Microbial transformation of quinoline by a Pseudomonas sp.

A Pseudomonas sp. isolated from sewage by enrichment culture on quinoline metabolized this substrate by a novel pathway involving 8-hydroxycoumarin. During early growth of the organism on quinoline, 2-hydroxyquinoline accumulated as the intermediate; 8-hydroxycoumarin accumulated as the major metabolite on further incubation. 2,8-Dihydroxyquinoline and 2,3-dihydroxyphenylpropionic acid were identified as the other intermediates. Inhibition of quinoline metabolism by 1 mM sodium arsenite led to the accumulation of pyruvate, whereas inhibition by 5 mM arsenite resulted in the accumulation of 2-hydroxyquinoline as the major metabolite and 2,8-dihydroxyquinoline as the minor metabolite. Coumarin was not utilized as a growth substrate by this bacterium, but quinoline-grown cells converted it to 2-hydroxyphenylpropionic acid, which was not further metabolized. Quinoline, 2-hydroxyquinoline, 8-hydroxycoumarin, and 2,3-dihydroxyphenylpropionic acid were rapidly oxidized by quinoline-adapted cells, whereas 2,8-dihydroxyquinoline was oxidized very slowly. Quinoline catabolism in this Pseudomonas sp. is therefore initiated by hydroxylation(s) of the molecule followed by cleavage of the pyridine ring to yield 8-hydroxycoumarin, which is further metabolized via 2,3-dihydroxyphenylpropionic acid.     

Microbiological degradation of quinoline by Pseudomonas stutzeri: the coumarin pathway of quinoline catabolism

A Gram-negative, oxidase positive, polar flagellated rod, characterised as Pseudomonas stutzeri, has been isolated from sewage by enrichment culture on quinoline. The organism utilizes quinoline as the sole source of carbon, nitrogen and energy, and liberates UV absorbing and phenolic metabolites during its growth on quinoline. 2-Hydroxyquinoline, 2,8-dihydroxyquinoline, 8-hydroxycoumarin and 2,3-dihydroxyphenylpropionic acid have been isolated as the transformation products of quinoline by this bacterium. Quinoline, 2-hydroxyquinoline, and 8-hydroxycoumarin were rapidly oxidised by quinoline-adapted cells; 2,3-dihydroxyphenylpropionic acid oxidation was also demonstrated by Warburg respirometry but 2,8-dihydroxyquinoline was not oxidised. A pathway for quinoline catabolism by P. stutzeri and the probable mechanisms for formation of 8-hydroxycoumarin are suggested.     

Microbial metabolism of quinoline and related compounds. II. Degradation of quinoline by Pseudomonas fluorescens 3, Pseudomonas putida 86 and Rhodococcus spec. B1

Quinoline catabolism was investigated with different bacterial strains, able to use quinoline as sole source of carbon, nitrogen and energy. Some degradation products of quinoline were isolated from the culture fluids and identified. With Pseudomonas fluorescens and Pseudomonas putida we found 2-oxo-1,2-dihydroquinoline, 8-hydroxy-2-oxo-1,2-dihydroquinoline, 8-hydroxycoumarin and 2,3-dihydroxyphenylpropionic acid as intermediates. With a Rhodococcus strain 2-oxo-1,2-dihydroquinoline, 6-hydroxy-2-oxo-1,2-dihydroquinoline, a red meta-cleavage product and a blue fluorescent compound were isolated. The red compound was identified as 5-hydroxy-6-(3-carboxy-3-oxopropenyl)-1H-2-pyridone. From this the blue fluorescent azacoumarin 2H-pyrano-2-one-[3,2b]-5H-6-pyridone is formed by chemical decomposition. Therefore it can be considered a by-product of quinoline-degradation in Rhodococcus spec. With the present results two different degradation pathways for quinoline in different microorganisms are proposed.     

Quinoline biodegradation and its nitrogen transformation pathway by a <Emphasis Type="Italic">Pseudomonas</Emphasis> sp. strain

A Pseudomonas sp. strain, which can utilize quinoline as its sole carbon, nitrogen and energy source, was isolated from activated sludge in a coking wastewater treatment plant. Quinoline can be degraded via the 8-hydroxycoumarin pathway. We quantified the first two organic intermediates of the biodegradation, 2-hydroxyquinoline and 2,8-dihydroxyquinoline. We tracked the transformation of the nitrogen in quinoline in two media containing different C/N ratios. At least 40.4% of the nitrogen was finally transformed into ammonium when quinoline was the sole C and N source. But addition of an external carbon source like glucose promoted the transformation of N from NH₃ into NO₃ ⁻, NO₂ ⁻, and then to N₂. The product analysis and gene characteristics indicated that the isolate accomplished heterotrophic nitrification and aerobic denitrification simultaneously. The study also demonstrated that quinoline and its metabolic products can be eliminated if the C/N ratio is properly controlled in the treatment of quinoline-containing wastewater.     

