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Abstract
Clostridium botulinum, a polyphyletic Gram-positive taxon of bacteria, is classified purely by their ability to produce botulinum neurotoxin (BoNT). BoNT is the primary virulence factor and the causative agent of botulism. A potentially fatal disease, botulism is classically characterized by a symmetrical descending flaccid paralysis, which is left untreated can lead to respiratory failure and death. Botulism cases are classified into three main forms dependent on the nature of intoxication; foodborne, wound and infant. The BoNT, regarded as the most potent biological substance known, is a zinc metalloprotease that specifically cleaves SNARE proteins at neuromuscular junctions, preventing exocytosis of neurotransmitters, leading to muscle paralysis. The BoNT is now used to treat numerous medical conditions caused by overactive or spastic muscles and is extensively used in the cosmetic industry due to its high specificity and the exceedingly small doses needed to exert long-lasting pharmacological effects. Additionally, the ability to form endospores is critical to the pathogenicity of the bacteria. Disease transmission is often facilitated via the metabolically dormant spores that are highly resistant to environment stresses, allowing persistence in the environment in unfavourable conditions. Infant and wound botulism infections are initiated upon germination of the spores into neurotoxin producing vegetative cells, whereas foodborne botulism is attributed to ingestion of preformed BoNT. C. botulinum is a saprophytic bacterium, thought to have evolved its potent neurotoxin to establish a source of nutrients by killing its host.
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Affiliation(s)
- Alexander M Rawson
- Clostridia Research Group, BBSRC/EPSRC Synthetic Biology Research Centre (SBRC), School of Life Sciences, The Biodiscovery Institute, The University of Nottingham, Nottingham, UK
| | - Andrew W Dempster
- Clostridia Research Group, BBSRC/EPSRC Synthetic Biology Research Centre (SBRC), School of Life Sciences, The Biodiscovery Institute, The University of Nottingham, Nottingham, UK
| | - Christopher M Humphreys
- Clostridia Research Group, BBSRC/EPSRC Synthetic Biology Research Centre (SBRC), School of Life Sciences, The Biodiscovery Institute, The University of Nottingham, Nottingham, UK
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Seys FM, Humphreys CM, Tomi-Andrino C, Li Q, Millat T, Yang S, Minton NP. Base editing enables duplex point mutagenesis in Clostridium autoethanogenum at the price of numerous off-target mutations. Front Bioeng Biotechnol 2023; 11:1211197. [PMID: 37496853 PMCID: PMC10366002 DOI: 10.3389/fbioe.2023.1211197] [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: 04/24/2023] [Accepted: 06/06/2023] [Indexed: 07/28/2023] Open
Abstract
Base editors are recent multiplex gene editing tools derived from the Cas9 nuclease of Streptomyces pyogenes. They can target and modify a single nucleotide in the genome without inducing double-strand breaks (DSB) of the DNA helix. As such, they hold great potential for the engineering of microbes that lack effective DSB repair pathways such as homologous recombination (HR) or non-homologous end-joining (NHEJ). However, few applications of base editors have been reported in prokaryotes to date, and their advantages and drawbacks have not been systematically reported. Here, we used the base editors Target-AID and Target-AID-NG to introduce nonsense mutations into four different coding sequences of the industrially relevant Gram-positive bacterium Clostridium autoethanogenum. While up to two loci could be edited simultaneously using a variety of multiplexing strategies, most colonies exhibited mixed genotypes and most available protospacers led to undesired mutations within the targeted editing window. Additionally, fifteen off-target mutations were detected by sequencing the genome of the resulting strain, among them seven single-nucleotide polymorphisms (SNP) in or near loci bearing some similarity with the targeted protospacers, one 15 nt duplication, and one 12 kb deletion which removed uracil DNA glycosylase (UDG), a key DNA repair enzyme thought to be an obstacle to base editing mutagenesis. A strategy to process prokaryotic single-guide RNA arrays by exploiting tRNA maturation mechanisms is also illustrated.
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Affiliation(s)
- François M. Seys
- Clostridia Research Group, BBSRC/EPSRC Synthetic Biology Research Centre (SBRC), School of Life Sciences, Biodiscovery Institute, University of Nottingham, Nottingham, United Kingdom
| | - Christopher M. Humphreys
- Clostridia Research Group, BBSRC/EPSRC Synthetic Biology Research Centre (SBRC), School of Life Sciences, Biodiscovery Institute, University of Nottingham, Nottingham, United Kingdom
| | - Claudio Tomi-Andrino
- Clostridia Research Group, BBSRC/EPSRC Synthetic Biology Research Centre (SBRC), School of Life Sciences, Biodiscovery Institute, University of Nottingham, Nottingham, United Kingdom
- Centre for Analytical Bioscience, Advanced Materials and Healthcare Technologies Division, School of Pharmacy, University of Nottingham, Nottingham, United Kingdom
- Nottingham BBSRC/EPSRC Synthetic Biology Research Centre (SBRC), School of Mathematical Sciences, University of Nottingham, Nottingham, United Kingdom
| | - Qi Li
- College of Life Sciences, Sichuan Normal University, Chengdu, China
| | - Thomas Millat
- Clostridia Research Group, BBSRC/EPSRC Synthetic Biology Research Centre (SBRC), School of Life Sciences, Biodiscovery Institute, University of Nottingham, Nottingham, United Kingdom
| | - Sheng Yang
- Key Laboratory of Synthetic Biology, CAS Center for Excellence in Molecular Plant Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Nigel P. Minton
- Clostridia Research Group, BBSRC/EPSRC Synthetic Biology Research Centre (SBRC), School of Life Sciences, Biodiscovery Institute, University of Nottingham, Nottingham, United Kingdom
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Bourgade B, Humphreys CM, Millard J, Minton NP, Islam MA. Design, Analysis, and Implementation of a Novel Biochemical Pathway for Ethylene Glycol Production in Clostridium autoethanogenum. ACS Synth Biol 2022; 11:1790-1800. [PMID: 35543716 PMCID: PMC9127970 DOI: 10.1021/acssynbio.1c00624] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [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] [Indexed: 01/26/2023]
Abstract
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The platform chemical
ethylene glycol (EG) is used to manufacture
various commodity chemicals of industrial importance, but largely
remains synthesized from fossil fuels. Although several novel metabolic
pathways have been reported for its bioproduction in model organisms,
none has been reported for gas-fermenting, non-model acetogenic chassis
organisms. Here, we describe a novel, synthetic biochemical pathway
to convert acetate into EG in the industrially important gas-fermenting
acetogen,Clostridium autoethanogenum. We not only developed a computational workflow to design and analyze
hundreds of novel biochemical pathways for EG production but also
demonstrated a successful pathway construction in the chosen host.
