What an awesome science story:
First, researchers grew enough fungus to give dandruff to 10 million people. Next, they sequenced its genes. Then they found out that not only does an icky fungus live on your head and cause dandruff - but it could be having sex. On your head. Right now.
It's Malassezia globosa, and it's another one of those commensal organisms that has a varying range of pathological effects, including serious systemic infections in some infants. Here's what Wikipedia has to say:
Recently, identification of Malassezia on skin has been aided by the application of molecular or DNA based techniques very similar to those used by forensic scientists to identify criminal suspects. These investigations show that in humans the species causing most skin disease, including the most common cause of dandruff and seborrhoeic dermatitis is M. globosa. The skin rash of tinea versicolor (pityriasis versicolor) is also due to infection by this fungi [sic].
As the fungus requires fat to grow, it is most common in areas with many sebaceous glands: on the scalp, face, and upper part of the body. When the fungus grows too rapidly, the natural renewal of cells is disturbed and dandruff appears with itching (a similar process may also occur with other fungi or bacteria).
Aside from the details about this fungus, the story is interesting because it illustrates the extent to which genome sequencing has become available in disease research. This work -- entire genome sequencing and analysis -- was done by a lab at Procter and Gamble. There's a bunch of stuff in Nature this week on the uses of whole-genome sequencing in evolutionary analysis and functional inference.
For research into pathogen-host interactions, like this work, having whole-genome sequences provides a new luxury that once came at great expense -- playing with data to find interesting hypotheses. It used to be that testing every wrong hypothesis required an expensive set of experiments. Now, many wrong hypotheses can be sorted out right away, and several may present themselves that you would never have thought of without the new data.