Diversity, heavy metals, and antibiotic resistance in culturable heterotrophic bacteria isolated from former lead-silver-zinc mine heap in Tarnowskie Gory (Silesia, Poland).

Mine tailings represent a great environmental concern due to their high contents of heavy metals. Cultivation analysis of microbiota of Tarnowskie Góry (Poland) mine tailing showed the occurrence of bacteria with colony-forming units as low as 5.7 × 104 per one gram of dried substrate. Among 110 bacterial isolates identified by a combination of MALDI-TOF mass spectrometry and 16S rRNA gene sequencing, phylum Actinobacteria was dominant, followed by Firmicutes and Proteobacteria. Extremely high levels of heavy-metal resistance were observed in Arthrobacter spp., particularly for zinc (500 mg/L), lead (1500 mg/L), and cadmium (1000 mg/L). On the other hand, Staphylococcus spp. showed high tolerance to several antibiotics tested, especially ampicillin, partly due to blaZ gene presence. Due to the occurrence of antibiotic-resistant bacteria, mine tailings are not the cause of heavy-metal contamination only, but also a source of antibiotic-resistant bacteria and thus may represent a serious risk for public health.

A COST Action on microbial responses to low pH: Developing links and sharing resources across the academic-industrial divide.

We present work of our COST Action on "Understanding and exploiting the impacts of low pH on micro-organisms". First, we summarise a workshop held at the European Federation of Biotechnology meeting on Microbial Stress Responses (online in 2020) on "Industrial applications of low pH stress on microbial bio-based production", as an example of an initiative fostering links between pure and applied research. We report the outcomes of a small survey on the challenging topic of developing links between researchers working in academia and industry that show that, while people in different sectors strongly support such links, barriers remain that obstruct this process. We present the thoughts of an expert panel held as part of the workshop above, where people with experience of collaboration between academia and industry shared ideas on how to develop and maintain links. Access to relevant information is essential for research in all sectors, and because of this we have developed, as part of our COST Action goals, two resources for the free use of all researchers with interests in any aspects of microbial responses to low pH. These are (1) a comprehensive database of references in the literature on different aspects of acid stress responses in different bacterial and fungal species, and (2) a database of research expertise across our network. We invite the community of researchers working in this field to take advantage of these resources to identify relevant literature and opportunities for establishing collaborations.

High frequency of antibiotic tolerance in deep subsurface heterotrophic cultivable bacteria from the Rozália Gold Mine, Slovakia.

The Rozália Mine, with its long mining history, could represent an environmental threat connected with metal contamination and associated antibiotic tolerance. Metal and antibiotic tolerance profiles of heterotrophic, cultivable bacteria isolated from the Rozália Gold Mine in Hodrusa-Hámre, Slovakia, and the surrounding area were analysed. Subsurface samples were collected from different mine levels or an ore storage dump. As expected, heterotrophic cultivable bacteria showed high minimum inhibitory concentrations for metals (up to 1000 mg/l for zinc and nickel, 2000 mg/l for lead and 500 mg/l for copper). Surprisingly, very high minimum inhibitory concentrations of selected antibiotics were observed, e.g. > 10,000 µg/ml for ampicillin, up to 4800 µg/ml for kanamycin, 800 µg/ml for chloramphenicol and 50 µg/ml for tetracycline. Correlation analysis revealed a linkage between increased tolerance to the antibiotics ampicillin and chloramphenicol and metal tolerance to nickel and copper. A correlation was also observed between tetracycline-kanamycin tolerance and zinc-lead tolerance. Our data indicate that high levels of antibiotic tolerance occur in deep subsurface microbiota, which is probably connected with the increased level of metal concentrations in the mine environment.

Analysis of the bacterial community from high alkaline (pH > 13) drainage water at a brown mud disposal site near Ziar nad Hronom (Banská Bystrica region, Slovakia) using 454 pyrosequencing.

Brown mud, as a waste product of the industrial process of aluminum production, represents a great environmental burden due to its toxicity to living organisms. However, some microorganisms are able to survive in this habitat, and they can be used in bioremediation processes. Traditional cultivation methods have a limited capacity to characterize bacterial composition in environmental samples. Recently, next-generation sequencing methods have provided new perspectives on microbial community studies. The aim of this study was to analyze the bacterial community in the drainage water of brown mud disposal site near Ziar nad Hronom (Banská Bystrica region, Slovakia) using 454 pyrosequencing. We obtained 9964 sequences assigned to 163 operational taxonomic units belonging to 10 bacterial phyla. The phylum Proteobacteria showed the highest abundance (80.39%) within the bacterial community, followed by Firmicutes (13.05%) and Bacteroidetes (5.64%). Other bacterial phyla showed an abundance lower than 1%. The classification yielded 85 genera. Sulfurospirillum spp. (45.19%) dominated the bacterial population, followed by Pseudomonas spp. (13.76%) and Exiguobacterium spp. (13.02%). These results indicate that high heavy metals content, high pH, and lack of essential nutrients are the drivers of a dramatic reduction of diversity in the bacterial population in this environment.