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Williams TJ, Allen MA, Ray AE, Benaud N, Chelliah DS, Albanese D, Donati C, Selbmann L, Coleine C, Ferrari BC. Novel endolithic bacteria of phylum Chloroflexota reveal a myriad of potential survival strategies in the Antarctic desert. Appl Environ Microbiol 2024; 90:e0226423. [PMID: 38372512 PMCID: PMC10952385 DOI: 10.1128/aem.02264-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Accepted: 01/02/2024] [Indexed: 02/20/2024] Open
Abstract
The ice-free McMurdo Dry Valleys of Antarctica are dominated by nutrient-poor mineral soil and rocky outcrops. The principal habitat for microorganisms is within rocks (endolithic). In this environment, microorganisms are provided with protection against sub-zero temperatures, rapid thermal fluctuations, extreme dryness, and ultraviolet and solar radiation. Endolithic communities include lichen, algae, fungi, and a diverse array of bacteria. Chloroflexota is among the most abundant bacterial phyla present in these communities. Among the Chloroflexota are four novel classes of bacteria, here named Candidatus Spiritibacteria class. nov. (=UBA5177), Candidatus Martimicrobia class. nov. (=UBA4733), Candidatus Tarhunnaeia class. nov. (=UBA6077), and Candidatus Uliximicrobia class. nov. (=UBA2235). We retrieved 17 high-quality metagenome-assembled genomes (MAGs) that represent these four classes. Based on genome predictions, all these bacteria are inferred to be aerobic heterotrophs that encode enzymes for the catabolism of diverse sugars. These and other organic substrates are likely derived from lichen, algae, and fungi, as metabolites (including photosynthate), cell wall components, and extracellular matrix components. The majority of MAGs encode the capacity for trace gas oxidation using high-affinity uptake hydrogenases, which could provide energy and metabolic water required for survival and persistence. Furthermore, some MAGs encode the capacity to couple the energy generated from H2 and CO oxidation to support carbon fixation (atmospheric chemosynthesis). All encode mechanisms for the detoxification and efflux of heavy metals. Certain MAGs encode features that indicate possible interactions with other organisms, such as Tc-type toxin complexes, hemolysins, and macroglobulins.IMPORTANCEThe ice-free McMurdo Dry Valleys of Antarctica are the coldest and most hyperarid desert on Earth. It is, therefore, the closest analog to the surface of the planet Mars. Bacteria and other microorganisms survive by inhabiting airspaces within rocks (endolithic). We identify four novel classes of phylum Chloroflexota, and, based on interrogation of 17 metagenome-assembled genomes, we predict specific metabolic and physiological adaptations that facilitate the survival of these bacteria in this harsh environment-including oxidation of trace gases and the utilization of nutrients (including sugars) derived from lichen, algae, and fungi. We propose that such adaptations allow these endolithic bacteria to eke out an existence in this cold and extremely dry habitat.
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Affiliation(s)
- Timothy J. Williams
- School of Biotechnology and Biomolecular Sciences, UNSW Sydney, Sydney, New South Wales, Australia
| | - Michelle A. Allen
- School of Biological, Earth and Environmental Sciences, UNSW Sydney, Sydney, New South Wales, Australia
| | - Angelique E. Ray
- School of Biotechnology and Biomolecular Sciences, UNSW Sydney, Sydney, New South Wales, Australia
| | - Nicole Benaud
- School of Biotechnology and Biomolecular Sciences, UNSW Sydney, Sydney, New South Wales, Australia
| | - Devan S. Chelliah
- School of Biotechnology and Biomolecular Sciences, UNSW Sydney, Sydney, New South Wales, Australia
| | - Davide Albanese
- Research and Innovation Center, Fondazione Edmund Mach, San Michele all’Adige, Italy
| | - Claudio Donati
- Research and Innovation Center, Fondazione Edmund Mach, San Michele all’Adige, Italy
| | - Laura Selbmann
- Department of Ecological and Biological Sciences, University of Tuscia, Largo dell’Università, Viterbo, Italy
- Mycological Section, Italian Antarctic National Museum (MNA), Genova, Italy
| | - Claudia Coleine
- Department of Ecological and Biological Sciences, University of Tuscia, Largo dell’Università, Viterbo, Italy
| | - Belinda C. Ferrari
- School of Biotechnology and Biomolecular Sciences, UNSW Sydney, Sydney, New South Wales, Australia
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Watanabe T, Yabe T, Tsuji JM, Fukui M. Desulfoferula mesophilus gen. nov. sp. nov., a mesophilic sulfate-reducing bacterium isolated from a brackish lake sediment. Arch Microbiol 2023; 205:368. [PMID: 37923857 DOI: 10.1007/s00203-023-03711-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2023] [Revised: 10/13/2023] [Accepted: 10/14/2023] [Indexed: 11/06/2023]
Abstract
A novel sulfate-reducing bacterium (strain 12FAKT) was isolated from sediment sampled from a brackish lake in Japan. Respiratory growth was observed with formate and pyruvate as an electron donor. Sulfate, thiosulfate, elemental sulfur and dimethyl sulfoxide were utilized as an electron acceptor. The isolate grew over a temperature range of 18-42 °C (optimum 35-37 °C), a NaCl concentration range of 50-450 mM (optimum 150-300 mM) and a pH range of 6.6-7.5. The 12FAKT genome consists of a circular chromosome with a length of 4.5 Mbp and G + C content of 63.6%. Based on 16S rRNA gene sequence similarity, the closest cultured relative was Desulfarculus baarsii 2st14T (92.2%). Genome-based phylogenetic analysis placed strain 12FAKT within the family Desulfarculaceae but did not affiliate the strain with any existing genus. Taken together, we propose a novel species of a novel genus, Desulfoferula mesophilus gen. nov. sp. nov. with the type strain 12FAKT (= DSM 115219T = JCM 39399T).
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Affiliation(s)
- Tomohiro Watanabe
- The Institute of Low Temperature Science, Hokkaido University, Kita-19, Nishi-8, Kita-ku, Sapporo, 060-0819, Japan.
| | - Tatsuya Yabe
- The Institute of Low Temperature Science, Hokkaido University, Kita-19, Nishi-8, Kita-ku, Sapporo, 060-0819, Japan
- Graduate School of Environmental Science, Hokkaido University, Kita-10, Nishi-5, Kita-ku, Sapporo, 060-0810, Japan
| | - Jackson M Tsuji
- The Institute of Low Temperature Science, Hokkaido University, Kita-19, Nishi-8, Kita-ku, Sapporo, 060-0819, Japan
- Japan Agency for Marine-Earth Science and Technology, 2-15 Natsushima, Yokosuka, Kanagawa, Japan
| | - Manabu Fukui
- The Institute of Low Temperature Science, Hokkaido University, Kita-19, Nishi-8, Kita-ku, Sapporo, 060-0819, Japan
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Ventura J, Camargo FP, Sakamoto IK, Silva EL, Varesche MBA. Potential methanogenic and degradation of nonylphenol ethoxylate from domestic sewage: unravelling the essential roles of nutritional conditions and microbial community. ENVIRONMENTAL TECHNOLOGY 2023; 44:1996-2010. [PMID: 34907848 DOI: 10.1080/09593330.2021.2018504] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Accepted: 12/07/2021] [Indexed: 05/25/2023]
Abstract
Nonylphenol ethoxylathe (NPEO) is a non-ionic surfactant of increasing concern, used in the formulation of laundry detergents and is frequently found in aquatic environments. The purpose of this study was to evaluate the effects of yeast extract (YE) and sodium fumarate (SF) in NPEO removal from domestic sewage under anaerobic conditions via central composite rotatable design (CCRD) and response surface methodology (RSM). Experiments were designed by varying concentrations of NPEO (1.6-5.8 mg L-1), YE (131.8-468.2 mg L-1) and SF (97.7-602.3 mg L-1) in batch reactors. SF and YE addition significantly influenced NPEO removal and CH4 production. Optimal values of YE (400 mg L-1) and SF (200 mg L-1) result in removal efficiency of 97% for 5 mg L-1 of NPEO, being mostly removed by biodegradation (86%). Meanwhile COD removal was 95% and methane yield was 134 ± 4 NmLCH4 g-¹CODremoved. The most abundant Bacteria genus identified were Macellibacteroides, Longilinea, Petrimonas and Proteiniphilum, while for Archaea, Methanosaeta and Methanoregula were the genera identified in higher relative abundances in optimized conditions.
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Affiliation(s)
- Jeny Ventura
- Department of Hydraulics and Sanitation, School of Engineering of São Carlos, University of São Paulo, Av. João Dagnone 1100, Jardim Santa Angelina, São Carlos 13563120, Brazil
| | - Franciele Pereira Camargo
- Department of Hydraulics and Sanitation, School of Engineering of São Carlos, University of São Paulo, Av. João Dagnone 1100, Jardim Santa Angelina, São Carlos 13563120, Brazil
| | - Isabel Kimiko Sakamoto
- Department of Hydraulics and Sanitation, School of Engineering of São Carlos, University of São Paulo, Av. João Dagnone 1100, Jardim Santa Angelina, São Carlos 13563120, Brazil
| | - Edson Luiz Silva
- Federal University of São Carlos, Chemical Engineering, São Carlos, Brazil
| | - Maria Bernadete Amâncio Varesche
- Department of Hydraulics and Sanitation, School of Engineering of São Carlos, University of São Paulo, Av. João Dagnone 1100, Jardim Santa Angelina, São Carlos 13563120, Brazil
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Williams K, Szwalbe AJ, de Mattos-Shipley KMJ, Bailey AM, Cox RJ, Willis CL. Maleidride biosynthesis - construction of dimeric anhydrides - more than just heads or tails. Nat Prod Rep 2023; 40:128-157. [PMID: 36129067 PMCID: PMC9890510 DOI: 10.1039/d2np00041e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Covering: up to early 2022Maleidrides are a family of polyketide-based dimeric natural products isolated from fungi. Many maleidrides possess significant bioactivities, making them attractive pharmaceutical or agrochemical lead compounds. Their unusual biosynthetic pathways have fascinated scientists for decades, with recent advances in our bioinformatic and enzymatic understanding providing further insights into their construction. However, many intriguing questions remain, including exactly how the enzymatic dimerisation, which creates the diverse core structure of the maleidrides, is controlled. This review will explore the literature from the initial isolation of maleidride compounds in the 1930s, through the first full structural elucidation in the 1960s, to the most recent in vivo, in vitro, and in silico analyses.
