Search

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 10,000 ppm 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. [ABSTRACT FROM AUTHOR]

Methyl parathion hydrolase (MPH) from a methyl parathion-degrading Burkholderia cepacia indigenous to Thailand was purified to apparent homogeneity by three steps of column chromatography using Resource S, Sephadex G100, and Octyl Sepharose 4FF columns. Its molecular mass was determined to be 35 kDa, and the pI to be 8.5. The recombinant plasmid pGT1, containing the MPH-encoding gene, mpdB, cloned into pGEX-4T-2 was over-expressed in Escherichia coli as GST-MPH fusion protein. The recombinant MPH was purified to homogeneity by a single step, using GSTPrep FF affinity column, with the molecular mass identical to that of the native enzyme. The purified enzyme had the specific activity of about 1,600 unit mg protein and the yield of about 75%, a 39-fold increase in recovery compared to that of the native enzyme. The optimal temperature and pH were 25°C and 9.0, respectively. The MPH was stable, with its activity unchanged for 48 h at 4°C, and reduced to 50% after 5 h and to 45% after 48 h at 25°C. The enzyme activity remained 80-90% after 8-15 h at pH 6-7. Cd, Co, and Zn ions at the concentration of 1 mM enhanced the activity; while sodium dodecyl sulfate (SDS), dithiothreitol (DTT) and ethylenediaminetetraacetate (EDTA) reduced it. The enzyme also showed cross reactivity with other insecticides within the organophosphate group, and the kinetic parameters for individual substrates were investigated. Since MPH from B. cepacia has wide potential applications in detoxification and detection of organophosphate compounds, this study provides important basis for its future use. [ABSTRACT FROM AUTHOR]