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Storani A, Guerrero SA, Iglesias AA. On the functionality of the N-terminal domain in xylanase 10A from Ruminococcus albus 8. Enzyme Microb Technol 2020; 142:109673. [PMID: 33220861 DOI: 10.1016/j.enzmictec.2020.109673] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2020] [Revised: 09/02/2020] [Accepted: 09/17/2020] [Indexed: 10/23/2022]
Abstract
We analyzed the structure to function relationships in Ruminococcus albus 8 xylanase 10A (RalXyn10A) finding that the N-terminus 34-amino acids sequence (N34) in the protein is particularly functional. We performed the recombinant wild type enzyme's characterization and that of the truncated mutant lacking the N34 extreme (RalΔN34Xyn10A). The truncated enzyme exhibited about half of the activity and reduced affinity for binding to insoluble saccharides. These suggest a (CBM)-like function for the N34 motif. Besides, RalXyn10A activity was diminished by redox agent dithiothreitol, a characteristic absent in RalΔN34Xyn10A. The N34 sequence exhibited a significant similarity with protein components of the ABC transporter of the bacterial membrane, and this motif is present in other proteins of R. albus 8. Data suggest that N34 would confer RalXyn10A the capacity to interact with polysaccharides and components of the cell membrane, enhancing the degradation of the substrate and uptake of the products by the bacterium.
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Affiliation(s)
- Alem Storani
- Laboratorio de Enzimología Molecular, Instituto de Agrobiotecnología del Litoral (CONICET - UNL). Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, 3000, Santa Fe, Argentina
| | - Sergio A Guerrero
- Laboratorio de Enzimología Molecular, Instituto de Agrobiotecnología del Litoral (CONICET - UNL). Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, 3000, Santa Fe, Argentina
| | - Alberto A Iglesias
- Laboratorio de Enzimología Molecular, Instituto de Agrobiotecnología del Litoral (CONICET - UNL). Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, 3000, Santa Fe, Argentina.
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Israeli-Ruimy V, Bule P, Jindou S, Dassa B, Moraïs S, Borovok I, Barak Y, Slutzki M, Hamberg Y, Cardoso V, Alves VD, Najmudin S, White BA, Flint HJ, Gilbert HJ, Lamed R, Fontes CMGA, Bayer EA. Complexity of the Ruminococcus flavefaciens FD-1 cellulosome reflects an expansion of family-related protein-protein interactions. Sci Rep 2017; 7:42355. [PMID: 28186207 PMCID: PMC5301203 DOI: 10.1038/srep42355] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2016] [Accepted: 01/08/2017] [Indexed: 11/25/2022] Open
Abstract
Protein-protein interactions play a vital role in cellular processes as exemplified by assembly of the intricate multi-enzyme cellulosome complex. Cellulosomes are assembled by selective high-affinity binding of enzyme-borne dockerin modules to repeated cohesin modules of structural proteins termed scaffoldins. Recent sequencing of the fiber-degrading Ruminococcus flavefaciens FD-1 genome revealed a particularly elaborate cellulosome system. In total, 223 dockerin-bearing ORFs potentially involved in cellulosome assembly and a variety of multi-modular scaffoldins were identified, and the dockerins were classified into six major groups. Here, extensive screening employing three complementary medium- to high-throughput platforms was used to characterize the different cohesin-dockerin specificities. The platforms included (i) cellulose-coated microarray assay, (ii) enzyme-linked immunosorbent assay (ELISA) and (iii) in-vivo co-expression and screening in Escherichia coli. The data revealed a collection of unique cohesin-dockerin interactions and support the functional relevance of dockerin classification into groups. In contrast to observations reported previously, a dual-binding mode is involved in cellulosome cell-surface attachment, whereas single-binding interactions operate for cellulosome integration of enzymes. This sui generis cellulosome model enhances our understanding of the mechanisms governing the remarkable ability of R. flavefaciens to degrade carbohydrates in the bovine rumen and provides a basis for constructing efficient nano-machines applied to biological processes.
