Expression of rprA, a Regulator of RpoS Translation, Increases Tolerance to Kanamycin in RcsB-deficient Escherichia coli K-12

Abstract

Activation of the Rcs phosphorelay system of Escherichia coli can increase translation of rpo S mRNA through stabilization by the small non-coding mRNA, rpr A. Increased RpoS levels in the cell causes up-regulation of a variety of genes that enhance the cellular stress response. Previous studies have proposed that the increased susceptibility to kanamycin of a Δ rcs B strain was due to an inability to produce extracellular capsule. However, the RcsB regulator has the additional role of regulating RpoS translation through rpr A. In this study, we investigated whether constitutive expression of rpr A in an RcsB-deficient strain is capable of restoring kanamycin resistance. The rpr A deletion mutant was supplemented with an rpr A-containing plasmid, and an MIC assay was used to compare the level of resistance to kanamycin with an isogenic wild-type strain. It was found that expression of rpr A increased the MIC from 12 μg/ml to 24 μg/ml of kanamycin in the wild-type and from 8 μg/ml to 16 μg/ml of kanamycin in the Δ rcs B strain. These preliminary data suggest that rpr A expression increased the resistance to kanamycin in both WT and Δ rcs B cells.