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Lewin GR, Davis NM, McDonald BR, Book AJ, Chevrette MG, Suh S, Boll A, Currie CR. Long-Term Cellulose Enrichment Selects for Highly Cellulolytic Consortia and Competition for Public Goods. mSystems 2022; 7:e0151921. [PMID: 35258341 PMCID: PMC9040578 DOI: 10.1128/msystems.01519-21] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2022] [Accepted: 02/10/2022] [Indexed: 11/23/2022] Open
Abstract
The complexity of microbial communities hinders our understanding of how microbial diversity and microbe-microbe interactions impact community functions. Here, using six independent communities originating from the refuse dumps of leaf-cutter ants and enriched using the plant polymer cellulose as the sole source of carbon, we examine how changes in bacterial diversity and interactions impact plant biomass decomposition. Over up to 60 serial transfers (∼8 months) using Whatman cellulose filter paper, cellulolytic ability increased and then stabilized in four enrichment lines and was variable in two lines. Bacterial community characterization using 16S rRNA gene amplicon sequencing showed community succession differed between the highly cellulolytic enrichment lines and those that had slower and more variable cellulose degradation rates. Metagenomic and metatranscriptomic analyses revealed that Cellvibrio and/or Cellulomonas dominated each enrichment line and produced the majority of cellulase enzymes, while diverse taxa were retained within these communities over the duration of transfers. Interestingly, the less cellulolytic communities had a higher diversity of organisms competing for the cellulose breakdown product cellobiose, suggesting that cheating slowed cellulose degradation. In addition, we found competitive exclusion as an important factor shaping all of the communities, with a negative correlation of Cellvibrio and Cellulomonas abundance within individual enrichment lines and the expression of genes associated with the production of secondary metabolites, toxins, and other antagonistic compounds. Our results provide insights into how microbial diversity and competition affect the stability and function of cellulose-degrading communities. IMPORTANCE Microbial communities are a key driver of the carbon cycle through the breakdown of complex polysaccharides in diverse environments including soil, marine systems, and the mammalian gut. However, due to the complexity of these communities, the species-species interactions that impact community structure and ultimately shape the rate of decomposition are difficult to define. Here, we performed serial enrichment on cellulose using communities inoculated from leaf-cutter ant refuse dumps, a cellulose-rich environment. By concurrently tracking cellulolytic ability and community composition and through metagenomic and metatranscriptomic sequencing, we analyzed the ecological dynamics of the enrichment lines. Our data suggest that antagonism is prevalent in these communities and that competition for soluble sugars may slow degradation and lead to community instability. Together, these results help reveal the relationships between competition and polysaccharide decomposition, with implications in diverse areas ranging from microbial community ecology to cellulosic biofuels production.
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Affiliation(s)
- Gina R. Lewin
- Department of Energy Great Lakes Bioenergy Research Center, University of Wisconsin—Madison, Madison, Wisconsin, USA
- Department of Bacteriology, University of Wisconsin—Madison, Madison, Wisconsin, USA
| | - Nicole M. Davis
- Department of Energy Great Lakes Bioenergy Research Center, University of Wisconsin—Madison, Madison, Wisconsin, USA
- Department of Bacteriology, University of Wisconsin—Madison, Madison, Wisconsin, USA
| | - Bradon R. McDonald
- Department of Bacteriology, University of Wisconsin—Madison, Madison, Wisconsin, USA
| | - Adam J. Book
- Department of Energy Great Lakes Bioenergy Research Center, University of Wisconsin—Madison, Madison, Wisconsin, USA
- Department of Bacteriology, University of Wisconsin—Madison, Madison, Wisconsin, USA
| | - Marc G. Chevrette
- Department of Bacteriology, University of Wisconsin—Madison, Madison, Wisconsin, USA
- Wisconsin Institute for Discovery and Department of Plant Pathology, University of Wisconsin—Madison, Madison, Wisconsin, USA
| | - Steven Suh
- Department of Energy Great Lakes Bioenergy Research Center, University of Wisconsin—Madison, Madison, Wisconsin, USA
- Department of Bacteriology, University of Wisconsin—Madison, Madison, Wisconsin, USA
| | - Ardina Boll
- Department of Energy Great Lakes Bioenergy Research Center, University of Wisconsin—Madison, Madison, Wisconsin, USA
- Department of Bacteriology, University of Wisconsin—Madison, Madison, Wisconsin, USA
| | - Cameron R. Currie
- Department of Energy Great Lakes Bioenergy Research Center, University of Wisconsin—Madison, Madison, Wisconsin, USA
