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PubMed1982

The purification and properties of 2,4-dichlorophenol hydroxylase from a strain of Acinetobacter species.

1. 2,4-Dichlorophenol hydroxylase has been purified 13-fold from Acinetobacter grown on 2,4-dichlorophenoxyacetic acid as sole carbon source. The enzyme was estimated to be 80-90% pure by electrophoresis. 2. The enzyme has a relative molecular mass of about 240 000 and consists of four subunits of identical size. 3. The enzyme contains FAD as the prosthetic group. FAD could not be replaced by riboflavin or FMN in reconstituting active enzyme from apoenzyme. 4. The reaction catalysed is an NADPH-dependent hydroxylation of 2,4-dichlorophenol with the formation of 3,5-dichlorocatechol as product. The reaction stoichiometry is typical of a monooxygenase with an external electron donor. NADPH is the preferred reduced pyridine nucleotide substrate but the enzyme can function with NADH. 5. The enzyme possesses broad effector specificity. In addition to 2,4-dichlorophenol, 4-chlorophenol and 4-chloro-2-methylphenol are true substrates for the enzyme. A number of 'non-substrate effectors' has been found. 6. The enzyme is sensitive to thiol-inhibiting reagents.

Acinetobacter↗
PubMed1995

Degradation of trichlorophenols by Alcaligenes eutrophus JMP134.

The degradation of chlorophenols by Alcaligenes eutrophus JMP134 (pJP4) was studied. The strain grew on 2,4,6-trichlorophenol or 2,4,6-tribromophenol as the sole carbon and energy source. Complete degradation of 2,4,6-trichlorophenol was confirmed by chloride release and gas chromatography analysis of supernatants from growth cultures. The 2,3,5-, 2,3,4-, 2,3,6- and 2,4,5-isomers of trichlorophenol did not support growth. However, up to 40% of 2,4,5-trichlorophenol was mineralized during growth of A. eutrophus on chemostats fed with either phenol (0.4 mM) or 2,4,6-trichlorophenol (0.4 mM) plus 2,4,5-trichlorophenol (0.1 mM). Growth on 2,4,6-trihalophenols was also observed in A. eutrophus JMP222, the strain lacking pJP4, suggesting that this new degradative ability reported for A. eutrophus is not related to pJP4 encoded catabolic functions.

Alcaligenes↗
PubMed1999

Degradation of 2,4-dichlorophenol and pentachlorophenol by two brown rot fungi.

Wheat straw cultures of the brown rot fungi Gloeophyllum striatum and G. trabeum degraded 2,4-dichlorophenol and pentachorophenol. Up to 54% and 27% 14CO2, respectively, were liberated from uniformly 14C-labeled substrates within 6 weeks. Under identical conditions Trametes versicolor, a typical white rot species employed as reference, evolved up to 42% and 43% 14CO2 and expressed high activities of laccase, manganese peroxidase, and manganese-independent peroxidase. No such activity could be detected in straw or liquid cultures of Gloeophyllum. Moreover, G. striatum degraded both chlorophenols most efficiently under non-cometabolic conditions, i.e. on a defined mineral medium lacking sources of carbon, nitrogen and phosphate.

Basidiomycota↗
PubMed2007

Adaptation of the psychrotroph Arthrobacter chlorophenolicus A6 to growth temperature and the presence of phenols by changes in the anteiso/iso ratio of branched fatty acids.

Arthrobacter chlorophenolicus is a previously described Gram-positive bacterium capable of degrading high concentrations of several phenolic compounds under optimal mesophilic (28 degrees C) as well as psychrophilic (5 degrees C) conditions. However, the exact mechanisms by which this organism is able to tolerate such extremes in temperature and high levels of toxic compounds are currently not known. In this study, we monitored changes in the fatty acid composition of the cell membrane under different extreme growth conditions. Arthrobacter chlorophenolicus adapts to differences in temperature and phenol concentrations by altering the anteiso/iso ratio of fatty acids in the cell membrane to different extents. According to the different physico-chemical properties of those two species of branched fatty acids, the bacteria showed an increased amount of anteiso fatty acids when grown under psychrophilic conditions to decrease the viscosity of their membranes. On the other hand, at higher growth temperatures as well as in the presence of toxic concentrations of phenol, 4-chlorophenol and 4-nitrophenol, the cells adapted their membrane by a dose-dependent decrease in the anteiso/iso ratio, leading to a more rigid membrane and counteracting the fluidity increase caused by the higher temperature and the organic solvents.

