Biodegradation of diphenyl ether and its monohalogenated derivatives by Sphingomonas sp. strain SS3.

The bacterium Sphingomonas sp. strain SS3, which utilizes diphenyl ether and its 4-fluoro, 4-chloro, and (to a considerably lesser extent) 4-bromo derivatives as sole sources of carbon and energy, was enriched from soil samples of an industrial waste deposit. The bacterium showed cometabolic activities toward all other isomeric monohalogenated diphenyl ethers. During diphenyl ether degradation in batch culture experiments, phenol and catechol were produced as intermediates which were then channeled into the 3-oxoadipate pathway. The initial step in the degradation follows the recently discovered mechanism of 1,2-dioxygenation, which yields unstable phenolic hemiacetals from diphenyl ether structures. Oxidation of the structure-related dibenzo-p-dioxin yielded 2-(2-hydroxyphenoxy)-muconate upon ortho cleavage of the intermediate 2,2',3-trihydroxydiphenyl ether. Formation of phenol, catechol, halophenol, and halocatechol from the conversion of monohalogenated diphenyl ethers gives evidence for a nonspecific attack of the dioxygenating enzyme system.     

Metabolism of 3-methyldiphenyl ether by Sphingomonas sp. SS31

The bacterium Sphingomonas sp. SS31, which was obtained from the diphenyl ether-degrading strain Sphingomonas sp. SS3 by an adaptation process, utilized 3-methyldiphenyl ether for growth in addition to diphenyl ether. The initial enzymatic attack onto this compound proceeded by a regioselective, but non-specific dioxygenation at the carbon carrying the ether bridge and the adjacent carbon of the unsubstituted as well as the methyl-substituted aromatic nucleus. Upon spontaneous decomposition, the resulting unstable hemiacetal structure yielded 3-methylphenol and catechol, or phenol, 3-methylcatechol, and 4-methylcatechol, respectively. Phenol and 3-methylphenol were oxidized to the corresponding catechols which, after subsequent ortho-cleavage, were channeled into the oxoadipate pathway.     

Biodegradation and transformation of 4,4'- and 2,4-dihalodiphenyl ethers by Sphingomonas sp. strain SS33.

The bacterium Sphingomonas sp. strain SS33, obtained from parent diphenyl ether-mineralizing strain SS3 (S. Schmidt, R.-M. Wittich, D. Erdmann, H. Wilkes, W. Francke, and P. Fortnagel, Appl. Environ. Microbiol. 58:2744-2750, 1992) after several weeks of adaptation on 4,4'-difluorodiphenyl ether as the new target compound, also utilized 4,4'-dichlorodiphenyl ether for growth. Intermediary halocatechols were also mineralized via the ortho pathway by type I enzymes. 4,4'-Dibromodiphenyl ether was not used as a carbon source although transformation by resting cells yielded mononuclear haloaromatic compounds, such as 4-bromophenol and 4-bromocatechol. The same was true for the conversion of 2,4-dichlorodiphenyl ether, which yielded the respective (halo-) phenols and (halo-) catechols.     

Biodegradation of ether pollutants by Pseudonocardia sp. strain ENV478

A bacterium designated Pseudonocardia sp. strain ENV478 was isolated by enrichment culturing on tetrahydrofuran (THF) and was screened to determine its ability to degrade a range of ether pollutants. After growth on THF, strain ENV478 degraded THF (63 mg/h/g total suspended solids [TSS]), 1,4-dioxane (21 mg/h/g TSS), 1,3-dioxolane (19 mg/h/g TSS), bis-2-chloroethylether (BCEE) (12 mg/h/g TSS), and methyl tert-butyl ether (MTBE) (9.1 mg/h/g TSS). Although the highest rates of 1,4-dioxane degradation occurred after growth on THF, strain ENV478 also degraded 1,4-dioxane after growth on sucrose, lactate, yeast extract, 2-propanol, and propane, indicating that there was some level of constitutive degradative activity. The BCEE degradation rates were about threefold higher after growth on propane (32 mg/h/g TSS) than after growth on THF, and MTBE degradation resulted in accumulation of tert-butyl alcohol. Degradation of 1,4-dioxane resulted in accumulation of 2-hydroxyethoxyacetic acid (2HEAA). Despite its inability to grow on 1,4-dioxane, strain ENV478 degraded this compound for > 80 days in aquifer microcosms. Our results suggest that the inability of strain ENV478 and possibly other THF-degrading bacteria to grow on 1,4-dioxane is related to their inability to efficiently metabolize the 1,4-dioxane degradation product 2HEAA but that strain ENV478 may nonetheless be useful as a biocatalyst for remediating 1,4-dioxane-contaminated aquifers.     

