BaeR is the primary regulator of the ethanol stress response [12]. Leblanc et al. identified two flavonoids and also sodium tungstate as novel inducers to BaeSR [13]. These new inducers are natural substrates of the MdtABC efflux pump, and they lead to much stronger induction of the BaeST response in an mdtA efflux pump mutant, while indole does not [13]. As a consequence of this sensing, BaeS is autophosphorylated, followed by the transfer of the phosphate group to BaeR [9], which is converted to an active form [5] that appears to recognize and bind a DNA sequence with a direct repeat symmetry [7]. BaeR exhibits high degrees of sequence similarity with the transcriptional regulators OmpR and PhoB [9] and belongs to the OmpR subfamily whose members contain a DNA-binding motif in the C-terminal domain [9]. The BaeSR, PhoBR, and CreBC two-component systems have been shown to interact in the regulation of gene expression [4]. BaeR suppresses envZ and phoR/creC mutations [9]. The crystal structure of the unphosphorylated dimeric form of BaeR has been determined [14]. BaeR is not an essential protein [15]. BaeR overproduction decreases the expression levels of outer membrane channel TolC, the global regulators MarA and Rob, as well as cephalosporin susceptibility in an acrB mutant strain, mainly by decreasing expression levels of outer membrane proteins (OmpC, OmpF, OmpW, OmpA, and OmpX) [16] Missense mutations in the baeS gene compensate for a mutation in the genes encoding the major antibiotic efflux pumps AcrAB and AcrEF. In these mutations, BaeS appears to activate BaeR constitutively to increase the expression of genes encoding the MdtAB efflux pump [17]. Analysis of RNA-seq analysis showed that BaeS affects the expression of 38 genes in a positive way, including many genes of iron regulon, and 34 genes in a negative way [17]. baeR mutant strains are capable of increasing the number of replication origins, the amount of DnaA protein per cell, and the growth rate [18] An integrated transcriptomic study of the extracytoplasmic stress response, which detects and responds to alterations of the bacterial envelope, was performed by Bury-Mone et al. (2009). They investigated the interconnections and dynamics between Bae, Cpx, Psp, Rcs, and σ^E pathways and showed that these pathways can be activated simultaneously in response to exogenous or endogenous stimulation, while natural environmental stimuli provoke bacterial modifications that lead to multiple pathway responses [19] Each of these responses might be specialized to ensure a specific aspect of envelope biogenesis and maintenance; on the other hand, CpxR could have a role as a modulator of the response by integrating other endogenous signals. Bury-Mone et al. concluded that all five pathways are needed to mount a full response to extracytoplasmic stress [19]