Biodeterioration of archaeological monuments of Taxila, Pakistan

摘要

The present research was conducted to assess the role of aeromycoflora around world heritage sites of Taxila and its relation with biodeterioration of stone monuments. The aerial mycoflora of six archaeological sites was recorded for one year to monitor the seasonal variations and transportation of fungal spores. Thirty-two fungal species belonging to twenty genera were isolated throughout the whole sampling period. The fungal genera Alternaria, Aspergillus, Cladosporium, Fusarium, Mucor, Helminthosporium, Curvularia and Penicillium were prevalent, whereas at species level Alternaria alternata was dominant followed by Aspergillus niger, Cladosporium herbarum, Penicillium chrysogenum and Fusarium oxysporum. A well-marked qualitative and quantitative seasonal variation in aeromycoflora of selected sites was recorded. Some fungal species showed restricted occurrence to a specific archaeological site of Taxila. The comparative study of aerial and surface mycoflora revealed that dominant aerial fungal species were involved in biodeterioration of monuments. The chemical composition of fungal patinas and biofilm was also carried out, and it was found that calcite, gypsum and calcium oxalate were the main minerals detected by X-ray diffraction technique. The dominant fungal species were also determined for their ability to produce organic acids in broth medium. The fungal species produce a significant amount of citric acid, acetic acid, oxalic acid, fumaric acid and gluconic acid. The different surface alterations of archaeological monuments of Taxila are due to the metabolic activities of fungal species growing on it. The present study is the first investigation about microbial decay of stone monuments of Taxila, and the results of this study will help to make a strategy for prevention of further biodeterioration of these monuments.