## 3 Results
### Seasonal Changes of Microbial Biodiversity
#### 3.3.2 Seasonal Biodiversity of Bacterial and Fungal Communities  
Dominating bacterial families (Figure 7a) identified in both seasons in stable bio-cenoses in sites 5 and 8 (according to alpha diversity analysis) belonged to: Hymenopteraaceae (both sites), Sphingomonadaceae (both sites), Geodermatiphilaceae (site 8), Microbacteriaceae (site 8), Nocardioidaceae (site 8), Rhizaceae (site 5), Sphingobacteriaceae (site 8) and Trueperaceae (site 5). Figure 7: Seasonal biodiversity based on bacterial and fungal family composition. Two stacked-bar plots show percentage composition of bacterial (**a**) and fungal (**b**) families identified across samples in summer and winter. Taxonomy was assigned using Naive Bayes classifier (QIIME 2 package) with Silva 132 database and UNITE v7.2 reference datasets. The total number of 33 bacterial and 9 fungal families constituted more than 3% in overall compositions. Two additional and artificial groups were created to include the families with abundance lower than the threshold (_Other_ below 3%) and the ones with unspecified (i.e., _’f_ —) or uncertain (i.e., _’Incertaine_ sedis’_) taxonomic position assigned (_Unspecified_). Biocenosis in site 6 was strictly dominated in both seasons by Acetobacteraceae and Acidobacteriaceae while in site 2, in addition to these two families, also Sphingobacteriaceae and Sphingomonadaceae were presented in both seasons with high abundance. In site no 1, bacterial sequences that presented with high abundance in both seasons belonged to Acetobacteraceae, Blastocatellaceae, Chitinophagaceae, Micromonosporaceae, Sphingomonadaceae, and Tepidosphaeraceae families, while in site no 3 the following families dominated in both seasons: Blastocatellaceae, Chitinophagaceae, Hymenopteraaceae, Nestocaceae, Pseudonocardiacae, and Sphingomonadaceae. In the last two sites, i.e., 4 and 7, there were only three and four families identified in both seasons respectively. These were Sphingomonadaceae, Tepidosphaeraceae and Truperaceae in site 4 and Flavobacteriaceae, Rhizobiaceae, Sphingobacteriaceae and Sphingomonadaceae in site 7. In analyzed biocenoses we also identified families that were dominated in samples collected only in winter or summer. To \"summer-specific\" bacterial families belonged: Beijerinckiaceae (sites 1-3 and 5), Caulobacteraceae (sites 4 and 7), Isosphaeraceae (sites 1 and 4), Kineosporiaceae (site 4), Rhodobacteraceae (sites 3-5), Solibacteraceae (site 6) and Spirosomaceae (sites 1, 3, and 8). The analysis of diversity at the family level showed that there are more families specific to winter. These \"winter-specific\" families on Pergola's surfaces were: Burkholderiaceae (sites 3, 6 and 8), Clostrtidaeene 1 (site 3), Cryomorphaceae (site 7), Cyclobacteriaceae (site 7), Cytophagaceae (site 3), Halomonadaceae (site 7), Marinobacteraceae (site 7), Micrococcaceae (site 5), and Microscillaceae (site 3). In sites 1 and 7, there were no fungal families identified in both seasons (Figure 7b). The Herpotrichilecae family was identified in sites from 2 to 4 in both seasons, Ramalinaceae dominated in winter and summer in sites 4, 5, and 8. Parmeliaceae family was identified in both seasons only in site 6, Bulleribasidiaceae in site 8, Teratosphaeriaceae in site 5 while Trichomeriaceae in site 3. Nectriaceae and Physciaceae families were identified with high abundance only in samples collected in summer (from sites 7 and 5 respectively), while Stereocoalaceae only in sample collected in winter (site 4). Moreover, a positive correlation between the presence of lichen crusts on the sandstone surface and the presence of _Rhinocladiella_ spp. and _Lecania_ spp. fungi, bacterial genus _Trupera_ spp., as well as bacteria from Nocardioidaceae family were found. For Acidobacteriaceae and Acetobacteraceae families and the presence of lichen crusts, a negative correlation was observed. A positive correlation between the presence of masses and the number of sequences of _Methylobacterium_ spp.