Biomedical subjects

D D Focht

Publications and source records attributed to D D Focht.

At least 19 recordsLinked to original sources

PubMed2001

Methyl tert-butyl ether (MTBE) degradation by a microbial consortium.

The widespread use of methyl tert-butyl ether (MTBE) as a gasoline additive has resulted in a large number of cases of groundwater contamination. Bioremediation is often proposed as the most promising alternative after treatment. However, MTBE biodegradation appears to be quite different from the biodegradation of usual gasoline contaminants such as benzene, toluene, ethyl benzene and xylene (BTEX). In the present paper, the characteristics of a consortium degrading MTBE in liquid cultures are presented and discussed. MTBE degradation rate was fast and followed zero order kinetics when added at 100 mg l(-1). The residual MTBE concentration in batch degradation experiments ranged from below the detection limit (1 microg l(-1)) to 50 microg l(-1). The specific activity of the consortium ranged from 7 to 52 mgMTBE g(dw)(-1) h(-1) (i.e. 19-141 mgCOD g(dw) (-1) h(-1)). Radioisotope experiments showed that 79% of the carbon-MTBE was converted to carbon-carbon dioxide. The consortium was also capable of degrading a variety of hydrocarbons, including tert-butyl alcohol (TBA), tert-amyl methyl ether (TAME) and gasoline constituents such as benzene, toluene, ethylbenzene and xylene (BTEX). The consortium was also characterized by a very slow growth rate (0.1 d(-1)), a low overall biomass yield (0.11 gdw g(-1)MTBE; i.e. 0.040 gdw gCOD(-1)), a high affinity for MTBE and a low affinity for oxygen, which may be a reason for the slow or absence of MTBE biodegradation in situ. Still, the results presented here show promising perspectives for engineering the in situ bioremediation of MTBE.

Bacteria↗

PubMed1998

Cometabolism of 1,1-dichloro-2,2-bis(4-chlorophenyl)ethylene by Pseudomonas acidovorans M3GY grown on biphenyl.

1,1-Dichloro-2,2-bis(4-chlorophenyl)ethylene (DDE), a toxic breakdown product of 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane (DDT), has traditionally been viewed as a dead-end metabolite: there are no published reports detailing enzymatic ring fission of DDE by bacteria in either soil or pure culture. In this study, we investigated the ability of Pseudomonas acidovorans M3GY to transform DDE and its unchlorinated analog, 1,1-diphenylethylene (DPE). While strain M3GY could grow on DPE, cells grown on DPE as a sole carbon source could not degrade DDE. Cells grown on biphenyl, however, did degrade DDE. Mass balance analysis of [14C]DDE showed transformation of more than 40% of the recoverable radioactivity. Nine chlorinated metabolites produced from DDE were identified by gas chromatography-mass spectrometry-Fourier-transform infrared spectrometry (GC-MS-FTIR) from cultures grown on biphenyl. Recovery of these metabolites demonstrates that biphenyl-grown cells degrade DDE through a meta-fission pathway. This study provides a possible model for biodegradation of DDE in soil by biphenyl-utilizing bacteria.

Biodegradation, Environmental↗

PubMed1997

Biodegradation of 2,4-Dichlorophenol through a Distal meta-Fission Pathway.

Alcaligenes eutrophus JMP222, a derivative of A. eutrophus JMP134 which has lost plasmid pJP4 (encoding the tfd genes for the ortho fission pathway), was induced for the meta fission pathway when grown on o-cresol. Resting cell suspensions, grown on o-cresol, oxidized 2,4-dichlorophenol (2,4-DCP), a degradation product of 2,4-dichlorophenoxyacetic acid, to 3,5-dichlorocatechol. Further degradation of 3,5-dichlorocatechol was observed by the production of a yellow ring fission product with liberation of chloride. Oxidation of 2,4-DCP (305 (mu)M) in 47 hs resulted in 69% dehalogenation through this pathway. The ring fission product was characterized as 2-hydroxy-3,5-dichloro-6-oxo-hexa-2,4-dienoic acid by gas chromatography-mass spectrometry and gas chromatography-Fourier transform infrared spectroscopy. These data indicate that 2,4-DCP is degraded through a distal meta ring fission pathway, in contrast to either a suicidal proximal fission or the standard ortho fission pathway.

