The Escherichia coli BarA-UvrY two-component system is a virulence determinant in the urinary tract

BACKGROUND: The Salmonella enterica BarA-SirA, the Erwinia carotovora ExpS-ExpA, the Vibrio cholerae BarA-VarA and the Pseudomonas spp GacS-GacA all belong to the same orthologous family of two-component systems as the Escherichia coli BarA-UvrY. In the first four species it has been demonstrated that disruption of this two-component system leads to a clear reduction in virulence of the bacteria. Our aim was to determine if the Escherichia coli BarA-UvrY two-component system is connected with virulence using a monkey cystitis model. RESULTS: Cystitis was generated in Macaque fascularis monkeys by infecting the bladder with a 1:1 mixture of the uropathogenic Escherichia coli isolate DS17 and a derivative where the uvrY gene had been disrupted with a kanamycin resistance gene. Urine was collected through bladder punctuation at subsequent time intervals and the relative amount of uvrY mutant was determined. This showed that inactivation of the UvrY response regulator leads to a reduced fitness. In similar competitions in culture flasks with Luria Broth (LB) the uvrY mutant rather had a higher fitness than the wild type. When the competitions were done in flasks with human urine the uvrY mutant initially had a lower fitness. This was followed by a fluctuation in the level of mutant in the long-term culture, with a pattern that was specific for the individual urines that were tested. Addition of LB to the different urine competition cultures however clearly led to a consistently higher fitness of the uvrY mutant. CONCLUSION: This paper demonstrates that the BarA-UvrY two-component system is a determinant for virulence in a monkey cystitis model. The observed competition profiles strengthen our previous hypothesis that disruption of the BarA-UvrY two-component system impairs the ability of the bacteria to switch between different carbon sources. The urine in the bladder contains several different carbon sources and its composition changes over time. Inability to efficiently switch between the carbon sources may thus provide an explanation to the reduced fitness of the uvrY mutant in the cystitis model

The ArcB Leucine Zipper Domain Is Required for Proper ArcB Signaling

The Arc two-component system modulates the expression of numerous genes in response to respiratory growth conditions. This system comprises ArcA as the response regulator and ArcB as the sensor kinase. ArcB is a tripartite histidine kinase whose activity is regulated by the oxidation of two cytosol-located redox-active cysteine residues that participate in intermolecular disulfide bond formation. Here, we report that the ArcB protein segment covering residues 70–121, fulfills the molecular characteristics of a leucine zipper containing coiled coil structure. Also, mutational analyses of this segment reveal three different phenotypical effects to be distributed along the coiled coil structure of ArcB, demonstrating that this motif is essential for proper ArcB signaling

Effect of d-Lactate on the Physiological Activity of the ArcB Sensor Kinase in Escherichia coli

The Arc two-component system, comprising the ArcB sensor kinase and the ArcA response regulator, modulates the expression of numerous genes in response to the respiratory growth conditions. Under anoxic growth conditions ArcB autophosphorylates and transphosphorylates ArcA, which in turn represses or activates its target operons. The anaerobic metabolite d-lactate has been shown to stimulate the in vitro autophosphorylating activity of ArcB. In this study, the in vivo effect of d-lactate on the kinase activity of ArcB was assessed. The results demonstrate that d-lactate does not act as a direct signal for activation of ArcB, as previously proposed, but acts as a physiologically significant effector that amplifies ArcB kinase activity

The ArcB Sensor Kinase of Escherichia coli Autophosphorylates by an Intramolecular Reaction▿

The Arc two-component system, comprising the ArcB sensor kinase and the ArcA response regulator, modulates the expression of numerous genes in response to the respiratory conditions of growth. ArcB is a tripartite histidine kinase whose activity is regulated by the oxidation of two cytosol-located redox-active cysteine residues that participate in intermolecular disulfide bond formation. Here we show that ArcB autophosphorylates through an intramolecular reaction which diverges from the usually envisaged intermolecular autophosphorylation of homodimeric histidine kinases

