Plasmid-Mediated Overexpression of AcrS May Decrease Kanamycin Resistance in Escherichia coli

09/05/2018

Maria-Elizabeth Baeva, Andrew P. Golin, Shivani Mysuria, Priya Suresh​

Volume 4
Fall 2017 / Winter 2018

SUMMARY Escherichia coli encodes efflux pumps that confer resistance to antimicrobial compounds. Previous studies have shown that efflux pumps AcrAB and AcrEF have similar structures and functions, and may be repressed by homologous transcriptional repressors. The transcriptional repressor AcrR, represses the acrAB operon. A gene encoding a less-studied putative transcriptional repressor AcrS, and acrR are both located upstream of acrEF and acrAB, respectively. Deleting acrS in Escherichia coli has also shown to result in increased levels of acrE mRNA when cultured in the presence of sub-inhibitory concentrations of kanamycin. Given this evidence that AcrS may repress acrE, we hypothesize that increasing AcrS expression will result in increased repression of acrE and confer a decrease in kanamycin resistance. An inducible expression vector containing acrS was constructed and transformed into wild-type E. coli strain BW25113, as well as strains bearing deletions of acrS or acrE. Resistance to kanamycin was tested using a minimum inhibitory concentration assay. Results from this study suggest that overexpressing AcrS decreased kanamycin resistance in E. coli BW25113. This supports the hypothesis that AcrS may be a transcriptional repressor of acrE in E. coli BW25113.