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Kuil T, Yayo J, Pechan J, Küchler J, van Maris AJA. Ethanol tolerance of Clostridium thermocellum: the role of chaotropicity, temperature and pathway thermodynamics on growth and fermentative capacity. Microb Cell Fact 2022; 21:273. [PMID: 36567317 PMCID: PMC9790125 DOI: 10.1186/s12934-022-01999-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2022] [Accepted: 12/17/2022] [Indexed: 12/26/2022] Open
Abstract
BACKGROUND Clostridium thermocellum is a promising candidate for consolidated bioprocessing of lignocellulosic biomass to ethanol. The low ethanol tolerance of this microorganism is one of the remaining obstacles to industrial implementation. Ethanol inhibition can be caused by end-product inhibition and/or chaotropic-induced stress resulting in increased membrane fluidization and disruption of macromolecules. The highly reversible glycolysis of C. thermocellum might be especially sensitive to end-product inhibition. The chaotropic effect of ethanol is known to increase with temperature. This study explores the relative contributions of these two aspects to investigate and possibly mitigate ethanol-induced stress in growing and non-growing C. thermocellum cultures. RESULTS To separate chaotropic from thermodynamic effects of ethanol toxicity, a non-ethanol producing strain AVM062 (Pclo1313_2638::ldh* ∆adhE) was constructed by deleting the bifunctional acetaldehyde/alcohol dehydrogenase gene, adhE, in a lactate-overproducing strain. Exogenously added ethanol lowered the growth rate of both wild-type and the non-ethanol producing mutant. The mutant strain grew quicker than the wild-type at 50 and 55 °C for ethanol concentrations ≥ 10 g L-1 and was able to reach higher maximum OD600 at all ethanol concentrations and temperatures. For the wild-type, the maximum OD600 and relative growth rates were higher at 45 and 50 °C, compared to 55 °C, for ethanol concentrations ≥ 15 g L-1. For the mutant strain, no positive effect on growth was observed at lower temperatures. Growth-arrested cells of the wild-type demonstrated improved fermentative capacity over time in the presence of ethanol concentrations up to 40 g L-1 at 45 and 50 °C compared to 55 °C. CONCLUSION Positive effects of temperature on ethanol tolerance were limited to wild-type C. thermocellum and are likely related to mechanisms involved in the ethanol-formation pathway and redox cofactor balancing. Lowering the cultivation temperature provides an attractive strategy to improve growth and fermentative capacity at high ethanol titres in high-cellulose loading batch cultivations. Finally, non-ethanol producing strains are useful platform strains to study the effects of chaotropicity and thermodynamics related to ethanol toxicity and allow for deeper understanding of growth and/or fermentation cessation under industrially relevant conditions.
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Affiliation(s)
- Teun Kuil
- grid.5037.10000000121581746Department of Industrial Biotechnology, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Johannes Yayo
- grid.5037.10000000121581746Department of Industrial Biotechnology, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Johanna Pechan
- grid.5037.10000000121581746Department of Industrial Biotechnology, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Jan Küchler
- grid.5037.10000000121581746Department of Industrial Biotechnology, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, Stockholm, Sweden ,grid.5807.a0000 0001 1018 4307Present Address: Max Plank Institute for Dynamics of Complex Technical Systems, Otto-Von-Guericke-University Magdeburg, Magdeburg, Germany
| | - Antonius J. A. van Maris
- grid.5037.10000000121581746Department of Industrial Biotechnology, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, Stockholm, Sweden
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Maeno S, Nishimura H, Tanizawa Y, Dicks L, Arita M, Endo A. Unique niche-specific adaptation of fructophilic lactic acid bacteria and proposal of three Apilactobacillus species as novel members of the group. BMC Microbiol 2021; 21:41. [PMID: 33563209 PMCID: PMC7871557 DOI: 10.1186/s12866-021-02101-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2020] [Accepted: 01/20/2021] [Indexed: 02/01/2023] Open
Abstract