The EG production was achieved using a two-plasmid system to bypass
unfeasible expression levels and potential toxic enzymatic interactions.
Although only a yield of 0.029 g EG/g fructose was achieved and therefore
requiring further strain engineering efforts to optimize the designed
strain, this work demonstrates an important proof-of-concept approach
to computationally design and experimentally implement fully synthetic
metabolic pathways in a metabolically highly specific, non-model host
organism.
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Affiliation(s)
- Barbara Bourgade
- Department of Chemical Engineering, Loughborough University, Loughborough LE11 3TU, U.K
| | - Christopher M. Humphreys
- BBSRC/EPSRC Synthetic Biology Research Centre, Biodiscovery Institute, University of Nottingham, Nottingham NG7 2RD, U.K
| | - James Millard
- BBSRC/EPSRC Synthetic Biology Research Centre, Biodiscovery Institute, University of Nottingham, Nottingham NG7 2RD, U.K
| | - Nigel P. Minton
- BBSRC/EPSRC Synthetic Biology Research Centre, Biodiscovery Institute, University of Nottingham, Nottingham NG7 2RD, U.K
| | - M. Ahsanul Islam
- Department of Chemical Engineering, Loughborough University, Loughborough LE11 3TU, U.K
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Seys FM, Rowe P, Bolt EL, Humphreys CM, Minton NP. A Gold Standard, CRISPR/Cas9-Based Complementation Strategy Reliant on 24 Nucleotide Bookmark Sequences. Genes (Basel) 2020; 11:genes11040458. [PMID: 32340238 PMCID: PMC7230483 DOI: 10.3390/genes11040458] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Revised: 04/09/2020] [Accepted: 04/20/2020] [Indexed: 12/17/2022] Open
Abstract
Phenotypic complementation of gene knockouts is an essential step in establishing function. Here, we describe a simple strategy for ‘gold standard’ complementation in which the mutant allele is replaced in situ with a wild type (WT) allele in a procedure that exploits CRISPR/Cas9. The method relies on the prior incorporation of a unique 24 nucleotide (nt) ‘bookmark’ sequence into the mutant allele to act as a guide RNA target during its Cas9-mediated replacement with the WT allele. The bookmark comprises a 23 nt Cas9 target sequence plus an additional nt to ensure the deletion is in-frame. Here, bookmarks are tailored to Streptococcus pyogenes CRISPR/Cas9 but could be designed for any CRISPR/Cas system. For proof of concept, nine bookmarks were tested in Clostridium autoethanogenum. Complementation efficiencies reached 91%. As complemented strains are indistinguishable from their progenitors, concerns over contamination may be satisfied by the incorporation of ‘watermark’ sequences into the complementing genes.
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Affiliation(s)
- François M. Seys
- Clostridia Research Group, BBSRC/EPSRC Synthetic Biology Research Centre (SBRC), School of Life Sciences, Biodiscovery Institute, University of Nottingham, Nottingham NG7 2RD, UK; (F.M.S.); (P.R.); (C.M.H.)
| | - Peter Rowe
- Clostridia Research Group, BBSRC/EPSRC Synthetic Biology Research Centre (SBRC), School of Life Sciences, Biodiscovery Institute, University of Nottingham, Nottingham NG7 2RD, UK; (F.M.S.); (P.R.); (C.M.H.)
| | - Edward L. Bolt
- School of Life Sciences, Queen’s Medical Centre, Nottingham NG7 2UH, UK;
| | - Christopher M. Humphreys
- Clostridia Research Group, BBSRC/EPSRC Synthetic Biology Research Centre (SBRC), School of Life Sciences, Biodiscovery Institute, University of Nottingham, Nottingham NG7 2RD, UK; (F.M.S.); (P.R.); (C.M.H.)
| | - Nigel P. Minton
- Clostridia Research Group, BBSRC/EPSRC Synthetic Biology Research Centre (SBRC), School of Life Sciences, Biodiscovery Institute, University of Nottingham, Nottingham NG7 2RD, UK; (F.M.S.); (P.R.); (C.M.H.)
- NIHR Nottingham Biomedical Research Centre, Nottingham University Hospitals NHS Trust, Nottingham NG7 2RD, UK
- Correspondence: ; Tel.: +44-(0)115-846-7458
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Woods C, Humphreys CM, Rodrigues RM, Ingle P, Rowe P, Henstra AM, Köpke M, Simpson SD, Winzer K, Minton NP. A novel conjugal donor strain for improved DNA transfer into Clostridium spp. Anaerobe 2019; 59:184-191. [PMID: 31269456 PMCID: PMC6866869 DOI: 10.1016/j.anaerobe.2019.06.020] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Revised: 06/27/2019] [Accepted: 06/29/2019] [Indexed: 12/29/2022]
Abstract
Clostridium encompasses species which are relevant to human and animal disease as well as species which have industrial potential, for instance, as producers of chemicals and fuels or as tumour delivery vehicles. Genetic manipulation of these target organisms is critical for advances in these fields. DNA transfer efficiencies, however, vary between species. Low efficiencies can impede the progress of research efforts. A novel conjugal donor strain of Escherichia coli has been created which exhibits a greater than 10-fold increases in conjugation efficiency compared to the traditionally used CA434 strain in the three species tested; C. autoethanogenum DSM 10061, C. sporogenes NCIMB 10696 and C. difficile R20291. The novel strain, designated 'sExpress', does not methylate DNA at Dcm sites (CCWGG) which allows circumvention of cytosine-specific Type IV restriction systems. A robust protocol for conjugation is presented which routinely produces in the order of 105 transconjugants per millilitre of donor cells for C. autoethanogenum, 106 for C. sporogenes and 102 for C. difficile R20291. The novel strain created is predicted to be a superior conjugal donor in a wide range of species which possess Type IV restriction systems.
