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Maphosa F, van Passel MWJ, de Vos WM, Smidt H. Metagenome analysis reveals yet unexplored reductive dechlorinating potential of Dehalobacter sp. E1 growing in co-culture with Sedimentibacter sp. ENVIRONMENTAL MICROBIOLOGY REPORTS 2012; 4:604-616. [PMID: 23760931 DOI: 10.1111/j.1758-2229.2012.00376.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2012] [Accepted: 07/28/2012] [Indexed: 06/02/2023]
Abstract
The importance of Dehalobacter species in bioremediation as dedicated degraders of chlorinated organics has been well recognized. However, still little is known about Dehalobacter's full genomic repertoires, including the genes involved in dehalogenation. Here we report the first insights into the genome sequence of Dehalobacter sp. E1 that grows in strict co-culture with Sedimentibacter sp. B4. Based on the co-culture metagenome and the genome of strain B4 (4.2 Mbp) we estimate the genome sequence of strain E1 to be 2.6 Mbp. Ten putative reductive dehalogenase homologue (Rdh)-encoding gene clusters were identified. One cluster has a putative tetrachloroethene Rdh-encoding gene cluster, similar to the pceABCT operon previously identified in Dehalobacter restrictus. Metagenome analysis indicated that the inability of strain E1 to synthesize cobalamin, an essential cofactor of reductive dehalogenases, is complemented by Sedimentibacter. The metagenomic exploration described here maps the extensive dechlorinating potential of Dehalobacter, and paves way for elucidation of the interactions with its co-cultured Sedimentibacter.
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Affiliation(s)
- Farai Maphosa
- Laboratory of Microbiology, Wageningen University, Wageningen, The Netherlands; NGI Ecogenomics Consortium, Amsterdam, The Netherlands
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102
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Abstract
Despite the fact that the genetic code is known to vary between organisms in rare cases, it is believed that in the lifetime of a single cell the code is stable. We found Acetohalobium arabaticum cells grown on pyruvate genetically encode 20 amino acids, but in the presence of trimethylamine (TMA), A. arabaticum dynamically expands its genetic code to 21 amino acids including pyrrolysine (Pyl). A. arabaticum is the only known organism that modulates the size of its genetic code in response to its environment and energy source. The gene cassette pylTSBCD, required to biosynthesize and genetically encode UAG codons as Pyl, is present in the genomes of 24 anaerobic archaea and bacteria. Unlike archaeal Pyl-decoding organisms that constitutively encode Pyl, we observed that A. arabaticum controls Pyl encoding by down-regulating transcription of the entire Pyl operon under growth conditions lacking TMA, to the point where no detectable Pyl-tRNA(Pyl) is made in vivo. Pyl-decoding archaea adapted to an expanded genetic code by minimizing TAG codon frequency to typically ~5% of ORFs, whereas Pyl-decoding bacteria (~20% of ORFs contain in-frame TAGs) regulate Pyl-tRNA(Pyl) formation and translation of UAG by transcriptional deactivation of genes in the Pyl operon. We further demonstrate that Pyl encoding occurs in a bacterium that naturally encodes the Pyl operon, and identified Pyl residues by mass spectrometry in A. arabaticum proteins including two methylamine methyltransferases.
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103
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CARD-FISH analysis of a TCE-dechlorinating biocathode operated at different set potentials. N Biotechnol 2012; 30:33-8. [DOI: 10.1016/j.nbt.2012.06.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2012] [Revised: 06/06/2012] [Accepted: 06/11/2012] [Indexed: 11/18/2022]
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104
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Maphosa F, Lieten SH, Dinkla I, Stams AJ, Smidt H, Fennell DE. Ecogenomics of microbial communities in bioremediation of chlorinated contaminated sites. Front Microbiol 2012; 3:351. [PMID: 23060869 PMCID: PMC3462421 DOI: 10.3389/fmicb.2012.00351] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2012] [Accepted: 09/12/2012] [Indexed: 11/29/2022] Open
Abstract
Organohalide compounds such as chloroethenes, chloroethanes, and polychlorinated benzenes are among the most significant pollutants in the world. These compounds are often found in contamination plumes with other pollutants such as solvents, pesticides, and petroleum derivatives. Microbial bioremediation of contaminated sites, has become commonplace whereby key processes involved in bioremediation include anaerobic degradation and transformation of these organohalides by organohalide respiring bacteria and also via hydrolytic, oxygenic, and reductive mechanisms by aerobic bacteria. Microbial ecogenomics has enabled us to not only study the microbiology involved in these complex processes but also develop tools to better monitor and assess these sites during bioremediation. Microbial ecogenomics have capitalized on recent advances in high-throughput and -output genomics technologies in combination with microbial physiology studies to address these complex bioremediation problems at a system level. Advances in environmental metagenomics, transcriptomics, and proteomics have provided insights into key genes and their regulation in the environment. They have also given us clues into microbial community structures, dynamics, and functions at contaminated sites. These techniques have not only aided us in understanding the lifestyles of common organohalide respirers, for example Dehalococcoides, Dehalobacter, and Desulfitobacterium, but also provided insights into novel and yet uncultured microorganisms found in organohalide respiring consortia. In this paper, we look at how ecogenomic studies have aided us to understand the microbial structures and functions in response to environmental stimuli such as the presence of chlorinated pollutants.
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Affiliation(s)
- Farai Maphosa
- Laboratory of Microbiology, Wageningen UniversityWageningen, Netherlands
| | | | | | - Alfons J. Stams
- Laboratory of Microbiology, Wageningen UniversityWageningen, Netherlands
| | - Hauke Smidt
- Laboratory of Microbiology, Wageningen UniversityWageningen, Netherlands
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105
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Sánchez-Andrea I, Rojas-Ojeda P, Amils R, Sanz JL. Screening of anaerobic activities in sediments of an acidic environment: Tinto River. Extremophiles 2012; 16:829-39. [PMID: 22956355 DOI: 10.1007/s00792-012-0478-4] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2012] [Accepted: 08/16/2012] [Indexed: 11/29/2022]
Abstract
The Tinto River (Huelva, Spain) is a natural acidic rock drainage environment produced by the bio-oxidation of metallic sulfides from the Iberian Pyritic Belt. A geomicrobiological model of the different microbial cycles operating in the sediments was recently developed through molecular biological methods, suggesting the presence of iron reducers, methanogens, nitrate reducers and hydrogen producers. In this study, we used a combination of molecular biological methods and targeted enrichment incubations to validate this model and prove the existence of those potential anaerobic activities in the acidic sediments of Tinto River. Methanogenic, sulfate-reducing, denitrifying and hydrogen-producing enrichments were all positive at pH between 5 and 7. Methanogenic enrichments revealed the presence of methanogenic archaea belonging to the genera Methanosarcina and Methanobrevibacter. Enrichments for sulfate-reducing microorganisms were dominated by Desulfotomaculum spp. Denitrifying enrichments showed a broad diversity of bacteria belonging to the genera Paenibacillus, Bacillus, Sedimentibacter, Lysinibacillus, Delftia, Alcaligenes, Clostridium and Desulfitobacterium. Hydrogen-producing enrichments were dominated by Clostridium spp. These enrichments confirm the presence of anaerobic activities in the acidic sediments of the Tinto River that are normally assumed to take place exclusively at neutral pH.
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Affiliation(s)
- Irene Sánchez-Andrea
- Departamento de Biología Molecular, Universidad Autónoma de Madrid, c/Darwin 2, C-014/021, Campus de Cantoblanco, Crtra. de Colmenar, Km. 15, 28049, Madrid, Spain.
