Research profile of Prof. Dr. Wolfgang Liebl

One of the main interests of the group is the analysis of polysaccharide and oligosaccharide breakdown and utilization by microorganisms adapted to extreme habitats. In particular, we have studied cellulose, xylan and starch degrading enzyme systems from extreme thermophiles and hyperthermophiles, i. e. organisms that grow optimally at 80°C or higher. These organisms represent very deep branches within the prokaryotic lineages of the phylogenetic tree of organisms. Extremophilic prokaryotes are often found in hot, geothermally heated habitats (heated marine sediments, black smokers in the deep sea, terrestrial hot springs, solfataric fields).

We are interested in the biochemical properties, the molecular structure and catalytic mechanism, the function(s) of non-catalytic domains, and the cellular localization of unusual glycoside hydrolases and transferases. Other projects in the field of extremophilic microorganisms deal with the enzymology and molecular biology of thermoalkaliphiles and thermoacidophiles. We have completed the genome sequence of the extreme thermoacidophilic archaeon Picrophilus torridus, the most acidophilic thermophile known to date. P. torridus grows at temperatures up to 65°C and pH values even below 0. The objectives of these studies are to better understand the evolutionary, metabolic and molecular mechanisms that allow this organism to withstand and thrive under such hostile environmental circumstances.

Various projects at the department deal with biotechnologically relevant bacteria, including Bacillus licheniformis, Corynebacterium glutamicum, Gluconobacter oxydans and solventogenic clostridia. Molecular biological, genetic, physiological and fermentation methods are employed to study traits such as central metabolism, enzymology and biotechnological applications.

Also, the group is interested in the characterization of genome (metagenome) structures of various microbial habitats. It is widely accepted that incredible microbial diversity exists in complex microbial consortia. Doubtlessly, the unexplored enzymatic diversity space is also tremendous. However, less than 1% of the microorganisms can be cultivated. DNA libraries are constructed from microbial consortia in order to explore the genetic diversity of the different environments. Also, classical activity-based screens are used for the isolation of genes for novel enzymes useful for biotechnology. Examples of enzymes we are interested in include (hemi)cellulolytic and amylolytic enzymes, sugar isomerases, and dehydrogenases. The microbial community structures of the environmental samples are investigated via 16S rDNA analysis.