Involvement of Outer Membrane Protein TolC, a Possible Member of the
            <i>mar-sox</i>
            Regulon, in Maintenance and Improvement of Organic Solvent Tolerance of
            <i>Escherichia coli</i>
            K-12

Aono, Rikizo; Tsukagoshi, Norihiko; Yamamoto, Mami

doi:10.1128/jb.180.4.938-944.1998

Cited by 173 publications

(50 citation statements)

References 49 publications

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“…The Escherichia coli soxRS regulon is composed of at least 17 related genes which respond to the redox status of the cell (Greenberg et al, 1990;Liochev et al, 1994;Ma et al, 1996;Aono et al, 1998). SoxR is a dimeric sensor with two [2Fe-2S] centers that detects oxidative stress and induces expression of soxS gene, which encodes a positive transcriptional regulator belonging to the AraC/XylS family that, in turn, induces expression of the genes of the sox regulon (Amábile-Cuevas & Demple, 1991;Wu & Weiss, 1992;Li & Demple, 1994;Ding et al, 1996;Pomposiello et al, 2001).…”

Section: Regulation Of Nitroreductase Gene Expressionmentioning

confidence: 99%

Reduction of polynitroaromatic compounds: the bacterial nitroreductases

et al. 2008

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Most nitroaromatic compounds are toxic and mutagenic for living organisms, but some microorganisms have developed oxidative or reductive pathways to degrade or transform these compounds. Reductive pathways are based either on the reduction of the aromatic ring by hydride additions or on the reduction of the nitro groups to hydroxylamino and/or amino derivatives. Bacterial nitroreductases are flavoenzymes that catalyze the NAD(P)H-dependent reduction of the nitro groups on nitroaromatic and nitroheterocyclic compounds. Nitroreductases have raised a great interest due to their potential applications in bioremediation, biocatalysis, and biomedicine, especially in prodrug activation for chemotherapeutic cancer treatments. Different bacterial nitroreductases have been purified and their biochemical and kinetic parameters have been determined. The crystal structure of some nitroreductases have also been solved. However, the physiological role(s) of these enzymes remains unclear. Nitroreductase genes are widely spread within bacterial genomes, but are also found in archaea and some eukaryotic species. Although studies on regulation of nitroreductase gene expression are scarce, it seems that nitroreductase genes may be controlled by the MarRA and SoxRS regulatory systems that are involved in responses to several antibiotics and environmental chemical hazards and to specific oxidative stress conditions. This review covers the microbial distribution, types, biochemical properties, structure and regulation of the bacterial nitroreductases. The possible physiological functions and the biotechnological applications of these enzymes are also discussed.

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Section: Regulation Of Nitroreductase Gene Expressionmentioning

confidence: 99%

Reduction of polynitroaromatic compounds: the bacterial nitroreductases

et al. 2008

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“…Piddock et al [70] found no di¡erences in the DNA sequence of acrR and the promoter region of acrAB between the MAR isolates and the pre-therapy parent strain, suggesting that any mutation mediating resistance is more likely to be found in another regulatory gene. It would be interesting to examine whether the expression of a Rob homologue is increased in these isolates, as it is known that this protein a¡ects the function of the AcrAB e¥ux pump in E. coli [71,72]. Accumulation of cipro£oxacin, tetracycline and chloramphenicol by some of the MAR isolates of S. Typhimurium was increased by CCCP but remained well below the concentrations accumulated by the pre-therapy isolate [70].…”

Section: Multiple Drug Resistance and E¥ux In Human Isolatesmentioning

confidence: 99%

Fluoroquinolone resistance in Salmonella serovars isolated from humans and food animals

Piddock¹

2002

FEMS Microbiology Reviews

117

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Quinolone-resistant Salmonella enterica usually contain a mutation in gyrA within the region encoding the quinolone resistance determining region of the A subunit of DNA gyrase. These mutations confer substitutions analogous to Escherichia coli Ser83-->Phe and Asp87-->Gly or Tyr, or a novel mutation resulting in Ala119-->Glu or Val. Mutations in gyrB are rare, and no mutations in parC or parE have been described. Quinolone-resistant Salmonella can also be cross-resistant to other agents including chloramphenicol and tetracycline. Increased efflux has been demonstrated and for some strains this has been associated with increased expression of acrB. Mutation in soxR has also been shown for one isolate. Detection of low level resistance (minimum inhibitory concentrations <0.5 microg ml(-1)) to fluoroquinolones is proving an increasing problem in the treatment of invasive Salmonella infections.

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“…The outer membrane protein TolC belongs to a family of envelope proteins found in all Gram-negative bacteria and is essential for the expulsion of a plethora of compounds (Eswaran et al ., 2003). TolC is not only important for the efflux of small compounds such as organic solvents and antibiotics, but also for the export of large proteins such as α -haemolysin (Aono et al ., 1998;Vakharia et al ., 2001;Nishino et al ., 2003).…”

Section: Introductionmentioning

confidence: 99%

The AcrAB-TolC efflux system of Salmonella enterica serovar Typhimurium plays a role in pathogenesis

Buckley

Webber

Cooles³

et al. 2006

Cell Microbiol

202

190

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SummaryThe ability of an isogenic set of mutants of Salmonella enterica serovar Typhimurium L354 (SL1344) with defined deletions in genes encoding components of tripartite efflux pumps, including acrB , acrD , acrF and tolC , to colonize chickens was determined in competition with L354. In addition, the ability of L354 and each mutant to adhere to, and invade, human embryonic intestine cells and mouse monocyte macrophages was determined in vitro . The tolC and acrB knockout mutants were hyper-susceptible to a range of antibiotics, dyes and detergents; the tolC mutant was also more susceptible to acid pH and bile and grew more slowly than L354. Complementation of either gene ablated the phenotype. The tolC mutant poorly adhered to both cell types in vitro and was unable to invade macrophages. The acrB mutant adhered, but did not invade macrophages . In vivo , both the acrB mutant and the tolC mutant colonized poorly and did not persist in the avian gut, whereas the acrD and acrF mutant colonized and persisted as well as L354. These data indicate that the AcrAB-TolC system is important for the colonization of chickens by S . Typhimurium and that this system has a role in mediating adherence and uptake into target host cells.

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Involvement of Outer Membrane Protein TolC, a Possible Member of the mar-sox Regulon, in Maintenance and Improvement of Organic Solvent Tolerance of Escherichia coli K-12

Cited by 173 publications

References 49 publications

Reduction of polynitroaromatic compounds: the bacterial nitroreductases

Reduction of polynitroaromatic compounds: the bacterial nitroreductases

Fluoroquinolone resistance in Salmonella serovars isolated from humans and food animals

The AcrAB-TolC efflux system of Salmonella enterica serovar Typhimurium plays a role in pathogenesis

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