## 4 Discussion
[47] observed high abundance of these phyla only in the samples of sandstone materials loosely on sandstone block from two Angkor temples. [PERSON] et al. [50] identified bacteria at the level of genera and, as in the case of Pergola, they noted the presence of _Hymenobacter, Methylobacterium Pseudonocardi, Rosceomonas, Scytonema, Spirosoma_, and _Trupera_ with abundances similar to those found in our study. Furthermore, the results of metagenomic analyses allowed for the identification of bacteria that have the ability to produce natural pigmented compounds. The genus _Sphingomonas_ identified with high abundance in almost all analyzed biocenoses and _Ralstonia_ genus are known for its properties to produce red pigments [35]. Moreover, in the analyzed biofilms there were numerous bacteria, especially during winter, from the genera _Arthobacter_ which produce blue and dark green pigments and _Cytohaga_ which produce yellow pigments. On the other hand, _Flavobacterium_ genus, which also produce yellow pigments [35] were identified with high abundance in summer. The above observations indicate that the main factor influencing the visible color changes of BPs depending on the seasons may be related with seasonal variation in the number of microorganisms capable of producing pigments. The fungal composition of all samples was dominated mainly by lichenized fungi (e.g., _Lecania_ spp., _Lepraria_ spp. ), while other taxa were also observed. Domination of Ascomycta is clearly visible and similar to the observations of [PERSON] et al. [9; 45] and [PERSON] et al. [50; 52]. Our data underlines the domination mostly by two genera: _Lecania_ and _Rhinocladiella_, presence of which was correlated with the presence of lichens on the sandstone surface. Many microbial taxa and eukaryotes that are lichen symbionts have also been identified on granite and limestone surfaces of tombstones in tropical, subtropical as well as more temperate regions [48]. Moreover, microbial biodiversity analysis indicates high abundance of acidifying bacteria taxa in biocenoses structures, i.e., Acetobacteraceae and Acidobacteriaceae. Duringsummer, ASVs of Acetobacteraceae family (producing acetic acid during fermentation) were most frequent compared to winter. High percentage of Acetobacteraceae in different biocenoses can affect the diversity of bacterial strains isolated on the Blickfeldt medium, and, in consequence, distinct acidifying properties were shown for summer isolates. Our data appears to correlate with the observation that different acidifying bacteria dominate the biofilm structures with seasonal dependence. The data quoted here refers only to cultured bacterial strains. Unfortunately, cultivation methods do not allow for the isolation of microorganisms in the proportions in which they are actually present in a given sample. Also in vitro studies of the activity of the culturable strains do not give us real insight into the actual metabolic changes that can be demonstrated by entire complex consortia of microorganisms in situ, in the environment. Therefore, in the next stage, we would like to verify which metabolic pathways dominate in a given season and which pathways are characteristic for given BPs using metabolomic analyses for sites with different BPs in dependent of seasons. Direct metabolic analyses of microorganisms colonizing the surfaces of historical sandstone would undoubtedly broaden the knowledge of geomicrobiology of building materials [53] in temperate climates, especially since sandstone is also a popular material nowadays. Such research would allow for the development of dedicated conservation schemes, e.g., for the selection of a biodeteriogens removal agent depending on the season or BPs. One of the possible explanation of differences in biochemical properties of isolated strains is that during seasons bacteria can change their metabolisms. These theses are consistent with the results of the metabolomic analysis of historical brick and wood samples activated by incubation in atmosphere with high humidity.