The Bad and the Good—Microorganisms in Cultural Heritage Environments—An Update on Biodeterioration and Biotreatment Approaches

Abstract

Cultural heritage objects constitute a very diverse environment, inhabited by various bacteria and fungi. The impact of these microorganisms on the degradation of artworks is undeniable, but at the same time, some of them may be applied for the efficient biotreatment of cultural heritage assets. Interventions with microorganisms have been proven to be useful in restoration of artworks, when classical chemical and mechanical methods fail or produce poor or short-term effects. The path to understanding the impact of microbes on historical objects relies mostly on multidisciplinary approaches, combining novel meta-omic technologies with classical cultivation experiments, and physico-chemical characterization of artworks. In particular, the development of metabolomic- and metatranscriptomic-based analyses associated with metagenomic studies may significantly increase our understanding of the microbial processes occurring on different materials and under various environmental conditions. Moreover, the progress in environmental microbiology and biotechnology may enable more effective application of microorganisms in the biotreatment of historical objects, creating an alternative to highly invasive chemical and mechanical methods.

Evaluation of Plant Origin Essential Oils as Herbal Biocides for the Protection of Caves Belonging to Natural and Cultural Heritage Sites

“…Another issue that is crucial for the biocide effectiveness is the presence of microbial biofilms. Development of biofilms, built from extracellular polymeric substances (e.g., polysaccharides, lipids, proteins, nucleic acids, pigments, enzymes), may significantly enhance the biodeterioration processes offering in parallel increased resistance of microorganisms to biocidal compounds [ 87 ]. All the aforementioned matters have to be closely monitored irrespectively of the biocide origin (natural or not) and according to the findings adjust the application frequency and maybe rotate the use of different EOs.…”

Airborne Fungi in Show Caves from Southern Spain

“…The most recurrent species isolated from rocks and speleothems and reported as producing deterioration are Cladosporium cladosporioides, Parengyodontium album and Penicillium chrysogenum [52][53][54][55]. Fungal deterioration can be evidenced by observation of structural and chemical changes using microscopic and spectroscopic techniques [56,57].…”

Fungal Deterioration of Cultural Heritage Objects

“…However, microbial deterioration of these materials occurs only under poor conservation conditions: high humidity level, soil contact, poor ventilation, and rare maintenance [81]. Even though deterioration of wood cultural heritage is a process conducted by all groups of microorganisms, fungi have the most significant potential to affect this type of historic artworks [82]. Biodegradation and biodeterioration of wood materials is predominantly dependent on its moisture content, requiring a minimum of 20% of water.…”

“…It is typical for this group of fungi to attack wood mass with high levels of humidity and low lignin content, forming a microscopic cavities inside the wood, sometimes leading to discoloration and occurrence of cracking pattern similar to brown rot (species from the genera Alternaria, Chaetomium, Daldinia, Humicola, Stemphylium, Xylaria, etc.) [79,82,83]. Soft-rot decay has been described frequently from construction timbers, ancient Egyptian wooden coffins, wooden structures of Buddhist temples, waterlogged archeological wooden material, which can be related to more tolerant growth conditions.…”

“…Additionally, the physical contact with moisture-absorbing surface can also provoke fungal decay [79]. On the other hand, fungal degradation of waterlogged and buried wood is much slower than for that found in dry environment, but once excavated decay can occur rapidly [82]. Finally, it should also be emphasized that in some cases fungal decay can be observed in extreme conditions such as in wood with 17.4% of moisture content [79].…”