BaeR Is Required for Upregulation of Expression of acrD in Escherichia coli Following Treatment with Subinhibitory Concentrations of Kanamycin

09/01/2016

Faraz Bateni, Matthew Dickey, Hatim Hanafi, Brian Vickers​

Volume 20
Fall 2015 / Winter 2016

The AcrAD-TolC efflux pump of Escherichia coli K-12 expels aminoglycosides such as kanamycin from the cell. The expression of genes encoding for proteins which make up the efflux pump are known to be regulated by the two-component systems BaeSR. In E. coli BaeSR has been shown to regulate the expression of acrD in response to treatment with subinhibitory concentrations of kanamycin but the direction of its regulation of acrD expression has not been established. One study’s findings suggested that BaeR functions to upregulate acrD expression while another study suggested that BaeR downregulates acrD expression in response to subinhibitory concentrations of kanamycin. To resolve these conflicting results, this study explored the direction of BaeR’s regulation of acrD expression. Reverse Transcription-qPCR was used to measure levels of acrD expression following exposure to subinhibitory concentrations of kanamycin in both wild type and baeR deletion mutant strains. In the wild type strain, a three-fold increase in acrD expression levels was observed post kanamycin treatment. In the baeR deletion mutant, no statistically significant change in expression levels was detected suggesting that BaeR is required for induction of acrD expression. These findings suggest that BaeR positively regulates expression of acrD in E. coli following treatment with subinhibitory concentrations of kanamycin treatment.

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