Forgot your password?
New user?
New Window Opens on the Secret Life of Microbes: Scientists Develop First Microbial Profiles of Ecosystems
CAS announces the release of SciFinder Scholar for Mac OS X
Press Releases
Press Releases
| Check out our New Publishers' Select for Free Articles |
Applied Microbiology and Biotechnology (v.50, #1)
New aspects of genes and enzymes for β-lactam antibiotic biosynthesis by J. F. Martín (pp. 1-15).
Penicillins, cephalosporins and cephamycins are peptide antibiotics synthesized by condensation of l-α-aminoadipic acid, l-cysteine and l-valine to form the tripeptide δ(l-α-aminoadipyl)-l-cysteinyl-d-valine (Aad-Cys-Val) by a non-ribosomal peptide synthetase. The genes pcbAB and pcbC, common to all penicillin and cephalosporin producers, that encode the Aad-Cys-Val synthetase1 and isopenicillin N (IPN) synthase1 respectively, have been cloned and the encoded enzymes studied in detail. The IPN synthase has been crystallized and its active center identified, providing evidence for the molecular mechanism of cyclization of the tripeptide Aad-Cys-Val to isopenicillin N. The late genes of the penicillin and cephalosporin pathways have also been characterized although some of the molecular mechanisms catalyzed by the encoded enzymes (e.g. IPN acyltransferase) are still obscure. In cephamycin-producing organisms, biosynthesis of the α-aminoadipic acid precursor proceeds in two steps catalyzed by lysine 6-aminotransferase and piperideine-6-carboxylic acid dehydrogenase. The gene lat for the first of these enzymes is located in the cephamycin gene cluster, providing an interesting example of association of genes encoding enzymes for the formation of a precursor with genes involved in assembly of the antibiotics. Novel enzymes involved in methoxylation at C-7 and carbamoylation at C-3′ of the cephem nucleus were isolated from Nocardia lactamdurans and Streptomyces clavuligerus. The methoxylation system is encoded by two linked genes cmcI-cmcJ and their products (proteins P7 and P8) form a complex that is required for hydroxylation at C-7 and for the subsequent methylation of the 7-hydroxycephem derivative to form the methoxyl group. Carbamoylation at the C-3′-hydroxyl group of the cephem nucleus is catalyzed by a specific carbamoyltransferase encoded by the gene cmcH. Finally, genes for a β-lactamase (bla), a penicillin-binding protein (pbp) and a transmembrane protein (cmcT) that appears to be involved in cephamycin exportation, are clustered together with the biosynthetic genes in the cephamycin clusters of S. clavuligerus and N. lactamdurans. Availability of the cloned genes allows metabolic engineering of the β-lactam biosynthetic pathways such as a channelling precursors and directed removal of bottlenecks in the β-lactam biosynthetic pathways. Several new β-lactam antibiotics have been discovered in gram-positive and gram-negative bacteria that will provide new genes for combinatorial synthesis of new molecules.
Bioaugmentation in activated sludge: current features and future perspectives by H. Van Limbergen; E. M. Top; W. Verstraete (pp. 16-23).
Bioaugmentation of activated sludge systems with specialised bacterial strains could be a powerful tool to improve several aspects in wastewater treatment processes, such as improved flocculation and degradation of recalcitrant compounds. This review focuses on the addition of strains to activated sludge to enhance the biodegradation of recalcitrant compounds, either through the activity of the inoculated strain or after transfer of degradative plasmids to activated sludge bacteria. Different factors that improve the aggregation of the sludge flocs and their influence on biodegradation are described. This review further deals with the role of bacterial plasmids in natural genetic exchange between inoculated and indigenous sludge bacteria, and in the construction of new genetically modified organisms. The few successful cases of bioaugmentation described in this review, together with future research, must lead to a better understanding of sludge bioaugmentation.
Fermentation of glycerol to 1,3-propanediol and 2,3-butanediol by Klebsiella pneumoniae by H. Biebl; A.-P. Zeng; K. Menzel; W.-D. Deckwer (pp. 24-29).
