Fungi with history: Unveiling the mycobiota of historic documents of Costa Rica

Abstract

Through nondestructive techniques, we studied the physicochemical characteristics and mycobiota of five key historic documents from Costa Rica, including the Independence Act of Costa Rica from 1821. We determined that for documents dated between 1500 and 1900 (i.e., the Cloudy Days Act, the Independence Act, and two documents from the Guatemalan Series from 1539 and 1549), the paper composition was cotton, whereas the 1991 replicate of the Political Constitution from 1949 was made of wood cellulose with an increased lignin content. We also determined that the ink employed in 1821 documents is ferrogallic, i.e., formed by iron sulfate salts in combination with gallic and tannic acids. In total, 22 fungal isolates were obtained: 15 from the wood-cellulose-based Political Constitution and seven from the other three cotton-based documents. These results suggest that cotton-based paper is the most resistant to microbial colonization. Molecular identifications using three DNA markers (i.e., ITS nrDNA, beta-tubulin, and translation elongation factor 1-alpha) classified the isolates in eight orders and ten genera. The most frequent genera were Cladosporium, Penicillium, and Purpureocillium. Of the isolates, 95% presented cellulolytic activity correlated to their ability to cause deterioration of the paper. This work increases the knowledge of the fungal diversity that inhabits historic documents and its relationship with paper composition and provides valuable information to develop strategies to conserve and restore these invaluable documents.