BACKGROUND Fructophilic lactic acid bacteria (FLAB) found in D-fructose rich niches prefer D-fructose over D-glucose as a growth substrate. They need electron acceptors for growth on D-glucose. The organisms share carbohydrate metabolic properties. Fructobacillus spp., Apilactobacillus kunkeei, and Apilactobacillus apinorum are members of this unique group. Here we studied the fructophilic characteristics of recently described species Apilactobacillus micheneri, Apilactobacillus quenuiae, and Apilactobacillus timberlakei. RESULTS The three species prefer D-fructose over D-glucose and only metabolize D-glucose in the presence of electron acceptors. The genomic characteristics of the three species, i.e. small genomes and thus a low number of coding DNA sequences, few genes involved in carbohydrate transport and metabolism, and partial deletion of adhE gene, are characteristic of FLAB. The three species thus are novel members of FLAB. Reduction of genes involved in carbohydrate transport and metabolism in accordance with reduction of genome size were the common characteristics of the family Lactobacillaceae, but FLAB markedly reduced the gene numbers more than other species in the family. Pan-genome analysis of genes involved in metabolism displayed a lack of specific carbohydrate metabolic pathways in FLAB, leading to a unique cluster separation. CONCLUSIONS The present study expanded FLAB group. Fructose-rich environments have induced similar evolution in phylogenetically distant FLAB species. These are examples of convergent evolution of LAB.
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Affiliation(s)
- Shintaro Maeno
- Department of Food, Aroma and Cosmetic Chemistry, Tokyo University of Agriculture, Abashiri, Hokkaido, 099-2493, Japan
| | - Hiroya Nishimura
- Department of Food, Aroma and Cosmetic Chemistry, Tokyo University of Agriculture, Abashiri, Hokkaido, 099-2493, Japan
| | - Yasuhiro Tanizawa
- Department of Informatics, National Institute of Genetics, Mishima, Shizuoka, 411-8540, Japan
| | - Leon Dicks
- Department of Microbiology, University of Stellenbosch, Matieland, Stellenbosch, 7602, South Africa
| | - Masanori Arita
- Department of Informatics, National Institute of Genetics, Mishima, Shizuoka, 411-8540, Japan
- RIKEN Center for Sustainable Resource Science, Yokohama, Kanagawa, 230-0045, Japan
| | - Akihito Endo
- Department of Food, Aroma and Cosmetic Chemistry, Tokyo University of Agriculture, Abashiri, Hokkaido, 099-2493, Japan.
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Holwerda EK, Olson DG, Ruppertsberger NM, Stevenson DM, Murphy SJL, Maloney MI, Lanahan AA, Amador-Noguez D, Lynd LR. Metabolic and evolutionary responses of Clostridium thermocellum to genetic interventions aimed at improving ethanol production. Biotechnol Biofuels 2020; 13:40. [PMID: 32175007 PMCID: PMC7063780 DOI: 10.1186/s13068-020-01680-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2019] [Accepted: 02/10/2020] [Indexed: 05/06/2023]
Abstract
BACKGROUND Engineering efforts targeted at increasing ethanol by modifying the central fermentative metabolism of Clostridium thermocellum have been variably successful. Here, we aim to understand this variation by a multifaceted approach including genomic and transcriptomic analysis combined with chemostat cultivation and high solids cellulose fermentation. Three strain lineages comprising 16 strains total were examined. Two strain lineages in which genes involved in pathways leading to organic acids and/or sporulation had been knocked out resulted in four end-strains after adaptive laboratory evolution (ALE). A third strain lineage recapitulated mutations involving adhE that occurred spontaneously in some of the engineered strains. RESULTS Contrary to lactate dehydrogenase, deleting phosphotransacetylase (pta, acetate) negatively affected steady-state biomass concentration and caused increased extracellular levels of free amino acids and pyruvate, while no increase in ethanol was detected. Adaptive laboratory evolution (ALE) improved growth and shifted elevated levels of amino acids and pyruvate towards ethanol, but not for all strain lineages. Three out of four end-strains produced ethanol at higher yield, and one did not. The occurrence of a mutation in the adhE gene, expanding its nicotinamide-cofactor compatibility, enabled two end-strains to produce more ethanol. A disruption in the hfsB hydrogenase is likely the reason why a third end-strain was able to make more ethanol. RNAseq analysis showed that the distribution of fermentation products was generally not regulated at the transcript level. At 120 g/L cellulose loadings, deletions of spo0A, ldh and pta and