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Durante-Rodríguez G, Gutiérrez-Del-Arroyo P, Vélez M, Díaz E, Carmona M. Further Insights into the Architecture of the PN Promoter That Controls the Expression of the bzd Genes in Azoarcus. Genes (Basel) 2019; 10:genes10070489. [PMID: 31252700 PMCID: PMC6678401 DOI: 10.3390/genes10070489] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2019] [Revised: 06/12/2019] [Accepted: 06/26/2019] [Indexed: 12/01/2022] Open
Abstract
The anaerobic degradation of benzoate in bacteria involves the benzoyl-CoA central pathway. Azoarcus/Aromatoleum strains are a major group of anaerobic benzoate degraders, and the transcriptional regulation of the bzd genes was extensively studied in Azoarcus sp. CIB. In this work, we show that the bzdR regulatory gene and the PN promoter can also be identified upstream of the catabolic bzd operon in all benzoate-degrader Azoarcus/Aromatoleum strains whose genome sequences are currently available. All the PN promoters from Azoarcus/Aromatoleum strains described here show a conserved architecture including three operator regions (ORs), i.e., OR1 to OR3, for binding to the BzdR transcriptional repressor. Here, we demonstrate that, whereas OR1 is sufficient for the BzdR-mediated repression of the PN promoter, the presence of OR2 and OR3 is required for de-repression promoted by the benzoyl-CoA inducer molecule. Our results reveal that BzdR binds to the PN promoter in the form of four dimers, two of them binding to OR1. The BzdR/PN complex formed induces a DNA loop that wraps around the BzdR dimers and generates a superstructure that was observed by atomic force microscopy. This work provides further insights into the existence of a conserved BzdR-dependent mechanism to control the expression of the bzd genes in Azoarcus strains.
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Affiliation(s)
- Gonzalo Durante-Rodríguez
- Microbial and Plant Biotechnology Department. Centro de Investigaciones Biológicas-CSIC. Ramiro de Maeztu, 9. 28040 Madrid, Spain
| | - Paloma Gutiérrez-Del-Arroyo
- Biocatalysis Department. Institute of Catalysis and Petrochemistry-CSIC. Marie Curie, 2, Cantoblanco. 28049 Madrid, Spain
| | - Marisela Vélez
- Biocatalysis Department. Institute of Catalysis and Petrochemistry-CSIC. Marie Curie, 2, Cantoblanco. 28049 Madrid, Spain
| | - Eduardo Díaz
- Microbial and Plant Biotechnology Department. Centro de Investigaciones Biológicas-CSIC. Ramiro de Maeztu, 9. 28040 Madrid, Spain
| | - Manuel Carmona
- Microbial and Plant Biotechnology Department. Centro de Investigaciones Biológicas-CSIC. Ramiro de Maeztu, 9. 28040 Madrid, Spain.
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52
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James KL, Kung JW, Crable BR, Mouttaki H, Sieber JR, Nguyen HH, Yang Y, Xie Y, Erde J, Wofford NQ, Karr EA, Loo JA, Ogorzalek Loo RR, Gunsalus RP, McInerney MJ. Syntrophus aciditrophicus uses the same enzymes in a reversible manner to degrade and synthesize aromatic and alicyclic acids. Environ Microbiol 2019; 21:1833-1846. [PMID: 30895699 PMCID: PMC6488403 DOI: 10.1111/1462-2920.14601] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Revised: 03/12/2019] [Accepted: 03/19/2019] [Indexed: 12/12/2022]
Abstract
Syntrophy is essential for the efficient conversion of organic carbon to methane in natural and constructed environments, but little is known about the enzymes involved in syntrophic carbon and electron flow. Syntrophus aciditrophicus strain SB syntrophically degrades benzoate and cyclohexane-1-carboxylate and catalyses the novel synthesis of benzoate and cyclohexane-1-carboxylate from crotonate. We used proteomic, biochemical and metabolomic approaches to determine what enzymes are used for fatty, aromatic and alicyclic acid degradation versus for benzoate and cyclohexane-1-carboxylate synthesis. Enzymes involved in the metabolism of cyclohex-1,5-diene carboxyl-CoA to acetyl-CoA were in high abundance in S. aciditrophicus cells grown in pure culture on crotonate and in coculture with Methanospirillum hungatei on crotonate, benzoate or cyclohexane-1-carboxylate. Incorporation of 13 C-atoms from 1-[13 C]-acetate into crotonate, benzoate and cyclohexane-1-carboxylate during growth on these different substrates showed that the pathways are reversible. A protein conduit for syntrophic reverse electron transfer from acyl-CoA intermediates to formate was detected. Ligases and membrane-bound pyrophosphatases make pyrophosphate needed for the synthesis of ATP by an acetyl-CoA synthetase. Syntrophus aciditrophicus, thus, uses a core set of enzymes that operates close to thermodynamic equilibrium to conserve energy in a novel and highly efficient manner.
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Affiliation(s)
- Kimberly L. James
- Department of Microbiology and Plant Biology, University of
Oklahoma, Norman, OK, 73019
| | - Johannes W. Kung
- Department of Microbiology and Plant Biology, University of
Oklahoma, Norman, OK, 73019
| | - Bryan R. Crable
- Department of Microbiology and Plant Biology, University of
Oklahoma, Norman, OK, 73019
| | - Housna Mouttaki
- Department of Microbiology and Plant Biology, University of
Oklahoma, Norman, OK, 73019
| | - Jessica R. Sieber
- Department of Microbiology and Plant Biology, University of
Oklahoma, Norman, OK, 73019
| | - Hong H. Nguyen
- Department of Chemistry & Biochemistry, University of
California, Los Angeles 90095
| | - Yanan Yang
- Department of Chemistry & Biochemistry, University of
California, Los Angeles 90095
| | - Yongming Xie
- Department of Chemistry & Biochemistry, University of
California, Los Angeles 90095
| | - Jonathan Erde
- Department of Chemistry & Biochemistry, University of
California, Los Angeles 90095
| | - Neil Q. Wofford
- Department of Microbiology and Plant Biology, University of
Oklahoma, Norman, OK, 73019
| | - Elizabeth A. Karr
- Department of Microbiology and Plant Biology, University of
Oklahoma, Norman, OK, 73019
- Price Family Foundation Institute of Structural Biology,
University of Oklahoma, Norman, OK, 73019
| | - Joseph A. Loo
- UCLA DOE Institute, University of California, Los Angeles
CA 90095
- Department of Chemistry & Biochemistry, University of
California, Los Angeles 90095
| | - Rachel R. Ogorzalek Loo
- UCLA DOE Institute, University of California, Los Angeles
CA 90095
- Department of Chemistry & Biochemistry, University of
California, Los Angeles 90095
| | - Robert P. Gunsalus
- Department of Microbiology, Immunology, and Molecular
Genetics, University of California, Los Angeles, CA, USA
- UCLA-Molecular Biology Institute, University of California,
Los Angeles, CA USA
- UCLA DOE Institute, University of California, Los Angeles
CA 90095
| | - Michael J. McInerney
- Department of Microbiology and Plant Biology, University of
Oklahoma, Norman, OK, 73019
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53
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Wide diversity of methane and short-chain alkane metabolisms in uncultured archaea. Nat Microbiol 2019; 4:603-613. [PMID: 30833729 PMCID: PMC6453112 DOI: 10.1038/s41564-019-0363-3] [Citation(s) in RCA: 121] [Impact Index Per Article: 24.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2018] [Accepted: 01/07/2019] [Indexed: 12/29/2022]
Abstract
Methanogenesis is an ancient metabolism of key ecological relevance, with direct impact on the evolution of Earth’s climate. Recent results suggest that the diversity of methane metabolisms and their derivations have probably been vastly underestimated. Here, by probing thousands of publicly available metagenomes for homologues of methyl-coenzyme M reductase complex (MCR), we have obtained ten metagenome-assembled genomes (MAGs) belonging to potential methanogenic, anaerobic methanotrophic and short-chain alkane oxidizing archaea. Five of these MAGs represent under-sampled (e.g., Verstraetearchaeota, Methanonatronarchaeia, ANME-1) or previously genomically undescribed (ANME-2c) archaeal lineages. The remaining five MAGs correspond to lineages that are only distantly related to previously known methanogens and span the entire archaeal phylogeny. Comprehensive comparative annotation significantly expands the metabolic diversity and energy conservation systems of MCR-bearing archaea. It also suggests the potential existence of a yet uncharacterized type of methanogenesis linked to short-chain alkane/fatty acid oxidation in a previously undescribed class of archaea (‘Ca. Methanoliparia’). We redefine a common core of marker genes specific to methanogenic, anaerobic methanotrophic and short-chain alkane-oxidizing archaea, and propose a possible scenario for the evolutionary and functional transitions that led to the emergence of such metabolic diversity.
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54
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Guzman JJL, Sousa DZ, Angenent LT. Development of a Bioelectrochemical System as a Tool to Enrich H 2-Producing Syntrophic Bacteria. Front Microbiol 2019; 10:110. [PMID: 30804906 PMCID: PMC6370660 DOI: 10.3389/fmicb.2019.00110] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Accepted: 01/18/2019] [Indexed: 01/23/2023] Open
Abstract
Syntrophic microbial partnerships are found in many environments and play critical roles in wastewater treatment, global nutrient cycles, and gut systems. An important type of syntrophy for the anaerobic conversion of carboxylic acids is H2 syntrophy. In this type of microbial partnership, dissolved H2 is produced by a bacterium and rapidly consumed by an archeon (methanogen), resulting in methane gas. This is referred to as interspecies H2 transfer, and some conversions rely on this mechanism to become thermodynamically feasible. For this reason, syntrophic partners are often not possible to separate in the lab, which hampers the full understanding of their physiology. Bioelectrochemical systems (BESs) may show promise to ultimately separate and study the behavior of the syntrophic bacterium by employing an abiotic H2 oxidation reaction at the anode, actively removing dissolved H2. Here, we performed a proof-of-concept study to ascertain whether an H2-removing anode can: (1) provide a growth advantage for the syntrophic bacterium; and (2) compete with the methanogenic partner. A mathematical model was developed to design a BES to perform competition experiments. Indeed, the operated BES demonstrated the ability to provide a growth advantage to the syntrophic bacterium Syntrophus aciditrophicus compared to its methanogenic partner Methanospirillum hungatei when grown in co-culture. Further, the BES provided the never-before isolated Syntrophomonas zehnderi with a growth advantage compared to Methanobacterium formicicum. Our results demonstrate a potential to use this BES to enrich H2-sensitive syntrophic bacteria, and gives prospects for the development of an effective method for the separation of obligate syntrophs.
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Affiliation(s)
- Juan J L Guzman
- Biological and Environmental Engineering Department, Cornell University, Ithaca, NY, United States
| | - Diana Z Sousa
- Laboratory of Microbiology, Wageningen University and Research, Wageningen, Netherlands
| | - Largus T Angenent
- Centrum for Applied Geosciences, University of Tübingen, Tübingen, Germany
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55
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Narihiro T, Nobu MK, Bocher BTW, Mei R, Liu WT. Co-occurrence network analysis reveals thermodynamics-driven microbial interactions in methanogenic bioreactors. ENVIRONMENTAL MICROBIOLOGY REPORTS 2018; 10:673-685. [PMID: 30136425 DOI: 10.1111/1758-2229.12689] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2018] [Revised: 08/13/2018] [Accepted: 08/15/2018] [Indexed: 06/08/2023]
Abstract
Methanogenic bioreactors have been applied to treat purified terephthalic acid (PTA) wastewater containing complex aromatic compounds, such as terephthalic acid, para-toluic acid and benzoic acid. This study characterized the interaction of microbial populations in 42 samples obtained from 10 PTA-degrading methanogenic bioreactors. Approximately, 54 dominant populations (11 methanogens, 8 syntrophs and 35 functionally unknown clades) that represented 73.9% of total 16S rRNA gene iTag sequence reads were identified. Co-occurrence analysis based on the abundance of dominant OTUs showed two non-overlapping networks centred around aromatic compound- (group AR: Syntrophorhabdaceae, Syntrophus and Pelotomaculum) and fatty acid- (group FA: Smithella and Syntrophobacter) degrading syntrophs. Group AR syntrophs have no direct correlation with hydrogenotrophic methanogens, while those from group FA do. As degradation of aromatic compounds has a wider thermodynamic window than fatty acids, Group AR syntrophs may be less influenced by fluctuations in hydrogenotrophic methanogen abundance or may non-specifically interact with diverse methanogens. In both groups, network analysis reveals full-scale- and lab-scale-specific uncultivated taxa that may mediate interactions between syntrophs and methanogens, suggesting that those uncultivated taxa may support the degradation of aromatic compounds through uncharted ecophysiological traits. These observations suggest that organisms from multiple niches orchestrate their metabolic capacity in multiple interaction networks to effectively degrade PTA wastewater.
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Affiliation(s)
- Takashi Narihiro
- Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
- Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Ibaraki, 305-8566, Japan
| | - Masaru K Nobu
- Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Ben T W Bocher
- Petrochemicals Technology, BP America, Naperville, IL, 60563, USA
| | - Ran Mei
- Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Wen-Tso Liu
- Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
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56
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Botello Suárez WA, da Silva Vantini J, Duda RM, Giachetto PF, Cintra LC, Tiraboschi Ferro MI, de Oliveira RA. Predominance of syntrophic bacteria, Methanosaeta and Methanoculleus in a two-stage up-flow anaerobic sludge blanket reactor treating coffee processing wastewater at high organic loading rate. BIORESOURCE TECHNOLOGY 2018; 268:158-168. [PMID: 30077172 DOI: 10.1016/j.biortech.2018.06.091] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Revised: 06/26/2018] [Accepted: 06/27/2018] [Indexed: 06/08/2023]
Abstract
The effect of the organic loading rate (OLR) on the performance and microbial composition of a two-stage UASB system treating coffee processing wastewater was assessed. The system was operated with OLR up to 18.2 g COD (L d)-1 and effluent recirculation. Methane production and effluent characteristics were monitored. The microbial composition was examined through next-generation sequencing and qPCR from the anaerobic sludge of the first reactor (R1) operated at low and high OLR. The system showed operational stability, obtaining a maximum methane production of 2.2 L CH4 (L d)-1, with a removal efficiency of COD and phenolic compounds of 84 and 73%, respectively. The performance of R1 at high OLR in steady conditions was associated with an appropriate proportion of nutrients (particularly Fe) and a marked increase of the syntrophic bacteria Syntrophus and Candidatus Cloacimonas, and acetoclastic and hydrogenotrophic methanogens, mainly Methanosaeta, Methanoculleus, Methanobacterium and Methanomassiliicoccus.
