Celebrate Taylor's new pub!
We are pleased to celebrate Taylor Dunivin's first ShadeLab paper, published today in the journal PLoS One! Taylor is a ShadeLab PhD student in MMG and Environmental Toxicology.
Title:
Taxonomically-linked growth phenotypes during arsenic stress among arsenic resistant bacteria isolated from soils overlying the Centralia coal seam fire
Why we're jazzed about it:
Microbial arsenic resistance is ancient, and the genes conferring resistance can be disseminated among microbes via horizontal gene transfer. In this study, we dig into the nitty gritty of microbial growth in arsenic in an isolate collection to show that there can be varied responses that likely have ecological consequences for competition in arsenic. Our results suggest that how a microbe grows in arsenic may be predicted by its place on the phylogenetic tree (its taxonomy) and not necessarily by how the gene was acquired (either from the parent line or from a neighbor). More work is needed to investigate these patterns with additional types of bacteria.
Abstract:
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.