A recent paper in PLoS One entitled Ionizing Radiation Changes the Electronic Properties of Melanin and Enhances the Growth of Melanized Fungi describes some pretty amazing results that have gotten some press lately. The lead author, Dr Dadachova, spoke on NPR’s Science Friday last week about how melanized fungi are able to use ionizing radiation for energy as seen in the enhanced growth in their experiments.
While this is the first report of such as result, the fact that innovation occurs wherever there is free energy is not surprising. As mentioned by Arturo Casadevall this story in the spring when he was gave a seminar at Berkeley, marine organisms that live near undersea hydrothermal vents have been able to photosynthesize the infrared light emitted from the vent. He discussed the radiation utilization of melanized fungal work at the end of his talk, and said that it has been an epic process to get it published — that this work had been in review for four years at several high profile journals, but I guess that it was controversial enough to not be accepted there. I guess Nature and Science get it now since they wrote news briefs…
This work grew out of observation that fungi were growing on the walls of Chernobyl reactor and in the ground nearby and all were blackened with melanin. In some areas the ground itsself is turning black with the melanized fungi. Melanin expression is a protective response, it is highly stable and does not readily degrade even in boiling acid. Melanin is utilized by plant pathogens, free living fungi, and pathogenic fungi for a variety of purposes that mainly is thought to be absorbing free radicals and reactive oxygen species to protect the organism from damage. The pathways and importance of melanin has been studied in many fungi including one of my favorites, Cryptococcus neoformans. Much of the pioneering work on melanin has been done in Arturo Casadevall’s lab using C. neoformans. The fungus uses melanin in its capsule to aid in defense from the host immune system as non-melanized mutants are unable to survive as long in a host as the wild-type. When Cryptococcus invades the CSF it can use dopamine to synthesize melanin. Interestingly ascomycetes and basidiomycetes have a different melanin biosynthetic pathway from ascomycetes but laccases are a major component of the pathway.
[Update: added some more press links in 1st paragraph, fixed wording a little]