###### Abstract  
The aim of the presented investigation was to describe seasonal changes of microbial community composition in situ in different biocenoses on historical sandstone of the Northern Pergola in the Museum of King John III's Palace at Wilanow (Poland). The microbial biodiversity was analyzed by the application of Illumina-based next-generation sequencing methods. The metabarocoding analysis allowed for detecting lichenized fungi taxa with the clear domination of two genera: _Lecamia_ and _Rhinolacidilla_. It was also observed that, during winter, the richness of fungal communities increased in the biocenoses dominated by lichens and mosses. The metabarocoding analysis showed 34 bacterial genera, with a clear domination of _Spingomonas_ spp. across almost all biocenoses. Acidophilic bacteria from Acidobacteriaceae and Acetobacteraceae families were also identified, and the results showed that a significant number of bacterial strains isolated during the summer displayed the ability to acidification in contrast to strains isolated in winter, when a large number of isolates displayed alkalizing activity. Other bacteria capable of nitrogen fixation and hydrocarbon utilization (including aromatic hydrocarbons) as well as halophilic microorganisms were also found. The diversity of organisms in the biofilm ensures its stability throughout the year despite the differences recorded between winter and summer. ultural heritage; biodeterioration; biodiversity of microorganisms; stone surfaces; historical sandstone; next-generation sequencing +
Footnote †: journal: Appl. Sci. 2021, 11, 620.  
undesirable degradative processes are called biodeterioration [10] and may affect valuable objects of cultural heritage [11]. Biodeterioration of stone surfaces mainly depends on their porosity, roughness, and mineral composition [12]. The porosity and roughness affect the rate of microbial colonization for physical reasons, while the mineral composition of stones determines the availability of nutrients for different groups of colonizing microorganisms. Generally, stones pioneering microorganisms mainly belong to chemolithotrophs, chemoorganotrophs, and phototrophs [13; 14] and their activity may lead to the chemical dissolution of the stone material by production and secretion of dissolution agents such as organic and inorganic acids and ligands [15]. Besides the above-listed abiotic factors affecting the presence and activity of various bacterial and fungal groups inhabiting the historical objects, the presence of more complex organisms, including lichens, mosses, and algae, is also important. These lithobiotic, epilithic and endolithic organisms are considered to be the main factors involved in the deterioration of historical stone objects [5; 16; 17; 18]. A wide variety of lichens, mosses and algae have been found on rocks, historical mural paintings, as well as stone monuments and buildings. However, bacteria and fungi still play a key role in the primary colonization and initial destruction of such facilities and objects [19; 20; 21; 22; 23]. Generally, data regarding the biodiversity and the biological activity of biofilms participating in stone deteriorating processes are scarce and incomplete. Molecular genetic analyses have been performed over the last ten years and they have proved to be valuable. Good examples are the biodiversity studies performed on biofilms occurring on different stone surfaces located inside and outside historical buildings, caves, and grottoes [7; 9; 23; 24]. Further studies were performed using next-generation sequencing analyses of whole microbial communities to establish microbial biodiversity in spatial structure (2D) of the lithobiotic biofilm on sandstone surfaces [9]. These analyses enhance our knowledge regarding the microbial diversity on historical stone surfaces.