Aerobic biodegradation characteristics and metabolic products of quinoline by a Pseudomonas strain

A bacterial strain, BW003, which utilized quinoline as its sole C, N and energy source, was isolated and identified as Pseudomonas sp. BW003 degraded 192–911 mg/l quinoline within 3–8 h with removal rates ranging from 96% to 98%. The optimum conditions for the degradation were 30 °C and pH 8. In the process of biodegradation, at least 43% of quinoline was transformed into 2-hydroxyquinoline, then 0.69% of 2-hydroxyquinoline was transformed into 2,8-dihydroxyquinoline, and then, presumably, into 8-hydroxycoumarin. Meanwhile, at least 48% of the nitrogen in quinoline was directly transformed into ammonia-N. An extra carbon source enhanced the nitrogen transformation from ammonia-N. Further experiments showed that, besides cell synthesis, BW003 transformed less than 6% of ammonia-N into nitrate through heterotrophic nitrification. In addition, BW003 contained a large plasmid, which may be involved in quinoline metabolism. The study indicates that quinoline and its metabolic products can be eliminated from wastewater by controlling the C/N ratio using BW003 as the bioaugmentation inoculum.     

Xenobiotic reductase A in the degradation of quinoline by Pseudomonas putida 86: physiological function, structure and mechanism of 8-hydroxycoumarin reduction

A continuous evolutionary pressure of the biotic and abiotic world has led to the development of a diversity of microbial pathways to degrade and biomineralize aromatic and heteroaromatic compounds. The heterogeneity of compounds metabolized by bacteria like Pseudomonas putida indicates the large variety of enzymes necessary to catalyse the required reactions. Quinoline, a N-heterocyclic aromatic compound, can be degraded by microbes along different pathways. For P. putida 86 quinoline degradation by the 8-hydroxycoumarin pathway has been described and several intermediates were identified. To select enzymes catalysing the later stages of the 8-hydroxycoumarin pathway P. putida 86 was grown with quinoline. The FMN-containing enzyme xenobiotic reductase A (XenA) was isolated and analysed for its reactivity with intermediates of the 8-hydroxycoumarin pathway. XenA catalyses the NADPH-dependent reduction of 8-hydroxycoumarin and coumarin to produce 8-hydroxy-3,4-dihydrocoumarin and 3,4-dihydrocoumarin, respectively. Crystallographic analysis of XenA alone and in complex with the two substrates revealed insights into the mechanism. XenA shows a dimeric arrangement of two (beta/alpha)(8) barrel domains each binding one FMN cofactor. High resolution crystal structures of complexes with 8-hydroxycoumarin and coumarin show different modes of binding for these molecules in the active site. While coumarin is ideally positioned for hydride transfer from N-5 of the isoalloxazine ring to C-4 of coumarin, 8-hydroxycoumarin forms a non-productive complex with oxidised XenA. Orientation of 8-hydroxycoumarin in the active site appears to be dependent on the electronic state of the flavin. We postulate that XenA catalyses the last step of the 8-hydroxycoumarin pathway before the heterocyclic ring is hydrolysed to yield 3-(2,3-dihydroxyphenyl)-propionic acid. As XenA is also found in P. putida strains unable to degrade quinoline, it appears to have more than one physiological function and is an example of how enzymes with low substrate specificity can help to explain the variety of degradation pathways possible.     

Microbial metabolism of quinoline and related compounds. III. Degradation of 3-chloroquinoline-8-carboxylic acid by Pseudomonas spec. EK III

Bacteria have been isolated with the ability to use 3-chloroquinoline-8-carboxylic acid as sole source of carbon and energy. According to their physiological properties, these bacteria have been classified as Pseudomonas spec. Two metabolites of the degradation pathway have been isolated and identified. The first metabolite was 3-(3-carboxy-3-oxopropenyl)-2-hydroxy-5-chloropyridine, the meta-cleavage product of 3-chloro-7,8-dihydroxyquinoline. The second metabolite, 5-chloro-2-hydroxynicotinic acid, was not further metabolized by this organisms.     