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106
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Impact of vitamin B12 on formation of the tetrachloroethene reductive dehalogenase in Desulfitobacterium hafniense strain Y51. Appl Environ Microbiol 2012; 78:8025-32. [PMID: 22961902 DOI: 10.1128/aem.02173-12] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Corrinoids are essential cofactors of reductive dehalogenases in anaerobic bacteria. Microorganisms mediating reductive dechlorination as part of their energy metabolism are either capable of de novo corrinoid biosynthesis (e.g., Desulfitobacterium spp.) or dependent on exogenous vitamin B(12) (e.g., Dehalococcoides spp.). In this study, the impact of exogenous vitamin B(12) (cyanocobalamin) and of tetrachloroethene (PCE) on the synthesis and the subcellular localization of the reductive PCE dehalogenase was investigated in the gram-positive Desulfitobacterium hafniense strain Y51, a bacterium able to synthesize corrinoids de novo. PCE-depleted cells grown for several subcultivation steps on fumarate as an alternative electron acceptor lost the tetrachloroethene-reductive dehalogenase (PceA) activity by the transposition of the pce gene cluster. In the absence of vitamin B(12), a gradual decrease of the PceA activity and protein amount was observed; after 5 subcultivation steps with 10% inoculum, more than 90% of the enzyme activity and of the PceA protein was lost. In the presence of vitamin B(12), a significant delay in the decrease of the PceA activity with an ∼90% loss after 20 subcultivation steps was observed. This corresponded to the decrease in the pceA gene level, indicating that exogenous vitamin B(12) hampered the transposition of the pce gene cluster. In the absence or presence of exogenous vitamin B(12), the intracellular corrinoid level decreased in fumarate-grown cells and the PceA precursor formed catalytically inactive, corrinoid-free multiprotein aggregates. The data indicate that exogenous vitamin B(12) is not incorporated into the PceA precursor, even though it affects the transposition of the pce gene cluster.
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107
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Prat L, Maillard J, Rohrbach-Brandt E, Holliger C. An unusual tandem-domain rhodanese harbouring two active sites identified in Desulfitobacterium hafniense. FEBS J 2012; 279:2754-67. [PMID: 22686689 DOI: 10.1111/j.1742-4658.2012.08660.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The rhodanese protein domain is common throughout all kingdoms of life and is characterized by an active site cysteine residue that is able to bind sulfane sulfur and catalyse sulfur transfer. No unique function has been attributed to rhodanese-domain-containing proteins, most probably because of their diversity at both the level of sequence and protein domain architecture. In this study, we investigated the biochemical properties of an unusual rhodanese protein, PhsE, from Desulfitobacterium hafniense strain TCE1 which we have previously shown to be massively expressed under anaerobic respiration with tetrachloroethene. The peculiarity of the PhsE protein is its domain architecture which is constituted of two rhodanese domains each with an active site cysteine. The N-terminal rhodanese domain is preceded by a lipoprotein signal peptide anchoring PhsE on the outside of the cytoplasmic membrane. In vitro sulfur-transferase activity of recombinant PhsE variants was measured for both domains contrasting with other tandem-domain rhodaneses in which usually only the C-terminal domain has been found to be active. The genetic context of phsE shows that it is part of a six-gene operon displaying homology with gene clusters encoding respiratory molybdoenzymes of the PhsA/PsrA family, possibly involved in the reduction of sulfur compounds. Our data suggest, however, that the presence of sulfide in the medium is responsible for the high expression of PhsE in Desulfitobacterium, where it could play a role in the sulfur homeostasis of the cell.
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Affiliation(s)
- Laure Prat
- Laboratory for Environmental Biotechnology, Institute of Environmental Engineering, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
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108
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Ding C, He J. Molecular techniques in the biotechnological fight against halogenated compounds in anoxic environments. Microb Biotechnol 2012; 5:347-67. [PMID: 22070763 PMCID: PMC3821678 DOI: 10.1111/j.1751-7915.2011.00313.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2011] [Revised: 09/24/2011] [Accepted: 09/28/2011] [Indexed: 11/28/2022] Open
Abstract
Microbial treatment of environmental contamination by anthropogenic halogenated organic compounds has become popular in recent decades, especially in the subsurface environments. Molecular techniques such as polymerase chain reaction-based fingerprinting methods have been extensively used to closely monitor the presence and activities of dehalogenating microbes, which also lead to the discovery of new dehalogenating bacteria and novel functional genes. Nowadays, traditional molecular techniques are being further developed and optimized for higher sensitivity, specificity, and accuracy to better fit the contexts of dehalogenation. On the other hand, newly developed high throughput techniques, such as microarray and next-generation sequencing, provide unsurpassed detection ability, which has enabled large-scale comparative genomic and whole-genome transcriptomic analysis. The aim of this review is to summarize applications of various molecular tools in the field of microbially mediated dehalogenation of various halogenated organic compounds. It is expected that traditional molecular techniques and nucleic-acid-based biomarkers will still be favoured in the foreseeable future because of relative low costs and high flexibility. Collective analyses of metagenomic sequencing data are still in need of information from individual dehalogenating strains and functional reductive dehalogenase genes in order to draw reliable conclusions.
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Affiliation(s)
| | - Jianzhong He
- Department of Civil and Environmental Engineering, National University of Singapore, Singapore 117576
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109
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Abstract
Besides acetogenic bacteria, only Desulfitobacterium has been described to utilize and cleave phenyl methyl ethers under anoxic conditions; however, no ether-cleaving O-demethylases from the latter organisms have been identified and investigated so far. In this study, genes of an operon encoding O-demethylase components of Desulfitobacterium hafniense strain DCB-2 were cloned and heterologously expressed in Escherichia coli. Methyltransferases I and II were characterized. Methyltransferase I mediated the ether cleavage and the transfer of the methyl group to the superreduced corrinoid of a corrinoid protein. Desulfitobacterium methyltransferase I had 66% identity (80% similarity) to that of the vanillate-demethylating methyltransferase I (OdmB) of Acetobacterium dehalogenans. The substrate spectrum was also similar to that of the latter enzyme; however, Desulfitobacterium methyltransferase I showed a higher level of activity for guaiacol and used methyl chloride as a substrate. Methyltransferase II catalyzed the transfer of the methyl group from the methylated corrinoid protein to tetrahydrofolate. It also showed a high identity (∼70%) to methyltransferases II of A. dehalogenans. The corrinoid protein was produced in E. coli as cofactor-free apoprotein that could be reconstituted with hydroxocobalamin or methylcobalamin to function in the methyltransferase I and II assays. Six COG3894 proteins, which were assumed to function as activating enzymes mediating the reduction of the corrinoid protein after an inadvertent oxidation of the corrinoid cofactor, were studied with respect to their abilities to reduce the recombinant reconstituted corrinoid protein. Of these six proteins, only one was found to catalyze the reduction of the corrinoid protein.
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110
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Genome sequence of Desulfitobacterium hafniense DCB-2, a Gram-positive anaerobe capable of dehalogenation and metal reduction. BMC Microbiol 2012; 12:21. [PMID: 22316246 PMCID: PMC3306737 DOI: 10.1186/1471-2180-12-21] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2011] [Accepted: 02/08/2012] [Indexed: 12/13/2022] Open
Abstract
Background The genome of the Gram-positive, metal-reducing, dehalorespiring Desulfitobacterium hafniense DCB-2 was sequenced in order to gain insights into its metabolic capacities, adaptive physiology, and regulatory machineries, and to compare with that of Desulfitobacterium hafniense Y51, the phylogenetically closest strain among the species with a sequenced genome. Results The genome of Desulfitobacterium hafniense DCB-2 is composed of a 5,279,134-bp circular chromosome with 5,042 predicted genes. Genome content and parallel physiological studies support the cell's ability to fix N2 and CO2, form spores and biofilms, reduce metals, and use a variety of electron acceptors in respiration, including halogenated organic compounds. The genome contained seven reductive dehalogenase genes and four nitrogenase gene homologs but lacked the Nar respiratory nitrate reductase system. The D. hafniense DCB-2 genome contained genes for 43 RNA polymerase sigma factors including 27 sigma-24 subunits, 59 two-component signal transduction systems, and about 730 transporter proteins. In addition, it contained genes for 53 molybdopterin-binding oxidoreductases, 19 flavoprotein paralogs of the fumarate reductase, and many other FAD/FMN-binding oxidoreductases, proving the cell's versatility in both adaptive and reductive capacities. Together with the ability to form spores, the presence of the CO2-fixing Wood-Ljungdahl pathway and the genes associated with oxygen tolerance add flexibility to the cell's options for survival under stress. Conclusions D. hafniense DCB-2's genome contains genes consistent with its abilities for dehalogenation, metal reduction, N2 and CO2 fixation, anaerobic respiration, oxygen tolerance, spore formation, and biofilm formation which make this organism a potential candidate for bioremediation at contaminated sites.
