Active efflux of toluene in a solvent-resistant bacterium

Isken, S.; Bont, J.A.M. de

doi:10.1128/jb.178.20.6056-6058.1996

Cited by 143 publications

(103 citation statements)

References 15 publications

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“…This finding may reflect greater expression of acrAB in Mar mutants or a combination of acrAB overexpression and the other changes occurring in a Mar mutant. It is interesting that efflux was associated with toluene resistance in Pseudomonas putida, although the genes were not identified (29).…”

Section: Discussionmentioning

confidence: 99%

Role of the acrAB locus in organic solvent tolerance mediated by expression of marA, soxS, or robA in Escherichia coli

et al. 1997

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Escherichia coli K-12 strains are normally tolerant to n-hexane and susceptible to cyclohexane. Constitutive expression of marA of the multiple antibiotic resistance (mar) locus or of the soxS or robA gene product produced tolerance to cyclohexane. Inactivation of the mar locus or the robA locus, but not the soxRS locus, increased organic solvent susceptibility in the wild type and Mar mutants (to both n-hexane and cyclohexane). The organic solvent hypersusceptibility is a newly described phenotype for a robA-inactivated strain. Multicopy expression of mar, soxS, or robA induced cyclohexane tolerance in strains with a deleted or inactivated chromosomal mar, soxRS, or robA locus; thus, each transcriptional activator acts independently of the others. However, in a strain with 39 kb of chromosomal DNA, including the mar locus, deleted, only the multicopy complete mar locus, consisting of its two operons, produced cyclohexane tolerance. Deletion of acrAB from either wild-type E. coli K-12 or a Mar mutant resulted in loss of tolerance to both n-hexane and cyclohexane. Organic solvent tolerance mediated by mar, soxS, or robA was not restored in strains with acrAB deleted. These findings strongly suggest that active efflux specified by the acrAB locus is linked to intrinsic organic solvent tolerance and to tolerance mediated by the marA, soxS, or robA gene product in E. coli.

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Section: Discussionmentioning

confidence: 99%

Role of the acrAB locus in organic solvent tolerance mediated by expression of marA, soxS, or robA in Escherichia coli

et al. 1997

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“…It has been demonstrated that the degree of toxicity of an organic solvent corresponds to its log P ow value, which is the logarithm of the partition coefficient of the organic solvent between n-octanol and water (Isken & de Bont, 1996;Inoue & Horikoshi, 1989). Organic solvents with a low log P ow value show higher toxicity to micro-organisms.…”

Section: Methodsmentioning

confidence: 99%

“…Microbial resistance to solvents is based mainly on the efflux of cellular solvent influxing from the medium. In Escherichia coli, the solvent efflux is mediated by a solvent-extruding pump system (White et al, 1997;Aono et al, 1998;Tsukagoshi & Aono, 2000); similar systems are also used by Pseudomonas aeruginosa (Li et al, 1998) and Pseudomonas putida (Isken & de Bont, 1996;Kieboom et al, 1998;Ramos et al, 1998;Mosqueda & Ramos, 2000).…”

Section: Introductionmentioning

confidence: 99%

n-Hexane sensitivity of Escherichia coli due to low expression of imp/ostA encoding an 87 kDa minor protein associated with the outer membrane

et al. 2003

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Most Escherichia coli strains are resistant to n-hexane. E. coli OST4251 is a n-hexane-sensitive strain that was constructed by transferring the n-hexane-sensitive phenotype from a n-hexane-sensitive strain by P1 transduction. OST4251 is resistant to diphenyl ether, which is less harmful than n-hexane to micro-organisms. The genetic determinant responsible for this subtle difference in the solvent resistance is mapped at 1·2 min on the E. coli chromosome. Nucleotide sequence analysis showed that IS2 and IS5 had integrated upstream of the imp/ostA structural gene in OST4251. The integration of IS2 decreased the activity of the imp/ostA promoter. A product of the gene was identified immunologically as an 87 kDa minor protein associated with the outer membrane. Upon transformation with plasmids containing the imp/ostA gene, OST4251 produced a high level of the gene product in the membrane and acquired n-hexane resistance. Thus, the low level of promoter activity resulted in low Imp production and the n-hexane-sensitivity phenotype. It is likely that the gene product contributes to n-hexane resistance by reducing the influx of n-hexane.