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Affiliation(s)
- Katherine Williams
- School of Biological Sciences, Life Sciences Building, University of Bristol, 24 Tyndall Ave, Bristol BS8 1TQ, UK.
| | | | | | - Andy M. Bailey
- School of Biological Sciences, Life Sciences Building, University of Bristol24 Tyndall AveBristol BS8 1TQUK
| | - Russell J. Cox
- Institute for Organic Chemistry and BMWZ, Leibniz University of HannoverSchneiderberg 3830167HannoverGermany
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Williams TJ, Allen MA, Panwar P, Cavicchioli R. Into the darkness: The ecologies of novel 'microbial dark matter' phyla in an Antarctic lake. Environ Microbiol 2022; 24:2576-2603. [PMID: 35466505 PMCID: PMC9324843 DOI: 10.1111/1462-2920.16026] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 04/18/2022] [Accepted: 04/20/2022] [Indexed: 11/29/2022]
Abstract
Uncultivated microbial clades ("microbial dark matter") are inferred to play important, but uncharacterized roles in nutrient cycling. Using Antarctic lake (Ace Lake, Vestfold Hills) metagenomes, 12 metagenome-assembled genomes (MAGs; 88-100% complete) were generated for four "dark matter" phyla: six MAGs from Candidatus Auribacterota (= Aureabacteria, SURF-CP-2), inferred to be hydrogen- and sulfide-producing fermentative heterotrophs, with individual MAGs encoding bacterial microcompartments (BMCs), gas vesicles, and type IV pili; one MAG (100% complete) from Candidatus Hinthialibacterota (= OLB16), inferred to be a facultative anaerobe capable of dissimilatory nitrate reduction to ammonia, specialized for mineralization of complex organic matter (e.g., sulfated polysaccharides), and encoding BMCs, flagella, and Tad pili; three MAGs from Candidatus Electryoneota (= AABM5-125-24), previously reported to include facultative anaerobes capable of dissimilatory sulfate reduction, and here inferred to perform sulfite oxidation, reverse tricarboxylic acid cycle for autotrophy, and possess numerous proteolytic enzymes; two MAGs from Candidatus Lernaellota (= FEN-1099), inferred to be capable of formate oxidation, amino acid fermentation, and possess numerous enzymes for protein and polysaccharide degradation. The presence of 16S rRNA gene sequences in public metagenome datasets (88-100% identity) suggests these "dark matter" phyla contribute to sulfur cycling, degradation of complex organic matter, ammonification and/or chemolithoautrophic CO2 fixation in diverse global environments. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Timothy J Williams
- School of Biotechnology and Biomolecular Sciences UNSW Sydney, Sydney, New South Wales, 2052, Australia
| | - Michelle A Allen
- School of Biotechnology and Biomolecular Sciences UNSW Sydney, Sydney, New South Wales, 2052, Australia
| | - Pratibha Panwar
- School of Biotechnology and Biomolecular Sciences UNSW Sydney, Sydney, New South Wales, 2052, Australia
| | - Ricardo Cavicchioli
- School of Biotechnology and Biomolecular Sciences UNSW Sydney, Sydney, New South Wales, 2052, Australia
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Abstract
Anaerobic ammonium oxidation (anammox) is important for converting bioavailable nitrogen into dinitrogen gas, particularly in carbon-poor environments. However, the diversity and prevalence of anammox bacteria in the terrestrial subsurface-a typically oligotrophic environment-are little understood. To determine the distribution and activity of anammox bacteria across a range of aquifer lithologies and physicochemistries, we analyzed 16S rRNA genes and quantified hydrazine synthase genes and transcripts sampled from 59 groundwater wells and metagenomes and metatranscriptomes from an oxic-to-dysoxic subset. Data indicate that anammox and anammox-associated bacteria (class "Candidatus Brocadiae") are prevalent in the aquifers studied, and that anammox community composition is strongly differentiated by dissolved oxygen (DO), but not ammonia/nitrite. While "Candidatus Brocadiae" diversity decreased with increasing DO, "Candidatus Brocadiae" 16S rRNA genes and hydrazine synthase (hzsB) genes and transcripts were detected across a wide range of bulk groundwater DO concentrations (0 to 10 mg/L). Anammox genes and transcripts correlated significantly with those involved in aerobic ammonia oxidation (amoA), potentially representing a major source of nitrite for anammox. Eight "Candidatus Brocadiae" genomes (63 to 95% complete), representing 2 uncharacterized families and 6 novel species, were reconstructed. Six genomes have genes characteristic of anammox, all for chemolithoautotrophy. Anammox and aerotolerance genes of up to four "Candidatus Brocadiae" genomes were transcriptionally active under oxic and dysoxic conditions, although activity was highest in dysoxic groundwater. The coexpression of nrfAH nitrite reductase genes by "Candidatus Brocadiae" suggests active regeneration of ammonia for anammox. Our findings indicate that anammox bacteria contribute to loss of fixed N across diverse anoxic-to-oxic aquifer conditions, which is likely supported by nitrite from aerobic ammonia oxidation. IMPORTANCE Anammox is increasingly shown to play a major role in the aquatic nitrogen cycle and can outcompete heterotrophic denitrification in environments low in organic carbon. Given that aquifers are characteristically oligotrophic, anammox may represent a major route for the removal of fixed nitrogen in these environments, including agricultural nitrogen, a common groundwater contaminant. Our research confirms that anammox bacteria and the anammox process are prevalent in aquifers and occur across diverse lithologies (e.g., sandy gravel, sand-silt, and volcanic) and groundwater physicochemistries (e.g., various oxygen, carbon, nitrate, and ammonium concentrations). Results reveal niche differentiation among anammox bacteria largely driven by groundwater oxygen contents and provide evidence that anammox is supported by proximity to oxic niches and handoffs from aerobic ammonia oxidizers. We further show that this process, while anaerobic, is active in groundwater characterized as oxic, likely due to the availability of anoxic niches.
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Williams TJ, Allen MA, Berengut JF, Cavicchioli R. Shedding Light on Microbial "Dark Matter": Insights Into Novel Cloacimonadota and Omnitrophota From an Antarctic Lake. Front Microbiol 2021; 12:741077. [PMID: 34707591 PMCID: PMC8542988 DOI: 10.3389/fmicb.2021.741077] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Accepted: 09/13/2021] [Indexed: 11/13/2022] Open
Abstract
The potential metabolism and ecological roles of many microbial taxa remain unknown because insufficient genomic data are available to assess their functional potential. Two such microbial "dark matter" taxa are the Candidatus bacterial phyla Cloacimonadota and Omnitrophota, both of which have been identified in global anoxic environments, including (but not limited to) organic-carbon-rich lakes. Using 24 metagenome-assembled genomes (MAGs) obtained from an Antarctic lake (Ace Lake, Vestfold Hills), novel lineages and novel metabolic traits were identified for both phyla. The Cloacimonadota MAGs exhibited a capacity for carbon fixation using the reverse tricarboxylic acid cycle driven by oxidation of hydrogen and sulfur. Certain Cloacimonadota MAGs encoded proteins that possess dockerin and cohesin domains, which is consistent with the assembly of extracellular cellulosome-like structures that are used for degradation of polypeptides and polysaccharides. The Omnitrophota MAGs represented phylogenetically diverse taxa that were predicted to possess a strong biosynthetic capacity for amino acids, nucleosides, fatty acids, and essential cofactors. All of the Omnitrophota were inferred to be obligate fermentative heterotrophs that utilize a relatively narrow range of organic compounds, have an incomplete tricarboxylic acid cycle, and possess a single hydrogenase gene important for achieving redox balance in the cell. We reason that both Cloacimonadota and Omnitrophota form metabolic interactions with hydrogen-consuming partners (methanogens and Desulfobacterota, respectively) and, therefore, occupy specific niches in Ace Lake.
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Affiliation(s)
- Timothy J Williams
- School of Biotechnology and Biomolecular Sciences, UNSW Sydney, Sydney, NSW, Australia
| | - Michelle A Allen
- School of Biotechnology and Biomolecular Sciences, UNSW Sydney, Sydney, NSW, Australia
| | - Jonathan F Berengut
- EMBL Australia Node for Single Molecule Science, School of Medical Sciences, UNSW Sydney, Kensington, NSW, Australia
| | - Ricardo Cavicchioli
- School of Biotechnology and Biomolecular Sciences, UNSW Sydney, Sydney, NSW, Australia
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McCully AL, Onyeziri MC, LaSarre B, Gliessman JR, McKinlay JB. Reductive tricarboxylic acid cycle enzymes and reductive amino acid synthesis pathways contribute to electron balance in a Rhodospirillum rubrum Calvin-cycle mutant. MICROBIOLOGY-SGM 2020; 166:199-211. [PMID: 31774392 DOI: 10.1099/mic.0.000877] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Purple non-sulfur bacteria (PNSB) use light for energy and organic substrates for carbon and electrons when growing photoheterotrophically. This lifestyle generates more reduced electron carriers than are required for biosynthesis, even during consumption of some of the most oxidized organic substrates like malate and fumarate. Reduced electron carriers not used in biosynthesis must still be oxidized for photoheterotrophic growth to occur. Diverse PNSB commonly rely on the CO2-fixing Calvin cycle to oxidize reduced electron carriers. Some PNSB also produce H2 or reduce terminal electron acceptors as alternatives to the Calvin cycle. Rhodospirillum rubrum Calvin-cycle mutants defy this trend by growing phototrophically on malate or fumarate without H2 production or access to terminal electron acceptors. We used 13C-tracer experiments to examine how a Rs. rubrum Calvin-cycle mutant maintains electron balance under such conditions. We detected the reversal of some tricarboxylic acid cycle enzymes, carrying reductive flux from malate or fumarate to αKG. This pathway and the reductive synthesis of αKG-derived amino acids are likely important for electron balance, as supplementing the growth medium with αKG-derived amino acids prevented Rs. rubrum Calvin-cycle-mutant growth unless a terminal electron acceptor was provided. Flux estimates also suggested that the Calvin-cycle mutant preferentially synthesized isoleucine using the reductive threonine-dependent pathway instead of the less-reductive citramalate-dependent pathway. Collectively, our results suggest that alternative biosynthetic pathways can contribute to electron balance within the constraints of a relatively constant biomass composition.
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Affiliation(s)
- Alexandra L McCully
- Present address: Department of Civil and Environmental Engineering, Stanford University, Stanford, CA 94305, USA.,Department of Biology, Indiana University, Bloomington, IN 47405, USA
| | | | - Breah LaSarre
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
| | | | - James B McKinlay
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
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Autotrophic and mixotrophic metabolism of an anammox bacterium revealed by in vivo 13C and 2H metabolic network mapping. ISME JOURNAL 2020; 15:673-687. [PMID: 33082573 PMCID: PMC8027424 DOI: 10.1038/s41396-020-00805-w] [Citation(s) in RCA: 51] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Revised: 09/23/2020] [Accepted: 10/02/2020] [Indexed: 12/20/2022]
Abstract
Anaerobic ammonium-oxidizing (anammox) bacteria mediate a key step in the biogeochemical nitrogen cycle and have been applied worldwide for the energy-efficient removal of nitrogen from wastewater. However, outside their core energy metabolism, little is known about the metabolic networks driving anammox bacterial anabolism and use of different carbon and energy substrates beyond genome-based predictions. Here, we experimentally resolved the central carbon metabolism of the anammox bacterium Candidatus ‘Kuenenia stuttgartiensis’ using time-series 13C and 2H isotope tracing, metabolomics, and isotopically nonstationary metabolic flux analysis. Our findings confirm predicted metabolic pathways used for CO2 fixation, central metabolism, and amino acid biosynthesis in K. stuttgartiensis, and reveal several instances where genomic predictions are not supported by in vivo metabolic fluxes. This includes the use of the oxidative branch of an incomplete tricarboxylic acid cycle for alpha-ketoglutarate biosynthesis, despite the genome not having an annotated citrate synthase. We also demonstrate that K. stuttgartiensis is able to directly assimilate extracellular formate via the Wood–Ljungdahl pathway instead of oxidizing it completely to CO2 followed by reassimilation. In contrast, our data suggest that K. stuttgartiensis is not capable of using acetate as a carbon or energy source in situ and that acetate oxidation occurred via the metabolic activity of a low-abundance microorganism in the bioreactor’s side population. Together, these findings provide a foundation for understanding the carbon metabolism of anammox bacteria at a systems-level and will inform future studies aimed at elucidating factors governing their function and niche differentiation in natural and engineered ecosystems.
