The active microbes and biochemical processes contributing to deterioration of Angkor sandstone monuments under the tropical climate in Cambodia – A review

Abstract

Abstract Angkor monuments/temples in the Southeast Asia are UNESCO World Cultural Heritage of the Khmer Civilization and they require preservation and protection from destruction. In this article, activity- and process-based approaches are used to present the current available results on the active microorganisms and their biochemical processes associated with the biodeterioration of sandstone cultural heritage under the tropical climate in Cambodia. Such information is important for effectively protection and management. Severe deterioration of sandstone monuments is a result of weathering processes of a combination of physical, chemical and biological forces, including both natural and anthropogenic ones. Given the fact that water is an important natural factor affecting the stability of sandstone cultural heritage under the tropical regions, subsequent microbial colonization and contribution to the deterioration of sandstone have been investigated with both culture-dependent and culture-independent techniques to provide information about the microbiota associated with the sandstone. Recent data show that both sulfur and nitrogen cycles are active biochemical processes by specific microorganisms on sandstone temples/monuments in the tropical region. Both sulfur-oxidizing bacteria and fungi are active involved and, more recently, ammonia-oxidizing archaea (AOA) are implicated with higher abundance than ammonia-oxidizing bacteria (AOB) on sandstone monuments. It is clear that a research paradigm shift is taking place on microbiology of cultural heritage, and the active, and biochemically and physiologically functional microbes are focused to advance our fundamental understanding and knowledge on the biodeteriogens for a better protection and management of cultural heritage. Biochemically and physiologically functional and important microorganisms, as well as the biochemical mechanisms involved, shall be focused in order to advance the basic research on cultural heritage, while providing essential information for its protection, including Angkor sandstone temples and monuments.