Biodegradation of bisphenol A and related compounds by Sphingomonas sp. strain BP-7 isolated from seawater

A bacterium capable of assimilating 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), strain BP-7, was isolated from offshore seawater samples on a medium containing bisphenol A as sole source of carbon and energy, and identified as Sphingomonas sp. strain BP-7. Other strains, Pseudomonas sp. strain BP-14, Pseudomonas sp. strain BP-15, and strain no. 24A, were also isolated from bisphenol A-enrichment culture of the seawater. These strains did not degrade bisphenol A, but accelerated the degradation of bisphenol A by Sphingomonas sp. strain BP-7. A mixed culture of Sphingomonas sp. strain BP-7 and Pseudomonas sp. strain BP-14 showed complete degradation of 100 ppm bisphenol A within 7 d in SSB-YE medium, while Sphingomonas sp. strain BP-7 alone took about 40 d for complete consumption of bisphenol A accompanied by accumulation of 4-hydroxyacetophenone. On a nutritional supplementary medium, Sphingomonas sp. strain BP-7 completely degraded bisphenol A and 4-hydroxyacetophenone within 20 h. The strain degraded a variety of bisphenols, such as 1,1-bis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxy-3-methylphenyl)propane, 2,2-bis(4-hydroxyphenyl)butane, and 1,1-bis(4-hydroxyphenyl)cyclohexane, and hydroxy aromatic compounds such as 4-hydroxyacetophenone, 4-hydroxybenzoic acid, catechol, protocatechuic acid, and hydroquinone. The strain did not degrade bis(4-hydroxyphenyl)methane, bis(4-hydroxyphenyl)sulfone, or bis(4-hydroxyphenyl)sulfide.     

Biodegradation of 3-nitrotoluene by Rhodococcus sp. strain ZWL3NT

A pure bacterial culture was isolated by its ability to utilize 3-nitrotoluene (3NT) as the sole source of carbon, nitrogen, and energy for growth. Analysis of its 16S rRNA gene showed that the organism (strain ZWL3NT) belongs to the genus Rhodococcus. A rapid disappearance of 3NT with concomitant release of nitrite was observed when strain ZWL3NT was grown on 3NT. The isolate also grew on 2-nitrotoluene, 3-methylcatechol and catechol. Two metabolites, 3-methylcatechol and 2-methyl-cis,cis-muconate, in the reaction mixture were detected after incubation of cells of strain ZWL3NT with 3NT. Enzyme assays showed the presence of both catechol 1,2-dioxygenase and catechol 2,3-dioxygenase in strain ZWL3NT. In addition, a catechol degradation gene cluster (catRABC cluster) for catechol ortho-cleavage pathway was cloned from this strain and cell extracts of Escherichia coli expressing CatA and CatB exhibited catechol 1,2-dioxygenase activity and cis,cis-muconate cycloisomerase activity, respectively. These experimental evidences suggest a novel pathway for 3NT degradation with 3-methylcatechol as a key metabolite by Rhodococcus sp. strain ZWL3NT.     

