Publication | 广以顾继东教授课题组在《Nature Sustainability》上发表综述论文
2020年9月，广东以色列理工学院顾继东教授课题组在《Nature Sustainability》上发表题为"Microbial deterioration and sustainable conservation of stone monuments and buildings (微生物对石质文物和古建筑的破损机制与可持续性保护措施)"的综述论文（IF:12.08)。广东以色列理工学院为该论文的第一署名单位，论文的第一作者为原香港大学博士研究生刘小波(现为广东以色列理工学院研究人员)，顾继东教授为论文的通讯联系人。论文中同时署名的有日本东京农工大学片山叶子(Yoko Katayama)教授，世界知名德国文物保护微生物专家Thomas Warscheid和美国史密森尼文保中心主任Robert Koestler。
该论文对过去连续15年中顾继东教授与片山叶子教授长期在吴哥窟合作研究的一系列有关微生物对文物破损的成果和世界各地在石质材料的相关报道进行了系统的梳理，从采样方法和研究模式为基础，阐明了石质文物的生物破损是由一系列复杂的物理、化学和生物化学过程及其相互作用所导致的结果，其中水循环、文物表面的五颜六色的微生物被膜(biofilms)以及其中包含的由微生物主导的生化代谢反应过程驱动得生物化学元素循环(如碳、氮和硫等)反应导致石材的结构破损和组成分解或溶解(图1)，最终造成建筑结构的破坏和文化遗产价值的丧失。
具体而言，在不同的气候条件下和不同阶段，石质文物表面微生物被膜由各种光能自养型、化能自养型和异养型微生物组成，特定的微生物种类和群体组成可协同驱动生物地球化学元素循环(如碳、氮和硫等)，尤其是在人为污染和大气污染较日益严重的地区，微生物通过利用上述化学元素为自身养分来合成和分泌各种有机或无机酸进而破坏石质材料并同化吸收溶解析出的矿物质促进其自身繁殖和生长。此项研究成果为制定有效的文物保护科学管理策略以实现可持续文化遗产防护的长远目标提供了必要的可靠依据。
图1 吴哥窟(a, f, g)，吴哥大城(b, d, e)和柏威夏寺(c)建筑砂岩上微生物被膜及其所造成石质材料的微生物破损现状
人类文明史中包括利用和发明不同的材料，而这些材料又将历史记录留给了后代。早在新石器时期，石材就用于制作捕猎工具和日常用具，同时也是建筑与艺术品的主要原料。截至2019年，联合国科教文组织(UNESCO)已认定845处历史古迹为世界文化遗产(https://whc.unesco.org/en/list/)。然而，由于全球气候变化、人类活动、地理及环境等因素影响，重要历史文物及建筑正遭受着各种不可逆的破损，包括自然风化、生物侵蚀及人为破坏，导致了人类文明的永久消失，例如我国云冈、大同、敦煌石窟和柬埔寨吴哥窟等。此论文从文物表面微生物被膜的形成、常见石质材料理化特征、人类活动、大气污染及微生物驱动元素循环等多角度入手，详细讨论和总结了微生物侵蚀石质文物和建筑物的主要机理，并以此为基础，探讨相应的可持续保护策略以及展望未来的研究方向。
本单位顾继东教授与片山叶子(Yoko Katayama)教授(原日本东京农工大学任教，现任职于东京国立文化财团)长期研究合作(图2)，对赤道地区高热高湿条件下吴哥砂岩文物从表面微生物的无破损取样方法入手，利用最新的DNA／RNA高通量分子测序和同位素示踪技术对微生物种群组成和生物化学破损机制进行了一系列的研究，阐明了石质文物的生物破损过程中一系列复杂的物理、化学和生物过程及其相互作用的结果，揭示了文物表面微生物被膜及其关键生化代谢反应过程。双方在吴哥的长期合作研究所取得的成果已发表20余篇SCI论文，得到国际同行的广泛认可和关注，经常受邀在国际会议上做专题报告并撰写了多篇相关综述文章以及专著中有关微生物退化的章节。
图2 合作双方团队在结束2019年度采样后合影及采样现场工作实况
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Liu, X., R. Koestler, T. Warscheid, Y. Katayama, and J.-D. Gu (2020) Microbial deterioration and sustainable conservation of stone monuments and buildings. Nature Sustainability 3: 991–1004. DOI:10.1038/s41893-020-00602-5
注：此文中图一为论文中的可公开使用图片，作者拥有其它图片的版权。
Ji-Dong Gu’s Research Group at GTIIT published a review article on "Microbial deterioration and sustainable conservation of stone monuments and buildings" in 《Nature Sustainability》(IF:12.08) in September 2020. The corresponding author of this article is J.-D. Gu of GTIIT and the first author is Dr. Xiaobo Liu who was a PhD student at The University of Hong Kong and graduated in August 2020 before joining GTIIT in October. In addition, co-authors on this publication include Prof. Yoko Katayama (formerly Tokyo University of Agriculture and Technology, now Tokyo National Research Institute for Cultural Properties), Dr. Thomas Warscheid of LBW Bioconsult in Germany and Dr. Robert Koestler, Director of Smithsonian Institution Center of Conservation).