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111
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Surface multiheme c-type cytochromes from Thermincola potens and implications for respiratory metal reduction by Gram-positive bacteria. Proc Natl Acad Sci U S A 2012; 109:1702-7. [PMID: 22307634 DOI: 10.1073/pnas.1112905109] [Citation(s) in RCA: 136] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Almost nothing is known about the mechanisms of dissimilatory metal reduction by Gram-positive bacteria, although they may be the dominant species in some environments. Thermincola potens strain JR was isolated from the anode of a microbial fuel cell inoculated with anaerobic digester sludge and operated at 55 °C. Preliminary characterization revealed that T. potens coupled acetate oxidation to the reduction of hydrous ferric oxides (HFO) or anthraquinone-2,6-disulfonate (AQDS), an analog of the redox active components of humic substances. The genome of T. potens was recently sequenced, and the abundance of multiheme c-type cytochromes (MHCs) is unusual for a Gram-positive bacterium. We present evidence from trypsin-shaving LC-MS/MS experiments and surface-enhanced Raman spectroscopy (SERS) that indicates the expression of a number of MHCs during T. potens growth on either HFO or AQDS, and that several MHCs are localized to the cell wall or cell surface. Furthermore, one of the MHCs can be extracted from cells with low pH or denaturants, suggesting a loose association with the cell wall or cell surface. Electron microscopy does not reveal an S-layer, and the precipitation of silver metal on the cell surface is inhibited by cyanide, supporting the involvement of surface-localized redox-active heme proteins in dissimilatory metal reduction. These results provide unique direct evidence for cell wall-associated cytochromes and support MHC involvement in conducting electrons across the cell envelope of a Gram-positive bacterium.
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112
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Effect of 2,4,6-trichlorophenol on the microbial activity of adapted anaerobic granular sludge bioaugmented with Desulfitobacterium strains. N Biotechnol 2011; 29:79-89. [DOI: 10.1016/j.nbt.2011.06.011] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2011] [Revised: 06/10/2011] [Accepted: 06/13/2011] [Indexed: 11/17/2022]
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113
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Liang B, Jiang J, Zhang J, Zhao Y, Li S. Horizontal transfer of dehalogenase genes involved in the catalysis of chlorinated compounds: evidence and ecological role. Crit Rev Microbiol 2011; 38:95-110. [DOI: 10.3109/1040841x.2011.618114] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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114
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Sánchez-Andrea I, Rodríguez N, Amils R, Sanz JL. Microbial diversity in anaerobic sediments at Rio Tinto, a naturally acidic environment with a high heavy metal content. Appl Environ Microbiol 2011; 77:6085-93. [PMID: 21724883 PMCID: PMC3165421 DOI: 10.1128/aem.00654-11] [Citation(s) in RCA: 115] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2011] [Accepted: 06/24/2011] [Indexed: 11/20/2022] Open
Abstract
The Tinto River is an extreme environment located at the core of the Iberian Pyritic Belt (IPB). It is an unusual ecosystem due to its size (100 km long), constant acidic pH (mean pH, 2.3), and high concentration of heavy metals, iron, and sulfate in its waters, characteristics that make the Tinto River Basin comparable to acidic mine drainage (AMD) systems. In this paper we present an extensive survey of the Tinto River sediment microbiota using two culture-independent approaches: denaturing gradient gel electrophoresis and cloning of 16S rRNA genes. The taxonomic affiliation of the Bacteria showed a high degree of biodiversity, falling into 5 different phyla: Proteobacteria, Firmicutes, Bacteroidetes, Acidobacteria, and Actinobacteria; meanwhile, all the Archaea were affiliated with the order Thermoplasmatales. Microorganisms involved in the iron (Acidithiobacillus ferrooxidans, Sulfobacillus spp., Ferroplasma spp., etc.), sulfur (Desulfurella spp., Desulfosporosinus spp., Thermodesulfobium spp., etc.), and carbon (Acidiphilium spp., Bacillus spp., Clostridium spp., Acidobacterium spp., etc.) cycles were identified, and their distribution was correlated with physicochemical parameters of the sediments. Ferric iron was the main electron acceptor for the oxidation of organic matter in the most acid and oxidizing layers, so acidophilic facultative Fe(III)-reducing bacteria appeared widely in the clone libraries. With increasing pH, the solubility of iron decreases and sulfate-reducing bacteria become dominant, with the ecological role of methanogens being insignificant. Considering the identified microorganisms-which, according to the rarefaction curves and Good's coverage values, cover almost all of the diversity-and their corresponding metabolism, we suggest a model of the iron, sulfur, and organic matter cycles in AMD-related sediments.
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MESH Headings
- Archaea/classification
- Archaea/genetics
- Bacteria/classification
- Bacteria/genetics
- Biodiversity
- Cloning, Molecular
- Cluster Analysis
- DNA, Archaeal/chemistry
- DNA, Archaeal/genetics
- DNA, Bacterial/chemistry
- DNA, Bacterial/genetics
- DNA, Ribosomal/chemistry
- DNA, Ribosomal/genetics
- Denaturing Gradient Gel Electrophoresis
- Genes, rRNA
- Geologic Sediments/microbiology
- Molecular Sequence Data
- Phylogeny
- RNA, Archaeal/genetics
- RNA, Bacterial/genetics
- RNA, Ribosomal, 16S/genetics
- Rivers
- Sequence Analysis, DNA
- Sequence Homology, Nucleic Acid
- Spain
- Water Microbiology
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Affiliation(s)
- Irene Sánchez-Andrea
- Universidad Autónoma de Madrid, Departamento de Biología Molecular, 28049 Madrid, Spain
- Centro de Biología Molecular Severo Ochoa, UAM-CSIC, 28049 Madrid, Spain
| | - Nuria Rodríguez
- Centro de Astrobiología, INTA-CSIC, Ctra. Ajalvir-Torrejón de Ardoz, 28850 Madrid, Spain
| | - Ricardo Amils
- Universidad Autónoma de Madrid, Departamento de Biología Molecular, 28049 Madrid, Spain
- Centro de Biología Molecular Severo Ochoa, UAM-CSIC, 28049 Madrid, Spain
- Centro de Astrobiología, INTA-CSIC, Ctra. Ajalvir-Torrejón de Ardoz, 28850 Madrid, Spain
| | - José Luis Sanz
- Universidad Autónoma de Madrid, Departamento de Biología Molecular, 28049 Madrid, Spain
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115
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Maillard J, Genevaux P, Holliger C. Redundancy and specificity of multiple trigger factor chaperones in Desulfitobacteria. Microbiology (Reading) 2011; 157:2410-2421. [DOI: 10.1099/mic.0.050880-0] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The ribosome-bound trigger factor (TF) chaperone assists folding of newly synthesized polypeptides and participates in the assembly of macromolecular complexes. In the present study we showed that multiple distinct TF paralogues are present in genomes of Desulfitobacteria, a bacterial genus known for its ability to grow using organohalide respiration. Two full-length TF chaperones and at least one truncated TF (lacking the N-terminal ribosome-binding domain) were identified, the latter being systematically linked to clusters of reductive dehalogenase genes encoding the key enzymes in organohalide respiration. Using a well-characterized heterologous chaperone-deficient Escherichia coli strain lacking both TF and DnaK chaperones, we demonstrated that all three TF chaperones were functional in vivo, as judged by their ability to partially suppress bacterial growth defects and protein aggregation in the absence of both major E. coli chaperones. Next, we found that the N-terminal truncated TF-like protein PceT functions as a dedicated chaperone for the cognate reductive dehalogenase PceA by solubilizing and stabilizing it in the heterologous system. Finally, we showed that PceT specifically interacts with the twin-arginine signal peptide of PceA. Taken together, our data define PceT (and more generally the new RdhT family) as a class of TF-like chaperones involved in the maturation of proteins secreted by the twin-arginine translocation pathway.
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Affiliation(s)
- Julien Maillard
- Laboratoire de Biotechnologie Environnementale (LBE), Institut d’Ingénierie de l’Environnement (IIE), Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Pierre Genevaux
- Laboratoire de Microbiologie et Génétique Moléculaires (LMGM), Centre National de la Recherche Scientifique (CNRS), Université Paul-Sabatier (UPS), Toulouse, France
| | - Christof Holliger
- Laboratoire de Biotechnologie Environnementale (LBE), Institut d’Ingénierie de l’Environnement (IIE), Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
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116
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Quantitative analysis of the relative transcript levels of four chlorophenol reductive dehalogenase genes in Desulfitobacterium hafniense PCP-1 exposed to chlorophenols. Appl Environ Microbiol 2011; 77:6261-4. [PMID: 21742910 DOI: 10.1128/aem.00390-11] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Relative to those of unexposed cultures, the transcript levels of the four CprA-type reductive dehalogenase genes (cprA2, cprA3, cprA4, and cprA5) in Desulfitobacterium hafniense PCP-1 were measured in cultures exposed to chlorophenols. In 2,4,6-trichlorophenol-amended cultures, cprA2 and cprA3 were upregulated, as was cprA5, but concomitantly with the appearance of 2,4-dichlorophenol (DCP). In 3,5-DCP-amended cultures, only cprA5 was upregulated. In pentachlorophenol-amended cultures grown for 12 h, cprA2 and cprA3 were upregulated but not cprA5. cprA4 was not upregulated significantly in cultures containing any tested chlorophenols.
