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Curr Microbiol (2009) 59:526531
DOI 10.1007/s00284-009-9471-2
Comparison of Two Multimetal Resistant Bacterial Strains: Enterobacter sp. YSU and Stenotrophomonas maltophilia ORO2
Andrew Holmes Anubhav Vinayak Cherise Benton Aaron Esbenshade Carlisle Heinselman Daniel Frankland Samatha Kulkarni Adrienne Kurtanich Jonathan Caguiat
Received: 16 January 2009 / Accepted: 21 July 2009 / Published online: 18 August 2009 Springer Science+Business Media, LLC 2009
Abstract The Y-12 plant in Oak Ridge, TN, which manufactured nuclear weapons during World War II and the Cold War, contaminated East Fork Poplar Creek with heavy metals. The multimetal resistant bacterial strain, Stenotrophomonas maltophilia Oak Ridge strain O2 (S. maltophilia O2), was isolated from East Fork Poplar Creek. Sequence analysis of 16s rDNA suggested that our working strain of S. maltophilia O2 was a strain of Enterobacter. Phylogenetic tree analysis and biochemical tests conrmed that it belonged to an Enterobacter species. This new strain was named Enterobacter sp. YSU. Using a modied R3A growth medium, R3A-Tris, the Hg(II), Cd(II), Zn(II), Cu(II), Au(III), Cr(VI), Ag(I), As(III), and Se(IV) MICs for a conrmed strain of S. maltophilia O2 were 0.24, 0.33, 5, 5, 0.25, 7, 0.03, 14, and 40 mM, respectively, compared to0.07, 0.24, 0.8, 3, 0.05, 0.4, 0.08, 14, and 40 mM, respectively, for Enterobacter sp. YSU. Although S. maltophilia O2 was generally more metal resistant than Enterobacter sp. YSU, in comparison to Escherichia coli strain HB101, Enterobacter sp. YSU was resistant to Hg(II), Cd(II), Zn(II), Au(III), Ag(I), As(III), and Se(IV). By studying metal resistances in these two strains, it may be possible to understand what makes one microorganism more metal resistant than another microorganism. This work also provided benchmark MICs that can be used to
evaluate the metal resistance properties of other bacterial isolates from East Fork Poplar Creek and other metal contaminated sites.
Introduction
The Y-12 plant in Oak Ridge, TN played an important role in national defense of the USA during the last 60 years of the twentieth century. It processed uranium during World War II to make the rst nuclear bomb [29]. With the beginning of the Cold War in the 1950s, the Y-12 plant switched to lithium processing for manufacturing hydrogen bombs. This process required large amounts of mercury, which was not tightly contained, and about 920,000 kg were spilled into East...