1
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Petropoulos M, Champeris Tsaniras S, Nikou S, Maxouri S, Dionellis VS, Kalogeropoulou A, Karamichali A, Ioannidis K, Danalatos IR, Obst M, Naumann R, Delinasios GJ, Gorgoulis VG, Roukos V, Anastassiadis K, Halazonetis TD, Bravou V, Lygerou Z, Taraviras S. Cdt1 overexpression drives colorectal carcinogenesis through origin overlicensing and DNA damage. J Pathol 2023; 259:10-20. [PMID: 36210634 DOI: 10.1002/path.6017] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2022] [Revised: 09/20/2022] [Accepted: 10/05/2022] [Indexed: 11/11/2022]
Abstract
Chromatin licensing and DNA replication factor 1 (CDT1), a protein of the pre-replicative complex, is essential for loading the minichromosome maintenance complex (MCM) helicases onto the origins of DNA replication. While several studies have shown that dysregulation of CDT1 expression causes re-replication and DNA damage in cell lines, and CDT1 is highly expressed in several human cancers, whether CDT1 deregulation is sufficient to enhance tumorigenesis in vivo is currently unclear. To delineate its role in vivo, we overexpressed Cdt1 in the mouse colon and induced carcinogenesis using azoxymethane/dextran sodium sulfate (AOM/DSS). Here, we show that mice overexpressing Cdt1 develop a significantly higher number of tumors with increased tumor size, and more severe dysplastic changes (high-grade dysplasia), compared with control mice under the same treatment. These tumors exhibited an increased growth rate, while cells overexpressing Cdt1 loaded greater amounts of Mcm2 onto chromatin, demonstrating origin overlicensing. Adenomas overexpressing Cdt1 showed activation of the DNA damage response (DDR), apoptosis, formation of micronuclei, and chromosome segregation errors, indicating that aberrant expression of Cdt1 results in increased genomic and chromosomal instability in vivo, favoring cancer development. In line with these results, high-level expression of CDT1 in human colorectal cancer tissue specimens and colorectal cancer cell lines correlated significantly with increased origin licensing, activation of the DDR, and microsatellite instability (MSI). © 2022 The Pathological Society of Great Britain and Ireland.
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Affiliation(s)
- Michalis Petropoulos
- Department of Physiology, Medical School, University of Patras, Patras, Greece.,Department of General Biology, Medical School, University of Patras, Patras, Greece
| | | | - Sofia Nikou
- Department of Anatomy-Histology-Embryology, School of Medicine, University of Patras, Patras, Greece
| | - Styliani Maxouri
- Department of General Biology, Medical School, University of Patras, Patras, Greece
| | | | | | | | | | | | - Mandy Obst
- Stem Cell Engineering, Biotechnology Center, Center for Molecular and Cellular Bioengineering, University of Technology Dresden, Dresden, Germany
| | - Ronald Naumann
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
| | | | - Vassilis G Gorgoulis
- Department of Histology and Embryology, School of Medicine, National Kapodistrian University of Athens, Athens, Greece.,Biomedical Research Foundation of the Academy of Athens, Athens, Greece.,Faculty of Biology, Medicine and Health, University of Manchester, Manchester Academic Health Science Centre, Manchester, UK
| | | | - Konstantinos Anastassiadis
- Stem Cell Engineering, Biotechnology Center, Center for Molecular and Cellular Bioengineering, University of Technology Dresden, Dresden, Germany
| | | | - Vasiliki Bravou
- Department of Anatomy-Histology-Embryology, School of Medicine, University of Patras, Patras, Greece
| | - Zoi Lygerou
- Department of General Biology, Medical School, University of Patras, Patras, Greece
| | - Stavros Taraviras
- Department of Physiology, Medical School, University of Patras, Patras, Greece
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2
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Tomaszewski EJ, Olson L, Obst M, Byrne JM, Kappler A, Muehe EM. Complexation by cysteine and iron mineral adsorption limit cadmium mobility during metabolic activity of Geobacter sulfurreducens. Environ Sci Process Impacts 2020; 22:1877-1887. [PMID: 32803208 DOI: 10.1039/d0em00244e] [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: 06/11/2023]
Abstract
Cadmium (Cd) adversely affects human health by entering the food chain via anthropogenic activity. In order to mitigate risk, a better understanding of the biogeochemical mechanisms limiting Cd mobility in the environment is needed. While Cd is not redox-active, Cd speciation varies (i.e., aqueous, complexed, adsorbed), and influences mobility. Here, the cycling of Cd in relation to initial speciation during the growth of Geobacter sulfurreducens was studied. Either fumarate or ferrihydrite (Fh) was provided as an electron acceptor and Cd was present as: (1) an aqueous cation, (2) an aqueous complex with cysteine, which is often present in metal stressed soil environments, or (3) adsorbed to Fh. During microbial Fe(iii) reduction, the removal of Cd was substantial (∼80% removal), despite extensive Fe(ii) production (ratio Fe(ii)total : Fetotal = 0.8). When fumarate was the electron acceptor, there was higher removal from solution when Cd was complexed with cysteine (97-100% removal) compared to aqueous Cd (34-50%) removal. Confocal laser scanning microscopy (CLSM) demonstrated the formation of exopolymeric substances (EPS) in all conditions and that Cd was correlated with EPS in the absence of Fe minerals (r = 0.51-0.56). Most notable is that aqueous Cd was more strongly correlated with Geobacter cells (r = 0.72) compared to Cd-cysteine complexes (r = 0.51). This work demonstrates that Cd interactions with cell surfaces and EPS, and Cd solubility during metabolic activity are dependent upon initial speciation. These processes may be especially important in soil environments where sulfur is limited and Fe and organic carbon are abundant.