Transformation of 2-chloroquinoline to 2-chloro-cis-7,8-dihydro-7,8-dihydroxyquinoline by quinoline-grown resting cells of Pseudomonas putida 86

Abstract Resting cells of Pseudononas putida strain 86 were grown on quinoline transformed 2-chloroquinoline to 2-chloro- cis -7,8-dihydro-7,8-dihydroxyquinoline which was not converted further. 7,8-Dioxygenating activity was present when the enzymes of quinoline catabolism were induced. Quinoline-grown cells of strain 86 treated simultaneously with 2-chloroquinoline and D-(-)- threo -chloramphenicol to prevent protein biosynthesis also formed the cis -7,8-dihydrodiol of 2-chloroquinoline. Succinate-grown resting cells did not oxidize 2-chloroquinoline. Acid-catalyzed decomposition of 2-chloro- cis -7,8-dihydro-7,8-dihydroxyquinoline predominantly yielded 2-chloro-8-hydroxyquinoline. By analogy, accumulation of the putative dead-end metabolite 1 H -8-hydroxy-2-oxoquinoline during growth of P. putida 86 on quinoline is suggested to likewise result from dehydration of the 7,8-dihydrodiol of 1 H -2-oxoquinoline.     

Biotransformation of quinoline and methylquinolines in anoxic freshwater sediment

Quinoline (Q) and some isomers of methylquinoline (MQ) were transformed to hydroxylated products in freshwater sediment slurries incubated under methanogenic conditions at 25 °C. Methylquinoline transformation was not affected by a methyl group on the C-3 or C-4 carbon atom of the pyridine ring; 2-MQ, however, was not transformed. All isomers of dimethylquinoline (DMQ) tested (2,4-, 2,6-, 2,7-, and 2,8-DMQ) with a methyl group at the number 2 carbon also persisted in sediments after anaerobic incubation for one year at 25 °C.In most experiments, quinoline initially was transformed to 2-hydroxyquinoline (2-OH-Q), which was further metabolized to unidentified products. A second product, 4-CH₃-2-OH-Q, was detected in some experiments. This product accumulated and was not further transformed. 6-, 7-, and 8-Methylquinoline (6-, 7-, 8-MQ) were hydroxylated to form the respective 2-OH-MQ products. These hydroxylated products accumulated and were not further transformed. Hydroxylation of Q and 6-, 7- and 8-MQ at the 2-carbon position was confirmed by GC/FTIR and GC/MS analyses. The transformations of Q and MQs were pH dependent with an optimal pH of 7–8.The results of this study suggest that two pathways may exist for the anaerobic transformation of quinoline; one pathway leads to the formation of a hydroxylated intermediate and the other to a methylated and hydroxylated intermediate. In addition, our results suggest that a methyl substituent on the number 2 carbon inhibits the anaerobic transformation of quinoline derivatives.Abbreviations GC gas chromatography - GC/FTIR gas chromatography/Fourier transform infrared spectrometry - GC/MS gas chromatography/mass spectrometry - HPLC high performance liquid chromatography - MQ methylquinoline - Q quinoline     

Molybdenum-dependent degradation of quinoline by Pseudomonas putida Chin IK and other aerobic bacteria

Eighteen different aerobic bacteria were isolated which utilized quinoline as sole source of carbon, nitrogen, and energy. Attempts were unsuccessful at isolating anaerobic quinoline-degrading bacteria. The optimal concentration of quinoline for growth was in the range of 2.5 to 5 mM. Some organisms excreted 2-hydroxyquinoline as the first intermediate. Hydroxylation of quinoline was catalyzed by a dehydrogenase which was induced in the presence of quinoline or 2-hydroxyquinoline. Quinoline dehydrogenase activity was dependent on the availability of molybdate in the growth medium. Growth on quinoline was inhibited by tungstate, an antagonist of molybdate. Partially purified quinoline dehydrogenase from Pseudomonas putida Chin IK indicated the presence of flavin, iron-sulfur centers, and molybdenum-binding pterin. M _r of quinoline dehydrogenase was about 300 kDa in all isolates investigated.Abbreviations APS ammonium peroxodisulfate - DCPIP 2,6-dichlorophenol-indophenol - EEO electroendosmosis - MTT thiazolyl blue - PES phenazine ethosulfate - TEMED N,N,N,N-tetramethyl-ethylenediamine     

Degradation of I-Naphthol by a Soil Pseudomonad

A soil Pseudomonas sp. grew with 1-naphthol as sole organic carbon source and produced a 3,4-dihydro-dihydroxy-1(2H)-naphthalenone as the main early intermediary metabolite. Washed 1-naphthol-grown organisms oxidized naphthalene, 1- or 2-naphthol, salicylic acid and, to some extent, 2,3-dihydroxybenzoic acid.     

