天梯山石窟壁画保存环境中空气细菌的季节性变化

Seasonal variation of airborne bacteria of the Tiantishan Grottoes and Western Xia Museum, Wuwei

摘要:

【背景】微生物侵蚀是古代壁画常见生物病害，影响壁画的长久保存和安全陈展。空气微生物作为壁画病害菌的主要来源，近年在文物赋存环境监测和预防性保护中引起广泛重视。【目的】对天梯山石窟壁画的2处保存地，即天梯山原址和武威西夏博物馆壁画保存环境中的空气细菌浓度、群落结构及其季节变化规律进行分析。【方法】利用生物气溶胶采样器，在2016年春、夏、秋、冬4季分别采集各位点空气样品；基于传统培养方法获得空气中细菌浓度及纯培养菌株；通过提取细菌基因组DNA、扩增其16S rRNA基因、测序和系统发生关系分析等技术研究不同位点细菌群落时空动态变化规律；结合环境监测数据，分析影响文化遗产地空气细菌群落变化的主要因素。【结果】空气可培养细菌的总浓度在16.7?1 451.8 CFU/m3范围内变动。原址第18窟和第13窟，各季节细菌浓度无显著性差异，且呈明显季节性变动规律，总体特征为夏秋季低，冬春季高。西夏博物馆外空气细菌浓度在各季节均高于库房内，冬季最高。本研究共鉴定出19个细菌属，隶属于4个门；其中不动杆菌属(Acinetobacter)、节杆菌属(Arthrobacter)、芽孢杆菌属(Bacillus)、考克氏菌属(Kocuria)、短波单胞菌属(Brevundimonas)、肉食杆菌属(Carnobacterium)、Pseudoclavibacter和薄层菌属(Hymenobacter)为优势属。【结论】天梯山石窟空气细菌群落结构具有明显的时空分布特征；相对湿度、温度及季节性降水均会影响其变化；鉴定得到部分种属具备引起壁画生物腐蚀的潜势；本研究可为当地开展遗址和馆藏环境中文物预防性保护提供本底资料。

Abstract:

[Background] Microbial deterioration is a common biological disease in ancient wall paintings, which seriously threaten the long-term safety preservation and exhibition of the wall paintings. As the main source of the harmful microorganisms to wall paintings, airborne microorganisms have attracted extensive attention in the monitoring and preventive conservation of cultural relics in recent years. [Objective] systematic survey of culturable airborne bacteria, including the concentration, community structure and seasonal variation, was carried out in environments of wall paintings preserved at Tiantishan Grottoes and Western Xia Museum, China. [Methods] Bio-aerosol sampler containing R2A agar was used for sampling in all four seasons in 2016. Traditional culture-based method to acquire the airborne bacterial concentration information and purified strains; by the extraction of genomic DNA, amplification of bacteria 16S rRNA gene region, sequencing, and phylogenetic analysis, thereafter the bacteria community composition and distribution characteristics of different study sites were clarified. Combined with environmental monitoring data, to disclosure the main factors which responsible for the dynamic changes of the airborne bacteria at the site. [Results] The concentration of culturable airborne bacteria was in a range from 16.7 to 1 451.8 CFU/m3. There was no significant difference in bacteria concentration between the Cave 18 and Cave 13, namely, the two sites at the Tiantishan Grottoes, with the obvious characteristics of the seasonal variation, briefly speaking, Winter and Spring were higher than Summer and Autumn. Meanwhile, there was significant difference in bacteria concentration between the inside and outside of the Xixia Museum, the square outside of the museum were far more than the inside of the museum at the four seasons, particularly in the winter. A total of 19 bacteria genera that affiliated to four phylum were detected, among which, Acinetobacter, Arthrobacter, Bacillus, Kocuria, Brevundimonas, Carnobacterium, Pseudoclavibacter and Hymenobacter were the dominant ones. [Conclusion] The airborne bacterial community structures of the Tiantishan Grottoes showed a distinct characteristic of the seasonal variation and spatial distribution; RH, temperature and seasonal rainfall were all have influences on the airborne bacteria distribution; some of the genera have potential of causing biodeterioration of the ancient wall paintings at this site; this study could provide supporting information for the preventive protection of cultural relics that preserved at local site and museums.