Degradation of chloroanilines in soil slurry by specialized organisms

The microbial degradation of 2-chloro-, 3-chloro-, 4-chloro-, and 3,4-dichloroaniline was examined as single compounds as well as a mixture in soil slurries. At 30°C the degradation of chloroanilines by indigenous soil populations in soil slurries was observed when soil slurry was freshly contaminated or precontaminated to allow binding of chloroanilines to the soil matrix. Within 6 weeks, 3-chloro- and 3,4-dichloroaniline (each 2 mm) were degraded more rapidly (about 50% chloride elimination) than 4-chloro- and 2-chloroaniline, due to stronger adsorption of 4-chloroaniline and greater resistance of 2-chloroaniline. The addition of various supplements such as buffer, mineral salts and acetate only slightly influenced the degradation of chloroanilines by the indigenous soil populations. The mineralization was drastically enhanced when laboratory-selected chloroaniline-degraders (8·10⁶ cells/g) such as Pseudomonas acidovorans strain BN3.1 were supplemented to the soil slurries so that complete elimination of chloride from the chloroanilines occurred within 10 days. Correspondence to: F. R. Brunsbach     

Degradation of chlorobenzenes in soil slurry by a specialized organism

The microbial degradation of monochloro-, 1,2-dichloro-, 1,4-dichloro-, and 1,2,4-trichlorobenzene in soil slurries was examined with single compounds as well as in mixtures. The indigenous soil populations brought about the degradation of monochlorobenzene when incubated at 27°C in slurries with 29% (w/w) suspended solids. In contrast, the other chlorobenzenes persisted during an incubation period of 1 month. Supplementation with buffer, mineral salts and acetate did not significantly influence the degradation. However, inoculation withPseudomonas aeruginosa strain RHO1, a monochloro- and 1,4-dichlorobenzene-degrading organism, to a titre of 1 × 10⁵ cells/g soil, led to rapid and complete degradation of 0.8 mm growth substrate within 30 h. In addition, the strain was able to degrade 1,2-dichloro- and 1,2,4-trichlorobenzene with stoichiometric release of chloride in the presence of acetate, ethanol, monochloro- or 1,4-dichlorobenzene as growth substrates. In mixtures of chlorobenzenes the co-metabolism of 1,2-dichloro- and 1,2,4-trichlorobenzene occurred until the growth substrates monochloroand 1,4-dichlorobenzene were degraded. The degradation was faster in the slurries of garden soil containing 8% organic carbon than in soil with the lower content of 2.6%.     

Mineralization of low-chlorinated biphenyls by Burkholderia sp. strain LB400 and by a two-membered consortium upon directed interspecies transfer of chlorocatechol pathway genes

The biphenyl-mineralizing bacterium Burkholderia sp. strain LB400 also utilized 3-chloro-, 4-chloro-, 2,3′-dichloro- and 2,4′-dichlorobiphenyl for growth. By the attack of the initial enzyme a chlorine was eliminated dioxygenolytically from position 2 of one of the aromatic rings when hydrogens of both were substituted by chlorine. The strain mineralized 3-chloro- and 2,3′-dichlorobiphenyl via the central intermediate 3-chlorobenzoate through its chlorocatechol pathway enzymes, but excreted stoichiometric amounts of 4-chlorobenzoate from 4-chloro- and 2,4^′-dichlorobiphenyl. These two compounds were mineralized by a co-culture of strain LB400 and a derivative of the (methyl-) benzoate-degrading strain Pseudomonas putida mt-2 (TOL). The complete degradation was achieved upon transfer of a cluster of at least five genes, encoding the regulated chlorocatechol pathway operon, from strain LB400 to strain mt-2. This transfer was demonstrated by the polymerase chain reaction. Received: 15 April 1998 / Received revision: 12 June 1998 / Accepted: 19 June 1998     

