A combination of sbmA and tolC mutations in Escherichia coli K-12 Tn10-carrying strains results in hypersusceptibility to tetracycline.

DE CRISTOBAL RICARDO E; VINCENT PAULA A; SALOMÓN RAÚL A

JOURNAL OF BACTERIOLOGY

ASM Press

Lugar: Washington, DC; Año: 2008 vol. 190 p. 1491 - 1494

0021-9193

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 microg/ml to resistance at 40 microg/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 microg/ml. Inactivation of sbmA alone partially inhibited high-level tetracycline resistance, from resistance at 200 microg/ml to resistance at 120 microg/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.