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Han X, Chang L, Chen H, Zhao J, Tian F, Ross RP, Stanton C, van Sinderen D, Chen W, Yang B. Harnessing the endogenous Type I-C CRISPR-Cas system for genome editing in Bifidobacterium breve. Appl Environ Microbiol 2024; 90:e0207423. [PMID: 38319094 PMCID: PMC10952402 DOI: 10.1128/aem.02074-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2023] [Accepted: 01/14/2024] [Indexed: 02/07/2024] Open
Abstract
Bifidobacterium breve, one of the main bifidobacterial species colonizing the human gastrointestinal tract in early life, has received extensive attention for its purported beneficial effects on human health. However, exploration of the mode of action of such beneficial effects exerted by B. breve is cumbersome due to the lack of effective genetic tools, which limits its synthetic biology application. The widespread presence of CRISPR-Cas systems in the B. breve genome makes endogenous CRISPR-based gene editing toolkits a promising tool. This study revealed that Type I-C CRISPR-Cas systems in B. breve can be divided into two groups based on the amino acid sequences encoded by cas gene clusters. Deletion of the gene coding uracil phosphoribosyl-transferase (upp) was achieved in five B. breve strains from both groups using this system. In addition, translational termination of uracil phosphoribosyl-transferase was successfully achieved in B. breve FJSWX38M7 by single-base substitution of the upp gene and insertion of three stop codons. The gene encoding linoleic acid isomerase (bbi) in B. breve, being a characteristic trait, was deleted after plasmid curing, which rendered it unable to convert linoleic acid into conjugated linoleic acid, demonstrating the feasibility of successive editing. This study expands the toolkit for gene manipulation in B. breve and provides a new approach toward functional genome editing and analysis of B. breve strains.IMPORTANCEThe lack of effective genetic tools for Bifidobacterium breve is an obstacle to studying the molecular mechanisms of its health-promoting effects, hindering the development of next-generation probiotics. Here, we introduce a gene editing method based on the endogenous CRISPR-Cas system, which can achieve gene deletion, single-base substitution, gene insertion, and successive gene editing in B. breve. This study will facilitate discovery of functional genes and elucidation of molecular mechanisms of B. breve pertaining to health-associated benefits.
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Affiliation(s)
- Xiao Han
- State Key Laboratory of Food Science and Resources, Jiangnan University, Wuxi, Jiangsu, China
- School of Food Science and Technology, Jiangnan University, Wuxi, Jiangsu, China
| | - Lulu Chang
- State Key Laboratory of Food Science and Resources, Jiangnan University, Wuxi, Jiangsu, China
- School of Food Science and Technology, Jiangnan University, Wuxi, Jiangsu, China
| | - Haiqin Chen
- State Key Laboratory of Food Science and Resources, Jiangnan University, Wuxi, Jiangsu, China
- School of Food Science and Technology, Jiangnan University, Wuxi, Jiangsu, China
| | - Jianxin Zhao
- State Key Laboratory of Food Science and Resources, Jiangnan University, Wuxi, Jiangsu, China
- School of Food Science and Technology, Jiangnan University, Wuxi, Jiangsu, China
| | - Fengwei Tian
- State Key Laboratory of Food Science and Resources, Jiangnan University, Wuxi, Jiangsu, China
- School of Food Science and Technology, Jiangnan University, Wuxi, Jiangsu, China
- International Joint Research Center for Probiotics & Gut Health, Jiangnan University, Wuxi, Jiangsu, China
| | - R. Paul Ross
- International Joint Research Center for Probiotics & Gut Health, Jiangnan University, Wuxi, Jiangsu, China
- APC Microbiome Ireland, University College Cork, Cork, Ireland
| | - Catherine Stanton
- International Joint Research Center for Probiotics & Gut Health, Jiangnan University, Wuxi, Jiangsu, China
- Teagasc Food Research Centre, Moorepark, Fermoy, Cork, Ireland
| | | | - Wei Chen
- State Key Laboratory of Food Science and Resources, Jiangnan University, Wuxi, Jiangsu, China
- School of Food Science and Technology, Jiangnan University, Wuxi, Jiangsu, China
- National Engineering Research Center for Functional Food, Jiangnan University, Wuxi, Jiangsu, China
| | - Bo Yang
- State Key Laboratory of Food Science and Resources, Jiangnan University, Wuxi, Jiangsu, China
- School of Food Science and Technology, Jiangnan University, Wuxi, Jiangsu, China
- International Joint Research Center for Probiotics & Gut Health, Jiangnan University, Wuxi, Jiangsu, China
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2
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Rimal B, Collins SL, Tanes CE, Rocha ER, Granda MA, Solanki S, Hoque NJ, Gentry EC, Koo I, Reilly ER, Hao F, Paudel D, Singh V, Yan T, Kim MS, Bittinger K, Zackular JP, Krausz KW, Desai D, Amin S, Coleman JP, Shah YM, Bisanz JE, Gonzalez FJ, Vanden Heuvel JP, Wu GD, Zemel BS, Dorrestein PC, Weinert EE, Patterson AD. Bile salt hydrolase catalyses formation of amine-conjugated bile acids. Nature 2024; 626:859-863. [PMID: 38326609 PMCID: PMC10881385 DOI: 10.1038/s41586-023-06990-w] [Citation(s) in RCA: 27] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2022] [Accepted: 12/18/2023] [Indexed: 02/09/2024]
Abstract
Bacteria in the gastrointestinal tract produce amino acid bile acid amidates that can affect host-mediated metabolic processes1-6; however, the bacterial gene(s) responsible for their production remain unknown. Herein, we report that bile salt hydrolase (BSH) possesses dual functions in bile acid metabolism. Specifically, we identified a previously unknown role for BSH as an amine N-acyltransferase that conjugates amines to bile acids, thus forming bacterial bile acid amidates (BBAAs). To characterize this amine N-acyltransferase BSH activity, we used pharmacological inhibition of BSH, heterologous expression of bsh and mutants in Escherichia coli and bsh knockout and complementation in Bacteroides fragilis to demonstrate that BSH generates BBAAs. We further show in a human infant cohort that BBAA production is positively correlated with the colonization of bsh-expressing bacteria. Lastly, we report that in cell culture models, BBAAs activate host ligand-activated transcription factors including the pregnane X receptor and the aryl hydrocarbon receptor. These findings enhance our understanding of how gut bacteria, through the promiscuous actions of BSH, have a significant role in regulating the bile acid metabolic network.
