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Ruan S, Bourne CR. Escherichia coli cells evade inducible parE toxin expression by reducing plasmid copy number. Microbiol Spectr 2024; 12:e0397323. [PMID: 38700352 PMCID: PMC11237751 DOI: 10.1128/spectrum.03973-23] [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: 11/17/2023] [Accepted: 04/15/2024] [Indexed: 05/05/2024] Open
Abstract
Plasmids play important roles in microbial ecosystems, serving as carriers of antibiotic resistance and virulence. In the laboratory, they are essential tools for genetic manipulation and recombinant protein expression. We uncovered an intriguing survival phenotype in a fraction of the bacterial population while using plasmid-mediated arabinose-inducible gene expression to monitor the production of toxic ParE proteins. This phenotype was not correlated with changes to the plasmid sequence and could not be rescued by increasing arabinose uptake. Instead, survival correlates with a marked reduction in plasmid copy number (PCN). Reduced PCN is reproducible, not a function of the pre-existing population, and can be sequentially enriched by continual passage with induction. The reduction in PCN appears to allow mitigation of toxicity from the expression of ParE proteins while balancing the need to maintain a threshold PCN to withstand selection conditions. This indicates an adaptive cellular response to stressful conditions, likely by altering the regulation of plasmid replication. Furthermore, this survival mechanism appears to not be limited to a specific bacterial strain of Escherichia coli or ParE toxin family member, suggesting a generalized response. Finally, bacterial whole genome sequencing indicated an N845S residue substitution in DNA polymerase I, which correlates with the observed reduction in PCN and has been previously reported to impact plasmid replication. Further understanding this molecular mechanism has broader implications for this adaptive response of the dynamics of plasmid-mediated gene expression, microbial adaptation, and genetic engineering methodologies. IMPORTANCE This research has increased our understanding of how bacteria respond to the pressure from plasmid-borne toxic genes, such as those found in toxin-antitoxin systems. Surprisingly, we found that bacteria survived toxic ParE protein expression by reducing the number of these plasmids in the cells. This discovery reveals another way in which bacteria can balance toxin expression with antibiotic selection to attenuate the effects of deleterious genes. This insight is not only valuable for understanding bacterial survival strategies but may also influence the development of better tools in biotechnology, where plasmids are often used to study the functional roles of genes.
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Affiliation(s)
- Shengfeng Ruan
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma, USA
| | - Christina R. Bourne
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma, USA
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Hypersaline Lake Urmia: a potential hotspot for microbial genomic variation. Sci Rep 2023; 13:374. [PMID: 36611086 PMCID: PMC9825399 DOI: 10.1038/s41598-023-27429-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2022] [Accepted: 01/02/2023] [Indexed: 01/09/2023] Open
Abstract
Lake Urmia located in Iran is a hypersaline environment with a salinity of about 27% (w/v). Metagenomic analyses of water samples collected from six locations in the lake exhibited a microbial community dominated by representatives of the family Haloferacaceae (69.8%), mainly those affiliated to only two genera, Haloquadratum (59.3%) and Halonotius (9.1%). Similar to other hypersaline lakes, the bacterial community was dominated by Salinibacter ruber (23.3%). Genomic variation analysis by inspecting single nucleotide variations (SNVs) and insertions/deletions (INDELs) exhibited a high level of SNVs and insertions, most likely through transformation for abundant taxa in the Lake Urmia community. We suggest that the extreme conditions of Lake Urmia and specifically its high ionic concentrations could potentially increase the SNVs and insertions, which can consequently hamper the assembly and genome reconstruction from metagenomic reads of Lake Urmia.
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Schiffer CJ, Grätz C, Pfaffl MW, Vogel RF, Ehrmann MA. Characterization of the Staphylococcus xylosus methylome reveals a new variant of type I restriction modification system in staphylococci. Front Microbiol 2023; 14:946189. [PMID: 36970683 PMCID: PMC10030836 DOI: 10.3389/fmicb.2023.946189] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Accepted: 02/13/2023] [Indexed: 03/29/2023] Open
Abstract
Restriction modification (RM) systems are known to provide a strong barrier to the exchange of DNA between and within bacterial species. Likewise, DNA methylation is known to have an important function in bacterial epigenetics regulating essential pathways such as DNA replication and the phase variable expression of prokaryotic phenotypes. To date, research on staphylococcal DNA methylation focused mainly on the two species Staphylococcus aureus and S. epidermidis. Less is known about other members of the genus such as S. xylosus, a coagulase-negative commensal of mammalian skin. The species is commonly used as starter organism in food fermentations but is also increasingly considered to have an as yet elusive function in bovine mastitis infections. We analyzed the methylomes of 14 S. xylosus strains using single-molecular, real-time (SMRT) sequencing. Subsequent in silico sequence analysis allowed identification of the RM systems and assignment of the respective enzymes to the discovered modification patterns. Hereby the presence of type I, II, III and IV RM systems in varying numbers and combinations among the different strains was revealed, clearly distinguishing the species from what is known for other members of the genus so far. In addition, the study characterizes a newly discovered type I RM system, encoded by S. xylosus but also by a variety of other staphylococcal species, with a hitherto unknown gene arrangement that involves two specificity units instead of one (hsdRSMS). Expression of different versions of the operon in E. coli showed proper base modification only when genes encoding both hsdS subunits were present. This study provides new insights into the general understanding of the versatility and function of RM systems as well as the distribution and variations in the genus Staphylococcus.