Opioid Peptides from Human β-Casein

A bacterium that assimilates 2,3-dichloro-1-propanol was isolated from soil by enrichment culture. The strain was identified as Pseudomonas sp. by the taxonomic studies. The strain converted 2,3-dichloro-1-propanol to 3-chloro-1,2-propanediol, releasing chloride ion. The conversion was stereospecific because the residual 2,3-dichloro-1-propanol and formed 3-chloro-1,2-propanediol gave optical rotation. The resting cells converted various halohydrins to the dehalogenated alcohols, and cell-free extracts had strong epoxyhydrolase activity. These results indicated that the strain assimilated 2,3-dichloro-1-propanol via 3-chloro-1,2-propanediol, glycidol, and glycerol. The possibility to manufacture optically active 2,3-dichloro-1-propanol is discussed.     

Degradation of 2-chlorobenzoic and 2,5-dichlorobenzoic acids in pure culture byPseudomonas stutzeri

A strain ofPseudomonas stutzeri KS25 utilizing 2-chlorobenzoic and 2,5-dichlorobenzoic acids as the sole carbon and energy source was isolated from polychlorophenol-contaminated soil and sewage, using the method of enrichment cultures. This strain was also able to grow on 2-fluoro-, 2-iodo-, 2-bromo- and 2,5-dihydroxybenzoate, but did not utilize 3-, 4-chloro-, 2,4- and 2,6-dichlorobenzoates as the sole carbon and energy source, however, it cometabolized 3-chloro-, 2,4-and 2,6-dichlorobenzoates, but not 4-chlorobenzoate. The yield of released chlorine during utilization of 2-chloro- and 2,5-dichlorobenzoates amounted to 100 % of the theoretical. The concentration of 2-chloro- and 2,5-dichlorobenzoates, not substantially inhibiting the isolated microorganism, was within the range 0.25–0.5 and 2.5–3.0 g/L, respectively.     

Production of 3,4-dihalogenated catechols from toluene and benzoate analogues by Pseudomonas putida strain PaW1

Summary 3,4-Dichloro-, 3-bromo-4-chloro- and 3-chloro-4-bromocatechnol have been formed by co-oxidation of the respective toluenes and benzoates. Acetate, toluene and p-xylene were tested as growth substrates for Pseudomonas putida strain PaWl with respect to the suitability for good co-oxidation. The influence of various parameters such as cell density, concentration of substrate, salts and phosphate, pH value and temperature on the production of 3,4-dichlorocatechol was tested. Besides the production of 3,4-dichlorocatechol by resting cells of P. putida PaWl, equipment for the continuous formation and extraction of the product was established.Offprint requests to: W. Reineke     

Biodegradation Kinetics of Four Substituted Chlorobenzoic Acids by Enterobacter aerogenes

Enterobacter aerogenes is generally found in soil, sewage plants, and human gastrointestinal tract. Thus, this study was conducted to evaluate the ability of Enterobacter aerogenes to degrade four chlorobenzoic acid compounds (2-chlorobenzoic acid (2-CBA), 3-chlorobenzoic acid (3-CBA), 4-chlorobenzoic acid (4-CBA), and 3,4-dichlorobenzoic acid (3,4-dCBA)) in minimal salt medium. Enterobacter aerogenes was partially able to degrade and dechlorinate these CBAs at concentration of 3.5 mM within 72 h of incubation. According to Haldane single-substrate model, the values of maximum predicted growth rate (μ_max), half saturation constant (K _s), and inhibition constant (K _i) fell in the range of 0.2–0.8 h^?1, 8–41 mM, and 5–53 mM, respectively. Based on the estimated values of both α, a growth-associated constant, and β, a non–growth-associated constant, the production of chloride was predominantly growth associated, since negligible values of the β were determined. Haldane model gave a good prediction of the CBA substrate utilization and degradation, and was in a very good agreement with the experimental data. Because of the capability of Enterobacter aerogenes to utilize these aromatic compounds as carbon and energy sources, this microorganism can be a valuable and promising candidate for use in the biotreatment of wastewater and soil samples contaminated with mixtures of chlorobenzoates.     

