太原北齐徐显秀墓壁画真菌群落组成与菌害成因

Fungal community composition on normal and moldy mural in Xu Xianxiu's tomb of Northern Qi Dynasty, Taiyuan

【目的】确定壁画病害真菌群落组成,解析影响病菌发生的关键环境因子,为墓室壁画的科学保护提供依据。【方法】利用无菌解剖刀分别采集白色霉变与无明显霉变壁画样品;使用扫描电子显微镜(SEM)分析病害真菌微观形态特征;通过提取样品基因组总DNA、扩增真菌ITS区、构建克隆文库、测序和系统发生关系分析等技术研究壁画真菌群落组成与结构特点;结合温度与相对湿度监测,分析诱发壁画霉变的环境成因。【结果】霉变壁画表面有大量菌丝体,分生孢子大小为(1.5-2.0)μm×(1.0-1.5)μm。霉变壁画克隆文库序列分别与NCBI数据库中白色侧齿霉属(Engyodontium)和支顶孢属(Acremonium)真菌具有较高的相似度,白色侧齿霉菌(Engyodontium album)为优势病害菌(98.1%);无明显霉变壁画克隆文库序列分别与青霉属(Penicillium)、曲霉属(Aspergillus)、链格孢属(Alternaria)、假丝酵母属(Candida)、毛壳菌属(Chaetomium)和白色侧齿霉属真菌高度相似,无绒毛青霉菌(Penicillium laeve)为优势菌(77.4%);所有文库序列均属于子囊菌门(Ascomycota)。监测期墓道下部环境温度在-0.3-17.6°C之间波动,相对湿度长期在80%-100%之间变化。【结论】霉变与无明显霉变壁画中真菌群落组成差异较大;白色侧齿霉菌是引起墓道壁画霉变的主要病害菌;墓道下部相对湿度常年较高是诱发壁画霉变的关键环境因子;有必要开展壁画菌害区域的抢救性防护,并实施一定的环境控制措施以保护该考古遗址古代壁画。

[Objective] We explored the fungal community composition on mural surface, to analyze the major environmental factors that induce the explosion of fungal disease, and to provide the basis for the scientific conservation of murals. [Methods] Mural samples with and without whitish moldy necrosis were carefully and separately collected by sterile scalpel. The Scan Electronic Microscope（SEM） was used to analyze microcosmic features of fungus that caused mural biodeterioration. By the extraction of total genomic DNA, the following steps should be the amplification of fungal ITS region, clone library construction, sequencing, and phylogenetic analysis, thereafter the fungal community composition and structure characteristics were clarified. Combined with temperature and relative humidity（RH） monitoring, the environmental factors related to fungal growth can be figure out. [Results] A large amount of mycelia existed on mildewed murals, the volume of conidia ranged among 1.5-2.0 μm multiplied by 1.0-1.5 μm. Most of clone library sequences in mildewed murals were much similar to genera Engyodontium and Acremonium, of these fungi Engyodontium album was a dominant fungus（98.1%）; however, sequences from mural samples without mildew were more similar to genera Penicillium, Aspergillus, Alternaria, Candida, Chaetomium and Engyodontium, in which Penicillium laeve was a dominant species（77.4%）. All sequences belonged to Ascomycota in our study. The temperature below the tomb tunnel varied from-0.3 °C to 17.6 °C, and RH varied mostly from 80% to 100%. [Conclusion] The fungal community composition in the moldy murals was distinct different from murals without apparently moldy necrosis. Engyodontium album was the dominant disease fungus which caused mildew of murals. Perennial higher RH below the tomb tunnel must be the primary environmental factor that induced mildew. As a result, it is necessary to carry out some salvage protection and certain environmental control measures for conservation of ancient murals in this archaeological site.