adaptive evolution did not negatively influence cellulose solubilization and utilization capabilities. Strains with a disruption in hfsB or a mutation in adhE produced more ethanol, isobutanol and 2,3-butanediol under these conditions and the highest isobutanol and ethanol titers reached were 5.1 and 29.9 g/L, respectively. CONCLUSIONS Modifications in the organic acid fermentative pathways in Clostridium thermocellum caused an increase in extracellular pyruvate and free amino acids. Adaptive laboratory evolution led to improved growth, and an increase in ethanol yield and production due a mutation in adhE or a disruption in hfsB. Strains with deletions in ldh and pta pathways and subjected to ALE demonstrated undiminished cellulolytic capabilities when cultured on high cellulose loadings.
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Affiliation(s)
- Evert K. Holwerda
- Thayer School of Engineering, Dartmouth College, Hanover, NH 03755 USA
- The Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
| | - Daniel G. Olson
- Thayer School of Engineering, Dartmouth College, Hanover, NH 03755 USA
- The Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
| | | | - David M. Stevenson
- Department of Bacteriology, University of Wisconsin, Madison, WI 53706 USA
- The Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
| | - Sean J. L. Murphy
- Thayer School of Engineering, Dartmouth College, Hanover, NH 03755 USA
| | - Marybeth I. Maloney
- Thayer School of Engineering, Dartmouth College, Hanover, NH 03755 USA
- The Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
| | - Anthony A. Lanahan
- Thayer School of Engineering, Dartmouth College, Hanover, NH 03755 USA
- The Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
| | - Daniel Amador-Noguez
- Department of Bacteriology, University of Wisconsin, Madison, WI 53706 USA
- The Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
| | - Lee R. Lynd
- Thayer School of Engineering, Dartmouth College, Hanover, NH 03755 USA
- The Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
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Maeno S, Tanizawa Y, Kajikawa A, Kanesaki Y, Kubota E, Arita M, Dicks L, Endo A. Pseudofructophilic Leuconostoc citreum Strain F192-5, Isolated from Satsuma Mandarin Peel. Appl Environ Microbiol 2019; 85:e01077-19. [PMID: 31399409 DOI: 10.1128/AEM.01077-19] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2019] [Accepted: 08/04/2019] [Indexed: 01/05/2023] Open
Abstract
Fructophilic lactic acid bacteria (FLAB), composed of Fructobacillus spp., Lactobacillus kunkeei, and Lactobacillus apinorum, are unique in that they prefer d-fructose over d-glucose as a carbon source. Strain F192-5, isolated from the peel of a satsuma mandarin and identified as Leuconostoc citreum, grows well on d-fructose but poorly on d-glucose and produces mainly lactate and acetate, with trace amounts of ethanol, from the metabolism of d-glucose. These characteristics are identical to those of obligate FLAB. However, strain F192-5 ferments a greater variety of carbohydrates than known FLAB. Comparative analyses of the genomes of strain F192-5 and reference strains of L. citreum revealed no signs of specific gene reductions, especially genes involved in carbohydrate transport and metabolism, in the genome of F192-5. The bifunctional alcohol/acetaldehyde dehydrogenase gene (adhE) is conserved in strain F192-5 but is not transcribed. This is most likely due to a deletion in the promoter region upstream of the adhE gene. Strain F192-5 did, however, ferment d-glucose when transformed with a plasmid containing the allochthonous adhE gene. L. citreum F192-5 is an example of a pseudo-FLAB strain with a deficiency in d-glucose metabolism. This unique phenotypic characteristic appears to be strain specific within the species L. citreum This might be one of the strategies lactic acid bacteria use to adapt to diverse environmental conditions.IMPORTANCE Obligate fructophilic lactic acid bacteria (FLAB) lack the metabolic pathways used in the metabolism of most carbohydrates and differ from other lactic acid bacteria in that they prefer to ferment d-fructose instead of d-glucose. These characteristics are well conserved at the genus or species level. Leuconostoc citreum F192-5 shows similar growth characteristics. However, the strain is metabolically and genomically different from obligate FLAB. This is an example of a strain that evolved a pseudo-FLAB phenotype to adapt to a fructose-rich environment.