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Affiliation(s)
- Carolin J. Schiffer
- Chair of Technical Microbiology, TUM School of Life Sciences, Technical University of Munich, Freising, Germany
- *Correspondence: Carolin J. Schiffer,
| | - Christian Grätz
- Chair of Animal Physiology and Immunology, TUM School of Life Sciences, Technical University of Munich, Freising, Germany
| | - Michael W. Pfaffl
- Chair of Animal Physiology and Immunology, TUM School of Life Sciences, Technical University of Munich, Freising, Germany
| | - Rudi F. Vogel
- Chair of Technical Microbiology, TUM School of Life Sciences, Technical University of Munich, Freising, Germany
| | - Matthias A. Ehrmann
- Chair of Technical Microbiology, TUM School of Life Sciences, Technical University of Munich, Freising, Germany
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Jiang W, Gao H, Sun J, Yang X, Jiang Y, Zhang W, Jiang M, Xin F. Current status, challenges and prospects for lignin valorization by using Rhodococcus sp. Biotechnol Adv 2022; 60:108004. [PMID: 35690272 DOI: 10.1016/j.biotechadv.2022.108004] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Revised: 05/30/2022] [Accepted: 06/03/2022] [Indexed: 11/18/2022]
Abstract
Lignin represents the most abundant renewable aromatics in nature, which has complicated and heterogeneous structure. The rapid development of biotransformation technology has brought new opportunities to achieve the complete lignin valorization. Especially, Rhodococcus sp. possesses excellent capabilities to metabolize aromatic hydrocarbons degraded from lignin. Furthermore, it can convert these toxic compounds into high value added bioproducts, such as microbial lipids, polyhydroxyalkanoate and carotenoid et al. Accordingly, this review will discuss the potentials of Rhodococcus sp. as a cell factory for lignin biotransformation, including phenol tolerance, lignin depolymerization and lignin-derived aromatic hydrocarbon metabolism. The detailed metabolic mechanism for lignin biotransformation and bioproducts spectrum of Rhodococcus sp. will be comprehensively discussed. The available molecular tools for the conversion of lignin by Rhodococcus sp. will be reviewed, and the possible direction for lignin biotransformation in the future will also be proposed.
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Affiliation(s)
- Wankui Jiang
- State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing 211816, PR China
| | - Haiyan Gao
- State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing 211816, PR China
| | - Jingxiang Sun
- State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing 211816, PR China
| | - Xinyi Yang
- State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing 211816, PR China
| | - Yujia Jiang
- State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing 211816, PR China
| | - Wenming Zhang
- State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing 211816, PR China; Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University, Nanjing 211816, PR China.
| | - Min Jiang
- State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing 211816, PR China; Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University, Nanjing 211816, PR China.
| | - Fengxue Xin
- State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing 211816, PR China; Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University, Nanjing 211816, PR China.
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Cell factory for γ-aminobutyric acid (GABA) production using Bifidobacterium adolescentis. Microb Cell Fact 2022; 21:33. [PMID: 35255900 PMCID: PMC8903651 DOI: 10.1186/s12934-021-01729-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Accepted: 12/20/2021] [Indexed: 11/10/2022] Open
Abstract
Abstract
Background
Bifidobacteria are gram-positive, probiotic, and generally regarded as safe bacteria. Techniques such as transformation, gene knockout, and heterologous gene expression have been established for Bifidobacterium, indicating that this bacterium can be used as a cell factory platform. However, there are limited previous reports in this field, likely because of factors such as the highly anaerobic nature of this bacterium. Bifidobacterium adolescentis is among the most oxygen-sensitive Bifidobacterium species. It shows strain-specific gamma-aminobutyric acid (GABA) production. GABA is a potent bioactive compound with numerous physiological and psychological functions. In this study, we investigated whether B. adolesentis could be used for mass production of GABA.