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Affiliation(s)
- E J Tomaszewski
- Geomicrobiology Group, Center for Applied Geoscience (ZAG), University of Tübingen, Schnarrenbergstrasse 94-96, Tübingen, D-72076, Germany. and University of Delaware, 221 Academy St, Newark, DE 19716, USA
| | - L Olson
- Geomicrobiology Group, Center for Applied Geoscience (ZAG), University of Tübingen, Schnarrenbergstrasse 94-96, Tübingen, D-72076, Germany.
| | - M Obst
- Experimental Biogeochemistry, BayCEER, University Bayreuth, Dr.-Hans-Frisch-Str. 1-3, Bayreuth, 95448, Germany
| | - J M Byrne
- Geomicrobiology Group, Center for Applied Geoscience (ZAG), University of Tübingen, Schnarrenbergstrasse 94-96, Tübingen, D-72076, Germany. and School of Earth Sciences, University of Bristol, Queens Road, Bristol, BS8 1QU, UK
| | - A Kappler
- Geomicrobiology Group, Center for Applied Geoscience (ZAG), University of Tübingen, Schnarrenbergstrasse 94-96, Tübingen, D-72076, Germany.
| | - E M Muehe
- Geomicrobiology Group, Center for Applied Geoscience (ZAG), University of Tübingen, Schnarrenbergstrasse 94-96, Tübingen, D-72076, Germany. and Plant Biogeochemistry Group, Department Environmental Microbiology, Helmholtz-Centre for Environmental Research, Leipzig, Germany
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3
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Baker O, Tsurkan S, Fu J, Klink B, Rump A, Obst M, Kranz A, Schröck E, Anastassiadis K, Stewart AF. The contribution of homology arms to nuclease-assisted genome engineering. Nucleic Acids Res 2017; 45:8105-8115. [PMID: 28582546 PMCID: PMC5570031 DOI: 10.1093/nar/gkx497] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2017] [Accepted: 05/30/2017] [Indexed: 01/29/2023] Open
Abstract
Designer nucleases like CRISPR/Cas9 enable fluent site-directed damage or small mutations in many genomes. Strategies for their use to achieve more complex tasks like regional exchanges for gene humanization or the establishment of conditional alleles are still emerging. To optimize Cas9-assisted targeting, we measured the relationship between targeting frequency and homology length in targeting constructs using a hypoxanthine-guanine phosphoribosyl-transferase assay in mouse embryonic stem cells. Targeting frequency with supercoiled plasmids improved steeply up to 2 kb total homology and continued to increase with even longer homology arms, thereby implying that Cas9-assisted targeting efficiencies can be improved using homology arms of 1 kb or greater. To humanize the Kmt2d gene, we built a hybrid mouse/human targeting construct in a bacterial artificial chromosome by recombineering. To simplify the possible outcomes, we employed a single Cas9 cleavage strategy and best achieved the intended 42 kb regional exchange with a targeting construct including a very long homology arm to recombine ∼42 kb away from the cleavage site. We recommend the use of long homology arm targeting constructs for accurate and efficient complex genome engineering, particularly when combined with the simplifying advantages of using just one Cas9 cleavage at the genome target site.
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Affiliation(s)
- Oliver Baker
- Stem Cell Engineering, Biotechnology Center, Technische Universität Dresden, BioInnovationsZentrum, Tatzberg 47, Dresden 01307, Germany.,Genomics, Biotechnology Center, Technische Universität Dresden, BioInnovationsZentrum, Tatzberg 47, Dresden 01307, Germany
| | - Sarah Tsurkan
- Genomics, Biotechnology Center, Technische Universität Dresden, BioInnovationsZentrum, Tatzberg 47, Dresden 01307, Germany
| | - Jun Fu
- Genomics, Biotechnology Center, Technische Universität Dresden, BioInnovationsZentrum, Tatzberg 47, Dresden 01307, Germany.,Shandong University-Helmholtz Joint Institute of Biotechnology, State Key Laboratory of Microbial Technology, Shandong University, Shanda Nanlu 27, 250100 Jinan, People's Republic of China
| | - Barbara Klink
- Institute for Clinical Genetics, Faculty of Medicine, Carl Gustav Carus, Technische Universität Dresden, Fetscherstrasse 74, Dresden 01307, Germany
| | - Andreas Rump
- Institute for Clinical Genetics, Faculty of Medicine, Carl Gustav Carus, Technische Universität Dresden, Fetscherstrasse 74, Dresden 01307, Germany
| | - Mandy Obst
- Stem Cell Engineering, Biotechnology Center, Technische Universität Dresden, BioInnovationsZentrum, Tatzberg 47, Dresden 01307, Germany.,Genomics, Biotechnology Center, Technische Universität Dresden, BioInnovationsZentrum, Tatzberg 47, Dresden 01307, Germany