Toxicity of diesel fuel to germination,growth and colonization of <Emphasis Type="Italic">Glomus intraradices</Emphasis> in soil and <Emphasis Type="Italic">in vitro</Emphasis> transformed carrot root cultures

Phytoremediation is the use of selected plants to decontaminate polluted environments. Arbuscular mycorrhizal fungi (AMF) may potentially be useful for phytoremediation, but it is not known how petroleum hydrocarbons influence AMF spore germination and hyphal growth. To address this question, germination of spores and germ tube growth of Glomus intraradices Schenck and Smith and Glomus aggregatum Schenck and Smith were assessed in soil contaminated with up to 3% (w/v) of F2 diesel oil or HAGO reference oil. Hyphal growth, colonization and progeny spore production were assessed in vitro using transformed root cultures of Daucus carota and G. intraradices spores in a F2 diesel contaminated medium. In addition, extraradical hyphal growth of G. intraradices colonizing Daucus carota in the presence of F2 diesel was studied. Neither F2 diesel nor HAGO reference oil affected spore germination or germ tube growth in soil. However, in the presence of plant roots, germ tube growth of G. intraradices was reduced and delayed in the presence of F2 diesel and root colonization was not detected. Hyphal growth of pre-colonized carrot roots by G. intraradices was reduced and delayed in F2 contaminated medium compared to controls. F2 diesel did not inhibit spore germination of these AMF species but did reduce colonization, germ tube and hyphal growth. These results suggest that AMF inoculum can be established in petroleum-contaminated sites. However, it may prove beneficial to plant pre-colonized plants to increase the probability of sufficient AMF colonization and growth. The likely mechanism(s) of petroleum toxicity in this plant-microbe system was discussed.     

Alleviation of salt stress by plant growth regulators and IAA producing bacteria in wheat

The action of phytohormone producing bacteria and plant growth regulators on germination and seedling growth of wheat under saline conditions were studied. Seed dormancy enforced by salinity (100 mM NaCl) was substantially alleviated and the germination was promoted by gibberellin, auxin, zeatin, and ethephon from 54 to 97%. The IAA producing bacterial strains Pseudomonas aureantiaca TSAU22, Pseudomonas extremorientalis TSAU6 and Pseudomonas extremorientalis TSAU20 significantly increased seedling root growth up to 25% in non-salinated conditions and up to 52% at 100 mM NaCl, compared to control plants. It is concluded that growth regulators considerably alleviated salinity-induced dormancy of wheat seeds. The facts mentioned above make it possible to recommend root colonizing bacteria that produce phytohormone to alleviate salt stress of wheat grown under conditions of soil salinity.     

Metabolism of dichloromethylcatechols as central intermediates in the degradation of dichlorotoluenes by Ralstonia sp. strain PS12