Journal Article↗

PubMed1996

Genetic exchange in soil between introduced chlorobenzoate degraders and indigenous biphenyl degraders.

Pseudomonas aeruginosa JB2, a chlorobenzoate degrader, was inoculated into soil having indigenous biphenyl degraders but no identifiable 2-chlorobenzoate (2CBa) or 2,5-dichlorobenzoate (2,5DCBa) degraders. The absence of any indigenous chlorobenzoate degraders was noted by the failure to obtain enrichment cultures with the addition of 2CBa, 3CBa, or 2,5DCBa and by the failure of soil DNA to hybridize to the tfdC gene, which encodes ortho fission of chlorocatechols. In contrast, DNA extracted from inoculated soils hybridized to this probe. Bacteria able to utilize both biphenyl and 2CBa as growth substrates were absent in uninoculated soil, but their presence increased with time in the inoculated soils. This increase was related kinetically to the growth of biphenyl degraders. Pseudomonas sp. strain AW, a dominant biphenyl degrader, was selected as a possible parental strain. Eight of nine recombinant strains, chosen at random, had high phenotypic similarity (90% or more) to the inoculant; the other, strain JB2-M, had 78% similarity. Two hybrid strains, P. aeruginosa JB2-3 and Pseudomonas sp. JB2-M, were the most effective of all strains, including strain AW, in metabolizing polychlorinated biphenyls (Aroclor 1242). Repetitive extragenic palindromic-PCR analysis of putative parental strains JB2 and AW and the two recombinant strains JB2-3 and JB2-M showed similar fragments among the recombinants and JB2 but not AW. These results indicate that the bph genes were transferred to the chlorobenzoate-degrading inoculant from indigenous biphenyl degraders.

Biodegradation, Environmental↗

PubMed1995

A meta cleavage pathway for 4-chlorobenzoate, an intermediate in the metabolism of 4-chlorobiphenyl by Pseudomonas cepacia P166.

Bacterial degradation of biphenyl and polychlorinated biphenyls proceeds by a well-studied pathway which produces benzoate and 2-hydroxypent-2,4-dienoate (or, in the case of polychlorinated biphenyls, the chlorinated derivatives of these compounds). Pseudomonas cepacia P166 utilizes 4-chlorobiphenyl for growth and produces 4-chlorobenzoate as a central intermediate. In this study we found that strain P166 further transforms 4-chlorobenzoate to 4-chlorocatechol, which is mineralized by a meta cleavage pathway. Key metabolites which we identified include the meta cleavage product (5-chloro-2-hydroxymuconic semialdehyde), 5-chloro-2-hydroxymuconate, 5-chloro-2-oxopent-4-enoate, 5-chloro-4-hydroxy-2-oxopentanoate, and chloroacetate. Chloroacetate accumulated transiently, and slow but stoichiometric dehalogenation was observed.

Biodegradation, Environmental↗

PubMed1994

Genetic construction of PCB degraders.

Genetic construction of recombinant strains with expanded degradative abilities may be useful for bioremedation of recalcitrant compounds, such as polychlorinated biphenyls (PCBs). Some degradative genes have been found either on conjugative plasmids or on transposons, which would facilitate their genetic transfer. The catabolic pathway for the total degradation of PCBs is encoded by two different sets of genes that are not normally found in the same organism. The bphABCD genes normally reside on the chromosome and encode for the four enzymes involved in the production of benzoate and chlorobenzoates from the respective catabolism of biphenyl and chlorobiphenyls. The genes encoding for chlorobenzoate catabolism have been found on both plasmids and the chromosome, often in association with transposable elements. Ring fission of chlorobiphenyls and chlorobenzoates involves the meta-fission pathway (3-phenylcatechol 2,3-dioxygenase) and the ortho-fission pathway (chlorocatechol 1,2-dioxygenase), respectively. As the catecholic intermediates of both pathways are frequently inhibitory to each other, incompatibilities result. Presently, all hybrid strains constructed by in vivo matings metabolize simple chlorobiphenyls through complementary pathways by comprising the bph, benzoate, and chlorocatechol genes of parental strains. No strains have yet been verified which are able to utilize PCBs having at least one chlorine on each ring as growth substrates. The possible incompatibilities of hybrid pathways are evaluated with respect to product toxicity, and the efficiency of both in vivo and in vitro genetic methods for the construction of recombinant strains able to degrade PCBs is discussed.