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Affiliation(s)
- Wilmar Alirio Botello Suárez
- Post-Graduate Program in Agricultural and Livestock Microbiology, São Paulo State University (UNESP), School of Agricultural and Veterinarian Sciences, Jaboticabal, SP, Brazil; Laboratory of Environmental Sanitation, Department of Rural Engineering, São Paulo State University (UNESP), School of Agricultural and Veterinarian Sciences, Jaboticabal, SP, Brazil
| | - Juliana da Silva Vantini
- Post-Graduate Program in Agricultural and Livestock Microbiology, São Paulo State University (UNESP), School of Agricultural and Veterinarian Sciences, Jaboticabal, SP, Brazil; Laboratory of Biochemistry and Molecular Biology, Department of Technology, São Paulo State University (UNESP), School of Agricultural and Veterinarian Sciences, Jaboticabal, SP, Brazil
| | | | | | | | - Maria Inês Tiraboschi Ferro
- Post-Graduate Program in Agricultural and Livestock Microbiology, São Paulo State University (UNESP), School of Agricultural and Veterinarian Sciences, Jaboticabal, SP, Brazil; Laboratory of Biochemistry and Molecular Biology, Department of Technology, São Paulo State University (UNESP), School of Agricultural and Veterinarian Sciences, Jaboticabal, SP, Brazil
| | - Roberto Alves de Oliveira
- Post-Graduate Program in Agricultural and Livestock Microbiology, São Paulo State University (UNESP), School of Agricultural and Veterinarian Sciences, Jaboticabal, SP, Brazil; Laboratory of Environmental Sanitation, Department of Rural Engineering, São Paulo State University (UNESP), School of Agricultural and Veterinarian Sciences, Jaboticabal, SP, Brazil.
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57
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Hidalgo-Ahumada CAP, Nobu MK, Narihiro T, Tamaki H, Liu WT, Kamagata Y, Stams AJM, Imachi H, Sousa DZ. Novel energy conservation strategies and behaviour of Pelotomaculum schinkii driving syntrophic propionate catabolism. Environ Microbiol 2018; 20:4503-4511. [PMID: 30126076 DOI: 10.1111/1462-2920.14388] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Revised: 08/02/2018] [Accepted: 08/15/2018] [Indexed: 11/29/2022]
Abstract
Under methanogenic conditions, short-chain fatty acids are common byproducts from degradation of organic compounds and conversion of these acids is an important component of the global carbon cycle. Due to the thermodynamic difficulty of propionate degradation, this process requires syntrophic interaction between a bacterium and partner methanogen; however, the metabolic strategies and behaviour involved are not fully understood. In this study, the first genome analysis of obligately syntrophic propionate degraders (Pelotomaculum schinkii HH and P. propionicicum MGP) and comparison with other syntrophic propionate degrader genomes elucidated novel components of energy metabolism behind Pelotomaculum propionate oxidation. Combined with transcriptomic examination of P. schinkii behaviour in co-culture with Methanospirillum hungatei, we found that formate may be the preferred electron carrier for P. schinkii syntrophy. Propionate-derived menaquinol may be primarily re-oxidized to formate, and energy was conserved during formate generation through newly proposed proton-pumping formate extrusion. P. schinkii did not overexpress conventional energy metabolism associated with a model syntrophic propionate degrader Syntrophobacter fumaroxidans MPOB (i.e., CoA transferase, Fix and Rnf). We also found that P. schinkii and the partner methanogen may also interact through flagellar contact and amino acid and fructose exchange. These findings provide new understanding of syntrophic energy acquisition and interactions.
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Affiliation(s)
- Catalina A P Hidalgo-Ahumada
- Laboratory of Microbiology, Wageningen University & Research, Stippeneng 4, 6708 WE Wageningen, Wageningen, The Netherlands
| | - Masaru K Nobu
- Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba, Ibaraki, 305-8566, Japan
| | - Takashi Narihiro
- Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba, Ibaraki, 305-8566, Japan
| | - Hideyuki Tamaki
- Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba, Ibaraki, 305-8566, Japan
| | - Wen-Tso Liu
- Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, 205 North Mathews Ave, Urbana, IL, 61801, USA
| | - Yoichi Kamagata
- Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba, Ibaraki, 305-8566, Japan
| | - Alfons J M Stams
- Laboratory of Microbiology, Wageningen University & Research, Stippeneng 4, 6708 WE Wageningen, Wageningen, The Netherlands.,Center of Biological Engineering, University of Minho, Campus de Gualtar, 4710-057, Braga, Portugal
| | - Hiroyuki Imachi
- Department of Subsurface Geobiological Analysis and Research (D-SUGAR), Japan Agency for Marine-Earth Science & Technology (JAMSTEC), Yokosuka, Kanagawa, 237-0061, Japan
| | - Diana Z Sousa
- Laboratory of Microbiology, Wageningen University & Research, Stippeneng 4, 6708 WE Wageningen, Wageningen, The Netherlands
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58
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Sorokin DY, Messina E, La Cono V, Ferrer M, Ciordia S, Mena MC, Toshchakov SV, Golyshin PN, Yakimov MM. Sulfur Respiration in a Group of Facultatively Anaerobic Natronoarchaea Ubiquitous in Hypersaline Soda Lakes. Front Microbiol 2018; 9:2359. [PMID: 30333814 PMCID: PMC6176080 DOI: 10.3389/fmicb.2018.02359] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2018] [Accepted: 09/14/2018] [Indexed: 11/21/2022] Open
Abstract
The ubiquity of strictly anaerobic sulfur-respiring haloarchaea in hypersaline systems with circumneutral pH has shaken a traditional concept of this group as predominantly aerobic heterotrophs. Here, we demonstrated that this functional group of haloarchaea also has its representatives in hypersaline alkaline lakes. Sediments from various hypersaline soda lakes showed high activity of sulfur reduction only partially inhibited by antibiotics. Eight pure cultures of sulfur-reducing natronoarchaea were isolated from such sediments using formate and butyrate as electron donors and sulfur as an electron acceptor. Unlike strict anaerobic haloarchaea, these novel sulfur-reducing natronoarchaea are facultative anaerobes, whose metabolic capabilities were inferred from cultivation experiments and genomic/proteomic reconstruction. While sharing many physiological traits with strict anaerobic haloarchaea, following metabolic distinctions make these new organisms be successful in both anoxic and aerobic habitats: the recruiting of heme-copper quinol oxidases as terminal electron sink in aerobic respiratory chain and the utilization of formate, hydrogen or short-chain fatty acids as electron donors during anaerobic growth with elemental sulfur. Obtained results significantly advance the emerging concept of halo(natrono)archaea as important players in the anaerobic sulfur and carbon cycling in various salt-saturated habitats.
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Affiliation(s)
- Dimitry Y Sorokin
- Winogradsky Institute of Microbiology, Research Centre of Biotechnology, Russian Academy of Sciences, Moscow, Russia.,Department of Biotechnology, Delft University of Technology, Delft, Netherlands
| | - Enzo Messina
- Institute for Coastal Marine Environment, National Research Council, Messina, Italy
| | - Violetta La Cono
- Institute for Coastal Marine Environment, National Research Council, Messina, Italy
| | - Manuel Ferrer
- Institute of Catalysis, Spanish National Research Council, Madrid, Spain
| | - Sergio Ciordia
- Proteomics Unit, National Center for Biotechnology, Spanish National Research Council, Madrid, Spain
| | - Maria C Mena
- Proteomics Unit, National Center for Biotechnology, Spanish National Research Council, Madrid, Spain
| | - Stepan V Toshchakov
- Winogradsky Institute of Microbiology, Research Centre of Biotechnology, Russian Academy of Sciences, Moscow, Russia.,Immanuel Kant Baltic Federal University, Kaliningrad, Russia
| | - Peter N Golyshin
- School of Biological Sciences and The Centre for Environmental Biotechnology, Bangor University, Bangor, United Kingdom
| | - Michail M Yakimov
- Institute for Coastal Marine Environment, National Research Council, Messina, Italy.,Immanuel Kant Baltic Federal University, Kaliningrad, Russia
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59
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Qian HX, Liao RZ. QM/MM Study of Tungsten-Dependent Benzoyl-Coenzyme A Reductase: Rationalization of Regioselectivity and Predication of W vs Mo Selectivity. Inorg Chem 2018; 57:10667-10678. [DOI: 10.1021/acs.inorgchem.8b01328] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Hui-Xia Qian
- Key Laboratory of Material Chemistry for Energy Conversion and Storage, Ministry of Education, Hubei Key Laboratory of Bioinorganic Chemistry and Materia Medica, Hubei Key Laboratory of Materials Chemistry and Service Failure, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Rong-Zhen Liao
- Key Laboratory of Material Chemistry for Energy Conversion and Storage, Ministry of Education, Hubei Key Laboratory of Bioinorganic Chemistry and Materia Medica, Hubei Key Laboratory of Materials Chemistry and Service Failure, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
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60
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Sedano-Núñez VT, Boeren S, Stams AJM, Plugge CM. Comparative proteome analysis of propionate degradation by Syntrophobacter fumaroxidans in pure culture and in coculture with methanogens. Environ Microbiol 2018; 20:1842-1856. [PMID: 29611893 PMCID: PMC5947623 DOI: 10.1111/1462-2920.14119] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Revised: 03/20/2018] [Accepted: 03/24/2018] [Indexed: 11/28/2022]
Abstract
Syntrophobacter fumaroxidans is a sulfate-reducing bacterium able to grow on propionate axenically or in syntrophic interaction with methanogens or other sulfate-reducing bacteria. We performed a proteome analysis of S. fumaroxidans growing with propionate axenically with sulfate or fumarate, and in syntrophy with Methanospirillum hungatei, Methanobacterium formicicum or Desulfovibrio desulfuricans. Special attention was put on the role of hydrogen and formate in interspecies electron transfer (IET) and energy conservation. Formate dehydrogenase Fdh1 and hydrogenase Hox were the main confurcating enzymes used for energy conservation. In the periplasm, Fdh2 and hydrogenase Hyn play an important role in reverse electron transport associated with succinate oxidation. Periplasmic Fdh3 and Fdh5 were involved in IET. The sulfate reduction pathway was poorly regulated and many enzymes associated with sulfate reduction (Sat, HppA, AprAB, DsrAB and DsrC) were abundant even at conditions where sulfate was not present. Proteins similar to heterodisulfide reductases (Hdr) were abundant. Hdr/Flox was detected in all conditions while HdrABC/HdrL was exclusively detected when sulfate was available; these complexes most likely confurcate electrons. Our results suggest that S. fumaroxidans mainly used formate for electron release and that different confurcating mechanisms were used in its sulfidogenic metabolism.
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Affiliation(s)
- Vicente T Sedano-Núñez
- Laboratory of Microbiology, Wageningen University & Research, Stippeneng 4, Wageningen, The Netherlands
| | - Sjef Boeren
- Laboratory of Biochemistry, Wageningen University & Research, Stippeneng 4, Wageningen, The Netherlands
| | - Alfons J M Stams
- Laboratory of Microbiology, Wageningen University & Research, Stippeneng 4, Wageningen, The Netherlands.,Centre of Biological Engineering, University of Minho, Campus de Gualtar, Braga, 4710-057, Portugal
| | - Caroline M Plugge
- Laboratory of Microbiology, Wageningen University & Research, Stippeneng 4, Wageningen, The Netherlands
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61
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Redundancy in Anaerobic Digestion Microbiomes during Disturbances by the Antibiotic Monensin. Appl Environ Microbiol 2018; 84:AEM.02692-17. [PMID: 29500266 PMCID: PMC5930344 DOI: 10.1128/aem.02692-17] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2017] [Accepted: 02/22/2018] [Indexed: 01/08/2023] Open
Abstract
The antibiotic monensin is fed to dairy cows to increase milk production efficiency. A fraction of this monensin is excreted into the cow manure. Previous studies have found that cow manure containing monensin can negatively impact the performance of anaerobic digesters, especially upon first introduction. Few studies have examined whether the anaerobic digester microbiome can adapt to monensin during the operating time. Here, we conducted a long-term time series study of four lab-scale anaerobic digesters fed with cow manure. We examined changes in both the microbiome composition and function of the anaerobic digesters when subjected to the dairy antibiotic monensin. In our digesters, monensin was not rapidly degraded under anaerobic conditions. The two anaerobic digesters that were subjected to manure from monensin feed-dosed cows exhibited relatively small changes in microbiome composition and function due to relatively low monensin concentrations. At higher concentrations of monensin, which we dosed directly to control manure (from dairy cows without monensin), we observed major changes in the microbiome composition and function of two anaerobic digesters. A rapid introduction of monensin to one of these anaerobic digesters led to the impairment of methane production. Conversely, more gradual additions of the same concentrations of monensin to the other anaerobic digester led to the adaptation of the anaerobic digester microbiomes to the relatively high monensin concentrations. A member of the candidate OP11 (Microgenomates) phylum arose in this anaerobic digester and appeared to be redundant with certain Bacteroidetes phylum members, which previously were dominating.IMPORTANCE Monensin is a common antibiotic given to dairy cows in the United States and is partly excreted with dairy manure. An improved understanding of how monensin affects the anaerobic digester microbiome composition and function is important to prevent process failure for farm-based anaerobic digesters. This time series study demonstrates how anaerobic digester microbiomes are inert to low monensin concentrations and can adapt to relatively high monensin concentrations by redundancy in an already existing population. Therefore, our work provides further insight into the importance of microbiome redundancy in maintaining the stability of anaerobic digesters.