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Affiliation(s)
- Vered Israeli-Ruimy
- Department of Biomolecular Sciences, The Weizmann Institute of Science, Rehovot, Israel
| | - Pedro Bule
- CIISA – Faculdade de Medicina Veterinária, Universidade de Lisboa, Avenida da Universidade Técnica, 1300-477 Lisboa, Portugal
| | - Sadanari Jindou
- Department of Molecular Microbiology and Biotechnology, Tel Aviv University, Ramat Aviv, Israel
| | - Bareket Dassa
- Department of Biomolecular Sciences, The Weizmann Institute of Science, Rehovot, Israel
| | - Sarah Moraïs
- Department of Biomolecular Sciences, The Weizmann Institute of Science, Rehovot, Israel
| | - Ilya Borovok
- Department of Molecular Microbiology and Biotechnology, Tel Aviv University, Ramat Aviv, Israel
| | - Yoav Barak
- Department of Biomolecular Sciences, The Weizmann Institute of Science, Rehovot, Israel
- Chemical Research Support, The Weizmann Institute of Science, Rehovot, Israel
| | - Michal Slutzki
- Department of Biomolecular Sciences, The Weizmann Institute of Science, Rehovot, Israel
| | - Yuval Hamberg
- Department of Biomolecular Sciences, The Weizmann Institute of Science, Rehovot, Israel
| | - Vânia Cardoso
- CIISA – Faculdade de Medicina Veterinária, Universidade de Lisboa, Avenida da Universidade Técnica, 1300-477 Lisboa, Portugal
| | - Victor D. Alves
- CIISA – Faculdade de Medicina Veterinária, Universidade de Lisboa, Avenida da Universidade Técnica, 1300-477 Lisboa, Portugal
| | - Shabir Najmudin
- CIISA – Faculdade de Medicina Veterinária, Universidade de Lisboa, Avenida da Universidade Técnica, 1300-477 Lisboa, Portugal
| | - Bryan A. White
- Department of Animal Sciences, Institute for Genomic Biology, University of Illinois at Urbana–Champaign, Champaign, IL, USA
- Department of Animal Sciences, University of Illinois at Urbana–Champaign, Champaign, IL, USA
| | - Harry J. Flint
- Microbiology Group, Rowett Institute of Nutrition and Health, University of Aberdeen, Foresterhill, Aberdeen, Scotland, UK
| | - Harry J. Gilbert
- Institute for Cell and Molecular Biosciences, Newcastle University, The Medical School, Newcastle upon Tyne NE2 4HH, UK
| | - Raphael Lamed
- Department of Molecular Microbiology and Biotechnology, Tel Aviv University, Ramat Aviv, Israel
| | - Carlos M. G. A. Fontes
- CIISA – Faculdade de Medicina Veterinária, Universidade de Lisboa, Avenida da Universidade Técnica, 1300-477 Lisboa, Portugal
| | - Edward A. Bayer
- Department of Biomolecular Sciences, The Weizmann Institute of Science, Rehovot, Israel
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Abstract
Information available on the role of Mg for growth and cellulose degradation by rumen bacteria is both limited and inconsistent. In this study, the Mg requirements for two strains each of the cellulolytic rumen species Fibrobacter succinogenes (A3c and S85), Ruminococcus albus (7 and 8) and Ruminococcus flavefaciens (B34b and C94) were investigated. Maximum growth, rate of growth and lag time were all measured using a complete factorial design, 2(3)×6; factors were: strains (2), within species (3) and Mg concentrations (6). R. flavefaciens was the only species that did not grow when Mg was singly deleted from the media, and both strains exhibited a linear growth response to increasing Mg concentrations (P<0.001). The requirement for R. flavefaciens B34b was estimated as 0.54 mM; whereas the requirement for R. flavefaciens C94 was >0.82 as there was no plateau in growth. Although not an absolute requirement for growth, strains of the two other species of cellulolytic bacteria all responded to increasing Mg concentrations. For F. succinogenes S85, R. albus 7 and R. albus 8, their requirement estimated from maximum growth was 0.56, 0.52 and 0.51, respectively. A requirement for F. succinogenes A3c could not be calculated because there was no solution for contrasts. Whether R. flavefaciens had a Mg requirement for cellulose degradation was determined in NH3-free cellulose media, using a 2×4 factorial design, 2 strains and 4 treatments. Both strains of R. flavefaciens were found to have an absolute Mg requirement for cellulose degradation. Based on reported concentrations of Mg in the rumen, 1.0 to 10.1 mM, it seems unlikely that an in vivo deficiency of this element would occur.
