Paramutation: eine Begegnung mit bleibendem Eindruck(S. 128)
Jasmin Bassler, Ortrun Mittelsten Scheid
Paramutation refers to an allelic interaction, whereby the paramutagenic allele of a gene induces a heritable change of expression at a paramutable allele. The paramutated allele becomes paramutagenic itself. Paramutation is an example that acquired states of gene expression can be inherited. Originally discovered in plants, it can also occur in other organisms. It is mechanistically connected to important epigenetic regulatory pathways and potentially relevant for evolution and population genetics.
Hilfe für gestresste Hefen: der Zellwand-Integritätsweg(S. 131)
Severin Schweisthal, Carolin Sterk, Jürgen J. Heinisch
The fungal cell wall gives shape and stability to cells and is a first barrier against adverse environmental conditions. It is a good target for antifungal drugs and important in biotechnology, life stock, and agriculture. The model yeast Saccharomyces cerevisiae is used to study cell wall synthesis, which is governed by the cell wall integrity (CWI) signal transduction pathway. Signalling is achieved through a conserved mitogen-activated protein kinase (MAPK) cascade whose human homologs are affected in various diseases.
Nachbarschaftsstudien am Ribosom: proximity dependent biotin identification(S. 134)
Oliver Valerius, Nadine Smolinski
Scaffolds mediate proximities of proteins and by that organize micro - environments. With proximity dependent biotin identification (BioID) the proteinaceous neighborhood of a bait is labeled in vivo and identified by mass spectrometry. The scaffold protein Asc1 of Saccharomyces cere - visiae locates to the head of the 40S ribosome and is involved in signaling and translation. To monitor Asc1-proximate proteins and their local dynamics we combine BioID with stable isotope labeling with amino acids in cell culture (SILAC).
Aus zwei mach eins: die Biosynthese der Phenazine(S. 137)
Christina Diederich, Mario Leypold, Rolf Breinbauer, Wulf Blankenfeldt
The phenazines are colored secondary metabolites that many bacterial species produce in such large quantities that they are visible to the naked eye. Phenazines are redox-active, enabling them to act as broad-spe - cificity antibiotics and as virulence/survival factors as in the case of the blue pyocyanin produced by the opportunistic pathogen Pseudomonas aeruginosa. Here, we review the current understanding of their bio - synthesis from chorismic acid.
Fluorierte Tenside und native Nanodiscs für die Membranproteinforschung(S. 140)
Carolyn Vargas, Erik Frotscher, Rodrigo Cuevas Arenas, Anne Grethen, Sandro Keller
Integral membrane proteins are important but challenging research subjects. Various membrane mimetics have been developed that should preserve the native structure and function of membrane proteins while rendering them amenable to biophysical, biochemical, and structural investigations. Here, we summarize recent progress with fluorinated surfactants and amphiphilic copolymers, two unconventional membrane mimetics that possess considerable advantages over canonical detergents or lipid vesicles.
Erzeugung virtueller 3D-Bilder mit jedem Lichtmikroskop oder REM(S. 143)
Manfred Rohde, Heribert Cypionka, Eckhard Völcker
A major issue of microphotography is the limited depth of focus. This problem can be overcome by taking series of images (z-stacks), which are processed by focus-stacking software to extract a sharp image with an infinite depth of focus. Furthermore, a depth map describing the z-positions of the sharpest pixels is produced, that can be used to generate virtual 3D images. Here we describe the freeware program PICOLAY and its use with light- and scanning electron microscopy (SEM). For SEM, we show different ways to produce stereoscopic images, based on only two or even a single image.
DNA-Metabarcoding – ein neuer Blick auf organismische Diversität(S. 147)
Alexander Keller, Gudrun Grimmer, Wiebke Sickel, Markus J. Ankenbrand
Taxon identification is one of the fundamental challenges in biological research. Usually, classifications are based on specimen morphology, sometimes supported by their behaviour, ecology or biochemistry. Technological advances now allow using genomic fragments as a taxon barcode. With the latest developments of high-throughput sequencers this can go even further: identifying complete assemblages simultaneously, with various applications in ecology, conservation, forensics and health security.
Wasserzeichen in synthetischen Genen(S. 151)
Michael Liss, Ralf Wagner
Like other high-value products labelling of genes or organisms will become important not only to pinpoint their identity, origin, or spread, but also for intellectual property, classification, bio-security or legal reasons. An adaptation of steganographic techniques used in digital media protection offers a versatile method to inseparably interlace digital watermarks into coding genes.
Anwendungen & Produkte
Neues Enzym mit Reverse Transkriptase- und DNA-Polymerase-Funktion(S. 164)
Ramon Kranaster, Jessica Zeller, Birgit Kühn, Andreas Marx
Reverse transcriptions under high temperatures can be performed with a new designed, thermostable DNA polymerase. This DNA polymerase was generated from Taq DNA polymerase by directed evolution in multiple rounds of mutagenesis and screening. The new DNA polymerase combines an artificially induced reverse transcriptase activity with the natural thermostability of Taq DNA polymerase. Potential applications are depicted here.
Robuste industrielle Bioprozesse: vom Labor- zum Industriemaßstab und zurück(S. 204)
Stefan Junne, Peter Neubauer
Scale-up of bioprocesses remains a challenge and represents a barrier for novel production processes. Feeding of substrate solution by the commonly applied fed-batch mode leads to heterogeneities in the fluid phase in industrial scale bioreactors. This in turn affects the metabolic activity of cells. This article describes the development of scale-down concepts and observed cellular responses under oscillatory cultivation conditions. These present strategies build a basis for improved scaledown approaches.
Pestizide im Boden – Was bleibt von ihnen?(S. 208)
Matthias Kästner, Anja Miltner, Karolina M. Nowak
Many pesticides are degradable by bacteria and fungi. However, some transformation products remain in soil. For approval, the fate of the compounds needs to be assessed in test procedures that enable the determination of extractable or non-extractable residues (NER). Results with 13C labelled pesticides show that easily degradable compounds are mineralised and converted to microbial biomass. After cell death microbial necromass is a major constituent of the NER without toxic potential.
Akkurate Bestimmung der Plasmidkopienzahl pro Zelle(S. 211)
Michael Jahn, Carsten Vorpahl, Dominique Türkowsky, Susann Müller
Plasmids are circular DNA molecules that are used as gene vectors in countless applications. They are easy to manipulate and transfer, but can also vary considerably in copy number between individual cells. In this article, a model expression system with a large amount of heterogeneity is presented. We used flow cytometry and digital PCR to count the number of plasmids in sorted sub-populations. Finally, heterogeneity could be attributed to the expression plasmid being either present or absent in bacterial sub-populations.