CS36 Ultraviolet Radiation
Date: Friday, June 14, 2002
Time: 11:15:00 AM
Location: Sidney
 
SandersRW, Temple University, Philadelphia, USA, rsanders@nimbus.temple.edu
O’Brien, A, , Temple University, Philadelphia, USA, obrien@astro.temple.edu
 
A MAJOR ROLE FOR PHOTOENZYMATIC REPAIR (PER) IN A FRESHWATER HETEROTROPHIC FLAGELLATE EXPOSED TO UV-B RADIATION
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Photoenzymatic repair (PER) reverses specific damage to DNA resulting from exposure to UV-B radiation. It is dependent on an enzyme (photolyase) requiring UV-A and visible light. UV-A radiation can also be damaging - usually through formation of reactive oxygen species. In laboratory experiments, a heterotrophic nanoflagellate (HNAN) isolated from an oligotrophic lake was exposed to three UV-B intensities. The maximum intensity used approximated full solar exposure on a clear day near summer solstice at 41 degrees N latitude. Treatments included exposure to: 1) UV-B radiation alone; 2) UV-B plus repair radiation (UV-A and visible wavelengths); 3) repair radiation alone; plus 4) a dark control. HNAN suffered 100% mortality at all intensity levels when exposed to UV-B alone. HNAN in treatments receiving UV-B plus repair radiation showed positive population growth that was inversely related to the UV-B exposure level. HNAN in treatments exposed to repair radiation alone and in dark controls had rapid and similar population growth. This flagellate, with a capacity for photoenzymatic repair and little if any sensitivity to UV-A, is well adapted to a high UVR environment.