Bacteria↗

PubMed1994

Construction of a Novel Polychlorinated Biphenyl-Degrading Bacterium: Utilization of 3,4'-Dichlorobiphenyl by Pseudomonas acidovorans M3GY.

Pseudomonas acidovorans M3GY is a recombinant bacterium with the novel capacity to utilize a biphenyl congener chlorinated on both rings, 3,4'-dichlorobiphenyl (3,4'-DCBP), as a sole carbon and energy source. Strain M3GY was constructed with a continuous amalgamated culture apparatus (L. Kröckel and D. D. Focht, Appl. Environ. Microbiol. 53:2470-2475, 1987) with P. acidovorans CC1(19), a chloroacetate and biphenyl degrader, and Pseudomonas sp. strain CB15(1), a biphenyl and 3-chlorobenzoate degrader. Genetic and phenotypic data showed the recipient parental strain to be P. acidovorans CC1 and the donor parental strain to be Pseudomonas sp. strain CB15. In growth experiments with 3,4'-DCBP as a sole source of carbon, cultures of strain M3GY increased in absorbance from 0.07 to 0.39 in 29 days while reaching a protein concentration of 58 mug ml and 67% substrate dehalogenation. 4-Chlorobenzoate was identified from culture supernatants of strain M3GY by gas chromatography-infrared spectrometry-mass spectrometry; this would be consistent with the oxidation of the m-chlorinated ring through the standard biphenyl pathway. 4-Chlorobenzoate was converted to 4-chlorocatechol, which was metabolized through the meta-fission pathway. The construction of P. acidovorans M3GY, with the novel capability to utilize 3,4'-DCBP, thus involves the complete use of meta-fission pathways for sequential rupture of the biphenyl and chlorobenzoate rings.

Journal Article↗

PubMed1994

Formation of chlorocatechol meta cleavage products by a pseudomonad during metabolism of monochlorobiphenyls.

Pseudomonas cepacia P166 was able to metabolize all monochlorobiphenyls to the respective chlorobenzoates. Although they transiently accumulated, the chlorobenzoate degradation intermediates were further metabolized to chlorocatechols, which in turn were meta cleaved. 2- and 3-Chlorobiphenyl both produced 3-chlorocatechol, which was transformed to an acyl halide upon meta cleavage. 3-Chlorocatechol metabolism was toxic to the cells and impeded monochlorobiphenyl metabolism. In the case of 2-chlorobiphenyl, toxicity was manifested as a diminished growth rate, which nevertheless effected rapid substrate utilization. In the case of 3-chlorobiphenyl, which generates 3-chlorocatechol more rapidly than does 2-chlorobiphenyl, toxicity was manifested as a decrease in viable cells during substrate utilization. 4-Chlorobenzoate was transformed to 4-chlorocatechol, which was metabolized by a meta cleavage pathway leading to dehalogenation. Chloride release from 4-chlorocatechol metabolism, however, was slow and did not coincide with rapid 4-chlorocatechol turnover. Growth experiments with strain P166 on monochlorobiphenyls illustrated the difficulties of working with hydrophobic substrates that generate toxic intermediates. Turbidity could not be used to measure the growth of bacteria utilizing monochlorobiphenyls because high turbidities were routinely measured from cultures with very low viable-cell counts.

Benzoates↗

PubMed1993

Enhanced mineralization of polychlorinated biphenyls in soil inoculated with chlorobenzoate-degrading bacteria.

