Fascinated by a curiosity: Dieter Mollenhauer and Geosiphon pyriformis

Geosiphon pyriformis is until now the only known example of a non-septate (i. e. coenocytic) soil fungus that lives in endosymbiotic association with a cyanobacterium as photobiont, namely Nostoc punctiforme. Twenty five years ago relatively little was known on Geosiphon, and the organism was considered more or less as a curiosity. However, since about 1990 research on the Geosiphon symbiosis has been intensified with the result that now the organism serves as a model system for formation and functioning of endocytosis and, initially unexpected, for arbuscular mykorrhiza. The following article aims to illustrate the important role Dieter Mollenhauer and its wife Resi have played in the research on Geosiphon.