Results
The B. adolescentis 4–2 strain isolated from a healthy adult human produced approximately 14 mM GABA. It carried gadB and gadC, which encode glutamate decarboxylase and glutamate GABA antiporter, respectively. We constructed pKKT427::Pori-gadBC and pKKT427::Pgap-gadBC plasmids carrying gadBC driven by the original gadB (ori) and gap promoters, respectively. Recombinants of Bifidobacterium were then constructed. Two recombinants with high production abilities, monitored by two different promoters, were investigated. GABA production was improved by adjusting the fermentation parameters, including the substrate concentration, initial culture pH, and co-factor supplementation, using response surface methodology. The optimum initial cultivation pH varied when the promoter region was changed. The ori promoter was induced under acidic conditions (pH 5.2:4.4), whereas the constitutive gap promoter showed enhanced GABA production at pH 6.0. Fed-batch fermentation was used to validate the optimum fermentation parameters, in which approximately 415 mM GABA was produced. The conversion ratio of glutamate to GABA was 92–100%.
Conclusion
We report high GABA production in recombinant B. adolescentis. This study provides a foundation for using Bifidobacterium as a cell factory platform for industrial production of GABA.
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Liang Y, Yu H. Genetic toolkits for engineering Rhodococcus species with versatile applications. Biotechnol Adv 2021; 49:107748. [PMID: 33823269 DOI: 10.1016/j.biotechadv.2021.107748] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2021] [Revised: 03/31/2021] [Accepted: 03/31/2021] [Indexed: 02/09/2023]
Abstract
Rhodococcus spp. are a group of non-model gram-positive bacteria with diverse catabolic activities and strong adaptive capabilities, which enable their wide application in whole-cell biocatalysis, environmental bioremediation, and lignocellulosic biomass conversion. Compared with model microorganisms, the engineering of Rhodococcus is challenging because of the lack of universal molecular tools, high genome GC content (61% ~ 71%), and low transformation and recombination efficiencies. Nevertheless, because of the high interest in Rhodococcus species for bioproduction, various genetic elements and engineering tools have been recently developed for Rhodococcus spp., including R. opacus, R. jostii, R. ruber, and R. erythropolis, leading to the expansion of the genetic toolkits for Rhodococcus engineering. In this article, we provide a comprehensive review of the important developed genetic elements for Rhodococcus, including shuttle vectors, promoters, antibiotic markers, ribosome binding sites, and reporter genes. In addition, we also summarize gene transfer techniques and strategies to improve transformation efficiency, as well as random and precise genome editing tools available for Rhodococcus, including transposition, homologous recombination, recombineering, and CRISPR/Cas9. We conclude by discussing future trends in Rhodococcus engineering. We expect that more synthetic and systems biology tools (such as multiplex genome editing, dynamic regulation, and genome-scale metabolic models) will be adapted and optimized for Rhodococcus.
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Affiliation(s)
- Youxiang Liang
- Department of Chemical Engineering, Tsinghua University, Beijing 100084, China; Key Laboratory of Industrial Biocatalysis (Tsinghua University), the Ministry of Education, Beijing 100084, China
| | - Huimin Yu
- Department of Chemical Engineering, Tsinghua University, Beijing 100084, China; Key Laboratory of Industrial Biocatalysis (Tsinghua University), the Ministry of Education, Beijing 100084, China; Center for Synthetic and Systems Biology, Tsinghua University, Beijing 100084, China.
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Liang Y, Jiao S, Wang M, Yu H, Shen Z. A CRISPR/Cas9-based genome editing system for Rhodococcus ruber TH. Metab Eng 2020; 57:13-22. [DOI: 10.1016/j.ymben.2019.10.003] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2019] [Revised: 10/10/2019] [Accepted: 10/10/2019] [Indexed: 02/03/2023]
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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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Affiliation(s)
- Benjamin M. Woolston
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139; , ,
| | - Steven Edgar
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139; , ,
| | - Gregory Stephanopoulos
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139; , ,
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Sakaguchi K, Funaoka N, Tani S, Hobo A, Mitsunaga T, Kano Y, Suzuki T. The pyrE Gene as a Bidirectional Selection Marker in Bifidobacterium Longum 105-A. BIOSCIENCE OF MICROBIOTA FOOD AND HEALTH 2013; 32:59-68. [PMID: 24936363 PMCID: PMC4034322 DOI: 10.12938/bmfh.32.59] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/10/2012] [Accepted: 01/12/2013] [Indexed: 11/30/2022]
Abstract
We constructed a deletion mutant of the pyrE gene in
Bifidobacterium longum 105-A. A pyrE knockout cassette
was cloned into pKKT427, a Bifidobacterium-Escherichia
coli shuttle vector, and then introduced into B. longum 105-A
by electroporation. The transformants were propagated and spread onto MRS plates
containing 5-fluoroorotic acid (5-FOA) and uracil. 5-FOA-resistant mutants were obtained
at a frequency of 4.7 × 10−5 integrations per cell. To perform
pyrE gene complementation, the pyrE gene was amplified
by PCR and used to construct a complementation plasmid
(pKKT427-pyrE+). B. longum 105-A
∆pyrE harboring this plasmid could not grow on MRS plates containing
5-FOA, uracil and spectinomycin. We also developed a chemically defined medium
(bifidobacterial minimal medium; BMM) containing inorganic salts, glucose, vitamins,
isoleucine and tyrosine for positive selection of pyrE transformants.
