Scientific concept

The Chair of General Microbiology and Microbial Genetics understands itself as a research department for developmental genetics of fungi. We focus our efforts on understanding the developmental programmes and molecular signals steering sexual and parasitic interactions between partners. Our favorite organisms belong to the basal fungal division Zygomycota. The mechanisms for intercellular communication between the partners form the centre of research.

Surprisingly, sexual communication between mating types and the recognition of hosts by the mycoparasite Parasitella parasitica is mediated by the same class of molecules, the trisporoids. Biochemically, trisporoids are degradation products of beta-carotene.

The general structure of trisporic acid. Positions which are differentially substituted in nature are marked. Trisporic acid is synthesized from beta-carotene. The substance was baptized after Blakeslea trispora, a zygomycete containing three spores in its sporangia (sporangiola) -thus trispora- and being a natural overproducer of carotene and trisporic acid.

We study sexual and parasitic interactions at several complementary analytical levels: genetically, physiologically, biochemically and phylogenetically with respect to the origin of the trisporic acid system and the evolutionary connections between sexuality and parasitism. Thus, our concept requires joint efforts of scientists with many different but complementary skills. Many of our experiments are possible only by including novel and highly sophisticated synthetic approaches for generating pure trisporoid derivates and for elucidating structures of natural trisporoids from biological samples. These achievements are developed and performed in the laboratory of our cooperation partner Professor Boland at the Max-Planck-Institute for Chemical Ecology.

This interdisciplinary integrative approach opens promising options for understanding the mechanisms underlying the empirically observed diversity of trisporoid compounds. We hypothesize that the trisporoid language is generally understood in zygomycetes. There are, however, many different dialects in this chemical language that warrant specifity in partner recognition with respect to species and to the reaction that needs to be induced in the partner. Indeed we could show that apart from the order Mucorales, where trisporoids have been found as mating mediators, the trisporoid language is also used in the phylogenetically distantly related order Mortierellales. This concept is part of the cooperative Priority Programme SPP1152 by DFG (Deutsche Forschungsgemeinschaft) - http://www.ipb-halle.de/dfg/dfg-spp-1152/homepage/.

It is particularly stimulating to look at gene transfer in zygomycetes. Our favourite model organisms Absidia glauca and Mucor mucedo form sexual spores -zygospores- deliberately on appropriate media. However, like in all zygomycetes, these spores do essentially not germinate. At least they fail to do so under laboratory conditions. For practical purposes, also for strain improvement of biotechnically exploited zygomycetes, the sexual system is useless. Much more efficient than mating for recombinant formation is the parasexual gene transfer between the biotrophic fusion parasite Parasitella parasitica and its zygomycetous hosts. In the system Absidia glauca as host and Parasitella parasitica as parasite, gene transfer rates from the parasite to its host range around several percent for a single defined genetic marker. The system is as efficient as F-plasmid mediated conjugation in Escherichia coli and probably the most efficient parasexual process that has been found in eukaryotic systems.

The combination of genetic, physiological, biochemical and phylogenetic approaches is scientifically extremely charming, conceptually and experimentally. Our approach sheds light on the fundamental and general biological processes of sexuality and parasitism. In the long run, it is also extremely useful for rendering a biotechnically important group of fungi amenable for manipulative procedures and strain improvement

Anke Burmester

• Characterization of the gene cluster encompassing the tsp1 gene in Mucor mucedo
• Development of novel plasmid vectors for transformation of zygomycetes
• Improvement of transformation procedures for zygomycetes

Christine Schimek

• Molecular physiology of sexual and parasitic differentiation in zygomycetes
• Mechanisms leading to metabolic diversity of trisporoids in zygomycetes
• Cell biology of sexual differentiation: localisation of trisporoid synthesis

Kornelia Schultze

• Regulation of the tsp1 gene for 4-dihydromethyl-trisporic acid dehydrogenase by natural antisense mechanisms in the zygomycete Parasitella parasitica

Kerstin Voigt

• Molecular phylogeny of zygomycetes
• Origin of the trisporic acid system in fungi
• Molecular identification of microorganisms

Johannes Wöstemeyer

• Transfer of genes from the mycoparasite Parasitella parasitica to its hosts
• Horizontal gene transfer as a motor of evolution in zygomycetes
• Molecular diagnosis of plant and human pathogens