Geomicrobially induced deterioration of stone monuments and buildings contributes to a considerable loss of world cultural heritage, especially when exposed to a changing climate or environment. The active biodeterioration processes typically involve biochemical activities and cooperation among functional microorganisms in epilithic biofilms, which assimilate mineral nutrients and metabolize anthropogenic pollutants through biogeochemical cycles. Development of any effective mitigation strategies requires the comprehensive understanding of such processes. We focus on how microbes contribute to the biodeterioration processes through their activities and biogeochemical cycles of elements, discuss biochemical mechanisms involved and provide innovative strategies for sustainable conservation of stone monuments and buildings. Biodeterioration of stone monuments and buildings can lead to a loss of world cultural heritage. This Review discusses the role of microbes in the deterioration processes, the biochemical mechanisms involved and possible strategies for sustainable conservation of stone monuments and buildings.

Microbial deterioration and sustainable conservation of stone monuments and buildings

Controlling biodeterioration of cultural heritage objects with biocides: A review

Natural biocides for the conservation of stone cultural heritage: A review

This review elucidates current knowledge on the significant role of fungi and lichens in the biodeterioration of stone monuments. The effect caused by many epilithic lichen species in the deterioration of different types of stone has been extensively investigated and demonstrated. Nonetheless, many aspects of the deterioration mechanisms of microcolonial fungi (MFC) and endolithic lichens are still to be proved. An interesting hypothesis has recently been put forward involving the secretion of siderophores like compounds. Lichens can provide bioprotection for stone surfaces, acting as a barrier against weathering, retaining moisture, increasing waterproofing, reducing thermal stress and erosion, and absorbing pollutants. Nevertheless, the evaluation of biodeterioration vs. bioprotection cannot be generalised, since it can vary according to the behaviour of different species, as well as being affected by both the lithotype and the environment. In addition to the laboratory studies, more field studies of biological communities are required, to analyse their establishment and succession in natural conditions and after conservation treatments. In order to guarantee the best decision for stone conservation, cleaning operations should not be based on a generalised approach, but should rather be based on a careful evaluation of different aspects concerning biodeterioration and bioprotection.

K. H. Moon

Papers

Biological colonization patterns on the ruins of Angkor temples (Cambodia) in the biodeterioration vs bioprotection debate

Pyrenocarpous lichens in Cambodia, with the description of Celothelium longisporum sp. nov. Pyrenulales.