Prof. Ji-Dong Gu
Guangdong Technion – Israel institute of Technology (GTIIT), China
Abstract: Stone monuments are important UNESCO World Cultural Heritage and their protection is an international task. After the initial detection of high concentration of nitrate in sandstone of Bayon temple of Angkor Thom in Cambodia, higher abundance of the active ammonia-oxidizing archaea (AOA) than the ammonia-oxidizing bacteria (AOB) was detected by real-time reverse-transcriptional PCR. Through amendment and incubation of 15N labelled substrates, low activity of denitrifying and no significant Anammox reaction were confirmed to support the accumulation of nitrate. Recently, both dissimilatory nitrate reduction to ammonium (DNRA) and complete ammonia oxidation (Comammox) processes were also discovered on these monuments. These results collectively support a comprehensive understanding of the N cycle on stone cultural heritage in which DNRA decreases the product nitrate concentration and also at the same time provide additional new substrate for ammonia oxidation by AOA, Comammox bacteria and AOB. An internal N cycle between ammonia/ammonium and nitrate is evident and its significance is to couple ammonia oxidation reaction to incorporation of CO2 into biomass and immobilized it on surfaces of sandstone. This process alters the surface properties of fresh stone and offers reduced organic C to support heterotrophic bacteria and fungi to colonize and grow on surfaces of stone. Dissolution of CaCO3 in sandstone was confirmed and this reaction further integrates physical science and microbiology to the enlargement of pores and porosity to increase water retention and holding, and microbial activity due to the available organic C and also water, so that the N cycling reactions can be more active as discussed above. Because of these, a holistic approach with water as a central theme must be formulated in investigation of the mechanisms involved and protection of Angkor sandstone temples and architecture.
Host：Prof. Cheng Gu
Executive Editor
Nanjing University
Time：09:00am Sept 13, 2022 (Beijing time)
Zoom ID: 816 9975 7155
Bilibili: 25002335
