Degradation of Mono-chlorinated Dibenzo-p-Dioxins by Janibacter sp. Strain YA Isolated from River Sediment

Strain YA was newly isolated from an enrichment culture of river sediment and was identified as Janibacter sp. It was able to utilize dibenzofuran as the sole source of carbon and energy. Strain YA degraded > 90% of 1-chloro-dibenzo-p-dioxin (1-CDD) and > 80% of 2-chloro-dibenzo-p-dioxin in 18 hours with each initial concentration at 40 mg/L. A novel metabolite, 2-chloro-2′,6-dihydroxydiphenylether, was observed in 1-CDD degradation. From the metabolites detected by gas chromatography–mass spectrometry, strain YA was supposed to have at least two types of oxidation pathways in 1-CDD degradation.     

Aerobic Degradation of N-Methyl-4-Nitroaniline (MNA) by Pseudomonas sp. Strain FK357 Isolated from Soil

N-Methyl-4-nitroaniline (MNA) is used as an additive to lower the melting temperature of energetic materials in the synthesis of insensitive explosives. Although the biotransformation of MNA under anaerobic condition has been reported, its aerobic microbial degradation has not been documented yet. A soil microcosms study showed the efficient aerobic degradation of MNA by the inhabitant soil microorganisms. An aerobic bacterium, Pseudomonas sp. strain FK357, able to utilize MNA as the sole carbon, nitrogen, and energy source, was isolated from soil microcosms. HPLC and GC-MS analysis of the samples obtained from growth and resting cell studies showed the formation of 4-nitroaniline (4-NA), 4-aminophenol (4-AP), and 1, 2, 4-benzenetriol (BT) as major metabolic intermediates in the MNA degradation pathway. Enzymatic assay carried out on cell-free lysates of MNA grown cells confirmed N-demethylation reaction is the first step of MNA degradation with the formation of 4-NA and formaldehyde products. Flavin-dependent transformation of 4-NA to 4-AP in cell extracts demonstrated that the second step of MNA degradation is a monooxygenation. Furthermore, conversion of 4-AP to BT by MNA grown cells indicates the involvement of oxidative deamination (release of NH₂ substituent) reaction in third step of MNA degradation. Subsequent degradation of BT occurs by the action of benzenetriol 1, 2-dioxygenase as reported for the degradation of 4-nitrophenol. This is the first report on aerobic degradation of MNA by a single bacterium along with elucidation of metabolic pathway.     

Synthesis of 2-(4-Hydroxyphenyl)naphthalene-1,8-dicarboxylic Anhydride,a Phytoalexin Isolated from Unripe Banana (Musa acuminata)

2-(4-Hydroxyphenyl)naphthalene-1,8-dicarboxylic anhydride, a component of the phytoalexin that has been isolated from the peel of unripe banana (Musa acuminata), was synthesized from 3-bromoacenaphthene.     

Degradation of Bromoxynil Octanoate by Strain Acinetobacter sp. XB2 Isolated from Contaminated Soil

Bromoxynil octanoate (BOO), the most widespread herbicide applied to maize, is potentially toxic to both animals and humans. In this article, a highly effective BOO-degrading bacterial strain, XB2, was isolated from the soil of a herbicide factory. The strain was identified as an Acinetobacter sp. based on its 16S rRNA gene sequence analysis, morphological, physiological, and biochemical properties. This strain could use BOO as its sole carbon source and could degrade 100?mg?l(-1) BOO to non-detectable levels in 72?h (h). The optimal pH and temperature for strain XB2's growth and degradation of BOO in MSM are 7.0 and 30°C, respectively. We propose the following pathway of BOO degradation by strain XB2: the first step is the scission of the ester bond to form bromoxynil, bromoxynil then transformed to 3,5-dibromo-4-hydroxybenzoic acid?due to the hydrolysis of nitriles, and debromination finally results in the formation of 3-bromo-4-hydroxybenzoic acid. Inoculating BOO-treated soil samples with strain XB2 resulted in a higher rate of BOO degradation than in non-inoculated soil, regardless of whether the soil had previously been sterilized.     