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117
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Physiological adaptation of Desulfitobacterium hafniense strain TCE1 to tetrachloroethene respiration. Appl Environ Microbiol 2011; 77:3853-9. [PMID: 21478312 DOI: 10.1128/aem.02471-10] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Desulfitobacterium spp. are ubiquitous organisms with a broad metabolic versatility, and some isolates have the ability to use tetrachloroethene (PCE) as terminal electron acceptor. In order to identify proteins involved in this organohalide respiration process, a comparative proteomic analysis was performed. Soluble and membrane-associated proteins obtained from cells of Desulfitobacterium hafniense strain TCE1 that were growing on different combinations of the electron donors lactate and hydrogen and the electron acceptors PCE and fumarate were analyzed. Among proteins increasingly expressed in the presence of PCE compared to fumarate as electron acceptor, a total of 57 proteins were identified by mass spectrometry analysis, revealing proteins involved in stress response and associated regulation pathways, such as PspA, GroEL, and CodY, and also proteins potentially participating in carbon and energy metabolism, such as proteins of the Wood-Ljungdahl pathway and electron transfer flavoproteins. These proteomic results suggest that D. hafniense strain TCE1 adapts its physiology to face the relative unfavorable growth conditions during an apparent opportunistic organohalide respiration.
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118
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Frequent concomitant presence of Desulfitobacterium spp. and "Dehalococcoides" spp. in chloroethene-dechlorinating microbial communities. Appl Microbiol Biotechnol 2010; 90:361-8. [PMID: 21152914 DOI: 10.1007/s00253-010-3042-0] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2010] [Revised: 11/23/2010] [Accepted: 11/24/2010] [Indexed: 10/18/2022]
Abstract
The presence of chloroethene dechlorination activity as well as several bacterial genera containing mainly organohalide-respiring members was investigated in 34 environmental samples from 18 different sites. Cultures inoculated with these environmental samples on tetrachloroethene and amended weekly with a seven organic electron donor mixture resulted in 11 enrichments with cis-DCE, ten with VC, and 11 with ethene as dechlorination end product, and only two where no dechlorination was observed. "Dehalococcoides" spp. and Desulfitobacterium spp. were detected in the majority of the environmental samples independently of the dechlorination end product formed. The concomitant presence of Dehalococcoides spp. and Desulfitobacterium spp. in the majority of the enrichments suggested that chloroethene dechlorination was probably the result of catalysis by at least two organohalide-respiring genera either in parallel or by stepwise catalysis. A more detailed study of one enrichment on cis-DCE suggested that in this culture Desulfitobacterium spp. as well as Dehalococcoides spp. dechlorinated cis-DCE whereas dechlorination of VC was only catalyzed by the latter.
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Miller MD, Aravind L, Bakolitsa C, Rife CL, Carlton D, Abdubek P, Astakhova T, Axelrod HL, Chiu HJ, Clayton T, Deller MC, Duan L, Feuerhelm J, Grant JC, Han GW, Jaroszewski L, Jin KK, Klock HE, Knuth MW, Kozbial P, Krishna SS, Kumar A, Marciano D, McMullan D, Morse AT, Nigoghossian E, Okach L, Reyes R, van den Bedem H, Weekes D, Xu Q, Hodgson KO, Wooley J, Elsliger MA, Deacon AM, Godzik A, Lesley SA, Wilson IA. Structure of the first representative of Pfam family PF04016 (DUF364) reveals enolase and Rossmann-like folds that combine to form a unique active site with a possible role in heavy-metal chelation. Acta Crystallogr Sect F Struct Biol Cryst Commun 2010; 66:1167-73. [PMID: 20944207 PMCID: PMC2954201 DOI: 10.1107/s1744309110007517] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2009] [Accepted: 02/26/2010] [Indexed: 11/16/2022]
Abstract
The crystal structure of Dhaf4260 from Desulfitobacterium hafniense DCB-2 was determined by single-wavelength anomalous diffraction (SAD) to a resolution of 2.01 Å using the semi-automated high-throughput pipeline of the Joint Center for Structural Genomics (JCSG) as part of the NIGMS Protein Structure Initiative (PSI). This protein structure is the first representative of the PF04016 (DUF364) Pfam family and reveals a novel combination of two well known domains (an enolase N-terminal-like fold followed by a Rossmann-like domain). Structural and bioinformatic analyses reveal partial similarities to Rossmann-like methyltransferases, with residues from the enolase-like fold combining to form a unique active site that is likely to be involved in the condensation or hydrolysis of molecules implicated in the synthesis of flavins, pterins or other siderophores. The genome context of Dhaf4260 and homologs additionally supports a role in heavy-metal chelation.
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Affiliation(s)
- Mitchell D. Miller
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | - L. Aravind
- National Institutes of Health, Bethesda, MD, USA
| | - Constantina Bakolitsa
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Program on Bioinformatics and Systems Biology, Burnham Institute for Medical Research, La Jolla, CA, USA
| | - Christopher L. Rife
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | - Dennis Carlton
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Department of Molecular Biology, The Scripps Research Institute, La Jolla, CA, USA
| | - Polat Abdubek
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Protein Sciences Department, Genomics Institute of the Novartis Research Foundation, San Diego, CA, USA
| | - Tamara Astakhova
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Center for Research in Biological Systems, University of California, San Diego, La Jolla, CA, USA
| | - Herbert L. Axelrod
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | - Hsiu-Ju Chiu
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | - Thomas Clayton
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Department of Molecular Biology, The Scripps Research Institute, La Jolla, CA, USA
| | - Marc C. Deller
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Department of Molecular Biology, The Scripps Research Institute, La Jolla, CA, USA
| | - Lian Duan
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Center for Research in Biological Systems, University of California, San Diego, La Jolla, CA, USA
| | - Julie Feuerhelm
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Protein Sciences Department, Genomics Institute of the Novartis Research Foundation, San Diego, CA, USA
| | - Joanna C. Grant
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Protein Sciences Department, Genomics Institute of the Novartis Research Foundation, San Diego, CA, USA
| | - Gye Won Han
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Department of Molecular Biology, The Scripps Research Institute, La Jolla, CA, USA
| | - Lukasz Jaroszewski
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Program on Bioinformatics and Systems Biology, Burnham Institute for Medical Research, La Jolla, CA, USA
- Center for Research in Biological Systems, University of California, San Diego, La Jolla, CA, USA
| | - Kevin K. Jin
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | - Heath E. Klock
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Protein Sciences Department, Genomics Institute of the Novartis Research Foundation, San Diego, CA, USA
| | - Mark W. Knuth
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Protein Sciences Department, Genomics Institute of the Novartis Research Foundation, San Diego, CA, USA
| | - Piotr Kozbial
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Program on Bioinformatics and Systems Biology, Burnham Institute for Medical Research, La Jolla, CA, USA
| | - S. Sri Krishna
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Program on Bioinformatics and Systems Biology, Burnham Institute for Medical Research, La Jolla, CA, USA
- Center for Research in Biological Systems, University of California, San Diego, La Jolla, CA, USA
| | - Abhinav Kumar
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | - David Marciano
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Department of Molecular Biology, The Scripps Research Institute, La Jolla, CA, USA
| | - Daniel McMullan
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Protein Sciences Department, Genomics Institute of the Novartis Research Foundation, San Diego, CA, USA
| | - Andrew T. Morse
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Center for Research in Biological Systems, University of California, San Diego, La Jolla, CA, USA
| | - Edward Nigoghossian
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Protein Sciences Department, Genomics Institute of the Novartis Research Foundation, San Diego, CA, USA
| | - Linda Okach
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Protein Sciences Department, Genomics Institute of the Novartis Research Foundation, San Diego, CA, USA
| | - Ron Reyes
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | - Henry van den Bedem
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | - Dana Weekes
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Program on Bioinformatics and Systems Biology, Burnham Institute for Medical Research, La Jolla, CA, USA