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Affiliation(s)
- Craig Woods
- Clostridia Research Group, BBSRC/EPSRC Synthetic Biology Research Centre (SBRC), School of Life Sciences, The University of Nottingham, Nottingham, NG7 2RD, UK
| | - Christopher M Humphreys
- Clostridia Research Group, BBSRC/EPSRC Synthetic Biology Research Centre (SBRC), School of Life Sciences, The University of Nottingham, Nottingham, NG7 2RD, UK
| | - Raquel Mesquita Rodrigues
- Clostridia Research Group, BBSRC/EPSRC Synthetic Biology Research Centre (SBRC), School of Life Sciences, The University of Nottingham, Nottingham, NG7 2RD, UK
| | - Patrick Ingle
- Clostridia Research Group, BBSRC/EPSRC Synthetic Biology Research Centre (SBRC), School of Life Sciences, The University of Nottingham, Nottingham, NG7 2RD, UK
| | - Peter Rowe
- Clostridia Research Group, BBSRC/EPSRC Synthetic Biology Research Centre (SBRC), School of Life Sciences, The University of Nottingham, Nottingham, NG7 2RD, UK
| | - Anne M Henstra
- Clostridia Research Group, BBSRC/EPSRC Synthetic Biology Research Centre (SBRC), School of Life Sciences, The University of Nottingham, Nottingham, NG7 2RD, UK
| | - Michael Köpke
- LanzaTech Inc., 8045 Lamon Avenue, Suite 400, Skokie, IL, USA
| | - Sean D Simpson
- LanzaTech Inc., 8045 Lamon Avenue, Suite 400, Skokie, IL, USA
| | - Klaus Winzer
- Clostridia Research Group, BBSRC/EPSRC Synthetic Biology Research Centre (SBRC), School of Life Sciences, The University of Nottingham, Nottingham, NG7 2RD, UK
| | - Nigel P Minton
- Clostridia Research Group, BBSRC/EPSRC Synthetic Biology Research Centre (SBRC), School of Life Sciences, The University of Nottingham, Nottingham, NG7 2RD, UK; NIHR Nottingham Biomedical Research Centre, Nottingham University Hospitals NHS Trust and the University of Nottingham, Nottingham NG7 2RD, UK.
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Annan FJ, Al-Sinawi B, Humphreys CM, Norman R, Winzer K, Köpke M, Simpson SD, Minton NP, Henstra AM. Engineering of vitamin prototrophy in Clostridium ljungdahlii and Clostridium autoethanogenum. Appl Microbiol Biotechnol 2019; 103:4633-4648. [PMID: 30972463 PMCID: PMC6505512 DOI: 10.1007/s00253-019-09763-6] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Revised: 02/19/2019] [Accepted: 03/12/2019] [Indexed: 11/30/2022]
Abstract
Clostridium autoethanogenum and Clostridium ljungdahlii are physiologically and genetically very similar strict anaerobic acetogens capable of growth on carbon monoxide as sole carbon source. While exact nutritional requirements have not been reported, we observed that for growth, the addition of vitamins to media already containing yeast extract was required, an indication that these are fastidious microorganisms. Elimination of complex components and individual vitamins from the medium revealed that the only organic compounds required for growth were pantothenate, biotin and thiamine. Analysis of the genome sequences revealed that three genes were missing from pantothenate and thiamine biosynthetic pathways, and five genes were absent from the pathway for biotin biosynthesis. Prototrophy in C. autoethanogenum and C. ljungdahlii for pantothenate was obtained by the introduction of plasmids carrying the heterologous gene clusters panBCD from Clostridium acetobutylicum, and for thiamine by the introduction of the thiC-purF operon from Clostridium ragsdalei. Integration of panBCD into the chromosome through allele-coupled exchange also conveyed prototrophy. C. autoethanogenum was converted to biotin prototrophy with gene sets bioBDF and bioHCA from Desulfotomaculum nigrificans strain CO-1-SRB, on plasmid and integrated in the chromosome. The genes could be used as auxotrophic selection markers in recombinant DNA technology. Additionally, transformation with a subset of the genes for pantothenate biosynthesis extended selection options with the pantothenate precursors pantolactone and/or beta-alanine. Similarly, growth was obtained with the biotin precursor pimelate combined with genes bioYDA from C. acetobutylicum. The work raises questions whether alternative steps exist in biotin and thiamine biosynthesis pathways in these acetogens.
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Affiliation(s)
- Florence J Annan
- BBSRC/EPSRC Synthetic Biology Research Centre, School of Life Sciences, University of Nottingham, Nottingham, NG7 2RD, UK
| | - Bakir Al-Sinawi
- University of New-South Wales (UNSW) Sydney, Kensington, Australia
| | - Christopher M Humphreys
- BBSRC/EPSRC Synthetic Biology Research Centre, School of Life Sciences, University of Nottingham, Nottingham, NG7 2RD, UK
| | - Rupert Norman
- BBSRC/EPSRC Synthetic Biology Research Centre, School of Life Sciences, University of Nottingham, Nottingham, NG7 2RD, UK
| | - Klaus Winzer
- BBSRC/EPSRC Synthetic Biology Research Centre, School of Life Sciences, University of Nottingham, Nottingham, NG7 2RD, UK
| | - Michael Köpke
- LanzaTech Inc., 8045 Lamon Avenue, Suite 400, Skokie, IL, USA
| | - Sean D Simpson
- LanzaTech Inc., 8045 Lamon Avenue, Suite 400, Skokie, IL, USA
| | - Nigel P Minton
- BBSRC/EPSRC Synthetic Biology Research Centre, School of Life Sciences, University of Nottingham, Nottingham, NG7 2RD, UK
| | - Anne M Henstra
- BBSRC/EPSRC Synthetic Biology Research Centre, School of Life Sciences, University of Nottingham, Nottingham, NG7 2RD, UK.