| | - Andrea Kranz
- Genomics, Biotechnology Center, Technische Universität Dresden, BioInnovationsZentrum, Tatzberg 47, Dresden 01307, Germany
| | - Evelin Schröck
- Institute for Clinical Genetics, Faculty of Medicine, Carl Gustav Carus, Technische Universität Dresden, Fetscherstrasse 74, Dresden 01307, Germany
| | - Konstantinos Anastassiadis
- Stem Cell Engineering, Biotechnology Center, Technische Universität Dresden, BioInnovationsZentrum, Tatzberg 47, Dresden 01307, Germany
| | - A Francis Stewart
- Genomics, Biotechnology Center, Technische Universität Dresden, BioInnovationsZentrum, Tatzberg 47, Dresden 01307, Germany
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4
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Swanner ED, Bayer T, Wu W, Hao L, Obst M, Sundman A, Byrne JM, Michel FM, Kleinhanns IC, Kappler A, Schoenberg R. Iron Isotope Fractionation during Fe(II) Oxidation Mediated by the Oxygen-Producing Marine Cyanobacterium Synechococcus PCC 7002. Environ Sci Technol 2017; 51:4897-4906. [PMID: 28402123 PMCID: PMC5415872 DOI: 10.1021/acs.est.6b05833] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/18/2016] [Revised: 04/10/2017] [Accepted: 04/12/2017] [Indexed: 06/07/2023]
Abstract
In this study, we couple iron isotope analysis to microscopic and mineralogical investigation of iron speciation during circumneutral Fe(II) oxidation and Fe(III) precipitation with photosynthetically produced oxygen. In the presence of the cyanobacterium Synechococcus PCC 7002, aqueous Fe(II) (Fe(II)aq) is oxidized and precipitated as amorphous Fe(III) oxyhydroxide minerals (iron precipitates, Feppt), with distinct isotopic fractionation (ε56Fe) values determined from fitting the δ56Fe(II)aq (1.79‰ and 2.15‰) and the δ56Feppt (2.44‰ and 2.98‰) data trends from two replicate experiments. Additional Fe(II) and Fe(III) phases were detected using microscopy and chemical extractions and likely represent Fe(II) and Fe(III) sorbed to minerals and cells. The iron desorbed with sodium acetate (FeNaAc) yielded heavier δ56Fe compositions than Fe(II)aq. Modeling of the fractionation during Fe(III) sorption to cells and Fe(II) sorption to Feppt, combined with equilibration of sorbed iron and with Fe(II)aq using published fractionation factors, is consistent with our resulting δ56FeNaAc. The δ56Feppt data trend is inconsistent with complete equilibrium exchange with Fe(II)aq. Because of this and our detection of microbially excreted organics (e.g., exopolysaccharides) coating Feppt in our microscopic analysis, we suggest that electron and atom exchange is partially suppressed in this system by biologically produced organics. These results indicate that cyanobacteria influence the fate and composition of iron in sunlit environments via their role in Fe(II) oxidation through O2 production, the capacity of their cell surfaces to sorb iron, and the interaction of secreted organics with Fe(III) minerals.
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Affiliation(s)
- E. D. Swanner
- Iowa
State University, Department of Geological
& Atmospheric Sciences, 2237 Osborn Drive, 253 Science I, Ames, Iowa 50011-1027, United States
| | - T. Bayer
- University
of Tuebingen, Department of Geosciences, Tuebingen, Germany
| | - W. Wu
- University
of Tuebingen, Department of Geosciences, Tuebingen, Germany
| | - L. Hao
- University
of Tuebingen, Department of Geosciences, Tuebingen, Germany
| | - M. Obst
- University
of Bayreuth, Bayreuth Center of Ecology
and Environmental Research, Dr-Hans-Frisch-Str. 1-3, 95448 Bayreuth, Germany
| | - A. Sundman
- University
of Tuebingen, Department of Geosciences, Tuebingen, Germany
| | - J. M. Byrne
- University
of Tuebingen, Department of Geosciences, Tuebingen, Germany
| | - F. M. Michel
- Department
of Geosciences, Virginia Tech, Blacksburg, Virginia 24061-0420, United States
| | - I. C. Kleinhanns
- University
of Tuebingen, Department of Geosciences, Tuebingen, Germany
| | - A. Kappler
- University
of Tuebingen, Department of Geosciences, Tuebingen, Germany
| | - R. Schoenberg
- University
of Tuebingen, Department of Geosciences, Tuebingen, Germany
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5
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Abstract
A novel reactor for solvent-free, visible-light-driven photocatalytic transformations was developed.
