SREL Reprint #3432

Physiological and comparative genomic analysis of Arthrobacter sp. SRS-W-1-2016 provides insights on niche adaptation for survival in uraniferous soils

Ashvini Chauhan1, Ashish Pathak1, Rajneesh Jaswal1, Bobby Edwards III1, Demario Chappell2,
Christopher Ball3, Reyna Garcia-Sillas4, Paul Stothard5, and John Seaman6

1Environmental Biotechnology and Genomics Laboratory, School of the Environment,
1515 S. Martin Luther King Jr. Blvd., Suite 305B, FSH Science Research Center,
Florida A&M University, Tallahassee, FL 32307, USA
2Department of Biology, College of Science and Technology, 1610 S. Martin Luther King Blvd.,
Florida A&M University, Tallahassee, FL 32307, USA
3Department of Biological Sciences, Life Science Building, Alabama State University,
915 S Jackson Street, Montgomery, AL 36101, USA
4School of Life Sciences, College of Liberal Arts and Sciences, Arizona State University,
723 E 6th St, Tempe, AZ 85281, USA
5Department of Agricultural, Food and Nutritional Science, University of Alberta,
Edmonton, AB T6G 2P5, Canada
6Savannah River Ecology Laboratory, University of Georgia, Aiken, SC 29802, USA

Abstract: Arthrobacter sp. strain SRS-W-1-2016 was isolated on high concentrations of uranium (U) from the Savannah River Site (SRS) that remains co-contaminated by radionuclides, heavy metals, and organics. SRS is located on the northeast bank of the Savannah River (South Carolina, USA), which is a U.S. Department of Energy (DOE) managed ecosystem left historically contaminated from decades of nuclear weapons production activities. Predominant contaminants within the impacted SRS environment include U and Nickel (Ni), both of which can be transformed microbially into less toxic forms via metal complexation mechanisms. Strain SRS-W-1-2016 was isolated from the uraniferous SRS soils on high concentrations of U (4200 µM) and Ni (8500 µM), but rapid growth was observed at much lower concentrations of 500 µM U and 1000 µM Ni, respectively. Microcosm studies established with strain SRS-W-1-2016 revealed a rapid decline in the concentration of spiked U such that it was almost undetectable in the supernatant by 72 h of incubation. Conversely, Ni concentrations remained unchanged, suggesting that the strain removed U but not Ni under the tested conditions. To obtain a deeper understanding of the metabolic potential, a draft genome sequence of strain SRS-W-1-2016 was obtained at a coverage of 90x, assembling into 93 contigs with an N50 contig length of 92,788 bases. The genomic size of strain SRS-W-1-2016 was found to be 4,564,701 bases with a total number of 4327 putative genes. An in-depth, genome-wide comparison between strain SRS-W-1-2016 and its four closest taxonomic relatives revealed 1159 distinct genes, representing 26.7% of its total genome; many associating with metal resistance proteins (e.g., for cadmium, cobalt, and zinc), transporter proteins, stress proteins, cytochromes, and drug resistance functions. Additionally, several gene homologues coding for resistance to metals were identified in the strain, such as outer membrane efflux pump proteins, peptide/nickel transport substrate and ATP-binding proteins, a high-affinity nickel-transport protein, and the spoT gene, which was recently implicated in bacterial resistance towards U. Detailed genome mining analysis of strain SRS-W-1-2016 also revealed the presence of a plethora of secondary metabolite biosynthetic gene clusters likely facilitating resistance to antibiotics, biocides, and metals. Additionally, several gene homologous for the well-known oxygenase enzyme system were also identified, potentially functioning to generate energy via the breakdown of organic compounds and thus enabling the successful colonization and natural attenuation of contaminants by Arthrobacter sp. SRS-W-1-2016 at the SRS site.

Keywords: bioremediation; uranium; nickel; whole genome sequencing; resistome; comparative
genomics; Arthrobacter

SREL Reprint #3432

Chauhan, A., A. Pathak, R. Jaswal, B. Edwards III, D. Chappell, C. Ball, R. Garcia-Sillas, P. Stothard, and J. C. Seaman. 2018. Physiological and comparative genomic analysis of Arthrobacter sp. SRS-W-1-2016 provides insights on niche adaptation for survival in uraniferous soils. Genes 9(1): 1-19.

This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).