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The longevity of thermoactinomycete endospores in natural substrates.

Occupational debris from beneath the Roman fort Vindolanda, and lake sediments cored from Seamere in East Anglia were examined for the presence of viable Thermoactinomyces endospores. Up to 104 viable endospores/g dry wt were recovered from the occupational debris at Vindolanda deposited between 1850 to 1890 years ago. Highest numbers were found in layers of bracken and straw litter sandwiched between clay floors within a military building. Associated artefacts and writing tablets have been used to date the various layers. Pollen analyses on core samples from Seamere revealed one region containing a declining percentage of tree pollen and the appearance of cereal and associated weed pollens suggesting the presence of a primitive agricultural community on the shores of the lake. Samples from this section of the core, deposited ca. 1950 to 2750 years ago, contained viable thermoactinomycete endospores. These studies confirm the extreme longevity of Thermoactinomycete endospores and suggest that these organisms may be usefully employed in future archaeological and palaeoecological studies.