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Affiliation(s)
- Bipin Rimal
- Department of Veterinary and Biomedical Sciences, Pennsylvania State University, University Park, PA, USA
| | - Stephanie L Collins
- Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA, USA
| | - Ceylan E Tanes
- Division of Gastroenterology, Hepatology, and Nutrition, Children's Hospital of Philadelphia, Philadelphia, PA, USA
| | - Edson R Rocha
- Department of Microbiology and Immunology, Brody School of Medicine, East Carolina University, Greenville, NC, USA
| | - Megan A Granda
- Department of Veterinary and Biomedical Sciences, Pennsylvania State University, University Park, PA, USA
| | - Sumeet Solanki
- Department of Molecular & Integrative Physiology and Internal Medicine, Division of Gastroenterology, University of Michigan, Ann Arbor, MI, USA
| | - Nushrat J Hoque
- Department of Chemistry, Pennsylvania State University, University Park, PA, USA
| | - Emily C Gentry
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, San Diego, CA, USA
- Collaborative Mass Spectrometry Innovation Center, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, San Diego, CA, USA
- Department of Chemistry, Virginia Tech, Blacksburg, VA, USA
| | - Imhoi Koo
- Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA, USA
| | - Erin R Reilly
- Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA, USA
| | - Fuhua Hao
- Department of Veterinary and Biomedical Sciences, Pennsylvania State University, University Park, PA, USA
| | - Devendra Paudel
- Department of Nutritional Sciences, Pennsylvania State University, University Park, PA, USA
| | - Vishal Singh
- Department of Nutritional Sciences, Pennsylvania State University, University Park, PA, USA
| | - Tingting Yan
- Laboratory of Metabolism, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - Min Soo Kim
- Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA, USA
| | - Kyle Bittinger
- Division of Gastroenterology, Hepatology, and Nutrition, Children's Hospital of Philadelphia, Philadelphia, PA, USA
| | - Joseph P Zackular
- Division of Protective Immunity, Children's Hospital of Philadelphia, Philadelphia, PA, USA
- Department of Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Kristopher W Krausz
- Laboratory of Metabolism, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - Dhimant Desai
- Department of Pharmacology, Penn State University College of Medicine, Hershey, PA, USA
| | - Shantu Amin
- Department of Pharmacology, Penn State University College of Medicine, Hershey, PA, USA
| | - James P Coleman
- Department of Microbiology and Immunology, Brody School of Medicine, East Carolina University, Greenville, NC, USA
| | - Yatrik M Shah
- Department of Molecular & Integrative Physiology and Internal Medicine, Division of Gastroenterology, University of Michigan, Ann Arbor, MI, USA
| | - Jordan E Bisanz
- Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA, USA
- One Health Microbiome Center, Huck Life Sciences Institute, University Park, PA, USA
| | - Frank J Gonzalez
- Laboratory of Metabolism, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - John P Vanden Heuvel
- Department of Veterinary and Biomedical Sciences, Pennsylvania State University, University Park, PA, USA
- INDIGO Biosciences, Inc., State College, PA, USA
| | - Gary D Wu
- Division of Gastroenterology and Hepatology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Babette S Zemel
- Division of Gastroenterology, Hepatology, and Nutrition, Children's Hospital of Philadelphia, Philadelphia, PA, USA
| | - Pieter C Dorrestein
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, San Diego, CA, USA
- Collaborative Mass Spectrometry Innovation Center, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, San Diego, CA, USA
| | - Emily E Weinert
- Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA, USA
- Department of Chemistry, Pennsylvania State University, University Park, PA, USA
| | - Andrew D Patterson
- Department of Veterinary and Biomedical Sciences, Pennsylvania State University, University Park, PA, USA.
- Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA, USA.
- One Health Microbiome Center, Huck Life Sciences Institute, University Park, PA, USA.
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3
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Hoedt EC, Bottacini F, Cash N, Bongers RS, van Limpt K, Ben Amor K, Knol J, MacSharry J, van Sinderen D. Broad Purpose Vector for Site-Directed Insertional Mutagenesis in Bifidobacterium breve. Front Microbiol 2021; 12:636822. [PMID: 33833740 PMCID: PMC8021953 DOI: 10.3389/fmicb.2021.636822] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2020] [Accepted: 03/02/2021] [Indexed: 11/28/2022] Open
Abstract
Members of the genus Bifidobacterium are notoriously recalcitrant to genetic manipulation due to their extensive and variable repertoire of Restriction-Modification (R-M) systems. Non-replicating plasmids are currently employed to achieve insertional mutagenesis in Bifidobacterium. One of the limitations of using such insertion vectors is the presence within their sequence of various restriction sites, making them sensitive to the activity of endogenous restriction endonucleases encoded by the target strain. For this reason, vectors have been developed with the aim of methylating and protecting the vector using a methylase-positive Escherichia coli strain, in some cases containing a cloned bifidobacterial methylase. Here, we present a mutagenesis approach based on a modified and synthetically produced version of the suicide vector pORI28 (named pFREM28), where all known restriction sites targeted by Bifidobacterium breve R-M systems were removed by base substitution (thus preserving the codon usage). After validating the integrity of the erythromycin marker, the vector was successfully employed to target an α-galactosidase gene responsible for raffinose metabolism, an alcohol dehydrogenase gene responsible for mannitol utilization and a gene encoding a priming glycosyltransferase responsible for exopolysaccharides (EPS) production in B. breve. The advantage of using this modified approach is the reduction of the amount of time, effort and resources required to generate site-directed mutants in B. breve and a similar approach may be employed to target other (bifido)bacterial species.