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Affiliation(s)
- M. Obst
- Institut für Organische Chemie
- Universität Regensburg
- 93040 Regensburg
- Germany
| | - R. S. Shaikh
- Institut für Organische Chemie
- Universität Regensburg
- 93040 Regensburg
- Germany
| | - B. König
- Institut für Organische Chemie
- Universität Regensburg
- 93040 Regensburg
- Germany
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6
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Obst M. Nekrotisierende Fasziitis – Verhindert Vakuumtherapie die Amputation? Zentralbl Chir 2016. [DOI: 10.1055/s-0036-1586300] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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7
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Baker O, Gupta A, Obst M, Zhang Y, Anastassiadis K, Fu J, Stewart AF. RAC-tagging: Recombineering And Cas9-assisted targeting for protein tagging and conditional analyses. Sci Rep 2016; 6:25529. [PMID: 27216209 PMCID: PMC4877586 DOI: 10.1038/srep25529] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2016] [Accepted: 04/13/2016] [Indexed: 11/30/2022] Open
Abstract
A fluent method for gene targeting to establish protein tagged and ligand inducible conditional loss-of-function alleles is described. We couple new recombineering applications for one-step cloning of gRNA oligonucleotides and rapid generation of short-arm (~1 kb) targeting constructs with the power of Cas9-assisted targeting to establish protein tagged alleles in embryonic stem cells at high efficiency. RAC (Recombineering And Cas9)-tagging with Venus, BirM, APEX2 and the auxin degron is facilitated by a recombineering-ready plasmid series that permits the reuse of gene-specific reagents to insert different tags. Here we focus on protein tagging with the auxin degron because it is a ligand-regulated loss-of-function strategy that is rapid and reversible. Furthermore it includes the additional challenge of biallelic targeting. Despite high frequencies of monoallelic RAC-targeting, we found that simultaneous biallelic targeting benefits from long-arm (>4 kb) targeting constructs. Consequently an updated recombineering pipeline for fluent generation of long arm targeting constructs is also presented.
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Affiliation(s)
- Oliver Baker
- Stem Cell Engineering, Biotechnology Center, Technische Universität Dresden, BioInnovationsZentrum, Tatzberg 47, Dresden 01307, Germany
| | - Ashish Gupta
- Genomics, Biotechnology Center, Technische Universität Dresden, BioInnovationsZentrum, Tatzberg 47, Dresden 01307, Germany
| | - Mandy Obst
- Stem Cell Engineering, Biotechnology Center, Technische Universität Dresden, BioInnovationsZentrum, Tatzberg 47, Dresden 01307, Germany
- Genomics, Biotechnology Center, Technische Universität Dresden, BioInnovationsZentrum, Tatzberg 47, Dresden 01307, Germany
| | - Youming Zhang
- Shandong University–Helmholtz Joint Institute of Biotechnology, State Key Laboratory of Microbial Technology, Shandong University, Shanda Nanlu 27, 250100 Jinan, People’s Republic of China
| | - Konstantinos Anastassiadis
- Stem Cell Engineering, Biotechnology Center, Technische Universität Dresden, BioInnovationsZentrum, Tatzberg 47, Dresden 01307, Germany
| | - Jun Fu
- Genomics, Biotechnology Center, Technische Universität Dresden, BioInnovationsZentrum, Tatzberg 47, Dresden 01307, Germany
- Shandong University–Helmholtz Joint Institute of Biotechnology, State Key Laboratory of Microbial Technology, Shandong University, Shanda Nanlu 27, 250100 Jinan, People’s Republic of China
| | - A. Francis Stewart
- Genomics, Biotechnology Center, Technische Universität Dresden, BioInnovationsZentrum, Tatzberg 47, Dresden 01307, Germany
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8
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Picard A, Obst M, Schmid G, Zeitvogel F, Kappler A. Limited influence of Si on the preservation of Fe mineral-encrusted microbial cells during experimental diagenesis. Geobiology 2016; 14:276-292. [PMID: 26695194 DOI: 10.1111/gbi.12171] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2015] [Accepted: 11/10/2015] [Indexed: 06/05/2023]
Abstract
The reconstruction of the history of microbial life since its emergence on early Earth is impaired by the difficulty to prove the biogenicity of putative microfossils in the rock record. While most of the oldest rocks on Earth have been exposed to different grades of diagenetic alterations, little is known about how the remains of micro-organisms evolve when exposed to pressure (P) and temperature (T) conditions typical of diagenesis. Using spectroscopy and microscopy, we compared morphological, mineralogical, and chemical biosignatures exhibited by Fe mineral-encrusted cells of the bacterium Acidovorax sp. BoFeN1 after long-term incubation under ambient conditions and after experimental diagenesis. We also evaluated the effects of Si on the preservation of microbial cells during the whole process. At ambient conditions, Si affected the morphology but not the identity (goethite) of Fe minerals that formed around cells. Fe-encrusted cells were morphologically well preserved after 1 week at 250 °C-140 MPa and after 16 weeks at 170 °C-120 MPa in the presence or in the absence of Si. Some goethite transformed to hematite and magnetite at 250 °C-140 MPa, but in the presence of Si more goethite was preserved. Proteins-the most abundant cellular components-were preserved over several months at ambient conditions but disappeared after incubations at high temperature and pressure conditions, both in the presence and in the absence of Si. Other organic compounds, such as lipids and extracellular polysaccharides seemed well preserved after exposure to diagenetic conditions. This study provides insights about the composition and potential preservation of microfossils that could have formed in Fe- and Si-rich Precambrian oceans.
