This unexpected discovery was made accidentally by a student learning to prepare bone sections for microscopic observation. She happened to u se the only microscope available at the time, a fluorescing microscope used to identify samples by shining ultraviolet light on them. Bands of yellow green, characteristic of the antibiotic tetracycline, glowed on her samples. The bone, it turned out, c ame from mummified remains from a Nubian cemetery in the Sudan and dated from between AD 350 and AD 550. Apparently the tetracycline got into the Nubians diet by accident, through Streptomyces, a bacterium that manufactures tetracycline and makes up mor e than half of the bacteria in Nubian soils.
Researchers believe it grew on grain stored at the bottom of mud bins.
Since the drug is deposited only on actively growing bone surfaces, banded patterns on bone samples support the theory that the antibiotic was only an occasional part of the Nubians diet. Struck by periodic famine, the Nubians should have been plagued by infectious diseases, but studies of scar tissue in the bone samples indicate a very low incidence of such dise ase. Surprisingly, tetracycline levels found in the bone samples equal levels prescribed by modern doctors. E. the long-term effects of the use of antibiotics 11. B. the discovery of mummified remains of many elderly persons.