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Journal of Bacteriology, February 2008, p. 1491-1494, Vol. 190, No. 4
0021-9193/08/$08.00+0     doi:10.1128/JB.01844-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

A Combination of sbmA and tolC Mutations in Escherichia coli K-12 Tn10-Carrying Strains Results in Hypersusceptibility to Tetracycline{triangledown}

Ricardo E. de Cristóbal, Paula A. Vincent, and Raúl A. Salomón*

Departamento de Bioquímica de la Nutrición, Instituto Superior de Investigaciones Biológicas, Consejo Nacional de Investigaciones Científicas y Técnicas-Universidad Nacional de Tucumán, and Instituto de Química Biológica Dr. Bernabé Bloj, Chacabuco 461, 4000 San Miguel de Tucumán, Tucumán, Argentina

Received 22 November 2007/ Accepted 1 December 2007

Previously, we demonstrated that Escherichia coli tolC mutations reduce the high-level resistance to tetracycline afforded by the transposon Tn10-encoded TetA pump from resistance at 200 µg/ml to resistance at 40 µg/ml. In this study, we found that the addition of an sbmA mutation to a tolC::Tn10 mutant exacerbates this phenotype: the double mutant did not form colonies, even in the presence of tetracycline at a concentration as low as 5 µg/ml. Inactivation of sbmA alone partially inhibited high-level tetracycline resistance, from resistance at 200 µg/ml to resistance at 120 µg/ml. There thus appears to be an additive effect of the mutations, resulting in almost complete suppression of the phenotypic expression of Tn10 tetracycline resistance.

* Corresponding author. Mailing address: Departamento de Bioquímica de la Nutrición, INSIBIO, Chacabuco 461, 4000 San Miguel de Tucumán, Argentina. Phone and fax: (54) (381) 4248921. E-mail: salomon{at}fbqf.unt.edu.ar

{triangledown} Published ahead of print on 14 December 2007.

Journal of Bacteriology, February 2008, p. 1491-1494, Vol. 190, No. 4
0021-9193/08/$08.00+0     doi:10.1128/JB.01844-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.





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