| | - Qingping Xu
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | - Keith O. Hodgson
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Photon Science, SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | - John Wooley
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Center for Research in Biological Systems, University of California, San Diego, La Jolla, CA, USA
| | - Marc-André Elsliger
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Department of Molecular Biology, The Scripps Research Institute, La Jolla, CA, USA
| | - Ashley M. Deacon
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | - Adam Godzik
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Program on Bioinformatics and Systems Biology, Burnham Institute for Medical Research, La Jolla, CA, USA
- Center for Research in Biological Systems, University of California, San Diego, La Jolla, CA, USA
| | - Scott A. Lesley
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Department of Molecular Biology, The Scripps Research Institute, La Jolla, CA, USA
- Protein Sciences Department, Genomics Institute of the Novartis Research Foundation, San Diego, CA, USA
| | - Ian A. Wilson
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Department of Molecular Biology, The Scripps Research Institute, La Jolla, CA, USA
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120
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Dong Y, Butler EC, Philp RP, Krumholz LR. Impacts of microbial community composition on isotope fractionation during reductive dechlorination of tetrachloroethylene. Biodegradation 2010; 22:431-44. [PMID: 20862525 DOI: 10.1007/s10532-010-9416-2] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2010] [Accepted: 09/07/2010] [Indexed: 11/24/2022]
Abstract
Isotope fractionation has been used with increasing frequency as a tool to quantify degradation of chlorinated aliphatic pollutants in the environment. The objective of this research was to determine if the electron donor present in enrichment cultures prepared from uncontaminated sediments influenced the extent of isotope fractionation of tetrachloroethylene (PCE), either directly, or through its influence on microbial community composition. Two PCE-degrading enrichment cultures were prepared from Duck Pond (DP) sediment and were incubated with formate (DPF) or H(2) (DPH) as electron donor. DPF and DPH were significantly different in both product distribution and extent of isotope fractionation. Chemical and isotope analyses indicated that electron donors did not directly affect the product distribution or the extent of isotope fractionation for PCE reductive dechlorination. Instead, restriction fragment length polymorphism (RFLP) and sequence analysis of the 16S rRNA clone libraries of DPF and DPH identified distinct microbial communities in each enrichment culture, suggesting that differences in microbial communities were responsible for distinct product distributions and isotope fractionation between the two cultures. A dominant species identified only in DPH was closely related to known dehalogenating species (Sulfurospirillum multivorans and Sulfurospirillum halorespirans) and may be responsible for PCE degradation in DPH. Our study suggests that different dechlorinators exist at the same site and can be preferentially stimulated by different electron donors, especially over the long-term (i.e., years), typical of in-situ ground water remediation.
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Affiliation(s)
- Yiran Dong
- Energy and Bioscience Institute, University of Illinois-Urbana Champaign, Urbana, IL 61801, USA
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121
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Identification and characterization of a novel CprA reductive dehalogenase specific to highly chlorinated phenols from Desulfitobacterium hafniense strain PCP-1. Appl Environ Microbiol 2010; 76:7536-40. [PMID: 20870790 DOI: 10.1128/aem.01362-10] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Desulfitobacterium hafniense strain PCP-1 reductively dechlorinates pentachlorophenol (PCP) to 3-chlorophenol and a variety of halogenated aromatic compounds at the ortho, meta, and para positions. Several reductive dehalogenases (RDases) are thought to be involved in this cascade of dehalogenation. We partially purified a novel RDase involved in the dechlorination of highly chlorinated phenols from strain PCP-1 cultivated in the presence of 2,4,6-trichlorophenol. The RDase was membrane associated, and the activity was sensitive to oxygen, with a half-life of 128 min upon exposure to air. The pH and temperature optima were 7.0 and 55°C, respectively. Several highly chlorinated phenols were dechlorinated at the ortho positions. The highest dechlorinating activity levels were observed with PCP, 2,3,4,5-tetrachlorophenol, and 2,3,4-trichlorophenol. 3-Chloro-4-hydroxyphenylacetate, 3-chloro-4-hydroxybenzoate, dichlorophenols, and monochlorophenols were not dechlorinated. The apparent K(m) value for PCP was 46.7 μM at a methyl viologen concentration of 2 mM. A mixture of iodopropane and titanium citrate caused a light-reversible inhibition of the dechlorinating activity, suggesting the involvement of a corrinoid cofactor. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the partially purified preparation revealed 2 bands with apparent molecular masses of 42 and 47 kDa. Mass spectrometry analysis using Mascot to search the genome sequence of D. hafniense strain DCB-2 identified the 42-kDa band as NADH-quinone oxidoreductase, subunit D, and the 47-kDa band as the putative chlorophenol RDase CprA3. This is the first report of an RDase with high affinity and high dechlorinating activity toward PCP.
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122
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Chen CY, Wang CK, Shih YH. Microbial degradation of 4-monobrominated diphenyl ether in an aerobic sludge and the DGGE analysis of diversity. JOURNAL OF ENVIRONMENTAL SCIENCE AND HEALTH. PART. B, PESTICIDES, FOOD CONTAMINANTS, AND AGRICULTURAL WASTES 2010; 45:379-385. [PMID: 20512728 DOI: 10.1080/03601231003799945] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Polybrominated diphenyl ethers (PBDEs) were applied as flame retardant additives in polymers for many plastic and electronic products. Due to their ubiquitous distribution in the environment, potential toxicity to human and tendency for bioaccumulation, PBDEs have raised public safety concern. In this study we examined the degradation of 4-monobrominated diphenyl ether (4-BDE) in aerobic sludge, as a model for PBDE biodegradation. Degradation of 4-BDE was observed in aerobic sludge. Co-metabolism with toluene or diphenyl ether facilitated 4-BDE biodegradation in terms of kinetics and efficiency. Diphenyl ether seems to perform slightly better as an auxiliary carbon source than toluene in facilitating 4-BDE degradation. During the experiment we identified diphenyl ether by gas chromatography/mass spectrometry(GC/MS), which indicates that an anaerobic debromination has occurred. Bacterial community composition was monitored with denaturing gradient gel electrophoresis. The fragments enriched in 4-BDE-degrading aerobic sludge samples belong to presumably a novel anaerobic Clostridiales species distantly related to all known debrominating microbes. This suggests that 4-BDE biodegradation can occur in anaerobic micro-niche in an apparently aerobic environment, by a previously unknown bacterial species. These findings can provide better understandings of biodegradation of brominated diphenyl ethers and can facilitate the prediction of the fate of PBDEs in the environment.
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Affiliation(s)
- Chun-Yao Chen
- Department of Life Science, Tzu-Chi University, Hualien, Taiwan
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123
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Fletcher KE, Boyanov MI, Thomas SH, Wu Q, Kemner KM, Löffler FE. U(VI) reduction to mononuclear U(IV) by Desulfitobacterium species. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2010; 44:4705-4709. [PMID: 20469854 DOI: 10.1021/es903636c] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
The bioreduction of U(VI) to U(IV) affects uranium mobility and fate in contaminated subsurface environments and is best understood in Gram-negative model organisms such as Geobacter and Shewanella spp. This study demonstrates that U(VI) reduction is a common trait of Gram-positive Desulfitobacterium spp. Five different Desulfitobacterium isolates reduced 100 microM U(VI) to U(IV) in <10 days, whereas U(VI) remained soluble in abiotic and heat-killed controls. U(VI) reduction in live cultures was confirmed using X-ray absorption near-edge structure (XANES) analysis. Interestingly, although bioreduction of U(VI) is almost always reported to yield the uraninite mineral (UO(2)), extended X-ray absorption fine structure (EXAFS) analysis demonstrated that the U(IV) produced in the Desulfitobacterium cultures was not UO(2). The EXAFS data indicated that the U(IV) product was a phase or mineral composed of mononuclear U(IV) atoms closely surrounded by light element shells. This atomic arrangement likely results from inner-sphere bonds between U(IV) and C/N/O- or P/S-containing ligands, such as carbonate or phosphate. The formation of a distinct U(IV) phase warrants further study because the characteristics of the reduced material affect uranium stability and fate in the contaminated subsurface.