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Biochemical characterization of 2-phosphinomethylmalate synthase from Streptomyces hygroscopicus: A member of the DRE-TIM metallolyase superfamily. Arch Biochem Biophys 2020; 691:108489. [PMID: 32697946 DOI: 10.1016/j.abb.2020.108489] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Revised: 07/06/2020] [Accepted: 07/07/2020] [Indexed: 11/23/2022]
Abstract
2-Phosphinomethylmalate synthase (PMMS) from Streptomyces hygroscopicus catalyzes the first step in the biosynthesis of the herbicide bialophos using 3-phosphinopyruvic acid and acetyl coenzyme A as substrates to form 2-phosphinomethylmalic acid and coenzyme A. PMMS belongs to the Claisen condensation-like (CC-like) subgroup of the DRE-TIM metallolyase superfamily, which uses conserved active site architecture to catalyze a functionally-diverse set of reactions. Analysis of a sequence similarity network for the CC-like subgroup identified PMMS and the related R-citrate synthase in an early-diverging cluster suggesting that this group of sequences are more distinct in relation to other Claisen-condensation subgroup members. To better understand the structure/function landscape of the CC-like subgroup PMMS was recombinantly expressed in Escherichia coli, purified, and characterized with respect to its enzymatic properties. Using oxaloacetate as a substrate analog, the recombinantly-produced enzyme exhibited improved Michaelis constants relative to the previously reported natively-produced enzyme. Results from pH rate profiles and kinetic isotope effects were consistent with results from other members of the CC-like subgroup supporting acid-base chemistry and hydrolysis of the direct Claisen-condensation product as the rate-determining step. Results of site-directed mutagenesis experiments indicate that PMMS uses an active-site architecture similar to homocitrate synthase to select for a dicarboxylic acid substrate.
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Fincker M, Huber JA, Orphan VJ, Rappé MS, Teske A, Spormann AM. Metabolic strategies of marine subseafloor Chloroflexi inferred from genome reconstructions. Environ Microbiol 2020; 22:3188-3204. [PMID: 32372496 DOI: 10.1111/1462-2920.15061] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2020] [Revised: 04/29/2020] [Accepted: 05/03/2020] [Indexed: 12/20/2022]
Abstract
Uncultured members of the Chloroflexi phylum are highly enriched in numerous subseafloor environments. Their metabolic potential was evaluated by reconstructing 31 Chloroflexi genomes from six different subseafloor habitats. The near ubiquitous presence of enzymes of the Wood-Ljungdahl pathway, electron bifurcation, and ferredoxin-dependent transport-coupled phosphorylation indicated anaerobic acetogenesis was central to their catabolism. Most of the genomes simultaneously contained multiple degradation pathways for complex carbohydrates, detrital protein, aromatic compounds, and hydrogen, indicating the coupling of oxidation of chemically diverse organic substrates to ubiquitous CO2 reduction. Such pathway combinations may confer a fitness advantage in subseafloor environments by enabling these Chloroflexi to act as primary fermenters and acetogens in one microorganism without the need for syntrophic H2 consumption. While evidence for catabolic oxygen respiration was limited to two phylogenetic clusters, the presence of genes encoding putative reductive dehalogenases throughout the phylum expanded the phylogenetic boundary for potential organohalide respiration past the Dehalococcoidia class.
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Affiliation(s)
- Maeva Fincker
- Department of Civil and Environmental Engineering, Stanford University, Stanford, CA, USA
| | - Julie A Huber
- Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
| | - Victoria J Orphan
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA
| | - Michael S Rappé
- Hawaii Institute of Marine Biology, University of Hawaii at Manoa, Kaneohe, HI, USA
| | - Andreas Teske
- Department of Marine Sciences, The University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Alfred M Spormann
- Department of Civil and Environmental Engineering, Stanford University, Stanford, CA, USA.,Department of Chemical Engineering, Stanford University, Stanford, CA, USA
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Uncultured Microbial Phyla Suggest Mechanisms for Multi-Thousand-Year Subsistence in Baltic Sea Sediments. mBio 2019; 10:mBio.02376-18. [PMID: 30992358 PMCID: PMC6469976 DOI: 10.1128/mbio.02376-18] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Much of life on Earth exists in a very slow-growing state, with microbes from deeply buried marine sediments representing an extreme example. These environments are like natural laboratories that have run multi-thousand-year experiments that are impossible to perform in a laboratory. We borrowed some techniques that are commonly used in laboratory experiments and applied them to these natural samples to make hypotheses about how these microbes subsist for so long at low activity. We found that some methods for stabilizing proteins and nucleic acids might be used by many members of the community. We also found evidence for niche differentiation strategies, and possibly cross-feeding, suggesting that even though they are barely growing, complex ecological interactions continue to occur over ultralong timescales. Energy-starved microbes in deep marine sediments subsist at near-zero growth for thousands of years, yet the mechanisms for their subsistence are unknown because no model strains have been cultivated from most of these groups. We investigated Baltic Sea sediments with single-cell genomics, metabolomics, metatranscriptomics, and enzyme assays to identify possible subsistence mechanisms employed by uncultured Atribacteria, Aminicenantes, Actinobacteria group OPB41, Aerophobetes, Chloroflexi, Deltaproteobacteria, Desulfatiglans, Bathyarchaeota, and Euryarchaeota marine group II lineages. Some functions appeared to be shared by multiple lineages, such as trehalose production and NAD+-consuming deacetylation, both of which have been shown to increase cellular life spans in other organisms by stabilizing proteins and nucleic acids, respectively. Other possible subsistence mechanisms differed between lineages, possibly providing them different physiological niches. Enzyme assays and transcripts suggested that Atribacteria and Actinobacteria group OPB41 catabolized sugars, whereas Aminicenantes and Atribacteria catabolized peptides. Metabolite and transcript data suggested that Atribacteria utilized allantoin, possibly as an energetic substrate or chemical protectant, and also possessed energy-efficient sodium pumps. Atribacteria single-cell amplified genomes (SAGs) recruited transcripts for full pathways for the production of all 20 canonical amino acids, and the gene for amino acid exporter YddG was one of their most highly transcribed genes, suggesting that they may benefit from metabolic interdependence with other cells. Subsistence of uncultured phyla in deep subsurface sediments may occur through shared strategies of using chemical protectants for biomolecular stabilization, but also by differentiating into physiological niches and metabolic interdependencies.
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Neumann-Schaal M, Jahn D, Schmidt-Hohagen K. Metabolism the Difficile Way: The Key to the Success of the Pathogen Clostridioides difficile. Front Microbiol 2019; 10:219. [PMID: 30828322 PMCID: PMC6384274 DOI: 10.3389/fmicb.2019.00219] [Citation(s) in RCA: 80] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2018] [Accepted: 01/28/2019] [Indexed: 12/11/2022] Open
Abstract
Strains of Clostridioides difficile cause detrimental diarrheas with thousands of deaths worldwide. The infection process by the Gram-positive, strictly anaerobic gut bacterium is directly related to its unique metabolism, using multiple Stickland-type amino acid fermentation reactions coupled to Rnf complex-mediated sodium/proton gradient formation for ATP generation. Major pathways utilize phenylalanine, leucine, glycine and proline with the formation of 3-phenylproprionate, isocaproate, butyrate, 5-methylcaproate, valerate and 5-aminovalerate. In parallel a versatile sugar catabolism including pyruvate formate-lyase as a central enzyme and an incomplete tricarboxylic acid cycle to prevent unnecessary NADH formation completes the picture. However, a complex gene regulatory network that carefully mediates the continuous adaptation of this metabolism to changing environmental conditions is only partially elucidated. It involves the pleiotropic regulators CodY and SigH, the known carbon metabolism regulator CcpA, the proline regulator PrdR, the iron regulator Fur, the small regulatory RNA CsrA and potentially the NADH-responsive regulator Rex. Here, we describe the current knowledge of the metabolic principles of energy generation by C. difficile and the underlying gene regulatory scenarios.
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Affiliation(s)
- Meina Neumann-Schaal
- Leibniz Institute DSMZ, German Collection of Microorganisms and Cell Cultures, Braunschweig, Germany.,Integrated Centre of Systems Biology (BRICS), Braunschweig University of Technology, Braunschweig, Germany
| | - Dieter Jahn
- Integrated Centre of Systems Biology (BRICS), Braunschweig University of Technology, Braunschweig, Germany.,Institute of Microbiology, Braunschweig University of Technology, Braunschweig, Germany
| | - Kerstin Schmidt-Hohagen
- Integrated Centre of Systems Biology (BRICS), Braunschweig University of Technology, Braunschweig, Germany.,Department of Bioinformatics and Biochemistry, Braunschweig University of Technology, Braunschweig, Germany
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14
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Xiong W, Lo J, Chou KJ, Wu C, Magnusson L, Dong T, Maness P. Isotope-Assisted Metabolite Analysis Sheds Light on Central Carbon Metabolism of a Model Cellulolytic Bacterium Clostridium thermocellum. Front Microbiol 2018; 9:1947. [PMID: 30190711 PMCID: PMC6115520 DOI: 10.3389/fmicb.2018.01947] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Accepted: 07/31/2018] [Indexed: 01/01/2023] Open
Abstract
Cellulolytic bacteria have the potential to perform lignocellulose hydrolysis and fermentation simultaneously. The metabolic pathways of these bacteria, therefore, require more comprehensive and quantitative understanding. Using isotope tracer, gas chromatography-mass spectrometry, and metabolic flux modeling, we decipher the metabolic network of Clostridium thermocellum, a model cellulolytic bacterium which represents as an attractive platform for conversion of lignocellulose to dedicated products. We uncover that the Embden-Meyerhof-Parnas (EMP) pathway is the predominant glycolytic route whereas the Entner-Doudoroff (ED) pathway and oxidative pentose phosphate pathway are inactive. We also observe that C. thermocellum's TCA cycle is initiated by both Si- and Re-citrate synthase, and it is disconnected between 2-oxoglutarate and oxaloacetate in the oxidative direction; C. thermocellum uses a citramalate shunt to synthesize isoleucine; and both the one-carbon pathway and the malate shunt are highly active in this bacterium. To gain a quantitative understanding, we further formulate a fluxome map to quantify the metabolic fluxes through central metabolic pathways. This work represents the first global in vivo investigation of the principal carbon metabolism of C. thermocellum. Our results elucidate the unique structure of metabolic network in this cellulolytic bacterium and demonstrate the capability of isotope-assisted metabolite studies in understanding microbial metabolism of industrial interests.