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Rincon MT, Dassa B, Flint HJ, Travis AJ, Jindou S, Borovok I, Lamed R, Bayer EA, Henrissat B, Coutinho PM, Antonopoulos DA, Berg Miller ME, White BA. Abundance and diversity of dockerin-containing proteins in the fiber-degrading rumen bacterium, Ruminococcus flavefaciens FD-1. PLoS One 2010; 5:e12476. [PMID: 20814577 PMCID: PMC2930009 DOI: 10.1371/journal.pone.0012476] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2010] [Accepted: 08/03/2010] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND The cellulosome is a multi-enzyme machine, which plays a key role in the breakdown of plant cell walls in many anaerobic cellulose-degrading microorganisms. Ruminococcus flavefaciens FD-1, a major fiber-degrading bacterium present in the gut of herbivores, has the most intricate cellulosomal organization thus far described. Cellulosome complexes are assembled through high-affinity cohesin-dockerin interactions. More than two-hundred dockerin-containing proteins have been identified in the R. flavefaciens genome, yet the reason for the expansion of these crucial cellulosomal components is yet unknown. METHODOLOGY/PRINCIPAL FINDINGS We have explored the full spectrum of 222 dockerin-containing proteins potentially involved in the assembly of cellulosome-like complexes of R. flavefaciens. Bioinformatic analysis of the various dockerin modules showed distinctive conservation patterns within their two Ca(2+)-binding repeats and their flanking regions. Thus, we established the conceptual framework for six major groups of dockerin types, according to their unique sequence features. Within this framework, the modular architecture of the parent proteins, some of which are multi-functional proteins, was evaluated together with their gene expression levels. Specific dockerin types were found to be associated with selected groups of functional components, such as carbohydrate-binding modules, numerous peptidases, and/or carbohydrate-active enzymes. In addition, members of other dockerin groups were linked to structural proteins, e.g., cohesin-containing proteins, belonging to the scaffoldins. CONCLUSIONS/SIGNIFICANCE This report profiles the abundance and sequence diversity of the R. flavefaciens FD-1 dockerins, and provides the molecular basis for future understanding of the potential for a wide array of cohesin-dockerin specificities. Conserved differences between dockerins may be reflected in their stability, function or expression within the context of the parent protein, in response to their role in the rumen environment.
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Affiliation(s)
- Marco T. Rincon
- Microbial Ecology Group, Rowett Institute of Nutrition and Health, University of Aberdeen, Aberdeen, United Kingdom
| | - Bareket Dassa
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot, Israel
| | - Harry J. Flint
- Microbial Ecology Group, Rowett Institute of Nutrition and Health, University of Aberdeen, Aberdeen, United Kingdom
| | - Anthony J. Travis
- Microbial Ecology Group, Rowett Institute of Nutrition and Health, University of Aberdeen, Aberdeen, United Kingdom
| | - Sadanari Jindou
- Department of Molecular Microbiology and Biotechnology, Tel Aviv University, Ramat Aviv, Israel
| | - Ilya Borovok
- Department of Molecular Microbiology and Biotechnology, Tel Aviv University, Ramat Aviv, Israel
| | - Raphael Lamed
- Department of Molecular Microbiology and Biotechnology, Tel Aviv University, Ramat Aviv, Israel
| | - Edward A. Bayer
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot, Israel
| | - Bernard Henrissat
