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At least 19 recordsLinked to original sources

PubMed1994

Effect of trichloroethylene (TCE) and toluene concentrations on TCE and toluene biodegradation and the population density of TCE and toluene degraders in soil.

Toluene is one of several cosubstrates able to support the cometabolism of trichloroethylene (TCE) by soil microbial communities. Indigenous microbial populations in soil degraded TCE in the presence, but not the absence, of toluene after a 60- to 80-h lag period. Initial populations of toluene and TCE degraders ranged from 0.2 x 10(3) to 4 x 10(3) cells per g of soil and increased by more than 4 orders of magnitude after the addition of 20 micrograms of toluene and 1 microgram of TCE per ml of soil solution. The numbers of TCE and toluene degraders and the percent removal of TCE increased with an increase in initial toluene concentration. As the initial TCE concentration was increased from 1 to 20 micrograms/ml, the numbers of toluene and TCE degraders and the rate of toluene degradation decreased, and no TCE degradation occurred. No toluene or TCE degradation occurred at a TCE concentration of 50 micrograms/ml.

Biodegradation, Environmental↗

PubMed2002

Effects of toluene exposure on signal transduction: toluene reduced the signaling via stimulation of human muscarinic acetylcholine receptor m2 subtypes in CHO cells.

The organic solvent toluene is used widely in industry and is toxic to the central nervous system (CNS). To clarify the mechanisms of CNS toxicity following toluene exposure, especially with respect to the G protein-coupling of receptors, we determined the effects of toluene on the activation of Gi by stimulating human muscarinic acetylcholine receptor m2 subtypes (hm2 receptors) expressed in Chinese hamster ovary (CHO) cells. We first examined whether toluene affects the inhibition of adenylyl cyclase by Gi. The attenuation of forskolin-stimulated cAMP formation by the stimulation of hm2 receptors was reduced in a medium containing toluene. Next, we determined the effects of toluene on carbamylcholine-stimulated [35S]GTPgammaS binding using membrane fractions of CHO cell expressing hm2 receptors. Carbamylcholine-stimulated [35S]GTPgammaS binding activity was markedly reduced when assayed using reaction buffers containing toluene. However, carbamylcholine-stimulated [35S]GTPgammaS binding activity was essentially unchanged following pretreatment of the cells with a toluene-saturated medium prior to membrane isolation. Toluene pretreatment and the toluene itself did not alter the characteristics of the binding of carbamylcholine and [3H]N-methylscopolamine to hm2 receptors. On the contrary of the effect of toluene for [35S]GTPgammaS binding, the effect of toluene for attenuation of forskolin-stimulated cAMP formation by the stimulation of hm2 receptors was irreversible. These observations indicate that toluene acts as an inhibitor of the signal transduction via hm2 receptor stimulation in CHO cells, and at least two mechanisms exist in the inhibition mechanisms by toluene.

Animals↗

PubMed1991

Anaerobic degradation of toluene in denitrifying Pseudomonas sp.: indication for toluene methylhydroxylation and benzoyl-CoA as central aromatic intermediate.

The anaerobic degradation of toluene has been studied with whole cells and by measuring enzyme activities. Cultures of Pseudomonas strain K 172 were grown in mineral medium up to a cell density of 0.5 g of dry cells per liter in fed-batch culture with toluene and nitrate as the sole carbon and energy sources. A molar growth yield of 57 g of cell dry matter formed per mol toluene totally consumed was determined. The mean generation time was 24 h. The redox balance between toluene consumed (oxidation and cell material synthesis) and nitrate consumed (reduction to nitrogen gas and assimilation as NH3) was 77% of expectation if toluene was completely oxidized; this indicated that the major amount of toluene was mineralized to CO2. It was tested whether the initial reaction in anaerobic toluene degradation was a carboxylation or a dehydrogenation (anaerobic hydroxylation); the hypothetical carboxylated or hydroxylated intermediates were tested with whole cells applying the method of simultaneous adaptation; cells pregrown on toluene degraded benzyl alcohol, benzaldehyde, and benzoic acid without lag, 4-hydroxybenzoate and p-cresol with a 90 min lag phase, and phenylacetate after a 200 min lag phase. The cells were not at all adapted to degrade 2-methylbenzoate, 4-methylbenzoate, o-cresol, and m-cresol, nor did these compounds support growth within a few days after inoculation with cells grown on toluene. In extracts of cells anaerobically grown on toluene, benzyl alcohol dehydrogenase, benzaldehyde dehydrogenase, and benzoyl-CoA synthetase (AMP forming) activities were present. The data (1) conclusively show anaerobic growth of a pure culture on toluene; (2) suggest that toluene is anaerobically degraded via benzoyl-CoA; (3) imply that water functions as the source of the hydroxyl group in a toluene methylhydroxylase reaction.

