The Study Of Microorganisms Diversity On Discolored Fresco In Mogao Grottoes

Mogao grottoes is well-known due to its amazing sculptures and ancient wall paintings. Its construction started from the year366AD. Having Experienced the construction of the Northern Dynasties, Sui, Tang, the Five Dynasties, Western Xia, Yuan dynasties, Mogao grottoes has a great scale. There have734existing caves in Mogao Grottoes, with2415clay sculptures. The area of murals is more than45,000square meters. Mogao Grottoes is1600meters long from north to south. Mogao Grottoes is the world’s current best-preserved and largest,exquisite art of Buddhist Holy Land. However it suffered from many factors like color distortion, collapse, salts problems, lost of painting layers, sand blown by wind, and biological deterioration etc. The physical and chemical research of Mogao Grottoes rock mass structure have made great progress, but research of microorganisms have some shortcomings in damaged mural. We selected the typical caves to research the relationship between microbial community and discolored fresco, caves layer, restoration materials.In the end of October2011, we collected samples in No.53, No.149, No.251, No.469cave in Mogao Grottoes. We investigated microbial diversity and analysis its function through culture and molecular biology methods.In our study, microorganisms diversity in discolored fresco is richer than control goup. Culturable bacteria including Pseudomonas, Bacillus. Deinococcus is the unique culturable bacteria from the surface of discolored fresco. In the first and second layer, the dominant species is Proteobacteria while secondary is Firmicutes when analysed by molecular biology methods. In the third layer, the percentage of Firmicutes is higher than Proteobacteria. Culturable bacteria diversity is the richest in the second layer. Pseudomonas, Bacillus are common culturable bacteria species in this three layers. We found that layers have an obvious influence on compositions of fungi and culturable bacteria through the NMDS analysis.The composition of bacterial community cultured and isolated from murals been used with restorative materials has no significant difference from that in common murals.The result of the experiment screening and isolating bacterial under different temperatures and pH gradients shows that37℃is a suitable temperature for bacterial to grow. At this temperature, the diversity of culturable bacterial is richer than other temperatures. The diversity of culturable bacterial reduced when be cultured at15℃, which is the average temperature in Mogao Grottoes. With the increase of pH, diversity of culturable bacterial has a decreasing trend. The environmental characteristics of Mogao Grottoes include low temperature and high degree of salinity. In this extreme condition, most of the culturable bacterial was inhibited. Therefore, the extremely environment is the best preserver of murals.In summary, our study suggests that one factor causing discolour of murals is the quantity and diversity of microorganisms in Mogao Grottoes. The quantity and diversity of microorganisms should be effectively controlled in order to keep a banlance between conservation and stakeholders for the sustainable utilization.