- Architecture et Fonction des Macromolecules Biologiques, CNRS and Universites d'Aix-Marseille I & II, Marseille, France
| | - Pedro M. Coutinho
- Architecture et Fonction des Macromolecules Biologiques, CNRS and Universites d'Aix-Marseille I & II, Marseille, France
| | - Dion A. Antonopoulos
- Division of Nutritional Sciences, Department of Animal Sciences, North American Consortium for Genomics of Fibrolytic Ruminal Bacteria, University of Illinois, Urbana, Illinois, United States of America
| | - Margret E. Berg Miller
- Division of Nutritional Sciences, Department of Animal Sciences, North American Consortium for Genomics of Fibrolytic Ruminal Bacteria, University of Illinois, Urbana, Illinois, United States of America
| | - Bryan A. White
- Division of Nutritional Sciences, Department of Animal Sciences, North American Consortium for Genomics of Fibrolytic Ruminal Bacteria, University of Illinois, Urbana, Illinois, United States of America
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Berg Miller ME, Antonopoulos DA, Rincon MT, Band M, Bari A, Akraiko T, Hernandez A, Thimmapuram J, Henrissat B, Coutinho PM, Borovok I, Jindou S, Lamed R, Flint HJ, Bayer EA, White BA. Diversity and strain specificity of plant cell wall degrading enzymes revealed by the draft genome of Ruminococcus flavefaciens FD-1. PLoS One 2009; 4:e6650. [PMID: 19680555 PMCID: PMC2721979 DOI: 10.1371/journal.pone.0006650] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2009] [Accepted: 07/07/2009] [Indexed: 11/19/2022] Open
Abstract
Background Ruminococcus flavefaciens is a predominant cellulolytic rumen bacterium, which forms a multi-enzyme cellulosome complex that could play an integral role in the ability of this bacterium to degrade plant cell wall polysaccharides. Identifying the major enzyme types involved in plant cell wall degradation is essential for gaining a better understanding of the cellulolytic capabilities of this organism as well as highlighting potential enzymes for application in improvement of livestock nutrition and for conversion of cellulosic biomass to liquid fuels. Methodology/Principal Findings The R. flavefaciens FD-1 genome was sequenced to 29x-coverage, based on pulsed-field gel electrophoresis estimates (4.4 Mb), and assembled into 119 contigs providing 4,576,399 bp of unique sequence. As much as 87.1% of the genome encodes ORFs, tRNA, rRNAs, or repeats. The GC content was calculated at 45%. A total of 4,339 ORFs was detected with an average gene length of 918 bp. The cellulosome model for R. flavefaciens was further refined by sequence analysis, with at least 225 dockerin-containing ORFs, including previously characterized cohesin-containing scaffoldin molecules. These dockerin-containing ORFs encode a variety of catalytic modules including glycoside hydrolases (GHs), polysaccharide lyases, and carbohydrate esterases. Additionally, 56 ORFs encode proteins that contain carbohydrate-binding modules (CBMs). Functional microarray analysis of the genome revealed that 56 of the cellulosome-associated ORFs were up-regulated, 14 were down-regulated, 135 were unaffected, when R. flavefaciens FD-1 was grown on cellulose versus cellobiose. Three multi-modular xylanases (ORF01222, ORF03896, and ORF01315) exhibited the highest levels of up-regulation. Conclusions/Significance The genomic evidence indicates that R. flavefaciens FD-1 has the largest known number of fiber-degrading enzymes likely to be arranged in a cellulosome architecture. Functional analysis of the genome has revealed that the growth substrate drives expression of enzymes predicted to be involved in carbohydrate metabolism as well as expression and assembly of key cellulosomal enzyme components.