El circuito regulatorio BarA/UvrY-CsrA en Escherichia coli y sus homólogos en las γ-proteobacterias

The BarA/UvrY two-component system of Escherichia coli directly activates the expression of the small non-coding RNAs CsrB and CsrC. These small RNAs function as antagonist of the CsrA activity, which regulates the translation of numerous target mRNAs. The BarA/UvrY-CsrA circuitry is conserved in the γ-proteobacteria and although the mechanism of action is preserved, there are important functional differences that represent the particular requirements of each bacterial species. In this review we compare the strategies that different bacterial species employ in order to carry out the regulation of the above circuitry in function of their life style.El sistema de dos-componentes BarA/UvrY de Escherichia coli activa directamente la expresión de los RNAs pequeños no-codificantes CsrB y CsrC. Estos RNAs pequeños funcionan como antagonistas de la actividad de la proteína CsrA, la cual regula positiva y negativamente la traducción de múltiples mensajeros blanco. El circuito BarA/UvrY-CsrA está conservado en las γ-proteobacterias y aunque el mecanismo de acción se mantiene, existen importantes diferencias funcionales que representan los requerimientos especiales de cada especie bacteriana.  En esta revisión compararemos las estrategias que diferentes bacterias emplean para llevar a cabo la regulación del mencionado circuito en función a su estilo de vida

Requirement of the Receiver and Phosphotransfer Domains of ArcB for Efficient Dephosphorylation of Phosphorylated ArcA In Vivo

The Arc two-component system, comprising the ArcB sensor kinase and the ArcA response regulator, modulates the expression of numerous genes in response to the respiratory conditions of growth. Under anoxic growth conditions, ArcB autophosphorylates and transphosphorylates ArcA, which in turn represses or activates its target operons. Under aerobic growth conditions, phosphorylated ArcA (ArcA-P) dephosphorylates and its transcriptional regulation is released. The dephosphorylation of ArcA-P has been shown to occur, at least in vitro, via an ArcA(Asp54)-P → ArcB(His717)-P → ArcB(Asp576)-P → P(i) reverse phosphorelay. In this study, the physiological significance of this pathway was assessed. The results demonstrate that the receiver and phosphotransfer domains of the tripartite sensor kinase ArcB are necessary and sufficient for efficient ArcA-P dephosphorylation in vivo

El circuito regulatorio BarA/UvrY-CsrA en Escherichia coli y sus homólogos en las γ-proteobacterias

El sistema de dos-componentes BarA/UvrY de Escherichia coli activa directamente la expresión de los RNAs pequeños no-codificantes CsrB y CsrC. Estos RNAs pequeños funcionan como antagonistas de la actividad de la proteína CsrA, la cual regula positiva y negativamente la traducción de múltiples mensajeros blanco. El circuito BarA/UvrY-CsrA está conservado en las γ-proteobacterias y aunque el mecanismo de acción se mantiene, existen importantes diferencias funcionales que representan los requerimientos especiales de cada especie bacteriana. En esta revisión compararemos las estrategias que diferentes bacterias emplean para llevar a cabo la regulación del mencionado circuito en función a su estilo de vida

The Neurospora crassa DCC-1 Protein, a Putative Histidine Kinase, Is Required for Normal Sexual and Asexual Development and Carotenogenesis▿

Two-component signaling pathways based on phosphoryl group transfer between histidine kinase and response regulator proteins regulate environmental responses in bacteria, archaea, plants, slime molds, and fungi. Here we characterize a mutant form of DCC-1, a putative histidine kinase encoded by the NCU00939 gene of the filamentous fungus Neurospora crassa. We show that this protein participates in the regulation of processes such as conidiation, perithecial development, and, to a certain degree, carotenogenesis. Furthermore, DCC-1 is suggested to exert its effect by promoting cyclic AMP production, thereby placing this protein within the context of a signaling pathway