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Ingle P, Groothuis D, Rowe P, Huang H, Cockayne A, Kuehne SA, Jiang W, Gu Y, Humphreys CM, Minton NP. Generation of a fully erythromycin-sensitive strain of Clostridioides difficile using a novel CRISPR-Cas9 genome editing system. Sci Rep 2019; 9:8123. [PMID: 31148548 PMCID: PMC6544763 DOI: 10.1038/s41598-019-44458-y] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Accepted: 05/14/2019] [Indexed: 12/26/2022] Open
Abstract
Understanding the molecular pathogenesis of Clostridioides difficile has relied on the use of ermB-based mutagens in erythromycin-sensitive strains. However, the repeated subcultures required to isolate sensitive variants can lead to the acquisition of ancillary mutations that affect phenotype, including virulence. CRISPR-Cas9 allows the direct selection of mutants, reducing the number of subcultures and thereby minimising the likelihood of acquiring additional mutations. Accordingly, CRISPR-Cas9 was used to sequentially remove from the C. difficile 630 reference strain (NCTC 13307) two ermB genes and pyrE. The genomes of the strains generated (630Δerm* and 630Δerm*ΔpyrE, respectively) contained no ancillary mutations compared to the NCTC 13307 parental strain, making these strains the preferred option where erythromycin-sensitive 630 strains are required. Intriguingly, the cas9 gene of the plasmid used contained a proximal frameshift mutation. Despite this, the frequency of mutant isolation was high (96% and 89% for ermB and pyrE, respectively) indicating that a functional Cas9 is still being produced. Re-initiation of translation from an internal AUG start codon would produce a foreshortened protein lacking a RuvCI nucleolytic domain, effectively a 'nickase'. The mutation allowed cas9 to be cloned downstream of the strong Pthl promoter. It may find application elsewhere where the use of strong, constitutive promoters is preferred.
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Affiliation(s)
- Patrick Ingle
- Clostridia Research Group, BBSRC/EPSRC Synthetic Biology Research Centre (SBRC), School of Life Sciences, The University of Nottingham, Nottingham, NG7 2RD, UK
| | - Daphne Groothuis
- Clostridia Research Group, BBSRC/EPSRC Synthetic Biology Research Centre (SBRC), School of Life Sciences, The University of Nottingham, Nottingham, NG7 2RD, UK
| | - Peter Rowe
- Clostridia Research Group, BBSRC/EPSRC Synthetic Biology Research Centre (SBRC), School of Life Sciences, The University of Nottingham, Nottingham, NG7 2RD, UK
- Deep Branch Biotechnology, NG8 1AA, Nottingham, United Kingdom
| | - He Huang
- Key Laboratory of Synthetic Biology, CAS Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, 200032, China
| | - Alan Cockayne
- Clostridia Research Group, BBSRC/EPSRC Synthetic Biology Research Centre (SBRC), School of Life Sciences, The University of Nottingham, Nottingham, NG7 2RD, UK
| | - Sarah A Kuehne
- Clostridia Research Group, BBSRC/EPSRC Synthetic Biology Research Centre (SBRC), School of Life Sciences, The University of Nottingham, Nottingham, NG7 2RD, UK
- School of Dentistry, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham, B5 7SA, UK
| | - Weihong Jiang
- Key Laboratory of Synthetic Biology, CAS Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, 200032, China
| | - Yang Gu
- Key Laboratory of Synthetic Biology, CAS Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, 200032, China
| | - Christopher M Humphreys
- Clostridia Research Group, BBSRC/EPSRC Synthetic Biology Research Centre (SBRC), School of Life Sciences, The University of Nottingham, Nottingham, NG7 2RD, UK
| | - Nigel P Minton
- Clostridia Research Group, BBSRC/EPSRC Synthetic Biology Research Centre (SBRC), School of Life Sciences, The University of Nottingham, Nottingham, NG7 2RD, UK.
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Humphreys CM, Minton NP. Advances in metabolic engineering in the microbial production of fuels and chemicals from C1 gas. Curr Opin Biotechnol 2018; 50:174-181. [PMID: 29414057 DOI: 10.1016/j.copbio.2017.12.023] [Citation(s) in RCA: 58] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Revised: 12/21/2017] [Accepted: 12/22/2017] [Indexed: 12/20/2022]
Abstract
The future sustainable production of chemicals and fuels from non-petrochemical sources, while at the same time reducing greenhouse gas (GHG) emissions, represent two of society's greatest challenges. Microbial chassis able to grow on waste carbon monoxide (CO) and carbon dioxide (CO2) can provide solutions to both. Ranging from the anaerobic acetogens, through the aerobic chemoautotrophs to the photoautotrophic cyanobacteria, they are able to convert C1 gases into a range of chemicals and fuels which may be enhanced and extended through appropriate metabolic engineering. The necessary improvements will be facilitated by the increasingly sophisticated gene tools that are beginning to emerge as part of the Synthetic Biology revolution. These tools, in combination with more accurate metabolic and genome scale models, will enable C1 chassis to deliver their full potential.
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Affiliation(s)
- Christopher M Humphreys
- BBSRC/EPSRC Synthetic Biology Research Centre, School of Life Sciences, University Park, University of Nottingham, Nottingham NG7 2RD, UK
| | - Nigel P Minton
- BBSRC/EPSRC Synthetic Biology Research Centre, School of Life Sciences, University Park, University of Nottingham, Nottingham NG7 2RD, UK.
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9
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Minton NP, Ehsaan M, Humphreys CM, Little GT, Baker J, Henstra AM, Liew F, Kelly ML, Sheng L, Schwarz K, Zhang Y. A roadmap for gene system development in Clostridium. Anaerobe 2016; 41:104-112. [PMID: 27234263 PMCID: PMC5058259 DOI: 10.1016/j.anaerobe.2016.05.011] [Citation(s) in RCA: 69] [Impact Index Per Article: 8.6] [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: 02/27/2016] [Revised: 05/19/2016] [Accepted: 05/21/2016] [Indexed: 01/18/2023]
Abstract
Clostridium species are both heroes and villains. Some cause serious human and animal diseases, those present in the gut microbiota generally contribute to health and wellbeing, while others represent useful industrial chassis for the production of chemicals and fuels. To understand, counter or exploit, there is a fundamental requirement for effective systems that may be used for directed or random genome modifications. We have formulated a simple roadmap whereby the necessary gene systems maybe developed and deployed. At its heart is the use of ‘pseudo-suicide’ vectors and the creation of a pyrE mutant (a uracil auxotroph), initially aided by ClosTron technology, but ultimately made using a special form of allelic exchange termed ACE (Allele-Coupled Exchange). All mutants, regardless of the mutagen employed, are made in this host. This is because through the use of ACE vectors, mutants can be rapidly complemented concomitant with correction of the pyrE allele and restoration of uracil prototrophy. This avoids the phenotypic effects frequently observed with high copy number plasmids and dispenses with the need to add antibiotic to ensure plasmid retention. Once available, the pyrE host may be used to stably insert all manner of application specific modules. Examples include, a sigma factor to allow deployment of a mariner transposon, hydrolases involved in biomass deconstruction and therapeutic genes in cancer delivery vehicles. To date, provided DNA transfer is obtained, we have not encountered any clostridial species where this technology cannot be applied. These include, Clostridium difficile, Clostridium acetobutylicum, Clostridium beijerinckii, Clostridium botulinum, Clostridium perfringens, Clostridium sporogenes, Clostridium pasteurianum, Clostridium ljungdahlii, Clostridium autoethanogenum and even Geobacillus thermoglucosidasius. A simple roadmap for the development and deployment of gene systems in clostridia. Allelic exchange using pyrE alleles and pseudo-suicide vectors. Knock-out and knock-in using allele-coupled exchange (ACE). Complementation studies through genome insertion. Genome insertion of application specific modules.