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Affiliation(s)
- Wei Xiong
- National Renewable Energy Laboratory, Golden, CO, United States
| | - Jonathan Lo
- National Renewable Energy Laboratory, Golden, CO, United States
| | | | - Chao Wu
- National Renewable Energy Laboratory, Golden, CO, United States
| | | | - Tao Dong
- National Renewable Energy Laboratory, Golden, CO, United States
| | - PinChing Maness
- National Renewable Energy Laboratory, Golden, CO, United States
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15
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Noda-Garcia L, Liebermeister W, Tawfik DS. Metabolite–Enzyme Coevolution: From Single Enzymes to Metabolic Pathways and Networks. Annu Rev Biochem 2018; 87:187-216. [DOI: 10.1146/annurev-biochem-062917-012023] [Citation(s) in RCA: 75] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
How individual enzymes evolved is relatively well understood. However, individual enzymes rarely confer a physiological advantage on their own. Judging by its current state, the emergence of metabolism seemingly demanded the simultaneous emergence of many enzymes. Indeed, how multicomponent interlocked systems, like metabolic pathways, evolved is largely an open question. This complexity can be unlocked if we assume that survival of the fittest applies not only to genes and enzymes but also to the metabolites they produce. This review develops our current knowledge of enzyme evolution into a wider hypothesis of pathway and network evolution. We describe the current models for pathway evolution and offer an integrative metabolite–enzyme coevolution hypothesis. Our hypothesis addresses the origins of new metabolites and of new enzymes and the order of their recruitment. We aim to not only survey established knowledge but also present open questions and potential ways of addressing them.
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Affiliation(s)
- Lianet Noda-Garcia
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot 76100, Israel;,
| | - Wolfram Liebermeister
- INRA, Unité MaIAGE, 78352 Jouy en Josas, France
- Institute of Biochemistry, Charité Universitätsmedizin, Berlin, 10117 Berlin, Germany
| | - Dan S. Tawfik
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot 76100, Israel;,
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16
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Yoshida A, Kosono S, Nishiyama M. Characterization of two 2-isopropylmalate synthase homologs from Thermus thermophilus HB27. Biochem Biophys Res Commun 2018; 501:465-470. [DOI: 10.1016/j.bbrc.2018.05.013] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Accepted: 05/02/2018] [Indexed: 10/16/2022]
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17
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Dannheim H, Riedel T, Neumann-Schaal M, Bunk B, Schober I, Spröer C, Chibani CM, Gronow S, Liesegang H, Overmann J, Schomburg D. Manual curation and reannotation of the genomes of Clostridium difficile 630Δerm and C. difficile 630. J Med Microbiol 2017; 66:286-293. [DOI: 10.1099/jmm.0.000427] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Affiliation(s)
- Henning Dannheim
- Department of Bioinformatics and Biochemistry, Technische Universität Braunschweig and Braunschweig Integrated Centre of Systems Biology (BRICS), Rebenring 56, 38106 Braunschweig, Germany
| | - Thomas Riedel
- Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures, Inhoffenstraße 7B, 38124 Braunschweig, Germany
| | - Meina Neumann-Schaal
- Department of Bioinformatics and Biochemistry, Technische Universität Braunschweig and Braunschweig Integrated Centre of Systems Biology (BRICS), Rebenring 56, 38106 Braunschweig, Germany
| | - Boyke Bunk
- Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures, Inhoffenstraße 7B, 38124 Braunschweig, Germany
- German Center for Infection Research (DZIF), Partner Site Hannover–Braunschweig, Inhoffenstraße 7B, 38124 Braunschweig, Germany
| | - Isabel Schober
- Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures, Inhoffenstraße 7B, 38124 Braunschweig, Germany
| | - Cathrin Spröer
- Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures, Inhoffenstraße 7B, 38124 Braunschweig, Germany
- German Center for Infection Research (DZIF), Partner Site Hannover–Braunschweig, Inhoffenstraße 7B, 38124 Braunschweig, Germany
| | - Cynthia Maria Chibani
- Department of Genomic and Applied Microbiology, Göttingen Genomics Laboratory, Georg-August-University Göttingen, Grisebachstraße 8, 37077 Göttingen, Germany
| | - Sabine Gronow
- Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures, Inhoffenstraße 7B, 38124 Braunschweig, Germany
- German Center for Infection Research (DZIF), Partner Site Hannover–Braunschweig, Inhoffenstraße 7B, 38124 Braunschweig, Germany
| | - Heiko Liesegang
- Department of Genomic and Applied Microbiology, Göttingen Genomics Laboratory, Georg-August-University Göttingen, Grisebachstraße 8, 37077 Göttingen, Germany
| | - Jörg Overmann
- Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures, Inhoffenstraße 7B, 38124 Braunschweig, Germany
- German Center for Infection Research (DZIF), Partner Site Hannover–Braunschweig, Inhoffenstraße 7B, 38124 Braunschweig, Germany
| | - Dietmar Schomburg
- Department of Bioinformatics and Biochemistry, Technische Universität Braunschweig and Braunschweig Integrated Centre of Systems Biology (BRICS), Rebenring 56, 38106 Braunschweig, Germany
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18
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Abstract
Organophosphonic acids are unique as natural products in terms of stability and mimicry. The C-P bond that defines these compounds resists hydrolytic cleavage, while the phosphonyl group is a versatile mimic of transition-states, intermediates, and primary metabolites. This versatility may explain why a variety of organisms have extensively explored the use organophosphonic acids as bioactive secondary metabolites. Several of these compounds, such as fosfomycin and bialaphos, figure prominently in human health and agriculture. The enzyme reactions that create these molecules are an interesting mix of chemistry that has been adopted from primary metabolism as well as those with no chemical precedent. Additionally, the phosphonate moiety represents a source of inorganic phosphate to microorganisms that live in environments that lack this nutrient; thus, unusual enzyme reactions have also evolved to cleave the C-P bond. This review is a comprehensive summary of the occurrence and function of organophosphonic acids natural products along with the mechanisms of the enzymes that synthesize and catabolize these molecules.
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Affiliation(s)
- Geoff P Horsman
- Department of Chemistry and Biochemistry, Wilfrid Laurier University , Waterloo, Ontario N2L 3C5, Canada
| | - David L Zechel
- Department of Chemistry, Queen's University , Kingston, Ontario K7L 3N6, Canada
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19
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Complete Genome Sequence of the Amino Acid-Fermenting Clostridium propionicum X2 (DSM 1682). GENOME ANNOUNCEMENTS 2016; 4:4/2/e00294-16. [PMID: 27081148 PMCID: PMC4832176 DOI: 10.1128/genomea.00294-16] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Clostridium propionicum is a strict anaerobic, Gram positive, rod-shaped bacterium that belongs to the clostridial cluster XIVb. The genome consists of one replicon (3.1 Mb) and harbors 2,936 predicted protein-encoding genes. The genome encodes all enzymes required for fermentation of the amino acids α-alanine, β-alanine, serine, threonine, and methionine.
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20
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Boll M, Kung JW, Ermler U, Martins BM, Buckel W. Fermentative Cyclohexane Carboxylate Formation in Syntrophus aciditrophicus. J Mol Microbiol Biotechnol 2016; 26:165-79. [PMID: 26959729 DOI: 10.1159/000440881] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Short-chain fatty acids such as acetic, propionic, butyric or lactic acids are typical primary fermentation products in the anaerobic feeding chain. Fifteen years ago, a novel fermentation type was discovered in the obligately anaerobic Deltaproteobacterium Syntrophus aciditrophicus. During fermentative growth with crotonate and/or benzoate, acetate is formed in the oxidative branch and cyclohexane carboxylate in the reductive branch. In both cases cyclohexa-1,5-diene-1-carboxyl-CoA (Ch1,5CoA) is a central intermediate that is either formed by a class II benzoyl-CoA reductase (fermentation of benzoate) or by reverse reactions of the benzoyl-CoA degradation pathway (fermentation of crotonate). Here, we summarize the current knowledge of the enzymology involved in fermentations yielding cyclohexane carboxylate as an excreted product. The characteristic enzymes involved are two acyl-CoA dehydrogenases specifically acting on Ch1,5CoA and cyclohex-1-ene-1-carboxyl-CoA. Both enzymes are also employed during the syntrophic growth of S. aciditrophicus with cyclohexane carboxylate as the carbon source in coculture with a methanogen. An investigation of anabolic pathways in S. aciditrophicus revealed a rather unusual pathway for glutamate synthesis involving a Re-citrate synthase. Future work has to address the unresolved question concerning which components are involved in reoxidation of the NADH formed in the oxidative branch of the unique cyclohexane carboxylate fermentation pathway in S. aciditrophicus.
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Affiliation(s)
- Matthias Boll
- Mikrobiologie, Fakultx00E4;t fx00FC;r Biologie, Albert-Ludwigs-Universitx00E4;t Freiburg, Freiburg, Germany
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21
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Davidova IA, Wawrik B, Callaghan AV, Duncan K, Marks CR, Suflita JM. Dethiosulfatarculus sandiegensis gen. nov., sp. nov., isolated from a methanogenic paraffin-degrading enrichment culture and emended description of the family Desulfarculaceae. Int J Syst Evol Microbiol 2015; 66:1242-1248. [PMID: 26704417 DOI: 10.1099/ijsem.0.000864] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A mesophilic deltaproteobacterium, designated strain SPRT, was isolated from a methanogenic consortium capable of degrading long-chain paraffins. Cells were motile, vibrio-shaped, and occurred singly, in pairs or in clusters. Strain SPRT did not metabolize hydrocarbons but grew fermentatively on pyruvate and oxaloacetate and autotrophically with H2 and CO2. Thiosulfate served as a terminal electron acceptor, but sulfate or sulfite did not. The organism required at least 10 g NaCl l- 1 and a small amount of yeast extract (0.001%) for growth. Optimal growth was observed between 30 and 37 °C and a pH range from 6.0 to 7.2. The DNA G+C content of SPRT's genome was 52.02 mol%. Based on 16S rRNA gene sequence analysis, strain SPRT was distinct from previously described Deltaproteobacteria, exhibiting the closest affiliation to Desulfarculus baarsii DSM 2075T and Desulfocarbo indianensis SCBMT, with only 91% similarity between their respective 16S gene sequences. In silico genome comparison supported the distinctiveness between strain SPRT and both Desulfocarbo indianensis SCBMT and Desulfarculus baarsii DSM 2075T. Based on physiological differences, as well as phylogenetic and genomic comparisons, we propose to classify SPRT as the type strain ( = DSM 100305T = JCM 30857T) of a novel species of a new genus with the name Dethiosulfatarculus sandiegensis gen. nov., sp. nov.
