Molecular identification of fungi colonizing art objects in Thailand and their growth inhibition by local plant extracts.

Abstract

In this initial attempt to identify fungi predominantly colonizing art objects, mural paintings and a bas-relief, at 12 archaeological sites in the central and western parts of Thailand, 13 fungal isolates were identified using morphological technique and estimated for their prevalence frequency at each site. Five main genera of fungal community found were Aspergillus, Fusarium, Curvularia, Penicillium, and Neurospora. These fungi were further identified to species level by molecular method utilizing nucleotide sequence homology analysis of the conserved internal transcribed spacer (ITS) region. Environmental factors such as temperature, relative humidity, and the opening or closure of the temples did not have any influence upon the fungal type. From the area-based distribution, Aspergillus was found at all collection sites, while Fusarium was found in Bangkok, and Ratchaburi and Petchaburi provinces in the western part of the country. Curvularia was found mostly in Phra Nakhon Si Ayutthaya and Lopburi provinces, and in one temple in Petchaburi. From the phylogenetic relationship, these prevalent fungi were divided into three closely related groups: Aspergillus and Penicillium, Fusarium and Neurospora, and Curvularia. In addition, growth inhibition of the fungi by local plant extracts of betel leaves, custard apple leaves, mangosteen peel, and guava leaves at 10,000ppm were investigated. Mangosteen peel extract gave the highest fungal growth inhibition for all the Curvularia tested, being 68.3%, 65.6%, and 60% for C. verruculosa, C. geniculata, and C. lunata, respectively. Guava leave extract also yielded highest growth inhibition of 64.4% for C. verruculosa. Both betel leave and custard apple leave extracts showed the highest inhibition towards A. fumigatus, at 65.1% and 61.8%, respectively. The results obtained here are basic information necessary for future applications in the biological prevention of art objects, and the design of appropriate measures for preventive conservation of Thai cultural heritage.