• Cross talk between the response regulators PhoB and TctD allows for the integration of diverse environmental signals in Pseudomonas aeruginosa.

      Bielecki, Piotr; Jensen, Vanessa; Schulze, Wiebke; Gödeke, Julia; Strehmel, Janine; Eckweiler, Denitsa; Nicolai, Tanja; Bielecka, Agata; Wille, Thorsten; Gerlach, Roman G; et al. (2015-07-27)
      Two-component systems (TCS) serve as stimulus-response coupling mechanisms to allow organisms to adapt to a variety of environmental conditions. The opportunistic pathogen Pseudomonas aeruginosa encodes for more than 100 TCS components. To avoid unwanted cross-talk, signaling cascades are very specific, with one sensor talking to its cognate response regulator (RR). However, cross-regulation may provide means to integrate different environmental stimuli into a harmonized output response. By applying a split luciferase complementation assay, we identified a functional interaction of two RRs of the OmpR/PhoB subfamily, namely PhoB and TctD in P. aeruginosa. Transcriptional profiling, ChIP-seq analysis and a global motif scan uncovered the regulons of the two RRs as well as a quadripartite binding motif in six promoter regions. Phosphate limitation resulted in PhoB-dependent expression of the downstream genes, whereas the presence of TctD counteracted this activation. Thus, the integration of two important environmental signals e.g. phosphate availability and the carbon source are achieved by a titration of the relative amounts of two phosphorylated RRs that inversely regulate a common subset of genes. In conclusion, our results on the PhoB and TctD mediated two-component signal transduction pathways exemplify how P. aeruginosa may exploit cross-regulation to adapt bacterial behavior to complex environments.
    • Deep transcriptome profiling of clinical Klebsiella pneumoniae isolates reveals strain and sequence type-specific adaptation.

      Bruchmann, Sebastian; Muthukumarasamy, Uthayakumar; Pohl, Sarah; Preusse, Matthias; Bielecka, Agata; Nicolai, Tanja; Hamann, Isabell; Hillert, Roger; Kola, Axel; Gastmeier, Petra; et al. (2015-11)
      Health-care-associated infections by multi-drug-resistant bacteria constitute one of the greatest challenges to modern medicine. Bacterial pathogens devise various mechanisms to withstand the activity of a wide range of antimicrobial compounds, among which the acquisition of carbapenemases is one of the most concerning. In Klebsiella pneumoniae, the dissemination of the K. pneumoniae carbapenemase is tightly connected to the global spread of certain clonal lineages. Although antibiotic resistance is a key driver for the global distribution of epidemic high-risk clones, there seem to be other adaptive traits that may explain their success. Here, we exploited the power of deep transcriptome profiling (RNA-seq) to shed light on the transcriptomic landscape of 37 clinical K. pneumoniae isolates of diverse phylogenetic origins. We identified a large set of 3346 genes which was expressed in all isolates. While the core-transcriptome profiles varied substantially between groups of different sequence types, they were more homogenous among isolates of the same sequence type. We furthermore linked the detailed information on differentially expressed genes with the clinically relevant phenotypes of biofilm formation and bacterial virulence. This allowed for the identification of a diminished expression of biofilm-specific genes within the low biofilm producing ST258 isolates as a sequence type-specific trait.
    • Genome-wide localization and expression profiling establish Sp2 as a sequence-specific transcription factor regulating vitally important genes.

      Terrados, Gloria; Finkernagel, Florian; Stielow, Bastian; Sadic, Dennis; Neubert, Juliane; Herdt, Olga; Krause, Michael; Scharfe, Maren; Jarek, Michael; Suske, Guntram; et al. (2012-09)
      The transcription factor Sp2 is essential for early mouse development and for proliferation of mouse embryonic fibroblasts in culture. Yet its mechanisms of action and its target genes are largely unknown. In this study, we have combined RNA interference, in vitro DNA binding, chromatin immunoprecipitation sequencing and global gene-expression profiling to investigate the role of Sp2 for cellular functions, to define target sites and to identify genes regulated by Sp2. We show that Sp2 is important for cellular proliferation that it binds to GC-boxes and occupies proximal promoters of genes essential for vital cellular processes including gene expression, replication, metabolism and signalling. Moreover, we identified important key target genes and cellular pathways that are directly regulated by Sp2. Most significantly, Sp2 binds and activates numerous sequence-specific transcription factor and co-activator genes, and represses the whole battery of cholesterol synthesis genes. Our results establish Sp2 as a sequence-specific regulator of vitally important genes.
    • A human-horse comparative map based on equine BAC end sequences.

      Leeb, Tosso; Vogl, Claus; Zhu, Baoli; de Jong, Pieter J; Binns, Matthew M; Chowdhary, Bhanu P; Scharfe, Maren; Jarek, Michael; Nordsiek, Gabriele; Schrader, Frank; et al. (2006-06)
      In an effort to increase the density of sequence-based markers for the horse genome we generated 9473 BAC end sequences (BESs) from the CHORI-241 BAC library with an average read length of 677 bp. BLASTN searches with the BESs revealed 4036 meaningful hits (E
    • Tumor invasion of Salmonella enterica serovar Typhimurium is accompanied by strong hemorrhage promoted by TNF-alpha.

      Leschner, Sara; Westphal, Kathrin; Dietrich, Nicole; Viegas, Nuno; Jablonska, Jadwiga; Lyszkiewicz, Marcin; Lienenklaus, Stefan; Falk, Werner; Gekara, Nelson; Loessner, Holger; et al. (2009)
      Several facultative anaerobic bacteria with potential therapeutic abilities are known to preferentially colonize solid tumors after systemic administration. How they efficiently find and invade the tumors is still unclear. However, this is an important issue to be clarified when bacteria should be tailored for application in cancer therapy.