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Syntrophic pathways for microbial mercury methylation. ISME JOURNAL 2018; 12:1826-1835. [PMID: 29599522 DOI: 10.1038/s41396-018-0106-0] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2017] [Revised: 02/28/2018] [Accepted: 03/05/2018] [Indexed: 01/13/2023]
Abstract
Exposure to dietary sources of methylmercury (MeHg) is the focus of public health concerns with environmental mercury (Hg) contamination. MeHg is formed in anoxic environments by anaerobic microorganisms. This process has been studied mostly with single-species culture incubations, although the relevance of such studies to Hg(II)-methylation in situ is limited because microbial activities in the environment are critically modulated by interactions among microbial functional groups. Here we describe experiments in which Hg(II)-methylation was examined within the context of various microbial syntrophies. We show enhanced Hg(II)-methylation under conditions that established syntrophy by interspecies hydrogen and acetate transfer. Relative to activity of monocultures, interactions of Hg(II) methylating sulfate-reducing bacteria with a methanogen stimulated potential Hg(II)-methylation rates 2-fold to 9-fold, and with Syntrophobacter sp. 1.7-fold to 1.8-fold; those of a Hg(II) methylating Syntrophobacter sp. with a methanogen increased Hg(II)-methylation 2-fold. Under sulfate-depleted conditions, higher Hg(II)-methylation rates in the syntrophic incubations corresponded to higher free energy yields (ΔG°') than in the monocultures. Based on energetic considerations, we therefore propose that syntrophic microbial interactions are likely a major source of MeHg in sulfate- and iron-limited anoxic environments while in sulfate-replete environments, MeHg formation via sulfate reduction dominates.
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A benzene-degrading nitrate-reducing microbial consortium displays aerobic and anaerobic benzene degradation pathways. Sci Rep 2018. [PMID: 29540736 PMCID: PMC5852087 DOI: 10.1038/s41598-018-22617-x] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
In this study, we report transcription of genes involved in aerobic and anaerobic benzene degradation pathways in a benzene-degrading denitrifying continuous culture. Transcripts associated with the family Peptococcaceae dominated all samples (21-36% relative abundance) indicating their key role in the community. We found a highly transcribed gene cluster encoding a presumed anaerobic benzene carboxylase (AbcA and AbcD) and a benzoate-coenzyme A ligase (BzlA). Predicted gene products showed >96% amino acid identity and similar gene order to the corresponding benzene degradation gene cluster described previously, providing further evidence for anaerobic benzene activation via carboxylation. For subsequent benzoyl-CoA dearomatization, bam-like genes analogous to the ones found in other strict anaerobes were transcribed, whereas gene transcripts involved in downstream benzoyl-CoA degradation were mostly analogous to the ones described in facultative anaerobes. The concurrent transcription of genes encoding enzymes involved in oxygenase-mediated aerobic benzene degradation suggested oxygen presence in the culture, possibly formed via a recently identified nitric oxide dismutase (Nod). Although we were unable to detect transcription of Nod-encoding genes, addition of nitrite and formate to the continuous culture showed indication for oxygen production. Such an oxygen production would enable aerobic microbes to thrive in oxygen-depleted and nitrate-containing subsurface environments contaminated with hydrocarbons.
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Buckel W, Thauer RK. Flavin-Based Electron Bifurcation, Ferredoxin, Flavodoxin, and Anaerobic Respiration With Protons (Ech) or NAD + (Rnf) as Electron Acceptors: A Historical Review. Front Microbiol 2018; 9:401. [PMID: 29593673 PMCID: PMC5861303 DOI: 10.3389/fmicb.2018.00401] [Citation(s) in RCA: 199] [Impact Index Per Article: 33.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2017] [Accepted: 02/21/2018] [Indexed: 12/19/2022] Open
Abstract
Flavin-based electron bifurcation is a newly discovered mechanism, by which a hydride electron pair from NAD(P)H, coenzyme F420H2, H2, or formate is split by flavoproteins into one-electron with a more negative reduction potential and one with a more positive reduction potential than that of the electron pair. Via this mechanism microorganisms generate low- potential electrons for the reduction of ferredoxins (Fd) and flavodoxins (Fld). The first example was described in 2008 when it was found that the butyryl-CoA dehydrogenase-electron-transferring flavoprotein complex (Bcd-EtfAB) of Clostridium kluyveri couples the endergonic reduction of ferredoxin (E0′ = −420 mV) with NADH (−320 mV) to the exergonic reduction of crotonyl-CoA to butyryl-CoA (−10 mV) with NADH. The discovery was followed by the finding of an electron-bifurcating Fd- and NAD-dependent [FeFe]-hydrogenase (HydABC) in Thermotoga maritima (2009), Fd-dependent transhydrogenase (NfnAB) in various bacteria and archaea (2010), Fd- and H2-dependent heterodisulfide reductase (MvhADG-HdrABC) in methanogenic archaea (2011), Fd- and NADH-dependent caffeyl-CoA reductase (CarCDE) in Acetobacterium woodii (2013), Fd- and NAD-dependent formate dehydrogenase (HylABC-FdhF2) in Clostridium acidi-urici (2013), Fd- and NADP-dependent [FeFe]-hydrogenase (HytA-E) in Clostridium autoethanogrenum (2013), Fd(?)- and NADH-dependent methylene-tetrahydrofolate reductase (MetFV-HdrABC-MvhD) in Moorella thermoacetica (2014), Fd- and NAD-dependent lactate dehydrogenase (LctBCD) in A. woodii (2015), Fd- and F420H2-dependent heterodisulfide reductase (HdrA2B2C2) in Methanosarcina acetivorans (2017), and Fd- and NADH-dependent ubiquinol reductase (FixABCX) in Azotobacter vinelandii (2017). The electron-bifurcating flavoprotein complexes known to date fall into four groups that have evolved independently, namely those containing EtfAB (CarED, LctCB, FixBA) with bound FAD, a NuoF homolog (HydB, HytB, or HylB) harboring FMN, NfnB with bound FAD, or HdrA harboring FAD. All these flavoproteins are cytoplasmic except for the membrane-associated protein FixABCX. The organisms—in which they have been found—are strictly anaerobic microorganisms except for the aerobe A. vinelandii. The electron-bifurcating complexes are involved in a variety of processes such as butyric acid fermentation, methanogenesis, acetogenesis, anaerobic lactate oxidation, dissimilatory sulfate reduction, anaerobic- dearomatization, nitrogen fixation, and CO2 fixation. They contribute to energy conservation via the energy-converting ferredoxin: NAD+ reductase complex Rnf or the energy-converting ferredoxin-dependent hydrogenase complex Ech. This Review describes how this mechanism was discovered.
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Affiliation(s)
- Wolfgang Buckel
- Laboratory for Microbiology, Faculty of Biology, Philipps-Universität Marburg, Marburg, Germany
| | - Rudolf K Thauer
- Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
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Leng L, Yang P, Singh S, Zhuang H, Xu L, Chen WH, Dolfing J, Li D, Zhang Y, Zeng H, Chu W, Lee PH. A review on the bioenergetics of anaerobic microbial metabolism close to the thermodynamic limits and its implications for digestion applications. BIORESOURCE TECHNOLOGY 2018; 247:1095-1106. [PMID: 28958887 DOI: 10.1016/j.biortech.2017.09.103] [Citation(s) in RCA: 78] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2017] [Revised: 09/09/2017] [Accepted: 09/15/2017] [Indexed: 05/24/2023]
Abstract
The exploration of the energetics of anaerobic digestion systems can reveal how microorganisms cooperate efficiently for cell growth and methane production, especially under low-substrate conditions. The establishment of a thermodynamically interdependent partnership, called anaerobic syntrophy, allows unfavorable reactions to proceed. Interspecies electron transfer and the concentrations of electron carriers are crucial for maintaining this mutualistic activity. This critical review summarizes the functional microorganisms and syntroph partners, particularly in the metabolic pathways and energy conservation of syntrophs. The kinetics and thermodynamics of propionate degradation to methane, reversibility of the acetate oxidation process, and estimation of microbial growth are summarized. The various routes of interspecies electron transfer, reverse electron transfer, and Poly-β-hydroxyalkanoate formation in the syntrophic community are also reviewed. Finally, promising and critical directions of future research are proposed. Fundamental insight in the activities and interactions involved in AD systems could serve as a guidance for engineered systems optimization and upgrade.
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Affiliation(s)
- Ling Leng
- Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong
| | - Peixian Yang
- Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong
| | - Shubham Singh
- Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong
| | - Huichuan Zhuang
- Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong
| | - Linji Xu
- Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong
| | - Wen-Hsing Chen
- Department of Environmental Engineering, National Ilan University, Yilan 260, Taiwan
| | - Jan Dolfing
- School of Civil Engineering and Geosciences, Newcastle University, Newcastle NE1 7RU, UK
| | - Dong Li
- Key Laboratory of Beijing for Water Quality Science and Water Environment Recovery Engineering, Beijing University of Technology, Beijing 100124, China
| | - Yan Zhang
- Key Laboratory of Beijing for Water Quality Science and Water Environment Recovery Engineering, Beijing University of Technology, Beijing 100124, China
| | - Huiping Zeng
- Key Laboratory of Beijing for Water Quality Science and Water Environment Recovery Engineering, Beijing University of Technology, Beijing 100124, China
| | - Wei Chu
- Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong
| | - Po-Heng Lee
- Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong.
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Lecker B, Illi L, Lemmer A, Oechsner H. Biological hydrogen methanation - A review. BIORESOURCE TECHNOLOGY 2017; 245:1220-1228. [PMID: 28893503 DOI: 10.1016/j.biortech.2017.08.176] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2017] [Revised: 08/28/2017] [Accepted: 08/29/2017] [Indexed: 05/07/2023]
Abstract
Surplus energy out of fluctuating energy sources like wind and solar energy is strongly increasing. Biological hydrogen (H2) methanation (BHM) is a highly promising approach to move the type of energy from electricity to natural gas via electrolysis and the subsequent step of the Sabatier-reaction. This review provides an overview of the numerous studies concerning the topic of BHM. The technical and biological parameters regarding the research results of these studies are compared and analyzed hereafter. A holistic view on how to overcome physical limitations of the fermentation process, such as gas-liquid mass transfer or a rise of the pH value, and on the enhancement of environmental circumstances for the bacterial biomass are delivered within. With regards to ex-situ methanation, the evaluated studies show a distinct connection between methane production and the methane percentage in the off-gas.
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Affiliation(s)
- Bernhard Lecker
- University of Hohenheim, State Institute of Agricultural Engineering and Bioenergy, Garbenstraße 9, 70599 Stuttgart, Germany.
| | - Lukas Illi
- University of Hohenheim, State Institute of Agricultural Engineering and Bioenergy, Garbenstraße 9, 70599 Stuttgart, Germany
| | - Andreas Lemmer
- University of Hohenheim, State Institute of Agricultural Engineering and Bioenergy, Garbenstraße 9, 70599 Stuttgart, Germany
| | - Hans Oechsner
- University of Hohenheim, State Institute of Agricultural Engineering and Bioenergy, Garbenstraße 9, 70599 Stuttgart, Germany
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67
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Hillesland KL. Evolution on the bright side of life: microorganisms and the evolution of mutualism. Ann N Y Acad Sci 2017; 1422:88-103. [PMID: 29194650 DOI: 10.1111/nyas.13515] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Revised: 09/05/2017] [Accepted: 09/11/2017] [Indexed: 01/15/2023]
Abstract
Mutualistic interactions, where two interacting species have a net beneficial effect on each other's fitness, play a crucial role in the survival and evolution of many species. Despite substantial empirical and theoretical work in past decades, the impact of these interactions on natural selection is not fully understood. In addition, mutualisms between microorganisms have been largely ignored, even though they are ecologically important and can be used as tools to bridge the gap between theory and empirical work. Here, I describe two problems with our current understanding of natural selection in mutualism and highlight the properties of microbial mutualisms that could help solve them. One problem is that bias and methodological problems have limited our understanding of the variety of mechanisms by which species may adapt to mutualism. Another problem is that it is rare for experiments testing coevolution in mutualism to address whether each species has adapted to evolutionary changes in its partner. These problems can be addressed with genome resequencing and time-shift experiments, techniques that are easier to perform in microorganisms. In addition, microbial mutualisms may inspire novel insights and hypotheses about natural selection in mutualism.
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Liu M, Wang S, Nobu MK, Bocher BTW, Kaley SA, Liu WT. Impacts of biostimulation and bioaugmentation on the performance and microbial ecology in methanogenic reactors treating purified terephthalic acid wastewater. WATER RESEARCH 2017; 122:308-316. [PMID: 28614743 DOI: 10.1016/j.watres.2017.06.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Revised: 05/08/2017] [Accepted: 06/03/2017] [Indexed: 06/07/2023]
Abstract
Up-flow anaerobic sludge blanket (UASB) processes treating purified terephthalic acid (PTA) wastewater often face challenges associated with biomass loss. As excessive biomass loss could lead to deterioration of PTA removal, biostimulation and bioaugmentation were often practiced without understanding the microbial impact in UASB. Three laboratory-scale UASB reactors were operated with synthetic PTA wastewater as the feed, with two added with co-substrate (glucose or molasses) on Day 170 for 90 days, and one with external granules on Day 118. Throughout the operation, treatment performance was measured together with the analysis of microbial communities of biomass samples using 16S rRNA-based gene Illumina sequencing. Glucose amendment destabilized both terephthalic acid and para-toluic acid removal, while molasses amendment improved para-toluic acid removal. Both substrate addition generally led to decreases in the abundances of syntrophs and methanogens and increases in carbohydrate-fermenting bacteria in the granular sludge. Regarding bioaugmentation, paper mill granule addition led to a temporary crash of terephthalic acid removal for 42 days, and deterioration of para-toluic acid removal throughout the operation. Syntrophs and methanogens were observed to colonize on the paper mill granules after three months, meanwhile growth of methanogens were stimulated on the PTA granules added initially. Overall, proper level of molasses amendment and external granule inoculation could be promising strategies to make up for biomass loss during the operation of PTA-degrading UASB.