An Altamont soil containing no measurable population of chlorobenzoate utilizers was examined for the potential to enhance polychlorinated biphenyl (PCB) mineralization by inoculation with chlorobenzoate utilizers, a biphenyl utilizer, combinations of the two physiological types, and chlorobiphenyl-mineralizing transconjugants. Biphenyl was added to all soils, and biodegradation of 14C-Aroclor 1242 was assessed by disappearance of that substance and by production of 14CO2. Mineralization of PCBs was consistently greatest (up to 25.5%) in soils inoculated with chlorobenzoate degraders alone. Mineralization was significantly lower in soils receiving all other treatments: PCB cometabolizer (10.7%); chlorobiphenyl mineralizers (8.7 and 14.9%); and mixed inocula of PCB cometabolizers and chlorobenzoate utilizers (11.4 and 18.0%). However, all inoculated soils had higher mineralization than did the uninoculated control (3.1%). PCB disappearance followed trends similar to that observed with the mineralization data, with the greatest degradation occurring in soils inoculated with the chlorobenzoate-degrading strains Pseudomonas aeruginosa JB2 and Pseudomonas putida P111 alone. While the mechanism by which the introduction of chlorobenzoate degraders alone enhanced biodegradation of PCBs could not be elucidated, the possibility that chlorobenzoate inoculants acquired the ability to metabolize biphenyl and possibly PCBs was explored. When strain JB2, which does not utilize biphenyl, was inoculated into soil containing biphenyl and Aroclor 1242, the frequency of isolates able to utilize biphenyl and 2,5-dichlorobenzoate increased progressively with time from 3.3 to 44.4% between 15 and 48 days, respectively. Since this soil contained no measurable level of chlorobenzoate utilizers yet did contain a population of biphenyl utilizers, the possibility of genetic transfer between the latter group and strain JB2 cannot be excluded.

Biodegradation, Environmental↗

PubMed1993

Variation in chlorobenzoate catabolism by Pseudomonas putida P111 as a consequence of genetic alterations.

Pseudomonas putida P111 is able to utilize a broad range of monochlorinated, dichlorinated, and trichlorinated benzoates. The involvement of two separate dioxygenases was noted from data on plasmid profiles and DNA hybridization. The benzoate dioxygenase, which converts 3-chlorobenzoate (3-CB), 4-CB, and benzoate to the corresponding catechols via reduction of a dihydrodiol, was shown to be chromosomally coded. The chlorobenzoate-1,2-dioxygenase that converts ortho-chlorobenzoates to the corresponding catechols without the need of a functional dioldehydrogenase was shown to be encoded on plasmid pPB111 (75 kb). Cured strains were unable to utilize ortho-chlorobenzoates for growth. DNA hybridization data indicated that catabolism of the corresponding chlorocatechols was coded on chromosomal genes. Maintenance of plasmid pPB111 was dependent on the presence of ortho-chlorobenzoates in the growth media. A unique variant of P111 (P111D), able to grow on 3,5-dichlorobenzoate (3,5-DCB), was obtained by continuous subculturing from media containing progressively lower and higher concentrations of 3-CB and 3,5-DCB, respectively. The low frequency of segregants able to grow on 2,5-DCB, 2,3-DCB, and 2,3, 5-trichlorobenzoate was evident by lag periods greater than 200 h. Continued subculture on 3,5-DCB resulted in the formation of new plasmid pPH111 (120 kb), which was homologous to pPB111. A probe from the clc operon, which encodes for the chlorocatechol pathway, hybridized to plasmid pPH111 and to the chromosome of the wild-type strain P111 but not to its plasmid pPB111 nor to the chromosome of strain P111A, which had lost the ability to utilize chlorobenzoates.(ABSTRACT TRUNCATED AT 250 WORDS)

Biodegradation, Environmental↗

PubMed1992

Mineralization of 2-chloro- and 2,5-dichlorobiphenyl by Pseudomonas sp. strain UCR2.