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Maeno S, Kajikawa A, Dicks L, Endo A. Introduction of bifunctional alcohol/acetaldehyde dehydrogenase gene ( adhE) in Fructobacillus fructosus settled its fructophilic characteristics. Res Microbiol 2018; 170:35-42. [PMID: 30291951 DOI: 10.1016/j.resmic.2018.09.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2018] [Revised: 09/13/2018] [Accepted: 09/21/2018] [Indexed: 10/28/2022]
Abstract
Fructophilic lactic acid bacteria (FLAB) are unique in the sense that they prefer D-fructose over D-glucose as main carbon source. If D-glucose is metabolised, electron acceptors are required and significant levels of acetate are produced. These bacteria are found in environments rich in D-fructose, such as flowers, fruits and the gastrointestinal tract of insects feeding on fructose-rich diets. Fructobacillus spp. are representatives of this unique group, and their fructophilic characteristics are well conserved. In this study, the bifunctional alcohol/acetaldehyde dehydrogenase gene (adhE) from Leuconostoc mesenteroides NRIC 1541T was cloned into a plasmid and transferred to Fructobacillus fructosus NRIC 1058T. Differences in biochemical characteristics between the parental strain (NRIC 1058T) and the transformants were compared. Strain 1-11, transformed with the adhE gene, did not show any fructophilic characteristics, and the strain grew well on D-glucose without external electron acceptors. Accumulation of acetic acid, which was originally seen in the parental strain, was replaced with ethanol in the transformed strain. Furthermore, in silico analyses revealed that strain NRIC 1058T lacked the sugar transporters/permeases and enzymes required for conversion of metabolic intermediates. This may be the reason for poor carbohydrate metabolic properties recorded for FLAB.
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Affiliation(s)
- Shintaro Maeno
- Department of Food, Aroma and Cosmetic Chemistry, Tokyo University of Agriculture, 099-2493, Hokkaido, Japan.
| | - Akinobu Kajikawa
- Department of Agricultural Chemistry, Tokyo University of Agriculture, 156-0083, Tokyo, Japan.
| | - Leon Dicks
- Department of Microbiology, University of Stellenbosch, Private Bag X1, 7602, Matieland, South Africa.
| | - Akihito Endo
- Department of Food, Aroma and Cosmetic Chemistry, Tokyo University of Agriculture, 099-2493, Hokkaido, Japan.