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Affiliation(s)
- Miaomiao Liu
- Department of Civil and Environmental Engineering, University of Illinois, Urbana-Champaign, Urbana, IL, USA
| | - Shanquan Wang
- Department of Civil and Environmental Engineering, University of Illinois, Urbana-Champaign, Urbana, IL, USA
| | - Masaru Konishi Nobu
- Department of Civil and Environmental Engineering, University of Illinois, Urbana-Champaign, Urbana, IL, USA
| | | | - Scott A Kaley
- BP America, Petrochemicals Technology, Naperville, IL, USA
| | - Wen-Tso Liu
- Department of Civil and Environmental Engineering, University of Illinois, Urbana-Champaign, Urbana, IL, USA.
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Qin QS, Feng DS, Liu PF, He Q, Li X, Liu AM, Zhang H, Hu GQ, Cheng L. Metagenomic Characterization of Candidatus Smithella cisternae Strain M82_1, a Syntrophic Alkane-Degrading Bacteria, Enriched from the Shengli Oil Field. Microbes Environ 2017; 32:234-243. [PMID: 28781346 PMCID: PMC5606693 DOI: 10.1264/jsme2.me17022] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The methanogenic degradation of hydrocarbons plays an important role in hydrocarbon-contaminated environments in the absence of an external electron acceptor. Members of Syntrophaceae sublineages were previously reported to be responsible for syntrophic alkane degradation. However, limited information is currently available on their physiological capabilities in nature because it is very challenging to cultivate these as-yet uncultured microbes. We herein performed metagenomic sequencing of the methanogenic hexadecane-degrading culture M82 and recovered a nearly complete genome (2.75 Mb, estimated completeness ≥97%) belonging to Syntrophaceae sublineage II. The assembly genome was tentatively named “Candidatus Smithella cisternae strain M82_1”. Genes encoding alkylsuccinate synthase for alkane activation were identified, suggesting that this organism is capable of oxidizing alkanes through fumarate addition. This capability was further supported by the detection of methyl pentadecyl succinic acid and methyl tetradecyl succinic acid in cultures amended with hexadecane and pentadecane, respectively. Genes encoding enzymes for the β-oxidation of long-chain fatty acids and butyrate were also identified. The electron transfer flavoprotein/DUF224 complex is presumed to link electron flow from acyl-CoA dehydrogenase to a membrane hydrogenase or formate dehydrogenase. Although no indications of Rnf complexes were detected, genes encoding electron-confurcating hydrogenase and formate dehydrogenase were proposed to couple the thermodynamically favorable oxidation of ferredoxin to generate H2 and formate from NADH. Strain M82_1 synthesized ATP from acetyl-CoA by substrate-level phosphorylation or F1F0-ATP synthases. These results provide an insight into the potential metabolic traits and ecophysiological roles of the syntrophic alkane degrader Syntrophaceae.
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Affiliation(s)
- Qian-Shan Qin
- Key Laboratory of Development and Application of Rural Renewable Energy, Biogas Institute of Ministry of Agriculture
| | | | - Peng-Fei Liu
- Key Laboratory of Development and Application of Rural Renewable Energy, Biogas Institute of Ministry of Agriculture
| | - Qiao He
- Key Laboratory of Development and Application of Rural Renewable Energy, Biogas Institute of Ministry of Agriculture
| | - Xia Li
- Key Laboratory of Development and Application of Rural Renewable Energy, Biogas Institute of Ministry of Agriculture
| | | | - Hui Zhang
- Key Laboratory of Development and Application of Rural Renewable Energy, Biogas Institute of Ministry of Agriculture
| | - Guo-Quan Hu
- Key Laboratory of Development and Application of Rural Renewable Energy, Biogas Institute of Ministry of Agriculture
| | - Lei Cheng
- Key Laboratory of Development and Application of Rural Renewable Energy, Biogas Institute of Ministry of Agriculture
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70
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Liang R, Duncan KE, Le Borgne S, Davidova I, Yakimov MM, Suflita JM. Microbial activities in hydrocarbon-laden wastewaters: Impact on diesel fuel stability and the biocorrosion of carbon steel. J Biotechnol 2017; 256:68-75. [DOI: 10.1016/j.jbiotec.2017.02.021] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2016] [Revised: 02/18/2017] [Accepted: 02/19/2017] [Indexed: 10/20/2022]
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71
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Argiroff WA, Zak DR, Lanser CM, Wiley MJ. Microbial Community Functional Potential and Composition Are Shaped by Hydrologic Connectivity in Riverine Floodplain Soils. MICROBIAL ECOLOGY 2017; 73:630-644. [PMID: 27807645 DOI: 10.1007/s00248-016-0883-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Accepted: 10/17/2016] [Indexed: 05/12/2023]
Abstract
Riverine floodplains are ecologically and economically valuable ecosystems that are heavily threatened by anthropogenic stressors. Microbial communities in floodplain soils mediate critical biogeochemical processes, yet we understand little about the relationship between these communities and variation in hydrologic connectivity related to land management or topography. Here, we present metagenomic evidence that differences among microbial communities in three floodplain soils correspond to a long-term gradient of hydrologic connectivity. Specifically, all strictly anaerobic taxa and metabolic pathways were positively associated with increased hydrologic connectivity and flooding frequency. In contrast, most aerobic taxa and all strictly aerobic pathways were negatively related to hydrologic connectivity and flooding frequency. Furthermore, the genetic potential to metabolize organic compounds tended to decrease as hydrologic connectivity increased, which may reflect either the observed concomitant decline of soil organic matter or the parallel increase in both anaerobic taxa and pathways. A decline in soil N, accompanied by an increased genetic potential for oligotrophic N acquisition subsystems, suggests that soil nutrients also shape microbial communities in these soils. We conclude that differences among floodplain soil microbial communities can be conceptualized along a gradient of hydrologic connectivity. Additionally, we show that these differences are likely due to connectivity-related variation in flooding frequency, soil organic matter, and soil N. Our findings are particularly relevant to the restoration and management of microbially mediated biogeochemical processes in riverine floodplain wetlands.
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Affiliation(s)
- William A Argiroff
- School of Natural Resources and Environment, University of Michigan, 440 Church St., Ann Arbor, MI, 48109, USA.
| | - Donald R Zak
- School of Natural Resources and Environment, University of Michigan, 440 Church St., Ann Arbor, MI, 48109, USA
- Department of Ecology and Evolutionary Biology, University of Michigan, 830 North University, Ann Arbor, MI, 48109, USA
| | - Christine M Lanser
- School of Natural Resources and Environment, University of Michigan, 440 Church St., Ann Arbor, MI, 48109, USA
| | - Michael J Wiley
- School of Natural Resources and Environment, University of Michigan, 440 Church St., Ann Arbor, MI, 48109, USA
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Hamann E, Tegetmeyer HE, Riedel D, Littmann S, Ahmerkamp S, Chen J, Hach PF, Strous M. Syntrophic linkage between predatory Carpediemonas and specific prokaryotic populations. ISME JOURNAL 2017; 11:1205-1217. [PMID: 28211847 PMCID: PMC5437931 DOI: 10.1038/ismej.2016.197] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Revised: 10/28/2016] [Accepted: 12/07/2016] [Indexed: 12/21/2022]
Abstract
Most anoxic environments are populated by small (<10 μm) heterotrophic eukaryotes that prey on different microbial community members. How predatory eukaryotes engage in beneficial interactions with other microbes has rarely been investigated so far. Here, we studied an example of such an interaction by cultivating the anerobic marine flagellate, Carpediemonas frisia sp. nov. (supergroup Excavata), with parts of its naturally associated microbiome. This microbiome consisted of so far uncultivated members of the Deltaproteobacteria, Bacteroidetes, Firmicutes, Verrucomicrobia and Nanoarchaeota. Using genome and transcriptome informed metabolic network modeling, we showed that Carpediemonas stimulated prokaryotic growth through the release of predigested biomolecules such as proteins, sugars, organic acids and hydrogen. Transcriptional gene activities suggested niche separation between biopolymer degrading Bacteroidetes, monomer utilizing Firmicutes and Nanoarchaeota and hydrogen oxidizing Deltaproteobacteria. An efficient metabolite exchange between the different community members appeared to be promoted by the formation of multispecies aggregates. Physiological experiments showed that Carpediemonas could also benefit from an association to these aggregates, as it facilitated the removal of inhibiting metabolites and increased the availability of prey bacteria. Taken together, our results provide a framework to understand how predatory microbial eukaryotes engage, across trophic levels, in beneficial interactions with specific prokaryotic populations.
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Affiliation(s)
- Emmo Hamann
- Department of Geoscience, University of Calgary, Calgary, AB, Canada.,Max Planck Institute for Marine Microbiology, Bremen, Germany
| | - Halina E Tegetmeyer
- Max Planck Institute for Marine Microbiology, Bremen, Germany.,Institute for Genome Research and Systems Biology, Center for Biotechnology, Bielefeld University, Bielefeld, Germany
| | - Dietmar Riedel
- Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Sten Littmann
- Max Planck Institute for Marine Microbiology, Bremen, Germany
| | | | - Jianwei Chen
- Department of Geoscience, University of Calgary, Calgary, AB, Canada.,Max Planck Institute for Marine Microbiology, Bremen, Germany
| | - Philipp F Hach
- Max Planck Institute for Marine Microbiology, Bremen, Germany
| | - Marc Strous
- Department of Geoscience, University of Calgary, Calgary, AB, Canada.,Max Planck Institute for Marine Microbiology, Bremen, Germany.,Institute for Genome Research and Systems Biology, Center for Biotechnology, Bielefeld University, Bielefeld, Germany
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A Ferredoxin- and F420H2-Dependent, Electron-Bifurcating, Heterodisulfide Reductase with Homologs in the Domains Bacteria and Archaea. mBio 2017; 8:mBio.02285-16. [PMID: 28174314 PMCID: PMC5296606 DOI: 10.1128/mbio.02285-16] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Heterodisulfide reductases (Hdr) of the HdrABC class are ancient enzymes and a component of the anaerobic core belonging to the prokaryotic common ancestor. The ancient origin is consistent with the widespread occurrence of genes encoding putative HdrABC homologs in metabolically diverse prokaryotes predicting diverse physiological functions; however, only one HdrABC has been characterized and that was from a narrow metabolic group of obligate CO2-reducing methanogenic anaerobes (methanogens) from the domain Archaea. Here we report the biochemical characterization of an HdrABC homolog (HdrA2B2C2) from the acetate-utilizing methanogen Methanosarcina acetivorans with unusual properties structurally and functionally distinct from the only other HdrABC characterized. Homologs of the HdrA2B2C2 archetype are present in phylogenetically and metabolically diverse species from the domains Bacteria and Archaea. The expression of the individual HdrA2, HdrB2, and HdrB2C2 enzymes in Escherichia coli, and reconstitution of an active HdrA2B2C2 complex, revealed an intersubunit electron transport pathway dependent on ferredoxin or coenzyme F420 (F420H2) as an electron donor. Remarkably, HdrA2B2C2 couples the previously unknown endergonic oxidation of F420H2 and reduction of ferredoxin with the exergonic oxidation of F420H2 and reduction of the heterodisulfide of coenzyme M and coenzyme B (CoMS-SCoB). The unique electron bifurcation predicts a role for HdrA2B2C2 in Fe(III)-dependent anaerobic methane oxidation (ANME) by M. acetivorans and uncultured species from ANME environments. HdrA2B2C2, ubiquitous in acetotrophic methanogens, was shown to participate in electron transfer during acetotrophic growth of M. acetivorans and proposed to be essential for growth in the environment when acetate is limiting. Discovery of the archetype HdrA2B2C2 heterodisulfide reductase with categorically unique properties extends the understanding of this ancient family beyond CO2-reducing methanogens to include diverse prokaryotes from the domains Bacteria and Archaea. The unprecedented coenzyme F420-dependent electron bifurcation, an emerging fundamental principle of energy conservation, predicts a role for HdrA2B2C2 in diverse metabolisms, including anaerobic CH4-oxidizing pathways. The results document an electron transport role for HdrA2B2C2 in acetate-utilizing methanogens responsible for at least two-thirds of the methane produced in Earth’s biosphere. The previously unavailable heterologous production of individual subunits and the reconstitution of HdrA2B2C2 with activity have provided an understanding of intersubunit electron transfer in the HdrABC class and a platform for investigating the principles of electron bifurcation.
