Bohme K.,TU Braunschweig
PLoS pathogens | Year: 2012
Expression of all Yersinia pathogenicity factors encoded on the virulence plasmid, including the yop effector and the ysc type III secretion genes, is controlled by the transcriptional activator LcrF in response to temperature. Here, we show that a protein- and RNA-dependent hierarchy of thermosensors induce LcrF synthesis at body temperature. Thermally regulated transcription of lcrF is modest and mediated by the thermo-sensitive modulator YmoA, which represses transcription from a single promoter located far upstream of the yscW-lcrF operon at moderate temperatures. The transcriptional response is complemented by a second layer of temperature-control induced by a unique cis-acting RNA element located within the intergenic region of the yscW-lcrF transcript. Structure probing demonstrated that this region forms a secondary structure composed of two stemloops at 25°C. The second hairpin sequesters the lcrF ribosomal binding site by a stretch of four uracils. Opening of this structure was favored at 37°C and permitted ribosome binding at host body temperature. Our study further provides experimental evidence for the biological relevance of an RNA thermometer in an animal model. Following oral infections in mice, we found that two different Y. pseudotuberculosis patient isolates expressing a stabilized thermometer variant were strongly reduced in their ability to disseminate into the Peyer's patches, liver and spleen and have fully lost their lethality. Intriguingly, Yersinia strains with a destabilized version of the thermosensor were attenuated or exhibited a similar, but not a higher mortality. This illustrates that the RNA thermometer is the decisive control element providing just the appropriate amounts of LcrF protein for optimal infection efficiency.
Bunjes H.,TU Braunschweig
Current Opinion in Colloid and Interface Science | Year: 2011
For about 20. years nanoparticles based on solid lipids have been under investigation as drug carrier systems. They can be prepared from a broad variety of lipid matrix materials including glycerides, fatty acids and waxes and are stabilized by physiologically compatible surfactants. Although the matrix lipids principally retain their material properties when dispersed into the colloidal state there are various peculiarities that have to be observed when dealing with such systems. In particular, the crystallization behavior and the polymorphic transitions are altered in the nanoparticulate systems. These properties as well as the particle shape and structure may be affected by the type of surfactants used for stabilization. Also incorporated drugs can modify the structural characteristics of the nanoparticles. Interactions between the individual particles may lead to alterations of the macroscopic behavior of the dispersions, especially of their rheological properties. Such structural parameters can influence the drug carrier properties of the dispersions. © 2011 Elsevier Ltd.
Dickschat J.S.,TU Braunschweig
Natural Product Reports | Year: 2014
Covering: up to 2013 This review gives a modern methodic overview of how volatile natural products from various sources such as plants, animals, bacteria and fungi can be trapped and how compound identification can be performed even in cases of very low yields or within highly complex compound mixtures. A detailed discussion is presented on how a structural proposal for an unknown analyte can be derived from GC-MS data. Furthermore, the application of trace analytical techniques in biosynthetic studies with isotopically labelled compounds is presented, including a discussion of the pros and cons of different kinds of stable isotope labellings in GC-MS analyses. This journal is © the Partner Organisations 2014.
Schroder U.,TU Braunschweig
Angewandte Chemie - International Edition | Year: 2012
Insects and molluscs as future biological drones for military purposes or environmental monitoring systems (see picture)? Two research groups have demonstrated the successful implantation and operation of biofuel cells in snails, clams, and cockroaches. Owing to their simple circulatory systems, these invertebrates could be used in implantation studies without serious physical damage. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Dickschat J.S.,TU Braunschweig
Natural Product Reports | Year: 2010
This review describes the chemistry of the bacterial biofilms including the chemistry of their constituents and signalling compounds that mediate or inhibit the formation of biofilms. Systems are described with special emphasis, in which quorum sensing molecules (autoinducers) trigger the formation of biofilms. In the first instance, N-acyl-l-homoserine lactones (AHLs) are the focus of this review, whereas the inter-species signal known as furanosyl borate diester and peptide autoinducers used by Gram-positive bacteria are not discussed in detail. Since the first discovery of an AHL autoinducer from Vibrio fischeri a large and further increasing number of different AHL structures from Gram-negative bacteria have been identified. This review gives a summary of all known AHL autoinducers and producing bacterial species. A few systems are discussed, where biofilm formation is suppressed by enzymatic degradation of AHL molecules or interference of secondary metabolites from other species with the quorum sensing systems of communicating bacteria. Finally, the multi-channel quorum sensing system, the intracellular downstream processing of the signal, and the resulting response of whole populations including biofilm formation are discussed for the Vibrio genus that has been extensively investigated.