Microbial community shifts during salt mitigation treatments of historic buildings using mineral poultices: a long-term monitoring of salt and associated biofilms

Increased heavy rainfall followed by periods of drought due to climate change is leading to more frequent salt-crystallization cycles. This not only leads to increased salt-weathering on architectural surfaces of cultural heritage monuments, but also creates an ideal ecological niche for the formati...

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Main Authors: Johannes Tichy, Beate Sipek, Martin Ortbauer, Lukas Fürnwein, Monika Waldherr, Alexandra Graf, Katja Sterflinger, Guadalupe Piñar
Format: Article
Language:English
Published: Frontiers Media S.A. 2025-05-01
Series:Frontiers in Microbiology
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Online Access:https://www.frontiersin.org/articles/10.3389/fmicb.2025.1603289/full
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author Johannes Tichy
Beate Sipek
Martin Ortbauer
Lukas Fürnwein
Monika Waldherr
Alexandra Graf
Katja Sterflinger
Guadalupe Piñar
author_facet Johannes Tichy
Beate Sipek
Martin Ortbauer
Lukas Fürnwein
Monika Waldherr
Alexandra Graf
Katja Sterflinger
Guadalupe Piñar
author_sort Johannes Tichy
collection DOAJ
description Increased heavy rainfall followed by periods of drought due to climate change is leading to more frequent salt-crystallization cycles. This not only leads to increased salt-weathering on architectural surfaces of cultural heritage monuments, but also creates an ideal ecological niche for the formation of biofilms by salt-loving microorganisms. These biofilms, characterized by a distinctive pink coloration, cause additional esthetic alterations to affected surfaces. In this study, mineral poultices prepared with different clay minerals (sepiolite, kaolinite and vermiculite) were developed and tested for a long-term (1 year) application on salt-weathered surfaces, thus contributing to their preservation. The poultices were tested on the surfaces of two historic buildings: the St. Virgil’s Chapel in Vienna and the Mauerbach Charterhouse in Lower Austria, both showing salt efflorescence and a uniform pink biofilm. First, the poultices were tested to evaluate their salt retention capacity, salt-weathering resistance and processability. The retention properties of the poultices were examined by measuring their salt content throughout the treatment using high performance liquid chromatography (HPLC) and continuous flow analysis (CFA). Salt content was also measured on the wall surfaces before and after treatment. Second, the effect of the desalination treatments on salt-associated pink biofilms was also evaluated. The shifts within the biofilm communities during and after the treatment were monitored by qPCR and long-read archaeal- and bacterial-16S rRNA amplicon analysis using the Nanopore sequencing technology. The results demonstrate that both the selected clay minerals and the salt composition in the treated areas significantly influenced the salt storage capacity of the poultices and their resistance to salt weathering. Fluctuations in salt load and ionic composition during and after treatment affected biofilm composition, with bacterial communities proving more sensitive than archaea to these changes. Both qPCR and metataxonomic results show that the effects of the poultices on the colonizing biofilms depend not only on the composition of their microbial members, but also on external abiotic factors such as the chemical composition and concentration of the salt mixtures on the surfaces. In addition, the biodiversity within the biofilms shows to be affected differently depending on the mineral clay used.
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publisher Frontiers Media S.A.