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Affiliation(s)
- Margret E. Berg Miller
- Department of Animal Sciences, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Dionysios A. Antonopoulos
- Department of Animal Sciences, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Marco T. Rincon
- Microbial Ecology Group, Rowett Institute of Nutrition and Health, University of Aberdeen, Aberdeen, United Kingdom
| | - Mark Band
- Department of Animal Sciences, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Albert Bari
- Department of Animal Sciences, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Tatsiana Akraiko
- Department of Animal Sciences, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Alvaro Hernandez
- Department of Animal Sciences, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Jyothi Thimmapuram
- Department of Animal Sciences, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Bernard Henrissat
- Architecture et Fonction des Macromolécules Biologiques, CNRS and Universités Aix-Marseille I & II, Marseille, France
| | - Pedro M. Coutinho
- Architecture et Fonction des Macromolécules Biologiques, CNRS and Universités Aix-Marseille I & II, Marseille, France
| | - Ilya Borovok
- Department of Molecular Microbiology and Biotechnology, Tel Aviv University, Ramat Aviv, Israel
| | - Sadanari Jindou
- Department of Molecular Microbiology and Biotechnology, Tel Aviv University, Ramat Aviv, Israel
| | - Raphael Lamed
- Department of Molecular Microbiology and Biotechnology, Tel Aviv University, Ramat Aviv, Israel
| | - Harry J. Flint
- Microbial Ecology Group, Rowett Institute of Nutrition and Health, University of Aberdeen, Aberdeen, United Kingdom
| | - Edward A. Bayer
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot, Israel
| | - Bryan A. White
- Department of Animal Sciences, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
- Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
- * E-mail:
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6
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Flint HJ, Bayer EA. Plant cell wall breakdown by anaerobic microorganisms from the Mammalian digestive tract. Ann N Y Acad Sci 2008; 1125:280-8. [PMID: 18378598 DOI: 10.1196/annals.1419.022] [Citation(s) in RCA: 151] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Degradation of lignocellulosic plant material in the mammalian digestive tract is accomplished by communities of anaerobic microorganisms that exist in symbiotic association with the host. Catalytic domains and substrate-binding modules concerned with plant polysaccharide degradation are found in a variety of anaerobic bacteria, fungi, and protozoa from the mammalian gut. The organization of plant cell wall-degrading enzymes, however, varies widely. The cellulolytic gram-positive bacterium Ruminococcus flavefaciens produces an elaborate cellulosomal enzyme complex that is anchored to the bacterial cell wall; assembly of the complex involves at least five different dockerin:cohesin specificities, and the R. flavefaciens genome encodes at least 180 dockerin-containing proteins that encompass a wide array of catalytic and binding activities. On the other hand, in the cellulolytic protozoan, Polyplastron multivesiculatum, individual plant cell wall-degrading enzymes appear to be secreted into food vacuoles, while the gram-negative bacterium Prevotella bryantii appears to possess a sequestration-type system for the utilization of soluble xylans. The system that is employed for polysaccharide utilization must play a major role in defining the ecological niche that each organism occupies within a complex gut community. 16S rRNA analyses are also revealing uncultured bacterial species closely adherent to fibrous substrates in the rumen and in the large intestine of animals and humans. The true complexity, both at a single organism and community level, of the microbial enzyme systems that allow animals to digest plant material is beginning to become apparent.
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Affiliation(s)
- Harry J Flint
- Microbial Ecology Group, Rowett Research Institute, Greenburn Road, Bucksburn, Aberdeen AB21 9SB, UK.
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7
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Jindou S, Borovok I, Rincon MT, Flint HJ, Antonopoulos DA, Berg ME, White BA, Bayer EA, Lamed R. Conservation and divergence in cellulosome architecture between two strains of Ruminococcus flavefaciens. J Bacteriol 2006; 188:7971-6. [PMID: 16997963 PMCID: PMC1636321 DOI: 10.1128/jb.00973-06] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A 17-kb scaffoldin gene cluster in Ruminococcus flavefaciens strain FD-1 was compared with the homologous segment published for strain 17. Although the general design of the cluster is identical in the two strains, significant differences in the modular architecture of the scaffoldin proteins were discovered, implying strain-specific divergence in cellulosome organization.
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Affiliation(s)
- Sadanari Jindou
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot 76100, Israel
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Reveneau C, Adams SE, Cotta MA, Morrison M. Phenylacetic and phenylpropionic acids do not affect xylan degradation by Ruminococcus albus. Appl Environ Microbiol 2004; 69:6954-8. [PMID: 14602663 PMCID: PMC262313 DOI: 10.1128/aem.69.11.6954-6958.2003] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Since the addition of either ruminal fluid or a combination of phenylacetic and phenylpropionic acids (PAA/PPA) has previously been shown to dramatically improve cellulose degradation and growth of Ruminococcus albus, it was of interest to determine the effects of these additives on xylan-grown cultures. Although cell-bound xylanase activity increased when either PAA/PPA or ruminal fluid was added to the growth medium, total xylanase did not change, and neither of these supplements affected the growth or xylan-degrading capacity of R. albus 8. Similarly, neither PAA/PPA nor ruminal fluid affected xylan degradation by multiple strains of R. albus when xylan prepared from oat spelts was used as a carbohydrate source. These results show that the xylanolytic potential of R. albus is not conditional on the availability of PAA/PPA or other components of ruminal fluid.