Ralstonia sp. strain PS12 is able to use 2,4-, 2,5-, and 3,4-dichlorotoluene as growth substrates. Dichloromethylcatechols are central intermediates that are formed by TecA tetrachlorobenzene dioxygenase-mediated activation at two adjacent unsubstituted carbon atoms followed by TecB chlorobenzene dihydrodiol dehydrogenase-catalyzed rearomatization and then are channeled into a chlorocatechol ortho cleavage pathway involving a chlorocatechol 1,2-dioxygenase, chloromuconate cycloisomerase, and dienelactone hydrolase. However, completely different metabolic routes were observed for the three dichloromethylcatechols analyzed. Whereas 3,4-dichloro-6-methylcatechol is quantitatively transformed into one dienelactone (5-chloro-2-methyldienelactone) and thus is degraded via a linear pathway, 3,5-dichloro-2-methylmuconate formed from 4,6-dichloro-3-methylcatechol is subject to both 1,4- and 3,6-cycloisomerization and thus is degraded via a branched metabolic route. 3,6-Dichloro-4-methylcatechol, on the first view, is transformed predominantly into one (2-chloro-3-methyl-trans-) dienelactone. In situ (1)H nuclear magnetic resonance analysis revealed the intermediate formation of 2,5-dichloro-4-methylmuconolactone, showing that both 1,4- and 3,6-cycloisomerization occur with this muconate and indicating a degradation of the muconolactone via a reversible cycloisomerization reaction and the dienelactone-forming branch of the pathway. Diastereomeric mixtures of two dichloromethylmuconolactones were prepared chemically to proof such a hypothesis. Chloromuconate cycloisomerase transformed 3,5-dichloro-2-methylmuconolactone into a mixture of 2-chloro-5-methyl-cis- and 3-chloro-2-methyldienelactone, affording evidence for a metabolic route of 3,5-dichloro-2-methylmuconolactone via 3,5-dichloro-2-methylmuconate into 2-chloro-5-methyl-cis-dienelactone. 2,5-Dichloro-3-methylmuconolactone was transformed nearly exclusively into 2-chloro-3-methyl-trans-dienelactone.     

Anaerobic biodegradation of pentachlorophenol in a contaminated soil inoculated with a methanogenic consortium or with Desulfitobacterium frappieri strain PCP-1

Anaerobic biodegradation of pentachlorophenol (PCP) in a contaminated soil from a wood-treating industrial site was studied in soil slurry microcosms inoculated with a PCP-degrading methanogenic consortium. When the microcosms containing 10%–40% (w/v) soil were inoculated with the consortium, more than 90% of the PCP was removed in less than 30 days at 29 °C. Less-chlorinated phenols, mainly 3-chlorophenol were slowly degraded and accumulated in the cultures. Addition of glucose and sodium formate to the microcosms was not necessary, suggesting that the organic compounds in the soil can sustain the dechlorinating activity. Inoculation of Desulfitobacterium frappieri strain PCP-1 along with a 3-chlorophenol-degrading consortium in the microcosms also resulted in the rapid dechlorination of PCP and the slow degradation of 3-chlorophenol. Competitive polymerase chain reaction experiments showed that PCP-1 was present at the same level throughout the 21-day biotreatment. D. frappieri, strain PCP-1, inoculated into the soil microcosms, was able to remove PCP from soil containing up to 200 mg PCP/kg soil. However, reinoculation of the strain was necessary to achieve more than 95% PCP removal with a concentration of 300 mg and 500 mg PCP/kg soil. These results demonstrate that D. frappieri strain PCP-1 can be used effectively to dechlorinate PCP to 3-chlorophenol in contaminated soils. Received: 14 November 1997 / Received revision: 29 January 1998 / Accepted: 24 February 1998     

Degradation of polychlorinated phenols by Streptomyces rochei 303

The strain Streptomyces rochei 303 (VKM Ac-1284D) is capable of utilizing 2-chloro-,2,4-,2,6-dichloro- and 2,4,6-trichlorophenols as the sole source of carbon. Its resting cells completely dechlorinated and degraded 2-, 3-chloro-; 2,4-, 2,6-, 2,3-, 2,5-, 3,4-, 3,5-dichloro-; 2,4-, 2,6-dibromo-; 2,4,6-, 2,4,5-, 2,3,4-, 2,3,5-, 2,3,6-trichlorophenols; 2,3,5,6-tetrachloro- and pentachlorophenol. During chlorophenol degradation, a stoichiometric amount of chloride ions was released and chlorohydroquinols were formed as intermediates. In cell-free extracts of S. rochei, the activity of hydroxyquinol 1,2-dioxygenase was found. The enzyme was induced with chlorophenols. Of all so far described strains degrading polychlorophenols, S. rochei 303 utilized a wider range of chlorinated phenols as the sole sourse of carbon and energy.Abbreviations CP chlorophenol - DCP dichlorophenol - TCP trichlorophenol - TeCP tetrachlorophenol - PCP pentachlorophenol - DBrP dibromophenol - CHQ chlorohydroquinol - DCHQ dichlorohydroquinol - HHQ hydroxyhydroquinol - CHHQ chlorohydroxyhydroquinol - CC chlorocatechol - TLC thin layer chromatography - GC/MC chromato-mass-spectrometry - HPLC high-performance liquid chromatography     