This article is a summary of over 15 years of an on-going research collaboration between Gu’s Research Group and Prof. Katayama’s working together on understanding microbial colonization, composition and biochemical active and destructive contributions to the sandstone monuments under tropical climate of high heat and humidity favorable to a wide range of microorganisms to thrive. Together with publications elsewhere on stone monuments and historic buildings, this article delineates the methodology, analytical techniques available, and processes of microbial deterioration of stone monuments involved in a series of physical, chemical and biological reactions. Among them, hydrological cycle, biofilm formation on surfaces (Fig. 1) and the biochemical processes of carbon, nitrogen and sulfur cycles are major contributors to the destruction of sandstone physical structure and finally collapse of the monument structure. The overall information is invaluable to the policy on scientific and sustainable management of cultural heritage of the world into the future to protect human civilization from destruction.
Figure 1. Photographs showing Angkor Wat (a, f, g), South Gate of Angkor Thom (b, d, e), and Preah Vihear temple and microbial colonization and different colors (c) and the deterioration and destruction
The history of human civilization includes utilization and invention of different materials at various stage of society development, and these materials also serve a range of purposes in recording the history of society and technological capability for future generations. Stone was used to produce weapons and daily working tools as well as art. UNESCO had officially 845 sites of World Cultural Heritage (https://whc.unesco.org/en/list/) registered in 2019. Because of global climate change, anthropogenic activity, local condition and geography, many of these sites are suffering from irreversible deterioration and destruction from natural, biological and human causes to result in the permanent disappearance of selective of them. The negative effects on these sites can be seen today at Yungang Grottoes, Datong Grottoes and Dunhuang grottoes in China, and also Angkor monuments in Cambodia and Southeast Asian countries. Generally speaking, sandstone and stone can be easily colonized by natural microflora to form microbial biofilms quickly under different climate conditions and at any locations, and the microorganisms develop on surfaces by phototrophic, chemotrophic and/or organotrophic life styles to make a living and interact with the local conditions and availability of the energy and carbon sources. Majority of them are involved inmetabolism of carbon, nitrogen and sulfur to thrive on the inorganic stone and they can also utilize the anthropogenic pollutants deposited to support their growth and release inorganic and organic acids to dissolve the chemical structure of the stone and support the microorganism with supplies of minerals. This article stars with biofilm formation on different types of stone, physical and chemical properties of them, human activities, air pollution and microbial element cycles of carbon, nitrogen and sulfur mainly to reveal the fundamental biochemical processes and mechanisms that are important to the destruction of sandstone and stone, so that protection policy can be drafted based on them in the long-term.
Prof. Gu of GTIIT and Prof. Yoko Katayama of Tokyo National Research Institute for Cultural Properties have been collaborate on this research initiative for the past more than 15 years with non-stop annual visiting (except this year 2020) to investigate the various aspects of cultural heritage microbiology (Figure 2). They initially tested the sampling methods that can minimize physical contact or alteration of the surface materials, reported the microbial community and composition using the newly available Next-generation Sequencing (NGS) technology for metagenomics and also metatranscriptomics analyses, quantified the nitrogen transformation reactions which resulted in an accumulation of nitrate by ammonia-oxidizing archaea and bacteria, and verified the this phenomenon with application of nitrogen-15 stable isotope labeling technique to track the biochemical reactions, and proposed a new research framework for microbiology of cultural heritage and protection. Their collaboration has resulted in a publication of more than 20 SCI papers, recognization by the scientific community and peers, and further wider collaborations with colleagues in Europe, e.g., Italy, Germany and France, and frequent invitations to deliver invited talks at international conferences and contributions to review article and book chapters.
Figure 2. A group photo after completing the 2019 annual sampling and survey at Sambor Prei Kuk in Cambodia, and shots of sampling at Preah Vihear and Beng Mealea temples
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Liu, X., R. Koestler, T. Warscheid, Y. Katayama, and J.-D. Gu (2020) Microbial deterioration and sustainable conservation of stone monuments and buildings. Nature Sustainability 3: 991–1004. DOI:10.1038/s41893-020-00602-5
Note: Figure1 in this paper is a picture available for public use, the author owns the copyright of the other pictures.
文/图：由顾继东提供
Text/Photos: Provided by Ji-Dong Gu
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