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Affiliation(s)
- Carine Reveneau
- The MAPLE Research Program, Department of Animal Sciences, The Ohio State University, Columbus, Ohio 43210, USA
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Flint HJ. Polysaccharide Breakdown by Anaerobic Microorganisms Inhabiting the Mammalian Gut. ADVANCES IN APPLIED MICROBIOLOGY 2004; 56:89-120. [PMID: 15566977 DOI: 10.1016/s0065-2164(04)56003-3] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Harry J Flint
- Microbial Genetics Group Rowett Research Institute Bucksburn, Aberdeen, AB21 9SB, United Kingdom.
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Lynd LR, Weimer PJ, van Zyl WH, Pretorius IS. Microbial cellulose utilization: fundamentals and biotechnology. Microbiol Mol Biol Rev 2002; 66:506-77, table of contents. [PMID: 12209002 PMCID: PMC120791 DOI: 10.1128/mmbr.66.3.506-577.2002] [Citation(s) in RCA: 2307] [Impact Index Per Article: 104.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Fundamental features of microbial cellulose utilization are examined at successively higher levels of aggregation encompassing the structure and composition of cellulosic biomass, taxonomic diversity, cellulase enzyme systems, molecular biology of cellulase enzymes, physiology of cellulolytic microorganisms, ecological aspects of cellulase-degrading communities, and rate-limiting factors in nature. The methodological basis for studying microbial cellulose utilization is considered relative to quantification of cells and enzymes in the presence of solid substrates as well as apparatus and analysis for cellulose-grown continuous cultures. Quantitative description of cellulose hydrolysis is addressed with respect to adsorption of cellulase enzymes, rates of enzymatic hydrolysis, bioenergetics of microbial cellulose utilization, kinetics of microbial cellulose utilization, and contrasting features compared to soluble substrate kinetics. A biological perspective on processing cellulosic biomass is presented, including features of pretreated substrates and alternative process configurations. Organism development is considered for "consolidated bioprocessing" (CBP), in which the production of cellulolytic enzymes, hydrolysis of biomass, and fermentation of resulting sugars to desired products occur in one step. Two organism development strategies for CBP are examined: (i) improve product yield and tolerance in microorganisms able to utilize cellulose, or (ii) express a heterologous system for cellulose hydrolysis and utilization in microorganisms that exhibit high product yield and tolerance. A concluding discussion identifies unresolved issues pertaining to microbial cellulose utilization, suggests approaches by which such issues might be resolved, and contrasts a microbially oriented cellulose hydrolysis paradigm to the more conventional enzymatically oriented paradigm in both fundamental and applied contexts.
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Affiliation(s)
- Lee R Lynd
- Chemical and Biochemical Engineering, Thayer School of Engineering and Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire 03755, USA.
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11
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Saluzzi L, Flint HJ, Stewart CS. Adaptation of Ruminococcus flavefaciens resulting in increased degradation of ryegrass cell walls. FEMS Microbiol Ecol 2001; 36:131-137. [PMID: 11451517 DOI: 10.1111/j.1574-6941.2001.tb00833.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
This study investigated the long term adaptation of a ruminal bacterium to growth on four different plant cell wall substrates. No significant increase in degradation was detected for lucerne, barley straw or weeping lovegrass after 23 serial subcultures of the cellulolytic rumen bacterium Ruminococcus flavefaciens strain 17 on each of these substrates. Significantly increased substrate degradation by R. flavefaciens strain 17 was however observed after 23 subcultures on perennial ryegrass. The increase in dry matter solubilisation (from 24.3 to 39.5% in 24 h incubation and from 52.3 to 61% in 72 h) was at least partially due to an increase in solubilisation of xylose, glucose and arabinose. Enhanced growth of the adapted strains occurred on this substrate. Significant increases in xylanase and beta-xylosidase specific activities were detected but no effect was detected on xylanase profiles in zymogram analyses. Similar responses were observed for two cultures originally derived from single-colony re-isolates. The most likely explanation for the observed adaptation involves selection for mutations affecting the regulation of xylanolytic enzymes.
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Affiliation(s)
- L Saluzzi
- Division of Gut Microbiology and Immunology, Rowett Research Institute, Bucksburn, AB21 9SB, Aberdeen, UK
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