Microbes Muddle Shroud of Turin's Age


Science News Vol. 147

In the interplay between science and religion, science usually sides with the skeptics. But now a bit of microbial science suggests that skeptics have too quickly dismissed the possibility that the Shroud of Turin might indeed be the burial cloth of Jesus Christ, as many believe. In the 1980s, researchers examined samples from the shroud for the presence of carbon-14, a radioactive atom that decays over time. The amount found, they concluded, pegged the linen cloth as medieval, less than 700 years old. But microbes may have interfered with those dating results, making the shroud appear younger than it actually is, asserts a research team led by Stephen J. Mattingly and Leoncio A. Garza-Valdes of the University of Texas at San Antonio. The group has for years studied how various microbes can coat artifacts and natural objects with "biogenic varnishes," plastic like coatings synthesized by bacteria or fungi. From microscopic examination of small samples of the shroud, they recently concluded that some of these same varnishes coat the linen fibers. Further examination of bits of fabric by two techniques, infrared spectroscopy and mass spectroscopy, indicated that the samples were not pure cellulose, linen's main constituent. The Texas team next found that their samples harbored a number of microbes-specifically, ones that have been found to grow in natron, a bleaching agent that may have been used on the cloth in the past.

Past radiocarbon dating, suggest Mattingly and Garza-Valdes, could not distinguish between the linen's cellulose and the microbes and their coating, which may be of much more recent origin. "What you are reporting is the age of the mixture, not the age of the linen," says Garza-Valdes. To resolve the shroud's true age, the researchers hope to obtain another sample and process it with an enzyme that breaks down cellulose-and no other suspected contaminant-into glucose. They could then date the glucose by carbon-14 analysis. "If we can isolate the glucose, that will be the answer," says Mattingly.


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