The BceRS two-component regulatory system induces expression of the bacitracin transporter, BceAB, in Bacillus subtilis.
ABSTRACT BceA and bceB encode a nucleotide-binding domain (NBD) and membrane-spanning domain (MSD) subunit, respectively, of an ATP-binding cassette (ABC) transporter in Bacillus subtilis. Disruption of these genes resulted in hypersensitivity to bacitracin, a peptide antibiotic that is non-ribosomally synthesized in some strains of Bacillus. Northern hybridization analyses showed that expression of the bceAB operon is induced by bacitracin present in the growth medium. The bceRS genes encoding a two-component regulatory system are located immediately upstream of bceAB. Deletion analyses of the bceAB promoter together with DNase I footprinting experiments revealed that a sensor kinase, BceS, responds to extracellular bacitracin either directly or indirectly and transmits a signal to a cognate response regulator, BceR. The regulator binds directly to the upstream region of the bceAB promoter and upregulates the expression of bceAB genes. The bcrC gene product is additionally involved in bacitracin resistance. The expression of bcrC is dependent on the ECF sigma factors, sigmaM and sigmaX, but not on the BceRS two-component system. In view of these results, possible roles of BceA, BceB and BcrC in bacitracin resistance of B. subtilis 168 are discussed.
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ABSTRACT: To study the functions of the uncharacterized open reading frames identified in the Bacillus subtilis genome, several vectors were constructed to perform insertional mutagenesis in the chromosome. All the pMUTIN plasmids carry a lacZ reporter gene and an inducible Pspac promoter, which is tightly regulated and can be induced about 1000-fold. The integration of a pMUTIN vector into the target gene has three consequences: (1) the target gene is inactivated; (2) lacZ becomes transcriptionally fused to the gene, allowing its expression pattern to be monitored; (3) the Pspac promoter controls the transcription of downstream genes in an IPTG-dependent fashion. This last feature is important because B. subtilis genes are often organized in operons. The potential polar effects generated by the integration of the vectors can be alleviated by addition of IPTG. Also, conditional mutants of essential genes can be obtained by integrating pMUTIN vectors upstream of the target gene. The vectors are currently being used for systematic inactivation of genes without known function within the B. subtilis European consortium. pMUTIN characteristics and the inactivation of eight genes in the resA-serA region of the chromosome are presented.Microbiology 12/1998; 144 ( Pt 11):3097-104. · 2.85 Impact Factor
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ABSTRACT: Resistance of Lactococcus lactis to cytotoxic compounds shares features with the multidrug resistance phenotype of mammalian tumor cells. Here, we report the gene cloning and functional characterization in Escherichia coli of LmrA, a lactococcal structural and functional homolog of the human multidrug resistance P-glycoprotein MDR1. LmrA is a 590-aa polypeptide that has a putative topology of six alpha-helical transmembrane segments in the N-terminal hydrophobic domain, followed by a hydrophilic domain containing the ATP-binding site. LmrA is similar to each of the two halves of MDR1 and may function as a homodimer. The sequence conservation between LmrA and MDR1 includes particular regions in the transmembrane domains and connecting loops, which, in MDR1 and the MDR1 homologs in other mammalian species, have been implicated as determinants of drug recognition and binding. LmrA and MDR1 extrude a similar spectrum of amphiphilic cationic compounds, and the activity of both systems is reversed by reserpine and verapamil. As LmrA can be functionally expressed in E. coli, it offers a useful prokaryotic model for future studies on the molecular mechanism of MDR1-like multidrug transporters.Proceedings of the National Academy of Sciences 11/1996; 93(20):10668-72. · 9.74 Impact Factor
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ABSTRACT: A new antibiotic "bacitracin" has been recovered from a strain of the B. subtilis group of organisms. It is neutral, water-soluble, non-toxic and relatively heat stable. In vitro it is active chiefly against Grampositive organisms, but the gonococcus and meningococcus are susceptible to its action. It is also active in vivo against experimentally produced hemolytic streptococcal infections in mice and gas gangrene infections in guinea pigs. Clinical use in hemolytic streptococcal and staphylococcal infections in man have given encouraging results.Science 11/1945; 102(2650):376-7. · 31.03 Impact Factor