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Bacteria as single living organisms are exposed to rapidly changing external conditions. Given strong selection pressure, it is not surprising that bacteria have evolved sophisticated signaling systems to constantly monitor changes in external parameters such as acidity, nutrients, eukaryotic signals and to adapt their structure, physiology, and behavior accordingly.

Research in Kirsten Jung's lab focuses on elucidating the molecular mechanisms of stimulus perception by histidine/kinase response regulator systems involved in metabolic (pyruvate) and ionic (K+) homeostasis in Escherichia, Salmonella and Vibrio (Area 1). We investigate the spatio-temporal dynamics of membrane-integrated and soluble receptors in response to acid stress in Escherichia and Vibrio species and are interested in the stress-response behavior of individual cells (Area 2). We study translation elongation factor P (EF-P), a protein that alleviates ribosome stalling at polyproline stretches, and its post-translational modification systems (Area 3). Finally, we are working on identifying new intracellular targets of natural compounds (Area 4).


Research Area 1: Molecular mechanisms of stimulus perception by histidine kinase/response regulator systems

Bacteria sense and respond to various stress conditions by employing so called two-component systems. These systems consist of a histidine kinase and a response regulator, which sense environmental stimuli, transduce information via phosphorylation and induce a cellular response. Escherichia coli, for example, contains 32 of these systems.
We are studying how sensing and uptake of the primary metabolite pyruvate is coordinated by the BtsS/BtsR and YpdA/YpdB histidine kinase systems in Escherichia, Vibrio and Salmonella species. The studies focus on the investigation of the unusual phosphorylation-independent signal transduction within the pyruvate-sensing histidine kinase/response regulator systems and their structural analysis.

Model of the nutrient sensing

Figure 1: Model of the nutrient sensing BtsS/BtsR-YpdA/YpdB network in E. coli.

Selected Publications:

  • Steiner, B.D., Eberly, A.R., Hurst, M.N., Zhang, E., Behr, S., Jung, K., Hadjifrangiskou, M. (2018) Evidence of cross-regulation in two closely-related pyruvate-sensing systems in uropathogenic Escherichia coli, J. Membr. Biol., 251(1):65-74.
  • Vilhena,C., Kaganovitch, E., Shin, J.Y., Grünberger, A., Behr, S., Kristoficova, I., Brameyer, S., Kohlheyer, D., Jung, K. (2018) A single cell view of the BtsSR/YpdAB pyruvate sensing network in Escherichia coli and its biological relevance, J. Bacteriol., 200: e00536-17.
  • Behr, S., Kristoficova, I., Wittig, M., Breland, E.J., Eberly, A.R., Sachs, C., Schmitt-Kopplin, P., Hadjifrangiskou, M., Jung, K. (2017) Identification of a high-affinity pyruvate receptor in Escherichia coli, Sci. Rep., 7: 1388.
  • Fried, L., Behr, S., Jung, K. (2013) Identification of a target gene and activating stimulus for the YpdA/YpdB histidine kinase/response regulator system in Escherichia coli, J. Bacteriol. 195, 807-815.
  • Kraxenberger, T., Fried, L., Behr, S., Jung, K. (2012) First insights into the unexplored two-component system YehU/YehT in Escherichia coli, J. Bacteriol. 194, 4272-4284.

We are also studying structure and dynamics of KdpD of E. coli, a dual-sensing receptor for K+ and a representative of the sensor histidine kinase family. Under fluctuating conditions, the dual sensing KdpD ensures together with KdpE robust K+ homeostasis in E. coli.

KdpD 3 is a bifunctional receptor

Figure 2: KdpD is a bifunctional receptor that regulates its kinase and phosphatase activities by sensing extra- and intracellular K+.