Adaptation, Physiological↗
PubMed1994

Reaction of inflamed periapical tissue to intracanal medicaments and root canal sealers.

The effects of different intracanal medicaments and zinc oxide-eugenol based root canal sealers on an experimentally induced apical periodontitis were studied histologically in mesial roots of lower molars of Wistar rats. After root canal instrumentation each canal was filled either with an intracanal medicament twice for 3 days each time or with a sealer for 21 days. The intracanal medicament chlorophenol caused periapical tissue damage. P-chloroxylenol-camphor lead to periapical improvement as did 5% sodium-hypochlorite. 12% sodium-hypochlorite gave tissue damage. After intracanal medication with an aqueous suspension of calcium hydroxide periapical repair was clearly visible. A combination of a corticoid and an antibiotic appeared to induce damage of the periapical tissues. The root canal sealers Endomethasone and N2 essentially impaired periapical repair. The results were acceptable for Aptal-Zink-Harz root canal fillings after 21 days as well as after 56 days.

Administration, Topical↗
PubMed1980

Laboratory studies of disinfectants against Legionella pneumophila.

Legionella pneumophila suspended in tap water was exposed to biocides recommended for inhibiting biological growth in cooling towers and evaporative condensers of air-conditioning systems. Chlorine, 2,2-dibromo-3-nitrilopropionamide, and a compound containing didecyldimethylammonium chloride and isopropanol were effective in destroying concentratiois of 10(5) to 10(6) viable cells per ml. Formulations consisting of 5-chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-4-isothiazolin-3-one, disodium ethylene bis(thiocarbamate) and sodium dimethyl dithiocarbamate, and a phenolic with pentachlorophenate and sodium salts of other chlorophenols were less effective.

1-Propanol↗
PubMed1982

Biodegradation of 2,4,5-trichlorophenoxyacetic acid by a pure culture of Pseudomonas cepacia.

A pure culture of Pseudomonas cepacia, designated AC1100, that can utilize 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) as its sole source of carbon and energy was isolated. An actively growing culture of AC1100 was able to degrade more than 97% of 2,4,5-T, present at 1 mg/ml, within 6 days as determined by chloride release, gas chromatographic, and spectrophotometric analyses. The ability of AC1100 to oxidize a variety of chlorophenols and related compounds is also reported.

2,4,5-Trichlorophenoxyacetic Acid↗
PubMed1986

Effects of pentachlorophenol and some of its known and possible metabolites on fungi.

The fungicidal activity of pentachlorophenol and its derivatives against 16 species of fungi representing 14 genera was tested. In relation to pentachlorophenol, no increase in fungistatic activity was found for pentachloroanisole, pentachloronitrobenzene, hexachlorobenzene, pentachlorophenyl acetate, o- and p-chloranil, the three isomeric chlorophenols, 2,6-dichlorophenol, the three isomeric tetrachlorobenzenediols, the three isomeric tetrachlorodimethoxybenzenes, the three isomeric tetrachlorobenzenediol diacetates, and all of the isomeric mono-, di-, tri-, and tetrachloroanisoles, except for 2,3,5-trichloroanisole with Geotrichum candidadum PC 67 and for 2,3,5,6-tetrachloroanisole with Mucor circinelloides PC 1. Increasing fungistatic activities were seen with 3,5-dichlorophenol, four trichlorophenols, and 2,3,4,5-tetrachlorophenol for all of the strains, with four dichlorophenols, 2,4,6-trichlorophenol, and two tetrachlorophenols for some strains, and with 2,3,6-trichlorophenol for only one strain (M. circinelloides PC 1).

Chlorophenols↗
PubMed1987

Degradation of chlorinated phenols by a pentachlorophenol-degrading bacterium.

A pentachlorophenol (PCP)-degrading Flavobacterium sp. was tested for its ability to dechlorinate other chlorinated phenols by using resting cells that had been grown in the presence or absence of PCP. Phenols with chlorine atoms at positions 2 and 6 of the phenol ring were dechlorinated completely by PCP-induced cells. Other chlorinated phenols were not significantly mineralized. When PCP was added to a culture growing on L-glutamate, there was a lag period before the start of PCP degradation. When similar cells were treated with chloramphenicol prior to the addition of PCP, they did not degrade added PCP, even after prolonged incubations. Thus, the enzymes necessary for PCP degradation appeared to be inducible. Suspensions of cells grown in the presence of 2,4,6-trichlorophenol or 2,3,5,6-tetrachlorophenol did not show a lag period for mineralization of PCP, 2,4,6-trichlorophenol, or 2,3,5,6-tetrachlorophenol, indicating that one enzyme system probably was induced for the biodegradation of all three compounds. Nondegradable chlorophenols were toxic toward the Flavobacterium sp., probably acting as uncouplers of oxidative phosphorylation.

