Degradation of polychlorinated biphenyls (PCBs) by four bacterial isolates obtained from the PCB-contaminated soil and PCB-contaminated sediment

We investigated the PCB-degrading abilities of four bacterial strains isolated from long-term PCB-contaminated soil (Alcaligenes xylosoxidans and Pseudomonas stutzeri) and sediments (Ochrobactrum anthropi and Pseudomonas veronii) that were co-metabolically grown on glucose plus biphenyl which is an inducer of the PCB catabolic pathway. The aim of study was to determine the respective contribution of biomass increase and expression of degrading enzymes on the PCB degrading abilities of each isolate. Growth on 5 g l⁻¹ glucose alone resulted in the highest stimulation of the growth of bacterial strains, whereas grown on 10 mg l⁻¹, 100 mg l⁻¹, 1 g l⁻¹, or 5 g l⁻¹ biphenyl did not effected the bacterial growth. None of the strains used in this study was able to grow on PCBs as the sole carbon source. Cells grown on glucose exhibited enhanced degradation ability due to an increased biomass. Addition of biphenyl at concentrations of 1 or 5 g l⁻¹ did not increase total PCB degradation, but stimulated the degradation of highly chlorinated congeners for some of the strains. The degradation of di- and tri-chlorobiphenyls was significantly lower for cells grown on 5 g l⁻¹ biphenyl independently on glucose addition. The highest degradation of the PCBs was obtained for A. xylosoxidans grown in the presence of glucose. Thus A. xylosoxidans appears to be the most promising among the four bacterial isolates for the purpose of bioremediation.     

Extensive biodegradation of highly chlorinated biphenyl and Aroclor 1242 by Pseudomonas aeruginosa TMU56 isolated from contaminated soils

A bacterial strain, designated TMU56, was isolated from soil that had been contaminated with electrical transformer fluid (Askarel) for over 35 years. The isolate was identified as Pseudomonas aeruginosa using its 16S rDNA sequence. This strain was found to grow on monochlorobiphenyls (CBs), including 2-chlorobenzoic acid and 4-chlorobenzoic acid. It was also found to grow on 2,4-, 2,5-, 2,2′-, and 4,4′-diCB, as well as on a wide range of other xenobiotic compounds. This is the first reported representative of the genus Pseudomonas that is capable of growing on 2,4,4′-triCB, 2,2′,5,5′-tetraCB and 2,2′,4,4′,5,5′-hexaCB as sole carbon sources. Washed benzoate-grown cells were able to degrade 89% and 56% of 2,4-diCB and 2,2′,4,4′,5,5′-hexaCB, respectively. Gas chromatography analysis of individual congeners in Aroclor 1242 (200 ppm) following a 4-day incubation showed 73.3% degradation of PCBs without the need for biphenyl as an inducer. The strain exhibited no noticeable specificity for the percentage of congener transformation or degree of chlorination.     

Effect of chlorobenzoates on the degradation of polychlorinated biphenyls (PCB) by Pseudomonas stutzeri

Chlorobenzoic acids (CBA) are frequently dead-end products of partial aerobic biodegradation of polychlorinated biphenyls (PCB). When CBA produced from PCB accumulate in the growth medium, they can inhibit the bacterial growth and consequently, slow down PCB biodegradation. In this study, the effects of seven mono- and dichlorinated CBA on growth of Pseudomonas stutzeri on different substrates and on the PCB degradation by this strain in a liquid mineral medium were tested. 3-CBA was the strongest growth inhibitor for P. stutzeri growing on glucose, benzoate and biphenyl. It was found to inhibit heavily the elimination of some di- and trichlorinated biphenyls. In contrast, its influence on the elimination of more chlorinated congeners was much less significant.The authors are with the Department of Biochemical Technology, Faculty of Chemical Technology, Slovak Technical University, 812 37 Bratislava, Slovakia.     

