# A Snapshot of the Microbiome of a Portuguese Abandoned Gold Mining Area
## 3 Results and Discussion
### Microbiome Diversity and Community Structural Organization
Lastly, when considering the diversity at the genus level, a WD2101 soil group genus (8%), _Sphingomonas_ (6%) and Candidatus _Solibacter_ (4%) were dominant in the control sample; _Bryobacter_ (10%), a WD2101 soil group genus (6%) and a WPS-2 genus (6%) were dominant in the tailings sample; and _Crossiella_ (8%), uncultured _Gemmataceae_ (6%), _Acidobacteriaceae_ (Subgroup 1) (4%) genera and _Acidophilium_ (4%) were dominant in the mine interior. _Proteobacteria_, _Acidobacteria_ and _Actinobacteria_ are often regarded as the dominant taxa colonizing mine tailings, a consequence of low environmental pH, poor organic matter contents and high concentrations of elements such as Pb, Cd and Zn [35]. As such, our results corroborate and are in accordance with the currently available literature [35; 78; 79]. Moreover, it was also possible to detect a change in dominance from _Proteobacteria_ to _Acidobacteria_ during the transition from the control towards the tailings and the mine areas, likely mirroring the alterations in soil pH and ion concentrations. _Acidobacteria_ were also found to be dominant in soils of Linglong Gold Mine (China) [24] and have been reported as the main prokaryotes in several distinctive acidic environments [80]. As for the additional genera, the WD2101 soil group and _Genmataaceae_ genus have been previously  
Figure 4: Fungi relative abundance (Top 10) at the Family level. Figure 3: Bacteria relative abundance (Top10) at the Family level. reported in various terrestrial habitats [33; 81], while _Sphingomonas_, Candidatus _Solibacter_, _Bryobacter_ and _Acidiplilium_ have frequently been described as present in gold mining ones and tailings [24; 34; 35]. Additionally, _Crossiella_ has also been recently pinpointed as an _Actinomycetota_ genus commonly found in the environment, including in various mineral mining soils [82]. On the other hand, for fungi, at the Phylum level, the control sample was largely dominated by _Ascomycata_ (69%), unclassified _Fungi_ (13%) and _Basidiomycata_ (9%); the tailings were largely dominated by _Ascomycata_ (95%); and lastly, the mine was largely dominated by _Ascomycata_ (56%), _Mortierellomycata_ (18%) and unclassified _Fungi_ (16%). Additionally, it could also be verified that unclassified _Heliotales_ (19%), _Chaetomiaceae_ (12%), unclassified _Fungi_ (13%), unclassified _Letoimycetes_ (5%) and _A Aspergillus_ (5%) are the predominant family level fungal groups in the control samples; _Saccharomyces_ fam. _Incertae sedis_ (34%), unclassified _Heliotales_ (17%), _Dermateaceae_ (16%), unclassified _Campoidales_ (13%) and _Metschinkwiaceae_ (5%) are predominant in the tailings; and that unclassified _Chaetomistries_ (21%), _Mortierellaceae_ (18%), unclassified _Fungi_ (16%), _Apergillusaceae_ (8%) and _Rhizopogonaceae_ (4%) are predominant in the mine sample. Finally, when considering the diversity at the genus level, unclassified _Heliotales_ (19%), unclassified _Fungi_ (13%) and _Arxotrichum_ (12%) were dominant in the control samples; _Starmerella_ (34%), unclassified _Heliotales_ (17%) and _Mollisia_ (16%) were dominant in the tailings; and _Mortierella_ (18%), unclassified _Fungi_ (16%) and _Chaetothriviales_ (21%) genera were dominant in the mine. These results also point to a change in dominance for fungal phyla across samples, namely a strong decrease from _Basidiomycata_ from the control towards the tailings and the mine. Moreover, an interesting and sharp increase of _Mortierellomycata_ inside the mine was also registered. The dominance of _Mortierellomycata_ (marked as _Zygomycata_) has been previously identified in highly contaminated gold mining sites, likely due to their ability to withstand significant arsenic concentrations [29].