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Affiliation(s)
- Kelly E Fletcher
- School of Civil and Environmental Engineering, Georgia Institute of Technology, 311 Ferst Drive, Atlanta, Georgia 30332, USA
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124
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Exploiting the ecogenomics toolbox for environmental diagnostics of organohalide-respiring bacteria. Trends Biotechnol 2010; 28:308-16. [DOI: 10.1016/j.tibtech.2010.03.005] [Citation(s) in RCA: 123] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2009] [Revised: 03/23/2010] [Accepted: 03/26/2010] [Indexed: 11/20/2022]
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125
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Iasur-Kruh L, Ronen Z, Arbeli Z, Nejidat A. Characterization of an enrichment culture debrominating tetrabromobisphenol A and optimization of its activity under anaerobic conditions. J Appl Microbiol 2010; 109:707-715. [PMID: 20202021 DOI: 10.1111/j.1365-2672.2010.04699.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
AIM To study the effects of incubation conditions on the microbial community structure and activity of a TBBPA-debrominating enrichment culture composed of bacterial and archaeal species. METHODS AND RESULTS The effects of the methanogen inhibitor 2-bromoethanesulfonate (BES), of the antibiotic ampicillin, of substrate (tetrabromobisphenol A, TBBPA) omission and availability of different electron donors on microbial community structure and activity were examined under anaerobic conditions. Debromination of TBBPA was blocked in the presence of ampicillin, while long-term incubation with BES resulted in delayed debromination activity. The results suggest that the bacterial species responsible for the debromination of TBBPA, while archaeal species involved in electron donor metabolism. The enrichment culture lost its debromination activity after cultivation for 9 months without TBBPA, concomitantly with the disappearance of two DNA bands in a denaturing gradient gel electrophoresis (DGGE) analysis of 16S rRNA gene fragments corresponding to Pelobacter carbinolicus and Sphaerochaeta sp. TQ1 that were present in the original culture. When butyrate was used as an electron donor, TBBPA debromination activity was attenuated. When acetate was used as the electron donor, no debromination was observed and in addition, there was a decrease in the abundance of the mcrA gene. CONCLUSIONS The results indicate that to maintain a high rate of TBBPA debromination activity, it is essential to preserve the microbial community structure (bacterial and archaeal members) of this culture and supply an electron donor that produces high amounts of hydrogen when fermented. SIGNIFICANCE AND IMPACT OF THE STUDY The study provides important information for the management of cultures to be used in bioremediation of TBBPA contaminated sites.
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Affiliation(s)
- L Iasur-Kruh
- Department of Environmental Hydrology and Microbiology, The Zuckerberg Institute for Water Research, The Jacob Blaustein Institutes for Desert Research, Ben Gurion University of the Negev, Negev, Israel
| | - Z Ronen
- Department of Environmental Hydrology and Microbiology, The Zuckerberg Institute for Water Research, The Jacob Blaustein Institutes for Desert Research, Ben Gurion University of the Negev, Negev, Israel
| | - Z Arbeli
- Laboratorio Ambiental, Instituto de Biotecnología - Edificio Manuel Ancizar, Universidad Nacional de Colombia, Bogotá, Colombia
| | - A Nejidat
- Department of Environmental Hydrology and Microbiology, The Zuckerberg Institute for Water Research, The Jacob Blaustein Institutes for Desert Research, Ben Gurion University of the Negev, Negev, Israel
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126
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Yang LY, Chen J, Cheng XL, Xi DM, Yang SL, Deng WD, Mao HM. Phylogenetic analysis of 16S rRNA gene sequences reveals rumen bacterial diversity in Yaks (Bos grunniens). Mol Biol Rep 2009; 37:553-62. [DOI: 10.1007/s11033-009-9794-x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2009] [Accepted: 09/02/2009] [Indexed: 10/20/2022]
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127
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Kunapuli U, Jahn MK, Lueders T, Geyer R, Heipieper HJ, Meckenstock RU. Desulfitobacterium aromaticivorans sp. nov. and Geobacter toluenoxydans sp. nov., iron-reducing bacteria capable of anaerobic degradation of monoaromatic hydrocarbons. Int J Syst Evol Microbiol 2009; 60:686-695. [PMID: 19656942 DOI: 10.1099/ijs.0.003525-0] [Citation(s) in RCA: 99] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Dissimilatory iron reduction plays a significant role in subsurface environments. Currently, it is assumed that members of the genus Geobacter constitute the majority of the iron-reducing micro-organisms that oxidize aromatic compounds in contaminated subsurface environments. Here, we report the isolation of two phylogenetically distinct pure cultures of iron-reducing degraders of monoaromatic hydrocarbons, strain TMJ1(T), which belongs to the genus Geobacter within the Deltaproteobacteria, and strain UKTL(T), belonging to the genus Desulfitobacterium within the Clostridia. Both strains utilize a wide range of substrates as carbon and energy sources, including the aromatic compounds toluene, phenol and p-cresol. Additionally, strain UKTL(T) utilizes o-xylene and TMJ1(T) utilizes m-cresol. Anaerobic degradation of toluene in both strains and o-xylene in strain UKTL(T) is initiated by activation with fumarate addition to the methyl group. The genomic DNA G+C contents of strains TMJ1(T) and UKTL(T) are 54.4 and 47.7 mol%, respectively. Based on a detailed physiological characterization and phylogenetic analysis of the 16S rRNA genes of both strains, we propose the names Desulfitobacterium aromaticivorans sp. nov. (type strain UKTL(T) =DSM 19510(T) =JCM 15765(T)) and Geobacter toluenoxydans sp. nov. (type strain TMJ1(T) =DSM 19350(T) =JCM 15764(T)) to accommodate these strains. To the best of our knowledge, strain UKTL(T) is the first described spore-forming, iron-reducing bacterium that can degrade aromatic hydrocarbons.
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Affiliation(s)
- Umakanth Kunapuli
- Institute of Groundwater Ecology, Helmholtz Zentrum München - German Research Center for Environmental Health, Ingolstädter Landstraße 1, D-85764 Neuherberg, Germany
| | - Michael K Jahn
- Institute of Groundwater Ecology, Helmholtz Zentrum München - German Research Center for Environmental Health, Ingolstädter Landstraße 1, D-85764 Neuherberg, Germany
| | - Tillmann Lueders
- Institute of Groundwater Ecology, Helmholtz Zentrum München - German Research Center for Environmental Health, Ingolstädter Landstraße 1, D-85764 Neuherberg, Germany
| | - Roland Geyer
- Department of Environmental Microbiology, Helmholtz Center for Environmental Research - UFZ, Permoserstraße 15, D-04318 Leipzig, Germany
| | - Hermann J Heipieper
- Department of Bioremediation, Helmholtz Center for Environmental Research - UFZ, Permoserstraße 15, D-04318 Leipzig, Germany
| | - Rainer U Meckenstock
- Institute of Groundwater Ecology, Helmholtz Zentrum München - German Research Center for Environmental Health, Ingolstädter Landstraße 1, D-85764 Neuherberg, Germany
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128
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Puyol D, Mohedano AF, Sanz JL, Rodríguez JJ. Comparison of UASB and EGSB performance on the anaerobic biodegradation of 2,4-dichlorophenol. CHEMOSPHERE 2009; 76:1192-1198. [PMID: 19577792 DOI: 10.1016/j.chemosphere.2009.06.015] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2009] [Revised: 06/03/2009] [Accepted: 06/04/2009] [Indexed: 05/28/2023]
Abstract
The anaerobic degradation of 2,4-dichlorophenol (2,4-DCP) in upflow anaerobic sludge blanket (UASB) and expanded granular sludge bed (EGSB) reactors using glucose as main carbon source was studied. The performance of both systems was compared in terms of 2,4-DCP and COD removal efficiencies, methane production, stability, granular sludge adaptability as well as reversion of the bacterial inhibition. Both organic and 2,4-DCP loading rates were incrementally varied through the experiments. With loading rates of 1.9 gCODL(-1)d(-1) and 100mg 2,4-DCP L(-1)d(-1), 75% and 84% removal efficiencies of this compound, accompanied by COD consumption efficiencies of 61% and 80% were achieved in the UASB and EGSB reactors, respectively. In these conditions, methane production reached 0.088 L CH(4)g(-1) COD in the EGSB reactor whereas in the UASB reactor was almost negligible. Decreasing the 2,4-DCP loading rate to 30 mgL(-1)d(-1) an improvement in the methane production was observed in both reactors (methanogenic activity of 0.148 and 0.192 L CH(4)g(-1) COD in UASB and EGSB reactors, respectively). Efficiency of dechlorination was improved in both reactors from around 30% to 80% by reducing to one-half the COD due to a decreasing of the 4-chlorophenol concentration accumulated in the effluents of both reactors. The dechlorination efficiency of the UASB reactor was dramatically inhibited at a 2,4-DCP feed concentration above around 210 mgL(-1) because of 2,4-DCP accumulation in the effluent. SEM studies revealed no significant morphological changes in the sludge granules.