- Department of Bacteriology, University of Wisconsin—Madison, Madison, Wisconsin, USA
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2
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The effect of ionic liquid on the structure of active site pocket and catalytic activity of a β-glucosidase from Halothermothrix orenii. J Mol Liq 2020. [DOI: 10.1016/j.molliq.2020.112879] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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3
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Chuzel L, Ganatra MB, Rapp E, Henrissat B, Taron CH. Functional metagenomics identifies an exosialidase with an inverting catalytic mechanism that defines a new glycoside hydrolase family (GH156). J Biol Chem 2018; 293:18138-18150. [PMID: 30249617 PMCID: PMC6254351 DOI: 10.1074/jbc.ra118.003302] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2018] [Revised: 09/11/2018] [Indexed: 12/24/2022] Open
Abstract
Exosialidases are glycoside hydrolases that remove a single terminal sialic acid residue from oligosaccharides. They are widely distributed in biology, having been found in prokaryotes, eukaryotes, and certain viruses. Most characterized prokaryotic sialidases are from organisms that are pathogenic or commensal with mammals. However, in this study, we used functional metagenomic screening to seek microbial sialidases encoded by environmental DNA isolated from an extreme ecological niche, a thermal spring. Using recombinant expression of potential exosialidase candidates and a fluorogenic sialidase substrate, we discovered an exosialidase having no homology to known sialidases. Phylogenetic analysis indicated that this protein is a member of a small family of bacterial proteins of previously unknown function. Proton NMR revealed that this enzyme functions via an inverting catalytic mechanism, a biochemical property that is distinct from those of known exosialidases. This unique inverting exosialidase defines a new CAZy glycoside hydrolase family we have designated GH156.
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Affiliation(s)
- Léa Chuzel
- From New England Biolabs, Ipswich, Massachusetts 01938,; the Max Planck Institute for Dynamics of Complex Technical Systems, 39106 Magdeburg, Germany
| | | | - Erdmann Rapp
- the Max Planck Institute for Dynamics of Complex Technical Systems, 39106 Magdeburg, Germany,; glyXera GmbH, 39120 Magdeburg, Germany
| | - Bernard Henrissat
- the Architecture et Fonction des Macromolécules Biologiques, CNRS, Aix-Marseille Université, F-13288 Marseille, France,; the Institut National de la Recherche Agronomique (INRA), Unité Sous Contrat (USC) 1408, Architecture et Fonction des Macromolécules Biologiques, 13288 Marseille, France, and; the Department of Biological Sciences, King Abdulaziz University, Jeddah 21589, Saudi Arabia
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4
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Expression of naturally ionic liquid-tolerant thermophilic cellulases in Aspergillus niger. PLoS One 2017; 12:e0189604. [PMID: 29281693 PMCID: PMC5744941 DOI: 10.1371/journal.pone.0189604] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2017] [Accepted: 11/29/2017] [Indexed: 12/03/2022] Open
Abstract
Efficient deconstruction of plant biomass is a major barrier to the development of viable lignocellulosic biofuels. Pretreatment with ionic liquids reduces lignocellulose recalcitrance to enzymatic hydrolysis, increasing yields of sugars for conversion into biofuels. However, commercial cellulases are not compatible with many ionic liquids, necessitating extensive water washing of pretreated biomass prior to hydrolysis. To circumvent this issue, previous research has demonstrated that several thermophilic bacterial cellulases can efficiently deconstruct lignocellulose in the presence of the ionic liquid, 1-ethyl-3-methylimadizolium acetate. As promising as these enzymes are, they would need to be produced at high titer in an industrial enzyme production host before they could be considered a viable alternative to current commercial cellulases. Aspergillus niger has been used to produce high titers of secreted enzymes in industry and therefore, we assessed the potential of this organism to be used as an expression host for these ionic liquid-tolerant cellulases. We demonstrated that 29 of these cellulases were expressed at detectable levels in a wild-type strain of A. niger, indicating a basic level of compatibility and potential to be produced at high levels in a host engineered to produce high titers of enzymes. We then profiled one of these enzymes in detail, the β-glucosidase A5IL97, and compared versions expressed in both A. niger and Escherichia coli. This comparison revealed the enzymatic activity of A5IL97 purified from E. coli and A. niger is equivalent, suggesting that A. niger could be an excellent enzyme production host for enzymes originally characterized in E. coli, facilitating the transition from the laboratory to industry.