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Dörries M, Wöhlbrand L, Kube M, Reinhardt R, Rabus R. Genome and catabolic subproteomes of the marine, nutritionally versatile, sulfate-reducing bacterium Desulfococcus multivorans DSM 2059. BMC Genomics 2016; 17:918. [PMID: 27846794 PMCID: PMC5109826 DOI: 10.1186/s12864-016-3236-7] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2016] [Accepted: 11/01/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Sulfate-reducing bacteria (SRB) are key players of the carbon- and sulfur-cycles in the sediments of the world's oceans. Habitat relevant SRBs are often members of the Desulfosarcina-Desulfococcus clade belonging to the deltaproteobacterial family of Desulfobacteraceae. Despite this environmental recognition, their molecular (genome-based) physiology and their potential to contribute to organic carbon mineralization as well as to adapt to changing environmental conditions have been scarcely investigated. A metabolically versatile representative of this family is Desulfococcus multivorans that is able to completely oxidize (to CO2) a variety of organic acids, including fatty acids up to C14, as well as aromatic compounds. RESULTS In this study the complete 4.46 Mbp and manually annotated genome of metabolically versatile Desulfococcus multivorans DSM 2059 is presented with particular emphasis on a proteomics-driven metabolic reconstruction. Proteomic profiling covered 17 substrate adaptation conditions (6 aromatic and 11 aliphatic compounds) and comprised 2D DIGE, shotgun proteomics and analysis of the membrane protein-enriched fractions. This comprehensive proteogenomic dataset allowed for reconstructing a metabolic network of degradation pathways and energy metabolism that consists of 170 proteins (154 detected; ~91 % coverage). Peripheral degradation routes feed via central benzoyl-CoA, (modified) β-oxidation or methylmalonyl-CoA pathways into the Wood-Ljungdahl pathway for complete oxidation of acetyl-CoA to CO2. Dissimilatory sulfate reduction is fueled by a complex electron transfer network composed of cytoplasmic components (e.g., electron transfer flavoproteins) and diverse membrane redox complexes (Dsr, Qmo, Hmc, Tmc, Qrc, Nuo and Rnf). Overall, a high degree of substrate-specific formation of catabolic enzymes was observed, while most complexes involved in electron transfer appeared to be constitutively formed. CONCLUSIONS A highly dynamic genome structure in combination with substrate-specifically formed catabolic subproteomes and a constitutive subproteome for energy metabolism and electron transfer appears to be a common trait of Desulfobacteraceae members.
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Affiliation(s)
- Marvin Dörries
- General and Molecular Microbiology, Institute for Chemistry and Biology of the Marine Environment (ICBM), Carl von Ossietzky University Oldenburg, Oldenburg, Germany
| | - Lars Wöhlbrand
- General and Molecular Microbiology, Institute for Chemistry and Biology of the Marine Environment (ICBM), Carl von Ossietzky University Oldenburg, Oldenburg, Germany
| | - Michael Kube
- Institute of Forest Genetics, Johann Heinrich von Thünen Institute, Waldsieversdorf, Germany
| | | | - Ralf Rabus
- General and Molecular Microbiology, Institute for Chemistry and Biology of the Marine Environment (ICBM), Carl von Ossietzky University Oldenburg, Oldenburg, Germany
- Max Planck Institute for Marine Microbiology, Bremen, Germany
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75
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James KL, Ríos-Hernández LA, Wofford NQ, Mouttaki H, Sieber JR, Sheik CS, Nguyen HH, Yang Y, Xie Y, Erde J, Rohlin L, Karr EA, Loo JA, Ogorzalek Loo RR, Hurst GB, Gunsalus RP, Szweda LI, McInerney MJ. Pyrophosphate-Dependent ATP Formation from Acetyl Coenzyme A in Syntrophus aciditrophicus, a New Twist on ATP Formation. mBio 2016; 7:e01208-16. [PMID: 27531911 PMCID: PMC4992975 DOI: 10.1128/mbio.01208-16] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Accepted: 07/12/2016] [Indexed: 11/29/2022] Open
Abstract
UNLABELLED Syntrophus aciditrophicus is a model syntrophic bacterium that degrades key intermediates in anaerobic decomposition, such as benzoate, cyclohexane-1-carboxylate, and certain fatty acids, to acetate when grown with hydrogen-/formate-consuming microorganisms. ATP formation coupled to acetate production is the main source for energy conservation by S. aciditrophicus However, the absence of homologs for phosphate acetyltransferase and acetate kinase in the genome of S. aciditrophicus leaves it unclear as to how ATP is formed, as most fermentative bacteria rely on these two enzymes to synthesize ATP from acetyl coenzyme A (CoA) and phosphate. Here, we combine transcriptomic, proteomic, metabolite, and enzymatic approaches to show that S. aciditrophicus uses AMP-forming, acetyl-CoA synthetase (Acs1) for ATP synthesis from acetyl-CoA. acs1 mRNA and Acs1 were abundant in transcriptomes and proteomes, respectively, of S. aciditrophicus grown in pure culture and coculture. Cell extracts of S. aciditrophicus had low or undetectable acetate kinase and phosphate acetyltransferase activities but had high acetyl-CoA synthetase activity under all growth conditions tested. Both Acs1 purified from S. aciditrophicus and recombinantly produced Acs1 catalyzed ATP and acetate formation from acetyl-CoA, AMP, and pyrophosphate. High pyrophosphate levels and a high AMP-to-ATP ratio (5.9 ± 1.4) in S. aciditrophicus cells support the operation of Acs1 in the acetate-forming direction. Thus, S. aciditrophicus has a unique approach to conserve energy involving pyrophosphate, AMP, acetyl-CoA, and an AMP-forming, acetyl-CoA synthetase. IMPORTANCE Bacteria use two enzymes, phosphate acetyltransferase and acetate kinase, to make ATP from acetyl-CoA, while acetate-forming archaea use a single enzyme, an ADP-forming, acetyl-CoA synthetase, to synthesize ATP and acetate from acetyl-CoA. Syntrophus aciditrophicus apparently relies on a different approach to conserve energy during acetyl-CoA metabolism, as its genome does not have homologs to the genes for phosphate acetyltransferase and acetate kinase. Here, we show that S. aciditrophicus uses an alternative approach, an AMP-forming, acetyl-CoA synthetase, to make ATP from acetyl-CoA. AMP-forming, acetyl-CoA synthetases were previously thought to function only in the activation of acetate to acetyl-CoA.
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Affiliation(s)
- Kimberly L James
- Department of Microbiology and Plant Biology, University of Oklahoma, Norman, Oklahoma, USA
| | - Luis A Ríos-Hernández
- Department of Microbiology and Plant Biology, University of Oklahoma, Norman, Oklahoma, USA
| | - Neil Q Wofford
- Department of Microbiology and Plant Biology, University of Oklahoma, Norman, Oklahoma, USA
| | - Housna Mouttaki
- Department of Microbiology and Plant Biology, University of Oklahoma, Norman, Oklahoma, USA
| | - Jessica R Sieber
- Department of Microbiology and Plant Biology, University of Oklahoma, Norman, Oklahoma, USA
| | - Cody S Sheik
- Department of Microbiology and Plant Biology, University of Oklahoma, Norman, Oklahoma, USA
| | - Hong H Nguyen
- Department of Biological Chemistry, University of California Los Angeles, Los Angeles, California, USA
| | - Yanan Yang
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, California, USA
| | - Yongming Xie
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, California, USA
| | - Jonathan Erde
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, California, USA
| | - Lars Rohlin
- Department of Microbiology, Immunology and Molecular Genetics, University of California Los Angeles, Los Angeles, California, USA
| | - Elizabeth A Karr
- Department of Microbiology and Plant Biology, University of Oklahoma, Norman, Oklahoma, USA
| | - Joseph A Loo
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, California, USA Department of Biological Chemistry, University of California Los Angeles, Los Angeles, California, USA
| | - Rachel R Ogorzalek Loo
- Department of Biological Chemistry, University of California Los Angeles, Los Angeles, California, USA
| | - Gregory B Hurst
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
| | - Robert P Gunsalus
- Department of Microbiology, Immunology and Molecular Genetics, University of California Los Angeles, Los Angeles, California, USA
| | - Luke I Szweda
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma, USA
| | - Michael J McInerney
- Department of Microbiology and Plant Biology, University of Oklahoma, Norman, Oklahoma, USA
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76
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Vanwonterghem I, Jensen PD, Rabaey K, Tyson GW. Genome-centric resolution of microbial diversity, metabolism and interactions in anaerobic digestion. Environ Microbiol 2016; 18:3144-58. [DOI: 10.1111/1462-2920.13382] [Citation(s) in RCA: 92] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Accepted: 03/17/2016] [Indexed: 12/16/2022]
Affiliation(s)
- Inka Vanwonterghem
- Advanced Water Management Centre (AWMC), The University of Queensland; QLD 4072 St Lucia Australia
- Australian Centre for Ecogenomics (ACE); The University of Queensland; QLD 4072 St Lucia Australia
| | - Paul D. Jensen
- Advanced Water Management Centre (AWMC), The University of Queensland; QLD 4072 St Lucia Australia
| | - Korneel Rabaey
- Advanced Water Management Centre (AWMC), The University of Queensland; QLD 4072 St Lucia Australia
- Centre for Microbial Ecology and Technology (CMET); Ghent University; Coupure Links 653 Ghent 9000 Belgium
| | - Gene W. Tyson
- Advanced Water Management Centre (AWMC), The University of Queensland; QLD 4072 St Lucia Australia
- Australian Centre for Ecogenomics (ACE); The University of Queensland; QLD 4072 St Lucia Australia
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Narihiro T, Nobu MK, Tamaki H, Kamagata Y, Sekiguchi Y, Liu WT. Comparative Genomics of Syntrophic Branched-Chain Fatty Acid Degrading Bacteria. Microbes Environ 2016; 31:288-92. [PMID: 27431485 PMCID: PMC5017805 DOI: 10.1264/jsme2.me16057] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The syntrophic degradation of branched-chain fatty acids (BCFAs) such as 2-methylbutyrate and isobutyrate is an essential step in the production of methane from proteins/amino acids in anaerobic ecosystems. While a few syntrophic BCFA-degrading bacteria have been isolated, their metabolic pathways in BCFA and short-chain fatty acid (SCFA) degradation as well as energy conservation systems remain unclear. In an attempt to identify these pathways, we herein performed comparative genomics of three syntrophic bacteria: 2-methylbutyrate-degrading “Syntrophomonas wolfei subsp. methylbutyratica” strain JCM 14075T (=4J5T), isobutyrate-degrading Syntrophothermus lipocalidus strain TGB-C1T, and non-BCFA-metabolizing S. wolfei subsp. wolfei strain GöttingenT. We demonstrated that 4J5 and TGB-C1 both encode multiple genes/gene clusters involved in β-oxidation, as observed in the Göttingen genome, which has multiple copies of genes associated with butyrate degradation. The 4J5 genome possesses phylogenetically distinct β-oxidation genes, which may be involved in 2-methylbutyrate degradation. In addition, these Syntrophomonadaceae strains harbor various hydrogen/formate generation systems (i.e., electron-bifurcating hydrogenase, formate dehydrogenase, and membrane-bound hydrogenase) and energy-conserving electron transport systems, including electron transfer flavoprotein (ETF)-linked acyl-CoA dehydrogenase, ETF-linked iron-sulfur binding reductase, ETF dehydrogenase (FixABCX), and flavin oxidoreductase-heterodisulfide reductase (Flox-Hdr). Unexpectedly, the TGB-C1 genome encodes a nitrogenase complex, which may function as an alternative H2 generation mechanism. These results suggest that the BCFA-degrading syntrophic strains 4J5 and TGB-C1 possess specific β-oxidation-related enzymes for BCFA oxidation as well as appropriate energy conservation systems to perform thermodynamically unfavorable syntrophic metabolism.
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Affiliation(s)
- Takashi Narihiro
- Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST)
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Wawrik B, Marks CR, Davidova IA, McInerney MJ, Pruitt S, Duncan KE, Suflita JM, Callaghan AV. Methanogenic paraffin degradation proceeds via alkane addition to fumarate by 'Smithella' spp. mediated by a syntrophic coupling with hydrogenotrophic methanogens. Environ Microbiol 2016; 18:2604-19. [PMID: 27198766 DOI: 10.1111/1462-2920.13374] [Citation(s) in RCA: 65] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Anaerobic microbial biodegradation of recalcitrant, water-insoluble substrates, such as paraffins, presents unique metabolic challenges. To elucidate this process, a methanogenic consortium capable of mineralizing long-chain n-paraffins (C28 -C50 ) was enriched from San Diego Bay sediment. Analysis of 16S rRNA genes indicated the dominance of Syntrophobacterales (43%) and Methanomicrobiales (26%). Metagenomic sequencing allowed draft genome assembly of dominant uncultivated community members belonging to the bacterial genus Smithella and the archaeal genera Methanoculleus and Methanosaeta. Five contigs encoding homologs of the catalytic subunit of alkylsuccinate synthase (assA) were detected. Additionally, mRNA transcripts for these genes, including a homolog binned within the 'Smithella' sp. SDB genome scaffold, were detected via RT-PCR, implying that paraffins are activated via 'fumarate addition'. Metabolic reconstruction and comparison with genome scaffolds of uncultivated n-alkane degrading 'Smithella' spp. are consistent with the hypothesis that syntrophically growing 'Smithella' spp. may achieve reverse electron transfer by coupling the reoxidation of ETFred to a membrane-bound FeS oxidoreductase functioning as an ETF:menaquinone oxidoreductase. Subsequent electron transfer could proceed via a periplasmic formate dehydrogenase and/or hydrogenase, allowing energetic coupling to hydrogenotrophic methanogens such as Methanoculleus. Ultimately, these data provide fundamental insight into the energy conservation mechanisms that dictate interspecies interactions salient to methanogenic alkane mineralization.
