Joy D. Van Nostrand¹, Tatiana V. Khijniak², Terry J. Gentry³, Michelle T. Novak¹,
Andrew G. Sowder⁴, Jizhong Z. Zhou^3,5, Paul M. Bertsch^1,4, and Pamela J. Morris<sup>1,6


1</sup>Marine Biomedicine and Environmental Science Center, Medical University of South Carolina, Charleston, SC 29412, USA
²Department of Microbiology and Immunology, Medical University of South Carolina, Charleston, SC 29425, USA
³Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
⁴Savannah River Ecology Laboratory, The University of Georgia, Aiken, SC 29802, USA
⁵Institute for Environmental Genomics, Department of Botany and Microbiology, The University of Oklahoma, Norman, OK 73019, USA
⁶Center for Coastal Environmental Health and Biomolecular Research and Hollings Marine Laboratory, U.S. National Oceanic and Atmospheric Administration, Charleston, SC 29412, USA

Abstract
Microbial communities from riparian sediments contaminated with high levels of Ni and U were examined for
metal-tolerant microorganisms. Isolation of four aerobic Ni-tolerant, Gram-positive heterotrophic bacteria indicated selection pressure fromNi. These isolates were identified as Arthrobacter oxydans NR-1, Streptomyces galbus NR-2, Streptomyces aureofaciens NR-3, and Kitasatospora cystarginea NR-4 based on partial 16S rDNA sequences. A functional gene microarray containing gene probes for functions associated with biogeochemical cycling, metal homeostasis, and organic contaminant degradation showed little overlap among the four isolates. Fifteen of the genes were detected in all four isolates with only two of these related to metal resistance, specifically to tellurium. Each of the four isolates also displayed resistance to at least one of six antibiotics tested, with resistance to kanamycin, gentamycin, and ciprofloxacin observed in at least two of the isolates. Further characterization of S. aureofaciens NR-3 and K. cystarginea NR-4 demonstrated that both isolates expressed Ni tolerance constitutively. In addition, both were able to grow in higher concentrations of Ni at pH 6 as compared with pH 7 (42.6 and 8.5 mM Ni at pH 6 and 7, respectively). Tolerance to Cd, Co, and Zn was also examined in these two isolates; a similar pH-dependent metal tolerance was observed when grown with Co and Zn. Neither isolate was tolerant to Cd. These findings suggest that Ni is exerting a selection pressure at this site for metal-resistant actinomycetes.



SREL Reprint #3033



Van Nostrand, J. D., T. V. Khijniak, T. J. Gentry, M. T. Novak, A. G. Sowder, J. Z. Zhou, P. M. Bertsch, and P. J. Morris. 2007. Isolation and Characterization of Four Gram-Positive Nickel-Tolerant Microorganisms from Contaminated Sediments. Microbial Ecology 53:670-682.

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