Pinheiro, CatarinaMiller, Ana ZéliaVaz, PatríciaCaldeira, Ana TeresaCasanova, Conceição2023-03-142023-03-142022-12-112571-9408PURE: 55636350PURE UUID: 927ac03f-c950-4792-8ba2-719ebc7ea638Scopus: 85144843713WOS: 000902623600001http://hdl.handle.net/10362/150559Funding Information: A.Z.M contribution is supported by the Spanish Ministry of Science and Innovation (MCIN) under the Ramón y Cajal contract (RYC2019-026885-I), and the intramural project PIE_20214AT021 from the Spanish National Research Council (CSIC). Publisher Copyright: © 2022 by the authors.The Alcobacenses are one of the most important Portuguese collections of Monastic codices. During a campaign study to further advance our knowledge on this important legacy and its state of conservation, a heavily deteriorated codex (ALC.338) stood out due to the presence of purple stains on the lower margins on virtually all folios. In some of them, the purple stains are accompanied by yellow and brown patches as well. Also noticed was the presence of these purple spots on the white tawed leather covering the codex. The codex was analyzed macro and microscopically, chemically and biologically using state-of-the-art technology such as next-generation sequencing. The biological deterioration associated with the appearance of these purple spots arises from the inside out and reveals significant abundance of the bacterial genus Saccharopolyspora sp., which accounted for 86% of the bacterial genera identified. For the fungal population, the most common genus was Malassezia sp. Visual inspection of the sample confirmed the presence of fungal and bacterial biofilms. Pressing questions, comparison to similar studies and future perspectives are also given.144953592engbiodeteriorationmeaslesNGSparchmentpurple stainsConservationArchaeologyMaterials Science (miscellaneous)SDG 3 - Good Health and Well-beingjournal article10.3390/heritage5040212https://www.scopus.com/pages/publications/85144843713