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Affiliation(s)
- Boris Wawrik
- Department of Microbiology and Plant Biology, University of Oklahoma, George Lynn Cross Hall, 770 Van Vleet Oval, Norman, OK, 73019, 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, University of Oklahoma, 100 East Boyd Street, Norman, OK, 73019, USA
| | - 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, University of Oklahoma, 100 East Boyd Street, Norman, OK, 73019, USA
| | - Michael J McInerney
- Department of Microbiology and Plant Biology, University of Oklahoma, George Lynn Cross Hall, 770 Van Vleet Oval, Norman, OK, 73019, USA
| | - Shane Pruitt
- Department of Microbiology and Plant Biology, University of Oklahoma, George Lynn Cross Hall, 770 Van Vleet Oval, Norman, OK, 73019, USA.,Development and Alumni Relations, Oglethorpe University, 4484 Peachtree Road, NE, Atlanta, GA, 30319, USA
| | - Kathleen E 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, University of Oklahoma, 100 East Boyd Street, Norman, OK, 73019, 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, University of Oklahoma, 100 East Boyd Street, 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
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Movahedi NS, Embree M, Nagarajan H, Zengler K, Chitsaz H. Efficient Synergistic Single-Cell Genome Assembly. Front Bioeng Biotechnol 2016; 4:42. [PMID: 27243002 PMCID: PMC4876485 DOI: 10.3389/fbioe.2016.00042] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2016] [Accepted: 05/06/2016] [Indexed: 11/13/2022] Open
Abstract
As the vast majority of all microbes are unculturable, single-cell sequencing has become a significant method to gain insight into microbial physiology. Single-cell sequencing methods, currently powered by multiple displacement genome amplification (MDA), have passed important milestones such as finishing and closing the genome of a prokaryote. However, the quality and reliability of genome assemblies from single cells are still unsatisfactory due to uneven coverage depth and the absence of scattered chunks of the genome in the final collection of reads caused by MDA bias. In this work, our new algorithm Hybrid De novo Assembler (HyDA) demonstrates the power of coassembly of multiple single-cell genomic data sets through significant improvement of the assembly quality in terms of predicted functional elements and length statistics. Coassemblies contain significantly more base pairs and protein coding genes, cover more subsystems, and consist of longer contigs compared to individual assemblies by the same algorithm as well as state-of-the-art single-cell assemblers SPAdes and IDBA-UD. Hybrid De novo Assembler (HyDA) is also able to avoid chimeric assemblies by detecting and separating shared and exclusive pieces of sequence for input data sets. By replacing one deep single-cell sequencing experiment with a few single-cell sequencing experiments of lower depth, the coassembly method can hedge against the risk of failure and loss of the sample, without significantly increasing sequencing cost. Application of the single-cell coassembler HyDA to the study of three uncultured members of an alkane-degrading methanogenic community validated the usefulness of the coassembly concept. HyDA is open source and publicly available at http://chitsazlab.org/software.html, and the raw reads are available at http://chitsazlab.org/research.html.
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Affiliation(s)
- Narjes S Movahedi
- Department of Computer Science, Wayne State University , Detroit, MI , USA
| | - Mallory Embree
- Department of Bioengineering, University of California San Diego , San Diego, CA , USA
| | - Harish Nagarajan
- Department of Bioengineering, University of California San Diego , San Diego, CA , USA
| | - Karsten Zengler
- Department of Bioengineering, University of California San Diego , San Diego, CA , USA
| | - Hamidreza Chitsaz
- Department of Computer Science, Colorado State University , Fort Collins, CO , USA
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80
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Krukenberg V, Harding K, Richter M, Glöckner FO, Gruber-Vodicka HR, Adam B, Berg JS, Knittel K, Tegetmeyer HE, Boetius A, Wegener G. CandidatusDesulfofervidus auxilii, a hydrogenotrophic sulfate-reducing bacterium involved in the thermophilic anaerobic oxidation of methane. Environ Microbiol 2016; 18:3073-91. [DOI: 10.1111/1462-2920.13283] [Citation(s) in RCA: 90] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2015] [Revised: 02/23/2016] [Accepted: 02/24/2016] [Indexed: 01/20/2023]
Affiliation(s)
| | - Katie Harding
- Max Planck Institute for Marine Microbiology; Bremen Germany
| | - Michael Richter
- Max Planck Institute for Marine Microbiology; Bremen Germany
| | - Frank Oliver Glöckner
- Max Planck Institute for Marine Microbiology; Bremen Germany
- Jacobs University Bremen gGmbH; Bremen Germany
| | | | - Birgit Adam
- Max Planck Institute for Marine Microbiology; Bremen Germany
| | - Jasmine S. Berg
- Max Planck Institute for Marine Microbiology; Bremen Germany
| | - Katrin Knittel
- Max Planck Institute for Marine Microbiology; Bremen Germany
| | - Halina E. Tegetmeyer
- Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research; Bremerhaven Germany
- Center for Biotechnology, Bielefeld University; Bielefeld Germany
| | - Antje Boetius
- Max Planck Institute for Marine Microbiology; Bremen Germany
- Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research; Bremerhaven Germany
- MARUM, Center for Marine Environmental Sciences, University Bremen; Bremen Germany
| | - Gunter Wegener
- Max Planck Institute for Marine Microbiology; Bremen Germany
- MARUM, Center for Marine Environmental Sciences, University Bremen; Bremen Germany
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81
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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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82
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Schmidt O, Hink L, Horn MA, Drake HL. Peat: home to novel syntrophic species that feed acetate- and hydrogen-scavenging methanogens. ISME JOURNAL 2016; 10:1954-66. [PMID: 26771931 DOI: 10.1038/ismej.2015.256] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2015] [Revised: 11/25/2015] [Accepted: 12/07/2015] [Indexed: 11/09/2022]
Abstract
Syntrophic bacteria drive the anaerobic degradation of certain fermentation products (e.g., butyrate, ethanol, propionate) to intermediary substrates (e.g., H2, formate, acetate) that yield methane at the ecosystem level. However, little is known about the in situ activities and identities of these syntrophs in peatlands, ecosystems that produce significant quantities of methane. The consumption of butyrate, ethanol or propionate by anoxic peat slurries at 5 and 15 °C yielded methane and CO2 as the sole accumulating products, indicating that the intermediates H2, formate and acetate were scavenged effectively by syntrophic methanogenic consortia. 16S rRNA stable isotope probing identified novel species/strains of Pelobacter and Syntrophomonas that syntrophically oxidized ethanol and butyrate, respectively. Propionate was syntrophically oxidized by novel species of Syntrophobacter and Smithella, genera that use different propionate-oxidizing pathways. Taxa not known for a syntrophic metabolism may have been involved in the oxidation of butyrate (Telmatospirillum-related) and propionate (unclassified Bacteroidetes and unclassified Fibrobacteres). Gibbs free energies (ΔGs) for syntrophic oxidations of ethanol and butyrate were more favorable than ΔGs for syntrophic oxidation of propionate. As a result of the thermodynamic constraints, acetate transiently accumulated in ethanol and butyrate treatments but not in propionate treatments. Aceticlastic methanogens (Methanosarcina, Methanosaeta) appeared to outnumber hydrogenotrophic methanogens (Methanocella, Methanoregula), reinforcing the likely importance of aceticlastic methanogenesis to the overall production of methane. ΔGs for acetogenesis from H2 to CO2 approximated to -20 kJ mol(-1) when acetate concentrations were low, indicating that acetogens may have contributed to the flow of carbon and reductant towards methane.
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Affiliation(s)
- Oliver Schmidt
- Department of Ecological Microbiology, University of Bayreuth, Bayreuth, Germany
| | - Linda Hink
- Department of Ecological Microbiology, University of Bayreuth, Bayreuth, Germany
| | - Marcus A Horn
- Department of Ecological Microbiology, University of Bayreuth, Bayreuth, Germany
| | - Harold L Drake
- Department of Ecological Microbiology, University of Bayreuth, Bayreuth, Germany
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83
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Comparison of bacterial and archaeal communities in depth-resolved zones in an LNAPL body. Appl Microbiol Biotechnol 2015; 100:3347-60. [PMID: 26691516 DOI: 10.1007/s00253-015-7106-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Revised: 10/13/2015] [Accepted: 10/15/2015] [Indexed: 10/22/2022]
Abstract
Advances in our understanding of the microbial ecology at sites impacted by light non-aqueous phase liquids (LNAPLs) are needed to drive development of optimized bioremediation technologies, support longevity models, and develop culture-independent molecular tools. In this study, depth-resolved characterization of geochemical parameters and microbial communities was conducted for a shallow hydrocarbon-impacted aquifer. Four distinct zones were identified based on microbial community structure and geochemical data: (i) an aerobic, low-contaminant mass zone at the top of the vadose zone; (ii) a moderate to high-contaminant mass, low-oxygen to anaerobic transition zone in the middle of the vadose zone; (iii) an anaerobic, high-contaminant mass zone spanning the bottom of the vadose zone and saturated zone; and (iv) an anaerobic, low-contaminant mass zone below the LNAPL body. Evidence suggested that hydrocarbon degradation is mediated by syntrophic fermenters and methanogens in zone III. Upward flux of methane likely contributes to promoting anaerobic conditions in zone II by limiting downward flux of oxygen as methane and oxygen fronts converge at the top of this zone. Observed sulfate gradients and microbial communities suggested that sulfate reduction and methanogenesis both contribute to hydrocarbon degradation in zone IV. Pyrosequencing revealed that Syntrophus- and Methanosaeta-related species dominate bacterial and archaeal communities, respectively, in the LNAPL body below the water table. Observed phylotypes were linked with in situ anaerobic hydrocarbon degradation in LNAPL-impacted soils.
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84
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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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85
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Methanogenic degradation of lignin-derived monoaromatic compounds by microbial enrichments from rice paddy field soil. Sci Rep 2015; 5:14295. [PMID: 26399549 PMCID: PMC4585845 DOI: 10.1038/srep14295] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2015] [Accepted: 08/24/2015] [Indexed: 11/08/2022] Open
Abstract
Anaerobic degradation of lignin-derived aromatics is an important metabolism for carbon and nutrient cycles in soil environments. Although there are some studies on degradation of lignin-derived aromatics by nitrate- and sulfate-reducing bacteria, knowledge on their degradation under methanogenic conditions are quite limited. In this study, methanogenic microbial communities were enriched from rice paddy field soil with lignin-derived methoxylated monoaromatics (vanillate and syringate) and their degradation intermediates (protocatechuate, catechol, and gallate) as the sole carbon and energy sources. Archaeal community analysis disclosed that both aceticlastic (Methanosarcina sp.) and hydrogenotrophic (Methanoculleus sp. and Methanocella sp.) methanogens dominated in all of the enrichments. Bacterial community analysis revealed the dominance of acetogenic bacteria (Sporomusa spp.) only in the enrichments on the methoxylated aromatics, suggesting that Sporomusa spp. initially convert vanillate and syringate into protocatechuate and gallate, respectively, with acetogenesis via O-demethylation. As the putative ring-cleavage microbes, bacteria within the phylum Firmicutes were dominantly detected from all of the enrichments, while the dominant phylotypes were not identical between enrichments on vanillate/protocatechuate/catechol (family Peptococcaceae bacteria) and on syringate/gallate (family Ruminococcaceae bacteria). This study demonstrates the importance of cooperation among acetogens, ring-cleaving fermenters/syntrophs and aceticlastic/hydrogenotrophic methanogens for degradation of lignin-derived aromatics under methanogenic conditions.
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86
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Jia N, Du J, Ding MZ, Gao F, Yuan YJ. Genome Sequence of Bacillus endophyticus and Analysis of Its Companion Mechanism in the Ketogulonigenium vulgare-Bacillus Strain Consortium. PLoS One 2015; 10:e0135104. [PMID: 26248285 PMCID: PMC4527741 DOI: 10.1371/journal.pone.0135104] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2015] [Accepted: 07/16/2015] [Indexed: 11/19/2022] Open
Abstract
Bacillus strains have been widely used as the companion strain of Ketogulonigenium vulgare in the process of vitamin C fermentation. Different Bacillus strains generate different effects on the growth of K. vulgare and ultimately influence the productivity. First, we identified that Bacillus endophyticus Hbe603 was an appropriate strain to cooperate with K. vulgare and the product conversion rate exceeded 90% in industrial vitamin C fermentation. Here, we report the genome sequencing of the B. endophyticus Hbe603 industrial companion strain and speculate its possible advantage in the consortium. The circular chromosome of B. endophyticus Hbe603 has a size of 4.87 Mb with GC content of 36.64% and has the highest similarity with that of Bacillus megaterium among all the bacteria with complete genomes. By comparing the distribution of COGs with that of Bacillus thuringiensis, Bacillus cereus and B. megaterium, B. endophyticus has less genes related to cell envelope biogenesis and signal transduction mechanisms, and more genes related to carbohydrate transport and metabolism, energy production and conversion, as well as lipid transport and metabolism. Genome-based functional studies revealed the specific capability of B. endophyticus in sporulation, transcription regulation, environmental resistance, membrane transportation, extracellular proteins and nutrients synthesis, which would be beneficial for K. vulgare. In particular, B. endophyticus lacks the Rap-Phr signal cascade system and, in part, spore coat related proteins. In addition, it has specific pathways for vitamin B12 synthesis and sorbitol metabolism. The genome analysis of the industrial B. endophyticus will help us understand its cooperative mechanism in the K. vulgare-Bacillus strain consortium to improve the fermentation of vitamin C.
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Affiliation(s)
- Nan Jia
- Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, PR China
- SynBio Research Platform, Collaborative Innovation Centre of Chemical Science and Engineering (Tianjin), School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, PR China
| | - Jin Du
- Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, PR China
- SynBio Research Platform, Collaborative Innovation Centre of Chemical Science and Engineering (Tianjin), School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, PR China
| | - Ming-Zhu Ding
- Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, PR China
- SynBio Research Platform, Collaborative Innovation Centre of Chemical Science and Engineering (Tianjin), School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, PR China
| | - Feng Gao
- Department of Physics, Tianjin University, Tianjin, 300072, PR China
- * E-mail: (FG); (YJY)
| | - Ying-Jin Yuan
- Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, PR China
- SynBio Research Platform, Collaborative Innovation Centre of Chemical Science and Engineering (Tianjin), School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, PR China
- * E-mail: (FG); (YJY)
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A Post-Genomic View of the Ecophysiology, Catabolism and Biotechnological Relevance of Sulphate-Reducing Prokaryotes. Adv Microb Physiol 2015. [PMID: 26210106 DOI: 10.1016/bs.ampbs.2015.05.002] [Citation(s) in RCA: 174] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Dissimilatory sulphate reduction is the unifying and defining trait of sulphate-reducing prokaryotes (SRP). In their predominant habitats, sulphate-rich marine sediments, SRP have long been recognized to be major players in the carbon and sulphur cycles. Other, more recently appreciated, ecophysiological roles include activity in the deep biosphere, symbiotic relations, syntrophic associations, human microbiome/health and long-distance electron transfer. SRP include a high diversity of organisms, with large nutritional versatility and broad metabolic capacities, including anaerobic degradation of aromatic compounds and hydrocarbons. Elucidation of novel catabolic capacities as well as progress in the understanding of metabolic and regulatory networks, energy metabolism, evolutionary processes and adaptation to changing environmental conditions has greatly benefited from genomics, functional OMICS approaches and advances in genetic accessibility and biochemical studies. Important biotechnological roles of SRP range from (i) wastewater and off gas treatment, (ii) bioremediation of metals and hydrocarbons and (iii) bioelectrochemistry, to undesired impacts such as (iv) souring in oil reservoirs and other environments, and (v) corrosion of iron and concrete. Here we review recent advances in our understanding of SRPs focusing mainly on works published after 2000. The wealth of publications in this period, covering many diverse areas, is a testimony to the large environmental, biogeochemical and technological relevance of these organisms and how much the field has progressed in these years, although many important questions and applications remain to be explored.