Acyl Coenzyme A↗

PubMed1999

Composition of toluene-degrading microbial communities from soil at different concentrations of toluene.

Toluene-degrading bacteria were isolated from hydrocarbon-contaminated soil by incubating liquid enrichment cultures and agar plate cultures in desiccators in which the vapor pressure of toluene was controlled by dilution with vacuum pump oil. Incubation in desiccators equilibrated with either 100, 10, or 1% (wt/wt) toluene in vacuum pump oil and testing for genomic cross-hybridization resulted in four genomically distinct strains (standards) capable of growth on toluene (strains Cstd1, Cstd2, Cstd5, and Cstd7). The optimal toluene concentrations for growth of these standards on plating media differed considerably. Cstd1 grew best in an atmosphere equilibrated with 0.1% (wt/wt) toluene, but Cstd5 failed to grow in this atmosphere. Conversely, Cstd5 grew well in the presence of 10% (wt/wt) toluene, which inhibited growth of Cstd1. 16S ribosomal DNA sequencing and cross-hybridization analysis indicated that both Cstd1 and Cstd5 are members of the genus Pseudomonas. An analysis of the microbial communities in soil samples that were incubated with 10% (wt/wt) toluene with reverse sample genome probing indicated that Pseudomonas strain Cstd5 was the dominant community member. However, incubation of soil samples with 0.1% (wt/wt) toluene resulted in a community that was dominated by Pseudomonas strain Q7, a toluene degrader that has been described previously (Y. Shen, L. G. Stehmeier, and G. Voordouw, Appl. Environ. Microbiol. 64:637-645, 1998). Q7 was not able to grow by itself in an atmosphere equilibrated with 0.1% (wt/wt) toluene but grew efficiently in coculture with Cstd1, suggesting that toluene or metabolic derivatives of toluene were transferred from Cstd1 to Q7.

Bacteria↗

PubMed2001

Multicenter field trial on possible health effects of toluene. I. Toluene body burdens in workers of the rotogravure industry.

Ambient air toluene concentrations as well as corresponding individual blood toluene levels were measured under conditions of a field trial, as basis for a correlation with possible acute effects. While the results of various psycho-physiological and medical evaluations after acute (Neubert et al., 2001) and long-term toluene exposure (Gericke et al., 2001) are published in accompanying papers, this publication deals with the exposure levels and body burdens characteristic of workers in the rotogravure industry in Germany at the time of the investigation (1993-1995). Besides providing some information on the exposure at various work-areas under occupational conditions, the correlation between a time-weighted average of the ambient air concentration with the corresponding blood toluene levels is analyzed. Limitations of such an attempt and possible pitfalls are discussed. In the largest field study so far performed on toluene exposure, 12 companies of the German rotogravure industry (and a total of 1528 volunteers) participated. Altogether, complete data sets, i.e. on both ambient air as well as blood toluene levels, were obtained from 1244 male and 124 female participants of the rotogravure industry with quite different degrees of toluene exposure. Rotogravure printers and their helpers were exposed to the highest toluene concentrations in ambient air. On the day of the evaluation, of 806 male volunteers within this group (of 1261 with verified exposure in air), 35 were exposed to a time-weighted average of 100 ppm (i.e. 375 mg/m(3)) or above, and 155 of the printers to concentrations between 50 and 100 ppm. Of the remaining 455 male participants of the rotogravure factories ('non-printers and helpers'), only three were exposed to toluene concentrations above 50 ppm. Only one of the 124 women working in the rotogravure factories was exposed to an average toluene concentrations above 100 mg/m(3) (i.e. 27 ppm). In 66 of the male volunteers toluene levels in blood of >850 microg/l were measured and 14 showed levels exceeding 1700 microg/l. When attempting to predict the resulting individual blood toluene levels from measurements of ambient air concentrations under field conditions, a considerable uncertainty is to be expected. We found a correlation coefficient of the regression curve of about 0.70, with numerous outliers (and a variation of the 12 factories between 0.52 and 0.88).