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Affiliation(s)
- A Picard
- Center for Applied Geoscience, Eberhard Karls University Tübingen, Tübingen, Germany
| | - M Obst
- Center for Applied Geoscience, Eberhard Karls University Tübingen, Tübingen, Germany
| | - G Schmid
- Center for Applied Geoscience, Eberhard Karls University Tübingen, Tübingen, Germany
| | - F Zeitvogel
- Center for Applied Geoscience, Eberhard Karls University Tübingen, Tübingen, Germany
| | - A Kappler
- Center for Applied Geoscience, Eberhard Karls University Tübingen, Tübingen, Germany
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9
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Zeitvogel F, Schmid G, Hao L, Ingino P, Obst M. ScatterJ: An ImageJ plugin for the evaluation of analytical microscopy datasets. J Microsc 2014; 261:148-56. [PMID: 25515182 DOI: 10.1111/jmi.12187] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Accepted: 09/09/2014] [Indexed: 11/29/2022]
Abstract
We present ScatterJ, an ImageJ plugin that allows for extracting qualitative as well as quantitative information from analytical microscopy datasets. A large variety of analytical microscopy methods are used to obtain spatially resolved chemical information. The resulting datasets are often large and complex, and can contain information that is not obvious or directly accessible. ScatterJ extends and complements existing methods to extract information on correlation and colocalization from pairs of species-specific or element-specific maps. We demonstrate the possibilities to extract information using example datasets from biogeochemical studies, although the plugin is not restricted to this type of research. The information that we could extract from our existing data helped to further our understanding of biogeochemical processes such as mineral formation or heavy metal sorption. ScatterJ can be used for a variety of different two-dimensional (2D) and three-dimensional (3D) datasets such as energy-dispersive X-ray spectroscopy maps, 3D confocal laser scanning microscopy maps, and 2D scanning transmission X-ray microscopy maps.
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Affiliation(s)
- F Zeitvogel
- Environmental Analytical Microscopy, Center for Applied Geosciences, University of Tuebingen, Tuebingen, Germany
| | - G Schmid
- Environmental Analytical Microscopy, Center for Applied Geosciences, University of Tuebingen, Tuebingen, Germany
| | - L Hao
- Environmental Analytical Microscopy, Center for Applied Geosciences, University of Tuebingen, Tuebingen, Germany
| | - P Ingino
- Environmental Analytical Microscopy, Center for Applied Geosciences, University of Tuebingen, Tuebingen, Germany
| | - M Obst
- Environmental Analytical Microscopy, Center for Applied Geosciences, University of Tuebingen, Tuebingen, Germany
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10
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Brandt VC, Lynn MT, Obst M, Brass M, Münchau A. Visual feedback of own tics increases tic frequency in patients with Tourette’s syndrome. Cogn Neurosci 2014; 6:1-7. [DOI: 10.1080/17588928.2014.954990] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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11
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Schmid G, Zeitvogel F, Hao L, Ingino P, Floetenmeyer M, Stierhof YD, Schroeppel B, Burkhardt CJ, Kappler A, Obst M. 3-D analysis of bacterial cell-(iron)mineral aggregates formed during Fe(II) oxidation by the nitrate-reducing Acidovorax sp. strain BoFeN1 using complementary microscopy tomography approaches. Geobiology 2014; 12:340-361. [PMID: 24828365 DOI: 10.1111/gbi.12088] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2013] [Accepted: 04/08/2014] [Indexed: 06/03/2023]
Abstract
The formation of cell-(iron)mineral aggregates as a consequence of bacterial iron oxidation is an environmentally widespread process with a number of implications for processes such as sorption and coprecipitation of contaminants and nutrients. Whereas the overall appearance of such aggregates is easily accessible using 2-D microscopy techniques, the 3-D and internal structure remain obscure. In this study, we examined the 3-D structure of cell-(iron)mineral aggregates formed during Fe(II) oxidation by the nitrate-reducing Acidovorax sp. strain BoFeN1 using a combination of advanced 3-D microscopy techniques. We obtained 3-D structural and chemical information on different cellular encrustation patterns at high spatial resolution (4-200 nm, depending on the method): more specifically, (1) cells free of iron minerals, (2) periplasm filled with iron minerals, (3) spike- or platelet-shaped iron mineral structures, (4) bulky structures on the cell surface, (5) extracellular iron mineral shell structures, (6) cells with iron mineral filled cytoplasm, and (7) agglomerations of extracellular globular structures. In addition to structural information, chemical nanotomography suggests a dominant role of extracellular polymeric substances (EPS) in controlling the formation of cell-(iron)mineral aggregates. Furthermore, samples in their hydrated state showed cell-(iron)mineral aggregates in pristine conditions free of preparation (i.e., drying/dehydration) artifacts. All these results were obtained using 3-D microscopy techniques such as focused ion beam (FIB)/scanning electron microscopy (SEM) tomography, transmission electron microscopy (TEM) tomography, scanning transmission (soft) X-ray microscopy (STXM) tomography, and confocal laser scanning microscopy (CLSM). It turned out that, due to the various different contrast mechanisms of the individual approaches, and due to the required sample preparation steps, only the combination of these techniques was able to provide a comprehensive understanding of structure and composition of the various Fe-precipitates and their association with bacterial cells and EPS.