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Yu Y, Qian Y, Du D, Li Q, Xu C, Liu H, Chen M, Yao H, Lu C, Zhang W. Infection and adaption-based proteomic changes of Streptococcus suis serotype 2 in a pig model. J Proteomics 2017; 180:41-52. [PMID: 29247804 DOI: 10.1016/j.jprot.2017.12.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2017] [Revised: 11/10/2017] [Accepted: 12/01/2017] [Indexed: 12/28/2022]
Abstract
Streptococcus suis (S. suis) is an emerging zoonotic agent that is responsible for significant economic losses to the porcine industry worldwide. However, most research regarding the pathogenic mechanisms has used in vitro cultures of S. suis, which may not provide an accurate representation of the in vivo biological activities. In this study, 188 differential abundance S. suis proteins were identified in in vivo samples obtained from the blood of the infected pigs. These were compared with in vitro samples by a Tandem Mass Tags (TMT) experiment. Thus, a virulence associated network was established using the enriched differential abundance proteins (obtained via bioinformatics analysis in this study) and the previously reported putative virulence factors associated with in vivo infection. One of the most important up-regulated hubs in this network, adhE (an acetaldehyde-CoA/alcohol dehydrogenase) was found. Furthermore, knocking out adhE in S. suis serotype 2 strain ZY05719 decreased virulence. Cell culture experiments and far-western blot analysis showed that adhE is involved in adhesion to Caco-2 cells; Hsp60 could be one of the receptors for this protein. SIGNIFICANCE This study is a systematical research to identify in vivo regulated virulence associated proteins of S. suis in pigs. It constructs a network consisting of in vivo infection related factors for the first time to get to know the coordinated actions of a multitude of factors that lead to host pathogenicity and filter the most important hubs. The individual factors that contribute to infection is also identified. A novel differential protein adhE which is one of the most important hubs of this network and is up-regulated in abundance in vivo is found to moonlight as an important adhesion by binding Hsp60 and finally contributes to virulence.
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Affiliation(s)
- Yanfei Yu
- Key Lab of Animal Bacteriology of Ministry of Agriculture, College of Veterinary Medicine & OIE Swine Streptococcosis Diagnostic Laboratory, Nanjing Agricultural University, Nanjing 210095, China; Institute of Veterinary Medicine, Jiangsu Academy of Agricultural Sciences, Key Laboratory of Veterinary Biological Engineering and Technology, Ministry of Agriculture, National Center for Engineering Research of Veterinary Bio-products, Nanjing 210014, China
| | - Yunyun Qian
- Key Lab of Animal Bacteriology of Ministry of Agriculture, College of Veterinary Medicine & OIE Swine Streptococcosis Diagnostic Laboratory, Nanjing Agricultural University, Nanjing 210095, China.
| | - Dechao Du
- Key Lab of Animal Bacteriology of Ministry of Agriculture, College of Veterinary Medicine & OIE Swine Streptococcosis Diagnostic Laboratory, Nanjing Agricultural University, Nanjing 210095, China.
| | - Quan Li
- Key Lab of Animal Bacteriology of Ministry of Agriculture, College of Veterinary Medicine & OIE Swine Streptococcosis Diagnostic Laboratory, Nanjing Agricultural University, Nanjing 210095, China.
| | - Chenyang Xu
- Key Lab of Animal Bacteriology of Ministry of Agriculture, College of Veterinary Medicine & OIE Swine Streptococcosis Diagnostic Laboratory, Nanjing Agricultural University, Nanjing 210095, China.
| | - Hanze Liu
- Key Lab of Animal Bacteriology of Ministry of Agriculture, College of Veterinary Medicine & OIE Swine Streptococcosis Diagnostic Laboratory, Nanjing Agricultural University, Nanjing 210095, China.
| | - Mianmian Chen
- Key Lab of Animal Bacteriology of Ministry of Agriculture, College of Veterinary Medicine & OIE Swine Streptococcosis Diagnostic Laboratory, Nanjing Agricultural University, Nanjing 210095, China.
| | - Huochun Yao
- Key Lab of Animal Bacteriology of Ministry of Agriculture, College of Veterinary Medicine & OIE Swine Streptococcosis Diagnostic Laboratory, Nanjing Agricultural University, Nanjing 210095, China.
| | - Chengping Lu
- Key Lab of Animal Bacteriology of Ministry of Agriculture, College of Veterinary Medicine & OIE Swine Streptococcosis Diagnostic Laboratory, Nanjing Agricultural University, Nanjing 210095, China.
| | - Wei Zhang
- Key Lab of Animal Bacteriology of Ministry of Agriculture, College of Veterinary Medicine & OIE Swine Streptococcosis Diagnostic Laboratory, Nanjing Agricultural University, Nanjing 210095, China.
