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Benzo[de]chromene‐7,8‐dione derivatives are known to have important biological and pharmacological properties. Thus, a novel and efficient method was developed for the synthesis of benzo[de]chromene‐7,8‐dione derivatives via the tandem reaction of 5‐bromo‐2‐hydroxynaphthalene‐1,4‐dione and terminal alkynes, which proceeds under the typical reaction conditions for Sonogashira coupling using Pd and Cu catalysts. The process likely occurs via a tandem reaction due to the synthesized Sonogashira coupling product undergoing intramolecular cyclization in the presence of a Cu catalyst. This method is superior to existing synthesis methods in that it can access benzo[de]chromene‐7,8‐dione compounds without the post‐oxidation of benzo[de]chromenes. Furthermore, it enables the direct supply of several biologically active compounds. The minimum inhibitory concentrations (MICs) of the synthesized compounds against multidrug efflux pump‐deficient strains of S. aureus, E. coli, and P. aeruginosa and their parent strains were determined. Certain synthesized compounds exhibited strong antimicrobial activity, indicating that they are substrates for multidrug efflux pumps. [ABSTRACT FROM AUTHOR]

The PA5471 gene required for induction of the MexXY multidrug efflux system in response to ribosometargeting antimicrobials was itself shown to be inducible by ribosome-targeting antimicrobials (Y. Morita, M. L. Sobel, and K. Poole, J. Bacteriol. 188:1847-1855, 2006). Using a lacZ transcriptional reporter, drug inducibility of PA5471 was shown to require the entirety of the 367-bp PA5472-PA5471 intergenic region. A constitutive promoter activity was, however, localized to the first 75 bp of this region, within which a single PA5471 transcription initiation site was mapped. That 3' sequences of the intergenic region blocked PA5471 expression and made it antibiotic dependent was suggestive of an attenuation mechanism of control. A 13-amino-acid leader peptide (LP)-encoding open reading frame preceded by a Shine-Dalgarno sequence was identified ca. 250 bp upstream of the PA5471 coding sequence, and its expression and translation were confirmed using a lacZ translational reporter. Alteration of the initiation codon (M1T) or introduction of translational stop signals at codons 3 (Q3Am) and 8 (C8Op) of this LP sequence (PA5471.1) yielded high-level constitutive expression of PA5471, suggesting that interference with LP translation was linked to PA5471 gene expression. Consistent with this, a Q3K mutation in the LP sequence maintained the drug inducibility of PA5471 expression. Introduction of the LP Q3Am mutation into the chromosome of Pseudomonas aeruginosa yielded stronger expression of PA5471 than did antibiotic (chloramphenicol) exposure of wild-type P. aeruginosa, in agreement with lacZ transcriptional fusion data. Still, the Q3Am mutation yielded modest expression of mexXY, less than that seen for antibiotic-treated wild-type P. aeruginosa. These data suggest that PA5471 is not sufficient for MexXY recruitment in response to antibiotic exposure and that additional antibiotic-dependent effects are needed.

Genes vmeA and vmeB, encoding a multidrug efflux transporter in the halophilic bacterium Vibrio parahaemolyticus, have been cloned using a drug-hypersusceptible Escherichia coli strain as the host. Cells of E. coli KAM33 ([DELTA]acrAB [DELTA]ydhE) carrying the vmeAB region from V. parahaemolyticus conferred much higher MICs for a variety of antimicrobial agents than did control cells. Cells possessing VmeAB under energized conditions maintained very low intracellular concentrations of ethidium. This was as expected for an energy-dependent efflux system, and supports the notion--based on sequence homology--that VmeAB belongs to the resistance nodulation cell division (RND) family of multidrug efflux transporters. It is likely that VmeAB forms functional complexes with the outer-membrane protein TolC in E. coli, because introduction of vmeAB into cells of E. coli KAM43, which lacks the tolC gene, failed to elevate the MICs for any of the antimicrobial agents tested. Therefore, a V. parahaemolyticus homologue of tolC was also cloned, designated vpoC, and was introduced together with vmeAB into cells of E. coli KAM43. The MICs of all agents tested were raised and were comparable to the values observed in E. coli KAM33 harbouring a plasmid carrying vmeAB. Finally, a vmeAB-deficient mutant of V. parahaemolyticus was constructed (designated TM3). TM3 showed slightly higher susceptibility than the parental V. parahaemolyticus to some antimicrobial agents. Survival rate of the TM3 when exposed to deoxycholate decreased compared with that of the parent.

The Pseudomonas aeruginosa nalD gene encodes a TetR family repressor with homology to the SmeT and TtgR repressors of the smeDEF and ttgABC multidrug efflux systems of Stenotrophomonas maltophilia and Pseudomonas putida, respectively. A sequence upstream of mexAB-oprM and overlapping a second promoter for this efflux system was very similar to the SmeT and TtgR operator sequences, and NalD binding to this region was, in fact, demonstrated. Moreover, increased expression from this promoter was seen in a nalD mutant, consistent with NalD directly controlling mexAB-oprM expression from a second promoter.

