Antibiotic Stress, Genetic Response and Altered Permeability of E. coli

Abstract

BackgroundMembrane permeability is the first step involved in resistance of bacteria to an antibiotic. The number and activity of efflux pumps and outer membrane proteins that constitute porins play major roles in the definition of intrinsic resistance in Gram-negative bacteria that is altered under antibiotic exposure.Methodology/Principal FindingsHere we describe the genetic regulation of porins and efflux pumps of Escherichia coli during prolonged exposure to increasing concentrations of tetracycline and demonstrate, with the aid of quantitative real-time reverse transcriptase-polymerase chain reaction methodology and western blot detection, the sequence order of genetic expression of regulatory genes, their relationship to each other, and the ensuing increased activity of genes that code for transporter proteins of efflux pumps and down-regulation of porin expression.Conclusions/SignificanceThis study demonstrates that, in addition to the transcriptional regulation of genes coding for membrane proteins, the post-translational regulation of proteins involved in the permeability of Gram-negative bacteria also plays a major role in the physiological adaptation to antibiotic exposure. A model is presented that summarizes events during the physiological adaptation of E. coli to tetracycline exposure.

The porin and the permeating antibiotic: a selective diffusion barrier in Gram-negative bacteria

“…This leads to an MDR phenotype partly as a result of modified porin expression and reflects a rapid adaptive response to antibiotic stress. The control of bacterial membrane permeability is a complex process that is tightly regulated by an intricate network of systems that sense and respond to osmotic shock, pH, temperature, antibiotics and chemical stress 33,[80][81][82] .…”

Highly Solvent Tolerance in Serratia marcescens IBBPo15

“…5A-5D, only HAE1 and acrAB genes were detected in the genome of S. marcescens IBB Po15 control cells. Nevertheless the used primers (i.e., ompF-f, ompF-r; A24f2, A577r2; acrA-f, acrB-r; recA-f, recA-r) are specific for ompF 6 , HAE1 23 , acrAB 7 and recA 24 genes formerly described, they were not specially designed for the bacteria investigated in this study causing unspecific amplification of other fragments.…”

“…For PCR amplification, 1 μl of DNA extract was added to a final volume of 25 μl reaction mixture, containing: 5×GoTaq flexi buffer, MgCl 2 , dNTP mix, specific primers for ompF, HAE1, acrAB transporter genes (ompF-f and ompF-r, 6 ; A24f2 and A577r2, 23 ; acrA-f and acrB-r, 7 ), recA gene (recA-f and recA-r, 24 ), and GoTaq G2 hot start polymerase (Promega). The PCR program consisted in initial denaturation for 10 min at 94°C, followed by 35 cycles of denaturation at 94°C for 1 min, annealing at 50°C or 55°C for 30 sec, extension at 72°C for 2 min, and a final extension at 72°C for 10 min.…”

“…Membrane transporters, such as porins or efflux pumps, are main filters regulating the internal accumulation of toxic compounds 4 . Porins OmpF (with molecular weight of 41 kDa) and OmpC (40 kDa) which exist in outer membrane of S. marcescens cells are two non-specific protein channels that serve to take in nutrients and toxic compounds, and export waste products 5,6 . Furthermore, the AcrAB-TolC efflux system is a tripartite complex and is a member of the resistance-nodulation-division (RND) family which is considered the major efflux system in members of Enterobacteriaceae family 7 responsible for tolerance to toxic compounds, including organic solvents 8 .…”

Stress responses, outer membrane permeability control and antimicrobial resistance in Enterobacteriaceae

“…Increased expression of the AcrAB efflux pump was found responsible for resistance to TET, which could also be reversed by the use of the efflux pump inhibitor phenylalanine-arginine-b-naphthylamide (PAbN). Interestingly, the TET-resistant strain also exhibited MDR due to repression of OmpF and OmpC expression [24]. Important questions arise from this and other related studies.…”