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Phylogenomic analysis and predicted physiological role of the proton-translocating NADH:quinone oxidoreductase (complex I) across bacteria. mBio 2015; 6:mBio.00389-15. [PMID: 25873378 PMCID: PMC4453560 DOI: 10.1128/mbio.00389-15] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED The proton-translocating NADH:quinone oxidoreductase (complex I) is a multisubunit integral membrane enzyme found in the respiratory chains of both bacteria and eukaryotic organelles. Although much research has focused on the enzyme's central role in the mitochondrial respiratory chain, comparatively little is known about its role in the diverse energetic lifestyles of different bacteria. Here, we used a phylogenomic approach to better understand the distribution of complex I across bacteria, the evolution of this enzyme, and its potential roles in shaping the physiology of different bacterial groups. By surveying 970 representative bacterial genomes, we predict complex I to be present in ~50% of bacteria. While this includes bacteria with a wide range of energetic schemes, the presence of complex I is associated with specific lifestyles, including aerobic respiration and specific types of phototrophy (bacteria with only a type II reaction center). A phylogeny of bacterial complex I revealed five main clades of enzymes whose evolution is largely congruent with the evolution of the bacterial groups that encode complex I. A notable exception includes the gammaproteobacteria, whose members encode one of two distantly related complex I enzymes predicted to participate in different types of respiratory chains (aerobic versus anaerobic). Comparative genomic analyses suggest a broad role for complex I in reoxidizing NADH produced from various catabolic reactions, including the tricarboxylic acid (TCA) cycle and fatty acid beta-oxidation. Together, these findings suggest diverse roles for complex I across bacteria and highlight the importance of this enzyme in shaping diverse physiologies across the bacterial domain. IMPORTANCE Living systems use conserved energy currencies, including a proton motive force (PMF), NADH, and ATP. The respiratory chain enzyme, complex I, connects these energy currencies by using NADH produced during nutrient breakdown to generate a PMF, which is subsequently used for ATP synthesis. Our goal is to better understand the role of complex I in bacteria, whose energetic diversity allows us to view its function in a range of biological contexts. We analyzed sequenced bacterial genomes to predict the presence, evolution, and function of complex I in bacteria. We identified five main classes of bacterial complex I and predict that different classes participate in different types of respiratory chains (aerobic and anaerobic). We also predict that complex I helps maintain a cellular redox state by reoxidizing NADH produced from central metabolism. Our findings suggest diverse roles for complex I in bacterial physiology, highlighting the need for future laboratory-based studies.
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89
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Sieber JR, Crable BR, Sheik CS, Hurst GB, Rohlin L, Gunsalus RP, McInerney MJ. Proteomic analysis reveals metabolic and regulatory systems involved in the syntrophic and axenic lifestyle of Syntrophomonas wolfei. Front Microbiol 2015; 6:115. [PMID: 25717324 PMCID: PMC4324140 DOI: 10.3389/fmicb.2015.00115] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2014] [Accepted: 01/29/2015] [Indexed: 11/13/2022] Open
Abstract
Microbial syntrophy is a vital metabolic interaction necessary for the complete oxidation of organic biomass to methane in all-anaerobic ecosystems. However, this process is thermodynamically constrained and represents an ecosystem-level metabolic bottleneck. To gain insight into the physiology of this process, a shotgun proteomics approach was used to quantify the protein landscape of the model syntrophic metabolizer, Syntrophomonas wolfei, grown axenically and syntrophically with Methanospirillum hungatei. Remarkably, the abundance of most proteins as represented by normalized spectral abundance factor (NSAF) value changed very little between the pure and coculture growth conditions. Among the most abundant proteins detected were GroEL and GroES chaperonins, a small heat shock protein, and proteins involved in electron transfer, beta-oxidation, and ATP synthesis. Several putative energy conservation enzyme systems that utilize NADH and ferredoxin were present. The abundance of an EtfAB2 and the membrane-bound iron-sulfur oxidoreductase (Swol_0698 gene product) delineated a potential conduit for electron transfer between acyl-CoA dehydrogenases and membrane redox carriers. Proteins detected only when S. wolfei was grown with M. hungatei included a zinc-dependent dehydrogenase with a GroES domain, whose gene is present in genomes in many organisms capable of syntrophy, and transcriptional regulators responsive to environmental stimuli or the physiological status of the cell. The proteomic analysis revealed an emphasis on macromolecular stability and energy metabolism by S. wolfei and presence of regulatory mechanisms responsive to external stimuli and cellular physiological status.
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Affiliation(s)
- Jessica R. Sieber
- Department of Botany and Microbiology, University of OklahomaNorman, OK, USA
| | - Bryan R. Crable
- Department of Botany and Microbiology, University of OklahomaNorman, OK, USA
| | - Cody S. Sheik
- Department of Geological Sciences, University of MichiganAnn Arbor, MI, USA
| | - Gregory B. Hurst
- Chemical Sciences Division, Oak Ridge National LaboratoryOak Ridge, TN, USA
| | - Lars Rohlin
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los AngelesLos Angeles, CA, USA
| | - Robert P. Gunsalus
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los AngelesLos Angeles, CA, USA
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Syntrophic growth of Desulfovibrio alaskensis requires genes for H2 and formate metabolism as well as those for flagellum and biofilm formation. Appl Environ Microbiol 2015; 81:2339-48. [PMID: 25616787 DOI: 10.1128/aem.03358-14] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In anaerobic environments, mutually beneficial metabolic interactions between microorganisms (syntrophy) are essential for oxidation of organic matter to carbon dioxide and methane. Syntrophic interactions typically involve a microorganism degrading an organic compound to primary fermentation by-products and sources of electrons (i.e., formate, hydrogen, or nanowires) and a partner producing methane or respiring the electrons via alternative electron accepting processes. Using a transposon gene mutant library of the sulfate-reducing Desulfovibrio alaskensis G20, we screened for mutants incapable of serving as the electron-accepting partner of the butyrate-oxidizing bacterium, Syntrophomonas wolfei. A total of 17 gene mutants of D. alaskensis were identified as incapable of serving as the electron-accepting partner. The genes identified predominantly fell into three categories: membrane surface assembly, flagellum-pilus synthesis, and energy metabolism. Among these genes required to serve as the electron-accepting partner, the glycosyltransferase, pilus assembly protein (tadC), and flagellar biosynthesis protein showed reduced biofilm formation, suggesting that each of these components is involved in cell-to-cell interactions. Energy metabolism genes encoded proteins primarily involved in H2 uptake and electron cycling, including a rhodanese-containing complex that is phylogenetically conserved among sulfate-reducing Deltaproteobacteria. Utilizing an mRNA sequencing approach, analysis of transcript abundance in wild-type axenic and cocultures confirmed that genes identified as important for serving as the electron-accepting partner were more highly expressed under syntrophic conditions. The results imply that sulfate-reducing microorganisms require flagellar and outer membrane components to effectively couple to their syntrophic partners; furthermore, H2 metabolism is essential for syntrophic growth of D. alaskensis G20.
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91
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Microbial dark matter ecogenomics reveals complex synergistic networks in a methanogenic bioreactor. ISME JOURNAL 2015; 9:1710-22. [PMID: 25615435 DOI: 10.1038/ismej.2014.256] [Citation(s) in RCA: 232] [Impact Index Per Article: 25.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2014] [Revised: 10/20/2014] [Accepted: 11/24/2014] [Indexed: 11/09/2022]
Abstract
Ecogenomic investigation of a methanogenic bioreactor degrading terephthalate (TA) allowed elucidation of complex synergistic networks of uncultivated microorganisms, including those from candidate phyla with no cultivated representatives. Our previous metagenomic investigation proposed that Pelotomaculum and methanogens may interact with uncultivated organisms to degrade TA; however, many members of the community remained unaddressed because of past technological limitations. In further pursuit, this study employed state-of-the-art omics tools to generate draft genomes and transcriptomes for uncultivated organisms spanning 15 phyla and reports the first genomic insight into candidate phyla Atribacteria, Hydrogenedentes and Marinimicrobia in methanogenic environments. Metabolic reconstruction revealed that these organisms perform fermentative, syntrophic and acetogenic catabolism facilitated by energy conservation revolving around H2 metabolism. Several of these organisms could degrade TA catabolism by-products (acetate, butyrate and H2) and syntrophically support Pelotomaculum. Other taxa could scavenge anabolic products (protein and lipids) presumably derived from detrital biomass produced by the TA-degrading community. The protein scavengers expressed complementary metabolic pathways indicating syntrophic and fermentative step-wise protein degradation through amino acids, branched-chain fatty acids and propionate. Thus, the uncultivated organisms may interact to form an intricate syntrophy-supported food web with Pelotomaculum and methanogens to metabolize catabolic by-products and detritus, whereby facilitating holistic TA mineralization to CO2 and CH4.
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92
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Jones CP, Ingram-Smith C. Biochemical and kinetic characterization of the recombinant ADP-forming acetyl coenzyme A synthetase from the amitochondriate protozoan Entamoeba histolytica. EUKARYOTIC CELL 2014; 13:1530-7. [PMID: 25303954 PMCID: PMC4248687 DOI: 10.1128/ec.00192-14] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2014] [Accepted: 10/05/2014] [Indexed: 11/20/2022]
Abstract
Entamoeba histolytica, an amitochondriate protozoan parasite that relies on glycolysis as a key pathway for ATP generation, has developed a unique extended PPi-dependent glycolytic pathway in which ADP-forming acetyl-coenzyme A (CoA) synthetase (ACD; acetate:CoA ligase [ADP-forming]; EC 6.2.1.13) converts acetyl-CoA to acetate to produce additional ATP and recycle CoA. We characterized the recombinant E. histolytica ACD and found that the enzyme is bidirectional, allowing it to potentially play a role in ATP production or in utilization of acetate. In the acetate-forming direction, acetyl-CoA was the preferred substrate and propionyl-CoA was used with lower efficiency. In the acetyl-CoA-forming direction, acetate was the preferred substrate, with a lower efficiency observed with propionate. The enzyme can utilize both ADP/ATP and GDP/GTP in the respective directions of the reaction. ATP and PPi were found to inhibit the acetate-forming direction of the reaction, with 50% inhibitory concentrations of 0.81 ± 0.17 mM (mean ± standard deviation) and 0.75 ± 0.20 mM, respectively, which are both in the range of their physiological concentrations. ATP and PPi displayed mixed inhibition versus each of the three substrates, acetyl-CoA, ADP, and phosphate. This is the first example of regulation of ACD enzymatic activity, and possible roles for this regulation are discussed.
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Affiliation(s)
- Cheryl P Jones
- Eukaryotic Pathogens Innovation Center, Department of Genetics and Biochemistry, Clemson University, Clemson, South Carolina, USA
| | - Cheryl Ingram-Smith
- Eukaryotic Pathogens Innovation Center, Department of Genetics and Biochemistry, Clemson University, Clemson, South Carolina, USA
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93
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Draft Genome Sequences of Three Smithella spp. Obtained from a Methanogenic Alkane-Degrading Culture and Oil Field Produced Water. GENOME ANNOUNCEMENTS 2014; 2:2/5/e01085-14. [PMID: 25342693 PMCID: PMC4208337 DOI: 10.1128/genomea.01085-14] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
Two draft genomes affiliated with Smithella spp. were obtained from a methanogenic alkane-degrading enrichment culture by single-cell sorting and metagenome contig binning, and a third was obtained by single-cell sorting of oil field produced water. Two genomes contained putative assABC genes encoding alkylsuccinate synthase, indicating genetic potential for fumarate activation of alkanes.
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94
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Hillesland KL, Lim S, Flowers JJ, Turkarslan S, Pinel N, Zane GM, Elliott N, Qin Y, Wu L, Baliga NS, Zhou J, Wall JD, Stahl DA. Erosion of functional independence early in the evolution of a microbial mutualism. Proc Natl Acad Sci U S A 2014; 111:14822-7. [PMID: 25267659 PMCID: PMC4205623 DOI: 10.1073/pnas.1407986111] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Many species have evolved to function as specialized mutualists, often to the detriment of their ability to survive independently. However, there are few, if any, well-controlled observations of the evolutionary processes underlying the genesis of new mutualisms. Here, we show that within the first 1,000 generations of initiating independent syntrophic interactions between a sulfate reducer (Desulfovibrio vulgaris) and a hydrogenotrophic methanogen (Methanococcus maripaludis), D. vulgaris frequently lost the capacity to grow by sulfate respiration, thus losing the primary physiological attribute of the genus. The loss of sulfate respiration was a consequence of mutations in one or more of three key genes in the pathway for sulfate respiration, required for sulfate activation (sat) and sulfate reduction to sulfite (apsA or apsB). Because loss-of-function mutations arose rapidly and independently in replicated experiments, and because these mutations were correlated with enhanced growth rate and productivity, gene loss could be attributed to natural selection, even though these mutations should significantly restrict the independence of the evolved D. vulgaris. Together, these data present an empirical demonstration that specialization for a mutualistic interaction can evolve by natural selection shortly after its origin. They also demonstrate that a sulfate-reducing bacterium can readily evolve to become a specialized syntroph, a situation that may have often occurred in nature.