Selected Publications:

  • Schramke, H., Tostevin, F., Heermann, R., Gerland, U., Jung, K. (2016) A dual-sensing receptor confers robust cellular homeostasis, Cell Rep. 16, 213–221.
  • Moscoso, J.A., Schramke, H., Zhang, Y., Tosi, T., Dehbi, A., Jung, K., Gründling, A. (2015) Binding of c-di-AMP to the Staphylococcus aureus sensor kinase KdpD occurs via the USP domain and down-regulates the expression of the Kdp potassium transporter, J. Bacteriol., 198 (1), 98-110.
  • Heermann, R., Zigann, K., Gayer, S., Rodriguez-Fernandez, M., Banga, J.R., Kremling, A., Jung, K. (2014) Dynamics of an interactive network composed of a bacterial two-component system, a transporter and K+ as mediator, PLoS One, 9(2). e89671.
  • Schramke, H., Wang, Y., Heermann, R., Jung, K. (2015) Stimulus perception by histidine kinases. In de Bruijn, F.J. (Editor) Stress and environmental control of gene expression in bacteria, Wiley-Blackwell Publishers.top

Research Area 2: Spatio-temporal dynamics of low-copy number receptors involved in acid stress resistance

Acid resistance is an important property of bacteria, such as Escherichia coli, to survive acidic environments like the human gastrointestinal tract. E. coli possess both passive and inducible acid resistance systems to counteract acidic environments. Thus, E. coli evolved sophisticated signaling systems to sense and appropriately respond to environmental acidic stress by regulating the activity of its three inducible acid resistance systems. One of these systems is the Cad system that is only induced under moderate acidic stress in a lysine-rich environment by the pH-responsive transcriptional regulator CadC. We study the localization and spatiotemporal dynamics of CadC and other membrane-integrated and intracellular receptors involved in acid stress response in Escherichia and Vibrio species with a specific focus on their DNA surface exploration during target search.  the localization of the one-component receptor

Figure 3: The localization of the one-component receptor CadC, an acid stress sensor, is directed by binding to DNA within Escherichia coli cells.


It is our aim to elucidate general molecular design principles of the Cad systems in different Proteobacteria and their target gene expression noise at single cell level during acid stress conditions.

                                The molecular design of the Cad-system

Figure 4: The molecular design of the Cad-system influences the degree of noise in CadB-eGFP abundance under acid stress.

Selected Publications:

  • Brameyer, S., Hoyer, E., Bibinger, S., Burdack, K., Lassak, J., Jung, K. (2020) Molecular design of a signaling system influences noise in protein abundance under acid stress in different gamma-proteobacteria. J Bacteriol, e00121-20.
  • Brameyer, S., Rösch, T.C., Andarib, J.A., Hoyer, E., Schwarz, J., Graumann, P.L., Jung, K. (2019) DNA-binding directs the localization of a membrane-integrated receptor of the ToxR family. Commun. Biol., 2:4.
  • Buchner, S., Schlundt, A., Lassak, J., Sattler, J., Jung, K. (2015) The role of a disordered linker in the pH-sensor CadC of Escherichia coli, J. Mol. Biol., 427(15): 2548-2561.
  • Lorenz, N., Shin, J.Y., Jung, K. (2017) Activity, abundance and localization of quorum sensing receptors in Vibrio harveyi, Front. Microbiol., 8, 634.
  • Fritz, G., Koller, C., Tetsch, L., Haneburger, I., Burdack, K., Jung, K., Gerland, U. (2009) Induction kinetics and feedback inhibition of a conditional stress response system in Escherichia coli, J. Mol. Biol. 393, 272–286.

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Research Area 3: Post-translational modifications of elongation factor P (EF-P) and the role of poly-proline motifs

The fundamental process of protein synthesis is catalyzed on ribosomes. We have recently demonstrated that bacterial ribosomes become arrested when translating proteins contain consecutive polyproline stretches, and that this arrest is alleviated by the translation elongation factor EF-P. Furthermore, we could show that the post-translational β-lysinylation of lysine34 of Escherichia coli EF-P by the enzymes EpmA and EpmB and the rhamnosylation of arginine32 of Shewanella EF-P by EarP, respectively, are critical for the rescue activity of EF-P. EF-P is aminopentanoylated in Bacillus and other members of the Firmicutes. In contrast, the EF-Ps of Actinobacteria – specifically, Clostridium glutamicum, Streptomyces coelicolor and Mycobacterium tuberculosis – alleviate ribosome stalling at polyproline motifs without the need for any activating post-translational modification.

                                                Ef-P prevents ribosome stalling

                                                

Figure 5: EF-P prevents ribosome stalling at polyproline stretches.