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Affiliation(s)
- Nigel P Minton
- Clostridia Research Group, BBSRC/EPSRC Synthetic Biology Research Centre, School of Life Sciences, University of Nottingham, Nottingham, NG7 2RD, UK; Nottingham Digestive Disease Centre, NIHR Biomedical Research Unit, The University of Nottingham, University Park, Nottingham, UK.
| | - Muhammad Ehsaan
- Clostridia Research Group, BBSRC/EPSRC Synthetic Biology Research Centre, School of Life Sciences, University of Nottingham, Nottingham, NG7 2RD, UK
| | - Christopher M Humphreys
- Clostridia Research Group, BBSRC/EPSRC Synthetic Biology Research Centre, School of Life Sciences, University of Nottingham, Nottingham, NG7 2RD, UK
| | - Gareth T Little
- Clostridia Research Group, BBSRC/EPSRC Synthetic Biology Research Centre, School of Life Sciences, University of Nottingham, Nottingham, NG7 2RD, UK
| | - Jonathan Baker
- Clostridia Research Group, BBSRC/EPSRC Synthetic Biology Research Centre, School of Life Sciences, University of Nottingham, Nottingham, NG7 2RD, UK
| | - Anne M Henstra
- Clostridia Research Group, BBSRC/EPSRC Synthetic Biology Research Centre, School of Life Sciences, University of Nottingham, Nottingham, NG7 2RD, UK
| | - Fungmin Liew
- Clostridia Research Group, BBSRC/EPSRC Synthetic Biology Research Centre, School of Life Sciences, University of Nottingham, Nottingham, NG7 2RD, UK
| | - Michelle L Kelly
- Clostridia Research Group, BBSRC/EPSRC Synthetic Biology Research Centre, School of Life Sciences, University of Nottingham, Nottingham, NG7 2RD, UK; Nottingham Digestive Disease Centre, NIHR Biomedical Research Unit, The University of Nottingham, University Park, Nottingham, UK
| | - Lili Sheng
- Clostridia Research Group, BBSRC/EPSRC Synthetic Biology Research Centre, School of Life Sciences, University of Nottingham, Nottingham, NG7 2RD, UK
| | - Katrin Schwarz
- Clostridia Research Group, BBSRC/EPSRC Synthetic Biology Research Centre, School of Life Sciences, University of Nottingham, Nottingham, NG7 2RD, UK
| | - Ying Zhang
- Clostridia Research Group, BBSRC/EPSRC Synthetic Biology Research Centre, School of Life Sciences, University of Nottingham, Nottingham, NG7 2RD, UK
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Humphreys CM, McLean S, Schatschneider S, Millat T, Henstra AM, Annan FJ, Breitkopf R, Pander B, Piatek P, Rowe P, Wichlacz AT, Woods C, Norman R, Blom J, Goesman A, Hodgman C, Barrett D, Thomas NR, Winzer K, Minton NP. Whole genome sequence and manual annotation of Clostridium autoethanogenum, an industrially relevant bacterium. BMC Genomics 2015; 16:1085. [PMID: 26692227 PMCID: PMC4687164 DOI: 10.1186/s12864-015-2287-5] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2015] [Accepted: 12/10/2015] [Indexed: 11/30/2022] Open
Abstract
Background Clostridium autoethanogenum is an acetogenic bacterium capable of producing high value commodity chemicals and biofuels from the C1 gases present in synthesis gas. This common industrial waste gas can act as the sole energy and carbon source for the bacterium that converts the low value gaseous components into cellular building blocks and industrially relevant products via the action of the reductive acetyl-CoA (Wood-Ljungdahl) pathway. Current research efforts are focused on the enhancement and extension of product formation in this organism via synthetic biology approaches. However, crucial to metabolic modelling and directed pathway engineering is a reliable and comprehensively annotated genome sequence. Results We performed next generation sequencing using Illumina MiSeq technology on the DSM10061 strain of Clostridium autoethanogenum and observed 243 single nucleotide discrepancies when compared to the published finished sequence (NCBI: GCA_000484505.1), with 59.1 % present in coding regions. These variations were confirmed by Sanger sequencing and subsequent analysis suggested that the discrepancies were sequencing errors in the published genome not true single nucleotide polymorphisms. This was corroborated by the observation that over 90 % occurred within homopolymer regions of greater than 4 nucleotides in length. It was also observed that many genes containing these sequencing errors were annotated in the published closed genome as encoding proteins containing frameshift mutations (18 instances) or were annotated despite the coding frame containing stop codons, which if genuine, would severely hinder the organism’s ability to survive. Furthermore, we have completed a comprehensive manual curation to reduce errors in the annotation that occur through serial use of automated annotation pipelines in related species. As a result, different functions were assigned to gene products or previous functional annotations rejected because of missing evidence in various occasions. Conclusions We present a revised manually curated full genome sequence for Clostridium autoethanogenum DSM10061, which provides reliable information for genome-scale models that rely heavily on the accuracy of annotation, and represents an important step towards the manipulation and metabolic modelling of this industrially relevant acetogen. Electronic supplementary material The online version of this article (doi:10.1186/s12864-015-2287-5) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Christopher M Humphreys
- BBSRC/EPSRC Synthetic Biology Research Centre, School of Life Sciences, University of Nottingham, Nottingham, NG7 2RD, UK.
| | - Samantha McLean
- BBSRC/EPSRC Synthetic Biology Research Centre, School of Life Sciences, University of Nottingham, Nottingham, NG7 2RD, UK.
| | | | - Thomas Millat
- BBSRC/EPSRC Synthetic Biology Research Centre, School of Life Sciences, University of Nottingham, Nottingham, NG7 2RD, UK.
