Aspergillus versicolor and trichoderma virens as contamination agents in a musealized roman floor mosaic from the 1st century

During the Museum Regional de Arqueologia D. Diogo de Sousa new building construction, a mosaic floor from a Roman house, dating probably from the 1st century, was found. Due to it’s rarity, dimension and quality, it was integrated in the underground floor of preserves not only the “in situ” mosaic but also the vestiges of a home from the Roman Era. The mosaic panels depict geometrical decorations of granitic and limestone tesserae with opposing colours. However, the “in-situ” condition of the mosaic, with its soil base and recurrent climate dependent moisture fluctuations, created the conditions for a biocontamination to appear in more recent years. The mosaic itself was covered by a thick, white and cream microbial biofilm, which includes a large area of the mosaic and also some adjacent home-related sections. Occasionally, some radial growth spots were detected, which seem to partially eliminate the original biofilm. Samples were taken from specific, relevant areas, both from the mosaic and the house, from different surfaces and materials, as well as from the biofilm and the radial spots with wet (water) sterile swabs. Tesserae with and without contamination were also collected. Observation with SEM allowed the identification of characteristic hyphae and other fungi structures. Samples were cultured in specific fungi and algae liquid media. A small number of fungal isolates was obtained and identified through ITS amplification as Aspergillus versicolor and Thrichoderma virens. The results are in agreement with the observations made since Trichoderma sp. are fungal antagonists often used as biocontrol agents.