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Affiliation(s)
- Emily C Hoedt
- APC Microbiome Ireland, University College Cork, Cork, Ireland.,NHMRC Centre of Research Excellence in Digestive Health, School of Medicine and Public Health, The University of Newcastle, Callaghan, NSW, Australia
| | - Francesca Bottacini
- NHMRC Centre of Research Excellence in Digestive Health, School of Medicine and Public Health, The University of Newcastle, Callaghan, NSW, Australia.,Department of Biological Sciences, Munster Technological University, Cork, Ireland
| | - Nora Cash
- NHMRC Centre of Research Excellence in Digestive Health, School of Medicine and Public Health, The University of Newcastle, Callaghan, NSW, Australia
| | | | | | | | - Jan Knol
- Danone Nutricia Research, Utrecht, Netherlands.,Laboratory of Microbiology, Wageningen University, Wageningen, Netherlands
| | - John MacSharry
- NHMRC Centre of Research Excellence in Digestive Health, School of Medicine and Public Health, The University of Newcastle, Callaghan, NSW, Australia.,School of Microbiology, University College Cork, Cork, Ireland.,School of Medicine, University College Cork, Cork, Ireland
| | - Douwe van Sinderen
- NHMRC Centre of Research Excellence in Digestive Health, School of Medicine and Public Health, The University of Newcastle, Callaghan, NSW, Australia.,School of Microbiology, University College Cork, Cork, Ireland
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4
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Bifidobacterium Transformation. Methods Mol Biol 2021. [PMID: 33649944 DOI: 10.1007/978-1-0716-1274-3_2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
The protocol presented in this chapter describes a generic method for electrotransformation of Bifidobacterium spp., outlining a technique that is ideal for conferring selective properties onto strains as well as allowing the user to introduce or knock out/in selected genes for phenotypic characterization purposes. We have generalized on the plasmid chosen for transformation and antibiotic selection marker, but the protocol is versatile in this respect and we are able to achieve transformation efficiencies up to 107 transformants/μg of DNA.
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5
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A Resource for Cloning and Expression Vectors Designed for Bifidobacteria: Overview of Available Tools and Biotechnological Applications. Methods Mol Biol 2021. [PMID: 33649956 DOI: 10.1007/978-1-0716-1274-3_14] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2023]
Abstract
Bifidobacteria represent an important group of (mostly) commensal microorganisms, which have enjoyed increasing scientific and industrial attention due to their purported health-promoting attributes. For the latter reason, several species have been granted "generally recognized as safe" (GRAS) and "qualified presumption of safety" (QPS) status by the Food and Drugs Administration (FDA) and European Food Safety Authority (EFSA) organizations. Increasing scientific evidence supports their potential as oral delivery vectors to produce bioactive and therapeutic molecules at intestinal level. In order to achieve an efficient utilization of bifidobacterial strains as health-promoting (food) ingredients, it is necessary to provide evidence on the molecular mechanisms behind their purported beneficial and probiotic traits, and precise mechanisms of interaction with their human (or other mammalian) host. In this context, developing appropriate molecular tools to generate and investigate recombinant strains is necessary. While bifidobacteria have long remained recalcitrant to genetic manipulation, a wide array of Bifidobacterium-specific replicating vectors and genetic modification procedures have been described in literature. The current chapter intends to provide an updated overview on the vectors used to genetically modify and manipulate bifidobacteria, including their general characteristics, reviewing examples of their use to successfully generate recombinant bifidobacterial strains for specific purposes, and providing a general workflow and cautions to design and conduct heterologous expression in bifidobacteria. Knowledge gaps and fields of research that may help to widen the molecular toolbox to improve the functional and technological potential of bifidobacteria are also discussed.
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6
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Site-Directed Mutagenesis of Bifidobacterium Strains. Methods Mol Biol 2021. [PMID: 33649947 DOI: 10.1007/978-1-0716-1274-3_5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/30/2023]
Abstract
At present, only a limited number of Bifidobacterium species are amenable to genetic manipulation using mutagenesis. This lack of genetic accessibility among the majority of bifidobacterial strains represents a significant roadblock for the study of gene function and expression in these potential probiotics. Genetic tools for generating mutants are difficult to develop for bifidobacteria, as they require workarounds for obstacles such as low transformation efficiencies, and the presence of differing and sometimes multiple restriction modification systems, in different strains. Site-directed mutagenesis is a frequently applied molecular strategy for the generation of targeted mutations, resulting in gene deletion or disruption, or alteration of their expression, thereby revealing information regarding their function. This strategy has been employed as a molecular tool in some Bifidobacterium strains and is typically achieved using a nonreplicating vector, harboring a DNA fragment corresponding to an internal part of the gene to be mutated. This vector is introduced into a bifidobacterial cell of the strain in question by electroporation. Through homologous recombination, this vector is integrated into the genomic DNA of said cell, disrupting the coding region of the targeted gene, thus preventing the expression of a functional protein product. Such mutant versions of Bifidobacterium strains may then be assessed for alterations in their phenotype or gene expression.
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7
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Higgins MA, Ryan KS. Generating a fucose permease deletion mutant in Bifidobacterium longum subspecies infantis ATCC 15697. Anaerobe 2021; 68:102320. [PMID: 33460787 DOI: 10.1016/j.anaerobe.2021.102320] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2020] [Revised: 01/11/2021] [Accepted: 01/12/2021] [Indexed: 12/16/2022]
Abstract
Bifidobacterium longum subsp. infantis ATCC 15697 has emerged as a model for infant gut-associated bifidobacterial strains. Here we present a genetic system for B. longum subsp. infantis ATCC 15697 using its own DNA restriction-modification systems and create a fucose permease deletion mutant lacking the ability to use free fucose as a carbon source.
