Melanin is effective in protecting fast and slow growing fungi from various types of ionizing radiation
Claudia Pacelli ; Ruth A. Bryan ; Silvano Onofri ; et al. ; - ASI Sponsor
Feb - 2017
DOI: 10.1111/1462-2920.13681

journal : Environmental Microbiology

Volume : 19 ; Issue : 4
type: Article Journal

Melanin is a ubiquitous pigment with unique physicochemical properties. The resistance of melanized fungi to cosmic and terrestrial ionizing radiation suggests that melanin also plays a pivotal role in radioprotection. In this study, we compared the effects of densely-ionizing deuterons and sparsely-ionizing X-rays on two microscopic fungi capable of melanogenesis. We utilized the fast-growing pathogenic basiodiomycete forming an induced DOPA-melanin, Cryptococcus neoformans (CN); and the slow-growing environmental rock-inhabiting ascomycete synthesizing a constitutive DHN-melanin, Cryomyces antarcticus (CA); melanized and non-melanized counterparts were compared. CA was more resistant to deuterons than CN, and similar resistance was observed for X-rays. Melanin afforded protection against high-dose (1.5 kGy) deuterons for both CN and CA (p-values < 10−4). For X-rays (0.3 kGy), melanin protected CA (p-values < 10−4) and probably CN. Deuterons increased XTT activity in melanized strains of both species, while the activity in non-melanized cells remained stable or decreased. For ATP levels the reverse occurred: it decreased in melanized strains, but not in non-melanized ones, after deuteron exposure. For both XTT and ATP, which reflect the metabolic activity of the cells, larger and more statistically-significant differences as a function of melanization status occurred in CN. Our data show, for the first time, that melanin protected both fast-growing and slow-growing fungi from high doses of deuterons under physiological conditions. These observations may give clues for creating melanin-based radioprotectors.

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Notes : Acknowledgments and Funding Sources[...] L.S. acknowledge the ASI (ItalianSpace Agency) for funding BIOMEX-MCF [...]