Biodegradation of bis(2-chloroethyl) ether by Xanthobacter sp. strain ENV481

Degradation of bis(2-chloroethyl) ether (BCEE) was observed to occur in two bacterial strains. Strain ENV481, a Xanthobacter sp. strain, was isolated by enrichment culturing of samples from a Superfund site located in the northeastern United States. The strain was able to grow on BCEE or 2-chloroethylethyl ether as the sole source of carbon and energy. BCEE degradation in strain ENV481 was facilitated by sequential dehalogenation reactions resulting in the formation of 2-(2-chloroethoxy)ethanol and diethylene glycol (DEG), respectively. 2-Hydroxyethoxyacetic acid was detected as a product of DEG catabolism by the strain. Degradation of BCEE by strain ENV481 was independent of oxygen, and the strain was not able to grow on a mixture of benzene, ethylbenzene, toluene, and xylenes, other prevalent contaminants at the site. Another bacterial isolate, Pseudonocardia sp. strain ENV478 (S. Vainberg et al., Appl. Environ. Microbiol. 72:5218-5224, 2006), degraded BCEE after growth on tetrahydrofuran or propane but was not able to grow on BCEE as a sole carbon source. BCEE degradation by strain ENV478 appeared to be facilitated by a monooxygenase-mediated O-dealkylation mechanism, and it resulted in the accumulation of 2-chloroacetic acid that was not readily degraded by the strain.     

一株曲霉属地衣内生真菌中新的二苯醚类成分

采用硅胶柱色谱、ODS柱色谱、Sephadex LH-20柱色谱、HPLC等分离方法,从一株地衣内生真菌菌株（No. 16-20-8-1,Aspergillus sp.）的发酵物中分离得到两个二苯醚类成分。利用UV、IR、MS和NMR等波谱技术,鉴定了它们的结构,分别为：2-isopentenyldiorcinol（1）和diorcinol（2）,其中1为新化合物。     

Metabolism of dibenzo-p-dioxin by Sphingomonas sp. strain RW1.

In the course of our screening for dibenzo-p-dioxin-utilizing bacteria, a Sphingomonas sp. strain was isolated from enrichment cultures inoculated with water samples from the river Elbe. The isolate grew with both the biaryl ethers dibenzo-p-dioxin and dibenzofuran (DF) as the sole sources of carbon and energy, showing doubling times of about 8 and 5 h, respectively. Biodegradation of the two aromatic compounds initially proceeded after an oxygenolytic attack at the angular position adjacent to the ether bridge, producing 2,2',3-trihydroxydiphenyl ether or 2,2',3-trihydroxybiphenyl from the initially formed dihydrodiols, which represent extremely unstable hemiacetals. Results obtained from determinations of enzyme activities and oxygen consumption suggest meta cleavage of the trihydroxy compounds. During dibenzofuran degradation, hydrolysis of 2-hydroxy-6-oxo-6-(2-hydroxyphenyl)-hexa-2,4-dienoate yielded salicylate, which was branched into the catechol meta cleavage pathway and the gentisate pathway. Catechol obtained from the product of meta ring fission of 2,2',3-trihydroxydiphenyl ether was both ortho and meta cleaved by Sphingomonas sp. strain RW1 when this organism was grown with dibenzo-p-dioxin.     

Metabolism of dibenzo-p-dioxin by Sphingomonas sp. strain RW1.

In the course of our screening for dibenzo-p-dioxin-utilizing bacteria, a Sphingomonas sp. strain was isolated from enrichment cultures inoculated with water samples from the river Elbe. The isolate grew with both the biaryl ethers dibenzo-p-dioxin and dibenzofuran (DF) as the sole sources of carbon and energy, showing doubling times of about 8 and 5 h, respectively. Biodegradation of the two aromatic compounds initially proceeded after an oxygenolytic attack at the angular position adjacent to the ether bridge, producing 2,2',3-trihydroxydiphenyl ether or 2,2',3-trihydroxybiphenyl from the initially formed dihydrodiols, which represent extremely unstable hemiacetals. Results obtained from determinations of enzyme activities and oxygen consumption suggest meta cleavage of the trihydroxy compounds. During dibenzofuran degradation, hydrolysis of 2-hydroxy-6-oxo-6-(2-hydroxyphenyl)-hexa-2,4-dienoate yielded salicylate, which was branched into the catechol meta cleavage pathway and the gentisate pathway. Catechol obtained from the product of meta ring fission of 2,2',3-trihydroxydiphenyl ether was both ortho and meta cleaved by Sphingomonas sp. strain RW1 when this organism was grown with dibenzo-p-dioxin.     

Biodegradation of diphenyl ethers by a copper-resistant mutant ofErwinia sp.