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Affiliation(s)
- Melanie A Higgins
- Department of Chemistry, The University of British Columbia, Vancouver, British Columbia, V6T 1Z1, Canada
| | - Katherine S Ryan
- Department of Chemistry, The University of British Columbia, Vancouver, British Columbia, V6T 1Z1, Canada.
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8
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Abstract
Random transposon mutagenesis allows for relatively rapid, genome-wide surveys to detect genes involved in functional traits, by performing screens of mutant libraries. This approach has been widely applied to identify genes responsible for activities of interest in multiple eukaryote and prokaryote organisms, although most studies on microorganisms have focused on pathogenic and clinically relevant bacteria. In this chapter we describe the implementation of an in vitro Tn5-based transposome strategy to generate a large collection of random mutants in the gut commensal Bifidobacterium breve UCC2003, and discuss considerations when applying this mutagenesis system to other Bifidobacterium species or strains of interest.
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Affiliation(s)
- Lorena Ruiz
- Department of Microbiology and Biochemistry of Dairy Products, IPLA-CSIC, Villaviciosa, Asturias, Spain
| | - Douwe van Sinderen
- APC Microbiome Ireland, University College Cork, Cork, Ireland.
- School of Microbiology, University College Cork, Cork, Ireland.
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9
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A Transposon Mutagenesis System for Bifidobacterium longum subsp. longum Based on an IS 3 Family Insertion Sequence, IS Blo11. Appl Environ Microbiol 2018; 84:AEM.00824-18. [PMID: 29934330 DOI: 10.1128/aem.00824-18] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2018] [Accepted: 06/16/2018] [Indexed: 12/29/2022] Open
Abstract
Bifidobacteria are a major component of the intestinal microbiota in humans, particularly breast-fed infants. Therefore, elucidation of the mechanisms by which these bacteria colonize the intestine is desired. One approach is transposon mutagenesis, a technique currently attracting much attention because, in combination with next-generation sequencing, it enables exhaustive identification of genes that contribute to microbial fitness. We now describe a transposon mutagenesis system for Bifidobacterium longum subsp. longum 105-A (JCM 31944) based on ISBlo11, a native IS3 family insertion sequence. To build this system, xylose-inducible or constitutive bifidobacterial promoters were tested to drive the expression of full-length or a truncated form at the N terminus of the ISBlo11 transposase. An artificial transposon plasmid, pBFS12, in which ISBlo11 terminal inverted repeats are separated by a 3-bp spacer, was also constructed to mimic the transposition intermediate of IS3 elements. The introduction of this plasmid into a strain expressing transposase resulted in the insertion of the plasmid with an efficiency of >103 CFU/μg DNA. The plasmid targets random 3- to 4-bp sequences, but with a preference for noncoding regions. This mutagenesis system also worked at least in B. longum NCC2705. Characterization of a transposon insertion mutant revealed that a putative α-glucosidase mediates palatinose and trehalose assimilation, demonstrating the suitability of transposon mutagenesis for loss-of-function analysis. We anticipate that this approach will accelerate functional genomic studies of B. longum subsp. longumIMPORTANCE Several hundred species of bacteria colonize the mammalian intestine. However, the genes that enable such bacteria to colonize and thrive in the intestine remain largely unexplored. Transposon mutagenesis, combined with next-generation sequencing, is a promising tool to comprehensively identify these genes but has so far been applied only to a small number of intestinal bacterial species. In this study, a transposon mutagenesis system was established for Bifidobacterium longum subsp. longum, a representative health-promoting Bifidobacterium species. The system enables the identification of genes that promote colonization and survival in the intestine and should help illuminate the physiology of this species.
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10
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Stevens MJ, Venturini A, Lacroix C, Meile L. Enhancing oxidative stress resistance in Bifidobacterium thermophilum using a novel overexpression vector and transformation protocol. Plasmid 2017; 92:43-48. [DOI: 10.1016/j.plasmid.2017.06.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2017] [Revised: 06/09/2017] [Accepted: 06/09/2017] [Indexed: 12/30/2022]
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11
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Tahoun A, Masutani H, El-Sharkawy H, Gillespie T, Honda RP, Kuwata K, Inagaki M, Yabe T, Nomura I, Suzuki T. Capsular polysaccharide inhibits adhesion of Bifidobacterium longum 105-A to enterocyte-like Caco-2 cells and phagocytosis by macrophages. Gut Pathog 2017; 9:27. [PMID: 28469711 PMCID: PMC5412050 DOI: 10.1186/s13099-017-0177-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/12/2017] [Accepted: 04/21/2017] [Indexed: 02/07/2023] Open
Abstract
Background Bifidobacterium longum 105-A produces markedly high amounts of capsular polysaccharides (CPS) and exopolysaccharides (EPS) that should play distinct roles in bacterial–host interactions. To identify the biological function of B. longum 105-A CPS/EPS, we carried out an informatics survey of the genome and identified the EPS-encoding genetic locus of B. longum 105-A that is responsible for the production of CPS/EPS. The role of CPS/EPS in the adaptation to gut tract environment and bacteria-gut cell interactions was investigated using the ΔcpsD mutant. Results A putative B. longum 105-A CPS/EPS gene cluster was shown to consist of 24 putative genes encoding a priming glycosyltransferase (cpsD), 7 glycosyltransferases, 4 CPS/EPS synthesis machinery proteins, and 3 dTDP-L-rhamnose synthesis enzymes. These enzymes should form a complex system that is involved in the biogenesis of CPS and/or EPS. To confirm this, we constructed a knockout mutant (ΔcpsD) by a double cross-over homologous recombination. Compared to wild-type, the ∆cpsD mutant showed a similar growth rate. However, it showed quicker sedimentation and formation of cell clusters in liquid culture. EPS was secreted by the ∆cpsD