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5
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Kolinko S, Wu YW, Tachea F, Denzel E, Hiras J, Gabriel R, Bäcker N, Chan LJG, Eichorst SA, Frey D, Chen Q, Azadi P, Adams PD, Pray TR, Tanjore D, Petzold CJ, Gladden JM, Simmons BA, Singer SW. A bacterial pioneer produces cellulase complexes that persist through community succession. Nat Microbiol 2017; 3:99-107. [PMID: 29109478 PMCID: PMC6794216 DOI: 10.1038/s41564-017-0052-z] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2017] [Accepted: 10/04/2017] [Indexed: 11/16/2022]
Abstract
Cultivation of microbial consortia provides low-complexity communities that can serve as tractable models to understand community dynamics. Time-resolved metagenomics demonstrated that an aerobic cellulolytic consortium cultivated from compost exhibited community dynamics consistent with the definition of an endogenous heterotrophic succession. The genome of the proposed pioneer population, ‘Candidatus Reconcilibacillus cellulovorans’, possessed a gene cluster containing multidomain glycoside hydrolases (GHs). Purification of the soluble cellulase activity from a 300litre cultivation of this consortium revealed that ~70% of the activity arose from the ‘Ca. Reconcilibacillus cellulovorans’ multidomain GHs assembled into cellulase complexes through glycosylation. These remarkably stable complexes have supramolecular structures for enzymatic cellulose hydrolysis that are distinct from cellulosomes. The persistence of these complexes during cultivation indicates that they may be active through multiple cultivations of this consortium and act as public goods that sustain the community. The provision of extracellular GHs as public goods may influence microbial community dynamics in native biomass-deconstructing communities relevant to agriculture, human health and biotechnology. Cultivation of a cellulolytic consortium reveals successional community dynamics and the presence of multidomain glycoside hydrolases assembled into stable complexes distinct from cellulosomes, which are produced by a potential pioneer population.
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Affiliation(s)
- Sebastian Kolinko
- Joint BioEnergy Institute, Emeryville, CA, USA.,Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Yu-Wei Wu
- Joint BioEnergy Institute, Emeryville, CA, USA.,Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.,Graduate Institute of Biomedical Informatics, College of Medical Science and Technology, Taipei Medical University, Taipei, Taiwan
| | - Firehiwot Tachea
- Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.,Advanced Biofuels Process Development Unit, Lawrence Berkeley National Laboratory, Emeryville, CA, USA
| | - Evelyn Denzel
- Joint BioEnergy Institute, Emeryville, CA, USA.,Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.,Faculty of Biotechnology, University of Applied Sciences, Mannheim, Germany
| | - Jennifer Hiras
- Joint BioEnergy Institute, Emeryville, CA, USA.,Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.,Corning Incorporated, Corning, NY, USA
| | - Raphael Gabriel
- Joint BioEnergy Institute, Emeryville, CA, USA.,Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.,Institut für Genetik, Technische Universität Braunschweig, Braunschweig, Germany
| | - Nora Bäcker
- Joint BioEnergy Institute, Emeryville, CA, USA.,Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.,Faculty of Biotechnology, University of Applied Sciences, Mannheim, Germany
| | - Leanne Jade G Chan
- Joint BioEnergy Institute, Emeryville, CA, USA.,Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Stephanie A Eichorst
- Joint BioEnergy Institute, Emeryville, CA, USA.,Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.,Division of Microbial Ecology, Department of Microbiology and Ecosystem Science, Research network "Chemistry meets Microbiology", University of Vienna, Vienna, Austria
| | - Dario Frey
- Joint BioEnergy Institute, Emeryville, CA, USA.,Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.,Faculty of Biotechnology, University of Applied Sciences, Mannheim, Germany
