MSA - Cell and molecular biology/Physiology & Genetics
Walberg, Eric , Volk, Thomas .
Phenomenological studies of possible radiotrophy in melanin and carotenoid producing fungi.
Pigments protective against ultraviolet radiation are ubiquitous in nature, being selected for in habitats with high exposure to ionizing radiation. Examples include melanins, carotenoids, and a diverse group of small aromatic molecules (SAMs). These compounds contain conjugated double bonds that confer a wide absorbance spectrum, melanin exemplifying the extreme case. These compounds were previously thought to serve merely photoprotective and antioxidant roles in fungi. However, recent studies (Dadachova et al. 2007 PLoS ONE 2(5): e457 doi:10.1371/journal.pone.0000457) have suggested that melanin-containing fungi may be able to capture energy from ionizing radiation for metabolic use. Thus far, no in-depth mechanism has been proposed. Our experiments have continued to study these phenomena by varying the location of the melanin. Our initial experiments have dealt with radiotrophy as it pertains to the presence of melanin, comparing effects of location in the cell wall (where melanin is typically formed outside the cell membrane) versus merely in solution. To test this, non-melanized Cladosporium, Cryptococcus and Exophiala were grown in flasks and irradiated by 137Cesium sources. To these cultures, melanin from outside sources was added. We compared fresh-extracted melanin, which contains cells wall components and melanin-associated proteins, with acid-hydrolyzed melanin, supposedly devoid of hydrophilic groups and proteins. For both sets of irradiated flasks, at several time points the cultures were compared for growth parameters, such as number of viable cells, dry weight, and cell dimensions. The controls consisted of melanized cultures without additional melanin and non-melanized cultures without additional melanin, along with all four sets of flasks (experimental and control) that were not irradiated. Finally, we have examined whether molecules with some similar ecological roles, such as carotenoids of the red basidiomycete yeast Rhodotorula, also show growth toward, or increased growth in, ionizing radiation, using similar sets of experiments.
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Tom Volk's Fungi
1 - University of Wiscosin- La Crosse, Biology, 3005 Cowley Hall, La Crosse, WI, 54601, USA
2 - University of Wisconsin- La Crosse, Biology, 3005 Cowley Hall, La Crosse, WI, 54601, USA
Presentation Type: Oral Paper:Papers for Topics
Location: White Pine/Cliff Lodge - Level C
Date: Monday, July 27th, 2009
Time: 11:00 AM