The extracellular production of recombinant neoculin (rNCL) with sensory activities by Aspergillus oryzae is reported and an efficient strategy is designed to express the two heterodimeric subunits with different productivities and increased rNCL production level by constitutive induction of the unfolded protein response (UPR). The analysis has shown that the A. oryzae production system is useful for the production of heterooligomeric proteins as well as for probing the molecular biology of this unique taste-modifying protein.

The MexXY components of the MexXY-OprM multidrug efflux system of Pseudomonas aeruginosa are encoded by a MexZ repressor-regulated operon that is inducible by antibiotics that target the ribosome. Mutant strains disrupted in a gene, PA5471, were shown to be compromised for drug-inducible mexAT expression and, therefore, MexXY-OprM-mediated antimicrobial resistance. The PA5471 gene was inducible by the same ribosometargeting agents that induce mexXY expression. Moreover, vector-driven expression of cloned PA5471 was sufficient to promote mexXY expression and MexXY-mediated resistance in the absence of antibiotic exposure, consistent with PA5471 directly or indirectly activating mexXY expression following its own upregulation in response to antibiotics. The requirement for PA5471 for mexAT expression and antimicrobial resistance was, however, obviated in mutants lacking the MexZ repressor of mexXY expression, suggesting that PA5471 directly or indirectly modulates MexZ activity in effecting mexXY expression. While the recruitment of PA5471 and MexXY in response to ribosome disruption by antimicrobials is consistent with their genes playing a role in protecting cells from the adverse consequences of disrupting the translation process, reminiscent of transtranslation, these genes appear to operate independently in their contribution to resistance: mutants defective in trans-translation showed a much more modest (twofold) decrease in resistance to ribosome-targeting agents than those lacking PA5471 or MexXY, and this decrease was observed whether functional PA5471/MexXY was present or not.

NorM is a member of the multidrug and toxic compound extrusion (MATE) family and functions as a [Na.sup.+]/multidrug antiporter in Vibrio parahaemolyticus, although the underlying mechanism of the [Na.sup.+]/multidrug antiport is unknown. Acidic amino acid residues Asp32, Glu251, and Asp367 in the transmembrane region of NorM are conserved in one of the clusters of the MATE family. In this study, we investigated the role(s) of acidic amino acid residues Asp32, Glu251, and Asp367 in the transmembrane region of NorM by site-directed mutagenesis. Wild-type NorM and mutant proteins with amino acid replacements D32E (D32 to E), D32N, D32K, E251D, E251Q, D367A, D367E, D367N, and D367K were expressed and localized in the inner membrane of Escherichia coli KAM32 cells, while the mutant proteins with D32A, E251A, and E251K were not. Compared to cells with wild-type NorM, cells with the mutant NorM protein exhibited reduced resistance to kanamycin, norfloxacin, and ethidium bromide, but the NorM D367E mutant was more resistant to ethidium bromide. The NorM mutant D32E, D32N, D32K, D367A, and D367K cells lost the ability to extrude ethidium ions, which was [Na.sup.+] dependent, and the ability to move [Na.sup.+], which was evoked by ethidium bromide. Both E251D and D367N mutants decreased [Na.sup.+]-dependent extrusion of ethidium ions, but ethidium bromide-evoked movement of [Na.sup.+] was retained. In contrast, D367E caused increased transport of ethidium ions and [Na.sup.+]. These results suggest that Asp32, Glu251, and Asp367 are involved in the [Na.sup.+]-dependent drug transport process.

We cloned the gene PA1361 (we designated the gene pmpM), which seemed to encode a multidrug efflux pump belonging to the MATE family, of Pseudomonas aeruginosa by the PCR method using the drug-hypersensitive Escherichia coli KAM32 strain as a host. Cells of E. coli possessing the pmpM gene showed elevated resistance to several antimicrobial agents. We observed energy-dependent efflux of ethidium from cells possessing the pmpM gene. We found that PmpM is an [H.sup.+]-drug antiporter, and this finding is the first reported case of an [H.sup.+] -coupled efflux pump in the MATE family. Disruption and reintroduction of the pmpM gene in P. aeruginosa revealed that PmpM is functional and that benzalkonium chloride, fluoroquinolones, ethidium bromide, acriflavine, and tetraphenylphosphonium chloride are substrates for PmpM in this microorganism.

The multidrug efflux pump, VmrA, from Vibrio parahaemolyticus catalyzes acriflavine efflux and exhibits sodium/drug transporter activity. Addition of tetraphenylphosphonium to sodium loaded cells causes sodium efflux.

Research has been conducted on the NorM of Vibrio parahaemolyticus, a multidrug efflux protein. The experiments have been conducted in investigating whether the NorM multidrug efflux pump of V. parahaemolyticus is a Na (super)+ /drug antiporter.

Research demonstrates that although small multidrug resistance involves only one gene, either ebrA or ebrB, for multidrug efflux pump activity both genes (ebrAB) are required in Bacillus subtilis.