutant alleles in a Fla1(-) strain allowed fla2-dependent motility without selection. Motility of the Fla2(+) strains is also dependent on ChpT and CtrA. The mutant versions of CckA showed an increased autophosphorylation activity in vitro. Interestingly, we found that cckA is transcriptionally repressed by the presence of organic acids, suggesting that the availability of carbon sources could be a part of the signal that turns on this flagellar set. Evidence is presented showing that reactivation of fla1 gene expression in the Fla2(+) background strongly reduces the number of cells with Fla2 flagella.

SUBMITTER: Vega-Baray B

PROVIDER: S-EPMC4325097 | biostudies-literature | 2015 Mar

REPOSITORIES: biostudies-literature

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The flagellar set Fla2 in Rhodobacter sphaeroides is controlled by the CckA pathway and is repressed by organic acids and the expression of Fla1.

Vega-Baray Benjamín B Domenzain Clelia C Rivera Anet A Alfaro-López Rocío R Gómez-César Elidet E Poggio Sebastián S Dreyfus Georges G Camarena Laura L

Journal of bacteriology 20141215 5

Rhodobacter sphaeroides has two different sets of flagellar genes. Under the growth conditions commonly used in the laboratory, the expression of the fla1 set is constitutive, whereas the fla2 genes are not expressed. Phylogenetic analyses have previously shown that the fla1 genes were acquired by horizontal transfer from a gammaproteobacterium and that the fla2 genes are endogenous genes of this alphaproteobacterium. In this work, we characterized a set of mutants that were selected for swimmin ...[more]

PMID: 25512309

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Project description:UnlabelledRhodobacter sphaeroides is a free-living alphaproteobacterium that contains two clusters of functional flagellar genes in its genome: one acquired by horizontal gene transfer (fla1) and one that is endogenous (fla2). We have shown that the Fla2 system is normally quiescent and under certain conditions produces polar flagella, while the Fla1 system is always active and produces a single flagellum at a nonpolar position. In this work we purified and characterized the structure and analyzed the composition of the Fla2 flagellum. The number of polar filaments per cell is 4.6 on average. By comparison with the Fla1 flagellum, the prominent features of the ultra structure of the Fla2 HBB are the absence of an H ring, thick and long hooks, and a smoother zone at the hook-filament junction. The Fla2 helical filaments have a pitch of 2.64 μm and a diameter of 1.4 μm, which are smaller than those of the Fla1 filaments. Fla2 filaments undergo polymorphic transitions in vitro and showed two polymorphs: curly (right-handed) and coiled. However, in vivo in free-swimming cells, we observed only a bundle of filaments, which should probably be left-handed. Together, our results indicate that Fla2 cell produces multiple right-handed polar flagella, which are not conventional but exceptional.ImportanceR. sphaeroides possesses two functional sets of flagellar genes. The fla1 genes are normally expressed in the laboratory and were acquired by horizontal transfer. The fla2 genes are endogenous and are expressed in a Fla1(-) mutant grown phototrophically and in the absence of organic acids. The Fla1 system produces a single lateral or subpolar flagellum, and the Fla2 system produces multiple polar flagella. The two kinds of flagella are never expressed simultaneously, and both are used for swimming in liquid media. The two sets of genes are certainly ready for responding to specific environmental conditions. The characterization of the Fla2 system will help us to understand its role in the physiology of this microorganism.

Project description:The flagellar lipoprotein FlgP has been identified in several species of bacteria, and its absence provokes different phenotypes. In this study, we show that in the alphaproteobacterium Rhodobacter sphaeroides, a ΔflgP mutant is unable to assemble the hook and the filament. In contrast, the membrane/supramembrane (MS) ring and the flagellar rod appear to be assembled. In the absence of FlgP a severe defect in the transition from rod to hook polymerization occurs. In agreement with this idea, we noticed a reduction in the amount of intracellular flagellin and the chemotactic protein CheY4, both encoded by genes dependent on σ28 This suggests that in the absence of flgP the switch to export the anti-sigma factor, FlgM, does not occur. The presence of FlgP was detected by Western blot in samples of isolated wild-type filament basal bodies, indicating that FlgP is an integral part of the flagellar structure. In this regard, we show that FlgP interacts with FlgH and FlgT, indicating that FlgP should be localized closely to the L and H rings. We propose that FlgP could affect the architecture of the L ring, which has been recently identified to be responsible for the rod-hook transition.IMPORTANCE Flagellar based motility confers a selective advantage on bacteria by allowing migration to favorable environments or in pathogenic species to reach the optimal niche for colonization. The flagellar structure has been well established in Salmonella However, other accessory components have been identified in other species. Many of these have been implied in adapting the flagellar function to enable faster rotation, or higher torque. FlgP has been proposed to be the main component of the basal disk located underlying the outer membrane in Campylobacter jejuni and Vibrio fischeri Its role is still unclear, and its absence impacts motility differently in different species. The study of these new components will bring a better understanding of the evolution of this complex organelle.

Dataset Information

The flagellar set Fla2 in Rhodobacter sphaeroides is controlled by the CckA pathway and is repressed by organic acids and the expression of Fla1.

Publications

The flagellar set Fla2 in Rhodobacter sphaeroides is controlled by the CckA pathway and is repressed by organic acids and the expression of Fla1.

Similar Datasets

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