Biodegradation of chlorinated alkanes and their commercial mixtures by Pseudomonas sp. strain 273

The biodegradation of chlorinated alkanes was studied under oxic conditions with the objective of identifying favorable and unfavorable intramolecular chlorination sequences with respect to the enzymes studied. Several dehalogenating bacterial strains were screened for their ability to degrade middle-chain polychlorinated alkanes as well as a commercial mixture. Of the organisms tested, the most promising was Pseudomonas sp. strain 273, which possesses an oxygenolytic dehalogenase. The effects of carbon chain length (C₆–C₁₆), halogen position, and overall chlorine content (14–61% w/w) were examined using both commercially available compounds and molecules synthesized in our laboratory. The effects of co-substrates, solvents, and inducing agents were also studied. The results with pure chlorinated alkanes showed that the relative positions of the chlorine atoms strongly influenced the total amount of dehalogenation achieved. The greatest dehalogenation yields were associated with terminally chlorinated alkanes. The α- and α,ω-chlorinated compounds yielded similar results. Vicinal chlorination had the most dramatic impact on degradation. When present on both ends or at the center of the molecule, no dehalogenation was detected. Although partial dehalogenation of 1,2-dichlorodecane was observed, it was likely due to a combination of β-oxidation and an abiotic mechanism. Cereclor S52 was appreciably dehalogenated in shake flasks only when 1,10-dichlorodecane was present as a co-substrate and after increasing the oil surface area through mechanical emulsification, demonstrating the importance of abiotic factors in degrading commercial polychlorinated alkane mixtures.     

Biodegradation of polychlorinated biphenyls in Aroclor 1232 and production of metabolites from 2,4,4'-trichlorobiphenyl at low temperature by psychrotolerant Hydrogenophaga sp. strain IA3-A

AIMS: To determine the extent and pattern of degradation of polychlorinated biphenyls (PCBs) in Aroclor 1232 at 5 degrees C by a psychrotolerant bacterium, and to confirm the formation of intermediates of PCB metabolism at low temperature using 2,4,4'-trichlorobiphenyl (2,4,4'-TCB). METHODS AND RESULTS: 10 ppm of Aroclor 1232 or 100 micromol l(-1) 2,4,4'-TCB was incubated with biphenyl-grown cells at 5 degrees C or 30 degrees C for 48 or 72 h. Degradation of PCBs and the products of metabolism of 2,4,4'-TCB were confirmed by gas chromatography and mass spectrometry. Extents of degradation of many of the PCBs were similar at 5 degrees C and 30 degrees C. The extent of biodegradation of PCBs in Aroclor 1232 at 5 degrees C was dependent on chlorination pattern. The 14 chlorine-containing intermediates of 2,4,4'-TCB metabolism, which were detected, include several isomers of dihydrodiols, dihydroxy compounds and meta-cleavage compounds. CONCLUSIONS: The bacterium will be useful for bioremediation of PCB-contaminated sites in cold climates; however, knowledge of the products of PCB metabolism is necessary, as they could be more toxic than the parent compounds. SIGNIFICANCE AND IMPACT OF THE STUDY: Substantial degradation of some PCBs in Aroclor 1232 was demonstrated at low temperature within 48 h. The detection of several isomeric intermediates suggests that multiple pathways are used to transform PCBs in this strain. For the first time, formation of metabolic products from 2,4,4'-TCB at low temperature is confirmed.     

Crystallization and preliminary crystallographic analysis of a 2,3-dihydroxybiphenyl dioxygenase from Pseudomonas sp. strain KKS102 having polychlorinated biphenyl (PCB)-degrading activity

Crystals have been obtained for a 2,3-dihydroxybiphenyl dioxygenase (conventionally called BphC) from a polychlorinated biphenyl (PCB)-degrader, Pseudomonas sp. strain KKS1O2. The crystals were grown using both ammonium sulfate and MPD as the precipitating agents. The crystals belonged to a tetragonal space group (I422) and diffracted to 2.5 Å. © 1995 Wiley-Liss, Inc.     