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Affiliation(s)
- Irene A Davidova
- Department of Microbiology and Plant Biology, University of Oklahoma, George Lynn Cross Hall, 770 Van Vleet Oval, Norman, OK 73019, USA.,Institute for Energy and the Environment, The University of Oklahoma, 100 East Boyd Street, Room 1510, Norman, OK 73019-1015, USA
| | - Boris Wawrik
- Department of Microbiology and Plant Biology, University of Oklahoma, George Lynn Cross Hall, 770 Van Vleet Oval, Norman, OK 73019, USA
| | - Amy V Callaghan
- Department of Microbiology and Plant Biology, University of Oklahoma, George Lynn Cross Hall, 770 Van Vleet Oval, Norman, OK 73019, USA
| | - Kathleen Duncan
- Department of Microbiology and Plant Biology, University of Oklahoma, George Lynn Cross Hall, 770 Van Vleet Oval, Norman, OK 73019, USA.,Institute for Energy and the Environment, The University of Oklahoma, 100 East Boyd Street, Room 1510, Norman, OK 73019-1015, USA
| | - Christopher R Marks
- Department of Microbiology and Plant Biology, University of Oklahoma, George Lynn Cross Hall, 770 Van Vleet Oval, Norman, OK 73019, USA.,Institute for Energy and the Environment, The University of Oklahoma, 100 East Boyd Street, Room 1510, Norman, OK 73019-1015, USA
| | - Joseph M Suflita
- Department of Microbiology and Plant Biology, University of Oklahoma, George Lynn Cross Hall, 770 Van Vleet Oval, Norman, OK 73019, USA.,Institute for Energy and the Environment, The University of Oklahoma, 100 East Boyd Street, Room 1510, Norman, OK 73019-1015, USA
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22
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Two pathways for glutamate biosynthesis in the syntrophic bacterium Syntrophus aciditrophicus. Appl Environ Microbiol 2015; 81:8434-44. [PMID: 26431966 DOI: 10.1128/aem.02323-15] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2015] [Accepted: 09/27/2015] [Indexed: 01/18/2023] Open
Abstract
The anaerobic metabolism of crotonate, benzoate, and cyclohexane carboxylate by Syntrophus aciditrophicus grown syntrophically with Methanospirillum hungatei provides a model to study syntrophic cooperation. Recent studies revealed that S. aciditrophicus contains Re-citrate synthase but lacks the common Si-citrate synthase. To establish whether the Re-citrate synthase is involved in glutamate synthesis via the oxidative branch of the Krebs cycle, we have used [1-(13)C]acetate and [1-(14)C]acetate as well as [(13)C]bicarbonate as additional carbon sources during axenic growth of S. aciditrophicus on crotonate. Our analyses showed that labeled carbons were detected in at least 14 amino acids, indicating the global utilization of acetate and bicarbonate. The labeling patterns of alanine and aspartate verified that pyruvate and oxaloacetate were synthesized by consecutive carboxylations of acetyl coenzyme A (acetyl-CoA). The isotopomer profile and (13)C nuclear magnetic resonance (NMR) spectroscopy of the obtained [(13)C]glutamate, as well as decarboxylation of [(14)C]glutamate, revealed that this amino acid was synthesized by two pathways. Unexpectedly, only the minor route used Re-citrate synthase (30 to 40%), whereas the majority of glutamate was synthesized via the reductive carboxylation of succinate. This symmetrical intermediate could have been formed from two acetates via hydration of crotonyl-CoA to 4-hydroxybutyryl-CoA. 4-Hydroxybutyrate was detected in the medium of S. aciditrophicus when grown on crotonate, but an active hydratase could not be measured in cell extracts, and the annotated 4-hydroxybutyryl-CoA dehydratase (SYN_02445) lacks key amino acids needed to catalyze the hydration of crotonyl-CoA. Besides Clostridium kluyveri, this study reveals the second example of a microbial species to employ two pathways for glutamate synthesis.
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The Complete Genome Sequence of Clostridium aceticum: a Missing Link between Rnf- and Cytochrome-Containing Autotrophic Acetogens. mBio 2015; 6:e01168-15. [PMID: 26350967 PMCID: PMC4600107 DOI: 10.1128/mbio.01168-15] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Clostridium aceticum was the first isolated autotrophic acetogen, converting CO2 plus H2 or syngas to acetate. Its genome has now been completely sequenced and consists of a 4.2-Mbp chromosome and a small circular plasmid of 5.7 kbp. Sequence analysis revealed major differences from other autotrophic acetogens. C. aceticum contains an Rnf complex for energy conservation (via pumping protons or sodium ions). Such systems have also been found in C. ljungdahlii and Acetobacterium woodii. However, C. aceticum also contains a cytochrome, as does Moorella thermoacetica, which has been proposed to be involved in the generation of a proton gradient. Thus, C. aceticum seems to represent a link between Rnf- and cytochrome-containing autotrophic acetogens. In C. aceticum, however, the cytochrome is probably not involved in an electron transport chain that leads to proton translocation, as no genes for quinone biosynthesis are present in the genome. Autotrophic acetogenic bacteria are receiving more and more industrial focus, as CO2 plus H2 as well as syngas are interesting new substrates for biotechnological processes. They are both cheap and abundant, and their use, if it results in sustainable products, also leads to reduction of greenhouse gases. Clostridium aceticum can use both gas mixtures, is phylogenetically not closely related to the commonly used species, and may thus become an even more attractive workhorse. In addition, its energy metabolism, which is characterized here, and the ability to synthesize cytochromes might offer new targets for improving the ATP yield by metabolic engineering and thus allow use of C. aceticum for production of compounds by pathways that currently present challenges for energy-limited acetogens.
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Lyu Z, Lu Y. Comparative genomics of three Methanocellales strains reveal novel taxonomic and metabolic features. ENVIRONMENTAL MICROBIOLOGY REPORTS 2015; 7:526-537. [PMID: 25727385 DOI: 10.1111/1758-2229.12283] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2014] [Accepted: 02/22/2015] [Indexed: 06/04/2023]
Abstract
Methanocellales represents a new order of methanogens, which is widespread in environments and plays specifically the important role in methane emissions from paddy fields. To gain more insights into Methanocellales, comparative genomic studies were performed among three Methanocellales strains through the same annotation pipeline. Genetic relationships among strains revealed by genome alignment, pan-genome reconstruction and comparison of amino average identity suggest that they should be classified in different genera. In addition, multiple copies of cell cycle regulator proteins were identified for the first time in Archaea. Core metabolisms were reconstructed, predicting certain unique and novel features for Methanocellales, including a set of methanogenesis genes potentially organized toward specialization in utilizing low concentrations of H2, a new route of disulfide reduction catalysed by a disulfide-reducing hydrogenase (Drh) complex phylogenetically related to sulfate-reducing prokaryotes, an oxidative tricarboxylic acid (TCA) cycle, a sophisticated nitrogen uptake and regulation system as well as a versatile sulfur utilization system. These core metabolisms are largely conserved among the three strains, but differences in gene copy number and metabolic diversity are evident. The present study thus adds new dimensions to the unique ecophysiology of Methanocellales and offers a road map for further experimental characterization of this methanogen lineage.
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Affiliation(s)
- Zhe Lyu
- College of Resources and Environmental Sciences, China Agricultural University, Beijing, 100193, China
| | - Yahai Lu
- College of Resources and Environmental Sciences, China Agricultural University, Beijing, 100193, China
- College of Urban and Environmental Sciences, Peking University, Beijing, 100871, China
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25
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Frey J, Falquet L. Patho-genetics of Clostridium chauvoei. Res Microbiol 2014; 166:384-92. [PMID: 25445013 DOI: 10.1016/j.resmic.2014.10.013] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2014] [Revised: 10/24/2014] [Accepted: 10/26/2014] [Indexed: 11/30/2022]
Abstract
The genomic sequence of Clostridium chauvoei, the etiological agent of blackleg, a severe disease of ruminants with high mortality specified by a myonecrosis reveals a chromosome of 2.8 million base-pairs and a cryptic plasmid of 5.5 kilo base-pairs. The chromosome contains the main pathways like glycolysis/gluconeogenesis, sugar metabolism, purine and pyrimidine metabolisms, but the notable absence of genes of the citric acid cycle and deficient or partially deficient amino acid metabolism for Histidine, Tyrosine, Phenylalanine, and Tryptophan. These essential amino acids might be acquired from host tissue damage caused by various toxins and by protein metabolism that includes 57 genes for peptidases, and several ABC transporters for amino acids import.
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Affiliation(s)
- Joachim Frey
- Institute of Veterinary Bacteriology, University of Bern, Länggasstrasse 122, 3001 Bern, Switzerland.
| | - Laurent Falquet
- Biochemistry Unit, Dept. of Biology, University of Fribourg and Swiss Institute of Bioinformatics, Fribourg, Switzerland
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26
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Casey AK, Hicks MA, Johnson JL, Babbitt PC, Frantom PA. Mechanistic and bioinformatic investigation of a conserved active site helix in α-isopropylmalate synthase from Mycobacterium tuberculosis, a member of the DRE-TIM metallolyase superfamily. Biochemistry 2014; 53:2915-25. [PMID: 24720347 PMCID: PMC4025573 DOI: 10.1021/bi500246z] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The characterization of functionally diverse enzyme superfamilies provides the opportunity to identify evolutionarily conserved catalytic strategies, as well as amino acid substitutions responsible for the evolution of new functions or specificities. Isopropylmalate synthase (IPMS) belongs to the DRE-TIM metallolyase superfamily. Members of this superfamily share common active site elements, including a conserved active site helix and an HXH divalent metal binding motif, associated with stabilization of a common enolate anion intermediate. These common elements are overlaid by variations in active site architecture resulting in the evolution of a diverse set of reactions that include condensation, lyase/aldolase, and carboxyl transfer activities. Here, using IPMS, an integrated biochemical and bioinformatics approach has been utilized to investigate the catalytic role of residues on an active site helix that is conserved across the superfamily. The construction of a sequence similarity network for the DRE-TIM metallolyase superfamily allows for the biochemical results obtained with IPMS variants to be compared across superfamily members and within other condensation-catalyzing enzymes related to IPMS. A comparison of our results with previous biochemical data indicates an active site arginine residue (R80 in IPMS) is strictly required for activity across the superfamily, suggesting that it plays a key role in catalysis, most likely through enolate stabilization. In contrast, differential results obtained from substitution of the C-terminal residue of the helix (Q84 in IPMS) suggest that this residue plays a role in reaction specificity within the superfamily.
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Affiliation(s)
- Ashley K Casey
- Department of Chemistry, The University of Alabama , 250 Hackberry Lane, Tuscaloosa, Alabama 35406, United States
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27
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Modifying the determinants of α-ketoacid substrate selectivity inmycobacterium tuberculosisα-isopropylmalate synthase. FEBS Lett 2014; 588:1603-7. [DOI: 10.1016/j.febslet.2014.02.053] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2014] [Revised: 02/22/2014] [Accepted: 02/24/2014] [Indexed: 11/21/2022]
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28
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Energy Conservation in Heliobacteria: Photosynthesis and Central Carbon Metabolism. THE STRUCTURAL BASIS OF BIOLOGICAL ENERGY GENERATION 2014. [DOI: 10.1007/978-94-017-8742-0_13] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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29
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Tong W, Chen Z, Cao Z, Wang Q, Zhang J, Bai X, Wang R, Liu S. Robustness analysis of a constraint-based metabolic model links cell growth and proteomics of Thermoanaerobacter tengcongensis under temperature perturbation. MOLECULAR BIOSYSTEMS 2013; 9:713-22. [PMID: 23396507 DOI: 10.1039/c3mb25278g] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The integration of omic data with metabolic networks has been demonstrated to be an effective approach to elucidate the underlying metabolic mechanisms in life. Because the metabolic pathways of Thermoanaerobacter tengcongensis (T. tengcongensis) are incomplete, we used a 1-(13)C-glucose culture to monitor intracellular isotope-labeled metabolites by GC/MS and identified the gap gene in glucose catabolism, Re-citrate synthase. Based on genome annotation and biochemical information, we reconstructed the metabolic network of glucose metabolism and amino acid synthesis in T. tengcongensis, including 253 reactions, 227 metabolites, and 236 genes. Furthermore, we performed constraint based modeling (CBM)-derived robustness analysis on the model to study the dynamic changes of the metabolic network. By perturbing the culture temperature from 75 to 55 °C, we collected the bacterial growth rates and differential proteomes. Assuming that protein abundance changes represent metabolic flux variations, we proposed that the robustness analysis of the CBM model could decipher the effect of proteome change on the bacterial growth under perturbation. For approximately 73% of the reactions, the predicted cell growth changes due to such reaction flux variations matched the observed cell growth data. Our study, therefore, indicates that differential proteome data can be integrated with metabolic network modeling and that robustness analysis is a strong method for representing the dynamic change in cell phenotypes under perturbation.