Biodegradation, Environmental↗
PubMed1987

Effect of adaptation to phenol on biodegradation of monosubstituted phenols by aquatic microbial communities.

The adaptation of a mixed aquatic microbial community to phenol was examined in microcosms receiving phenol as a sole carbon source. Extended exposure (adaptation) to phenol resulted in adaptation of the microbial community to the structurally related aromatic compounds m-cresol, m-aminophenol, and p-chlorophenol. The increased biodegradation potential of the phenol-adapted microbial community was accompanied by a concurrent increase in the number of microorganisms able to degrade the three test compounds. Thus, adaptation to the three test chemicals was likely a growth-related result of extended exposure to phenol. The results indicate that adaptation to a single chemical may increase the assimilative capacity of an aquatic environment for other related chemicals even in the absence of adaptation-inducing levels of those materials.

Adaptation, Physiological↗
PubMed1987

Adaptation to and biodegradation of xenobiotic compounds by microbial communities from a pristine aquifer.

The ability of subsurface microbial communities to adapt to the biodegradation of xenobiotic compounds was examined in aquifer solids samples from a pristine aquifer. An increase in the rates of mineralization of radiolabeled substrates with exposure was used as an indication of adaptation. For some compounds, such as chlorobenzene and 1,2,4-trichlorobenzene, slight mineralization was observed but no adaptation was apparent during incubations of over 8 months. Other compounds demonstrated three patterns of response. For m-cresol, m-aminophenol, and aniline intermediate rates of biodegradation and a linear increase in the percent mineralized with time were observed. Phenol, p-chlorophenol, and ethylene dibromide were rapidly metabolized initially, with a nonlinear increase in the percent mineralized with time, indicating that the community was already adapted to the biodegradation of these compounds. Only p-nitrophenol demonstrated a typical adaptation response. In different samples of soil from the same layer in the aquifer, the adaptation period to p-nitrophenol varied from a few days to as long as 6 weeks. In most cases the concentration of xenobiotic added, over the range from a few nanograms to micrograms per gram, made no difference in the response. Most-probable-number counts demonstrated that adaptation is accompanied by an increase in specific degrader numbers. This study has shown that diverse patterns of response occur in the subsurface microbial community.

Aminophenols↗
PubMed1988

Laccase-mediated detoxification of phenolic compounds.

The ability of a polyphenoloxidase, the laccase of the fungus Rhizoctonia praticola, to detoxify phenolic pollutants was examined. The growth of the fungus could be inhibited by phenolic compounds, and the effective concentration was dependent on the substituents of the phenol. A toxic amount of a phenolic compound was added to a fungal growth medium in the presence or absence of a naturally occurring phenol, and half of the replicates also received laccase. The medium was then inoculated with R. praticola, and the levels of phenols in the medium were monitored by high-performance liquid chromatography analysis. The addition of the laccase reversed the inhibitory effect of 2,6-xylenol, 4-chloro-2-methylphenol, and p-cresol. Other compounds, e.g., o-cresol and 2,4-dichlorophenol, were detoxified only when laccase was used in conjunction with a natural phenol such as syringic acid. The toxicity of p-chlorophenol and 2,4,5-trichlorophenol could not be overcome by any additions. The ability of the laccase to alter the toxicity of the phenols appeared to be related to the capacity of the enzyme to decrease the levels of the parent compound by transformation or cross-coupling with another phenol.

Chlorophenols↗
PubMed1989

Anaerobic biodegradation of 2,4-dichlorophenol in freshwater lake sediments at different temperatures.