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“…Similarly, resistance to antibiotics and solvents such as ethanol was found to increase in S12 with exposure to toluene but not antibiotics (279). In [ 14 C]toluene influx studies, an energydependent efflux system was proposed, as less influx was observed in adapted cells, while greater influx was observed in the presence of potassium cyanide, a respiratory chain inhibitor, and m-chlorophenylhydrazone, a proton conductor (276). The interruption of toluene metabolism through mutation of the tod genes did not affect toluene tolerance in DOT-T1E, suggesting that some other mechanism of tolerance was involved (440).…”

Section: Recently Story Et Al (587) Identified a Gene (Pbhd) Inmentioning

confidence: 99%

Recent Advances in Petroleum Microbiology

Hamme¹,

Singh

Ward

2003

Microbiol Mol Biol Rev

1,193

640

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Recent advances in molecular biology have extended our understanding of the metabolic processes related to microbial transformation of petroleum hydrocarbons. The physiological responses of microorganisms to the presence of hydrocarbons, including cell surface alterations and adaptive mechanisms for uptake and efflux of these substrates, have been characterized. New molecular techniques have enhanced our ability to investigate the dynamics of microbial communities in petroleum-impacted ecosystems. By establishing conditions which maximize rates and extents of microbial growth, hydrocarbon access, and transformation, highly accelerated and bioreactor-based petroleum waste degradation processes have been implemented. Biofilters capable of removing and biodegrading volatile petroleum contaminants in air streams with short substrate-microbe contact times (<60 s) are being used effectively. Microbes are being injected into partially spent petroleum reservoirs to enhance oil recovery. However, these microbial processes have not exhibited consistent and effective performance, primarily because of our inability to control conditions in the subsurface environment. Microbes may be exploited to break stable oilfield emulsions to produce pipeline quality oil. There is interest in replacing physical oil desulfurization processes with biodesulfurization methods through promotion of selective sulfur removal without degradation of associated carbon moieties. However, since microbes require an environment containing some water, a two-phase oil-water system must be established to optimize contact between the microbes and the hydrocarbon, and such an emulsion is not easily created with viscous crude oil. This challenge may be circumvented by application of the technology to more refined gasoline and diesel substrates, where aqueous-hydrocarbon emulsions are more easily generated. Molecular approaches are being used to broaden the substrate specificity and increase the rates and extents of desulfurization. Bacterial processes are being commercialized for removal of H2S and sulfoxides from petrochemical waste streams. Microbes also have potential for use in removal of nitrogen from crude oil leading to reduced nitric oxide emissions provided that technical problems similar to those experienced in biodesulfurization can be solved. Enzymes are being exploited to produce added-value products from petroleum substrates, and bacterial biosensors are being used to analyze petroleum-contaminated environments

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Active efflux of toluene in a solvent-resistant bacterium

Abstract: We investigated the mechanisms behind the organic-solvent resistance of the solvent-tolerant strain Pseudomonas putida S12. By use of 14 C-labeled toluene, we obtained evidence that an energy-dependent export system may be responsible for this resistance to toluene.

Cited by 143 publications

References 15 publications

Role of the acrAB locus in organic solvent tolerance mediated by expression of marA, soxS, or robA in Escherichia coli

Role of the acrAB locus in organic solvent tolerance mediated by expression of marA, soxS, or robA in Escherichia coli

n-Hexane sensitivity of Escherichia coli due to low expression of imp/ostA encoding an 87 kDa minor protein associated with the outer membrane

Recent Advances in Petroleum Microbiology

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