Degradation of 3-phenylbutyric acid by Pseudomonas sp.

Pseudomonas sp. isolated by selective culture with 3-phenylbutyrate (3-PB) as the sole carbon source metabolized the compound through two different pathways by initial oxidation of the benzene ring and by initial oxidation of the side chain. During early exponential growth, a catechol substance identified as 3-(2,3-dihydroxyphenyl)butyrate (2,3-DHPB) and its meta-cleavage product 2-hydroxy-7-methyl-6-oxononadioic-2,4-dienoic acid were produced. These products disappeared during late exponential growth, and considerable amounts of 2,3-DHPB reacted to form brownish polymeric substances. The catechol intermediate 2,3-DHPB could not be isolated, but cell-free extracts were able only to oxidize 3-(2,3-dihydroxyphenyl)propionate of all dihydroxy aromatic acids tested. Moreover, a reaction product caused by dehydration of 2,3-DHPB on silica gel was isolated and identified by spectral analysis as (--)-8-hydroxy-4-methyl-3,4-dihydrocoumarin. 3-Phenylpropionate and a hydroxycinnamate were found in supernatants of cultures grown on 3-PB; phenylacetate and benzoate were found in supernatants of cultures grown on 3-phenylpropionate; and phenylacetate was found in cultures grown on cinnamate. Cells grown on 3-PB rapidly oxidized 3-phenylpropionate, cinnamate, catechol, and 3-(2,3-dihydroxyphenyl)propionate, whereas 2-phenylpropionate, 2,3-dihydroxycinnamate, benzoate, phenylacetate, and salicylate were oxidized at much slower rates. Phenylsuccinate was not utilized for growth nor was it oxidized by washed cell suspensions grown on 3-PB. However, dual axenic cultures of Pseudomonas acidovorans and Klebsiella pneumoniae, which could not grow on phenylsuccinate alone, could grow syntrophically and produced the same metabolites found during catabolism of 3-PB by Pseudomonas sp. Washed cell suspensions of dual axenic cultures also immediately oxidized phenylsuccinate, 3-phenylpropionate, cinnamate, phenylacetate, and benzoate.     

Metabolism of dibenzothiophene by a Beijerinckia species.

Beijerinckia B8/36 when grown with succinate in the presence of dibenzothiophene, accumulated (+)-cis-1,2-dihydroxy-1,2-dihydrodibenzothiophene and dibenzothiophene-5-oxide in the culture medium. Each metabolite was isolated in crystalline form and characterized by a variety of chemical techniques, cis-Naphthalene dihydrodiol dehydrogenase, isolated from Pseudomonas putida, oxidized (+)-cis-1,2-dihydroxy-1,2-dihydrodibenzothiophene to a compound that was tentatively identified as 1,2-dihydroxydibenzothiophene. The same product was formed when crude cell extracts of the parent strain of Beijerinckia oxidized (+)-cis-1,2-dihydroxy-1,2-dihydrodibenzothiophene under anaerobic conditions. Further metabolism of 1,2-dihydroxydibenzothiophene by heat-treated cell extracts led to the formation of 4[2-(3-hydroxy)-thionaphthenyl]-2-oxo-3-butenoic acid. The latter compound was metabolized by crude cell extracts to 3-hydroxy-2-formylthionaphthene. Further degradation of this metabolite was not observed.     

Metabolism of dibenzothiophene by a Beijerinckia species

Beijerinckia B8/36 when grown with succinate in the presence of dibenzothiophene, accumulated (+)-cis-1,2-dihydroxy-1,2-dihydrodibenzothiophene and dibenzothiophene-5-oxide in the culture medium. Each metabolite was isolated in crystalline form and characterized by a variety of chemical techniques, cis-Naphthalene dihydrodiol dehydrogenase, isolated from Pseudomonas putida, oxidized (+)-cis-1,2-dihydroxy-1,2-dihydrodibenzothiophene to a compound that was tentatively identified as 1,2-dihydroxydibenzothiophene. The same product was formed when crude cell extracts of the parent strain of Beijerinckia oxidized (+)-cis-1,2-dihydroxy-1,2-dihydrodibenzothiophene under anaerobic conditions. Further metabolism of 1,2-dihydroxydibenzothiophene by heat-treated cell extracts led to the formation of 4[2-(3-hydroxy)-thionaphthenyl]-2-oxo-3-butenoic acid. The latter compound was metabolized by crude cell extracts to 3-hydroxy-2-formylthionaphthene. Further degradation of this metabolite was not observed.     