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series Frontiers in Microbiology
spelling doaj-art-69232cdf85054ea1b9499580e7e2731d2025-08-20T03:47:34ZengFrontiers Media S.A.Frontiers in Microbiology1664-302X2025-05-011610.3389/fmicb.2025.16032891603289Microbial community shifts during salt mitigation treatments of historic buildings using mineral poultices: a long-term monitoring of salt and associated biofilmsJohannes Tichy0Beate Sipek1Martin Ortbauer2Lukas Fürnwein3Monika Waldherr4Alexandra Graf5Katja Sterflinger6Guadalupe Piñar7Institute for Natural Sciences and Technology in the Art, Academy of Fine Arts Vienna, Vienna, AustriaInstitute for Conservation – Restoration, Academy of Fine Arts Vienna, Vienna, AustriaInstitute for Conservation – Restoration, Academy of Fine Arts Vienna, Vienna, AustriaDepartment of Applied Life Sciences/Bioengineering/Bioinformatics, FH Campus Wien, Vienna, AustriaDepartment of Applied Life Sciences/Bioengineering/Bioinformatics, FH Campus Wien, Vienna, AustriaDepartment of Applied Life Sciences/Bioengineering/Bioinformatics, FH Campus Wien, Vienna, AustriaInstitute for Natural Sciences and Technology in the Art, Academy of Fine Arts Vienna, Vienna, AustriaInstitute for Natural Sciences and Technology in the Art, Academy of Fine Arts Vienna, Vienna, AustriaIncreased heavy rainfall followed by periods of drought due to climate change is leading to more frequent salt-crystallization cycles. This not only leads to increased salt-weathering on architectural surfaces of cultural heritage monuments, but also creates an ideal ecological niche for the formation of biofilms by salt-loving microorganisms. These biofilms, characterized by a distinctive pink coloration, cause additional esthetic alterations to affected surfaces. In this study, mineral poultices prepared with different clay minerals (sepiolite, kaolinite and vermiculite) were developed and tested for a long-term (1 year) application on salt-weathered surfaces, thus contributing to their preservation. The poultices were tested on the surfaces of two historic buildings: the St. Virgil’s Chapel in Vienna and the Mauerbach Charterhouse in Lower Austria, both showing salt efflorescence and a uniform pink biofilm. First, the poultices were tested to evaluate their salt retention capacity, salt-weathering resistance and processability. The retention properties of the poultices were examined by measuring their salt content throughout the treatment using high performance liquid chromatography (HPLC) and continuous flow analysis (CFA). Salt content was also measured on the wall surfaces before and after treatment. Second, the effect of the desalination treatments on salt-associated pink biofilms was also evaluated. The shifts within the biofilm communities during and after the treatment were monitored by qPCR and long-read archaeal- and bacterial-16S rRNA amplicon analysis using the Nanopore sequencing technology. The results demonstrate that both the selected clay minerals and the salt composition in the treated areas significantly influenced the salt storage capacity of the poultices and their resistance to salt weathering. Fluctuations in salt load and ionic composition during and after treatment affected biofilm composition, with bacterial communities proving more sensitive than archaea to these changes. Both qPCR and metataxonomic results show that the effects of the poultices on the colonizing biofilms depend not only on the composition of their microbial members, but also on external abiotic factors such as the chemical composition and concentration of the salt mixtures on the surfaces. In addition, the biodiversity within the biofilms shows to be affected differently depending on the mineral clay used.https://www.frontiersin.org/articles/10.3389/fmicb.2025.1603289/fullsalt-weatheringmineral poulticespink biofilmsarchaeabacterialong-term monitoring
spellingShingle Johannes Tichy
Beate Sipek
Martin Ortbauer
Lukas Fürnwein
Monika Waldherr
Alexandra Graf
Katja Sterflinger
Guadalupe Piñar
Microbial community shifts during salt mitigation treatments of historic buildings using mineral poultices: a long-term monitoring of salt and associated biofilms
Frontiers in Microbiology
salt-weathering
mineral poultices
pink biofilms
archaea
bacteria
long-term monitoring
title Microbial community shifts during salt mitigation treatments of historic buildings using mineral poultices: a long-term monitoring of salt and associated biofilms
title_full Microbial community shifts during salt mitigation treatments of historic buildings using mineral poultices: a long-term monitoring of salt and associated biofilms
title_fullStr Microbial community shifts during salt mitigation treatments of historic buildings using mineral poultices: a long-term monitoring of salt and associated biofilms
title_full_unstemmed Microbial community shifts during salt mitigation treatments of historic buildings using mineral poultices: a long-term monitoring of salt and associated biofilms
title_short Microbial community shifts during salt mitigation treatments of historic buildings using mineral poultices: a long-term monitoring of salt and associated biofilms
title_sort microbial community shifts during salt mitigation treatments of historic buildings using mineral poultices a long term monitoring of salt and associated biofilms
topic salt-weathering
mineral poultices
pink biofilms
archaea
bacteria
long-term monitoring
url https://www.frontiersin.org/articles/10.3389/fmicb.2025.1603289/full
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