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Affiliation(s)
- G Schmid
- Center for Applied Geoscience, University of Tuebingen, Tuebingen, Germany
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12
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Rostovskaya M, Naumann R, Fu J, Obst M, Mueller D, Stewart AF, Anastassiadis K. Transposon mediated BAC transgenesis via pronuclear injection of mouse zygotes. Genesis 2013; 51:135-41. [PMID: 23225373 DOI: 10.1002/dvg.22362] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2012] [Accepted: 12/05/2012] [Indexed: 11/09/2022]
Abstract
Pronuclear microinjection of bacterial artificial chromosomes (BACs) is the preferred way to generate transgenic mice because the transgene accurately recapitulates expression of the endogenous gene. However, the method is demanding and the integrity and copy number of the BAC transgene is difficult to control. Here, we describe a simpler pronuclear injection method that relies on transposition to introduce full-length BACs into the mouse genome. The bacterial backbone of a hPAX6-GFP reporter BAC was retrofitted with PiggyBac transposon inverted terminal repeats and co-injected with PiggyBac transposase mRNA. Both the frequency of transgenic founders as well as intact, full-length, single copy integrations were increased. Transposition was determined by a rapid PCR screen for a transpositional signature and confirmation by splinkerette sequencing to show that the BACs were integrated as a single copy either in one or two different genomic sites. BAC transposons displayed improved functional accuracy over random integrants as evaluated by expression of the hPAX6-GFP reporter in embryonic neural tube and absence of ectopic expression. This method involves less work to achieve increased frequencies of both transgenesis and single copy, full-length integrations. These advantages are not only relevant to rodents but also for transgenesis in all systems.
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Affiliation(s)
- Maria Rostovskaya
- Stem Cell Engineering, Biotechnology Center, Technische Universitaet Dresden, Dresden, Germany
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Rostovskaya M, Fu J, Obst M, Baer I, Weidlich S, Wang H, Smith AJH, Anastassiadis K, Stewart AF. Transposon-mediated BAC transgenesis in human ES cells. Nucleic Acids Res 2012; 40:e150. [PMID: 22753106 PMCID: PMC3479164 DOI: 10.1093/nar/gks643] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Transgenesis is a cornerstone of molecular biology. The ability to integrate a specifically engineered piece of DNA into the genome of a living system is fundamental to our efforts to understand life and exploit its implications for medicine, nanotechnology and bioprospecting. However, transgenesis has been hampered by position effects and multi-copy integration problems, which are mainly due to the use of small, plasmid-based transgenes. Large transgenes based on native genomic regions cloned into bacterial artificial chromosomes (BACs) circumvent these problems but are prone to fragmentation. Herein, we report that contrary to widely held notions, large BAC-sized constructs do not prohibit transposition. We also report the first reliable method for BAC transgenesis in human embryonic stem cells (hESCs). The PiggyBac or Sleeping Beauty transposon inverted repeats were integrated into BAC vectors by recombineering, followed by co-lipofection with the corresponding transposase in hESCs to generate robust fluorescent protein reporter lines for OCT4, NANOG, GATA4 and PAX6. BAC transposition delivers several advantages, including increased frequencies of single-copy, full-length integration, which will be useful in all transgenic systems but especially in difficult venues like hESCs.
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Affiliation(s)
- Maria Rostovskaya
- Stem Cell Engineering, BioInnovationsZentrum, Technische Universitaet Dresden, Dresden 01307, Germany
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14
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Hitchcock AP, Obst M, Wang J, Lu YS, Tyliszczak T. Advances in the detection of as in environmental samples using low energy X-ray fluorescence in a scanning transmission X-ray microscope: arsenic immobilization by an Fe(II)-oxidizing freshwater bacteria. Environ Sci Technol 2012; 46:2821-2829. [PMID: 22283463 DOI: 10.1021/es202238k] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Speciation and quantitative mapping of elements, organic and inorganic compounds, and mineral phases in environmental samples at high spatial resolution is needed in many areas of geobiochemistry and environmental science. Scanning transmission X-ray microscopes (STXMs) provide a focused beam which can interrogate samples at a fine spatial scale. Quantitative chemical information can be extracted using the transmitted and energy-resolved X-ray fluorescence channels simultaneously. Here we compare the relative merits of transmission and low-energy X-ray fluorescence detection of X-ray absorption for speciation and quantitative analysis of the spatial distribution of arsenic(V) within cell-mineral aggregates formed by Acidovorax sp. strain BoFeN1, an anaerobic nitrate-reducing Fe(II)-oxidizing β-proteobacteria isolated from the sediments of Lake Constance. This species is noted to be highly tolerant to high levels of As(V). Related, As-tolerant Acidovorax-strains have been found in As-contaminated groundwater wells in Bangladesh and Cambodia wherein they might influence the mobility of As by providing sorption sites which might have different properties as compared to chemically formed Fe-minerals. In addition to demonstrating the lower detection limits that are achieved with X-ray fluorescence relative to transmission detection in STXM, this study helps to gain insights into the mechanisms of As immobilization by biogenic Fe-mineral formation and to further the understanding of As-resistance of anaerobic Fe(II)-oxidizing bacteria.
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Affiliation(s)
- A P Hitchcock
- Department of Chemistry and Chemical Biology, McMaster University, Hamilton, ON, Canada L8S 4M1.