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Wang S, Dong S, Wang Y. Enhancement of solvent production by overexpressing key genes of the acetone-butanol-ethanol fermentation pathway in Clostridium saccharoperbutylacetonicum N1-4. Bioresour Technol 2017; 245:426-433. [PMID: 28898840 DOI: 10.1016/j.biortech.2017.09.024] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2017] [Revised: 09/03/2017] [Accepted: 09/04/2017] [Indexed: 05/24/2023]
Abstract
Clostridium saccharoperbutylacetonicum N1-4 is well known as a hyper-butanol producing strain. However, little information is available concerning its butanol production mechanism and the development of more robust strains. In this study, key biosynthetic genes (either endogenous or exogenous) including the sol operon (bld-ctfA-ctfB-adc), adhE1, adhE1D485G, thl, thlA1V5A, thlAV5A and the expression cassette EC (thl-hbd-crt-bcd) were overexpressed in C. saccharoperbutylacetonicum N1-4 to evaluate their potential in enhancement of butanol production. The overexpression of sol operon increased ethanol production by 400%. The overexpression of adhE1 and adhED485G resulted in a 5.6- and 4.9-fold higher ethanol production, respectively, producing final acetone-butanol-ethanol (ABE) titers (30.6 and 30.1gL-1) of among the highest as ever reported for solventogenic clostridia. The most significant increase of butanol production (by 13.7%) and selectivity (73.7%) was achieved by the overexpression of EC. These results provides a solid foundation and essential references for the further development of more robust strains.
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Affiliation(s)
- Shaohua Wang
- Department of Biosystems Engineering, Auburn University, Auburn, AL 36849, USA
| | - Sheng Dong
- Department of Biosystems Engineering, Auburn University, Auburn, AL 36849, USA
| | - Yi Wang
- Department of Biosystems Engineering, Auburn University, Auburn, AL 36849, USA; Center for Bioenergy and Bioproducts, Auburn University, Auburn, AL 36849, USA.
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Hon S, Lanahan AA, Tian L, Giannone RJ, Hettich RL, Olson DG, Lynd LR. Development of a plasmid-based expression system in Clostridium thermocellum and its use to screen heterologous expression of bifunctional alcohol dehydrogenases ( adhEs). Metab Eng Commun 2016; 3:120-129. [PMID: 29142822 PMCID: PMC5678826 DOI: 10.1016/j.meteno.2016.04.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2015] [Revised: 03/15/2016] [Accepted: 04/21/2016] [Indexed: 12/27/2022] Open
Abstract
Clostridium thermocellum is a promising candidate for ethanol production from cellulosic biomass, but requires metabolic engineering to improve ethanol yield. A key gene in the ethanol production pathway is the bifunctional aldehyde and alcohol dehydrogenase, adhE. To explore the effects of overexpressing wild-type, mutant, and exogenous adhEs, we developed a new expression plasmid, pDGO144, that exhibited improved transformation efficiency and better gene expression than its predecessor, pDGO-66. This new expression plasmid will allow for many other metabolic engineering and basic research efforts in C. thermocellum. As proof of concept, we used this plasmid to express 12 different adhE genes (both wild type and mutant) from several organisms. Ethanol production varied between clones immediately after transformation, but tended to converge to a single value after several rounds of serial transfer. The previously described mutant C. thermocellum D494G adhE gave the best ethanol production, which is consistent with previously published results.