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Affiliation(s)
- D Puyol
- Ingeniería Química, Facultad de Ciencias, Universidad Autónoma de Madrid, 28049 Madrid, Spain.
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129
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Functional characterization of the trigger factor protein PceT of tetrachloroethene-dechlorinating Desulfitobacterium hafniense Y51. Appl Microbiol Biotechnol 2009; 83:775-81. [DOI: 10.1007/s00253-009-1958-z] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2009] [Revised: 03/09/2009] [Accepted: 03/10/2009] [Indexed: 10/20/2022]
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130
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Noncanonical vancomycin resistance cluster from Desulfitobacterium hafniense Y51. Antimicrob Agents Chemother 2009; 53:2841-5. [PMID: 19414574 DOI: 10.1128/aac.01408-08] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The glycopeptide vancomycin is a drug of last resort for infection with gram-positive organisms, and three genes are vital to resistance: vanH, vanA, and vanX. These genes are found in a vanHAX cluster, which is conserved across pathogenic bacteria, glycopeptide antibiotic producers, and other environmental bacteria. The genome sequence of the anaerobic, gram-positive, dehalogenating bacterium Desulfitobacterium hafniense Y51 revealed a predicted vanA homolog; however, it exists in a vanAWK-murFX cluster, unlike those of other vancomycin-resistant organisms. Using purified recombinant VanA from D. hafniense Y51, we determined its substrate specificity and found it to have a 42-fold preference for D-lactate over D-alanine, confirming its activity as a D-Ala-D-Lac ligase and its annotation as VanA. Furthermore, we showed that D. hafniense Y51 is highly resistant to vancomycin, with a MIC for growth of 64 microg/ml. Finally, vanA(Dh) is expressed during growth in vancomycin, as demonstrated by reverse transcription-PCR. This finding represents a new glycopeptide antibiotic resistance gene cluster and expands the genetic diversity of resistance to this important class of antibiotic.
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131
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Tracking functional guilds: "Dehalococcoides" spp. in European river basins contaminated with hexachlorobenzene. Appl Environ Microbiol 2009; 75:4696-704. [PMID: 19376891 DOI: 10.1128/aem.02829-08] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Hexachlorobenzene (HCB) has been widely used in chemical manufacturing processes and as a pesticide. Due to its resistance to biological degradation, HCB has mainly accumulated in freshwater bodies and agricultural soils. "Dehalococcoides" spp., anaerobic dechlorinating bacteria that are capable of degrading HCB, were previously isolated from river sediments. Yet there is limited knowledge about the abundance, diversity, and activity of this genus in the environment. This study focused on the molecular analysis of the composition and abundance of active Dehalococcoides spp. in HCB-contaminated European river basins. 16S rRNA-based real-time quantitative PCR and denaturing gradient gel electrophoresis in combination with multivariate statistics were applied. Moreover, a functional gene array was used to determine reductive dehalogenase (rdh) gene diversity. Spatial and temporal fluctuations were observed not only in the abundance of Dehalococcoides spp. but also in the composition of the populations and rdh gene diversity. Multivariate statistics revealed that Dehalococcoides sp. abundance is primarily affected by spatial differences, whereas species composition is under the influence of several environmental parameters, such as seasonal changes, total organic carbon and/or nitrogen content, and HCB contamination. This study provides new insight into the natural occurrence and dynamics of active Dehalococcoides spp. in HCB-contaminated river basins.
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132
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Winch S, Mills HJ, Kostka JE, Fortin D, Lean DRS. Identification of sulfate-reducing bacteria in methylmercury-contaminated mine tailings by analysis of SSU rRNA genes. FEMS Microbiol Ecol 2009; 68:94-107. [PMID: 19291023 DOI: 10.1111/j.1574-6941.2009.00658.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Sulfate-reducing bacteria (SRB) are often used in bioremediation of acid mine drainage because microbial sulfate reduction increases pH and produces sulfide that binds with metals. Mercury methylation has also been linked with sulfate reduction. Previous geochemical analysis indicated the occurrence of sulfate reduction in mine tailings, but no molecular characterization of the mine tailings-associated microbial community has determined which SRB are present. This study characterizes the bacterial communities of two geochemically contrasting, high-methylmercury mine tailing environments, with emphasis on SRB, by analyzing small subunit (SSU) rRNA genes present in the tailings sediments and in enrichment cultures inoculated with tailings. Novel Deltaproteobacteria and Firmicutes-related sequences were detected in both the pH-neutral gold mine tailings and the acidic high-sulfide base-metal tailings. At the subphylum level, the SRB communities differed between sites, suggesting that the community structure was dependent on local geochemistry. Clones obtained from the gold tailings and enrichment cultures were more similar to previously cultured isolates whereas clones from acidic tailings were more closely related to uncultured lineages identified from other acidic sediments worldwide. This study provides new insights into the novelty and diversity of bacteria colonizing mine tailings, and identifies specific organisms that warrant further investigation with regard to their roles in mercury methylation and sulfur cycling in these environments.
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Affiliation(s)
- Susan Winch
- Department of Earth Science, University of Ottawa, Ottawa, ON, Canada.
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133
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Retentive memory of bacteria: Long-term regulation of dehalorespiration in Sulfurospirillum multivorans. J Bacteriol 2008; 191:1650-5. [PMID: 19103925 DOI: 10.1128/jb.00597-08] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The gram-negative, strictly anaerobic epsilonproteobacterium Sulfurospirillum multivorans is able to gain energy from dehalorespiration with tetrachloroethene (perchloroethylene [PCE]) as a terminal electron acceptor. The organism can also utilize fumarate as an electron acceptor. Prolonged subcultivation of S. multivorans in the absence of PCE with pyruvate as an electron donor and fumarate as an electron acceptor resulted in a decrease of PCE dehalogenase (PceA) activity. Concomitantly, the pceA transcript level equally decreased as shown by reverse transcriptase PCR. After 35 subcultivations (approximately 105 generations), a pceA transcript was not detectable and the PceA protein and activity were completely absent. In such long-term subcultivated S. multivorans cells, the biosynthesis of catalytically active PceA was restored to the initial level within about 50 h (approximately three generations) by the addition of PCE or trichloroethene. Single colonies obtained from PceA-depleted cultures were able to induce PCE dechlorination, indicating that long-term subcultured cells still contained the functional pceA gene. The results point to a novel type of long-term regulation of PCE dehalogenase gene expression in S. multivorans.
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134
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Rothery RA, Workun GJ, Weiner JH. The prokaryotic complex iron–sulfur molybdoenzyme family. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2008; 1778:1897-929. [DOI: 10.1016/j.bbamem.2007.09.002] [Citation(s) in RCA: 144] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2007] [Revised: 08/17/2007] [Accepted: 09/02/2007] [Indexed: 10/22/2022]
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135
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Levy C, Pike K, Heyes DJ, Joyce MG, Gabor K, Smidt H, van der Oost J, Leys D. Molecular basis of halorespiration control by CprK, a CRP-FNR type transcriptional regulator. Mol Microbiol 2008; 70:151-67. [PMID: 18717788 PMCID: PMC2610375 DOI: 10.1111/j.1365-2958.2008.06399.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Certain bacteria are able to conserve energy via the reductive dehalogenation of halo-organic compounds in a respiration-type metabolism. The transcriptional regulator CprK from Desulfitobacterium spp. induces expression of halorespiratory genes upon binding of o-chlorophenol ligands and is reversibly inactivated by oxygen through disulphide bond formation. We report crystal structures of D. hafniense CprK in the ligand-free (both oxidation states), ligand-bound (reduced) and DNA-bound states, making it the first member of the widespread CRP-FNR superfamily for which a complete structural description of both redox-dependent and allosteric molecular rearrangements is available. In conjunction with kinetic and thermodynamic ligand binding studies, we provide a model for the allosteric mechanisms underpinning transcriptional control. Amino acids that play a key role in this mechanism are not conserved in functionally distinct CRP-FNR members. This suggests that, despite significant structural homology, distinct allosteric mechanisms are used, enabling this protein family to control a very wide range of processes.