| | - Anne M Henstra
- BBSRC/EPSRC Synthetic Biology Research Centre, School of Life Sciences, University of Nottingham, Nottingham, NG7 2RD, UK.
| | - Florence J Annan
- BBSRC/EPSRC Synthetic Biology Research Centre, School of Life Sciences, University of Nottingham, Nottingham, NG7 2RD, UK.
| | - Ronja Breitkopf
- BBSRC/EPSRC Synthetic Biology Research Centre, School of Life Sciences, University of Nottingham, Nottingham, NG7 2RD, UK.
| | - Bart Pander
- BBSRC/EPSRC Synthetic Biology Research Centre, School of Life Sciences, University of Nottingham, Nottingham, NG7 2RD, UK.
| | - Pawel Piatek
- BBSRC/EPSRC Synthetic Biology Research Centre, School of Life Sciences, University of Nottingham, Nottingham, NG7 2RD, UK.
| | - Peter Rowe
- BBSRC/EPSRC Synthetic Biology Research Centre, School of Life Sciences, University of Nottingham, Nottingham, NG7 2RD, UK.
| | | | - Craig Woods
- BBSRC/EPSRC Synthetic Biology Research Centre, School of Life Sciences, University of Nottingham, Nottingham, NG7 2RD, UK.
| | - Rupert Norman
- BBSRC/EPSRC Synthetic Biology Research Centre, School of Life Sciences, University of Nottingham, Nottingham, NG7 2RD, UK.
| | - Jochen Blom
- Bioinformatics and Systems Biology, Justus-Liebig-University Giessen, 35392, Giessen, Germany.
| | - Alexander Goesman
- Bioinformatics and Systems Biology, Justus-Liebig-University Giessen, 35392, Giessen, Germany.
| | - Charlie Hodgman
- BBSRC/EPSRC Synthetic Biology Research Centre, School of Life Sciences, University of Nottingham, Nottingham, NG7 2RD, UK.
| | - David Barrett
- School of Pharmacy, University of Nottingham, Nottingham, NG7 2RD, UK.
| | - Neil R Thomas
- School of Chemistry, University of Nottingham, Nottingham, NG7 2RD, UK.
| | - Klaus Winzer
- BBSRC/EPSRC Synthetic Biology Research Centre, School of Life Sciences, University of Nottingham, Nottingham, NG7 2RD, UK.
| | - Nigel P Minton
- BBSRC/EPSRC Synthetic Biology Research Centre, School of Life Sciences, University of Nottingham, Nottingham, NG7 2RD, UK.
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Brookes SJ, D'Antona G, Zagorodnyuk VP, Humphreys CM, Costa M. Propagating contractions of the circular muscle evoked by slow stretch in flat sheets of guinea-pig ileum. Neurogastroenterol Motil 2001; 13:519-31. [PMID: 11903913 DOI: 10.1046/j.1365-2982.2001.00290.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Flat sheet preparations of guinea-pig ileum were stretched circumferentially and the propagation of circular muscle contractions along the preparation was investigated. Slow stretch, at 100 microm s-1, of a 50-mm long flat sheet of intestine, evoked circular muscle contraction orally, which propagated, without decrement, for up to 30 mm. This occurred despite circular muscle shortening being prevented, and in the absence of propulsion of contents. Thus, propagation in this flat sheet preparation could not explained on the basis of neuro-mechanical interactions, as previously proposed. Irrespective of the length of preparations, contraction amplitude decreased significantly in the most aboral 10-15 mm of intestine. This was not due to descending inhibitory pathways, but was associated with interruption of ascending excitatory pathways near the aboral end. Slow waves were not detected in circular muscle cells in any preparation (n=8). Smooth muscle action potentials evoked in circular muscle cells, in the presence of tetrodotoxin (TTX, 0.6 micromol L-1), did not propagate for more than 1 mm in the longitudinal axis. Propagation of circular muscle activity, evoked by slow stretch of flat sheet preparations, reveals the presence of a mechanism other than myogenic spread or the neuro-mechanical interactions previously proposed to account for propagation; the nature of this mechanism remains to be determined.
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Affiliation(s)
- S J Brookes
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, South Australia.
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Abstract
We investigated and quantified the spontaneous patterns of motility in the isolated guinea-pig proximal and distal colon taken from adult animals. During spontaneous emptying, profiles of proximal and distal colon were recorded with a video camera, and image analysis was used to construct spatio-temporal maps of the motions of the intestinal wall. Four patterns of motility were recorded. In the proximal colon there were neurally mediated contractions that propagated in the aboral direction at 4.1 mm s(-1), gently pushing the soft contents aborally; these are likely to represent spontaneous peristaltic behaviour. A second pattern, insensitive to tetrodotoxin (TTX; 0.6 microM), consisted, in both oral and aboral propagation, of shallow contractions of the circular muscle (ripples). These contractions propagated aborally at 2.8 +/- 0.45 mm s(-1) and orally at 2.03 +/- 0.31 mm s(-1) (n=10). Of these TTX-resistant contractions, 22.5% propagated both orally and aborally from a common origin. The orally propagated component of these myogenic contractions is likely to correspond to the antiperistalsis widely described in the proximal colon. In the distal colon, two patterns of motor activity were observed. One, induced by natural or artificial pellets, consisted of peristaltic contractions that pushed the pellets aborally at 0.8 mm s(-1) and expelled a pellet every 108 s. In the interval between pellet propulsion and after the distal colon had emptied all of its pellets a second, nerve-mediated pattern of motor activity, consisting of clusters of annular circular muscle contractions separated by short dilated regions, slowly propagated aborally at 0.3 mm s(-1). Both of these motor patterns were abolished by TTX (0.6 microM). A latex balloon, inserted at the oral end of the empty isolated distal colon and inflated to a size similar to faecal pellets, was propelled at 1.4 mm s(-1). Epoxy resin-covered natural pellets were propelled at a similar speed of 1.6 mm s(-1). Our data revealed that myogenic and neurogenic patterns of propagated contractions in the colon occur in isolated preparations and are involved in emptying the colon.