Degradation of Fumonisin B1 by a Bacterial Strain Isolated from Soil

A mixed microbial culture degrading fumonisin B l was obtained from soil samples using an enrichment culture procedure. A bacterial isolate from the enrichment culture (strain NCB 1492) degraded fumonisin B1 after incubation for 3 h, as indicated by TLC and HPLC analysis. On the basis of the sequence analysis of 16S rDNA, strain NCB 1492 was related to the Delftia/Comamonas group. Thin-layer chromatographic analysis indicated the presence of metabolites in the NCB 1492 culture filtrates after degradation of fumonisin B1 supplied as sole carbon and nitrogen source in phosphate buffer. Four metabolites were identified by mass spectrometry analysis.     

Degradation of Dimethyl Isophthalate by Viarovorax paradoxus Strain T4 Isolated from Deep-Ocean Sediment of the South China Sea

Viarovorax paradoxusT4 strain was isolated from deep-ocean sediment and demonstrated to be able to degrade dimethyl isophthalate (DMI). When DMI was utilized as the sole source of carbon and energy, it was transformed by hydrolysis initially, forming monomethyl isophthalate (MMI) and isophthalate acid (IA) as degradation intermediates. DMI and MMI were completely transformed to MMI and IA in about 100 h, respectively. Degradation of IA was completed in about 55 h. Analysis of total organic carbon in the culture medium confirmed that more than 80% of the substrate carbon was mineralized. Bacterial esterase induced by a range of substrates could be assessed using p-nitrophenyl acetate as the common substrate using crude enzyme preparation. The decreasing trend of K _m values derived from the Michaelis–Menten equation was dimethyl phthalate (DMP) > monomethyl phthalate (MMP) > dimethyl terephthalate (DMT) > Liver esterase > DMI > MMI > monomethyl terephthalate (MMT), indicating that higher K _m values were obtained by di-esters than mono-ester and the esters induced by terephthalate esters showed the highest activity. This investigation suggests that biochemical pathways for phthalate esters share many common characteristics and the esterases induced by different substrates are highly specific.     

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.     

Degradation and Detoxification of Nicosulfuron by a Pseudomonas Strain Isolated from a Contaminated Cornfield Soil

ABSTRACT

The dissipation and detoxification of nicosulfuron (NS) by Pseudomonas aeruginosa B9 isolated from a cornfield soil was investigated. The fastest decline of NS occurred at 40 µg ml^?1 in liquid media with 0.25% glucose plus 0.05% yeast extract (DT₅₀ = 4 days) with a notable pH reduction (pH ? 5). Bioassay tests showed considerable phytotoxicity of NS for Cress (Lepidium sativum L.) with 50% shoot growth inhibition (SGI) at 40 µg ml^?1. The dissipation of NS (40 µg ml^?1) by the B9 isolate reduced the SGI significantly (SGI: up to 45 ± 3%) compared to the non-inoculated media (SGI: up to 58 ± 4%). In soils with the B9 isolate, NS dissipation, especially at 0.3 µg g^?1, was faster with a more significant SGI reduction (k = 0.08 ± 0.00 day^?1; SGI = 2 ± 1%) compared to non-inoculated samples (k = 0.03 ± 0.00 day^?1; SGI = 8 ± 1%). NS initially inhibited soil respiration, microbial biomass carbon, and dehydrogenase activity. The effect was however transient, and these parameters recovered within 10 days, especially in the presence of the isolate. Overall, this study proves Pseudomonas aeruginosa B9 as a suitable candidate for bioremediation of NS in contaminated sites.     

Cyanide Degradation under Alkaline Conditions by a Strain of Fusarium solani Isolated from Contaminated Soils

Several cyanide-tolerant microorganisms have been selected from alkaline wastes and soils contaminated with cyanide. Among them, a fungus identified as Fusarium solani IHEM 8026 shows a good potential for cyanide biodegradation under alkaline conditions (pH 9.2 to 10.7). Results of K(sup14)CN biodegradation studies show that fungal metabolism seems to proceed by a two-step hydrolytic mechanism: (i) the first reaction involves the conversion of cyanide to formamide by a cyanide-hydrolyzing enzyme, cyanide hydratase (EC 4.2.1.66); and (ii) the second reaction consists of the conversion of formamide to formate, which is associated with fungal growth. No growth occurred during the first step of cyanide degradation, suggesting that cyanide is toxic to some degree even in cyanide-degrading microorganisms, such as F. solani. The presence of organic nutrients in the medium has a major influence on the occurrence of the second step. Addition of small amounts of yeast extract led to fungal growth, whereas no growth was observed in media containing cyanide as the sole source of carbon and nitrogen. The simple hydrolytic detoxification pathway identified in the present study could be used for the treatment of many industrial alkaline effluents and wastes containing free cyanide without a prior acidification step, thus limiting the risk of cyanhydric acid volatilization; this should be of great interest from an environmental and health point of view.     