Adult↗

PubMed2000

Comparison between blood and urinary toluene as biomarkers of exposure to toluene.

OBJECTIVES: To compare blood toluene (TOL-B) and urinary toluene (TOL-U) as biomarkers of occupational exposure to toluene, and to set a suitable procedure for collection and handling of specimens. METHOD: An assay based on headspace solid-phase microextraction (SPME) was used both for the determination of toluene urine/air partition coefficient (lambdaurine/air) and for the biological monitoring of exposure to toluene in 31 workers (group A) and in 116 non-occupationally exposed subjects (group B). Environmental toluene (TOL-A) was sampled during the work shift (group A) or during the 24 h before specimen collection (group B). Blood and urine specimens were collected at the end of the shift (group A) or in the morning (group B) and toluene was measured. RESULTS: Toluene lambdaurine/air was 3.3 +/- 0.9. Based on the specimen/air partition coefficient, it was calculated that the vial in which the sample is collected had to be filled up to 85% of its volume with urine and 50% with blood in order to limit the loss of toluene in the air above the specimen to less than 5%. Environmental and biological monitoring of workers showed that the median personal exposure to toluene (TOL-A) during the work-shift was 80 mg/m3, the corresponding TOL-B was 82 microg/l and TOL-U was 13 microg/l. Personal exposure to toluene in environmentally exposed subjects was 0.05 mg/m3, TOL-B was 0.36 microg/l and TOL-U was 0.20 microg/l. A significant correlation (P < 0.05) was observed between TOL-B or TOL-U and TOL-A (Pearson's r = 0.782 and 0.754) in workers, but not in controls. A significant correlation was found between TOL-U and TOL-B both in workers and in controls (r = 0.845 and 0.681). CONCLUSION: The comparative evaluation of TOL-B and TOL-U showed that they can be considered to be equivalent biomarkers as regards their capacity to distinguish workers and controls and to correlate with exposure. However, considering that TOL-U does not require an invasive specimen collection, it appears to be a more convenient tool for the biological monitoring of exposure to toluene.

Adult↗

PubMed2000

A set of genes encoding a second toluene efflux system in Pseudomonas putida DOT-T1E is linked to the tod genes for toluene metabolism.

Sequence analysis in Pseudomonas putida DOT-T1E revealed a second toluene efflux system for toluene metabolism encoded by the ttgDEF genes, which are adjacent to the tod genes. The ttgDEF genes were expressed in response to the presence of aromatic hydrocarbons such as toluene and styrene in the culture medium. To characterize the contribution of the TtgDEF system to toluene tolerance in P. putida, site-directed mutagenesis was used to knock out the gene in the wild-type DOT-T1E strain and in a mutant derivative, DOT-T1E-18. This mutant carried a Tn5 insertion in the ttgABC gene cluster, which encodes a toluene efflux pump that is synthesized constitutively. For site-directed mutagenesis, a cassette to knock out the ttgD gene and encoding resistance to tellurite was constructed in vitro and transferred to the corresponding host chromosome via the suicide plasmid pKNG101. Successful replacement of the wild-type sequences with the mutant cassette was confirmed by Southern hybridization. A single ttgD mutant, DOT-T1E-1, and a double mutant with knock outs in the ttgD and ttgA genes, DOT-T1E-82, were obtained and characterized for toluene tolerance. This was assayed by the sudden addition of toluene (0.3% [vol/vol]) to the liquid culture medium of cells growing on Luria-Bertani (LB) medium (noninduced) or on LB medium with toluene supplied via the gas phase (induced). Induced cells of the single ttgD mutant were more sensitive to sudden toluene shock than were the wild-type cells; however, noninduced wild-type and ttgD mutant cells were equally tolerant to toluene shock. Noninduced cells of the double DOT-T1E-82 mutant did not survive upon sudden toluene shock; however, they still remained viable upon sudden toluene shock if they had been previously induced. These results are discussed in the context of the use of multiple efflux pumps involved in solvent tolerance in P. putida DOT-T1E.