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Affiliation(s)
- Wei Tong
- Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing, 101300, China
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30
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Schipp CJ, Marco-Urrea E, Kublik A, Seifert J, Adrian L. Organic cofactors in the metabolism of Dehalococcoides mccartyi strains. Philos Trans R Soc Lond B Biol Sci 2013; 368:20120321. [PMID: 23479751 DOI: 10.1098/rstb.2012.0321] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Dehalococcoides mccartyi strains are strictly anaerobic organisms specialized to grow with halogenated compounds as electron acceptor via a respiratory process. Their genomes are among the smallest known for free-living organisms, and the embedded gene set reflects their strong specialization. Here, we briefly review main characteristics of published Dehalococcoides genomes and show how genome information together with cultivation and biochemical experiments have contributed to our understanding of Dehalococcoides physiology and biochemistry. We extend this approach by the detailed analysis of cofactor metabolism in Dehalococcoides strain CBDB1. Dehalococcoides genomes were screened for encoded proteins annotated to contain or interact with organic cofactors, and the expression of these proteins was analysed by shotgun proteomics to shed light on cofactor requirements. In parallel, cultivation experiments testing for vitamin requirements showed that cyanocobalamin (vitamin B12), thiamine and biotin were essential supplements and that cyanocobalamin could be substituted by dicyanocobinamide and dimethylbenzimidazole. Dehalococcoides genome analysis, detection of single enzymes by shotgun proteomics and inhibition studies confirmed the expression of the biosynthetic pathways for pyridoxal-5-phosphate, flavin nucleotides, folate, S-adenosylmethionine, pantothenate and nicotinic acids in strain CBDB1. Haem/cytochromes, quinones and lipoic acids were not necessary for cultivation or dechlorination activity and no biosynthetic pathways were identified in the genomes.
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Affiliation(s)
- Christian J Schipp
- Department of Isotope Biogeochemistry, Helmholtz Centre for Environmental Research-UFZ, 04318 Leipzig, Germany
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31
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Identification and characterization of re-citrate synthase in Syntrophus aciditrophicus. J Bacteriol 2013; 195:1689-96. [PMID: 23378508 DOI: 10.1128/jb.02185-12] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Glutamate is usually synthesized from acetyl coenzyme A (acetyl-CoA) via citrate, isocitrate, and 2-oxoglutarate. Genome analysis revealed that in Syntrophus aciditrophicus, the gene for Si-citrate synthase is lacking. An alternative pathway starting from the catabolic intermediate glutaconyl-CoA via 2-hydroxyglutarate could be excluded by genomic analysis. On the other hand, a putative gene (SYN_02536; NCBI gene accession no. CP000252.1) annotated as coding for isopropylmalate/citramalate/homocitrate synthase has been shown to share 49% deduced amino acid sequence identity with the gene encoding Re-citrate synthase of Clostridium kluyveri. We cloned and overexpressed this gene in Escherichia coli together with the genes encoding the chaperone GroEL. The recombinant homotetrameric enzyme with a C-terminal Strep-tag (4 × 72,892 Da) was separated from GroEL on a Strep-Tactin column by incubation with ATP, K(+), and Mg(2+). The pure Re-citrate synthase used only acetyl-CoA and oxaloacetate as the substrates. As isolated, the enzyme contained stoichiometric amounts of Ca(2+) (0.9 Ca/73 kDa) but achieved higher specific activities in the presence of Mn(2+) (1.2 U/mg) or Co(2+) (2.0 U/mg). To determine the stereospecificity of the enzyme, [(14)C]citrate was enzymatically synthesized from oxaloacetate and [1-(14)C]acetyl-CoA; the subsequent cleavage by Si-citrate lyase yielded unlabeled acetate and labeled oxaloacetate, demonstrating that the enzyme is a Re-citrate synthase. The production of Re-citrate synthase by S. aciditrophicus grown axenically on crotonate was revealed by synthesis of [(14)C]citrate in a cell extract followed by stereochemical analysis. This result was supported by detection of transcripts of the Re-citrate synthase gene in axenic as well as in syntrophic cultures using quantitative reverse transcriptase PCR (qRT-PCR).
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32
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Tang JKH, You L, Blankenship RE, Tang YJ. Recent advances in mapping environmental microbial metabolisms through 13C isotopic fingerprints. J R Soc Interface 2012; 9:2767-80. [PMID: 22896564 DOI: 10.1098/rsif.2012.0396] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
After feeding microbes with a defined (13)C substrate, unique isotopic patterns (isotopic fingerprints) can be formed in their metabolic products. Such labelling information not only can provide novel insights into functional pathways but also can determine absolute carbon fluxes through the metabolic network via metabolic modelling approaches. This technique has been used for finding pathways that may have been mis-annotated in the past, elucidating new enzyme functions, and investigating cell metabolisms in microbial communities. In this review paper, we summarize the applications of (13)C approaches to analyse novel cell metabolisms for the past 3 years. The isotopic fingerprints (defined as unique isotopomers useful for pathway identifications) have revealed the operations of the Entner-Doudoroff pathway, the reverse tricarboxylic acid cycle, new enzymes for biosynthesis of central metabolites, diverse respiration routes in phototrophic metabolism, co-metabolism of carbon nutrients and novel CO(2) fixation pathways. This review also discusses new isotopic methods to map carbon fluxes in global metabolisms, as well as potential factors influencing the metabolic flux quantification (e.g. metabolite channelling, the isotopic purity of (13)C substrates and the isotopic effect). Although (13)C labelling is not applicable to all biological systems (e.g. microbial communities), recent studies have shown that this method has a significant value in functional characterization of poorly understood micro-organisms, including species relevant for biotechnology and human health.
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Affiliation(s)
- Joseph Kuo-Hsiang Tang
- Carlson School of Chemistry and Biochemistry, Clark University, 950 Main Street, Worcester, MA 01610, USA
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Marco-Urrea E, Paul S, Khodaverdi V, Seifert J, von Bergen M, Kretzschmar U, Adrian L. Identification and characterization of a re-citrate synthase in Dehalococcoides strain CBDB1. J Bacteriol 2011; 193:5171-8. [PMID: 21784924 PMCID: PMC3187404 DOI: 10.1128/jb.05120-11] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2011] [Accepted: 07/17/2011] [Indexed: 01/12/2023] Open
Abstract
The genome annotations of all sequenced Dehalococcoides strains lack a citrate synthase, although physiological experiments have indicated that such an activity should be encoded. We here report that a Re face-specific citrate synthase is synthesized by Dehalococcoides strain CBDB1 and that this function is encoded by the gene cbdbA1708 (NCBI accession number CAI83711), previously annotated as encoding homocitrate synthase. Gene cbdbA1708 was heterologously expressed in Escherichia coli, and the recombinant enzyme was purified. The enzyme catalyzed the condensation of oxaloacetate and acetyl coenzyme A (acetyl-CoA) to citrate. The protein did not have homocitrate synthase activity and was inhibited by citrate, and Mn2+ was needed for full activity. The stereospecificity of the heterologously expressed citrate synthase was determined by electrospray ionization liquid chromatography-mass spectrometry (ESI LC/MS). Citrate was synthesized from [2-(13)C]acetyl-CoA and oxaloacetate by the Dehalococcoides recombinant citrate synthase and then converted to acetate and malate by commercial citrate lyase plus malate dehydrogenase. The formation of unlabeled acetate and 13C-labeled malate proved the Re face-specific activity of the enzyme. Shotgun proteome analyses of cell extracts of strain CBDB1 demonstrated that cbdbA1708 is expressed in strain CBDB1.
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Affiliation(s)
- Ernest Marco-Urrea
- Helmholtz Centre for Environmental Research—UFZ, Department of Isotope Biogeochemistry, Leipzig, Germany
- Department of Chemical Engineering, Autonomous University of Barcelona, Bellaterra 08193, Spain
| | - Steffanie Paul
- Technische Universität Berlin, FG Angewandte Biochemie, Berlin, Germany
| | - Viola Khodaverdi
- Technische Universität Berlin, FG Angewandte Biochemie, Berlin, Germany
| | - Jana Seifert
- Helmholtz Centre for Environmental Research—UFZ, Department of Proteomics, Leipzig, Germany
| | - Martin von Bergen
- Helmholtz Centre for Environmental Research—UFZ, Department of Proteomics, Leipzig, Germany
| | - Utta Kretzschmar
- Technische Universität Berlin, FG Angewandte Biochemie, Berlin, Germany
| | - Lorenz Adrian
- Helmholtz Centre for Environmental Research—UFZ, Department of Isotope Biogeochemistry, Leipzig, Germany
- Technische Universität Berlin, FG Angewandte Biochemie, Berlin, Germany
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34
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Tang KH, Tang YJ, Blankenship RE. Carbon metabolic pathways in phototrophic bacteria and their broader evolutionary implications. Front Microbiol 2011; 2:165. [PMID: 21866228 PMCID: PMC3149686 DOI: 10.3389/fmicb.2011.00165] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2011] [Accepted: 07/18/2011] [Indexed: 11/19/2022] Open
Abstract
Photosynthesis is the biological process that converts solar energy to biomass, bio-products, and biofuel. It is the only major natural solar energy storage mechanism on Earth. To satisfy the increased demand for sustainable energy sources and identify the mechanism of photosynthetic carbon assimilation, which is one of the bottlenecks in photosynthesis, it is essential to understand the process of solar energy storage and associated carbon metabolism in photosynthetic organisms. Researchers have employed physiological studies, microbiological chemistry, enzyme assays, genome sequencing, transcriptomics, and (13)C-based metabolomics/fluxomics to investigate central carbon metabolism and enzymes that operate in phototrophs. In this report, we review diverse CO(2) assimilation pathways, acetate assimilation, carbohydrate catabolism, the tricarboxylic acid cycle and some key, and/or unconventional enzymes in central carbon metabolism of phototrophic microorganisms. We also discuss the reducing equivalent flow during photoautotrophic and photoheterotrophic growth, evolutionary links in the central carbon metabolic network, and correlations between photosynthetic and non-photosynthetic organisms. Considering the metabolic versatility in these fascinating and diverse photosynthetic bacteria, many essential questions in their central carbon metabolism still remain to be addressed.