Microbial metabolism of quinoline and related compounds. IX. Degradation of 6-hydroxyquinoline and quinoline by Pseudomonas diminuta 31/1 Fa1 and Bacillus circulans 31/2 A1

Two strains, using 6-hydroxyquinoline as sole source of energy, carbon and nitrogen, have been isolated. These bacteria, designated 31/1 Fa1 and 31/2 A1, are also able to degrade quinoline. According to their physiological properties strain 31/1 Fa1 has been identified as Pseudomonas diminuta and strain 31/2 A1 as Bacillus circulans. 6-Hydroxy-2-oxo-1,2-dihydroquinoline was found as intermediate in the degradation of 6-hydroxyquinoline and quinoline. 2-Oxo-1,2-dihydroquinoline was the first metabolite in the degradation of quinoline.     

Effect of chlorine substitution on the bacterial metabolism of various polychlorinated biphenyls.

Of 36 pure isomers (chlorine numbers 1 to 5) of polychlorinated biphenyls examined, 23 compounds were metabolized by Alcaligenes sp. strain Y42, and 33 compounds were metabolized by Acinetobacter sp. strain P6. The major pathway of many polychlorinated biphenyl isomers examined was considered to proceed through 2',3'-dihydro-2',3'-diol compounds, concomitant dehydrogenated 2',3'-dihydroxy compounds, subsequently the 1',2'-meta-cleavage compounds (chlorinated derivatives of 2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoic acids), and then chlorobenzoic acids. The meta-cleavage products were usually converted to chlorobenzoic acids upon further incubation in many polychlorinated biphenyls, but they accumulated specifically in the metabolism of 2,4'-, 2,4,4'-, and 2,5,4'-chlorobiphenyls, which are all chlorinated at the 2,4'-position in the molecules in common. Dihydroxy compounds accumulated mainly in the metabolism of 2,6-, 2,3,6-, 2,4,2',5'-, 2,5,2',5'-, and 2,4,5,2',5'-chlorobiphenyls by Acinetobacter sp. P6. The 2,3,2',3'-, 2,3,2',5'-, and 2,4,5,2',3'-chlorobiphenyls, which are chlorinated at the 2,3-position of one of the rings, were metabolized in a different fashion. Two major metabolites of a chlorobenzoic acid and an unknown compound accumulated always in the metabolism of this group of polychlorinated biphenyls. 2,4,6-Trichlorobiphenyl was metabolized quite differently between the two organisms. Alcaligenes sp. Y42 metabolized this compound very slowly to trichlorobenzoic acid by the major oxidative route. In contrast, Acinetobacter sp. P6 metabolized it to a trihydroxy compound via a dihydroxy compound.     

Effect of chlorine substitution on the bacterial metabolism of various polychlorinated biphenyls.

Of 36 pure isomers (chlorine numbers 1 to 5) of polychlorinated biphenyls examined, 23 compounds were metabolized by Alcaligenes sp. strain Y42, and 33 compounds were metabolized by Acinetobacter sp. strain P6. The major pathway of many polychlorinated biphenyl isomers examined was considered to proceed through 2',3'-dihydro-2',3'-diol compounds, concomitant dehydrogenated 2',3'-dihydroxy compounds, subsequently the 1',2'-meta-cleavage compounds (chlorinated derivatives of 2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoic acids), and then chlorobenzoic acids. The meta-cleavage products were usually converted to chlorobenzoic acids upon further incubation in many polychlorinated biphenyls, but they accumulated specifically in the metabolism of 2,4'-, 2,4,4'-, and 2,5,4'-chlorobiphenyls, which are all chlorinated at the 2,4'-position in the molecules in common. Dihydroxy compounds accumulated mainly in the metabolism of 2,6-, 2,3,6-, 2,4,2',5'-, 2,5,2',5'-, and 2,4,5,2',5'-chlorobiphenyls by Acinetobacter sp. P6. The 2,3,2',3'-, 2,3,2',5'-, and 2,4,5,2',3'-chlorobiphenyls, which are chlorinated at the 2,3-position of one of the rings, were metabolized in a different fashion. Two major metabolites of a chlorobenzoic acid and an unknown compound accumulated always in the metabolism of this group of polychlorinated biphenyls. 2,4,6-Trichlorobiphenyl was metabolized quite differently between the two organisms. Alcaligenes sp. Y42 metabolized this compound very slowly to trichlorobenzoic acid by the major oxidative route. In contrast, Acinetobacter sp. P6 metabolized it to a trihydroxy compound via a dihydroxy compound.     