Degradation of Cyanophycin by Sedimentibacter hongkongensis Strain KI and Citrobacter amalonaticus Strain G Isolated from an Anaerobic Bacterial Consortium

Using a combination of various enrichment techniques, the strictly anaerobic, gram-positive, endospore-forming bacterium Sedimentibacter hongkongensis strain KI as revealed by 16S rRNA analysis and the gram-negative enterobacterium Citrobacter amalonaticus strain G as revealed by physiological tests were isolated from an anaerobic cyanophycin (CGP)-degrading bacterial consortium. S. hongkongensis strain KI is the first anaerobic bacterium with the ability to hydrolyze CGP to β-Asp-Arg and β-Asp-Lys dipeptides, as revealed by electrospray ionization-mass spectrometry and reversed-phase high-performance liquid chromatography analysis. However, these primary accumulated hydrolysis products were only partially used by S. hongkongensis strain KI, and significant growth on CGP did not occur. On the other hand, C. amalonaticus strain G did not degrade CGP but grew on the β-linked iso-dipeptides formed in vitro by enzymatic CGP degradation or in vivo by metabolic activity of S. hongkongensis strain KI. Dipeptide utilization occurred at the highest rate if both strains were used in cocultivation experiments with CGP, indicating that cooperation between different bacteria occurs in anaerobic natural environments for complete CGP turnover. The amino acids obtained from the cleavage of dipeptides were fermented to ethanol, acetic acid, and succinic acid, as revealed by gas chromatographic analysis and by spectrophotometric enzyme assays.     

Degradation of Fluorobenzene by Rhizobiales Strain F11 via ortho Cleavage of 4-Fluorocatechol and Catechol

The aerobic metabolism of fluorobenzene by Rhizobiales sp. strain F11 was investigated. Liquid chromatography-mass spectrometry analysis showed that 4-fluorocatechol and catechol were formed as intermediates during fluorobenzene degradation by cell suspensions. Both these compounds, unlike 3-fluorocatechol, supported growth and oxygen uptake. Cells grown on fluorobenzene contained enzymes for the ortho pathway but not for meta ring cleavage of catechols. The results suggest that fluorobenzene is predominantly degraded via 4-fluorocatechol with subsequent ortho cleavage and also partially via catechol.     

Poly(Aspartic Acid) Degradation by a Sphingomonas sp. Isolated from Freshwater

A poly(aspartic acid) degrading bacterium (strain KT-1 [JCM10459]) was isolated from river water and identified as a member of the genus Sphingomonas. The isolate degraded only poly(aspartic acid)s of low molecular masses (<5 kDa), while the cell extract hydrolyzed high-molecular-mass poly(aspartic acid)s of 5 to 150 kDa to yield aspartic acid monomer.     

Coriolus versicolor Laccase Catalyzes the Decarboxylation of 2-(4-Hydroxyphenyl)-glycine and 4-Hydroxymandelic Acid

Cyclodextrin glucanotransferase [1,4-α-D-glucan 4-α-D-(l,4-α-D-glucano)-transferase (cyclizing), EC 2.4.1.19] from an alkalophilic Bacillus species A2–5a had a wider acceptor specificity than that from B. macerans, which was similar to those from B. stearo-thermophilus and B. circulans.

Glucosyl rhamnose produced by the CGTase was identified as glucopyranosyl-α-l,4-rhamnopyranose by α- and β-glucosidase treatments, and ¹H- and ^{1 3}C-NMR analyses.     

Characterization of Methanococcus voltaei Strain P2F9701a: A New Methanogen Isolated from Estuarine Environment

A new methanogen, designated as strain P2F9701a (= OCM 745), was isolated from a water sample of estuarine environment in Elrin Shi, Taiwan. Cells of strain P2F9701a were motile coccus (0.7∼1.1 μm) with tufts of flagella. Gas vacuoles were observed, and the protein cell wall was composed of S-layer protein subunit with M_r of 74,700. Cells catabolized formate and H₂+CO₂ to produce methane, but not acetate, methanol, and trimethylamine. Strain P2F9701a grew in the range of 30–42°C, with optimal growth temperature at 37°C, but did not grow below 28°C or above 42°C. This estuarine isolate P2F9701a tolerated well the NaCl concentration between 0.02 and 1.03 m, and the optimal salt for growth was 0.17 m. Although phylogenetic analytic results indicated that P2F9701a belongs to the mesophilic, hydrogenotrophic marine methanogen of Methanococcus voltaei, the occurrence of gas vacuoles, tufts of flagella, eury-halotolerant and steno-thermotolerant characters of strain P2F9701a are different from mesophilic Methanococcus spp. that had been reported. Received: 19 October 2000 / Accepted: 17 November 2000     