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Affiliation(s)
| | - Sujung Lim
- Biological Sciences, University of Washington Bothell, Bothell, WA 98011
| | | | | | - Nicolas Pinel
- Civil and Environmental Engineering, and Institute for Systems Biology, Seattle, WA 98109-5234
| | - Grant M Zane
- Department of Biochemistry, University of Missouri, Columbia, MO 65211
| | | | - Yujia Qin
- Institute for Environmental Genomics and Department of Microbiology and Plant Biology, University of Oklahoma, Norman, OK 73019
| | - Liyou Wu
- Institute for Environmental Genomics and Department of Microbiology and Plant Biology, University of Oklahoma, Norman, OK 73019
| | - Nitin S Baliga
- Institute for Systems Biology, Seattle, WA 98109-5234; Departments of Biology and Microbiology, Molecular and Cellular Biology Program, University of Washington Seattle, Seattle, WA 98195; Lawrence Berkeley National Laboratory, Berkeley, CA 94720; and
| | - Jizhong Zhou
- Institute for Environmental Genomics and Department of Microbiology and Plant Biology, University of Oklahoma, Norman, OK 73019; Earth Science Division, State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, China
| | - Judy D Wall
- Department of Biochemistry, University of Missouri, Columbia, MO 65211
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95
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Estelmann S, Boll M. Glutaryl-coenzyme A dehydrogenase from Geobacter metallireducens - interaction with electron transferring flavoprotein and kinetic basis of unidirectional catalysis. FEBS J 2014; 281:5120-31. [PMID: 25223645 DOI: 10.1111/febs.13051] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2014] [Revised: 09/04/2014] [Accepted: 09/12/2014] [Indexed: 11/28/2022]
Abstract
Glutaryl-CoA dehydrogenases (GDHs) are FAD containing acyl-CoA dehydrogenases that usually catalyze the dehydrogenation and decarboxylation of glutaryl-CoA to crotonyl-CoA with an electron transferring flavoprotein (ETF) acting as natural electron acceptor. In anaerobic bacteria, GDHs play an important role in the benzoyl-CoA degradation pathway of monocyclic aromatic compounds. In the present study, we identified, purified and characterized the benzoate-induced BamOP as the electron accepting ETF of GDH (BamM) from the Fe(III)-respiring Geobacter metallireducens. The BamOP heterodimer contained FAD and AMP as cofactors. In the absence of an artificial electron acceptor, at pH values above 8, the BamMOP-components catalyzed the expected glutaryl-CoA oxidation to crotonyl-CoA and CO2 ; however, at pH values below 7, the redox-neutral glutaryl-CoA conversion to butyryl-CoA and CO2 became the dominant reaction. This previously unknown, strictly ETF-dependent coupled glutaryl-CoA oxidation/crotonyl-CoA reduction activity was facilitated by an unexpected two-electron transfer between FAD(BamM) and FAD(BamOP) , as well as by the similar redox potentials of the two FAD cofactors in the substrate-bound state. The strict order of electron/proton transfer and C-C-cleavage events including transient charge-transfer complexes did not allow an energetic coupling of electron transfer and decarboxylation. This explains why it was difficult to release the glutaconyl-CoA intermediate from reduced GDH. Moreover, it provides a kinetic rational for the apparent inability of BamM to catalyze the reverse reductive crotonyl-CoA carboxylation, even under thermodynamically favourable conditions. For this reason reductive crotonyl-CoA carboxylation, a key reaction in C2-assimilation via the ethylmalonyl-CoA pathway, is accomplished by a different crotonyl-CoA carboxylase/reductase via a covalent NADPH/ene-adduct.
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96
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Porter AW, Young LY. Benzoyl-CoA, a universal biomarker for anaerobic degradation of aromatic compounds. ADVANCES IN APPLIED MICROBIOLOGY 2014; 88:167-203. [PMID: 24767428 DOI: 10.1016/b978-0-12-800260-5.00005-x] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Aromatic compounds are a major component of the global carbon pool and include a diverse range of compounds such as humic acid, lignin, amino acids, and industrial contaminants. Due to the prevalence of aromatic compounds in the environment, aerobic and anaerobic microorganisms have evolved mechanisms by which to metabolize that available carbon. Less well understood are the anaerobic pathways. We now know that anaerobic metabolism of a variety of monoaromatic compounds can be initiated in a number of different ways, and a key metabolite for these pathways is benzoyl-CoA. Chemicals can have different upstream anaerobic degradation pathways yet can still be assessed by targeting the downstream benzoyl-CoA pathway. In this pathway, we propose that the ring opening hydrolase, encoded by the bamA gene, is especially useful because, in contrast to the benzoyl-CoA reductase, it is detected under a number of respiratory settings, including denitrifying, iron-reducing, sulfate-reducing, and fermentative conditions, and has a wide distribution in the environment. This review examines the bamA gene in enrichment cultures and environmental DNA extracts to consider whether it can be used as a biomarker for anaerobic aromatic degradation. Given the number of potential upstream inputs from natural and man-made monoaromatic compounds, the benzoyl-CoA pathway and the bamA gene in particular may play an important role in the global carbon cycle that has thus far been overlooked.
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Affiliation(s)
- Abigail W Porter
- Department of Environmental Science, School of Biological and Environmental Sciences, Rutgers University, New Brunswick, New Jersey, USA.
| | - Lily Y Young
- Department of Environmental Science, School of Biological and Environmental Sciences, Rutgers University, New Brunswick, New Jersey, USA
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A genomic view on syntrophic versus non-syntrophic lifestyle in anaerobic fatty acid degrading communities. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2014; 1837:2004-2016. [PMID: 24973598 DOI: 10.1016/j.bbabio.2014.06.005] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2013] [Revised: 06/05/2014] [Accepted: 06/09/2014] [Indexed: 11/22/2022]
Abstract
In sulfate-reducing and methanogenic environments complex biopolymers are hydrolyzed and degraded by fermentative micro-organisms that produce hydrogen, carbon dioxide and short chain fatty acids. Degradation of short chain fatty acids can be coupled to methanogenesis or to sulfate-reduction. Here we study from a genome perspective why some of these micro-organisms are able to grow in syntrophy with methanogens and others are not. Bacterial strains were selected based on genome availability and upon their ability to grow on short chain fatty acids alone or in syntrophic association with methanogens. Systematic functional domain profiling allowed us to shed light on this fundamental and ecologically important question. Extra-cytoplasmic formate dehydrogenases (InterPro domain number; IPR006443), including their maturation protein FdhE (IPR024064 and IPR006452) is a typical difference between syntrophic and non-syntrophic butyrate and propionate degraders. Furthermore, two domains with a currently unknown function seem to be associated with the ability of syntrophic growth. One is putatively involved in capsule or biofilm production (IPR019079) and a second in cell division, shape-determination or sporulation (IPR018365). The sulfate-reducing bacteria Desulfobacterium autotrophicum HRM2, Desulfomonile tiedjei and Desulfosporosinus meridiei were never tested for syntrophic growth, but all crucial domains were found in their genomes, which suggests their possible ability to grow in syntrophic association with methanogens. In addition, profiling domains involved in electron transfer mechanisms revealed the important role of the Rnf-complex and the formate transporter in syntrophy, and indicate that DUF224 may have a role in electron transfer in bacteria other than Syntrophomonas wolfei as well. This article is a part of a Special Issue entitled: 18th European Bioenergetics Conference (Biochim. Biophys. Acta, Volume 1837, Issue 7, July 2014).
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98
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Characterization of the RnfB and RnfG subunits of the Rnf complex from the archaeon Methanosarcina acetivorans. PLoS One 2014; 9:e97966. [PMID: 24836163 PMCID: PMC4023990 DOI: 10.1371/journal.pone.0097966] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Accepted: 04/26/2014] [Indexed: 11/20/2022] Open
Abstract
Rnf complexes are redox-driven ion pumps identified in diverse species from the domains Bacteria and Archaea, biochemical characterizations of which are reported for two species from the domain Bacteria. Here, we present characterizations of the redox-active subunits RnfG and RnfB from the Rnf complex of Methanosarcina acetivorans, an acetate-utilizing methane-producing species from the domain Archaea. The purified RnfG subunit produced in Escherichia coli fluoresced in SDS-PAGE gels under UV illumination and showed a UV-visible spectrum typical of flavoproteins. The Thr166Gly variant of RnfG was colorless and failed to fluoresce under UV illumination confirming a role for Thr166 in binding FMN. Redox titration of holo-RnfG revealed a midpoint potential of −129 mV for FMN with n = 2. The overproduced RnfG was primarily localized to the membrane of E. coli and the sequence contained a transmembrane helix. A topological analysis combining reporter protein fusion and computer predictions indicated that the C-terminal domain containing FMN is located on the outer aspect of the cytoplasmic membrane. The purified RnfB subunit produced in E. coli showed a UV-visible spectrum typical of iron-sulfur proteins. The EPR spectra of reduced RnfB featured a broad spectral shape with g values (2.06, 1.94, 1.90, 1.88) characteristic of magnetically coupled 3Fe-4S and 4Fe-4S clusters in close agreement with the iron and acid-labile sulfur content. The ferredoxin specific to the aceticlastic pathway served as an electron donor to RnfB suggesting this subunit is the entry point of electrons to the Rnf complex. The results advance an understanding of the organization and biochemical properties of the Rnf complex and lay a foundation for further understanding the overall mechanism in the pathway of methane formation from acetate.
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99
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Extraordinary phylogenetic diversity and metabolic versatility in aquifer sediment. Nat Commun 2014; 4:2120. [PMID: 23979677 PMCID: PMC3903129 DOI: 10.1038/ncomms3120] [Citation(s) in RCA: 147] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2013] [Accepted: 06/06/2013] [Indexed: 11/08/2022] Open
Abstract
Microorganisms in the subsurface represent a substantial but poorly understood component of the Earth's biosphere. Subsurface environments are complex and difficult to characterize; thus, their microbiota have remained as a 'dark matter' of the carbon and other biogeochemical cycles. Here we deeply sequence two sediment-hosted microbial communities from an aquifer adjacent to the Colorado River, CO, USA. No single organism represents more than ~1% of either community. Remarkably, many bacteria and archaea in these communities are novel at the phylum level or belong to phyla lacking a sequenced representative. The dominant organism in deeper sediment, RBG-1, is a member of a new phylum. On the basis of its reconstructed complete genome, RBG-1 is metabolically versatile. Its wide respiration-based repertoire may enable it to respond to the fluctuating redox environment close to the water table. We document extraordinary microbial novelty and the importance of previously unknown lineages in sediment biogeochemical transformations.
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100
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Lyles CN, Le HM, Beasley WH, McInerney MJ, Suflita JM. Anaerobic hydrocarbon and fatty acid metabolism by syntrophic bacteria and their impact on carbon steel corrosion. Front Microbiol 2014; 5:114. [PMID: 24744752 PMCID: PMC3978324 DOI: 10.3389/fmicb.2014.00114] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2013] [Accepted: 03/07/2014] [Indexed: 11/28/2022] Open
Abstract
The microbial metabolism of hydrocarbons is increasingly associated with the corrosion of carbon steel in sulfate-rich marine waters. However, how such transformations influence metal biocorrosion in the absence of an electron acceptor is not fully recognized. We grew a marine alkane-utilizing, sulfate-reducing bacterium, Desulfoglaeba alkanexedens, with either sulfate or Methanospirillum hungatei as electron acceptors, and tested the ability of the cultures to catalyze metal corrosion. Axenically, D. alkanexedens had a higher instantaneous corrosion rate and produced more pits in carbon steel coupons than when the same organism was grown in syntrophic co-culture with the methanogen. Since anaerobic hydrocarbon biodegradation pathways converge on fatty acid intermediates, the corrosive ability of a known fatty acid-oxidizing syntrophic bacterium, Syntrophus aciditrophicus was compared when grown in pure culture or in co-culture with a H2-utilizing sulfate-reducing bacterium (Desulfovibrio sp., strain G11) or a methanogen (M. hungatei). The instantaneous corrosion rates in the cultures were not substantially different, but the syntrophic, sulfate-reducing co-culture produced more pits in coupons than other combinations of microorganisms. Lactate-grown cultures of strain G11 had higher instantaneous corrosion rates and coupon pitting compared to the same organism cultured with hydrogen as an electron donor. Thus, if sulfate is available as an electron acceptor, the same microbial assemblages produce sulfide and low molecular weight organic acids that exacerbated biocorrosion. Despite these trends, a surprisingly high degree of variation was encountered with the corrosion assessments. Differences in biomass, initial substrate concentration, rates of microbial activity or the degree of end product formation did not account for the variations. We are forced to ascribe such differences to the metallurgical properties of the coupons.
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Affiliation(s)
- Christopher N Lyles
- Department of Microbiology and Plant Biology, Institute for Energy and the Environment, and the OU Biocorrosion Center, University of Oklahoma Norman, OK, USA
| | - Huynh M Le
- Department of Microbiology and Plant Biology, Institute for Energy and the Environment, and the OU Biocorrosion Center, University of Oklahoma Norman, OK, USA
| | | | - Michael J McInerney
- Department of Microbiology and Plant Biology, Institute for Energy and the Environment, and the OU Biocorrosion Center, University of Oklahoma Norman, OK, USA
| | - Joseph M Suflita
- Department of Microbiology and Plant Biology, Institute for Energy and the Environment, and the OU Biocorrosion Center, University of Oklahoma Norman, OK, USA
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