B. longum 105-A ∆pyrE could not grow on BMM agar, but
the same strain harboring pKKT427-pyrE+ could. Thus,
pyrE can be used as a counterselection marker in
B. longum 105-A and potentially other Bifidobacterium
species as well. We demonstrated the effectiveness of this system by constructing a
knockout mutant of the xynF gene in B. longum 105-A by
using the pyrE gene as a counterselection marker. This
pyrE-based selection system will contribute to genetic studies of
bifidobacteria.
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Affiliation(s)
- Kouta Sakaguchi
- The United Graduate School of Agricultural Science, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan
| | - Nobutaka Funaoka
- Faculty of Applied Biological Sciences, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan
| | - Saori Tani
- Faculty of Applied Biological Sciences, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan
| | - Aya Hobo
- Faculty of Applied Biological Sciences, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan
| | - Tohru Mitsunaga
- Faculty of Applied Biological Sciences, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan
| | - Yasunobu Kano
- Department of Molecular Genetics, Kyoto Pharmaceutical University, 1 Shichono-cho, Misasagi, Yamashina-ku, Kyoto 607-8412, Japan
| | - Tohru Suzuki
- The United Graduate School of Agricultural Science, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan
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A targeted gene knockout method using a newly constructed temperature-sensitive plasmid mediated homologous recombination in Bifidobacterium longum. Appl Microbiol Biotechnol 2012; 95:499-509. [PMID: 22639142 DOI: 10.1007/s00253-012-4090-4] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2012] [Revised: 04/03/2012] [Accepted: 04/07/2012] [Indexed: 10/28/2022]
Abstract
Bifidobacteria are the main component of the human microflora. We constructed a temperature-sensitive (Ts) plasmid by random mutagenesis of the Bifidobacterium-Escherichia coli shuttle vector pKKT427 using error-prone PCR. Mutant plasmids were introduced into Bifidobacterium longum 105-A and, after screening approximately 3,000 colonies, candidate clones that grew at 30 °C but not at 42 °C were selected. According to DNA sequence analysis of the Ts plasmid, five silent and one missense mutations were found in the repB region. The site-directed mutagenesis showed only the missense mutation to be relevant to the Ts phenotype. We designated this plasmid pKO403. The Ts phenotype was also observed in B. longum NCC2705 and Bifidobacterium adolescentis ATCC15703. Single-crossover homologous-recombination experiments were carried out to determine the relationship between the length of homologous sequences encoded on the plasmid and recombination frequency: fragments greater than 1 kb gave an efficiency of more than 10(3) integrations per cell. We performed gene knockout experiments using this Ts plasmid. We obtained gene knockout mutants of the pyrE region of B. longum 105-A, and determined that double-crossover homologous recombination occurred at an efficiency of 1.8 %. This knockout method also worked for the BL0033 gene in B. longum NCC2705.
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Monk IR, Foster TJ. Genetic manipulation of Staphylococci-breaking through the barrier. Front Cell Infect Microbiol 2012; 2:49. [PMID: 22919640 PMCID: PMC3417578 DOI: 10.3389/fcimb.2012.00049] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2012] [Accepted: 03/20/2012] [Indexed: 12/29/2022] Open
Abstract
Most strains of Staphylococcus aureus and Staphylococcus epidermidis possess a strong restriction barrier that hinders exchange of DNA. Recently, major advances have been made in identifying and characterizing the restriction-modification (RM) systems involved. In particular a novel type IV restriction enzyme that recognizes cytosine methylated DNA has been shown to be the major barrier to transfer of plasmid DNA from Escherichia coli into S. aureus and S. epidermidis. While the conserved type I RM system provides a further barrier. Here we review the recent advances in understanding of restriction systems in staphylococci and highlight how this has been exploited to improve our ability to manipulate genetically previously untransformable strains.
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Affiliation(s)
- Ian R Monk
- Department of Microbiology, Moyne Institute of Preventive Medicine, School of Genetics and Microbiology, Trinity College Dublin Dublin, Ireland.
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