Effect of bacterial inoculation of strains of pseudomonas aeruginosa,alcaligenes feacalis and bacillus subtilis on germination,growth and heavy metal (cd,cr, and ni) uptake of brassica juncea

Bacterial inoculation may influence Brassica juncea growth and heavy metal (Ni, Cr, and Cd) accumulation. Three metal tolerant bacterial isolates (BCr3, BCd33, and BNi11) recovered from mine tailings, identified as Pseudomonas aeruginosa KP717554, Alcaligenes feacalis KP717561, and Bacillus subtilis KP717559 were used. The isolates exhibited multiple plant growth beneficial characteristics including the production of indole-3-acetic acid, hydrogen cyanide, ammonia, insoluble phosphate solubilization together with the potential to protect plants against fungal pathogens. Bacterial inoculation improved seeds germination of B. juncea plant in the presence of 0.1 mM Cr, Cd, and Ni, as compared to the control treatment. Compared with control treatment, soil inoculation with bacterial isolates significantly increased the amount of soluble heavy metals in soil by 51% (Cr), 50% (Cd), and 44% (Ni) respectively. Pot experiment of B. juncea grown in soil spiked with 100 mg kg^?1 of NiCl₂, 100 mg kg^?1 of CdCl₂, and 150 mg kg^?1 of K₂Cr₂O₇, revealed that inoculation with metal tolerant bacteria not only protected plants against the toxic effects of heavy metals, but also increased growth and metal accumulation of plants significantly. These findings suggest that such metal tolerant, plant growth promoting bacteria are valuable tools which could be used to develop bio-inoculants for enhancing the efficiency of phytoextraction.     

Optimization of environmental parameters for biodegradation of alpha and beta endosulfan in soil slurry by Pseudomonas aeruginosa

Aim: To determine optimal environmental conditions for achieving biodegradation of α‐ and β‐endosulfan in soil slurries following inoculation with an endosulfan degrading strain of Pseudomonas aeruginosa. Methods and Results: Parameters that were investigated included soil texture, soil slurry: water ratios, initial inoculum size, pH, incubation temperature, aeration, and the use of exogenous sources of organic and amino acids. The results showed that endosulfan degradation was most effectively achieved at an initial inoculum size of 600 μl (OD = 0·86), incubation temperature of 30°C, in aerated slurries at pH 8, in loam soil. Under these conditions, the bacterium removed more than 85% of spiked α‐ and β‐endosulfan (100 mg l^?1) after 16 days. Abiotic degradation in noninoculated control medium within same incubation period was about 16%. Biodegradation of endosulfan varied in different textured soils, being more rapid in course textured soil than in fine textured soil. Increasing the soil contents in the slurry above 15% resulted in less biodegradation of endosulfan. Exogenous application of organic acids (citric acid and acetic acid) and amino acids (l ‐methionine and l ‐cystein) had stimulatory and inhibitory effects, respectively, on biodegradation of endosulfan. Conclusion: The results of this study demonstrated that biodegradation of endosulfan by Ps. aeruginosa in soil sediments enhanced significantly under optimized environmental conditions. Significance and Impact of the Study: Endosulfan is a commonly used pesticide that can contaminate soil, wetlands and groundwater. Our study demonstrates that bioaugmentation of contaminated soils with an endosulfan degrading bacterium under optimized conditions provides an effective bioremediation strategy.     