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Affiliation(s)
- Colin Levy
- Manchester Interdisciplinary Biocentre, The University of Manchester, Manchester M1 7DN, UK
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136
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Resolution of culture Clostridium bifermentans DPH-1 into two populations, a Clostridium sp. and tetrachloroethene-dechlorinating Desulfitobacterium hafniense strain JH1. Appl Environ Microbiol 2008; 74:6141-3. [PMID: 18708512 DOI: 10.1128/aem.00994-08] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Clostridium bifermentans strain DPH-1 reportedly dechlorinates tetrachloroethene (PCE) to cis-1,2-dichloroethene. Cultivation-based approaches resolved the DPH-1 culture into two populations: a nondechlorinating Clostridium sp. and PCE-dechlorinating Desulfitobacterium hafniense strain JH1. Strain JH1 carries pceA, encoding a PCE reductive dehalogenase, and shares other characteristics with Desulfitobacterium hafniense strain Y51.
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137
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Gupta N, Ragsdale SW. Dual roles of an essential cysteine residue in activity of a redox-regulated bacterial transcriptional activator. J Biol Chem 2008; 283:28721-8. [PMID: 18687692 DOI: 10.1074/jbc.m800630200] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
CprK from Desulfitobacterium dehalogenans is the first characterized transcriptional regulator of anaerobic dehalorespiration and is controlled at two levels: redox and effector binding. In the reduced state and in the presence of chlorinated aromatic compounds, CprK positively regulates expression of the cpr gene cluster. One of the products of the cpr gene cluster is CprA, which catalyzes the reductive dehalogenation of chlorinated aromatic compounds. Redox regulation of CprK occurs through a thiol/disulfide redox switch, which includes two classes of cysteine residues. Under oxidizing conditions, Cys11 and Cys200 form an intermolecular disulfide bond, whereas Cys105 and Cys111 form an intramolecular disulfide. Here, we report that Cys11 is involved in redox inactivation in vivo. Upon replacement of Cys11 with serine, alanine, or aspartate, CprK loses its DNA binding activity. C11A is unstable; however, circular dichroism studies demonstrate that the stability and overall secondary structures of CprK and the C11S and C11D variants are similar. Furthermore, effector binding remains intact in the C11S and C11D variants. However, fluorescence spectroscopic results reveal that the tertiary structures of the C11S and C11D variants differ from that of the wild type protein. Thus, Cys11 plays a dual role as a redox switch and in maintaining the correct tertiary structure that promotes DNA binding.
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Affiliation(s)
- Nirupama Gupta
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Mighigan 48109-0606, USA
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138
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Mun CH, Ng WJ, He J. Acidogenic sequencing batch reactor start-up procedures for induction of 2,4,6-trichlorophenol dechlorination. WATER RESEARCH 2008; 42:1675-1683. [PMID: 18022668 DOI: 10.1016/j.watres.2007.10.019] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2007] [Revised: 10/14/2007] [Accepted: 10/16/2007] [Indexed: 05/25/2023]
Abstract
Dechlorination of 2,4,6-trichlorophenol to 4-chlorophenol under acidogenic conditions (pH 5.6-6.5) was successfully induced by manipulating the start-up procedure of an acidogenic sequencing batch reactor (SBR). A stepwise pH reduction from neutral to acidic level during start-up was crucial for inducing dechlorination. Once induced, dechlorination can proceed at pH as low as 5.6 before inhibition occurs. Optimum pH for maximum dechlorination rate ranged from 6.0 to 6.3. High primary (sucrose) to secondary (2,4,6-trichlorophenol) substrate ratio failed to induce dechlorination. Instead, dechlorination occurred at primary to secondary substrate ratios of less than 103M/M. A specific maximum trichlorophenol loading rate of 60micromol/g MLVSSd was achieved before inhibition appeared with onset of acidogenic reactor failure. T-RFLP profile analysis gave evidence that the start-up procedure resulted in the selection of an appropriate microbial community, which resulted in the successful development of an acidogenic consortium capable of degrading 2,4,6-trichlorophenol.
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Affiliation(s)
- Cheok Hong Mun
- Division of Environmental Science & Engineering, National University of Singapore, Singapore.
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139
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Futagami T, Goto M, Furukawa K. Biochemical and genetic bases of dehalorespiration. CHEM REC 2008; 8:1-12. [DOI: 10.1002/tcr.20134] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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140
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Kunapuli U, Lueders T, Meckenstock RU. The use of stable isotope probing to identify key iron-reducing microorganisms involved in anaerobic benzene degradation. ISME JOURNAL 2007; 1:643-53. [PMID: 18043671 DOI: 10.1038/ismej.2007.73] [Citation(s) in RCA: 167] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Here, we present a detailed functional and phylogenetic characterization of an iron-reducing enrichment culture maintained in our lab with benzene as sole carbon and energy source. We used DNA-stable isotope probing to identify microbes within the enrichment most active in the assimilation of (13)C-label. When (12)C(6)- and (13)C(6)-benzene were added as comparative substrates, marked differences in the quantitative buoyant density distribution became apparent especially for uncultured microbes within the Gram-positive Peptococcaceae, closely related to environmental clones retrieved from contaminated aquifers world wide and only distantly related to cultured representatives of the genus Thermincola. Prominent among the other constituents of the enrichment were uncultured Deltaproteobacteria, as well as members of the Actinobacteria. Although their presence within the enrichment seems to be stable they did not assimilate (13)C-label as significantly as the Clostridia within the time course of our experiment. We hypothesize that benzene degradation in our enrichment involves an unusual syntrophy, where members of the Clostridia primarily oxidize benzene. Electrons from the contaminant are both directly transferred to ferric iron by the primary oxidizers, but also partially shared with the Desulfobulbaceae as syntrophic partners. Alternatively, electrons may also be quantitatively transferred to the partners, which then reduce the ferric iron. Thus our results provide evidence for the importance of a novel clade of Gram-positive iron-reducers in anaerobic benzene degradation, and a role of syntrophic interactions in this process. These findings shed a totally new light on the factors controlling benzene degradation in anaerobic contaminated environments.
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Affiliation(s)
- Umakanth Kunapuli
- GSF-National Research Center for Environment and Health, Institute of Groundwater Ecology, Neuherberg, Germany
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141
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Villemur R, Constant P, Gauthier A, Shareck M, Beaudet R. Heterogeneity between 16S ribosomal RNA gene copies borne by oneDesulfitobacteriumstrain is caused by different 100-200 bp insertions in the 5´ region. Can J Microbiol 2007; 53:116-28. [PMID: 17496957 DOI: 10.1139/w06-111] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Strains of Desulfitobacterium hafniense, such as strains PCP-1, DP7, TCE1, and TCP-A, have unusual long 16S ribosomal RNA (rRNA) genes due to an insertion of approximately 100 bp in the 5' region. In this report, we analyzed the 16S rRNA genes of different Desulfitobacterium strains to determine if such an insertion is a common feature of desulfitobacteria. We amplified this region by polymerase chain reaction (PCR) from eight Desulfitobacterium strains (D. hafniense strains PCP-1, DP7, TCP-A, TCE1, and DCB-2; D. dehalogenans; D. chlororespirans; and Desulfitobacterium sp. PCE1) and resolved each PCR product by denaturing gradient gel electrophoresis (DGGE). All strains had from two to seven DGGE- migrating bands, suggesting heterogeneity in their 16S rRNA gene copies. For each strain, the 5' region of the 16S rRNA genes was amplified and a clone library was derived. Clones corresponding to most PCR–DGGE migration bands were isolated. Sequencing of representative clones revealed that the heterogeneity was generated by insertions of 100–200 bp. An insertion was found in at least one copy of the 16S rRNA gene in all examined strains. In total, we found eight different types of insertions (INS1–INS8) that varied from 123 to 193 nt in length. Two-dimensional structural analyses of transcribed sequences predicted that all insertions would form an energetically stable loop. Reverse transcriptase – PCR experiments revealed that most of the observed insertions in the Desulfitobacterium strains were excised from the mature 16S rRNA transcripts. Insertions were not commonly found in bacterial 16S rRNA genes, and having a different insertion in several 16S rRNA gene copies borne by a single bacterial species was rarely observed. The function of these insertions is not known, but their occurrence can have an important impact in deriving 16S rRNA oligonucleotidic fluorescence in situ hybridization probes, as these insertions can be excised from 16S rRNA transcripts.Key words: Desulfitobacterium, 16S ribosomal RNA genes, heterogeneity, gene insertions, fluorescence in situ hybridization.
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