Klebsiella pneumoniae was shown to convert glycerol to 1,3-propanediol, 2,3-butanediol and ethanol under conditions of uncontrolled pH. Formation of 2,3-butanediol starts with some hours' delay and is accompanied by a reuse of the acetate that was formed in the first period. The fermentation was demonstrated in the type strain of K. pneumoniae, but growth was better with the more acid-tolerant strain GT1, which was isolated from nature. In continuous cultures in which the pH was lowered stepwise from 7.3 to 5.4, 2,3-butanediol formation started at pH 6.6 and reached a maximum yield at pH 5.5, whereas formation of acetate and ethanol declined in this pH range. 2,3-Butanediol and acetoin were also found among the products in chemostat cultures grown at pH 7 under conditions of glycerol excess but only with low yields. At any of the pH values tested, excess glycerol in the culture enhanced the butanediol yield. Both effects are seen as a consequence of product inhibition, the undissociated acid being a stronger trigger than the less toxic diols and acid anions. The possibilities for using the fermentation type described to produce 1,3-propanediol and 2,3-butanediol almost without by-products are discussed.
Poly-(3-hydroxybutyrate) production from whey by high-density cultivation of recombinant Escherichia coli by H. H. Wong; S. Y. Lee (pp. 30-33).
Recombinant Escherichia coli strain GCSC 6576, harboring a high-copy-number plasmid containing the Ralstonia eutropha genes for polyhydroxyalkanoate (PHA) synthesis and the E. coli ftsZ gene, was employed to produce poly-(3-hydroxybutyrate) (PHB) from whey. pH-stat fed-batch fermentation, using whey powder as the nutrient feed, produced cellular dry weight and PHB concentrations of 109 g l−1 and 50 g l−1 respectively in 47 h. When concentrated whey solution containing 210 g l−1 lactose was used as the nutrient feed, cellular dry weight and PHB concentrations of 87 g l−1 and 69 g l−1 respectively could be obtained in 49 h by pH-stat fed-batch culture. The PHB content was as high as 80% of the cellular dry weight. These results suggest that cost-effective production of PHB is possible by fed-batch culture of recombinant E. coli using concentrated whey solution as a substrate.
Process development for high-level secretory production of carboxypeptidase Y by Saccharomyces cerevisiae by Y. Shiba; F. Fukui; K. Ichikawa; N. Serizawa; H. Yoshikawa (pp. 34-41).
In order to develop a production process for carboxypeptidase Y (CPY, yeast vacuolar protease) secreted by Saccharomyces cerevisiae KS58-2D, medium composition, culture conditions, and expression systems were investigated. We found that the addition of histidine to thiamine-free medium, in which CPY production was almost negligible, raised the intracellular thiamine level, resulting in the increase of CPY production. On the basis of the choice of an expression system that uses an inducible GAL10 promoter, reassessment of histidine concentration in the medium, and optimization of the pH level during cultivation (pH 6.5), active CPY was secreted in a quantity of over 400 mg/l, which was more than tenfold that higher than that previously reported. The process developed could be easily scaled-up to industrial-scale fermentation.
Analysis of the leuB gene from Corynebacterium glutamicum by M. Pátek; J. Hochmannová; M. Jelínková; J. Nešvera; L. Eggeling (pp. 42-47).
The leuB gene of Corynebacterium glutamicum was found to be present on a 2.2-kb BamHI-SacI chromosomal fragment which complemented the leuB mutation of Escherichia coli. The activity of 3-isopropylmalate dehydrogenase (EC 1.1.1.85), encoded by the leuB gene, was significantly increased in C. glutamicum cells harbouring a plasmid containing the 2.2-kb fragment. The nucleotide sequence of the C. glutamicumleuB coding region (an open reading frame, ORF, of 1020 bp encoding a polypeptide of 340 amino acids with M r of 36 144) was determined. The deduced amino acid sequence of the product of this ORF is highly homologous to those of 3-isopropylmalate dehydrogenases from three species of mycobacteria. The transcriptional start site of the leuB gene was localized 35 bp upstream of its translational start; a functional terminator was detected in the 3′ flanking region. Northern hybridization analysis showed that the C. glutamicumleuB gene is transcribed as a single monocistronic RNA (approximately 1.2 kb in size). Activity of the leuB promoter was significantly reduced when leucine was present in the growth medium. This suggests the negative regulation of the leuB expression on the transcriptional level in C. glutamicum cells.
Cloning of a new endoglucanase gene from Bacillus sp. BP-23 and characterisation of the enzyme. Performance in paper manufacture from cereal straw by A. Blanco; P. Díaz; J. Martínez; T. Vidal; A. L. Torres; F. I. J. Pastor (pp. 48-54).