| | - Qiushi Chen
- Complex Carbohydrate Research Center, University of Georgia, Athens, GA, USA
| | - Parastoo Azadi
- Complex Carbohydrate Research Center, University of Georgia, Athens, GA, USA
| | - Paul D Adams
- Joint BioEnergy Institute, Emeryville, CA, USA.,Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Todd R Pray
- Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.,Advanced Biofuels Process Development Unit, Lawrence Berkeley National Laboratory, Emeryville, CA, USA
| | - Deepti Tanjore
- Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.,Advanced Biofuels Process Development Unit, Lawrence Berkeley National Laboratory, Emeryville, CA, USA
| | - Christopher J Petzold
- Joint BioEnergy Institute, Emeryville, CA, USA.,Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - John M Gladden
- Joint BioEnergy Institute, Emeryville, CA, USA.,Biological and Materials Science Center, Sandia National Laboratories, Livermore, CA, USA
| | - Blake A Simmons
- Joint BioEnergy Institute, Emeryville, CA, USA.,Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Steven W Singer
- Joint BioEnergy Institute, Emeryville, CA, USA. .,Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
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6
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Jiménez DJ, Dini-Andreote F, DeAngelis KM, Singer SW, Salles JF, van Elsas JD. Ecological Insights into the Dynamics of Plant Biomass-Degrading Microbial Consortia. Trends Microbiol 2017. [PMID: 28648267 DOI: 10.1016/j.tim.2017.05.012] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Plant biomass (PB) is an important resource for biofuel production. However, the frequent lack of efficiency of PB saccharification is still an industrial bottleneck. The use of enzyme cocktails produced from PB-degrading microbial consortia (PB-dmc) is a promising approach to optimize this process. Nevertheless, the proper use and manipulation of PB-dmc depends on a sound understanding of the ecological processes and mechanisms that exist in these communities. This Opinion article provides an overview of arguments as to how spatiotemporal nutritional fluxes influence the successional dynamics and ecological interactions (synergism versus competition) between populations in PB-dmc. The themes of niche occupancy, 'sugar cheaters', minimal effective consortium, and the Black Queen Hypothesis are raised as key subjects that foster our appraisal of such systems. Here we provide a conceptual framework that describes the critical topics underpinning the ecological basis of PB-dmc, giving a solid foundation upon which further prospective experimentation can be developed.
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Affiliation(s)
- Diego Javier Jiménez
- Microbial Ecology Cluster, Groningen Institute for Evolutionary Life Sciences, University of Groningen, Nijenborgh 7, 9747AG, Groningen, The Netherlands.
| | - Francisco Dini-Andreote
- Microbial Ecology Cluster, Groningen Institute for Evolutionary Life Sciences, University of Groningen, Nijenborgh 7, 9747AG, Groningen, The Netherlands
| | - Kristen M DeAngelis
- Department of Microbiology, University of Massachusetts, 639 North Pleasant Street, Amherst, MA 01003-9298, USA
| | - Steven W Singer
- Joint BioEnergy Institute,5885 Hollis Street, Emeryville, CA 94608, USA; Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA
| | - Joana Falcão Salles
- Microbial Ecology Cluster, Groningen Institute for Evolutionary Life Sciences, University of Groningen, Nijenborgh 7, 9747AG, Groningen, The Netherlands
| | - Jan Dirk van Elsas
- Microbial Ecology Cluster, Groningen Institute for Evolutionary Life Sciences, University of Groningen, Nijenborgh 7, 9747AG, Groningen, The Netherlands
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7
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Characterization of three plant biomass-degrading microbial consortia by metagenomics- and metasecretomics-based approaches. Appl Microbiol Biotechnol 2016; 100:10463-10477. [PMID: 27418359 PMCID: PMC5119850 DOI: 10.1007/s00253-016-7713-3] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2016] [Revised: 06/16/2016] [Accepted: 06/27/2016] [Indexed: 02/01/2023]