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Affiliation(s)
- G D'Antona
- Department of Human Physiology and Centre for Neuroscience, The Flinders University of South Australia, Adelaide, Australia
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Abstract
1. Segments of isolated guinea-pig intestine, 12 mm long, were distended slowly by intraluminal fluid infusion or by mechanical stretch as either a tube or flat sheet. In all cases, at a constant threshold length, a sudden, large amplitude contraction of the circular muscle occurred orally, corresponding to the initiation of peristalsis. 2. Circumferential stretch of flat sheet preparations evoked graded contractions of the longitudinal muscle (the 'preparatory phase'), which were maintained during circular muscle contraction. This suggests that the lengthening reported during the emptying phase of peristalsis is due to mechanical interactions. 3. The threshold for peristalsis was lower with more rapid stretches and was also lower in long preparations (25 mm) compared with short preparations (5-10 mm), indicating that ascending excitatory pathways play a significant role in triggering peristalsis. 4. Stretching a preparation beyond the threshold for peristalsis evoked contractions of increasing amplitude; thus peristalsis is graded above its threshold. However, during suprathreshold stretch maintained at a constant length, contractions of the circular muscle quickly declined in amplitude and frequency. 5. Circular muscle cells had a resting membrane potential approximately 6 mV more negative than the threshold for action potentials. During slow circumferential stretch, subthreshold graded excitatory motor input to the circular muscle occurred, prior to the initiation of peristalsis. However, peristalsis was initiated by a discrete large excitatory junction potential (12 +/- 2 mV) which evoked bursts of smooth muscle action potentials and which probably arose from synchronized firing of ascending excitatory neuronal pathways.
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Affiliation(s)
- S J Brookes
- Department of Human Physiology and Centre for Neuroscience, Flinders University, GPO Box 2100, Adelaide, South Australia 5001, Australia.
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Abstract
Localized distension of the intestine evokes an ascending excitatory reflex and a descending inhibitory reflex in the circular muscle layer. The sequential activation of these two reflexes is believed to underlie the motor pattern of peristalsis, which is responsible for the co-ordinated propulsion of intestinal contents. In this study we have shown that the initiation of peristalsis involves mechanisms additional to those mediating the ascending excitatory reflex. A short length of guinea-pig small intestine was mounted in a partitioned organ bath so that the lumen was occluded by the partition, but neuronal continuity was maintained. The anal segment was distended by intraluminal fluid infusion to evoke a peristalsis; in the oral segment, an isotonic transducer was used to record circular muscle contractions due to ascending excitatory reflexes. Stepwise distension of the anal segment with 5 microliters increments at 10 s intervals, or with a large, single-step infusion, elicited both the ascending excitatory reflex and peristalsis, when carried out at 3 min intervals. The threshold volume for the ascending excitatory reflex was smaller than the threshold for peristalsis with either incremental or single-step distensions. The ascending excitatory reflex appeared with a shorter delay than peristalsis. Tetrodotoxin (0.6 microM) or hexamethonium (100 microM) added to the oral compartment abolished the ascending excitatory reflex but not peristalsis. These drugs abolished both the ascending excitatory reflex and peristalsis when added to the anal compartment. When stimuli were delivered at 1 min intervals, peristalsis failed completely after the first trial, but the ascending excitatory reflex persisted, at a slightly reduced amplitude. When the anal segment was distended to just-subthreshold volume, electrical field stimulation (0.25-0.5 ms, 1-5 Hz for 1 s), delivered at 3 min intervals, evoked ascending excitatory responses but not peristalsis. Higher frequency stimulation (10 Hz) consistently evoked both peristalsis and the ascending excitatory responses. When trains of electrical stimulation were repeated at 1 min intervals, peristalsis quickly failed, but the ascending excitatory response persisted, although reduced in amplitude. The initiation of peristalsis can be dissociated from the ascending excitatory reflex by its threshold volume, by the duration of distension or the intensity of electrical stimulation required, and by its susceptibility to fatigue with repeated mechanical or electrical stimuli. This suggests that the ascending excitatory reflex may be part of the mechanism underlying the initiation of peristalsis, but that additional mechanisms must also be involved. Peristalsis should not be regarded as a reflex response but rather as an all-or-nothing motor pattern, triggered by mechanical stimulation, similar to other co-ordinated motor patterns in vertebrates and invertebrates.
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Affiliation(s)
- M Tonini
- Department of Human Physiology, School of Medicine, Flinders University of South Australia, Adelaide, South Australia
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Johnson SM, Costa M, Humphreys CM. Opioid dependence in myenteric neurons innervating the circular muscle of guinea-pig ileum. Naunyn Schmiedebergs Arch Pharmacol 1989; 339:166-72. [PMID: 2725695 DOI: 10.1007/bf00165139] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Guinea-pigs were treated with morphine for 6-8 days by subcutaneous implantation of pellets, each containing a mixture of morphine base (120 mg) and morphine hydrochloride (35 mg). Each guinea-pig received a single pellet. Mechanical activity of the circular muscle was recorded in vitro in preparations comprising the circular muscle and myenteric plexus. Exposure to morphine was maintained by addition of 1 microM morphine to the organ baths. After 90 min, morphine was withdrawn, either by repeatedly washing tissues in morphine-free Krebs' solution, or by addition of naloxone to reduce the occupancy of the opioid receptors by morphine. Withdrawal of morphine resulted in markedly enhanced contractile activity compared with that in circular muscle-myenteric plexus preparations from untreated control guinea-pigs. The withdrawal contractions were abolished by tetrodotoxin (600 nM) and greatly reduced by hyoscine (1 microM), indicating that they resulted from action potential discharge in myenteric neurons that release acetylcholine onto the circular muscle. Activation of the cholinergic excitatory motor neurons was not secondary to synaptic activation by cholinergic interneurons, because hexamethonium (100 microM) did not affect withdrawal contractions. The withdrawal response may therefore arise in the cholinergic excitatory motor neurons themselves, or in neurons that activate them via noncholinergic mechanisms.