mutant, but had altered monosaccharide composition and molecular weight. Comparison of the morphology of B. longum 105-A wild-type and ∆cpsD by negative staining in light and electron microscopy revealed that the formation of fimbriae is drastically enhanced in the ∆cpsD mutant while the B. longum 105-A wild-type was coated by a thick capsule. The fimbriae expression in the ∆cpsD was closely associated with the disappearance of the CPS layer. The wild-type showed low pH tolerance, adaptation, and bile salt tolerance, but the ∆cpsD mutant had lost this survivability in gastric and duodenal environments. The ∆cpsD mutant was extensively able to bind to the human colon carcinoma Caco-2 cell line and was phagocytosed by murine macrophage RAW 264.7, whereas the wild-type did not bind to epithelial cells and totally resisted internalization by macrophages. Conclusions Our results suggest that CPS/EPS production and fimbriae formation are negatively correlated and play key roles in the survival, attachment, and colonization of B. longum 105-A in the gut. Electronic supplementary material The online version of this article (doi:10.1186/s13099-017-0177-x) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Amin Tahoun
- Faculty of Applied Biological Sciences, Gifu University, 1-1 Yanagido, Gifu, 501-1193 Japan.,Faculty of Veterinary Medicine, Kafr El-Sheikh University, Kafr El-Sheikh, 33516 Egypt
| | - Hisayoshi Masutani
- Faculty of Applied Biological Sciences, Gifu University, 1-1 Yanagido, Gifu, 501-1193 Japan
| | - Hanem El-Sharkawy
- Faculty of Veterinary Medicine, Kafr El-Sheikh University, Kafr El-Sheikh, 33516 Egypt.,Department of Chemistry and Biomolecular Science, Faculty of Engineering, Gifu University, 1-1 Yanagido, Gifu, 501-1193 Japan
| | - Trudi Gillespie
- CALM_live Imaging Facility, Centre for Inflammation Research, University of Edinburgh, Edinburgh, 47 EH16 4TJ UK
| | - Ryo P Honda
- Department of Molecular Pathobiochemistry, Graduate School of Medicine, Gifu University, 1-1 Yanagido, Gifu, 501-1193 Japan
| | - Kazuo Kuwata
- United Graduate School of Drug Discovery and Medical Information Sciences, Gifu University, 1-1 Yanagido, Gifu, 501-1193 Japan.,Department of Gene and Development, Graduate School of Medicine, Gifu University, 1-1 Yanagido, Gifu, 501-1193 Japan.,Center for Highly Advanced Integration of Nano and Life Sciences, Gifu University (G-CHAIN), Gifu University, 1-1 Yanagido, Gifu, 501-1193 Japan
| | - Mizuho Inagaki
- Faculty of Applied Biological Sciences, Gifu University, 1-1 Yanagido, Gifu, 501-1193 Japan.,United Graduate School of Agricultural Science, Gifu University, 1-1 Yanagido, Gifu, 501-1193 Japan
| | - Tomio Yabe
- Faculty of Applied Biological Sciences, Gifu University, 1-1 Yanagido, Gifu, 501-1193 Japan.,Center for Highly Advanced Integration of Nano and Life Sciences, Gifu University (G-CHAIN), Gifu University, 1-1 Yanagido, Gifu, 501-1193 Japan.,United Graduate School of Agricultural Science, Gifu University, 1-1 Yanagido, Gifu, 501-1193 Japan
| | - Izumi Nomura
- Faculty of Applied Biological Sciences, Gifu University, 1-1 Yanagido, Gifu, 501-1193 Japan
| | - Tohru Suzuki
- Faculty of Applied Biological Sciences, Gifu University, 1-1 Yanagido, Gifu, 501-1193 Japan.,United Graduate School of Agricultural Science, Gifu University, 1-1 Yanagido, Gifu, 501-1193 Japan
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12
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Mechanistic Study of Utilization of Water-Insoluble Saccharomyces cerevisiae Glucans by Bifidobacterium breve Strain JCM1192. Appl Environ Microbiol 2017; 83:AEM.03442-16. [PMID: 28115383 DOI: 10.1128/aem.03442-16] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Accepted: 01/14/2017] [Indexed: 11/20/2022] Open
Abstract
Bifidobacteria exert beneficial effects on hosts and are extensively used as probiotics. However, due to the genetic inaccessibility of these bacteria, little is known about their mechanisms of carbohydrate utilization and regulation. Bifidobacterium breve strain JCM1192 can grow on water-insoluble yeast (Saccharomyces cerevisiae) cell wall glucans (YCWG), which were recently considered as potential prebiotics. According to the results of 1H nuclear magnetic resonance (NMR) spectrometry, the YCWG were composed of highly branched (1→3,1→6)-β-glucans and (1→4,1→6)-α-glucans. Although the YCWG were composed of 78.3% β-glucans and 21.7% α-glucans, only α-glucans were consumed by the B. breve strain. The ABC transporter (malEFG1) and pullulanase (aapA) genes were transcriptionally upregulated in the metabolism of insoluble yeast glucans, suggesting their potential involvement in the process. A nonsense mutation identified in the gene encoding an ABC transporter ATP-binding protein (MalK) led to growth failure of an ethyl methanesulfonate-generated mutant with yeast glucans. Coculture of the wild-type strain and the mutant showed that this protein was responsible for the import of yeast glucans or their breakdown products, rather than the export of α-glucan-catabolizing enzymes. Further characterization of the carbohydrate utilization of the mutant and three of its revertants indicated that this mutation was pleiotropic: the mutant could not grow with maltose, glycogen, dextrin, raffinose, cellobiose, melibiose, or turanose. We propose that insoluble yeast α-glucans are hydrolyzed by extracellular pullulanase into maltose and/or maltooligosaccharides, which are then transported into the cell by the ABC transport system composed of MalEFG1 and MalK. The mechanism elucidated here will facilitate the development of B. breve and water-insoluble yeast glucans as novel synbiotics.IMPORTANCE In general, Bifidobacterium strains are genetically intractable. Coupling classic forward genetics with next-generation sequencing, here we identified an ABC transporter ATP-binding protein (MalK) responsible for the import of insoluble yeast glucan breakdown products by B. breve JCM1192. We demonstrated the pleiotropic effects of the ABC transporter ATP-binding protein in maltose/maltooligosaccharide, raffinose, cellobiose, melibiose, and turanose transport. With the addition of transcriptional analysis, we propose that insoluble yeast glucans are broken down by extracellular pullulanase into maltose and/or maltooligosaccharides, which are then transported into the cell by the ABC transport system composed of MalEFG1 and MalK. The mechanism elucidated here will facilitate the development of B. breve and water-insoluble yeast glucans as novel synbiotics.