Pseudomonas sp. strain UCR2 was isolated from a multi-chemostat mating experiment between a chlorobenzoate-degrader, Pseudomonas aeruginosa strain JB2, and a chlorobiphenyl-degrader, Arthrobacter sp. strain B1Barc. Strain UCR2 differed from either of the parental organisms in that it grew on both 2-chloro- and 2,5-dichlorobiphenyl with concomitant release of chloride. Phenotypic typing by the Biolog system indicated that strain UCR2 shared greater similarity with strain JB2 (88%) than strain B1Barc (3%). In DNA:DNA hybridization experiments, genomic DNA from strain UCR2 hybridized with both strain JB2 and strain B1Barc, with the former pairing yielding a much stronger signal than the latter. In contrast, no hybridization whatsoever was observed when the parental organisms strains JB2 and B1Barc were probed against each other.

Biodegradation, Environmental↗

PubMed1992

Degradation of 2-methylbenzoic acid by Pseudomonas cepacia MB2.

We report the isolation of Pseudomonas cepacia MB2, believed to be the first microorganism to utilize 2-methylbenzoic acid as the sole carbon source. Its growth range included all mono- and dimethylbenzoates (with the exception of 2,5- and 2,6-dimethylbenzoates) and 3-chloro-2-methylbenzoate (but not 4- or 5-chloro-2-methylbenzoate) but not chlorobenzoates lacking a methyl group. 2-Chlorobenzoate, 3-chlorobenzoate, and 2,3-, 2,4-, and 3,4-dichlorobenzoates inhibited growth of MB2 on 2-methylbenzoate as a result of cometabolism to the corresponding chlorinated catechols which blocked the key enzyme catechol 2,3-dioxygenase. A metapyrocatechase-negative mutant, MB2-G5, showed accumulation of dimethylcatechols from 2,3- and 3,4-dimethylbenzoates, and phenols were detected in resting-cell transformation extracts bearing the same substitution pattern as the original substrate, presumably following thermal degradation of the intermediate dihydrodiol. 2-Methylphenol was also found in extracts of the mutant cells with 2-methylbenzoate. These observations suggested a major route of methylbenzoate metabolism to be dioxygenation to a carboxy-hydrodiol which then forms a catechol derivative. In addition, the methyl group of 2-methylbenzoate was oxidized to isobenzofuranone (by cells of MB2-G5) and to phthalate (by cells of a separate mutant that could not utilize phthalate, MB2-D2). This pathway also generated a chlorinated isobenzofuranone from 3-chloro-2-methylbenzoate.

Benzoates↗

PubMed1992

Construction of a 3-chlorobiphenyl-utilizing recombinant from an intergeneric mating.

Recombinant Pseudomonas sp. strain CB15, which grows on 3-chlorobiphenyl (3CB), was constructed from Pseudomonas sp. strain HF1, which grows on 3-chlorobenzoate, and from Acinetobacter sp. strain P6, which grows on biphenyl, by using a continuous amalgamated culture apparatus. DNA from strains CB15 and HF1 hybridized very strongly to each other, while hybridization between both parental strains, HF1 and P6, was negligible. However, DNA from the recombinant CB15 hybridized moderately to strongly with three specific fragments of parental strain P6. Strains HF1 and P6 did not grow on 3CB, but recombinant strain CB15 mineralized this compound and released inorganic chloride. When growing on 3CB, strain CB15 accumulated brown products, one of which was identified as 3-chloro-5-(2'-hydroxy-3'-chlorophenyl)-1,2-benzoquinone by mass spectrometry. Emulsification and mechanical fragmentation greatly increased the rate of 3CB mineralization by strain CB15. At least three methods of inhibition from catecholic intermediates may account for slow growth on 3CB. The meta fission of 2,3-dihydroxybiphenyl (the nonchlorinated analog of the metabolic intermediate 3-chloro-2',3'-dihydroxybiphenyl) was affected by substrate inhibition (Vmax = 359 nmol.min-1.mg-1, Km = 114 microM, Kss [the inhibition constant] = 951 microM) and was also inhibited by 3-chlorocatechol. The ortho fission of 3-chlorocatechol, a degradation product, followed Michaelis-Menten kinetics (Vmax = 365 nmol.min-1.mg-1, Km = 1 microM), but the addition of 2,3-dihydroxybiphenyl inhibited the reaction (Ki = 0.87 microM).(ABSTRACT TRUNCATED AT 250 WORDS)

Acinetobacter↗

PubMed1992

Utilization of 3-chloro-2-methylbenzoic acid by Pseudomonas cepacia MB2 through the meta fission pathway.