Analysis of changes in congener selectivity during PCB degradation by Burkholderia sp. strain TSN101 with increasing concentrations of PCB and characterization of the bphBCD genes and gene products

We isolated and characterized a gram-negative bacterium, Burkholderia sp. strain TSN101, that can degrade polychlorinated biphenyls (PCBs) at concentrations as high as 150 μg Kaneclor 300/ml, a PCB mixture equivalent to Aroclor 1242. Growing cells of strain TSN101 degraded most of the tri- and tetrachlorobiphenyls in medium containing 25 μg Kaneclor 300/ml. Using PCB concentrations of 50–150 μg of Kaneclor 300/ml, the congener selectivity pattern was different and the pattern of chlorine substitution strongly affected degradation of some congeners. At 25 μg Kaneclor 300/ml, strain TSN101 degraded di- and trichlorinated congeners with chlorine substitutions at both the ortho and the para positions. At higher concentrations of Kaneclor 300, di- and trichlorobiphenyls with ortho substituents in both phenyl rings were not degraded well. Trichlorobiphenyls with para and meta substitutents were degraded equally well at all concentrations studied. The ability of strain TSN101 to degrade ortho and para-substituted congeners was confirmed using a defined PCB mixture with chlorine substituents at 2′- and 4′-positions. A 5-kb DNA fragment containing the bphBCD genes was cloned and sequenced. Comparison of the deduced amino acid sequences of these genes with related proteins indicated 99 and 98% sequence similarity to the BphB and BphD of Comamonas testosteroni strain B-356, respectively. The bphC gene product showed 74% sequence similarity to the BphC of Burkholderia cepacia strain LB400 and exhibited a narrow substrate specificity with strong affinity for 2,3-dihydroxybiphenyl. A bphC-disrupted mutant of Burkholderia sp. strain TSN101, constructed by gene replacement, lost the ability to utilize biphenyl, thus supporting the role of the cloned bph gene in biphenyl metabolism. Received: 18 February 1997 / Accepted: 19 August 1997     

Degradation of polychlorinated biphenyl (PCB) by a consortium obtained from a contaminated soil composed of Brevibacterium,Pandoraea and Ochrobactrum

An indigenous polychlorinated biphenyl (PCB)-degrading bacterial consortium was obtained from soils contaminated by transformer oil with a high content of PCBs. The PCB degrader strains were isolated and identified as Brevibacterium antarcticum, Pandoraea pnomenusa, and Ochrobactrum intermedium by 16S rRNA gene sequence phylogenetic analysis. The PCB-degrading ability of the consortium and of individual strains was determined by using GC/MS. The PCB-degrading capacities of the consortium were evaluated for three concentrations of transfomer oil ranging from 55 to 152 μM supplemented with 0.001% biphenyl and 0.1% of Tween 80 surfactant. PCB biodegradation by the consortium was favored in the presence of both additives and the greatest extent of biodegradation (67.5%) was obtained at a PCB concentration of 55 μM. Each bacterial species exhibited a particular pattern of degradation relating to specific PCB congeners. Isolated strains showed a moderate degradation capability towards tetra-, hepta-, and octa-chlorobiphenyls; although no effect on penta-, hexa-, and nona-chlorobiphenyls was observed. Recently, PCB degradation capacity was recognized in a Pandorea member; however, this is the first study that describes the ability of Brevibacterium and Ochrobactrum species to degrade PCBs.     