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Landete JM, Medina M, Arqués JL. Fluorescent reporter systems for tracking probiotic lactic acid bacteria and bifidobacteria. World J Microbiol Biotechnol 2016; 32:119. [PMID: 27263014 DOI: 10.1007/s11274-016-2077-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2016] [Accepted: 04/27/2016] [Indexed: 12/19/2022]
Abstract
In the last two decades, there has been increasing evidence supporting the role of the intestinal microbiota in health and disease, as well as the use of probiotics to modulate its activity and composition. Probiotic bacteria selected for commercial use in foods, mostly lactic acid bacteria and bifidobacteria, must survive in sufficient numbers during the manufacturing process, storage, and passage through the gastro-intestinal tract. They have several modes of action and it is crucial to unravel the mechanisms underlying their postulated beneficial effects. To track their survival and persistence, and to analyse their interaction with the gastro-intestinal epithelia it is essential to discriminate probiotic strains from endogenous microbiota. Fluorescent reporter proteins are relevant tools that can be exploited as a non-invasive marker system for in vivo real-time imaging in complex ecosystems as well as in vitro fluorescence labelling. Oxygen is required for many of these reporter proteins to fluoresce, which is a major drawback in anoxic environments. However, some new fluorescent proteins are able to overcome the potential problems caused by oxygen limitations. The current available approaches and the benefits/disadvantages of using reporter vectors containing fluorescent proteins for labelling of bacterial probiotic species commonly used in food are addressed.
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Affiliation(s)
- José M Landete
- Dpto. de Tecnología de Alimentos, INIA, Carretera de La Coruña Km 7, 28040, Madrid, Spain
| | - Margarita Medina
- Dpto. de Tecnología de Alimentos, INIA, Carretera de La Coruña Km 7, 28040, Madrid, Spain
| | - Juan L Arqués
- Dpto. de Tecnología de Alimentos, INIA, Carretera de La Coruña Km 7, 28040, Madrid, Spain.
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O'Callaghan A, Bottacini F, O'Connell Motherway M, van Sinderen D. Pangenome analysis of Bifidobacterium longum and site-directed mutagenesis through by-pass of restriction-modification systems. BMC Genomics 2015; 16:832. [PMID: 26489930 PMCID: PMC4618763 DOI: 10.1186/s12864-015-1968-4] [Citation(s) in RCA: 75] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2015] [Accepted: 09/30/2015] [Indexed: 12/16/2022] Open
Abstract
Background Bifidobacterial genome analysis has provided insights as to how these gut commensals adapt to and persist in the human GIT, while also revealing genetic diversity among members of a given bifidobacterial (sub)species. Bifidobacteria are notoriously recalcitrant to genetic modification, which prevents exploration of their genomic functions, including those that convey (human) health benefits. Methods PacBio SMRT sequencing was used to determine the whole genome seqeunces of two B. longum subsp. longum strains. The B. longum pan-genome was computed using PGAP v1.2 and the core B. longum phylogenetic tree was constructed using a maximum-likelihood based approach in PhyML v3.0. M.blmNCII was cloned in E. coli and an internal fragment if arfBarfB was cloned into pORI19 for insertion mutagenesis. Results In this study we present the complete genome sequences of two Bifidobacterium longum subsp. longum strains. Comparative analysis with thirty one publicly available B. longum genomes allowed the definition of the B. longum core and dispensable genomes. This analysis also highlighted differences in particular metabolic abilities between members of the B. longum subspecies infantis, longum and suis. Furthermore, phylogenetic analysis of the B. longum core genome indicated the existence of a novel subspecies. Methylome data, coupled to the analysis of restriction-modification systems, allowed us to substantially increase the genetic accessibility of B. longum subsp. longum NCIMB 8809 to a level that was shown to permit site-directed mutagenesis. Conclusions Comparative genomic analysis of thirty three B. longum representatives revealed a closed pan-genome for this bifidobacterial species. Phylogenetic analysis of the B. longum core genome also provides evidence for a novel fifth B. longum subspecies. Finally, we improved genetic accessibility for the strain B. longum subsp. longum NCIMB 8809, which allowed the generation of a mutant of this strain. Electronic supplementary material The online version of this article (doi:10.1186/s12864-015-1968-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- A O'Callaghan
- APC Microbiome Institute & School of Microbiology, University College Cork, Western Road, Cork, Ireland.
| | - F Bottacini
- APC Microbiome Institute & School of Microbiology, University College Cork, Western Road, Cork, Ireland.
| | - M O'Connell Motherway
- APC Microbiome Institute & School of Microbiology, University College Cork, Western Road, Cork, Ireland.
| | - D van Sinderen
- APC Microbiome Institute & School of Microbiology, University College Cork, Western Road, Cork, Ireland.
