## 3 Results and Discussion
### Bacterial Communities  
Bacteria have high importance in industrial processes, bioremediation, and heavy metal tolerance [13]. Bioremediation is the process of biological systems cleaning of the polluted environment by the bacteria and fungi, which are important for reclamation, immobilization and detoxification of heavy metals [63]. A total of 30 species of bacteria were detected from five samples of orchids, belonging to eight phyla, Acidobacteria, Actinobacteria, Bacteroidetes, Gemmatimonadetes, Placentomyces, Proteobacteria, Verrucomicobia, and Tenericutes (Table 2). The highest biodiversity of bacteria was in the roots and also surrounding soil of E. atrorubens (Jasenie). Additionally, the evenness in sampled pairs was consistently higher in soil samples (median 1.2x higher of Faith's phylogenetic diversity). However, that was not the cause in the number of discovered species as it was in analysis of fungal communities. Figure 3: Fungal communities detected in the surrounding soil of orchids. (1) _E. atrorubens_ (Dobsiná); (2) _E. atrorubens_ ([PERSON]); (3) _P. biifolia_ ([PERSON]); (4) _E. pontica_ ([PERSON]); (5) _C. longifolia_ ([PERSON]). Our results show (Figures 4 and 5) that _Candidatus Udaebacter_ was the dominant bacterium at the Sirk deposit in the roots of two different orchids as well as in technogenic substrate and a high dominance of bacteria from the family _Pyrinomonadaeae_ in a stony substrate on the mining heap in Dobsina and the related very dominant abundance of the fungus _Trichorphaea pseudogregaria_ in the roots of _E. atrorubens_. The most abundant species in the roots of orchids was _Candidatus udaeobacter_, _Gemmata_ sp., _Singulisphaera_ sp., _Chtthonobacter_ sp., _Pseudomonas_ sp., _Luteolibacter_ sp., _Nocardioides_ sp., _Pirellula_ sp. (Figure 4). In the surrounding soil, it was _Candidatus udaeobacter_, _Chtthonobacter_ sp., _Pyrinomonadaceae_; _RB41_, _Gemmata_ sp., and _Pirellula_ sp. (Figure 5). Moreover, _Candidatus udaeobacter_, _Candidatus solibacter_, and _Chtthonobacter_ sp. were present in four or more soil samples. Furthermore, 11 species tolerated pH of 4.98. **Faith’s phylogenetic diversity** & **21.2** & **25.4** & **23.5** & **26.8** & **19.3** & **41.7** & **16.8** & **19.9** & **17.3** & **26.2** \\ \hline \hline \end{tabular}
\end{table}
Table 2: DNA identification of the bacteria isolated from the roots of the orchids and surrounding soils. Species, such as Candidatus solibacter, _Bradyrhizobium_ sp., _Burkholderia_ sp., _Gemmatomonas_ sp., _Fimbriglobus_ sp., _Flatobacterium_ sp., _Pseudomonas_ sp., _Spithgomonas_ sp., _Pedobacter_ sp., and _Verrucomicrobia_ sp. were also detected in heavy metal contaminated soils [64, 65, 66, 67, 68]. A bacterium with the highest relative abundance was Candidatus udaeobacter, which is an abundant soil bacterium that reduces its requirement for soil organic carbon by acquiring costly amino acids and vitamins from the environment [69]. Pirellula sp. found in both roots and soil gains energy from the aerobic oxidation of mono- or disaccharides derived from the cleavage of sulfated polymers produced by algae [70]. Bacteria from the genus _Pseudomonas_ induce auxin production by plant growth-promoting bacteria [71]. They are also known as very metabolically active bacteria able to utilize many agrochemicals [72, 73, 74]. Together with _Luteolibacter_ sp., _Vicinamibacter_ sp., and _Sphingomonas_ sp. they were identified by many other studies as an oil-degrading bacteria which is important for bioremediation [75, 76, 77]. _Acidibacter_ sp. and _Candidatus solibacter_ were suitable to be grown in oil-contaminated soils [78]. The genera representing the heterotrophic strain _Planctomycetes_ have the ability to reduce sulfur and, in particular, play an important role in sugar metabolism [79]. The overlap of the genera present indicates a close connection of the plant with the microbiome, therefore the plant is able to adapt quickly to changing conditions.