Characterization of <Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis> RM-3 as a Potential Biocontrol Agent

Molecular characterization of rhizobacterial isolate RM-3, based on sequencing of a partial 1,313-bp fragment of 16S rDNA amplicon, validated the strain as Pseudomonas aeruginosa. The strain showed significant growth inhibition of different phytopathogenic fungi in dual plate and liquid culture assays. Maximum growth inhibition was found in case of Macrophomina phaseolina in plate assay (68%), whereas it was 93% in Dreschlera graminae in dual liquid assay. Microscopic studies (light and scanning electron) showed morphological abnormalities such as perforation, fragmentation, swelling, shriveling and lysis of hyphae of pathogenic fungi. The strain also exhibited production of siderophore and hydrogen cyanide (HCN) on chrome azurol S and King’s B media, respectively. Besides, this strain also produced extracellular chitinase enzyme and an important antibiotic, phenazine. Seed bacterization with RM-3 showed a significant (P < 0.05) increase in seed germination, shoot length, shoot fresh and dry weight, root length, root fresh and dry weight and leaf area. It was also able to colonize the rhizosphere of plants and reduced percent disease incidence in M. phaseolina-infested soil by 83%. Yield parameters such as pods, number of seeds and grain yield per plant also enhanced significantly (P < 0.05) in comparison to control. Thus, the secondary metabolites producing Pseudomonas aeruginosa strain RM-3 exhibited innate potential of plant growth promotion and biocontrol potential in vitro and in vivo.     

Isolation,identification and characterization of soil microbes which degrade phenolic allelochemicals

Aims: To isolate and characterize microbes in the soils containing high contents of phenolics and to dissolve the allelopathic inhibition of plants through microbial degradation. Methods and Results: Four microbes were isolated from plant soils using a screening medium containing p‐coumaric acid as sole carbon source. The isolates were identified by biochemical analysis and sequences of their 16S or 18S rDNA, and designated as Pseudomonas putida 4CD1 from rice (Oryza sativa) soil, Ps. putida 4CD3 from pine (Pinus massoniana) soil, Pseudomonas nitroreducens 4CD2 and Rhodotorula glutinis 4CD4 from bamboo (Bambusa chungii) soil. All isolates degraded 1 g l^?1 of p‐coumaric acid by 70–93% in inorganic and by 99% in Luria‐Bertani solutions within 48 h. They also effectively degraded ferulic acid, p‐hydroxybenzoic acid and p‐hydroxybenzaldehyde. The microbes can degrade p‐coumaric acid and reverse its inhibition on seed germination and seedling growth in culture solutions and soils. Low pHs inhibited the growth and phenolic degradation of the three bacteria. High temperature inhibited the R. glutinis. Co²⁺ completely inhibited the three bacteria, but not the R. glutinis. Cu²⁺, Al³⁺, Zn²⁺, Fe³⁺, Mn²⁺, Mg²⁺ and Ca²⁺ had varying degrees of inhibition for each of the bacteria. Conclusions: Phenolics in plant culture solutions and soils can be decomposed through application of soil microbes in laboratory or controlled conditions. However, modification of growth conditions is more important for acidic and ions‐contaminated media. Significance and Impact of the Study: The four microbes were first isolated and characterized from the soils of bamboo, rice or pine. This study provides some evidence and methods for microbial control of phenolic allelochemicals.     

Reduction of aryl acids by white-rot fungi for the biocatalytic production of aryl aldehydes and alcohols

Ligninolytic basidiomycetes were screened for their ability to reduce aryl acids to the corresponding aldehydes and alcohols. Seven fungal strains converted p-anisic acid in high molar yields to the reduced products. The white-rot fungus Bjerkandera sp. strain BOS55 was one of the best reducing strains and was highly tolerant towards high concentrations of different aromatic acids. It was tested for the reduction of p-anisic, veratric, 3-chloro-4-methoxybenzoic, 3,5-dichloro-4-methoxybenzoic, 3,4-dichlorobenzoic, 4-fluorobenzoic, and 3-nitrobenzoic acids. All of these compounds were reduced to their corresponding aldehydes and alcohols. Received: 22 March 1999 / Received revision: 12 July 1999 / Accepted: 1 August 1999     