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Shkoporov AN, Khokhlova EV, Savochkin KA, Kafarskaia LI, Efimov BA. Production of biologically active scFv and VHH antibody fragments in Bifidobacterium longum. FEMS Microbiol Lett 2015; 362:fnv083. [PMID: 25994292 DOI: 10.1093/femsle/fnv083] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/13/2015] [Indexed: 01/01/2023] Open
Abstract
Bifidobacteria constitute a significant part of healthy intestinal microbiota in adults and infants and present a promising platform for construction of genetically modified probiotic agents for treatment of gastrointestinal disorders. In this study, three strains of Bifidobacterium longum were constructed that express and secrete biologically active single-chain antibodies against human TNF-α and Clostridium difficile exotoxin A. Anti-TNF-α scFv antibody D2E7 was produced at the level of 25 μg L(-1) in broth culture and was mostly retained in the cytoplasm, while VHH-type antibodies A20.1 and A26.8 against C. difficile exotoxin A were produced at the levels of 0.3-1 mg L(-1) and secreted very efficiently. The biological activity of both antibody types was demonstrated in the mammalian cell-based assays. Expression of A20.1 and A26.8 was also observed in vivo after intragastric administration of transformed B. longum strains to (C57/BL6 × DBA/2)F1 mice. The obtained B. longum strains may serve as prototypes for construction of novel probiotic medications against inflammatory bowel disease and C. difficile-associated disease.
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Affiliation(s)
- A N Shkoporov
- Department of Microbiology and Virology, Pirogov Russian National Research Medical University, Ostrovitjanova str. 1, Moscow 117997, Russia Pharmbacter LLC, Skladochnaya ul., 1 - 1, Moscow 127018, Russia
| | - E V Khokhlova
- Department of Microbiology and Virology, Pirogov Russian National Research Medical University, Ostrovitjanova str. 1, Moscow 117997, Russia
| | - K A Savochkin
- Pharmbacter LLC, Skladochnaya ul., 1 - 1, Moscow 127018, Russia
| | - L I Kafarskaia
- Department of Microbiology and Virology, Pirogov Russian National Research Medical University, Ostrovitjanova str. 1, Moscow 117997, Russia
| | - B A Efimov
- Department of Microbiology and Virology, Pirogov Russian National Research Medical University, Ostrovitjanova str. 1, Moscow 117997, Russia
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Complete Genome Sequence of Bifidobacterium longum 105-A, a Strain with High Transformation Efficiency. GENOME ANNOUNCEMENTS 2014; 2:2/6/e01311-14. [PMID: 25523770 PMCID: PMC4271160 DOI: 10.1128/genomea.01311-14] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Bifidobacterium longum 105-A shows high transformation efficiency and allows for the generation of gene knockout mutants through homologous recombination. Here, we report the complete genome sequence of strain 105-A. Genes encoding at least four putative restriction-modification systems were found in this genome, which might contribute to its transformation efficiency.
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Sun Z, Westermann C, Yuan J, Riedel CU. Experimental determination and characterization of the gap promoter of Bifidobacterium bifidum S17. Bioengineered 2014; 5:371-7. [PMID: 25482086 DOI: 10.4161/bioe.34423] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
The DNA sequence upstream of the glyceraldehyde 3-phosphate dehydrogenase gene (gap) of various strains of bifidobacteria is used in a number of vector systems for homologous and heterologous expression in this group of bacteria. To date none of the bifidobacterial gap promoters (Pgap) have been verified experimentally. Here, we probe a range of putative bifidobacterial promoters hypothesized to show high constitutive transcriptional activity using a β-glucuronidase reporter system. In silico analysis revealed a predicted bacterial promoter upstream of the gap gene of Bifidobacterium bifidum S17. The corresponding DNA sequences was cloned into the promoter probe vector pMDY23 and yielded highest reporter activities among the promoter sequences tested confirming previous studies. Using rapid amplification of cDNA ends (5'-RACE), we identified the transcription start site (TSS) of Pgap of B. bifidum S17. The experimentally determined TSS and the associated -10 and -35 regions do not match with the promoter predicted in silico. Moreover, a potential ribosome-binding site (RBS) was identified upstream of the ATG start codon of the gap gene, which is complementary to the 3'-end of the 16S rRNA with only 1 mismatch suggesting efficient initiation of translation. Alignment of the Pgap sequences of a number of representative bifidobacteria showed a high level of conservation and the presence of -35 and -10 regions, which are similar but not identical to the consensus promoter sequences of house-keeping genes of Escherichia coli and Bacillus subtilis. Collectively, these results confirm the suitability of Pgap for high level, constitutive expression in bifidobacteria.
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Affiliation(s)
- Zhongke Sun
- a Institute of Microbiology and Biotechnology ; University of Ulm ; Ulm , Germany
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O′Connell Motherway M, Watson D, Bottacini F, Clark TA, Roberts RJ, Korlach J, Garault P, Chervaux C, van Hylckama Vlieg JET, Smokvina T, van Sinderen D. Identification of restriction-modification systems of Bifidobacterium animalis subsp. lactis CNCM I-2494 by SMRT sequencing and associated methylome analysis. PLoS One 2014; 9:e94875. [PMID: 24743599 PMCID: PMC3990576 DOI: 10.1371/journal.pone.0094875] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2014] [Accepted: 03/20/2014] [Indexed: 01/25/2023] Open
Abstract
Bifidobacterium animalis subsp. lactis CNCM I-2494 is a component of a commercialized fermented dairy product for which beneficial effects on health has been studied by clinical and preclinical trials. To date little is known about the molecular mechanisms that could explain the beneficial effects that bifidobacteria impart to the host. Restriction-modification (R-M) systems have been identified as key obstacles in the genetic accessibility of bifidobacteria, and circumventing these is a prerequisite to attaining a fundamental understanding of bifidobacterial attributes, including the genes that are responsible for health-promoting properties of this clinically and industrially important group of bacteria. The complete genome sequence of B. animalis subsp. lactis CNCM I-2494 is predicted to harbour the genetic determinants for two type II R-M systems, designated BanLI and BanLII. In order to investigate the functionality and specificity of these two putative R-M systems in B. animalis subsp. lactis CNCM I-2494, we employed PacBio SMRT sequencing with associated methylome analysis. In addition, the contribution of the identified R-M systems to the genetic accessibility of this strain was assessed.
