In biology, you learned that the penicillin-producing mold fungus Penicillium chrysogenum only reproduces asexually through spores - it has been taught that way for much of the last century. But a group of researchers now say that the fungus also has a sexual cycle, two "genders". 

In 1928, anti-bacterial researcher Alexander Fleming demonstrated (after discovering it serendipitously following years of research) the formation of penicillin in Penicillium chrysogenum. To date, there is no other known producer of that antibiotic.

Unlike in animals, sexual reproduction in fungi is not the rule. Most reproduce via spores which, in the case of molds, occur as white, green or black deposits on spoiled food. These spores only bear the genes of one parent fungus.  So it was thought about Penicillium chrysogenum .

"Five years ago we already detected the existence of so-called sex genes in Penicillium chrysogenum", says Prof. Ulrich Kück from Ruhr-Universität . Now, they have discovered specific environmental conditions in which the fungus actually reproduces sexually. They bred fungal strains in the dark under oxygen deprivation conditions in a nutrient medium supplemented with the vitamin biotin. The offspring exhibited new properties, both at the molecular level, as well as in their phenotypes.

Using microarray analysis, the biologists also investigated the activity of all the approximately 12,000 genes of the mold fungus. The result: the sex genes control the activity of biologically relevant genes, for example those for penicillin production.

"We presume that the findings can also be applied to other fungi", says Kück, "such as Penicillium citrinum and Aspergillus terreus that produce cholesterol-lowering statins, or Penicillium brevicompactum and Tolypocladium inflatum, which produce immunosuppressives that are used in all organ transplantations". 

Published in PNAS.