Amino Acid Sequence↗

PubMed1998

High-pressure liquid chromatographic determination of toluene in urine as a marker of occupational exposure to toluene.

OBJECTIVE: To establish a convenient method by high-pressure liquid chromatography (HPLC) to measure toluene in urine as a marker of occupational exposure to toluene. METHODS: As soon after sampling as possible, 1 ml of urine was mixed with an equal volume of acetonitrile in a 2.2-ml HPLC glass bottle, and the bottle was tightly sealed and stored at 4 degrees C. Immediately before HPLC determination, 100 microl methanol was added to the mixture to prevent confounding effects of glycosuria, and the bottle was spun to remove any suspended matter. An aliquot of the supernate was introduced into the HPLC system and analyzed on a PRODIGY column, with an acetonitrile - perchloric acid phosphoric acid - water mixture serving as the mobile phase. The effluent was monitored at 191 nm. RESULTS: The method can measure toluene in urine every 20 min, the detection limit was 2 microg/l, the coefficient of variation was less than 5%, and the recovery rate was 100%. No significant reduction in toluene concentration was observed for 1 week after storage at 4 degrees C. When the method was applied to end-of-shift urine samples from 13 male workers exposed to toluene at 18-140 ppm and also to urine samples from 10 nonexposed male controls, toluene in urine was linearly related to toluene exposure concentration, with a regression line passing close to the origin. The correlation coefficient was as high as 0.97 (n=23). No toluene was detected in control urine samples. Calculations suggest that urinary toluene accounts for as little as less than 0.01% of the toluene absorbed via inhalation and that the absorbed toluene is converted almost quantitatively to hippuric acid and, by less than 0.1%, to o-cresol.

Adult↗

PubMed1984

Toluene levels in blood and brain of rats as a function of toluene level in inspired air.

The relationship of toluene concentration in blood and brain to the concentration of toluene in inspired air has not been explicitly studied. Sixty rats were exposed by inhalation to 50, 100, 500, or 1000 ppm toluene for 3 hr. Immediately following exposure, venous blood samples and whole brains were collected and assayed for toluene levels. For several empirical reasons, the natural logarithm (log) of toluene tissue levels were predicted in a linear model from log toluene levels in air. An additional 10 rats were exposed to 550 ppm toluene for 8 hr in order to verify that the 3-hr exposure was sufficient to produce near-asymptotic levels of toluene in blood and brain. Log brain toluene concentration was significantly higher than log blood concentration by an additive constant. The ratio of brain to blood toluene level was estimated as 1.56/1. Three- and eight-hour exposure results did not differ, thus indicating that these results would hold for toluene exposures of 3 hr or greater.

Animals↗

PubMed1996

Evidence that anaerobic oxidation of toluene in the denitrifying bacterium Thauera aromatica is initiated by formation of benzylsuccinate from toluene and fumarate.

Toluene is degraded anoxically to CO2 by the denitrifying bacterium Thauera aromatica. Toluene first becomes oxidized to benzoyl-CoA by O2-independent reactions. Benzoyl-CoA is then reduced to non-aromatic products by benzoyl-CoA reductase. We set out to study the reactions employed for the initial activation of toluene and its oxidation to the level of benzoate. Evidence is provided for a novel way of toluene degradation based on experiments with cell-free extracts and with whole toluene-grown cells: Cell-free extracts oxidized [14C]toluene to [14C]benzoyl-CoA via several radioactive intermediates. This reaction was strictly dependent on the presence of fumarate, coenzyme A and nitrate as electron acceptor; acetyl-CoA and ATP were not necessary for the reaction. The first product formed in vitro was benzylsuccinate; (2H8)toluene was converted to (2H7)benzylsuccinate. Formation of benzylsuccinate from toluene was independent of coenzyme A and nitrate, but it required the presence of fumarate. Other tricarboxylic acid cycle intermediates were converted to fumarate in cell extracts and therefore could partially substitute for fumarate. [14C]Benzylsuccinate was oxidized further to [14C]benzoyl-CoA and [14C]benzoate in cell extracts if coenzyme A and nitrate were present. No benzyl alcohol and benzaldehyde and no phenylpropionate could be detected as intermediates. In isotope trapping experiments with cell suspensions, two intermediates from [14C]toluene were detected, benzoate and benzylsuccinate. This corroborates the sequence of reactions deduced from in vitro experiments. A hypothetical degradation pathway for the anaerobic oxidation of toluene to benzoyl-CoA via an initial addition of fumarate to the methyl group of toluene and following beta-oxidation of the benzylsuccinate formed is suggested.

