A University of Cincinnati biologist has found a microbe which not only survives under extremely hot and acidic conditions; it can repair its damaged DNA using natural light.

Sulfolobus acidocaldarius is one of a special group of micro-organisms, commonly called "hyperthermophiles." These organisms require extremely high temperatures to grow and reproduce, and they have been recovered by microbiologists over the past 25 years from various hot springs, undersea vents, and other geothermal environments.

When its genetic material (DNA) is artificially damaged by ultraviolet (UV) light, S. acidocaldarius has been found to repair the damage. However, Dennis Grogan, assistant professor of biological sciences at the University of Cincinnati, found that the repair process requires assistance from the environment, in the form of visible light. This light-driven repair of DNA, known to microbial geneticists as "photoreactivation," is the first DNA repair process to be measured in a hyperthermophile.

Grogan presented his findings May 19, 1996 at the 96th General Meeting of the American Society for Microbiology. He has been investigating the basic cellular properties of S. acidocaldarius for the past six years.

In nature, S. acidocaldarius thrives in acidic, sulfurous hot springs; in the laboratory, it prefers acidic growth medium (pH=3) at about 80 degrees Celsius. Such severe conditions often cause DNA and other cellular materials to decompose. So, Grogan has been looking at how this microbe managed to protect itself.

"Since the precise structure of DNA is essential for life and reproduction, it would seem logical that the S. acidocaldarius cell should have particularly effective ways of repairing damage to its DNA," said Grogan.

Grogan tested the microbe's repair capabilities by artificially damaging the DNA of live S. acidocaldarius cells with UV radiation, whose effects on DNA are precisely kno
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Contact: Chris Curran
chris.curran@uc.edu
513-556-1806
University of Cincinnati
19-May-1996