Summary A bacterium tentatively identified as anErwinia sp. was isolated from sewage by enrichment on methanol and lignin. Several mutants developed from this strain were studied for their ability to degrade aromatic ethers. Different concentrations of the chemicals were incubated with the organisms and the degradation was estimated by high-performance liquid chromatography (HPLC). Among these mutants, one isolate,Erwinia sp. strain CU3614, showed resistance to copper ions (>20 mM CuSO₄) and the ability to degrade 4-hydroxydiphenyl ether (4-HDPE), 4-chlorodiphenyl ether (4-CDPE), 4-nitrodiphenyl ether (4-NDPE) and 2,7-dichlorodibenzo-p-dioxin (2,7-DCDD) in the presence of copper ions. Increased concentrations of copper in the medium resulted in higher degradation of 4-HDPE. Further studies with copper-sensitive mutants obtained fromErwinia sp. CU3614 by Tn5 transposon-induced mutagenesis showed a corresponding decrease in the ability to degrade 4-HDPE. These results suggest the presence of a copper-associated activity in the biotransformation of aromatic ethers.     

Biodegradation of dimethyl phthalate by Sphingomonas sp. isolated from phthalic-acid-degrading aerobic granules

This study isolated nine strains of aerobic phenol-degrading granules. These isolates (I1–I9) were characterized using 16S rRNA gene sequencing, with γ-Proteobacteria as the dominant strains in the aerobic granules. While most strains demonstrated either high phenol-degrading capabilities or auto-aggregation capabilities, three isolates, I2, I6, and I8 showed both features. These findings contradict the previous view that auto-aggregation and phenol degradation are mutually exclusive in aerobic granules. Strains I2 and I8 independently formed single-culture aerobic granules except for I3. Anti-microbial activity test results indicated that strains I2 and I8 inhibited growth of strain I3. However, co-culturing I3 with I2 or I8 helped to form granules.     

Plasmid-mediated mineralization of carbofuran by Sphingomonas sp. strain CF06.

A bacterial strain (CF06) that mineralized both the carbonyl group and the aromatic ring of the insecticide carbofuran and that is capable of using carbofuran as a sole source of carbon and nitrogen was isolated from a soil in Washington state. Phospholipid fatty acid and 16S rRNA sequencing analysis indicate that CF06 is a Sphingomonas sp. CF06 contains five plasmids, at least some of which are required for metabolism of carbofuran. Loss of the plasmids induced by growth at 42 degrees C resulted in the inability of the cured strain to grow on carbofuran as a sole source of carbon. Introduction of the plasmids confers on Pseudomonas fluorescens M480R the ability to use carbofuran as a sole source of carbon for growth and energy. Of the five plasmids, four are rich in insertion sequence elements and contain large regions of overlap. Rearrangements, deletions, and loss of individual plasmids that resulted in the loss of the carbofuran-degrading phenotype were observed following introduction of Tn5.     

Biodegradation of the sulfonylurea herbicide chlorimuron-ethyl by the strain Pseudomonas sp. LW3

Eleven carbazole (CAR)-degrading bacterial strains were isolated from seawater collected off the coast of Japan using two different media. Seven isolates were shown to be most closely related to the genera Erythrobacter, Hyphomonas, Sphingosinicella, Caulobacter , and Lysobacter . Meanwhile, strains OC3, OC6S, OC9, and OC11S showed low similarity to known bacteria, the closest relative being Kordiimonas gwangyangensis GW14-5 (90% similarity). Southern hybridization analysis revealed that only five isolates carried car genes similar to those reported in Pseudomonas resinovorans CA10 ( car _CA10) or Sphingomonas sp. strain KA1 ( car _KA1). The isolates were subjected to GC-MS and the results indicated that these strains degrade CAR to anthranilic acid.     