Pseudomonas cepacia MB2 grew on 3-chloro-2-methylbenzoate as a sole carbon source by metabolism through the meta fission pathway with the subsequent liberation of chloride. meta pyrocatechase activity in cell extracts was induced strongly by 3-chloro-2-methylbenzoate, but not by nongrowth analogs 4- or 5-chloro-2-methylbenzoate. Although rapid turnover of metabolites precluded direct identification, a mutant strain MB2-G5 lacking meta pyrocatechase activity produced 4-chloro-3-methylcatechol when incubated with 3-chloro-2-methylbenzoate. The catecholic product, confirmed by nuclear magnetic resonance and mass spectral analyses, produced a transient meta fission product (lambda max = 391 nm) from cell extracts of the wild-type MB2 strain. Further confirmation of meta pyrocatechase activity was noted by conversion of 4-chlorocatechol to 2-hydroxy-5-chloromuconic semialdehyde, which was not further metabolized. In contrast to 3-chlorocatechol, which was not metabolized and is known to generate suicidal products, 4-chlorocatechols do not generate acyl halides. Thus, further metabolism of the ring fission products is governed in strain MB2 by their suitability as substrates for the hydrolase.

Burkholderia cepacia↗

PubMed1991

Cometabolism of 3,4-dichlorobenzoate by Acinetobacter sp. strain 4-CB1.

When Acinetobacter sp. strain 4-CB1 was grown on 4-chlorobenzoate (4-CB), it cometabolized 3,4-dichlorobenzoate (3,4-DCB) to 3-chloro-4-hydroxybenzoate (3-C-4-OHB), which could be used as a growth substrate. No cometabolism of 3,4-DCB was observed when Acinetobacter sp. strain 4-CB1 was grown on benzoate. 4-Carboxyl-1,2-benzoquinone was formed as an intermediate from 3,4-DCB and 3-C-4-OHB in aerobic and anaerobic resting-cell incubations and was the major transient intermediate found when cells were grown on 3-C-4-OHB. The first dechlorination step of 3,4-DCB was catalyzed by the 4-CB dehalogenase, while a soluble dehalogenase was responsible for dechlorination of 3-C-4-OHB. Both enzymes were inducible by the respective chlorinated substrates, as indicated by oxygen uptake experiments. The dehalogenase activity on 3-C-4-OHB, observed in crude cell extracts, was 109 and 44 nmol of 3-C-4-OHB min-1 mg of protein-1 under anaerobic and aerobic conditions, respectively. 3-Chloro-4-hydroxybenzoate served as a pseudosubstrate for the 4-hydroxybenzoate monooxygenase by effecting oxygen and NADH consumption without being hydroxylated. Contrary to 4-CB metabolism, the results suggest that 3-C-4-OHB was not metabolized via the protocatechuate pathway. Despite the ability of resting cells grown on 4-CB or 3-C-4-OHB to carry out all of the necessary steps for dehalogenation and catabolism of 3,4-DCB, it appeared that 3,4-DCB was unable to induce the necessary 4-CB dehalogenase for the initial p-dehalogenation step.(ABSTRACT TRUNCATED AT 250 WORDS)

Acinetobacter↗

PubMed1991

Metabolism of and inhibition by chlorobenzoates in Pseudomonas putida P111.