The gene celA, encoding an endoglucanase from the strain Bacillus sp. BP-23, was cloned and expressed in Escherichia coli. The nucleotide sequence of a 1867-bp DNA fragment containing the celA gene was determined, revealing an open reading frame of 1200 nucleotides that encodes a protein of 44 803 Da. The deduced amino acid sequence of the encoded enzyme shows high homology to those of enzymes belonging to subtype 4 of the family-A cellulases. The celA gene product synthesized in E. coli showed activity on carboxymethylcellulose and lichenan but no activity was found on Avicel. Activity was enhanced in the presence of 10 mM Mg2+ and Ca2+ and showed its maximum at 40 °C and pH 4.0. Study of the performance of CelA on paper manufacture from agricultural fibres showed that treatment with the enzyme improved the properties of the pulp and the quality of paper. CelA treatment enhanced the physical properties (stretch and tensile index) of paper from wheat straw, while dewatering properties were slightly diminished. Electron-microscope analysis showed that the surface of straw fibres was modified by CelA.
Analysis of the gene for β-fructosidase (invertase, inulinase) of the hyperthermophilic bacterium Thermotoga maritima, and characterisation of the enzyme expressed in Escherichia coli by W. Liebl; D. Brem; A. Gotschlich (pp. 55-64).
This is the first report describing the gene structure and the enzymatic properties of a β-fructosidase of a hyperthermophilic organism. The bfrA gene of the ancestral bacterium Thermotoga maritima MSB8 codes for a 432-residue, polypeptide of about 50 kDa, with significant sequence similarity to other β-fructosidases. On the basis of its primary structure, BfrA can be assigned to glycosyl hydrolase family 32. The bfrA gene was expressed in Escherichia coli and the recombinant enzyme was purified and characterised. BfrA was specific for the fructose moiety and the β-anomeric configuration of the glycosidic linkages of its substrates. The enzyme released fructose from sucrose and raffinose, and the fructose polymer inulin was hydrolysed quantitatively in an exo-type fashion. BfrA displayed similar catalytic efficiencies for the hydrolysis of sucrose and inulin with k cat/K m values (at 75 °C, pH 5.5) of about 4.1 × 104 M−1s−1 and 3.1 × 104 M−1s−1 respectively. BfrA had an optimum temperature of 90–95 °C (10-min assay) and was extremely insensitive to thermo-inactivation. During 5 h at temperatures up to 80 °C at pH 7, the enzyme retained at least 85% of its initial activity. Thus, BfrA is the most thermostable β-fructosidase and also the most thermostable inulinase described to date. In conclusion, the T. maritima enzyme can be classified as an exo-β-d-fructofuranosidase (EC 3.2.1.26) with invertase and inulinase activity. Its catalytic properties along with the extreme thermostability recommend it for use in biotechnology.
Production of glucose isomerase in a recombinant strain of Streptomyces lividans
by F. Wang; R. D. Whitaker; C. A. Batt (pp. 65-70).
High-level expression of the angiotensin-converting-enzyme-inhibiting peptide, YG-1, as tandem multimers in Escherichia coli by C. J. Park; J. H. Lee; S.-S. Hong; H.-S. Lee; S. C. Kim (pp. 71-76).
To produce a large quantity of the angiotensin-converting-enzyme(ACE)-inhibiting peptide YG-1, which consists of ten amino acids derived from yeast glyceraldehyde-3-phosphate dehydrogenase, a high-level expression was explored with tandem multimers of the YG-1 gene in Escherichia coli. The genes encoding YG-1 were tandemly multimerized to 9-mers, 18-mers and 27-mers, in which each of the repeating units in the tandem multimers was connected to the neighboring genes by a DNA linker encoding Pro-Gly-Arg for the cleavage of multimers by clostripain. The multimers were cloned into the expression vector pET-21b, and expressed in E. coli BL21(DE3) with isopropyl β-d-thiogalactopyranoside induction. The expressed multimeric peptides encoded by the 9-mer, 18-mer and 27-mer accumulated intracellularly as inclusion bodies and comprised about 67%, 25% and 15% of the total proteins in E. coli respectively. The multimeric peptides expressed as inclusion bodies were cleaved with clostripain, and active monomers were purified to homogeneity by reversed-phase high-performance liquid chromatography. In total, 105 mg pure recombinant YG-1 was obtained from 1 l E. coli culture harboring pETYG9, which contained the 9-mer of the YG-1 gene. The recombinant YG-1 was identical to the natural YG-1 in molecular mass, amino acid sequence and ACE-inhibiting activity.
