## 1 Introduction
Co-selection occurs through the following mechanisms: (a) co-resistance- when there is physical proximity of the resistance encoding antibiotics and/or metal resistance, e.g., on the same genetic element (plasmid) or in the same cell (e.g., _merA_ and _KPC_ beta-lactamase); (b) cross-resistance-when a single resistance functions to provide efflux and antibiotic resistance (e.g., _mdrL_ confers resistance to metals, such as zinc, cobalt, and chromium, along with antibiotics, such as erythromycincin, josamycin, and clindamycin) [11]; and (c) co-regulatory resistance- in this situation, multiple resistance genes conferring resistance to different toxic compounds, including antibiotics, biocides, and metals, are controlled by a single regulatory gene element (e.g., _czCR_ regulating the expression of the _CzcCBA_efflux pump, resulting in the resistance to zinc, cadmium, and cobalt, along with co-regulating resistance to antibiotic carbapenems [12]. To further understand environmentally-relevant genomic mechanisms that underpin microbial survival in radionuclide and heavy metal-rich ecosystems, we recently isolated several bacterial strains in the presence of high concentrations of both U and Ni [13]. 16S-gene based analysis revealed that the isolated strains mainly belonged to _Burkholderia_ spp. and _Arthrobacter_ spp.--genera demonstrated to serve as bioindicators of environmental contamination, as well as agents of bioremediation, especially U [14]. In fact, _Arthrobacter_ spp., were found to be predominant in the U-contaminated Hanford site [15], which is another DOE site in Washington State having a similar U contamination history as the SRS site. _Arthrobacter_ spp., have also been isolated from ecosystems under extreme environmental stresses, such as a nuclear waste plume amd U mined site, as well as heavy metal contaminated habitats [16; 17; 18; 19; 20; 14]. Therefore, it appears that _Arthrobacter_ spp., have recruited strong genomic traits to be able to colonize and survive in radionuclide and metal contaminated habitats. Understanding the basis of metal-micrbial interactions, therefore, is a prerequisite for the successful management and/or rehabilitation of nuclear-legacy contaminated environments. We recently characterized the genomic traits of _Burkholderia_ sp. strain SRS-W-2-2016, a bacterial strain isolated from the same cohort as _Arthrobacter_ sp. SRS-W-1-2016 [13]; which revealed the presence of several gene homologues previously demonstrated to code for the resistance of heavy metals and radionuclides, forming the basis of this study. Specifically, in this study, we report several ecologically relevant genomic traits present in _Arthrobacter_ sp. SRS-W-1-2016, including a suite of substrate binding proteins, permeases, transport regulators, and efflux pumps- likely working in concert to potentially detoxify toxic metals and thus facilitating the natural attenuation of contaminants within the SRS impacted ecosystem. Such genome-enabled studies will facilitate a deeper understanding of heavy metal and antibiotic resistance and hydrocarbon degradative mechanisms in complex, mixed contaminant habitats and provide recommendations for the environmental stewardship of anthropogenically-impacted environments.