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Affiliation(s)
- Kuo-Hsiang Tang
- Department of Biology, Washington University in St. LouisSt. Louis, MO, USA
- Department of Chemistry, Washington University in St. LouisSt. Louis, MO, USA
| | - Yinjie J. Tang
- Department of Energy, Environment, and Chemical Engineering, Washington University in St. LouisSt. Louis, MO, USA
| | - Robert Eugene Blankenship
- Department of Biology, Washington University in St. LouisSt. Louis, MO, USA
- Department of Chemistry, Washington University in St. LouisSt. Louis, MO, USA
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35
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More than 200 genes required for methane formation from H₂ and CO₂ and energy conservation are present in Methanothermobacter marburgensis and Methanothermobacter thermautotrophicus. ARCHAEA-AN INTERNATIONAL MICROBIOLOGICAL JOURNAL 2011; 2011:973848. [PMID: 21559116 PMCID: PMC3087415 DOI: 10.1155/2011/973848] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/24/2010] [Revised: 12/07/2010] [Accepted: 02/18/2011] [Indexed: 12/19/2022]
Abstract
The hydrogenotrophic methanogens Methanothermobacter marburgensis and Methanothermobacter thermautotrophicus can easily be mass cultured. They have therefore been used almost exclusively to study the biochemistry of methanogenesis from H2 and CO2, and the genomes of these two model organisms have been sequenced. The close relationship of the two organisms is reflected in their genomic architecture and coding potential. Within the 1,607 protein coding sequences (CDS) in common, we identified approximately 200 CDS required for the synthesis of the enzymes, coenzymes, and prosthetic groups involved in CO2 reduction to methane and in coupling this process with the phosphorylation of ADP. Approximately 20 additional genes, such as those for the biosynthesis of F430 and methanofuran and for the posttranslational modifications of the two methyl-coenzyme M reductases, remain to be identified.
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36
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37
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Crown SB, Indurthi DC, Ahn WS, Choi J, Papoutsakis ET, Antoniewicz MR. Resolving the TCA cycle and pentose-phosphate pathway of Clostridium acetobutylicum ATCC 824: Isotopomer analysis, in vitro activities and expression analysis. Biotechnol J 2010; 6:300-5. [PMID: 21370473 DOI: 10.1002/biot.201000282] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2010] [Revised: 09/12/2010] [Accepted: 09/15/2010] [Indexed: 12/18/2022]
Abstract
Solventogenic clostridia are an important class of microorganisms that can produce various biofuels. One of the bottlenecks in engineering clostridia stems from the fact that central metabolic pathways remain poorly understood. Here, we utilized the power of (13) C-based isotopomer analysis to re-examine central metabolic pathways of Clostridium acetobutylicum ATCC 824. We demonstrate using [1,2-(13) C]glucose, MS analysis of intracellular metabolites, and enzymatic assays that C. acetobutylicum has a split TCA cycle where only Re-citrate synthase (CS) contributes to the production of α-ketoglutarate via citrate. Furthermore, we show that there is no carbon exchange between α-ketoglutarate and fumarate and that the oxidative pentose-phosphate pathway (oxPPP) is inactive. Dynamic gene expression analysis of the putative Re-CS gene (CAC0970), its operon, and all glycolysis, pentose-phosphate pathway, and TCA cycle genes identify genes and their degree of involvement in these core pathways that support the powerful primary metabolism of this industrial organism.
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Affiliation(s)
- Scott B Crown
- Department of Chemical Engineering, Metabolic Engineering and Systems Biology Laboratory, Delaware Biotechnology Institute, University of Delaware, Newark, DE, USA
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38
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Tang KH, Feng X, Zhuang WQ, Alvarez-Cohen L, Blankenship RE, Tang YJ. Carbon flow of heliobacteria is related more to clostridia than to the green sulfur bacteria. J Biol Chem 2010; 285:35104-12. [PMID: 20807773 DOI: 10.1074/jbc.m110.163303] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The recently discovered heliobacteria are the only Gram-positive photosynthetic bacteria that have been cultured. One of the unique features of heliobacteria is that they have properties of both the photosynthetic green sulfur bacteria (containing the type I reaction center) and Clostridia (forming heat-resistant endospores). Most of the previous studies of heliobacteria, which are strict anaerobes and have the simplest known photosynthetic apparatus, have focused on energy and electron transfer processes. It has been assumed that like green sulfur bacteria, the major carbon flow in heliobacteria is through the (incomplete) reductive (reverse) tricarboxylic acid cycle, whereas the lack of CO(2)-enhanced growth has not been understood. Here, we report studies to fill the knowledge gap of heliobacterial carbon metabolism. We confirm that the CO(2)-anaplerotic pathway is active during phototrophic growth and that isoleucine is mainly synthesized from the citramalate pathway. Furthermore, to our surprise, our results suggest that the oxidative (forward) TCA cycle is operative and more active than the previously reported reductive (reverse) tricarboxylic acid cycle. Both isotopomer analysis and activity assays suggest that citrate is produced by a putative (Re)-citrate synthase and then enters the oxidative (forward) TCA cycle. Moreover, in contrast to (Si)-citrate synthase, (Re)-citrate synthase produces a different isomer of 2-fluorocitrate that is not expected to inhibit the activity of aconitase.
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Affiliation(s)
- Kuo-Hsiang Tang
- Department of Biology, Washington University, St. Louis, Missouri 63130, USA
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39
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Characterizing the metabolism of Dehalococcoides with a constraint-based model. PLoS Comput Biol 2010; 6. [PMID: 20811585 PMCID: PMC2930330 DOI: 10.1371/journal.pcbi.1000887] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2010] [Accepted: 07/15/2010] [Indexed: 01/26/2023] Open
Abstract
Dehalococcoides strains respire a wide variety of chloro-organic compounds and are important for the bioremediation of toxic, persistent, carcinogenic, and ubiquitous ground water pollutants. In order to better understand metabolism and optimize their application, we have developed a pan-genome-scale metabolic network and constraint-based metabolic model of Dehalococcoides. The pan-genome was constructed from publicly available complete genome sequences of Dehalococcoides sp. strain CBDB1, strain 195, strain BAV1, and strain VS. We found that Dehalococcoides pan-genome consisted of 1118 core genes (shared by all), 457 dispensable genes (shared by some), and 486 unique genes (found in only one genome). The model included 549 metabolic genes that encoded 356 proteins catalyzing 497 gene-associated model reactions. Of these 497 reactions, 477 were associated with core metabolic genes, 18 with dispensable genes, and 2 with unique genes. This study, in addition to analyzing the metabolism of an environmentally important phylogenetic group on a pan-genome scale, provides valuable insights into Dehalococcoides metabolic limitations, low growth yields, and energy conservation. The model also provides a framework to anchor and compare disparate experimental data, as well as to give insights on the physiological impact of "incomplete" pathways, such as the TCA-cycle, CO(2) fixation, and cobalamin biosynthesis pathways. The model, referred to as iAI549, highlights the specialized and highly conserved nature of Dehalococcoides metabolism, and suggests that evolution of Dehalococcoides species is driven by the electron acceptor availability.
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40
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Systems-level metabolic flux profiling elucidates a complete, bifurcated tricarboxylic acid cycle in Clostridium acetobutylicum. J Bacteriol 2010; 192:4452-61. [PMID: 20622067 DOI: 10.1128/jb.00490-10] [Citation(s) in RCA: 111] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Obligatory anaerobic bacteria are major contributors to the overall metabolism of soil and the human gut. The metabolic pathways of these bacteria remain, however, poorly understood. Using isotope tracers, mass spectrometry, and quantitative flux modeling, here we directly map the metabolic pathways of Clostridium acetobutylicum, a soil bacterium whose major fermentation products include the biofuels butanol and hydrogen. While genome annotation suggests the absence of most tricarboxylic acid (TCA) cycle enzymes, our results demonstrate that this bacterium has a complete, albeit bifurcated, TCA cycle; oxaloacetate flows to succinate both through citrate/alpha-ketoglutarate and via malate/fumarate. Our investigations also yielded insights into the pathways utilized for glucose catabolism and amino acid biosynthesis and revealed that the organism's one-carbon metabolism is distinct from that of model microbes, involving reversible pyruvate decarboxylation and the use of pyruvate as the one-carbon donor for biosynthetic reactions. This study represents the first in vivo characterization of the TCA cycle and central metabolism of C. acetobutylicum. Our results establish a role for the full TCA cycle in an obligatory anaerobic organism and demonstrate the importance of complementing genome annotation with isotope tracer studies for determining the metabolic pathways of diverse microbes.
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Sieber JR, Sims DR, Han C, Kim E, Lykidis A, Lapidus AL, McDonnald E, Rohlin L, Culley DE, Gunsalus R, McInerney MJ. The genome of Syntrophomonas wolfei: new insights into syntrophic metabolism and biohydrogen production. Environ Microbiol 2010; 12:2289-301. [PMID: 21966920 DOI: 10.1111/j.1462-2920.2010.02237.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Syntrophomonas wolfei is a specialist, evolutionarily adapted for syntrophic growth with methanogens and other hydrogen- and/or formate-using microorganisms. This slow-growing anaerobe has three putative ribosome RNA operons, each of which has 16S rRNA and 23S rRNA genes of different length and multiple 5S rRNA genes. The genome also contains 10 RNA-directed, DNA polymerase genes. Genomic analysis shows that S. wolfei relies solely on the reduction of protons, bicarbonate or unsaturated fatty acids to re-oxidize reduced cofactors. Syntrophomonas wolfei lacks the genes needed for aerobic or anaerobic respiration and has an exceptionally limited ability to create ion gradients. An ATP synthase and a pyrophosphatase were the only systems detected capable of creating an ion gradient. Multiple homologues for β-oxidation genes were present even though S. wolfei uses a limited range of fatty acids from four to eight carbons in length.Syntrophomonas wolfei, other syntrophic metabolizers with completed genomic sequences, and thermophilic anaerobes known to produce high molar ratios of hydrogen from glucose have genes to produce H(2) from NADH by an electron bifurcation mechanism. Comparative genomic analysis also suggests that formate production from NADH may involve electron bifurcation. A membrane-bound, iron-sulfur oxidoreductase found in S. wolfei and Syntrophus aciditrophicus may be uniquely involved in reverse electron transport during syntrophic fatty acid metabolism. The genome sequence of S. wolfei reveals several core reactions that may be characteristic of syntrophic fatty acid metabolism and illustrates how biological systems produce hydrogen from thermodynamically difficult reactions.
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Affiliation(s)
- Jessica R Sieber
- Department of Botany and Microbiology, University of Oklahoma, Norman, OK 73019, USA
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42
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Tang YJ, Martin HG, Deutschbauer A, Feng X, Huang R, Llora X, Arkin A, Keasling JD. Invariability of central metabolic flux distribution in Shewanella oneidensis MR-1 under environmental or genetic perturbations. Biotechnol Prog 2010; 25:1254-9. [PMID: 19610125 DOI: 10.1002/btpr.227] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
An environmentally important bacterium with versatile respiration, Shewanella oneidensis MR-1, displayed significantly different growth rates under three culture conditions: minimal medium (doubling time approximately 3 h), salt stressed minimal medium (doubling time approximately 6 h), and minimal medium with amino acid supplementation (doubling time approximately 1.5 h). (13)C-based metabolic flux analysis indicated that fluxes of central metabolic reactions remained relatively constant under the three growth conditions, which is in stark contrast to the reported significant changes in the transcript and metabolite profiles under various growth conditions. Furthermore, 10 transposon mutants of S. oneidensis MR-1 were randomly chosen from a transposon library and their flux distributions through central metabolic pathways were revealed to be identical, even though such mutational processes altered the secondary metabolism, for example, glycine and C1 (5,10-Me-THF) metabolism.