Cloning and characterization of the gene encoding a repressible acid phosphatase (PHO1) from the methylotrophic yeast Hansenula polymorpha by A. Phongdara; A. Merckelbach; P. Keup; G. Gellissen; C. P. Hollenberg (pp. 77-84).
A cloned cDNA, generated from mRNA isolates of phosphate-derepressed H. polymorpha cells, was identified to harbour an incomplete sequence of the coding region for a repressible acid phosphatase. The cDNA fragment served as a probe to screen a plasmid library of H. polymorpha genomic DNA. A particular clone, p606, of a 1.9-kb insert contained a complete copy of the PHO1 gene. Sequencing revealed the presence of a 1329-nucleotide open reading frame encoding a protein of 442 amino acids with a calculated M r of 49400. The␣encoded protein has an N-terminal 17-amino-acid secretory leader sequence and seven potential N-glycosylation sites. The leader cleavage site was confirmed by N-terminal sequencing of the purified enzyme. The nucleotide sequence is 48.9% homologous, the derived amino acid sequence 36% homologous to its Saccharomyces cerevisiae counterpart. The derived amino acid sequence harbours a consensus sequence RHGXRXP, previously identified as a sequence involved in active-site formation of acid phosphatases. The PHO1 promoter and the secretion leader sequence present promising new tools for heterologous gene expression.
Utilization of the TEF1-a gene (TEF1) promoter for expression of polygalacturonase genes, pgaA and pgaB, in Aspergillus oryzae by N. Kitamoto; J. Matsui; Y. Kawai; A. Kato; S. Yoshino; K. Ohmiya; N. Tsukagoshi (pp. 85-92).
For the development of an efficient gene expression system in a shoyu koji mold Aspergillus oryzae KBN616, the TEF1 gene, encoding translation-elongation factor 1α, was cloned from the same strain and used for expression of polygalacturonase genes. The TEF1 gene comprised 1647 bp with three introns. The TEF1-α protein consisted of 460 amino acids possessing high identity to other fungal TEF proteins. Two nucleotide sequences homologous to the upstream activation sequence, characterized for the ribosomal protein genes in Saccharomyces cerevisiae, as well as the pyrimidine-rich sequences were present in the TEF1 gene promoter region, suggesting that the A. oryzae TEF1 gene has a strong promoter activity. Two expression vectors, pTFGA300 and pTFGB200 for production of polygalacturonases A and B respectively, were constructed by using the TEF1 gene promoter. A polygalacturonase (PGB) gene cloned from the same strain comprised 1226 bp with two introns and encoded a protein of 367 amino acids with high similarity to other fungal polygalacturonases. PGA and PGB were secreted at approximately 100 mg/l in glucose medium and purified to homogeneity. PGA had a molecular mass of 41 kDa, a pH optimum of 5.0 and temperature optimum of 45 °C. PGB had a molecular mass of 39 kDa, a pH optimum of 5.0 and temperature optimum of 55 °C.
Cloning and expression of a gene encoding cyanidase from Pseudomonas stutzeri AK61 by A. Watanabe; K. Yano; K. Ikebukuro; I. Karube (pp. 93-97).
The gene coding for cyanidase, which catalyzes the hydrolysis of cyanide to formate and ammonia, was cloned from chromosomal DNA of Pseudomonas stutzeri AK61 into Escherichia coli. The cyanidase gene consisted of an open reading frame of 1004 bp, and it was predicted that cyanidase was composed of 334 amino acids with a calculated molecular mass of 37 518 Da. The amino acid sequence of cyanidase showed a 35.1% and 26.4% homology to aliphatic nitrilase from Rhodococcus rhodochrous K22 and cyanide hydratase from Fusarium lateritium, respectively. A unique cysteine residue of aliphatic nitrilase, which was suggested to play an essential role in the catalytic activity, was conserved in cyanidase. The active form of cyanidase was successfully expressed by a DNA clone containing the cyanidase gene in E.coli. Its productivity was approximately 230 times larger than that of P. stutzeri AK61. The characteristics of the expressed cyanidase, including optimum pH, optimum temperature, Michaelis constant (K m) for cyanide and specific activity, were similar to those of the native enzyme from P. stutzeri AK61.