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Affiliation(s)
- Mary O′Connell Motherway
- Alimentary Pharmabiotic Centre and School of Microbiology, National University of Ireland, Cork, Ireland
| | - Debbie Watson
- Alimentary Pharmabiotic Centre and School of Microbiology, National University of Ireland, Cork, Ireland
| | - Francesca Bottacini
- Alimentary Pharmabiotic Centre and School of Microbiology, National University of Ireland, Cork, Ireland
| | - Tyson A. Clark
- Pacific Biosciences, Menlo Park, California, United States of America
| | | | - Jonas Korlach
- Pacific Biosciences, Menlo Park, California, United States of America
| | | | | | | | | | - Douwe van Sinderen
- Alimentary Pharmabiotic Centre and School of Microbiology, National University of Ireland, Cork, Ireland
- * E-mail:
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Expression of fluorescent proteins in bifidobacteria for analysis of host-microbe interactions. Appl Environ Microbiol 2014; 80:2842-50. [PMID: 24584243 DOI: 10.1128/aem.04261-13] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Bifidobacteria are an important component of the human gastrointestinal microbiota and are frequently used as probiotics. The genetic inaccessibility and lack of molecular tools commonly used in other bacteria have hampered a detailed analysis of the genetic determinants of bifidobacteria involved in their adaptation to, colonization of, and interaction with the host. In the present study, a range of molecular tools were developed that will allow the closing of some of the gaps in functional analysis of bifidobacteria. A number of promoters were tested for transcriptional activity in Bifidobacterium bifidum S17 using pMDY23, a previously published promoter probe vector. The promoter of the gap gene (Pgap) of B. bifidum S17 yielded the highest promoter activity among the promoters tested. Thus, this promoter and the pMDY23 backbone were used to construct a range of vectors for expression of different fluorescent proteins (FPs). Successful expression of cyan fluorescent protein (CFP), green fluorescent protein (GFP), yellow fluorescent protein (YFP), and mCherry could be shown for three strains representing three different Bifidobacterium spp. The red fluorescent B. bifidum S17/pVG-mCherry was further used to demonstrate application of fluorescent bifidobacteria for adhesion assays and detection in primary human macrophages cultured in vitro. Furthermore, pMGC-mCherry was cloned by combining a chloramphenicol resistance marker and expression of the FP mCherry under the control of Pgap. The chloramphenicol resistance marker of pMGC-mCherry was successfully used to determine gastrointestinal transit time of B. bifidum S17. Moreover, B. bifidum S17/pMGC-mCherry could be detected in fecal samples of mice after oral administration.
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Sun Z, He X, Brancaccio VF, Yuan J, Riedel CU. Bifidobacteria exhibit LuxS-dependent autoinducer 2 activity and biofilm formation. PLoS One 2014; 9:e88260. [PMID: 24505453 PMCID: PMC3914940 DOI: 10.1371/journal.pone.0088260] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2013] [Accepted: 01/08/2014] [Indexed: 12/26/2022] Open
Abstract
Autoinducer-2 (AI-2) molecules are one class of signalling molecules involved in gene regulation dependent on population density in a mechanism commonly referred to as quorum sensing (QS). AI-2 is produced by the methylthioadenosine/S-adenosyl-homocysteine nucleosidase LuxS. In the present study, we characterise the function of bifidobacterial LuxS proteins to address the question whether these economically important bacteria are able to perform QS communication. All publically available genome sequences of bifidobacteria harbour putative luxS genes. The deduced amino acid sequences are well conserved in the genus and show good homology to the LuxS protein of the prototypical AI-2 producer Vibrio harveyi. The luxS genes of three bifidobacterial strains were successfully expressed in AI-2-negative Escherichia coli DH5α. Supernatants of these recombinant E. coli strains contained significant AI-2 activity. In initial experiments, we failed to detect AI-2 activity in supernatants of bifidobacteria grown in MRSc. High concentration of glucose as well as acidic pH had strong inhibitory effects on AI-2 activity. AI-2 activity could be detected when lower volumes of supernatants were used in the assay. Homologous overexpression of luxS in Bifidobacterium longum NCC2705 increased AI-2 levels in the supernatant. Furthermore, over-expression of luxS or supplementation with AI-2-containing supernatants enhanced biofilm formation of B. longum NCC2705. Collectively, these results suggest that bifidobacteria indeed harbour functional luxS genes that are involved in the production of AI-2-like molecules. To the best of our knowledge, this represents the first report on AI-2 activity produced by bifidobacteria. Self-produced AI-2 activity as well as AI-2-like molecules of other bacteria of the intestinal tract may have a regulatory function in biofilm formation and host colonization by bifidobacteria.
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Affiliation(s)
- Zhongke Sun
- Institute of Microbiology and Biotechnology, University of Ulm, Ulm, Germany
| | - Xiang He
- Institute of Disease Control and Prevention, Academy of Military Medical Sciences, Beijing, China
| | | | - Jing Yuan
- Institute of Disease Control and Prevention, Academy of Military Medical Sciences, Beijing, China
- * E-mail: (CUR); (JY)
| | - Christian U. Riedel
- Institute of Microbiology and Biotechnology, University of Ulm, Ulm, Germany
- * E-mail: (CUR); (JY)
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