Abstract
The selection of microbes by enrichment on plant biomass has been proposed as an efficient way to develop new strategies for lignocellulose saccharification. Here, we report an in-depth analysis of soil-derived microbial consortia that were trained to degrade once-used wheat straw (WS1-M), switchgrass (SG-M) and corn stover (CS-M) under aerobic and mesophilic conditions. Molecular fingerprintings, bacterial 16S ribosomal RNA (rRNA) gene amplicon sequencing and metagenomic analyses showed that the three microbial consortia were taxonomically distinct. Based on the taxonomic affiliation of protein-encoding sequences, members of the Bacteroidetes (e.g. Chryseobacterium, Weeksella, Flavobacterium and Sphingobacterium) were preferentially selected on WS1-M, whereas SG-M and CS-M favoured members of the Proteobacteria (e.g. Caulobacter, Brevundimonas, Stenotrophomonas and Xanthomonas). The highest degradation rates of lignin (~59 %) were observed with SG-M, whereas CS-M showed a high consumption of cellulose and hemicellulose. Analyses of the carbohydrate-active enzymes in the three microbial consortia showed the dominance of glycosyl hydrolases (e.g. of families GH3, GH43, GH13, GH10, GH29, GH28, GH16, GH4 and GH92). In addition, proteins of families AA6, AA10 and AA2 were detected. Analysis of secreted protein fractions (metasecretome) for each selected microbial consortium mainly showed the presence of enzymes able to degrade arabinan, arabinoxylan, xylan, β-glucan, galactomannan and rhamnogalacturonan. Notably, these metasecretomes contain enzymes that enable us to produce oligosaccharides directly from wheat straw, sugarcane bagasse and willow. Thus, the underlying microbial consortia constitute valuable resources for the production of enzyme cocktails for the efficient saccharification of plant biomass.
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8
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Substrate-Specific Development of Thermophilic Bacterial Consortia by Using Chemically Pretreated Switchgrass. Appl Environ Microbiol 2014; 80:7423-32. [PMID: 25261509 DOI: 10.1128/aem.02795-14] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Accepted: 09/19/2014] [Indexed: 12/14/2022] Open
Abstract
Microbial communities that deconstruct plant biomass have broad relevance in biofuel production and global carbon cycling. Biomass pretreatments reduce plant biomass recalcitrance for increased efficiency of enzymatic hydrolysis. We exploited these chemical pretreatments to study how thermophilic bacterial consortia adapt to deconstruct switchgrass (SG) biomass of various compositions. Microbial communities were adapted to untreated, ammonium fiber expansion (AFEX)-pretreated, and ionic-liquid (IL)-pretreated SG under aerobic, thermophilic conditions using green waste compost as the inoculum to study biomass deconstruction by microbial consortia. After microbial cultivation, gravimetric analysis of the residual biomass demonstrated that both AFEX and IL pretreatment enhanced the deconstruction of the SG biomass approximately 2-fold. Two-dimensional nuclear magnetic resonance (2D-NMR) experiments and acetyl bromide-reactive-lignin analysis indicated that polysaccharide hydrolysis was the dominant process occurring during microbial biomass deconstruction, and lignin remaining in the residual biomass was largely unmodified. Small-subunit (SSU) rRNA gene amplicon libraries revealed that although the dominant taxa across these chemical pretreatments were consistently represented by members of the Firmicutes, the Bacteroidetes, and Deinococcus-Thermus, the abundance of selected operational taxonomic units (OTUs) varied, suggesting adaptations to the different substrates. Combining the observations of differences in the community structure and the chemical and physical structure of the biomass, we hypothesize specific roles for individual community members in biomass deconstruction.