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15
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Kerl S, Kayser K, Obst M, Moga S, Juhasz-Böss I, Solomayer EF. Automatisierte Ultraschalluntersuchung in der Mammadiagnostik – Unizentrische Pilotstudie mit 790 Untersuchungen. Geburtshilfe Frauenheilkd 2011. [DOI: 10.1055/s-0031-1286441] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022] Open
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Abstract
Quantitative three-dimensional (3D) chemical mapping using angle-scan spectro-tomography in a scanning transmission (soft) X-ray microscope (STXM) has been used for the first time to characterize the early stages of CaCO(3) biomineral nucleation on the surface of planktonic freshwater cyanobacterial cells of the strain Synechococcus leopoliensis PCC 7942. The apparatus for STXM angle-scan tomography is described. Aspects of sample preparation, sample mounting and data acquisition and quantitative analysis and interpretation are discussed in detail. Angle-scan tomography and chemically selective 3D imaging at multiple photon energies has been combined with a complete 2D spectromicroscopic characterization of the biochemical and mineralogical composition. This has provided detailed insights into the mechanisms of mineral nucleation, leading to development of a detailed model of CaCO(3) nucleation by the cyanobacterial strain S. leopoliensis PCC 7942. It shows that Ca is absorbed by the extracellular polymeric substances (EPS) of the cyanobacteria and that CaCO(3) with aragonite-like short-range order is precipitated rather homogeneously within the EPS. The precipitation of the thermodynamically more stable calcite polymorph then starts at Ca-rich hot spots within the EPS and close to the cyanobacteria.
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Affiliation(s)
- M Obst
- Center for Applied Geoscience, Tuebingen University, Tuebingen, Germany.
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17
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Hitchcock AP, Dynes JJ, Lawrence JR, Obst M, Swerhone GDW, Korber DR, Leppard GG. Soft X-ray spectromicroscopy of nickel sorption in a natural river biofilm. Geobiology 2009; 7:432-453. [PMID: 19656215 DOI: 10.1111/j.1472-4669.2009.00211.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Scanning transmission X-ray microscopy (STXM) at the C 1s, O 1s, Ni 2p, Ca 2p, Mn 2p, Fe 2p, Mg 1s, Al 1s and Si 1s edges was used to study Ni sorption in a complex natural river biofilm. The 10-week grown river biofilm was exposed to 10 mg L(-1) Ni(2+) (as NiCl(2)) for 24 h. The region of the biofilm examined was dominated by filamentous structures, which were interpreted as the discarded sheaths of filamentous bacteria, as well as a sparse distribution of rod-shaped bacteria. The region also contained discrete particles with spectra similar to those of muscovite, SiO(2) and CaCO(3). The Ni(II) ions were selectively adsorbed by the sheaths of the filamentous bacteria. The sheaths were observed to be metal rich with significant amounts of Ca, Fe and Mn, along with the Ni. In addition, the sheaths had a large silicate content but little organic material. The metal content of the rod-shaped bacterial cells was much lower. The Fe on the sheath was mainly in the Fe(III) oxidation state. Mn was found in II, III and IV oxidation states. The Ni was likely sorbed to Mn-Fe minerals on the sheath. These STXM results have probed nano-scale biogeochemistry associated with bacterial species in a complex, natural biofilm community. They have implications for selective Ni contamination of the food chain and for developing bioremediation strategies.
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Affiliation(s)
- A P Hitchcock
- Brockhouse Institute for Materials Research, McMaster University, ON, Canada.
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18
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Abstract
Calcite nucleation on the surface of cyanobacteria of the Synechococcus leopoliensis strain PCC 7942 was investigated to assess the influence of photosynthetic uptake of inorganic carbon and active ion exchange processes across the cell membrane on the nucleation and precipitation mechanisms. We performed long-term precipitation experiments at a constant CO(2) level in ambient air by adding suspensions of previously washed cyanobacteria to solutions of NaHCO(3)/CaCl(2) which were supersaturated with respect to calcite. Induction times between 4 and 110 h were measured over a range of saturation states, Omega, between 8 and 4. The kinetics of CaCO(3) nucleation was compared between experiments: (i) with ongoing photosynthesis, (ii) with cells metabolizing but not undergoing photosynthetic uptake of inorganic carbon and (iii) in darkness without photosynthesis. No significant differences were observed between the three treatments. The results reveal that under low nutrient concentrations and permanent CO(2) supply, photosynthetic uptake of inorganic carbon predominantly uses CO(2) and consequently does not directly influence the nucleation process of CaCO(3) at the surface of S. leopoliensis. Furthermore, ion exchange processes did not affect the kinetics, indicating a passive nucleation process wherein the cell surface or extracellular polymers provided preferential sites for mineral nucleation. The catalyzing effect of the cyanobacteria on calcite nucleation was equivalent to a approximately 18% reduction in the specific interfacial free energy of the calcite nuclei. This result and the ubiquitous abundance of cyanobacteria suggest that this process may have an impact on local and global carbon cycling.
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Affiliation(s)
- M Obst
- Swiss Federal Institute of Aquatic Science and Technology, Kastanienbaum, Switzerland.