产碱杆菌ECU0401催化拆分扁桃酸及其衍生物

从土壤中分离的1株产碱杆菌Alcaligenes sp.ECU0401具有扁桃酸脱氢酶活性,可以以扁桃酸、苯甲酰甲酸或苯甲酸为唯一C源生长,并且具有较高的脱氢酶活力。以外消旋扁桃酸为C源,采用分批补料策略培养（或反应）99h,扁桃酸累计投入量为30.4g/L,（S）-（＋）-扁桃酸被完全降解,（R）-（-）-扁桃酸回收产率为32.8%,对映体过量值（e.e.）〉99.9%。利用静息细胞作为催化剂不对称降解外消旋扁桃酸的氯代衍生物,制备获得光学活性的（R）-（-）-邻氯扁桃酸、（S）-（＋）-间氯扁桃酸和（S）-（＋）-对氯扁桃酸,光学纯度均超过99.9%e.e.。     

Biodegradation of seven polychlorinated biphenyls by a newly isolated aerobic bacterium (<Emphasis Type="Italic">Rhodococcus</Emphasis> sp. R04)

An aerobic bacterial strain, designated R04, belonging to the genus Rhodococcus has been isolated and characerized by 16S rDNA analysis. The capability of this strain to degrade seven different polychlorinated biphenyls (CBs), 500 ppm 3-CB, 3,4-CB, 4,4-CB, 2,4,6-CB, 2,4,5-CB, 2,3,4,5-CB and 3,4,3,4-CB in liquid medium, was evaluated. After 5 days of incubation, the concentration of chloride increased to 0.35 mM in cultures containing 3-CB and R04, whereas in cultures with 3,4-CB, 2,3,4,5-CB or 3,4,3,4-CB plus R04 the chloride content increased to 0.1 mM. However, non-stoichiometric amounts of chloride were produced in cultures with R04 and 4,4-CB, 2,4,6-CB and 2,4,5-CB. The spectrum of supernatants from R04 grown on seven PCBs had a UV-visible (UV-VIS) absorption at 200–500 nm, characteristic of biphenyl-derived cleavage products. Gas-chromatographic (GC) analysis showed that R04 was able to transform 100% of 3-CB and 3,4-CB after 1 day of incubation, and 95% of 4,4-CB, 2,4,6-CB, 2,4,5-CB, 2,3,4,5-CB and 3,4,3,4-CB after 5 days of incubation. The position of the chlorine substituents on the rings strongly influenced the degradation of polychlorinated biphenyls (PCBs) and their intermediate metabolites by Rhodococcus sp. R04. The degradation of PCBs was further evaluated by monitoring intermediate metabolites of PCBs.     

Stereospecific oxidation of (R)- and (S)-1-indanol by naphthalene dioxygenase from Pseudomonas sp. strain NCIB 9816-4.

A recombinant Escherichia coli strain which expresses naphthalene dioxygenase (NDO) from Pseudomonas sp. strain NCIB 9816-4 oxidized (S)-1-indanol to trans-(1S,3S)-indan-1,3-diol (95.5%) and (R)-3-hydroxy-1-indanone (4.5%). The same cells oxidized (R)-1-indanol to cis-1,3-indandiol (71%), (R)-3-hydroxy-1-indanone (18.2%), and cis-1,2,3-indantriol (10.8%). Purified NDO oxidized (S)-1-indenol to both syn- and anti-2,3-dihydroxy-1-indanol.     

Location and sequence analysis of a 2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoate hydrolase-encoding gene (bpdF) of the biphenyl/ polychlorinated biphenyl degradation pathway in Rhodococcus sp. M5

The 2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoate (HOPD) hydrolase-encoding gene (bpdF) in the biphenyl (BP)/polychlorinated biphenyl (PCB)-degrading bacterium, Rhodococcus sp. M5 (M5), was found to be located within a 4.5-kb HindIII-BamHI genomic DNA that was 5.4 kb downstream from the bpdC1C2BADE gene cluster. The deduced amino acid (aa) sequence of bpdF revealed that the hydrolase contains 297 aa (32679 Da) that was verified by expression in the Escherichia coli T7 RNA polymerase/promoter system. Unlike previously known HOPD hydrolases, the aa sequence of BpdF appears unique. Interestingly, all HOPD hydrolases and related proteins from the phenol and toluene/ xylene degradation pathways, were found to have a bias in the codon usage in the catalytic Ser within the conserved VGNS(M/F)GG motif.     