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Affiliation(s)
- S M Johnson
- Department of Physiology, Centre for Neuroscience, Flinders University of South Australia, Bedford Park
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Johnson SM, Costa M, Humphreys CM. Opioid mu and kappa receptors on axons of cholinergic excitatory motor neurons supplying the circular muscle of guinea-pig ileum. Naunyn Schmiedebergs Arch Pharmacol 1988; 338:397-400. [PMID: 2854208 DOI: 10.1007/bf00172116] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
In preparations of guinea-pig ileum comprising the circular muscle and the axonal processes of myenteric neurons, electrical stimulation evoked contractions of the circular muscle which were abolished by tetrodotoxin and by hyoscine, indicating that they resulted from action potential-mediated release of acetylcholine. The selective mu opioid agonist, (D-Ala2-N-Me-Phe4-Gly5-ol)-enkephalin (DAGO), and the selective kappa opioid agonist, trans-(+/-)-3,4-dichloro-N-(2-(1-pyrrolidinyl) cyclohexyl) benzeneacetamide, U-50488H, caused concentration-dependent and naloxone-reversible inhibitions of nerve-mediated contractions. The experiments indicate that opioid mu and kappa receptors are present on the axonal processes of cholinergic excitatory motor neurons supplying the circular muscle of the guinea-pig ileum.
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MESH Headings
- 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer
- Animals
- Axons/metabolism
- Carbachol/pharmacology
- Enkephalin, Ala(2)-MePhe(4)-Gly(5)-
- Enkephalins/pharmacology
- Female
- Guinea Pigs
- Ileum/drug effects
- Ileum/metabolism
- In Vitro Techniques
- Male
- Motor Neurons/metabolism
- Muscle, Smooth/drug effects
- Muscle, Smooth/metabolism
- Myenteric Plexus/drug effects
- Myenteric Plexus/metabolism
- Narcotics/pharmacology
- Parasympathetic Nervous System/metabolism
- Pyrrolidines/pharmacology
- Receptors, Opioid/metabolism
- Receptors, Opioid, kappa
- Receptors, Opioid, mu
- Tetrodotoxin/pharmacology
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Affiliation(s)
- S M Johnson
- Department of Physiology, Flinders University of South Australia, Bedford Park
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Johnson SM, Costa M, Humphreys CM, Shearman R. Inhibitory effects of opioids in a circular muscle-myenteric plexus preparation of guinea-pig ileum. Naunyn Schmiedebergs Arch Pharmacol 1987; 336:419-24. [PMID: 2829034 DOI: 10.1007/bf00164876] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The actions of opioids were examined in a strip preparation of the external muscle and myenteric plexus of the guinea-pig ileum cut parallel to the circular muscle. Contractions of the circular muscle induced by electrical stimulation of myenteric neurons were depressed in a concentration-dependent manner by the mu agonists, morphine and DAGO, and by the kappa agonist, U-50,488H. The concentrations of morphine, DAGO and U-50,488H which depressed nerve-mediated contractions by 50% (IC50) were 86 nM, 11 nM and 5.0 nM, respectively. The equilibrium dissociation constants (KD) for naloxone as an antagonist of the inhibitory effects of DAGO and of U-50,488H were 5.6 nM and 29.4 nM, respectively. In contrast to the potent inhibitory effects of mu and kappa agonists, the delta-selective agonist, D-Pen-L-Pen, produced only weak inhibition of nerve-mediated contractions. Even at a concentration of 3 microM, there was less than 50% inhibition, which was not antagonised by the delta receptor antagonist, ICI 174864. The experiments indicate that both mu and kappa opioid receptors are present on the myenteric neurons supplying the circular muscle and that delta receptors are either absent or ineffectively activated.
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Affiliation(s)
- S M Johnson
- Department of Physiology, School of Medicine, Flinders University, Bedford Park, S.A
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Abstract
The effects of morphine withdrawal by washout were examined in ilea from guinea-pigs pretreated by subcutaneous implantation of two pellets, each containing 155 mg morphine. One week later preparations of the longitudinal muscle-myenteric plexus were set up in vitro in a modified Krebs solution containing morphine (1 microM). Within 5-15 min after washing in morphine-free Krebs, the preparations exhibited marked spontaneous contractions which became maximal after 20-60 min. The contractions resulting from morphine washout were greatly reduced by TTX and by hyoscine but not by hexamethonium, suggesting that excitation involved predominantly the cholinergic myenteric motor neurons, and was thus similar to that underlying the contraction induced by naloxone. In contrast to the naloxone-induced contractions, however, those resulting from morphine washout were well sustained during periods of recording up to 5 h. Morphine washout therefore provides conditions suitable for investigating the mechanisms underlying the variety of withdrawal signs observed in the ileum in vitro.
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Affiliation(s)
- S M Johnson
- Department of Physiology, School of Medicine, Flinders University, Bedford Park, South Australia
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Costa M, Furness JB, Humphreys CM. Apamin distinguishes two types of relaxation mediated by enteric nerves in the guinea-pig gastrointestinal tract. Naunyn Schmiedebergs Arch Pharmacol 1986; 332:79-88. [PMID: 3005886 DOI: 10.1007/bf00633202] [Citation(s) in RCA: 128] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Eight smooth muscle preparations from the stomach, small intestine and large intestine of the guinea-pig were used to compare apamin's actions in reducing the effectiveness of transmission from enteric inhibitory nerves and in reducing responses to inhibitory agonists alpha, beta-methylene ATP, VIP and isoprenaline. The effects of apamin on inhibitory reflexes in the ileum and colon were also evaluated. Apamin had little or no effect on responses to VIP and isoprenaline in any region, but consistently and substantially reduced responses to alpha, beta-methylene ATP. Responses to stimulation of enteric inhibitory neurons were substantially reduced by apamin in the antrum circular muscle, ileum longitudinal and circular muscle, taenia coli and distal colon longitudinal muscle, but it was ineffective in the fundus circular muscle, proximal colon longitudinal muscle and distal colon circular muscle. It caused a small reduction of the relaxation of the ileal circular muscle caused reflexly by distension, but did not modify the similar descending inhibitory reflex in the circular muscle of the colon. It is concluded that apamin can be used to distinguish two types of non-noradrenergic transmission from enteric inhibitory nerves to gastrointestinal muscle. Furthermore, neither VIP nor ATP can be the sole transmitter chemical released from enteric inhibitory neurons throughout the gastrointestinal tract.
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Humphreys CM, Kronoveter KJ. Inaccuracies of the sling psychrometer caused by thermal radiation or inadequate wick. Am Ind Hyg Assoc J 1970; 31:609-17. [PMID: 5488307 DOI: 10.1080/0002889708506300] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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Humphreys CM, Dukes-Dobos F. A method of assessing the heat load on workers moving about in a complex thermal environment. Int J Biometeorol 1966; 10:187-196. [PMID: 5978318 DOI: 10.1007/bf01426865] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
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