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Affiliation(s)
- Shuen Hon
- Thayer School of Engineering, Dartmouth College, Hanover, NH, USA
- BioEnergy Science Center, Oak Ridge, TN, USA
| | - Anthony A. Lanahan
- Thayer School of Engineering, Dartmouth College, Hanover, NH, USA
- BioEnergy Science Center, Oak Ridge, TN, USA
| | - Liang Tian
- Thayer School of Engineering, Dartmouth College, Hanover, NH, USA
- BioEnergy Science Center, Oak Ridge, TN, USA
| | - Richard J. Giannone
- BioEnergy Science Center, Oak Ridge, TN, USA
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - Robert L. Hettich
- BioEnergy Science Center, Oak Ridge, TN, USA
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - Daniel G. Olson
- Thayer School of Engineering, Dartmouth College, Hanover, NH, USA
- BioEnergy Science Center, Oak Ridge, TN, USA
| | - Lee R. Lynd
- Thayer School of Engineering, Dartmouth College, Hanover, NH, USA
- BioEnergy Science Center, Oak Ridge, TN, USA
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Maeno S, Tanizawa Y, Kanesaki Y, Kubota E, Kumar H, Dicks L, Salminen S, Nakagawa J, Arita M, Endo A. Genomic characterization of a fructophilic bee symbiont Lactobacillus kunkeei reveals its niche-specific adaptation. Syst Appl Microbiol 2016; 39:516-526. [PMID: 27776911 DOI: 10.1016/j.syapm.2016.09.006] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2016] [Revised: 09/20/2016] [Accepted: 09/21/2016] [Indexed: 02/02/2023]
Abstract
Lactobacillus kunkeei is classified as a sole obligate fructophilic lactic acid bacterium that is found in fructose-rich niches, including the guts of honeybees. The species is differentiated from other lactobacilli based on its poor growth with glucose, enhanced growth in the presence of oxygen and other electron acceptors, and production of high concentrations of acetate from the metabolism of glucose. These characteristics are similar to phylogenetically distant Fructobacillus spp. In the present study, the genomic structure of L. kunkeei was characterized by using 16 different strains, and it had significantly less genes and smaller genomes when compared with other lactobacilli. Functional gene classification revealed that L. kunkeei had lost genes specifically involved in carbohydrate transport and metabolism. The species also lacked most of the genes for respiration, although growth was enhanced in the presence of oxygen. The adhE gene of L. kunkeei, encoding a bifunctional alcohol dehydrogenase (ADH)/aldehyde dehydrogenase (ALDH) protein, lacked the part encoding the ADH domain, which is reported here for the first time in lactic acid bacteria. The deletion resulted in the lack of ADH activity, implying a requirement for electron acceptors in glucose assimilation. These results clearly indicated that L. kunkeei had undergone a specific reductive evolution in order to adapt to fructose-rich environments. The reduction characteristics were similar to those of Fructobacillus spp., but distinct from other lactobacilli with small genomes, such as Lactobacillus gasseri and Lactobacillus vaginalis. Fructose-richness thus induced an environment-specific gene reduction in phylogenetically distant microorganisms.
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Affiliation(s)
- Shintaro Maeno
- Department of Food and Cosmetic Science, Tokyo University of Agriculture, Hokkaido, Japan
| | - Yasuhiro Tanizawa
- Department of Computational Biology and Medical Sciences, Graduate School of Frontier Science, The University of Tokyo, Chiba, Japan; Center for Information Biology, National Institute of Genetics, Shizuoka, Japan
| | - Yu Kanesaki
- Genome Research Center, NODAI Research Institute, Tokyo University of Agriculture, Tokyo, Japan
| | - Eri Kubota
- Genome Research Center, NODAI Research Institute, Tokyo University of Agriculture, Tokyo, Japan
| | - Himanshu Kumar
- Functional Foods Forum, University of Turku, Turku, Finland
| | - Leon Dicks
- Department of Microbiology, University of Stellenbosch, Stellenbosch, South Africa
| | - Seppo Salminen
- Functional Foods Forum, University of Turku, Turku, Finland
| | - Junichi Nakagawa
- Department of Food and Cosmetic Science, Tokyo University of Agriculture, Hokkaido, Japan
| | - Masanori Arita
- Center for Information Biology, National Institute of Genetics, Shizuoka, Japan; RIKEN Center for Sustainable Resource Science, Kanagawa, Japan
| | - Akihito Endo
- Department of Food and Cosmetic Science, Tokyo University of Agriculture, Hokkaido, Japan.
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