Taxonomically-linked growth phenotypes during arsenic stress among arsenic resistant bacteria isolated from soils overlying the Centralia coal seam fire

• Published in: PloS one 2018-01, Vol.13 (1), p.e0191893
• Main Authors: Dunivin, Taylor K, Miller, Justine, Shade, Ashley
• Format: Article
• Language: English
• Subjects: Arsenate reductase; Arsenates; Arsenic; Arsenic - pharmacokinetics; Arsenic - toxicity; Arsenite; Bacteria; Bacteria, Aerobic - classification; Bacteria, Aerobic - drug effects; Bacteria, Aerobic - genetics; Biodegradation, Environmental; Biology and life sciences; Biosphere; Biotransformation; Burning; Coal; Collections; Computer and Information Sciences; Deoxyribonucleic acid; DNA; Drug Resistance, Bacterial - genetics; Ecology; Ecology and Environmental Sciences; Efflux; Engineering and Technology; Environmental management; Environmental protection; Exposure; Fires; Gene transfer; Gene Transfer, Horizontal; Genera; Genes; Genes, Bacterial; Genetic transformation; Genomes; Glycerol; Growth rate; Horizontal transfer; Lag time; Medicine and Health Sciences; Microorganisms; Morphology; Pennsylvania; Phenotypes; Phylogeny; Physical Sciences; Reductases; Research and Analysis Methods; rRNA 16S; Soil bacteria; Soil Microbiology; Soil microorganisms; Soil Pollutants - pharmacokinetics; Soil Pollutants - toxicity; Soils; Stress, Physiological; Taxonomy
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0191893

Arsenic (As), a toxic element, has impacted life since early Earth. Thus, microorganisms have evolved many As resistance and tolerance mechanisms to improve their survival outcomes given As exposure. We isolated As resistant bacteria from Centralia, PA, the site of an underground coal seam fire that has been burning since 1962. From a 57.4°C soil collected from a vent above the fire, we isolated 25 unique aerobic As resistant bacterial strains spanning seven genera. We examined their diversity, resistance gene content, transformation abilities, inhibitory concentrations, and growth phenotypes. Although As concentrations were low at the time of soil collection (2.58 ppm), isolates had high minimum inhibitory concentrations (MICs) of arsenate and arsenite (>300 mM and 20 mM respectively), and most isolates were capable of arsenate reduction. We screened isolates (PCR and sequencing) using 12 published primer sets for six As resistance genes (AsRGs). Genes encoding arsenate reductase (arsC) and arsenite efflux pumps (arsB, ACR3(2)) were present, and phylogenetic incongruence between 16S rRNA genes and AsRGs provided evidence for horizontal gene transfer. A detailed investigation of differences in isolate growth phenotypes across As concentrations (lag time to exponential growth, maximum growth rate, and maximum OD590) showed a relationship with taxonomy, providing information that could help to predict an isolate's performance given As exposure in situ. Our results suggest that microbiological management and remediation of environmental As could be informed by taxonomically-linked As tolerance, potential for resistance gene transferability, and the rare biosphere.