Ancient buildings remind us of the grand achievements of human past, but these large buildings are not immune to destruction by small lifeforms. The Old Cathedral of Coimbra, Portugal is a UNESCO World Heritage Site suffering from biodegradation: destruction due to microbial life. Scientists are studying the source of this biodegradation, with the hopes that understanding the microorganisms involved will provide solutions for restoration and preservation for future generations.
The microcolonial black fungus, Aeminium ludgeri, was recently isolated and sequenced from a limestone art piece of the Old Cathedral. The study was a collaboration by scientists from the University of Coimbra and the Instituto Pedro Nunes. We spoke to first author João Trovão about the A. ludgeri resource and how it may be used by the scientific and conservator community.
What is Aeminium ludgeri?
Trovão: Aeminium ludgeri is an extremotolerant microcolonial black fungus belonging to the order Capnodiales. The organism was recently described, along with a new genus and family, in order to correctly accommodate this strain. The fungus was found colonizing a biodeteriorated limestone art-piece in the Old Cathedral of Coimbra, Portugal (UNESCO World Heritage Site) contributing to the overall deterioration of this piece.
What is biodegradation and what role does A. ludgeri play in biodegradation?
Trovão: Biodegradation can be defined as the set of processes naturally occurring that contribute to the decay and recycling of organic matter by microorganisms. However, when these material breakdown processes occur in man-made materials (including invaluable cultural heritage monuments) they are usually defined as biodeterioration. Being a microcolonial black fungus, Aeminium ludgeri likely contributes to the biodeterioration of stone monuments through hyphal penetration (biopitting), production of corrosive extracellular polysaccharides and through aesthetic alterations due to their usual strong dark colors.
Under what conditions was A. ludgeri DSM 106916 isolated and how was it cultured?
Trovão: During an experimental survey aimed to isolate fungi from biodeteriorated limestones in the Old Cathedral of Coimbra, we verified that this particular art-piece displayed signs typically associated with the presence of microcolonial black fungi. In order to isolate the fungal organisms possibly contributing to this phenomenon, we attempted to growth these organisms after plating samples of the dark areas of the art-piece in Malt Extract Agar supplemented with NaCl (10%). The organism was also isolated after plating on solid Halobacteria medium (NaCl 20%, pH 8) of an aliquot of a 7 days enrichment culture obtained in the same liquid medium. Colonies were further isolated into axenic cultures and kept using both these and additional culture media.
What might its genome reveal about A. ludgeri extremotolerance or biodegradation?
Trovão: We believe that the genome sequence of Aeminium ludgeri will provide valuable data regarding the extremotolerance pathways of microcolonial black fungi while also helping to further understand their contribution to biodeterioration of stone monuments. This data is allowing us, for example, to understand and acknowledge the protective molecules of this fungus (such as synthesis of melanin-like pigments), and consequently to ascertain what possible conservation approaches will likely provide better results in the future.
How will you use the A. ludgeri genome sequence in your research?
Trovão: We are currently conducting further laboratory tests in order to fully characterize the limestone biodeterioration spectrum and mechanisms of this organism. The genome sequence obtained in this study will ultimately contribute to further understand and link the biodeterioration and resistance mechanisms verified, with the metabolic pathways and genetic characteristics of this organism.
How will this resource help other scientists with their research?
Trovão: Our team is composed of biologists, geologists and physicists working to fully characterize limestone biodeterioration in this UNESCO World Heritage site. In that sense, our main goal is to provide valuable information that ultimately will help other scientists, restorers and conservators to adopt the most accurate intervention procedures for preserving and maintaining this cultural heritage monument for future generations. Nonetheless, we also believe that this information will also be helpful to mycologists working with this remarkable and diverse fungal group.