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Applied and Environmental Microbiology, April 2007, p. 2199-2206, Vol. 73, No. 7
0099-2240/07/$08.00+0     doi:10.1128/AEM.02511-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Novel Tetracycline Resistance Determinant Isolated from an Environmental Strain of Serratia marcescens{triangledown}

Stuart A. Thompson,1* Elizabeth V. Maani,1 Angela H. Lindell,2 Catherine J. King,2 and J. Vaun McArthur2

Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, Georgia 30912,1 Savannah River Ecology Laboratory, University of Georgia, Aiken, South Carolina 298022

Received 27 October 2006/ Accepted 6 February 2007

Resistances to tetracycline and mercury were identified in an environmental strain of Serratia marcescens isolated from a stream highly contaminated with heavy metals. As a step toward addressing the mechanisms of coselection of heavy metal and antibiotic resistances, the tetracycline resistance determinant was cloned in Escherichia coli. Within the cloned 13-kb segment, the tetracycline resistance locus was localized by deletion analysis and transposon mutagenesis. DNA sequence analysis of an 8.0-kb region revealed a novel gene [tetA(41)] that was predicted to encode a tetracycline efflux pump. Phylogenetic analysis showed that the TetA(41) protein was most closely related to the Tet(39) efflux protein of Acinetobacter spp. yet had less than 80% amino acid identity with known tetracycline efflux pumps. Adjacent to the tetA(41) gene was a divergently transcribed gene [tetR(41)] predicted to encode a tetracycline-responsive repressor protein. The tetA(41)-tetR(41) intergenic region contained putative operators for TetR(41) binding. The tetA(41) and tetR(41) promoters were analyzed using lacZ fusions, which showed that the expression of both the tetA(41) and tetR(41) genes exhibited TetR(41)-dependent regulation by subinhibitory concentrations of tetracycline. The apparent lack of plasmids in this S. marcescens strain, as well as the presence of metabolic genes adjacent to the tetracycline resistance locus, suggested that the genes were located on the S. marcescens chromosome and may have been acquired by transduction. The cloned Tet 41 determinant did not confer mercury resistance to E. coli, confirming that Tet 41 is a tetracycline-specific efflux pump rather than a multidrug transporter.

* Corresponding author. Mailing address: Department of Biochemistry and Molecular Biology, Medical College of Georgia, 1120 15th Street, Augusta, GA 30912-2100. Phone: (706) 721-7277. Fax: (706) 721-6608. E-mail: stthomps{at}mcg.edu.

{triangledown} Published ahead of print on 16 February 2007.

Applied and Environmental Microbiology, April 2007, p. 2199-2206, Vol. 73, No. 7
0099-2240/07/$08.00+0     doi:10.1128/AEM.02511-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Akers, K. S., Mende, K., Yun, H. C., Hospenthal, D. R., Beckius, M. L., Yu, X., Murray, C. K. (2009). Tetracycline Susceptibility Testing and Resistance Genes in Isolates of Acinetobacter baumannii-Acinetobacter calcoaceticus Complex from a U.S. Military Hospital. Antimicrob. Agents Chemother. 53: 2693-2695 [Abstract] [Full Text]  
  • Brown, M. G., Mitchell, E. H., Balkwill, D. L. (2008). Tet 42, a Novel Tetracycline Resistance Determinant Isolated from Deep Terrestrial Subsurface Bacteria. Antimicrob. Agents Chemother. 52: 4518-4521 [Abstract] [Full Text]  
  • van Hoek, A. H. A. M., Mayrhofer, S., Domig, K. J., Florez, A. B., Ammor, M. S., Mayo, B., Aarts, H. J. M. (2008). Mosaic Tetracycline Resistance Genes and Their Flanking Regions in Bifidobacterium thermophilum and Lactobacillus johnsonii. Antimicrob. Agents Chemother. 52: 248-252 [Abstract] [Full Text]  


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