Cytology of the prokaryotic cell (Publications)
New prokaryotic isolates obtained by the Institute for Microbiology and Genetics or by other laboratories are characterized by electron microscopy. In cooperation with the Steinbüchel group in Münster/Germany, ultrastructural aspects of bacterial PHA inclusion bodies (including their boundary layer) and of other inclusion bodies are investigated by conventional electron microscopy.
Studies are in progress aimed at
the analysis of composition, macromolecular architecture, and function
of a fibrillar network present at the inner aspect of the cytoplasmic membrane
of a wide variety of prokaryotes (bacteria, archaea). Preliminary data
sugges its function as a cytoskeleton that preserves cell shape.
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Composition and dynamics of microbial biofilms (Publications)
Structure and dynamics of microbial
biofilms are essentially determined by the action of cell surfaces, mediating
contact to other organisms or the substratum. Electron microscopy helps
to localize the organisms in biofilms, antibody- and lectin coupled gold
markers help to reveal their specific sites of interaction at the cell
surface. In some terrestric ecosystems, the surfaces of rocks and soil
may be covered by biofilms consisting of green algae, fungi and cyanobacterteria.
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Prokaryotic enzyme complexes in vivo and in vitro (Publications)
By a combination of biochemical,
enzymological, immunological, electron microscopic, and molecular biological
techniques, prokaryotic enzyme complexes located in the cytoplasm, in or
attached at the cytoplasmic membrane, in the periplasm, or extracellularly
are analysed regarding size, quaternary structure, domain structure of
the subunits, and structure-function relationships.
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Structure and function of enzymes in membraneous compartments (Publications)
Reversed micelles are spherical droplets of water surrounded by a monolayer of surfactant molecules, arranged with their polar head groups towards the water pool, in a nonpolar solvent. They represent a simple model system for a biological membraneous compartment. In contrast to liposomes, it is very easy to change the size of the central water pool by variation of the water concentration of the system.
Enzymes exhibit in reversed micelles and bound to artificial phospholipid bilayer membranes up to ten-fold increase in specific activity and a temperature optimum up to 16 °C higher as compared to aqueous buffer solutions. Our investigations lead to the assumption that structure of water inside a reversed micelle and very close to phospholipid membranes differs from structure of free water and leads to these effects on enzyme function. Hence, structural and functional compartmentation of enzymes close to membranes or in narrow membraneous compartments (in living cells) is not only a fact of compartmentation by the membrane itself, but also by diverse water structures close to the membrane surface.
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Compartmentation of enzymes involved in fungal secondary metabolism
The project is funded by the Pharmaceutical Industry and aims at the localization of enzymes involved in synthesis of antibiotics in fungal cells. Immunoelectron microscopy reveals compartmentation of the complex biosynthetic pathways and helps to influence the pathways in order to obtain antibiotics with modified properties.
Figure: Fungal vacuole with colloidal gold markers (black dots) indicating antigenic sites of metabolic enzymes.