Anaerobic degradation of 2,4-dichlorophenol (2,4-DCP) between 5 and 72 degrees C was investigated. Anaerobic sediment slurries prepared from local freshwater pond sediments were partitioned into anaerobic tubes or serum vials, which then were incubated separately at the various temperatures. Reductive 2,4-DCP dechlorination occurred only in the temperature range between 5 and 50 degrees C, although methane was formed up to 60 degrees C. In sediment samples from two sites and at all tested temperatures from 5 to 50 degrees C, 2,4-DCP was transformed to 4-chlorophenol (4-CP). The 4-CP intermediate was subsequently degraded after an extended lag period in the temperature range from 15 to 40 degrees C. Adaptation periods for 2,4-DCP transformation decreased between 5 and 25 degrees C, were essentially constant between 25 and 35 degrees C, and increased in the tubes incubated at temperatures between 35 and 40 degrees C. The degradation rates increased exponentially between 15 and 30 degrees C, had a second peak at 35 degrees C, and decreased to about 5% of the peak activity by 40 degrees C. In tubes from one sediment sample, incubated at temperatures above 40 degrees C, an increase in the degradation rate was observed following the minimum at 40 degrees C. This suggests that at least two different organisms were involved in the transformation of 2,4-DCP to 4-CP. Storage of the original sediment slurries for 2 months at 12 degrees C resulted in increased adaptation times, but did not affect the degradation rates.

Anaerobiosis↗
PubMed1990

Sequential anaerobic degradation of 2,4-dichlorophenol in freshwater sediments.

2,4-Dichlorophenol (2,4-DCP) was anaerobically degraded in freshwater lake sediments. From observed intermediates in incubated sediment samples and from enrichment cultures, the following sequence of transformations was postulated. 2,4-DCP is dechlorinated to 4-chlorophenol (4-CP), 4-CP is dechlorinated to phenol, phenol is carboxylated to benzoate, and benzoate is degraded via acetate to methane and CO2; at least five different organisms are involved sequentially. The rate-limiting step was the transformation of 4-CP to phenol. Sediment-free enrichment cultures were obtained which catalyzed only the dechlorination of 2,4-DCP, the carboxylation of phenol, and the degradation of benzoate, respectively. Whereas the dechlorination of 2,4-DCP was not inhibited by H2, the dechlorination of 4-CP, and the transformation of phenol and benzoate were. Low concentrations of 4-CP inhibited phenol and benzoate degradation. Transformation rates and maximum concentrations allowing degradation were determined in both freshly collected sediments and in adapted samples: at 31 degrees C, which was the optimal temperature for the dechlorination, the average adaptation time for 2,4-DCP, 4-CP, phenol, and benzoate transformations were 7, 37, 11 and 2 days, respectively. The maximal observed transformation rates for these compounds in acclimated sediments were 300, 78, 2, 130, and 2,080 micromol/liter(-1)/day(-1), respectively. The highest concentrations which still allowed the transformation of the compound in acclimated sediments were 3.1 m/M 2,4-DCP, 3.1 mM 4-CP, 13 mM phenol, and greater than 52 mM benzoate. The corresponding values were lower for sediments which had not been adapted for the transformation steps.

Acetates↗
PubMed1994

Regulation of chloro- and methylphenol degradation in Comamonas testosteroni JH5.

Comamonas testosteroni JH5 was isolated from a mixed bacterial culture enriched on different chloro- and methylphenols. The strain completely mineralized a mixture consisting of 4-chlorophenol (4-CP) and 4-methylphenol (4-MP). During degradation of the mixture, 4-hydroxybenzyl alcohol, 4-hydroxybenzaldehyde, 4-hydroxybenzoic acid, and 4-chlorocatechol were detected as short-lived intermediates. Mineralization of 4-CP and that of 4-MP occurred successively and were accompanied by diauxic growth, whereas 4-CP and 2-methylphenol were mineralized simultaneously. It was ascertained that neither a reversible enzyme inhibition nor potential toxic intermediates caused the observed diauxie. Some facts support the hypothesis that the successive degradation of 4-CP and 4-MP is regulated on the level of transcription. C. testosteroni JH5 contained a meta-cleaving enzyme when pregrown on 4-CP and the isomeric monomethylphenols. Inactivation of this enzyme in the presence of 3-chlorocatechol was observed.

Biodegradation, Environmental↗
PubMed1998

Aerobic mineralization of 2,6-dichlorophenol by Ralstonia sp. strain RK1.

