title: In vivo study of the two-component signaling network in Escherichia coli
creator: Sommer, Erik
subject: ddc-570
subject: 570 Life sciences
description: Microorganisms commonly use ‘two-component’ signaling systems for sensing environmental conditions, with members being present in nearly all bacterial and archaeal genomes in different numbers. Prototypical two-component systems are comprised of a sensory histidine kinase and a response regulator protein that is phosphorylated by the kinase. The regulator typically acts as a transcription factor regulating gene expression. Due to their prevalence in microorganisms, a basic understanding of the principles of two-component systems provides insights into mechanisms of prokaryotic signaling circuits. Apart from a few studies performed in vitro, the signaling properties of a whole bacterial two-component network in vivo remains largely unclear. Using a system level approach, we characterized the localization of signaling proteins and the interactions between pathways on different levels in the model bacterium Escherichia coli. We constructed a comprehensive library of fluorescent protein fusions to kinases and regulators from two-component systems, and applied fluorescence microscopy to analyze their spatial organization within the cell. We found that most of the sensors exhibit a intrinsic tendency for cluster formation, which might provide a scaffold for information processing and insulation against detrimental noise from other sources. We used in vivo FRET microscopy tools to study protein interactions in a systematic way. For kinases, we could confirm the formation of sensor dimers or higher order oligomers in vivo in most of the cases. For the sensor BaeS, we characterized the change of sensor confirmation upon stimulation. Additionally, we identified a few pathways exhibiting interconnections on the sensor level and between sensors and non-cognate regulators, providing an additional layer of information processing. We could confirm the physiological relevance of some of these pathway interconnections on the gene expression level, using flow cytometry measurements of a fluorescent promotor library. Moreover, using this library we found most of the reported stimuli not affecting two-component gene expression. Taken together, our data provide a deeper understanding of cellular organization within and interconnections between different two-component systems in E. coli. The results of this study can broaden the understanding of cell signaling principles in bacteria.
date: 2012
type: Dissertation
type: info:eu-repo/semantics/doctoralThesis
type: NonPeerReviewed
format: application/pdf
identifier: https://archiv.ub.uni-heidelberg.de/volltextserverhttps://archiv.ub.uni-heidelberg.de/volltextserver/13155/1/Diss_Erik_Sommer.pdf
identifier: DOI:10.11588/heidok.00013155
identifier: urn:nbn:de:bsz:16-opus-131552
identifier:   Sommer, Erik  (2012) In vivo study of the two-component signaling network in Escherichia coli.  [Dissertation]     
relation: https://archiv.ub.uni-heidelberg.de/volltextserver/13155/
rights: info:eu-repo/semantics/openAccess
rights: http://archiv.ub.uni-heidelberg.de/volltextserver/help/license_urhg.html
language: eng