Invitation to the Defense of Johannes Tichy

The Examination Panel is made up of: Dipl. Ing. Dr.techn. Dubravka Jembrih Simbürger (chair), Univ. Prof. Dipl. Biol. Dr. Katja Sterflinger (supervisor), Dr. Domenico Pangallo, DrSc. (external appraiser).

The defense will take place in English at the INTK at Kelsenstraße 2, 1030 Vienna, EG, Raum 0.10, Seminarraum 2

Abstract

Abstract The conservation of our built cultural heritage, increasingly threatened by climate change, is becoming an ever-greater challenge for the active protection of art and cultural heritage in the 21st century. Common physical and chemical ageing processes that affect built cultural heritage and monuments are being accelerated by ongoing climate change. One of the key factors driving the predictable deterioration associated with climatic changes is salt weathering, caused by the increased frequency of salt dissolution-crystallisation cycles, which play a significant role in surface degradation. Salts pose a constant threat to cultural monuments and to the surfaces and structures of historic buildings through damage mechanisms, such as mechanical and physico-chemical decay and related decomposition processes. Salt damage not only accelerates the weathering of the building material itself, but also creates an ecological niche that can be colonised by halotolerant and halophilic microorganisms. In addition to colonising the surfaces of affected structures in the form of biofilms, pink discolouration may occur due to the production of biological pigments, which can alter the aesthetic appearance significantly. Two representative historic buildings were selected to investigate the weathering salts and the structure and function of the colonising microorganisms on their surfaces: the St. Virgil Chapel on Stephansplatz in Vienna and the Carthusian monastery in Mauerbach, Lower Austria. Furthermore, the two buildings were used as test objects to develop damage mitigation strategies. Physico-chemical analysis methods were employed to identify and quantify the harmful salts present. Raman spectroscopy was used to investigate the pigment responsible for the pink discolouration. Third-generation sequencing technology was used for DNA-based analysis to determine the structure of the microbial community within the formed biofilm. RNA-based sequencing techniques were applied to elucidate the microbial activity, which was primarily driven by archaea and bacteria. Finally, the salt-damaged surfaces were treated with a desalination method involving the application of clay containing poultices for one year. Salt analysis revealed fundamental differences: the St. Virgil Chapel was damaged by chloride containing salts, whereas the Charterhouse Mauerbach was damaged by sulphate-containing salts. Spectroscopic analysis showed that the pigment responsible for the pink discolouration belongs to the carotenoid derivative class. The structure of the microbial community showed a strong dependency on the anions present in the respective salts (chloride vs. sulphate). Active metabolic pathways in the bacteria and archaea were elucidated using complex RNA extraction and sequencing analysis techniques, revealing a repertoire that enables them to survive in a salt-rich habitat. The spectroscopically identified pigments could also be partially verified through RNA analysis, which demonstrated evidence for the production of more than one pink pigment. Finally, the results of the developed desalination strategy, which included one year of microbial monitoring, showed that the microbial community reacted sensitively to changes in salt type and concentration. This highlights the need for a combined approach involving biological and salt-related monitoring during and after desalination treatments.

Short biography

• Food Science and Biotechnology, Bachelor, University of Natural Resources and Life Sciences/VIENNA, 2013-2016
• Biotechnology, Master, University of Natural Resources and Life Sciences/VIENNA, diploma-engineer, 2017-2020
• Material sciences, Doctoral study, Academy of Fine Arts Vienna, 2021-