Sunday, July 27, 2008

Life in strange places

In Cosmos, The Science of Everything, Lauren Monaghan's article, Silent Spring, tells a strange tale of mutating fungi found in Ukraine's Chernobyl number four reactor.

Back in 1999, scientists had sent a robot inside to survey the reactor. The robot returned with samples of a particularly black fungi, indicating an abundance of the biological pigment melanin.

Arturo Casadevall, a microbiologist from the Albert Einstein College of Medicine at Yeshiva University in New York, thought that the presence of the melanin might be significant. Melanin is typically associated with 'protective' properties. Melanin in skin, for example, absorbs and safely transforms different electromagnetic wavelengths, such as DNA-damaging ultraviolet light.

In an experiment scientist analyzed three different types of fungi, including Cladosporium sphaerospermum, the species abundant in and around Chernobyl. Using ionizing radiation from the radioactive isotope, cesium-137, they exposed the fungi to radiation doses similar to those inside the damaged reactor.

Melanin-containing fungi exposed to the radiation – even when deliberately starved of nutrients – grew significantly larger and up to 2.5 times faster than fungi without melanin and those not exposed to radiation.

Even though the melanin-containing fungus was starved of typical fungus nutrients, it prospered. Although still a tentative hypothesis, the evidence indicates that the melanin might be converting radiation into nutrients for the fungus, somewhat like how chlorophyll converts sunlight into energy for a higher plant. If true, this is astounding.

This is like the discovery of chemosynthesis around hydrothermal vents deep in the ocean. In the deep, dark ocean, a bacteria was found to metabolize hydrogen sulfide given off by the vents. A relatively diverse ecosystem (organisms such as shrimp, crabs, tube worms) was found to exist entirely upon the bacteria.

If it could happen there, perhaps it is possible that life could similarly evolve around a food chain fueled by radiation.

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