• Beta-lactam resistance response triggered by inactivation of a nonessential penicillin-binding protein.

      Moya, Bartolomé; Dötsch, Andreas; Juan, Carlos; Blázquez, Jesús; Zamorano, Laura; Haussler, Susanne; Oliver, Antonio; Servicio de Microbiología and Unidad de Investigación, Hospital Son Dureta, Instituto Universitario de Investigación en Ciencias de la Salud Palma de Mallorca, Spain. (2009-03)
      It has long been recognized that the modification of penicillin-binding proteins (PBPs) to reduce their affinity for beta-lactams is an important mechanism (target modification) by which Gram-positive cocci acquire antibiotic resistance. Among Gram-negative rods (GNR), however, this mechanism has been considered unusual, and restricted to clinically irrelevant laboratory mutants for most species. Using as a model Pseudomonas aeruginosa, high up on the list of pathogens causing life-threatening infections in hospitalized patients worldwide, we show that PBPs may also play a major role in beta-lactam resistance in GNR, but through a totally distinct mechanism. Through a detailed genetic investigation, including whole-genome analysis approaches, we demonstrate that high-level (clinical) beta-lactam resistance in vitro, in vivo, and in the clinical setting is driven by the inactivation of the dacB-encoded nonessential PBP4, which behaves as a trap target for beta-lactams. The inactivation of this PBP is shown to determine a highly efficient and complex beta-lactam resistance response, triggering overproduction of the chromosomal beta-lactamase AmpC and the specific activation of the CreBC (BlrAB) two-component regulator, which in turn plays a major role in resistance. These findings are a major step forward in our understanding of beta-lactam resistance biology, and, more importantly, they open up new perspectives on potential antibiotic targets for the treatment of infectious diseases.
    • Efficient production of soluble recombinant single chain Fv fragments by a Pseudomonas putida strain KT2440 cell factory.

      Dammeyer, Thorben; Steinwand, Miriam; Krüger, Sarah-C; Dübel, Stefan; Hust, Michael; Timmis, Kenneth N; Helmholtz Centre for infection research, Inhoffenstr. 7, D-38124 Braunschweig, Germany. (2011)
      Recombinant antibody fragments have a wide range of applications in research, diagnostics and therapy. For many of these, small fragments like single chain fragment variables (scFv) function well and can be produced inexpensively in bacterial expression systems. Although Escherichia coli K-12 production systems are convenient, yields of different fragments, even those produced from codon-optimized expression systems, vary significantly. Where yields are inadequate, alternative production systems are needed. Pseudomonas putida strain KT2440 is a versatile biosafety strain known for good expression of heterologous genes, so we have explored its utility as a cell factory for production of scFvs.
    • FKBPs in bacterial infections.

      Ünal, Can M; Steinert, Michael; Helmholtz Centre for infection research, Inhoffenstr. 7, D-38124 Braunschweig, Germany. (2015-10)
      FK506-binding proteins (FKBPs) contain a domain with peptidyl-prolyl-cis/trans-isomerase (PPIase) activity and bind the immunosuppressive drugs FK506 and rapamycin. FKBPs belong to the immunophilin family and are found in eukaryotes and bacteria.
    • The intriguing cyclophilin A-HIV-1 Vpr interaction: prolyl cis/trans isomerisation catalysis and specific binding.

      Solbak, Sara M; Reksten, Tove R; Wray, Victor; Bruns, Karsten; Horvli, Ole; Raae, Arnt J; Henklein, Petra; Henklein, Peter; Röder, Rene; Mitzner, David; et al. (2010)
      Cyclophilin A (CypA) represents a potential target for antiretroviral therapy since inhibition of CypA suppresses human immunodeficiency virus type 1 (HIV-1) replication, although the mechanism through which CypA modulates HIV-1 infectivity still remains unclear. The interaction of HIV-1 viral protein R (Vpr) with the human peptidyl prolyl isomerase CypA is known to occur in vitro and in vivo. However, the nature of the interaction of CypA with Pro-35 of N-terminal Vpr has remained undefined.
    • Pseudomonas aeruginosa cupA-encoded fimbriae expression is regulated by a GGDEF and EAL domain-dependent modulation of the intracellular level of cyclic diguanylate.

      Meissner, Andree; Wild, Verena; Simm, Roger; Rohde, Manfred; Erck, Christian; Bredenbruch, Florian; Morr, Michael; Römling, Ute; Häussler, Susanne; Division of Cell Biology and Immunology, Helmholtz Centre for Infection Research, Inhoffenstrasse 7, 38124 Braunschweig, Germany. (2007-10)
      Cyclic-diguanylate (c-di-GMP) is a widespread bacterial signal molecule that plays a major role in the modulation of cellular surface components, such as exopolysaccharides and fimbriae, and in the establishment of a sessile life style. Here, we report that intracellular c-di-GMP levels influence cupA-encoded fimbriae expression in Pseudomonas aeruginosa. In an autoaggregative P. aeruginosa small colony variant (SCV) CupA fimbriae and the intracellular c-di-GMP concentration were found to be enhanced as compared with the clonal wild-type. The SCV morphology and the expression of CupA fimbriae were dependent on a functional PA1120 and morA gene both encoding a GGDEF domain. Overexpression of the GGDEF domain protein PA1120 complemented the PA1120 and the morA mutant with respect to CupA fimbriae expression. In agreement with these findings, overexpression of the EAL domain containing phenotypic variance regulator (PvrR) in the SCV resulted in a decreased intracellular level of c-di-GMP, a reduced cupA fimbriae expression and a switch to wild-type colony morphology.