Microbial epoxidation of the tricyclic sesquiterpene presilphiperfolane angelate ester

Microbial transformation studies on 2beta-angeloyloxy-5beta,8beta-dihydroxypresilphiperfolane have revealed that it was metabolized by a number of microorganisms. Using a standard two-stage fermentation technique, Mucor ramannianus (ATCC 9628) produced three metabolites. One of them was characterized as the novel metabolite (2'R,3'R)-(+)-2beta-(2',3'-epoxyangeloyloxy)-5beta,8beta-dihydroxypresilphiperfolane on the basis of spectral data. The absolute configuration at both oxirane carbons was confirmed by spectral and optical activity data of the hydrolysis product of the novel metabolite which is (2R,3R)-(+)-2,3-epoxyangelic acid.     

反应器进水管生物膜中喹啉降解菌的分离鉴定及降解特性

【背景】喹啉是一类高毒、致癌且难降解的含氮杂环化合物,本实验室建立了一个长期高效运行的反硝化喹啉降解生物反应器。【目的】从反应器进水管富集的生物膜中筛选有氧条件下降解喹啉的菌株。【方法】通过以喹啉为唯一碳源的培养基来富集、分离、纯化菌株;利用16S rRNA基因的序列分析鉴定分离株的系统发育地位;比较不同pH及温度条件下菌株的喹啉降解特性。【结果】经鉴定,4株分离物Q1、Q3、Q7和Q8分别属于Sphingobium、Massilia、Rhodococcus和Dyadobacter属。降解实验表明,以上菌株均能在48 h内实现50 mg/L喹啉的完全去除,但各自表现出不同的降解特性,其中Q1、Q3和Q8在降解过程中都检测到了喹啉降解产物2-羟基喹啉的积累。降解喹啉的Sphingobium、Massilia和Dyadobacter属菌株尚未见报道。【结论】从喹啉降解生物反应器的进水管内分离的4株喹啉降解菌可为设计处理含喹啉工业废水的反应器提供新菌种资源,对于完善喹啉生物降解机理研究具有实际意义。     

Comparison of the mutagenicity of quinoline and all monohydroxyquinolines with a series of arene oxide, trans-dihydrodiol, diol epoxide, N-oxide and arene hydrate derivatives of quinoline in the Ames/Salmonella microsome test.

Fourteen new quinoline derivatives were synthesised and their mutagenicity compared in the Ames test using Salmonella typhimurium TA100 as indicator strain with and without (Aroclor-induced) S9 mix. None of the synthesised quinoline derivatives had to our knowledge been examined before in the Ames test. Quinoline and the monohydroxyquinolines were included as reference compounds. Three of the new derivatives, i.e., quinoline 7,8-oxide, N-methyl-quinoline 5,6-oxide and trans-quinoline-5,6,7,8-dioxide appeared to be mutagenic. Quinoline 7,8-oxide was positive only in the presence of S9 mix, the specific mutagenicity amounting to 2498 +/- 96 and 1289 +/- 120 revertants per mumole with 20 and 10% S9 in the mix, respectively. Both N-methyl-quinoline 5,6-oxide and trans-quinoline-5,6,7,8-dioxide were weakly positive, the former only in the presence of the S9 mix, and the latter irrespective of the presence of S9 mix, the specific mutagenicity amounting to 134 +/- 6 and 123 +/- 10 revertants per mumole, respectively. The mutagenic potency of quinoline 7,8-oxide was of the same order as that of quinoline itself and was distinctly lower than that of 8-hydroxyquinoline. Inconclusive results were obtained with trans-7,8-dihydroxy-7,8-dihydroquinoline, 5,6-dihydroxy-7,8-epoxy-5,6,7,8-tetrahydroquinoline and 8-hydroxyquinoline-N-oxide; if these compounds are mutagenic their mutagenic potency would be at least 20-30 times lower than that of the parent compounds. None of the other chemically synthesised quinoline derivatives showed mutagenic activity with TA100 either in the presence or in the absence of S9 mix. The results obtained with the reference compounds were in accordance with literature data.