Biofilms and Biodeterioration: The Case of an Ancient Indian Monument

Abstract

Historical buildings are substantially built with sedimentary rocks, especially limestone, and form an important component of a country’s cultural heritage. The monuments are exposed to external environmental forces (humidity and temperature) that facilitate the proliferation of microorganisms and biofilms in an ecological succession. Feroz Shah Kotla is an ancient monument in Delhi, India, dating back to 1354 ad, and constructed of limestone, and with a discoloured façade now. The main objective of the present study was to characterise the biofilm present in areas of monuments exposed to sun and shaded areas, as influenced by two seasons—winter and monsoon (rainy), in terms of moisture, chlorophyll, protein and exopolysaccharide (EPS) as a function of carbohydrate concentration. The moisture, protein and EPS contents were higher in samples obtained from sun-exposed areas of rainy season samples and least in shaded areas of winter samples, while the chlorophyll content was highest in sun-exposed winter samples. The ICP-MS analysis showed that Ca concentration was highest (15,967.92 µg−1). Scanned electron microscope images show the presence of coccoid, bacillus and filamentous forms of microorganisms, and sparser in the dry season. The results of the present study provide significant clues that the deterioration of such ancient monuments is correlated to the establishment and continued presence of biofilms which eventually weaken and corrode the surface; appropriate conservation actions can be congruent in targeting biofilms successfully.