薯蓣内生真菌抗氧化活性的初步研究

用碘量法研究了4株薯蓣内生真菌的发酵液和菌丝的抗氧化活性。结果表明,4株菌株的菌丝和发酵液具有不同的抗氧化活性,其中从薯蓣块茎中分离得到菌株EDT5发酵液的抗氧化活性最强,从薯蓣种子中分离得到菌株EDS4发酵液的抗氧化活性次之,并且在一定范围内,随着发酵液粗提物浓度的增加,其抗氧化活性增强。EDT5和EDS4发酵液的抗氧化效果高于或近于其宿主薯蓣而高于维生素E的抗氧化效果,表明内生真菌是天然抗氧化产物开发的潜在重要资源之一。     

Metabolic Pathway Involved in 2-Methyl-6-Ethylaniline Degradation by Sphingobium sp. Strain MEA3-1 and Cloning of the Novel Flavin-Dependent Monooxygenase System meaBA

2-Methyl-6-ethylaniline (MEA) is the main microbial degradation intermediate of the chloroacetanilide herbicides acetochlor and metolachlor. Sphingobium sp. strain MEA3-1 can utilize MEA and various alkyl-substituted aniline and phenol compounds as sole carbon and energy sources for growth. We isolated the mutant strain MEA3-1Mut, which converts MEA only to 2-methyl-6-ethyl-hydroquinone (MEHQ) and 2-methyl-6-ethyl-benzoquinone (MEBQ). MEA may be oxidized by the P450 monooxygenase system to 4-hydroxy-2-methyl-6-ethylaniline (4-OH-MEA), which can be hydrolytically spontaneously deaminated to MEBQ or MEHQ. The MEA microbial metabolic pathway was reconstituted based on the substrate spectra and identification of the intermediate metabolites in both the wild-type and mutant strains. Plasmidome sequencing indicated that both strains harbored 7 plasmids with sizes ranging from 6,108 bp to 287,745 bp. Among the 7 plasmids, 6 were identical, and pMEA02′ in strain MEA3-1Mut lost a 37,000-bp fragment compared to pMEA02 in strain MEA3-1. Two-dimensional electrophoresis (2-DE) and protein mass fingerprinting (PMF) showed that MEA3-1Mut lost the two-component flavin-dependent monooxygenase (TC-FDM) MeaBA, which was encoded by a gene in the lost fragment of pMEA02. MeaA shared 22% to 25% amino acid sequence identity with oxygenase components of some TC-FDMs, whereas MeaB showed no sequence identity with the reductase components of those TC-FDMs. Complementation with meaBA in MEA3-1Mut and heterologous expression in Pseudomonas putida strain KT2440 resulted in the production of an active MEHQ monooxygenase.     

Degradation of 2,4,6-Trinitrophenol (TNP) by Arthrobacter sp. HPC1223 Isolated from Effluent Treatment Plant

Arthrobacter sp. HPC1223 (Genebank Accession No. AY948280) isolated from activated biomass of effluent treatment plant was capable of utilizing 2,4,6 trinitrophenol (TNP) under aerobic condition at 30 °C and pH 7 as nitrogen source. It was observed that the isolated bacteria utilized TNP up to 70 % (1 mM) in R2A media with nitrite release. The culture growth media changed into orange-red color hydride-meisenheimer complex at 24 h as detected by HPLC. Oxygen uptake of Arthrobacter HPC1223 towards various nitro/amino substituted phenols such as dinitrophenol (1.2 nmol/min/mg cells), paranitrophenol (0.9 nmol/min/mg cells), 2-aminophenol (0.75 nmol/min/mg cells), p-aminophenol (0.4 nmol/min/mg cells), phenol (0.56 nmol/min/mg cells) and TNP (2.42 nmol/min/mg cell) was analysed, which showed its additional characteristic of broad substrate catabolic capacity. The present study thus report a novel indigenous bacteria isolated from activated sludge utilized TNP and has broad catabolic potential towards substituted phenols.