Pseudomonas putida P111 was isolated by enrichment culture on 2,5-dichlorobenzoate and was also able to grow on 2-chloro-, 3-chloro-, 4-chloro-, 2,3-dichloro-, 2,4-dichloro-, and 2,3,5-trichlorobenzoates. However, 3,5-dichlorobenzoate completely inhibited growth of P111 on all ortho-substituted benzoates that were tested. When 3,5-dichlorobenzoate was added as a cosubstrate with either 3- or 4-chlorobenzoate, cell yields and chloride release were greater than those observed from growth on either monochlorobenzoate alone. Moreover, resting cells of P111 grown on 4-chlorobenzoate released chloride from 3,5-dichlorobenzoate and produced no identifiable intermediate. In contrast, resting cells grown on 2,5-dichlorobenzoate metabolized 3,5-dichlorobenzoate without release of chloride and accumulated a degradation product, which was identified as 1-carboxy-1,2-dihydroxy-3,5-dichlorocyclohexadiene on the basis of gas chromatography-mass spectrometry confirmation of its two acid-hydrolyzed products, 3,5- and 2,4-dichlorophenol. Since 3,5-dichlorocatechol was rapidly metabolized by cells grown on 2,5-dichlorobenzoate, it is apparent that 1-carboxy-1,2-dihydroxy-3,5-dichlorocyclohexadiene is not further metabolized by these cells. Moreover, induction of a functional dihyrodiol dehydrogenase would not be required for growth of P111 on other ortho-chlorobenzoates since the corresponding chlorodihydrodiols produced from a 1,2-dioxygenase attack would spontaneously decompose to the corresponding catechols. In contrast, growth on 3-chloro-, 4-chloro-, or 3,5-dichlorobenzoate requires a functional dihydrodiol dehydrogenase, yet only the two monochlorobenzoates appear to induce for it.

Biodegradation, Environmental↗

PubMed1990

Bacterial degradation of ring-chlorinated acetophenones.

Two strains, Alcaligenes sp. strain ACA and Pseudomonas fluorescens ACB, isolated from acetophenone and 4'-hydroxyacetophenone enrichments, respectively, cometabolize a range of chlorinated acetophenones (CAs). A biological Baeyer-Villiger reaction converts the CA to chlorophenyl acetate. This is evident only in the presence of an esterase inhibitor, since the CA is normally rapidly hydrolyzed to a chlorophenol which has the same substitution pattern as the original ketone. The oxygenase that attacks the ketone uses NADPH in the incorporation of one atom of O(2) and is strongly inhibited by phenols that bear an ortho or meta chlorine or bromine, but much less by cresols or phenol itself. A feedback phenomenon may thus account for the inability of strain ACA to grow on CAs, which also fail to induce the cells for their own metabolism.

Journal Article↗

PubMed1990

Degradation of mono-, di-, and trihalogenated benzoic acids by Pseudomonas aeruginosa JB2.

Pseudomonas aeruginosa JB2 was isolated from a polychlorinated biphenyl-contaminated soil by enrichment culture containing 2-chlorobenzoate as the sole carbon source. Strain JB2 was subsequently found also to grow on 3-chlorobenzoate, 2,3- and 2,5-dichlorobenzoates, 2,3,5-trichlorobenzoate, and a wide range of other mono- and dihalogenated benzoic acids. Cometabolism of 2,4-dichlorobenzoate was also observed. Chlorocatechols were the central intermediates of all chlorobenzoate catabolic pathways. Degradation of 2-chlorobenzoate was routed through 3-chlorocatechol, whereas 4-chlorocatechol was identified from the metabolism of both 2,3- and 2,5-dichlorobenzoate. The initial attack on chlorobenzoates was oxygen dependent and most likely mediated by dioxygenases. Although plasmids were not detected in strain JB2, spontaneous mutants were detected in 70% of glycerol-grown colonies. The mutants were all of the following phenotype: benzoate+, 3-chlorobenzoate+, 2-chlorobenzoate-, 2,3-dichlorobenzoate-, 2,5-dichlorobenzoate-. While chlorocatechols were oxidized by the mutants at wild-type levels, oxidation of 2-chloro- and 2,3- and 2,5-dichlorobenzoates was substantially diminished. These findings suggested that strain JB2 possessed, in addition to the benzoate dioxygenase, a halobenzoate dioxygenase that was necessary for the degradation of chlorobenzoates substituted in the ortho position.

Biodegradation, Environmental↗