Aspergillus oryzae with and without a homolog of aflatoxin biosynthetic gene ver-1 by K.-I. Kusumoto; K. Yabe; Y. Nogata; H. Ohta (pp. 98-104).
Part of the nucleotide sequence of the ver-1 homolog in each of two strains of Aspergillus oryzae, Aspergillus sojae, and Aspergillus flavus were compared with two homologs in Aspergillus parasiticus. The homologs in A. oryzae and A. sojae (non-aflatoxin-producers) exhibited an extremely high degree (93.8–99.8% for A. oryzae, and 96.0–99.5% for A. sojae) of sequence identity with that of A. flavus and A. parasiticus. No two strains within the same species, except A. sojae, were identical. No sequence fingerprint was found to distinguish between A. oryzae and A. flavus, or between A. sojae and A. parasiticus. The predicted partial amino acid sequences (181 amino acids) of the ver-1 homologs had at most two amino acid changes relative to A. parasiticus SYS-4 ver-1. Transcripts of ver-1 homologs in the strains of A. oryzae and A. sojae examined were not detected by the polymerase chain reaction coupled with reverse transcription. By Southern analysis, a total of 46 strains of A. oryzae were examined for the presence of the ver-1 homolog. The homolog was detected in 38 strains, but not in 8 strains. Morphologically, strains with and without the ver-1 homolog were indistinguishable. Thus, A. oryzae contains strains with and without a homolog of the aflatoxin biosynthetic gene ver-1.
Conversion of chlorinated propanes by Methylosinus trichosporium OB3b expressing soluble methane monooxygenase by T. Bosma; D. B. Janssen (pp. 105-112).
Chlorinated propanes are important pollutants that may show persistent behaviour in the environment. The biotransformation of 1-chloropropane, 1,2-dichloropropane, 1,3-dichloropropane and 1,2,3-trichloropropane was studied using resting cell suspensions of Methylosinus trichosporium OB3b expressing soluble methane monooxygenase. The transformation followed first-order kinetics. The rate constants were in the order 1-chloropropane > 1,3-dichloropropane > 1,2-dichloropropane > 1,2,3-trichloropropane, and varied from 0.07 to 1.03 ml min−1 mg of cells−1 for 1,2,3-trichloropropane and 1-chloropropane respectively. Turnover-dependent inactivation occurred for all of the chloropropanes tested. The inactivation constants were lower for 1-chloropropane and 1,2-dichloropropane than for 1,2,3-trichloropropane and 1,3-dichloropropane. Not all the chloride was released during cometabolic transformation of the chlorinated propanes and production of monochlorinated- and dichlorinated propanols was found by gas chromatography. The reaction pathway of 1,2,3-trichloropropane conversion was studied by mass spectrometric analysis of products formed in 2H2O, which indicated that 1,2,3-trichloropropane was initially oxidized to 2,3-dichloropropionaldehyde and 1,3-dichloroacetone, depending on whether oxygen insertion occurred on the C-3 or C-2 carbon of 1,2,3,-trichloropropane, followed by reduction to the corresponding propanols. The results show that chloropropanes are susceptible to cometabolic oxidation by methanotrophs, but that the transformation kinetics is worse than with cometabolic conversion of trichloroethylene.
High-level expression of an endoxylanase gene from Bacillus sp. in Bacillus subtilis DB104 for the production of xylobiose from xylan by K. J. Jeong; I. Y. Park; M. S. Kim; S. C. Kim (pp. 113-118).
To produce xylobiose from xylan, high-level expression of an endoxylanase gene from Bacillus sp. was carried out in Bacillus subtilis DB104. A 1.62-kb SmaI DNA fragment, coding for an endoxylanase of Bacillus sp., was ligated into the Escherichia coli/B. subtilis shuttle vector pJH27Δ88, producing pJHKJ4, which was subsequently transformed into B. subtilis DB104. A maximum endoxylanase activity of 105 U/ml was obtained from the supernatant of B. subtilis DB104 harboring pJHKJ4. The endoxylanase was purified to homogeneity by ion-exchange chromatography and the production profile of xylooligosaccharides from xylan by the endoxylanase was examined by HPLC with a carbohydrate analysis column. Xylobiose was the major product from xylan at 40 °C and its proportion in the xylan hydrolyzates increased with the reaction time; at 12 h, over 60% of the reaction products was xylobiose. These results suggest that xylobiose, which has a stimulatory effect on the selective growth of the intestinal bacterium Bifidobacterium, can be mass-produced effectively by the endoxylanase of Bacillus sp. cloned in B. subtilis.