Acyl Coenzyme A↗

PubMed1998

S-p-toluylmercapturic acid in the urine of workers exposed to toluene: a new biomarker for toluene exposure.

A mercapturic acid attached to the aromatic ring of toluene was for the first time detected in human urine as a metabolite of toluene. Since the metabolism of toluene is usually considered to take place at the side-chain, this gives, besides the biosynthesis of cresols, a further hint of a metabolic conversion of the aromatic system. We examined a group of 33 workers occupationally exposed to toluene, determining the concentrations of toluene in ambient air and in whole blood, o-cresol and hippuric acid in urine and p-toluylmercapturic acid (p-TMA) in urine. All blood and urine samples were collected post-shift. The renal excretion of S-p-toluylmercapturic acid showed highly significant correlations with established parameters of a biological monitoring of toluene. The median ambient air concentration was 63 ppm, ranging from 13 to 151 ppm, the median concentration of toluene in whole blood was 804 microg/l, corresponding to median urinary concentrations for o-cresol of 2.3 mg/l, hippuric acid of 2.3 g/l and p-TMA of 20.4 microg/l. p-TMA was not detectable in urine samples of a control group of 10 non-exposed persons. Both the German Biological Tolerance Values (BAT-values) for toluene in blood (1000 microg/l) and o-cresol in urine (3 mg/l) correspond to a mean p-TMA elimination of approximately 50 microg/l, and thus are in agreement with each other. According to our results p-TMA reflects internal toluene exposure diagnostically sensitive and specifical. With the developed analytical procedure we determined a median benzylmercapturic acid (BMA) concentration of 190 microg/l in the urine samples of the toluene exposed persons. We also determined a median BMA concentration of 30 microg/l in the control samples of non-exposed persons. However, these results are preliminary and require further confirmation as the reliability of the method was determined only for p-TMA.

Acetylcysteine↗

PubMed1998

Inhibition of rat lung mixed-function oxidase activity following repeated low-level toluene inhalation: possible role of toluene metabolites.

Toluene is a commonly used solvent that has been shown to alter mixed-function oxidase (MFO) activity, in an organ- and isozyme-specific pattern, following intraperitoneal administration. The purpose of this study was to determine whether similar changes occurred following repeated, low-level inhalation exposure, and to investigate the role of toluene metabolites in these alterations. Exposure to 375 ppm toluene, 6 h/d for up to 5 d, resulted in significant inhibition of the activity of pulmonary arylhydrocarbon hydroxylase (AHH), cytochrome P-4502B1 (CYP2B1), and CYP4B1, but not CYP1A1. After exposure to lower toluene levels (125 ppm, 6 h/d, 3 d), the activities of lung AHH, CYP2B1, and CYP4B1 were also significantly decreased, but in a dose-related manner. MFO activity was not consistently altered in liver. Control pulmonary or liver microsomes were incubated with various concentrations (0.01-10 mM) of toluene or its metabolites and CYP2B1, CYP1A1, and/or CYP4B1 activities were subsequently determined. Benzaldehyde produced a significant dose-related inhibition in the activity of all three lung P-450s examined (IC50 10(-3) M). Toluene was found to be a more potent inhibitor of lung CYP2B1 and CYP1A1 (IC50, 10(-4) M) than benzaldehyde, but neither toluene nor benzyl alcohol was an effective inhibitor of lung CYP4B1. Toluene and its metabolites were weaker inhibitors of CYP1A1 than of CYP2B1. For CYP2B1 and CYP1A1, the order of inhibitory potency was toluene > benzaldehyde > benzyl alcohol and suggests that both the parent molecule and its metabolites may act in concert to inhibit catalytic activity of these cytochromes. The MFO inhibition seen after repeated low-level toluene inhalation exposure could result in altered metabolic profiles of other xenobiotics in an organ-specific fashion.