Many virulence factors contain polyproline stretches, which explains why modified EF-P is critical for bacterial pathogenicity. Polyproline motifs are required for the regulation of copy number or dimerization or catalytic activity of certain proteins. The project focuses on the elucidation and characterization of synthetic and novel post-translational modification pathways of EF-P.

Selected Publications:

  • Pinheiro, B., Scheidler, C.M., Kielkowski, P., Schmid, M., Forné, I., Ye, S., Reiling, N., Takano, E., Imhof, A., Sieber, S. A., Schneider, S., Jung, K. (2020) Structure and function of a novel elongation factor P subfamily in Actinobacteria. Cell Rep., 30, 4332-4342.e5.
  • Pfab, M., Kielkowski, P., Krafczyk, R., Volkwein, W., Sieber, S.A., Lassak, J., Jung, K. (2020) Synthetic post-translational modifications of elongation factor P using the ligase EpmA. FEBS J., doi: 10.1111/febs.15346.
  • Motz, L., Jung, K. (2018) The role of polyproline motifs in the histidine kinase EnvZ, PLoS One, 13(6): e0199782.
  • Qi, F., Motz, M., Jung, K., Lassak, J. and Frishman, D. (2018) Evolutionary analysis of polyproline motifs in Escherichia coli reveals their regulatory role in translation, PLoS Comp. Biol. 14(2):e1005987.
  • Starosta, A.L., Lassak, J., Atkinson, G.C., Peil, L., Woolstenhulme, C.J., Virumäe, K., Buskirk, A., Tenson, T., Remme, J., Jung, K., Wilson, D.N. (2014) A conserved proline triplet in Val-tRNA synthetase and the origin of elongation factor P, Cell Rep., 9, 476-483.
  • Lassak, J., Keilhauer, E., Fürst, M., Wuichet, K., Gödeke, J., Starosta, A.L., Chen, J., Søgaard-Andersen, L., Rohr, J., Wilson, D.N., Häussler, S., Mann, M., Jung, K. (2015) Arginine-rhamnosylation as new strategy for post-translational modification of translation elongation factor P, Nat. Chem. Biol., 11, 266-70.
  • Ude, S., Lassak, J., Starosta, A. L., Kraxenberger, T., Wilson, D.N., Jung, K. (2013) Translation elongation factor EF-P alleviates ribosome stalling at polyproline stretches. Science 339, 82-85.

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Research Area 4: Chemical Biology and the identification of protein targets of natural compounds

There are about 500,000 molecules for the communication between pro- and eukaryotes. We use bacterial model organisms to study the effect of natural compounds such as fimbrolides, quorum quenchers or eukaryotic hormones on the phenotypic behavior of bacteria, such as quorum sensing and chemotaxis. The project also focuses on the identification of the cellular targets of these compounds.

Chemical communication 

Figure 6: Chemical communication between pro- and eukaryotes.

Selected Publications:

  • Zhao, W., Lorenz, N., Jung, K., Sieber, S.A. (2016) Mechanistic analysis of aliphatic β-lactones in Vibrio harveyi reveals a quorum sensing independent mode of action. Chem. Commun., 52, 11971-11974.
  • Zhao, W., Lorenz, N., Jung, K., Sieber, S.A. (2016) Fimbrolide natural products disrupt bioluminescence of Vibrio harveyi by targeting autoinducer biosynthesis and luciferase activity, Angew. Chem. Int. Ed. Engl. 55 (3):1187-91.
  • Rossmann, F.S., Wobser, D., Racek, T., Puchalka, J., Rabener, E.M., Reiger, M., Hendrickx, A.P.A., Diederich, A., Jung, K., Klein, C., Huebner, J. (2015) Phage-mediated dispersal of biofilm and distribution of bacterial virulence genes is induced by Quorum Sensing. PLoS Pathog. 11(2): e1004653.
  • Chu, Y., Nega, M., Wölfle, M., Plener, L., Grond, S., Jung, K., Götz, F. (2013) A new class of quorum quenching molecules from Staphylococcus species affects communication of Gram-negative bacteria, PLoS Pathog. 9(9): e1003654.

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