Role of the cell envelope stress regulators BaeR and CpxR in control of RND-type multidrug efflux pumps and transcriptional cross talk with exopolysaccharide synthesis in Erwinia amylovora
- 389 Downloads
The purpose of this study was to identify the role of the cell envelope stress-sensing systems BaeSR and CpxARP in regulation of multidrug efflux and exopolysaccharide synthesis in Erwinia amylovora. We have previously reported that BaeR activates transcription of the RND-type efflux pumps AcrD and MdtABC. In this study, we found that a cpxR-deficient mutant was highly susceptible to β-lactams, aminoglycosides and lincomycin, whereas a baeR mutant showed no change in antimicrobial sensitivity. However, overexpression of BaeR in a mutant lacking the major RND pump AcrB increased resistance of E. amylovora to several compounds that are not substrates of AcrD or MdtABC. Furthermore, we observed that overexpression of BaeR significantly increased amylovoran production. Moreover, the expression of RND-type efflux pumps was changed in regulatory mutants of exopolysaccharide production. Our data suggest that BaeSR and CpxARP regulate additional mechanisms, beside efflux, which are responsible for antimicrobial resistance of E. amylovora.
KeywordsFire blight Transcriptional regulation Two-component system Amylovoran Levan AcrD MdtABC
This study was supported by Jacobs University Bremen and by the MOLIFE Research Center, Jacobs University Bremen. Furthermore, we acknowledge Yvonne Braun for critical reading of the manuscript.
- Clinical and Laboratory Standards Institute (2012) Methods for dilution antimicrobial susceptibility tests for bacteria that grow aerobically. CLSI document M7-A7. Clinical and Laboratory Standards Institute, Wayne, PAGoogle Scholar
- Coleman M, Pearce R, Hitchin E, Busfield F, Mansfield JW, Roberts IS (1990) Molecular cloning, expression and nucleotide sequence of the rcsA gene of Erwinia amylovora, encoding a positive regulator of capsule expression: evidence for a family of related capsule activator proteins. J Gen Microbiol 136:1799–1806PubMedCrossRefGoogle Scholar
- De Las PA, Connolly L, Gross CA (1997) SigmaE is an essential sigma factor in Escherichia coli. J Bacteriol 179:6862–6864Google Scholar
- Hoang TT, Karkhoff-Schweizer RR, Kutchma AJ, Schweizer HP (1998) A broad-host-range Flp-FRT recombination system for site-specific excision of chromosomally-located DNA sequences: application for isolation of unmarked Pseudomonas aeruginosa mutants. Gene 212:77–86. doi: 10.1016/S0378-1119(98)00130-9 PubMedCrossRefGoogle Scholar
- R Core Team (2013) R: a language and environment for statistical computing. R Foundation for Statistical Computing, ViennaGoogle Scholar
- Schenk A, Weingart H, Ullrich MS (2008) Extraction of high-quality bacterial RNA from infected leaf tissue for bacterial in planta gene expression analysis by multiplexed fluorescent Northern hybridization. Mol Plant Pathol 9:227–235. doi: 10.1111/j.1364-3703.2007.00452.x PubMedCrossRefGoogle Scholar