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9
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Gladden JM, Park JI, Bergmann J, Reyes-Ortiz V, D'haeseleer P, Quirino BF, Sale KL, Simmons BA, Singer SW. Discovery and characterization of ionic liquid-tolerant thermophilic cellulases from a switchgrass-adapted microbial community. BIOTECHNOLOGY FOR BIOFUELS 2014; 7:15. [PMID: 24479406 PMCID: PMC3923250 DOI: 10.1186/1754-6834-7-15] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2013] [Accepted: 01/15/2014] [Indexed: 05/02/2023]
Abstract
BACKGROUND The development of advanced biofuels from lignocellulosic biomass will require the use of both efficient pretreatment methods and new biomass-deconstructing enzyme cocktails to generate sugars from lignocellulosic substrates. Certain ionic liquids (ILs) have emerged as a promising class of compounds for biomass pretreatment and have been demonstrated to reduce the recalcitrance of biomass for enzymatic hydrolysis. However, current commercial cellulase cocktails are strongly inhibited by most of the ILs that are effective biomass pretreatment solvents. Fortunately, recent research has shown that IL-tolerant cocktails can be formulated and are functional on lignocellulosic biomass. This study sought to expand the list of known IL-tolerant cellulases to further enable IL-tolerant cocktail development by developing a combined in vitro/in vivo screening pipeline for metagenome-derived genes. RESULTS Thirty-seven predicted cellulases derived from a thermophilic switchgrass-adapted microbial community were screened in this study. Eighteen of the twenty-one enzymes that expressed well in E. coli were active in the presence of the IL 1-ethyl-3-methylimidazolium acetate ([C2mim][OAc]) concentrations of at least 10% (v/v), with several retaining activity in the presence of 40% (v/v), which is currently the highest reported tolerance to [C2mim][OAc] for any cellulase. In addition, the optimum temperatures of the enzymes ranged from 45 to 95°C and the pH optimum ranged from 5.5 to 7.5, indicating these enzymes can be used to construct cellulase cocktails that function under a broad range of temperature, pH and IL concentrations. CONCLUSIONS This study characterized in detail twenty-one cellulose-degrading enzymes derived from a thermophilic microbial community and found that 70% of them were [C2mim][OAc]-tolerant. A comparison of optimum temperature and [C2mim][OAc]-tolerance demonstrates that a positive correlation exists between these properties for those enzymes with a optimum temperature >70°C, further strengthening the link between thermotolerance and IL-tolerance for lignocelluolytic glycoside hydrolases.
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Affiliation(s)
- John M Gladden
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Joint BioEnergy Institute (JBEI), 1 Cyclotron Road, Berkeley, CA 94720, USA.
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10
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D'haeseleer P, Gladden JM, Allgaier M, Chain PSG, Tringe SG, Malfatti SA, Aldrich JT, Nicora CD, Robinson EW, Paša-Tolić L, Hugenholtz P, Simmons BA, Singer SW. Proteogenomic analysis of a thermophilic bacterial consortium adapted to deconstruct switchgrass. PLoS One 2013; 8:e68465. [PMID: 23894306 PMCID: PMC3716776 DOI: 10.1371/journal.pone.0068465] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2013] [Accepted: 05/29/2013] [Indexed: 12/02/2022] Open
Abstract
Thermophilic bacteria are a potential source of enzymes for the deconstruction of lignocellulosic biomass. However, the complement of proteins used to deconstruct biomass and the specific roles of different microbial groups in thermophilic biomass deconstruction are not well-explored. Here we report on the metagenomic and proteogenomic analyses of a compost-derived bacterial consortium adapted to switchgrass at elevated temperature with high levels of glycoside hydrolase activities. Near-complete genomes were reconstructed for the most abundant populations, which included composite genomes for populations closely related to sequenced strains of Thermus thermophilus and Rhodothermus marinus, and for novel populations that are related to thermophilic Paenibacilli and an uncultivated subdivision of the little-studied Gemmatimonadetes phylum. Partial genomes were also reconstructed for a number of lower abundance thermophilic Chloroflexi populations. Identification of genes for lignocellulose processing and metabolic reconstructions suggested Rhodothermus, Paenibacillus and Gemmatimonadetes as key groups for deconstructing biomass, and Thermus as a group that may primarily metabolize low molecular weight compounds. Mass spectrometry-based proteomic analysis of the consortium was used to identify >3000 proteins in fractionated samples from the cultures, and confirmed the importance of Paenibacillus and Gemmatimonadetes to biomass deconstruction. These studies also indicate that there are unexplored proteins with important roles in bacterial lignocellulose deconstruction.
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Affiliation(s)
- Patrik D'haeseleer
- Joint BioEnergy Institute, Emeryville, California, United States of America.
