Dataset Information

Mechanism of Signalling and Adaptation through the Rhodobacter sphaeroides Cytoplasmic Chemoreceptor Cluster.

ABSTRACT: Rhodobacter sphaeroides has two chemotaxis clusters, an Escherichia coli-like cluster with membrane-spanning chemoreceptors and a less-understood cytoplasmic cluster. The cytoplasmic CheA is split into CheA₄, a kinase, and CheA₃, a His-domain phosphorylated by CheA₄ and a phosphatase domain, which together phosphorylate and dephosphorylate motor-stopping CheY₆. In bacterial two-hybrid analysis, one major cytoplasmic chemoreceptor, TlpT, interacted with CheA₄, while the other, TlpC, interacted with CheA₃. Both clusters have associated adaptation proteins. Deleting their methyltransferases and methylesterases singly and together removed chemotaxis, but with opposite effects. The cytoplasmic cluster signal overrode the membrane cluster signal. Methylation and demethylation of specific chemoreceptor glutamates controls adaptation. Tandem mass spectroscopy and bioinformatics identified four putative sites on TlpT, three glutamates and a glutamine. Mutating each glutamate to alanine resulted in smooth swimming and loss of chemotaxis, unlike similar mutations in E. coli chemoreceptors. Cells with two mutated glutamates were more stoppy than wild-type and responded and adapted to attractant addition, not removal. Mutating all four sites amplified the effect. Cells were non-motile, began smooth swimming on attractant addition, and rapidly adapted back to non-motile before attractant removal. We propose that TlpT responds and adapts to the cell's metabolic state, generating the steady-state concentration of motor-stopping CheY₆~P. Membrane-cluster signalling produces a pulse of CheY₃/CheY₄~P that displaces CheY₆~P and allows flagellar rotation and smooth swimming before both clusters adapt.

SUBMITTER: Beyer JA

PROVIDER: S-EPMC6829392 | biostudies-literature | 2019 Oct

REPOSITORIES: biostudies-literature

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Mechanism of Signalling and Adaptation through the Rhodobacter sphaeroides Cytoplasmic Chemoreceptor Cluster.

Beyer Jennifer A de JA Szöllössi Andrea A Byles Elaine E Fischer Roman R Armitage Judith P JP

International journal of molecular sciences 20191014 20

Rhodobacter sphaeroides has two chemotaxis clusters, an Escherichia coli-like cluster with membrane-spanning chemoreceptors and a less-understood cytoplasmic cluster. The cytoplasmic CheA is split into CheA4, a kinase, and CheA3, a His-domain phosphorylated by CheA4 and a phosphatase domain, which together phosphorylate and dephosphorylate motor-stopping CheY6. In bacterial two-hybrid analysis, one major cytoplasmic chemoreceptor, ...[more]

PMID: 31615130

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Project description:Activation of the two-component system formed by CckA, ChpT, and CtrA (kinase, phosphotransferase, and response regulator, respectively) in Rhodobacter sphaeroides does not occur under the growth conditions commonly used in the laboratory. However, it is possible to isolate a gain-of-function mutant in CckA that turns the system on. Using massive parallel transcriptome sequencing (RNA-seq), we identified 321 genes that are differentially regulated by CtrA. From these genes, 239 were positively controlled and 82 were negatively regulated. Genes encoding the Fla2 polar flagella and gas vesicle proteins are strongly activated by CtrA. Genes involved in stress responses as well as several transcriptional factors are also positively controlled, whereas the photosynthetic and CO2 fixation genes are repressed. Potential CtrA-binding sites were bioinformatically identified, leading to the proposal that at least 81 genes comprise the direct regulon. Based on our results, we ponder that the transcriptional response orchestrated by CtrA enables a lifestyle in which R. sphaeroides will effectively populate the surface layer of a water body enabled by gas vesicles and will remain responsive to chemotactic stimuli using the chemosensoring system that controls the Fla2 flagellum. Simultaneously, fine-tuning of photosynthesis and stress responses will reduce the damage caused by heat and high light intensity in this water stratum. In summary, in this bacterium CtrA has evolved to control physiological responses that allow its adaptation to a particular lifestyle instead of controlling the cell cycle as occurs in other species.IMPORTANCE Cell motility in Alphaproteobacteria is frequently controlled by the CckA, ChpT, and CtrA two-component system. Under the growth conditions commonly used in the laboratory, ctrA is transcriptionally inactive in Rhodobacter sphaeroides, and motility depends on the Fla1 flagellar system that was acquired by a horizontal transfer event. Likely, the incorporation of this flagellar system released CtrA from the strong selective pressure of being the main motility regulator, allowing this two-component system to specialize and respond to some specific conditions. Identifying the genes that are directly regulated by CtrA could help us understand the conditions in which the products of this regulon are required. Massive parallel transcriptome sequencing (RNA-seq) revealed that CtrA orchestrates an adaptive response that contributes to the colonization of a particular environmental niche.

Dataset Information

Mechanism of Signalling and Adaptation through the Rhodobacter sphaeroides Cytoplasmic Chemoreceptor Cluster.

Publications

Mechanism of Signalling and Adaptation through the <i>Rhodobacter sphaeroides</i> Cytoplasmic Chemoreceptor Cluster.

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