Prevention of hyperhydricity in oregano shoot cultures is sustained through multiple subcultures by selected polysaccharide-producing soil bacteria without re-inoculation by K. Ueno; K. Shetty (pp. 119-124).
Previous studies from our laboratory showed that several non-specific, polysaccharide-producing soil bacteria could be effectively used to prevent hyperhydricity. In this study, prevention of hyperhydricity of shoot cultures of oregano clonal line O-1 was investigated over multiple subculture cycles without re-inoculation of shoots. Results clearly indicate that hyperhydricity was prevented in oregano shoot cultures over eight subculture cycles without any re-inoculation after the initial inoculation with several polysaccharide-producing bacteria in the first cycle. Hyperhydricity-related parameters of subculture cycles 7 and 8, reported in this manuscript, showed that the water content was significantly reduced in response to all bacteria tested. The total phenolics content, on a fresh-weight and dry-weight basis, was stimulated significantly by all bacterial treatments except Pseudomonas stutzeri in the seventh cycle. The chlorophyll content was significantly stimulated in all treatments on a fresh-weight basis in the two subculture cycles. On a dry-weight basis, except for P. stutzeri, the bacterial species tested induced significant increases in chlorophyll content. Plant growth in response to all bacteria was reduced. In spite of growth reduction, the numbers of shoot nodes available for propagation were not reduced and all the shoot tissues were unhyperhydrated. These results also suggested that prevention of bacteria-mediated hyperhydricity may be linked to survival of bacteria in the stem, which may be carried through to the next subculture. Acclimation studies showed that bacteria-containing shoots performed better and further strengthened the case for use of non-pathogenic, polysaccharide-producing bacteria for hyperhydricity control in commercial plant tissue cultures.
Physiology and kinetics of Bifidobacterium bifidum during growth on different sugars by N. T. Mlobeli; N. A. Gutierrez; I. S. Maddox (pp. 125-128).
A strain of Bifidobacterium bifidum was grown on different sugars under pH-controlled conditions to estimate some kinetic parameters for growth and product formation. Glucose was the preferred sugar in terms of growth rate and yield, sugar utilisation rate and acetate formation rate, while lactose gave considerably lower values for these parameters. When present in a mixture with glucose, the rate of lactose utilisation was lower than when present on its own.
Biological degradation of diesel fuel in water and soil monitored with solid-phase micro-extraction and GC-MS by M. Eriksson; A. Swartling; G. Dalhammar; J. Fäldt; A.-K. Borg-Karlson (pp. 129-134).
Solid-phase micro-extraction (SPME) was used for monitoring degradation of hydrocarbons in diesel-fuel-contaminated (1% v/v) water and soil. Natural soil bacteria with and without external addition of inoculum were used. Directly after a 10-s exposure of the sample, the polydimethylsiloxane fibre was injected into the GC-MS. This method strongly reduced the time of analysis compared to a conventional liquid/liquid extraction. A comparison of SPME and pentane extraction of diesel oil was made and found to be consistent. The degradation of diesel fuel in water was monitored for 10 weeks using SPME. After 5 weeks all hydrocarbons were degraded except for the decahydronaphthalenes. These compounds were approximately 3% of the total hydrocarbons in the diesel oil used and remained undegraded throughout the study although none of the chemical or physical parameters was limiting. In the soil study the degradation of diesel fuel in normal soil was completed after 3 weeks, when the only remaining substances were decahydronaphthalenes. All samples were compared to sterile references to make up for evaporation losses. SPME proved to be a fast and reliable method to monitor changes in concentrations of semi-volatile organic compounds.
Anaerobic biodegradation of pentachlorophenol in a contaminated soil inoculated with a methanogenic consortium or with Desulfitobacterium frappieri strain PCP-1 by R. Beaudet; M.-J. Lévesque; R. Villemur; M. Lanthier; M. Chénier; F. Lépine; J.-G. Bisaillon (pp. 135-141).
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.