Mineralization of phenol and its derivatives by Pseudomonas sp. strain CP4

A Pseudomonas sp. strain, CP4, was isolated that used phenol up to 1.5 g/l as sole source of carbon and energy. Optimal growth on 1.5 g phenol/l was at pH 6.5 to 7.0 and 30°C. Unadapted cells needed 72 h to decrease the chemical oxygen demand (COD) of about 2000 mg/l (from 1 g phenol/l) to about 200 mg/l. Adapted cells, pregrown on phenol, required only 65 h to decrease the COD level to below 100 mg/l. Adaptation of cells to phenol also improved the degradation of cresols. Cell-free extracts of strain CP4 grown on phenol or o-, m- or p-cresol had sp. act. of 0.82, 0.35, 0.54 and 0.32 units of catechol 2,3-dioxygenase and 0.06, 0.05, 0.05 and 0.03 units of catechol 1,2-dioxygenase, respectively. Cells grown on glucose or succinate had neither activity. Benzoate and all isomers of cresol, creosote, hydroxybenzoates, catechol and methyl catechol were utilized by strain CP4. No chloroaromatic was degraded, either as sole substrate or as co-substrate.The authors are with the Department of Microbiology and Bioengineering, Central Food Technological Research Institute, Mysore-570 013, India     

Biodegradation of monohalogenated alkanes by soil NH(3)-oxidizing bacteria

Although cooxidative biodegradation of monohalogenated hydrocarbons has been well studied in the model NH₃-oxidizing bacterium, Nitrosomonas europaea, virtually no information exists about cooxidation of these compounds by native populations of NH₃-oxidizing bacteria. To address this subject, nitrifying activity was stimulated to 125–400 nmol NO₃ ^– produced g^–1 soil h^–1 by first incubating a Ca(OH)₂-amended, silt loam soil (pH 7.0±0.2) at field capacity (270 g H₂O kg^–1 soil) with 10 μmol NH₄ ⁺ g^–1 soil for 14 days, followed by another 10 days of incubation in a shaken slurry (2:1 water:soil, v/w) with periodic pH adjustment and maintenance of 10 mM NH₄ ⁺. These slurries actively degraded both methyl bromide (MeBr) and ethyl chloride (EtCl) at maximum rates of 20–30 nmol ml^–1 h^–1 that could be sustained for approximately 12 h. Although the MeBr degradation rates were linear for the first 10–12 h of incubation, they could not be sustained regardless of NH₄ ⁺ level and declined to zero over 20 h of incubation. The transformation capacity of the slurry enrichments (~1 μmol MeBr ml^–1 soil slurry) was similar to the value measured previously in cell suspensions of N. europaea with similar NH₃-oxidizing activity. Several MeBr-degrading characteristics of the nitrifying enrichments were found to be similar to those documented in the literature for MeBr-degrading methanotrophs and facultatively methylotrophic bacteria. Electronic Publication     

Biotransformation of fluorene, diphenyl ether, dibenzo-p-dioxin and carbazole by Janibacter sp.

Fluorene, diphenyl ether, dibenzo-p-dioxin, and carbazole were used by a dibenzofuran-utilizing Janibacter sp. strain YY-1. Metabolites were identified by GC-MS. Angular dioxygenation was the major pathway for degradation of fluorene, diphenyl ether, and dibenzo-p-dioxin but not for carbazole. Lateral dioxygenation of all tested compounds was indicated by the detection of mono- or di-hydroxylated compounds. The bacterium also catalyzed the monooxygenation of fluorene at the C9 position.     

Biodegradation of 2-nitrotoluene by Pseudomonas sp. strain JS42.

A strain of Pseudomonas sp. was isolated from nitrobenzene-contaminated soil and groundwater on 2-nitrotoluene as the sole source of carbon, energy, and nitrogen. Bacterial cells growing on 2-nitrotoluene released nitrite into the growth medium. The isolate also grew on 3-methylcatechol, 4-methylcatechol, and catechol. 2-Nitrotoluene, 3-methylcatechol, and catechol stimulated oxygen consumption by intact cells regardless of the growth substrate. Crude extracts from the isolate contained catechol 2,3-dioxygenase and 2-hydroxy-6-oxohepta-2,4-dienoate hydrolase activity. The results suggest that 2-nitrotoluene is subject to initial attack by a dioxygenase enzyme that forms 3-methylcatechol with concomitant release of nitrite. The 3-methylcatechol is subsequently degraded via the meta ring fission pathway.