Administration, Inhalation↗

PubMed1995

Blood toluene as a biological index of environmental toluene exposure in the "normal" population and in occupationally exposed workers immediately after exposure and 16 hours later.

Blood toluene was measured in a group of 100 workers occupationally exposed to a mean 8-h environmental toluene concentration of 128 micrograms/l (34 ppm), and in a group of 269 "normal" subjects without occupational exposure to toluene. The mean blood toluene of the workers at the end of the shift and the following morning, after 16 h, was 457 and 38 micrograms/l, respectively. The normal subjects had a blood toluene level of 1.1 micrograms/l. On the basis of the highly significant correlation between blood toluene and occupational exposure, it can be calculated that environmental toluene exposure of 188 and 377 micrograms/l (50 and 100 ppm) gives end-of-shift blood toluene levels of 690 and 1390 micrograms/l, respectively. The corresponding blood toluene levels on the following morning are 50 and 100 micrograms/l, respectively.

Environmental Exposure↗

PubMed1993

[Experimental studies of postmortem diffusion of toluene in blood, brain, muscle and fat of rats exposed to toluene vapor].

This report describes the postmortem diffusion of toluene in blood, brain, muscle and fat of rats exposed to toluene vapor. After exposure to toluene vapor (4,000 ppm) for 15 and 60 min, rats were killed by CO2 exposure and left for 12 and 24 hours in a fresh air. Toluene concentrations in blood, brain, muscle and fat were determined by head space gas chromatography. Postmortem decrease of toluene concentration in blood and increase of that in fat were observed with postmortem interval in both exposure conditions. But an extremely larger postmortem changes in the short exposure than those in the long exposure were observed. These are due to the facts that the value of fat/blood toluene concentration ratio at the time of death in the short exposure (3.3) was extremely smaller than that in the long exposure (10.5). Postmortem increase in muscle was also observed slightly. Postmortem concentrations in brain in both exposure intervals were relatively constant during these experiments. This postmortem stability is attributable to its anatomical features. These results suggest that brain toluene concentration at the autopsy is useful for the estimation of blood toluene concentration at the time of death and by comparison between toluene concentration in blood and that in brain it may be possible to presume the circumstances of death.

Adipose Tissue↗

PubMed1999

Estimating amounts of toluene inhaled by workers with protective mask using biological indicators of toluene.

Personal air samplers were attached to workers wearing protective masks to determine the levels of toluene vapor in the breathing zone. Concentrations of toluene in exhaled air, blood and urine; and hippuric acid and o-cresol concentrations in the urine of the workers were determined. Subsequently, toluene concentrations in the air inhaled by workers with and without gas masks were estimated by single and multiple regression equations. Analysis of single regression equations revealed that, compared with toluene concentrations in air, masks decreased the concentrations of the four biological exposure indicators: toluene in exhaled air, urinary toluene, urinary hippuric acid and urinary o-cresol by about 29% in average. Analysis by multiple regression equations showed a decrease of 38% in four biological indicators. Since average exposure to toluene in the shop was relatively low, the workers wore the masks only during high concentrations of toluene; they were, however, exposed to direct inhalation when the masks were removed in lower concentrations.

Adult↗

PubMed2000

Toluene-degrading bacteria are chemotactic towards the environmental pollutants benzene, toluene, and trichloroethylene.

