Abstract
BackgroundAn exceptionally thick biofilm covers walls of ancient gold and arsenic Złoty Stok mine (Poland) in the apparent absence of organic sources of energy.Methods and ResultsWe have characterized this microbial community using culture-dependent and independent methods. We sequenced amplicons of the 16S rRNA gene obtained using generic primers and additional primers targeted at Archaea and Actinobacteria separately. Also, we have cultured numerous isolates from the biofilm on different media under aerobic and anaerobic conditions. We discovered very high biodiversity, and no single taxonomic group was dominant. The majority of almost 4,000 OTUs were classified above genus level indicating presence of novel species. Elemental analysis, performed using SEM-EDS and X-ray, of biofilm samples showed that carbon, sulphur and oxygen were not evenly distributed in the biofilm and that their presence is highly correlated. However, the distribution of arsenic and iron was more flat, and numerous intrusions of elemental silver and platinum were noted, indicating that microorganisms play a key role in releasing these elements from the rock.ConclusionsAltogether, the picture obtained throughout this study shows a very rich, complex and interdependent system of rock biofilm. The chemical heterogeneity of biofilm is a likely explanation as to why this oligotrophic environment is capable of supporting such high microbial diversity.
Highlights
The mutual interactions of microbes with surroundings result in both environmental and microbial community changes
The overall morphological appearance of the biofilm is variable in terms of colour, smoothness, consistency, moisture content, thickness and tubercle dimensions, yet the internal structure revealed by Scanning Electron Microscopy (SEM) methodology shown in every case the lattice structure of the matrix with vast empty or lower electron density spaces (Figs. 1D and 1E)
Certain habitats support high biodiversity despite limited resources, and this situation is called ‘‘the paradox of the plankton’’ (Hutchinson, 1961), as plankton was the first example of this kind of environment
Summary
The mutual interactions of microbes with surroundings result in both environmental and microbial community changes. The structure of microbial communities in a particular environment depends on specific physical and chemical conditions: humidity, pH, How to cite this article Tomczyk-Żak et al (2017), Taxonomic and chemical assessment of exceptionally abundant rock mine biofilm. Only sporadic development of microorganisms on the surfaces in the form of abundant biofilms has been documented. In most cases these were the micro-colonies on prehistorical paintings in caves (SchabereiterGurtner et al, 2002a; Portillo, Gonzalez & Saiz-Jimenez, 2008; Portillo, Gonzalez & SaizJimenez, 2009; Schabereiter-Gurtner et al, 2002b; Schabereiter-Gurtner et al, 2004) or populations colonizing historical monuments (Gorbushina et al, 2002; Zimmermann, Gonzalez & Saiz-Jimenez, 2006). The chemical heterogeneity of biofilm is a likely explanation as to why this oligotrophic environment is capable of supporting such high microbial diversity
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