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Affiliation(s)
- Yinjie J Tang
- Dept. of Energy, Washington University, St. Louis, MO 63130, USA
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43
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Huisman FH, Hunter MF, Devenish SR, Gerrard JA, Parker EJ. The C-terminal regulatory domain is required for catalysis by Neisseria meningitidis α-isopropylmalate synthase. Biochem Biophys Res Commun 2010; 393:168-73. [DOI: 10.1016/j.bbrc.2010.01.114] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2010] [Accepted: 01/27/2010] [Indexed: 11/28/2022]
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44
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Characterization of the central metabolic pathways in Thermoanaerobacter sp. strain X514 via isotopomer-assisted metabolite analysis. Appl Environ Microbiol 2009; 75:5001-8. [PMID: 19525270 DOI: 10.1128/aem.00715-09] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Thermoanaerobacter sp. strain X514 has great potential in biotechnology due to its capacity to ferment a range of C(5) and C(6) sugars to ethanol and other metabolites under thermophilic conditions. This study investigated the central metabolism of strain X514 via (13)C-labeled tracer experiments using either glucose or pyruvate as both carbon and energy sources. X514 grew on minimal medium and thus contains complete biosynthesis pathways for all macromolecule building blocks. Based on genome annotation and isotopic analysis of amino acids, three observations can be obtained about the central metabolic pathways in X514. First, the oxidative pentose phosphate pathway in X514 is not functional, and the tricarboxylic acid cycle is incomplete under fermentative growth conditions. Second, X514 contains (Re)-type citrate synthase activity, although no gene homologous to the recently characterized (Re)-type citrate synthase of Clostridium kluyveri was found. Third, the isoleucine in X514 is derived from acetyl coenzyme A and pyruvate via the citramalate pathway rather than being synthesized from threonine via threonine ammonia-lyase. The functionality of the citramalate synthase gene (cimA [Teth514_1204]) has been confirmed by enzymatic activity assays, while the presence of intracellular citramalate has been detected by mass spectrometry. This study demonstrates the merits of combining (13)C-assisted metabolite analysis, enzyme assays, and metabolite detection not only to examine genome sequence annotations but also to discover novel enzyme activities.
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45
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Investigation of carbon metabolism in "Dehalococcoides ethenogenes" strain 195 by use of isotopomer and transcriptomic analyses. J Bacteriol 2009; 191:5224-31. [PMID: 19525347 DOI: 10.1128/jb.00085-09] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Members of the genus "Dehalococcoides" are the only known microorganisms that can completely dechlorinate tetrachloroethene and trichloroethene to the innocuous end product, ethene. This study examines the central metabolism in "Dehalococcoides ethenogenes" strain 195 via (13)C-labeled tracer experiments. Supported by the genome annotation and the transcript profile, isotopomer analysis of key metabolites clarifies ambiguities in the genome annotation and identifies an unusual biosynthetic pathway in strain 195. First, the (13)C-labeling studies revealed that strain 195 contains complete amino acid biosynthesis pathways, even though current genome annotation suggests that several of these pathways are incomplete. Second, the tricarboxylic acid cycle of strain 195 is confirmed to be branched, and the Wood-Ljungdahl carbon fixation pathway is shown to not be functionally active under our experimental conditions; rather, CO(2) is assimilated via two reactions, conversion of acetyl-coenzyme A (acetyl coenzyme A [acetyl-CoA]) to pyruvate catalyzed by pyruvate synthase (DET0724-0727) and pyruvate conversion to oxaloacetate via pyruvate carboxylase (DET0119-0120). Third, the (13)C-labeling studies also suggested that isoleucine is synthesized from acetyl-CoA and pyruvate via citramalate synthase (CimA, EC 2.3.1.182), rather than from the common pathway via threonine ammonia-lyase (EC 4.3.1.19). Finally, evidence is presented that strain 195 may contain an undocumented citrate synthase (>95% Re-type stereospecific), i.e., a novel Re-citrate synthase that is apparently different from the one recently reported in Clostridium kluyveri.
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The genome sequence of the psychrophilic archaeon, Methanococcoides burtonii: the role of genome evolution in cold adaptation. ISME JOURNAL 2009; 3:1012-35. [DOI: 10.1038/ismej.2009.45] [Citation(s) in RCA: 130] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Genomic analysis of "Elusimicrobium minutum," the first cultivated representative of the phylum "Elusimicrobia" (formerly termite group 1). Appl Environ Microbiol 2009; 75:2841-9. [PMID: 19270133 DOI: 10.1128/aem.02698-08] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Organisms of the candidate phylum termite group 1 (TG1) are regularly encountered in termite hindguts but are present also in many other habitats. Here, we report the complete genome sequence (1.64 Mbp) of "Elusimicrobium minutum" strain Pei191(T), the first cultured representative of the TG1 phylum. We reconstructed the metabolism of this strictly anaerobic bacterium isolated from a beetle larva gut, and we discuss the findings in light of physiological data. E. minutum has all genes required for uptake and fermentation of sugars via the Embden-Meyerhof pathway, including several hydrogenases, and an unusual peptide degradation pathway comprising transamination reactions and leading to the formation of alanine, which is excreted in substantial amounts. The presence of genes encoding lipopolysaccharide biosynthesis and the presence of a pathway for peptidoglycan formation are consistent with ultrastructural evidence of a gram-negative cell envelope. Even though electron micrographs showed no cell appendages, the genome encodes many genes putatively involved in pilus assembly. We assigned some to a type II secretion system, but the function of 60 pilE-like genes remains unknown. Numerous genes with hypothetical functions, e.g., polyketide synthesis, nonribosomal peptide synthesis, antibiotic transport, and oxygen stress protection, indicate the presence of hitherto undiscovered physiological traits. Comparative analysis of 22 concatenated single-copy marker genes corroborated the status of "Elusimicrobia" (formerly TG1) as a separate phylum in the bacterial domain, which was so far based only on 16S rRNA sequence analysis.
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Drevland RM, Jia Y, Palmer DRJ, Graham DE. Methanogen homoaconitase catalyzes both hydrolyase reactions in coenzyme B biosynthesis. J Biol Chem 2008; 283:28888-96. [PMID: 18765671 PMCID: PMC2662002 DOI: 10.1074/jbc.m802159200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2008] [Revised: 08/27/2008] [Indexed: 11/06/2022] Open
Abstract
Homoaconitase enzymes catalyze hydrolyase reactions in the alpha-aminoadipate pathway for lysine biosynthesis or the 2-oxosuberate pathway for methanogenic coenzyme B biosynthesis. Despite the homology of this iron-sulfur protein to aconitase, previously studied homoaconitases catalyze only the hydration of cis-homoaconitate to form homoisocitrate rather than the complete isomerization of homocitrate to homoisocitrate. The MJ1003 and MJ1271 proteins from the methanogen Methanocaldococcus jannaschii formed the first homoaconitase shown to catalyze both the dehydration of (R)-homocitrate to form cis-homoaconitate, and its hydration is shown to produce homoisocitrate. This heterotetrameric enzyme also used the analogous longer chain substrates cis-(homo)(2)aconitate, cis-(homo)(3)aconitate, and cis-(homo)(4)aconitate, all with similar specificities. A combination of the homoaconitase with the M. jannaschii homoisocitrate dehydrogenase catalyzed all of the isomerization and oxidative decarboxylation reactions required to form 2-oxoadipate, 2-oxopimelate, and 2-oxosuberate, completing three iterations of the 2-oxoacid elongation pathway. Methanogenic archaeal homoaconitases and fungal homoaconitases evolved in parallel in the aconitase superfamily. The archaeal homoaconitases share a common ancestor with isopropylmalate isomerases, and both enzymes catalyzed the hydration of the minimal substrate maleate to form d-malate. The variation in substrate specificity among these enzymes correlated with the amino acid sequences of a flexible loop in the small subunits.
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Affiliation(s)
- Randy M Drevland
- Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, Texas 78712, USA
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A dicarboxylate/4-hydroxybutyrate autotrophic carbon assimilation cycle in the hyperthermophilic Archaeum Ignicoccus hospitalis. Proc Natl Acad Sci U S A 2008; 105:7851-6. [PMID: 18511565 DOI: 10.1073/pnas.0801043105] [Citation(s) in RCA: 189] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Ignicoccus hospitalis is an anaerobic, autotrophic, hyperthermophilic Archaeum that serves as a host for the symbiotic/parasitic Archaeum Nanoarchaeum equitans. It uses a yet unsolved autotrophic CO(2) fixation pathway that starts from acetyl-CoA (CoA), which is reductively carboxylated to pyruvate. Pyruvate is converted to phosphoenol-pyruvate (PEP), from which glucogenesis as well as oxaloacetate formation branch off. Here, we present the complete metabolic cycle by which the primary CO(2) acceptor molecule acetyl-CoA is regenerated. Oxaloacetate is reduced to succinyl-CoA by an incomplete reductive citric acid cycle lacking 2-oxoglutarate dehydrogenase or synthase. Succinyl-CoA is reduced to 4-hydroxybutyrate, which is then activated to the CoA thioester. By using the radical enzyme 4-hydroxybutyryl-CoA dehydratase, 4-hydroxybutyryl-CoA is dehydrated to crotonyl-CoA. Finally, beta-oxidation of crotonyl-CoA leads to two molecules of acetyl-CoA. Thus, the cyclic pathway forms an extra molecule of acetyl-CoA, with pyruvate synthase and PEP carboxylase as the carboxylating enzymes. The proposal is based on in vitro transformation of 4-hydroxybutyrate, detection of all enzyme activities, and in vivo-labeling experiments using [1-(14)C]4-hydroxybutyrate, [1,4-(13)C(2)], [U-(13)C(4)]succinate, or [1-(13)C]pyruvate as tracers. The pathway is termed the dicarboxylate/4-hydroxybutyrate cycle. It combines anaerobic metabolic modules to a straightforward and efficient CO(2) fixation mechanism.
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The genome of Clostridium kluyveri, a strict anaerobe with unique metabolic features. Proc Natl Acad Sci U S A 2008; 105:2128-33. [PMID: 18218779 DOI: 10.1073/pnas.0711093105] [Citation(s) in RCA: 296] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Clostridium kluyveri is unique among the clostridia; it grows anaerobically on ethanol and acetate as sole energy sources. Fermentation products are butyrate, caproate, and H2. We report here the genome sequence of C. kluyveri, which revealed new insights into the metabolic capabilities of this well studied organism. A membrane-bound energy-converting NADH:ferredoxin oxidoreductase (RnfCDGEAB) and a cytoplasmic butyryl-CoA dehydrogenase complex (Bcd/EtfAB) coupling the reduction of crotonyl-CoA to butyryl-CoA with the reduction of ferredoxin represent a new energy-conserving module in anaerobes. The genes for NAD-dependent ethanol dehydrogenase and NAD(P)-dependent acetaldehyde dehydrogenase are located next to genes for microcompartment proteins, suggesting that the two enzymes, which are isolated together in a macromolecular complex, form a carboxysome-like structure. Unique for a strict anaerobe, C. kluyveri harbors three sets of genes predicted to encode for polyketide/nonribosomal peptide synthetase hybrides and one set for a nonribosomal peptide synthetase. The latter is predicted to catalyze the synthesis of a new siderophore, which is formed under iron-deficient growth conditions.
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