Effects of organic and inorganic salts on docosahexaenoic acid (DHA) production by a locally isolated strain of Thraustochytrium sp. T01

Abstract

The traditional source for docosahexaenoic acid (DHA) i.e. fish oil is currently being replaced by microbial sources due to the unpleasant odor and the risk of chemical contamination of fish. Thraustochytrium sp., marine microalgae-like protist is a known source of DHA. In our previous study, we reported a high yielding strain, T01, of Thraustochytrium sp. for DHA production isolated from the mangroves of South India. This strain shows promising yields of biomass and DHA. Shake flask study of T01 yielded 6.17?±?0.04 gL^?1 of DHA. In the present work, we report the effects of organic and inorganic salts on DHA production. Addition of organic salts such as sodium acetate, pyruvate, citrate and malate led to increase in the DHA content in T01 strain. The DHA content increased by 40–46% on addition of sodium salts of organic acids, while inorganic phosphates increased DHA by 33%. The total lipid content also increased (28–33%) with salts of organic acids and 28% with phosphate, but not as much as the increase in DHA. Addition of all the salts together did not show a significant increase in lipid and DHA contents as compared to the addition of individual salts.     

Degradation of 2,4-dichlorophenol by Bacillus sp. isolated from an aeration pond in the Baikalsk pulp and paper mill (Russia)

A pure culture of 2,4-dichlorophenol (2,4-DCP)-degrading bacteria was isolated from a natural enrichment that had been adapted to chlorophenols in the aeration pond of the Baikalsk pulp and paper mill (Russia). The bacteria were identified by 16S rDNA intergenic region analysis, using PCR with universal primers. Comparative analysis of the 16S rDNA sequence (1545 bp) in the GenBank database revealed that these bacteria are related to Bacillus cereus GN1. Degradation of 2,4-DCP was studied using this culture in liquid medium under aerobic conditions, at initial concentrations of 20–560 μM 2,4-DCP. The 2,4-DCP degradation rates by B. cereus GN1 could be determined at concentrations up to 400 μM. However, higher concentrations of 2,4-DCP (560 μM) were inhibitory to cell growth.     

Characterization of Borrelia sp. isolated from Ixodes tanuki, I. turdus, and I. columnae in Japan by restriction fragment length polymorphism of rrf (5S)-rrl (23S) intergenic spacer amplicons

Abstract Accumulation of citric acid by Aspergillus niger depends on a high flux through glycolysis. We have investigated the possibility of control of this flux by trehalose 6-phosphate, an inhibitor of hexokinase of Saccharomyces cerevisiae and other eukaryotes (Blasquez et al., FEBS Lett. (1993) 329, 517ndash;54). Hexokinase of A. niger was shown in vitro to be only weakly inhibited by trehalose 6-phosphate (K, 1.5–2 mM). To investigate the in vivo relevance of this inhibition, we used isogenic strains of A. niger , carrying either a disruption or an amplification of the trehalose-6-phosphate synthase A (T6PSA)-encoding gene ( ggsA ) and exhibiting corresponding differences in T6PSA activity. These strains produced citric acid at comparable rates and with similar yields on 1 or 2.5% (w/v) sucrose. At 5–14% (w/v) sucrose, the ggsA disrupted strain initiated citric acid accumulation earlier, whereas the multicopy strain showed the reverse effect. When sucrose was replaced by lactose, which enabled only low rates of catabolism irrespective of its concentration (1–8%), no differences in the initiation or rate of citric acid accumulation were observed between the three strains. The possible mechanisms by which ggsA controls glycolytic flux in A. niger in the presence of high sugar concentrations are discussed.