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19
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Abstract
Angiotensin II signals via at least two receptors termed AT1 and AT2. The function of the AT1 receptor is well defined, while that of the AT2 receptor is still shrouded in uncertainty. AT2 gene-deficient (-/-) mice have been helpful in unravelling the function of the AT2 receptor. We have studied AT2-/- and AT2+/+ mice with classical physiological techniques developed for the rat. We found that although AT2-/- mice have normal glomerular filtration rate, the pressure-natriuresis relationship in these mice, compared with AT2+/+ mice, is shifted rightward. Moreover, medullary blood flow fails to increase with increased perfusion pressure while the AT1 receptor expression in the kidneys is increased. We used telemetry and found that AT2-/- mice have about 10 mmHg higher blood pressures than AT2+/+ mice and that their circadian rhythm is disturbed. Moreover, their baroreflexes, as measured by spectral analyses, differs from AT2+/+ controls. The cardiac function of AT2-/- mice is remarkably preserved and the differences are subtle. However, if the mice are given l-NAME hypertension, they exhibit an end-systolic pressure-volume relationship that reveals decreased contractility and probable increased vascular stiffness. Furthermore, the hearts of AT2-/- mice hypertrophy more in response to l-NAME than those of AT2+/+ mice and perivascular fibrosis is increased. DOCA-salt treatment also shows a more rightward pressure-natriuresis relationship in AT2-/- compared with AT2+/+ mice. The renal iNOS expression is increased with DOCA-salt treatment. Our findings support the notion that the AT2 receptor signals antiproliferative and antifibrotic effects and that its presence results in lower blood pressures and lesser responses to secondary forms of hypertension. Technical advances that have allowed us to adapt methods for the rat to the much smaller mouse have facilitated our studies.
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Affiliation(s)
- V Gross
- Franz Volhard Clinic HELIOS Klinikum-Berlin and Max Delbrück Center, Medical Faculty of the Charité, Berlin, Germany
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Gross V, Tank J, Obst M, Jordan J, Diedrich A, Plehm R, Luft FC. CLONIDINE IMPROVES BAROREFLEX SENSITIVITY IN MICE THROUGH PARASYMPATHETIC ACTIVATION. J Hypertens 2004. [DOI: 10.1097/00004872-200406002-00075] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Baum H, Obst M, Huber U, Neumeier D. Cardiac troponin T in patients with high creatinine concentration but normal creatine kinase activity in serum. Clin Chem 1996. [DOI: 10.1093/clinchem/42.3.474] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Affiliation(s)
- H Baum
- Inst. für Klin. Chem. und Pathobiochem., Klinikum rechts der Isar, TU München, Germany
| | - M Obst
- Inst. für Klin. Chem. und Pathobiochem., Klinikum rechts der Isar, TU München, Germany
| | - U Huber
- Inst. für Klin. Chem. und Pathobiochem., Klinikum rechts der Isar, TU München, Germany
| | - D Neumeier
- Inst. für Klin. Chem. und Pathobiochem., Klinikum rechts der Isar, TU München, Germany
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Baum H, Obst M, Huber U, Neumeier D. Cardiac troponin T in patients with high creatinine concentration but normal creatine kinase activity in serum. Clin Chem 1996; 42:474-5. [PMID: 8598121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Affiliation(s)
- H Baum
- Inst. für Klin. Chem. und Pathobiochem., Klinikum rechts der Isar, TU München, Germany
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Abstract
The beta-galactosidase of Lactobacillus sake DSM 20017 is encoded by two genes located on its chromosome. These genes designated lacL and lacM were cloned in Escherichia coli NM 554 on an 8.65 kbp HindIII fragment inserted in vector pRB473. Deletion analysis of the originally cloned fragment revealed that both genes are required for the formation of a functional beta-galactosidase. lacL and lacM are transcribed as a single transcript of approximately 2.9 kbp starting 34 bp upstream of the translational start codon. The proteins derived from lacL and lacM share only 18-59% homology with other beta-galactosidases. The genes encoding the beta-galactosidase are scattered with multiple direct and inverted repeats of 9-12 bp. However, comparison with the plasmid-encoded Leuconostoc lactis beta-galactosidase revealed equal distribution of conserved amino acid residues and suggests that the genes have a common origin. Specific deletions or insertions resulting from the presence of the repeats were not observed. The L. sake beta-galactosidase was phenotypically expressed in E. coli NM 554 and Lactobacillus curvatus LTH 1432. Its two genes can be used to replace antibiotic reporter genes to develop food-grade vectors and alpha-complementation systems for self-cloning in meat lactobacilli.
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Affiliation(s)
- M Obst
- Institut für Lebensmitteltechnologie, Stuttgart, Germany
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24
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Obst M, Cornelissen AW. Detection of DNA sequences in Plasmodium berghei by means of in situ hybridization. Histochemistry 1990; 94:101-7. [PMID: 2190950 DOI: 10.1007/bf00266796] [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: 12/30/2022]
Abstract
A non-radioactive in situ hybridization technique, used to map unique DNA sequences to plant chromosomes, has been adapted for the localization of specific DNA sequences in nuclei of Plasmodium berghei. After hybridization using probes labeled with biotin-11-dUTP, the formed DNA/DNA hybrids were detected by fluorescence microscopy using a specific double-layer antibody technique. Besides its high resolution, this procedure is characterized by a high sensitivity, allowing the detection of a unique sequence as small as 2.5 kb.
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Affiliation(s)
- M Obst
- Max-Planck-Institut für Biologie, Molecular Parasitology Unit, Tübingen, Federal Republic of Germany
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