The bioremediation of polluted groundwater and toxic waste sites requires that bacteria come into close physical contact with pollutants. This can be accomplished by chemotaxis. Five motile strains of bacteria that use five different pathways to degrade toluene were tested for their ability to detect and swim towards this pollutant. Three of the five strains (Pseudomonas putida F1, Ralstonia pickettii PKO1, and Burkholderia cepacia G4) were attracted to toluene. In each case, the response was dependent on induction by growth with toluene. Pseudomonas mendocina KR1 and P. putida PaW15 did not show a convincing response. The chemotactic responses of P. putida F1 to a variety of toxic aromatic hydrocarbons and chlorinated aliphatic compounds were examined. Compounds that are growth substrates for P. putida F1, including benzene and ethylbenzene, were chemoattractants. P. putida F1 was also attracted to trichloroethylene (TCE), which is not a growth substrate but is dechlorinated and detoxified by P. putida F1. Mutant strains of P. putida F1 that do not oxidize toluene were attracted to toluene, indicating that toluene itself and not a metabolite was the compound detected. The two-component response regulator pair TodS and TodT, which control expression of the toluene degradation genes in P. putida F1, were required for the response. This demonstration that soil bacteria can sense and swim towards the toxic compounds toluene, benzene, TCE, and related chemicals suggests that the introduction of chemotactic bacteria into selected polluted sites may accelerate bioremediation processes.

Alkanes↗

PubMed1998

Isolation and characterization of toluene-sensitive mutants from the toluene-resistant bacterium Pseudomonas putida GM73.

To understand the mechanism underlying toluene resistance of a toluene-tolerant bacterium, Pseudomonas putida GM73, we carried out Tn5 mutagenesis and isolated eight toluene-sensitive mutants. None of the mutants grew in the presence of 20% (vol/vol) toluene in growth medium but exhibited differential sensitivity to toluene. When wild-type cells were treated with toluene (1% [vol/vol]) for 5 min, about 2% of the cells could form colonies. In the mutants Ttg1, Ttg2, Ttg3, and Ttg8, the same treatment killed more than 99.9999% of cells (survival rate, <10(-6)). In Ttg4, Ttg5, Ttg6, and Ttg7, about 0.02% of cells formed colonies. We cloned the Tn5-inserted genes, and the DNA sequence flanking Tn5 was determined. From comparison with a sequence database, putative protein products encoded by ttg genes were identified as follows. Ttg1 and Ttg2 are ATP binding cassette (ABC) transporter homologs; Ttg3 is a periplasmic linker protein of a toluene efflux pump; both Ttg4 and Ttg7 are pyruvate dehydrogenase; Ttg5 is a dihydrolipoamide acetyltransferase; and Ttg7 is the negative regulator of the phosphate regulon. The sequences deduced from ttg8 did not show a significant similarity to any DNA or proteins in sequence databases. Characterization of these mutants and identification of mutant genes suggested that active efflux mechanism and efficient repair of damaged membranes were important in toluene resistance.

Amino Acid Sequence↗

PubMed1990

[The distribution of toluene in the brain and its effects on the brain catecholamines in acute toluene poisoning].

The regional distribution of toluene in the brain and its effects on the brain catecholamine levels in rats is reported. Separate sets of rats were exposed to the toluene via inhalation, at 1,500 ppm and at 10,000 ppm respectively, and via an ingestion (400 mg/kg). Given these three exposure conditions, the values of brain/blood toluene ratios were found to be the highest in the brain stem areas (2.85-3.22) such as the pons and medulla oblongata, in the middle range in the midbrain, the thalamus, the caudate-putamen, the hypothalamus and the cerebellum (1.77-2.12), and in the lowest ranges in the olfactory bulb, the hippocampus and the cerebral cortex (1.22-1.64). The values of the partition coefficient of toluene in the brain regions and in the blood of rats examined in vitro were also the highest in the brain stem and the lowest in the cerebral cortex. The highest values of brain/blood toluene and partition coefficients of toluene in the brain regions and blood were obtained in the lipid-rich regions. These results suggest that toluene, which has a high lipid solubility and no protein binding capability, distributes according to lipid contents of the brain. The inhalation of toluene (1,500 ppm and 10,000 ppm) caused decreases in the noradrenaline (NA) levels in the dorsal part of rat pons, rich in locus coeruleus, and in the dopamine (DA) levels in the hypothalamus and ventral part of the rat midbrain, rich in substantia nigra.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