A new aerobic bacterium was isolated from the sediment of a freshwater pond close to a contaminated site at Amponville (France). It was enriched in a fixed-bed reactor fed with 2,6-dichlorophenol (2,6-DCP)as the sole carbon and energy source at pH 7.5 and room temperature. The degradation of 2,6-DCP followed Monod kinetics at low initial concentrations. At concentrations above 300 microM (50 mg.liter-1), 2,6-DCP increasingly inhibited its own degradation. The base sequence of the 16S ribosomal DNA allowed us to assign the bacterium to the genus Ralstonia (formerly Alcaligenes). The substrate spectrum of the bacterium includes toluene, benzene, chlorobenzene, phenol, and all four ortho- and para-substituted mono- and dichlorophenol isomers. Substituents other than chlorine prevented degradation. The capacity to degrade 2,6-DCP was examined in two fixed-bed reactors. The microbial population grew on and completely mineralized 2,6-DCP at 2,6-DCP concentrations up to 740 microM in continuous reactor culture supplied with H2O2 as an oxygen source. Lack of peroxide completely stopped further degradation of 2,6-DCP. Lowering the acid-neutralizing capacity of the medium to 1/10th the original capacity led to a decrease in the pH of the effluent from 7 to 6 and to a significant reduction in the degradation activity. A second fixed-bed reactor successfully removed low chlorophenol concentrations (20 to 26 microM) with hydraulic residence times of 8 to 30 min.

Chlorophenols↗
PubMed1999

Heat-induced expression and chemically induced expression of the Escherichia coli stress protein HtpG are affected by the growth environment.

Differences in expression of the Escherichia coli stress protein HtpG were found following exposure of exponentially growing cells to heat or chemical shock when cells were grown under different environmental conditions. With an htpG::lacZ reporter system, htpG expression increased in cells grown in a complex medium (Luria-Bertani [LB] broth) following a temperature shock at 45 degrees C. In contrast, no HtpG overexpression was detected in cells grown in a glucose minimal medium, despite a decrease in the growth rate. Similarly, in pyruvate-grown cells there was no heat shock induction of HtpG expression, eliminating the possibility that repression of HtpG in glucose-grown E. coli was due to catabolite repression. When 5 mM phenol was used as a chemical stress agent for cells growing in LB broth, expression of HtpG increased. However, when LB-grown cells were subjected to stress with 10 mM phenol and when both 5 and 10 mM phenol were added to glucose-grown cultures, repression of htpG expression was observed. 2-Chlorophenol stress resulted in overexpression of HtpG when cells were grown in complex medium but repression of HtpG synthesis when cells were grown in glucose. No induction of htpG expression was seen with 2, 4-dichlorophenol in cells grown with either complex medium or glucose. The results suggest that, when a large pool of amino acids and proteins is available, as in complex medium, a much stronger stress response is observed. In contrast, when cells are grown in a simple glucose mineral medium, htpG expression either is unaffected or is even repressed by imposition of a stress condition. The results demonstrate the importance of considering differences in growth environment in order to better understand the nature of the response to an imposed stress condition.

Bacterial Proteins↗
PubMed2002

Characterization and description of Anaeromyxobacter dehalogenans gen. nov., sp. nov., an aryl-halorespiring facultative anaerobic myxobacterium.

Five strains were isolated which form a physiologically and phylogenetically coherent group of chlororespiring microorganisms and represent the first taxon in the Myxobacteria capable of anaerobic growth. The strains were enriched and isolated from various soils and sediments based on their ability to grow using acetate as an electron donor and 2-chlorophenol (2-CPh) as an electron acceptor. They are slender gram-negative rods with a bright red pigmentation that exhibit gliding motility and form spore-like structures. These unique chlororespiring myxobacteria also grow with 2,6-dichlorophenol, 2,5-dichlorophenol, 2-bromophenol, nitrate, fumarate, and oxygen as terminal electron acceptors, with optimal growth occurring at low concentrations (<1 mM) of electron acceptor. 2-CPh is reduced by all strains as an electron acceptor in preference to nitrate, which is reduced to ammonium. Acetate, H(2), succinate, pyruvate, formate, and lactate were used as electron donors. None of the strains grew by fermentation. The 16S ribosomal DNA (rDNA) sequences of the five strains form a coherent cluster deeply branching within the family Myxococcaceae within the class Myxobacteria and are mostly closely associated with the Myxococcus subgroup. With the exception of anaerobic growth and lack of a characteristic fruiting body, these strains closely resemble previously characterized myxobacteria and therefore should be considered part of the Myxococcus subgroup. The anaerobic growth and 9.0% difference in 16S rDNA sequence from those of other myxobacterial genera are sufficient to place these strains in a new genus and species designated Anaeromyxobacter dehalogenans. The type strain is 2CP-1 (ATCC BAA-258).

Acetates↗