Evaluation of Pseudomonas chlororaphis subsp. aurantiaca SR1 for growth promotion of soybean and for control of Macrophomina phaseolina

Pseudomonas chlororaphis subsp. aurantiaca SR1 was evaluated for control of Macrophomina phaseolina in vitro and in soybean plants, for growth promotion of soybean plants and for production of antifungal compounds. Strain SR1 caused a significant inhibition of M. phaseolina in vitro and reduced damping-off in the in vivo assays. In addition, strain SR1 significantly increased shoot and root length and shoot and root dry weight of soybean plants in M. phaseolina infested soil, as compared to control plants in infested soil. Fragments for the phenazine-1-carboxylic acid, pyrrolnitrin and hydrogen cyanide encoding genes were amplified from the DNA of strain SR1 after polymerase chain reaction (PCR) assays with specific primers. Thus, this study establishes that P. chlororaphis subsp. aurantiaca SR1 provides control of M. phaseolina in vivo and suggests that strain SR1 might be applied as an effective biocontrol agent to protect soybean plants from this phytopathogen.     

Effects of different treatments of fly ash and mining soil on growth and antioxidant protection of Indian wild rice

The aim of the present study was investigation of the effects of fly ash and mining soil on growth and antioxidant protection of two cultivars of Indian wild rice (Oryza nivara and Oryza rufipogon) for possible phytoremediation and restoration of metal-contaminated site. In this study, Indian wild rice showed significant changes in germination, growth, and biochemical parameters after exposure to different ratio of fly ash and mining soil with garden soil. There was significant reduction of germination, fresh weight, dry weight, leaf chlorophyll content, leaf area, Special Analysis Device Chlorophyll (SPAD) Index, proteins, and activities of antioxidant enzymes in both cultivars of the wild rice grown in 100% fly ash and mining soil compared to the plants grown in 100% garden soil. Results from this study showed that in both cultivars of wild rice, all growth and antioxidant parameters increased when grown in 50% fly ash and mining soil. Taken together, Indian wild rice has the capacity to tolerate 50% of fly ash and mining soil, and can be considered as a good candidate for possible phytoremediation of contaminated soils.     

Characterization of Fluoroglycofen Ethyl Degradation by Strain <Emphasis Type="Italic">Mycobacterium phocaicum</Emphasis> MBWY-1

A fluoroglycofen ethyl-degrading bacterium, MBWY-1, was isolated from the soil of an herbicide factory. This isolated strain was identified as Mycobacterium phocaicum based on analysis of its 16S rRNA gene sequence and its morphological, physiological, and biochemical properties. The strain was able to utilize fluoroglycofen ethyl as its sole source of carbon for growth and could degrade 100 mg l⁻¹ of fluoroglycofen ethyl to a non-detectable level within 72 h. The optimum temperature and pH for fluoroglycofen ethyl degradation by strain MBWY-1 were 30°C and 7.0, respectively. Five metabolites produced during the degradation of fluoroglycofen ethyl and were identified by mass spectrometry as {5-[2-chloro-4-(trifluoromethyl) phenoxy]-2-nitrophenylacyl} hydroxyacetic acid, acifluorfen, 5-[2-chloro-4-(trifluoromethyl) phenoxy]-2-nitrobenzoate, 5-[2-chloro-4-(trifluoromethyl) phenoxy]-2-hydroxyl, and 3-chloro-4-hydroxyl benzotrifluoride. Identification of the metabolites allowed to propose the degradation pathway of fluoroglycofen ethyl by strain MBWY-1. The inoculation of strain MBWY-1 into soil treated with fluoroglycofen ethyl resulted in a higher fluoroglycofen ethyl degradation rate than in uninoculated soil regardless of whether the soil was sterilized or nonsterilized.