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11
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Eichorst SA, Varanasi P, Stavila V, Zemla M, Auer M, Singh S, Simmons BA, Singer SW. Community dynamics of cellulose-adapted thermophilic bacterial consortia. Environ Microbiol 2013; 15:2573-87. [DOI: 10.1111/1462-2920.12159] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2013] [Revised: 04/29/2013] [Accepted: 05/15/2013] [Indexed: 12/01/2022]
Affiliation(s)
| | | | - Vatalie Stavila
- Biological and Materials Sciences Center; Sandia National Laboratories; Livermore; CA; 94551; USA
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12
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Peacock JP, Cole JK, Murugapiran SK, Dodsworth JA, Fisher JC, Moser DP, Hedlund BP. Pyrosequencing reveals high-temperature cellulolytic microbial consortia in Great Boiling Spring after in situ lignocellulose enrichment. PLoS One 2013; 8:e59927. [PMID: 23555835 PMCID: PMC3612082 DOI: 10.1371/journal.pone.0059927] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2012] [Accepted: 02/20/2013] [Indexed: 02/01/2023] Open
Abstract
To characterize high-temperature cellulolytic microbial communities, two lignocellulosic substrates, ammonia fiber-explosion-treated corn stover and aspen shavings, were incubated at average temperatures of 77 and 85°C in the sediment and water column of Great Boiling Spring, Nevada. Comparison of 109,941 quality-filtered 16S rRNA gene pyrosequences (pyrotags) from eight enrichments to 37,057 quality-filtered pyrotags from corresponding natural samples revealed distinct enriched communities dominated by phylotypes related to cellulolytic and hemicellulolytic Thermotoga and Dictyoglomus, cellulolytic and sugar-fermenting Desulfurococcales, and sugar-fermenting and hydrogenotrophic Archaeoglobales. Minor enriched populations included close relatives of hydrogenotrophic Thermodesulfobacteria, the candidate bacterial phylum OP9, and candidate archaeal groups C2 and DHVE3. Enrichment temperature was the major factor influencing community composition, with a negative correlation between temperature and richness, followed by lignocellulosic substrate composition. This study establishes the importance of these groups in the natural degradation of lignocellulose at high temperatures and suggests that a substantial portion of the diversity of thermophiles contributing to consortial cellulolysis may be contained within lineages that have representatives in pure culture.
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Affiliation(s)
- Joseph P Peacock
- School of Life Sciences, University of Nevada, Las Vegas, Nevada, United States of America
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13
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A thermophilic ionic liquid-tolerant cellulase cocktail for the production of cellulosic biofuels. PLoS One 2012; 7:e37010. [PMID: 22649505 PMCID: PMC3359315 DOI: 10.1371/journal.pone.0037010] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2012] [Accepted: 04/11/2012] [Indexed: 11/19/2022] Open
Abstract
Generation of biofuels from sugars in lignocellulosic biomass is a promising alternative to liquid fossil fuels, but efficient and inexpensive bioprocessing configurations must be developed to make this technology commercially viable. One of the major barriers to commercialization is the recalcitrance of plant cell wall polysaccharides to enzymatic hydrolysis. Biomass pretreatment with ionic liquids (ILs) enables efficient saccharification of biomass, but residual ILs inhibit both saccharification and microbial fuel production, requiring extensive washing after IL pretreatment. Pretreatment itself can also produce biomass-derived inhibitory compounds that reduce microbial fuel production. Therefore, there are multiple points in the process from biomass to biofuel production that must be interrogated and optimized to maximize fuel production. Here, we report the development of an IL-tolerant cellulase cocktail by combining thermophilic bacterial glycoside hydrolases produced by a mixed consortia with recombinant glycoside hydrolases. This enzymatic cocktail saccharifies IL-pretreated biomass at higher temperatures and in the presence of much higher IL concentrations than commercial fungal cocktails. Sugars obtained from saccharification of IL-pretreated switchgrass using this cocktail can be converted into biodiesel (fatty acid ethyl-esters or FAEEs) by a metabolically engineered strain of E. coli. During these studies, we found that this biodiesel-producing E. coli strain was sensitive to ILs and inhibitors released by saccharification. This cocktail will enable the development of novel biomass to biofuel bioprocessing configurations that may overcome some of the barriers to production of inexpensive cellulosic biofuels.
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