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Hjort, Karin
Publications (5 of 5) Show all publications
Hjort, K., Presti, I., Elväng, A., Marinelli, F. & Sjöling, S. (2014). Bacterial chitinase with phytopathogen control capacity from suppressive soil revealed by functional metagenomics. Applied Microbiology and Biotechnology, 98(6), 2819-2828
Open this publication in new window or tab >>Bacterial chitinase with phytopathogen control capacity from suppressive soil revealed by functional metagenomics
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2014 (English)In: Applied Microbiology and Biotechnology, ISSN 0175-7598, E-ISSN 1432-0614, Vol. 98, no 6, p. 2819-2828Article in journal (Refereed) Published
Abstract [en]

Plant disease caused by fungal pathogens results in vast crop damage globally. Microbial communities of soil that is suppressive to fungal crop disease provide a source for the identification of novel enzymes functioning as bioshields against plant pathogens. In this study, we targeted chitin-degrading enzymes of the uncultured bacterial community through a functional metagenomics approach, using a fosmid library of a suppressive soil metagenome. We identified a novel bacterial chitinase, Chi18H8, with antifungal activity against several important crop pathogens. Sequence analyses show that the chi18H8 gene encodes a 425-amino acid protein of 46 kDa with an N-terminal signal peptide, a catalytic domain with the conserved active site F175DGIDIDWE183, and a chitinase insertion domain. Chi18H8 was expressed (pGEX-6P-3 vector) in Escherichia coli and purified. Enzyme characterization shows that Chi18H8 has a prevalent chitobiosidase activity with a maximum activity at 35 °C at pH lower than 6, suggesting a role as exochitinase on native chitin. To our knowledge, Chi18H8 is the first chitinase isolated from a metagenome library obtained in pure form and which has the potential to be used as a candidate agent for controlling fungal crop diseases. Furthermore, Chi18H8 may also answer to the demand for novel chitin-degrading enzymes for a broad range of other industrial processes and medical purposes.

Keywords
metagenomic library, chitinase, terminal restriction fragment length polymorphism (T-RFLP), Streptomycetes, suppressive soil
National Category
Microbiology Environmental Sciences
Research subject
Baltic and East European studies; Environmental Studies
Identifiers
urn:nbn:se:sh:diva-20023 (URN)10.1007/s00253-013-5287-x (DOI)000332108100041 ()24121932 (PubMedID)2-s2.0-84905997072 (Scopus ID)47/42/2011 (Local ID)47/42/2011 (Archive number)47/42/2011 (OAI)
Projects
Metaexplore - metagenomics for bioexploration
Funder
EU, FP7, Seventh Framework Programme, KBBE-222625The Foundation for Baltic and East European Studies
Note

Electronic supplementary material

Available from: 2013-10-24 Created: 2013-10-24 Last updated: 2019-03-04Bibliographically approved
Granhall, U., Welsh, A., Throbäck, I. N., Hjort, K., Hansson, M. & Hallin, S. (2010). Bacterial community diversity in paper mills processing recycled paper. Journal of Industrial Microbiology & Biotechnology, 37(10), 1061-1069
Open this publication in new window or tab >>Bacterial community diversity in paper mills processing recycled paper
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2010 (English)In: Journal of Industrial Microbiology & Biotechnology, ISSN 1367-5435, E-ISSN 1476-5535, Vol. 37, no 10, p. 1061-1069Article in journal (Refereed) Published
Abstract [en]

Paper mills processing recycled paper suffer from biofouling causing roblems both in the mill and final product. The total bacterial ommunity composition and identification of specific taxa in the process ater and biofilms at the stock preparation and paper machine areas in a ill with recycled paper pulp was described by using a DNA-based pproach. Process water in a similar mill was also analyzed to nvestigate if general trends can be found between mills and over time. acterial community profiles, analyzed by terminal-restriction fragment ength polymorphism (T-RFLP), in process water showed that the dominant eaks in the profiles were similar between the two mills, although the verall composition was unique for each mill. When comparing process ater and biofilm at different locations within one of the mills, we bserved a separation according to location and sample type, with the iofilm from the paper machine being most different. 16S rRNA gene clone ibraries were generated and 404 clones were screened by RFLP analysis. rouping of RFLP patterns confirmed that the biofilm from the paper achine was most different. A total of 99 clones representing all RFLP atterns were analyzed, resulting in sequences recovered from nine acterial phyla, including two candidate phyla. Bacteroidetes epresented 45% and Actinobacteria 23% of all the clones. Sequences with imilarity to organisms implicated in biofouling, like Chryseobacterium pp. and Brevundimonas spp., were recovered from all samples even though he mill had no process problems during sampling, suggesting that they re part of the natural paper mill community. Moreover, many sequences howed little homology to as yet uncultivated bacteria implying that aper mills are interesting for isolation of new organisms, as well as or bioprospecting.

National Category
Medical Biotechnology (with a focus on Cell Biology (including Stem Cell Biology), Molecular Biology, Microbiology, Biochemistry or Biopharmacy)
Identifiers
urn:nbn:se:sh:diva-13704 (URN)10.1007/s10295-010-0754-1 (DOI)000282053000006 ()2-s2.0-78149361388 (Scopus ID)
Available from: 2011-12-06 Created: 2011-12-06 Last updated: 2017-12-08Bibliographically approved
Hjort, K., Bergström, M., Adesina, M. F., Jansson, J. K., Smalla, K. & Sjöling, S. (2010). Chitinase genes revealed and compared in bacterial isolates, DNA extracts and a metagenomic library from a phytopathogen-suppressive soil. FEMS Microbiology Ecology, 71(2), 197-207
Open this publication in new window or tab >>Chitinase genes revealed and compared in bacterial isolates, DNA extracts and a metagenomic library from a phytopathogen-suppressive soil
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2010 (English)In: FEMS Microbiology Ecology, ISSN 0168-6496, E-ISSN 1574-6941, Vol. 71, no 2, p. 197-207Article in journal (Refereed) Published
Abstract [en]

Soil that is suppressive to disease caused by fungal pathogens is an interesting source to target for novel chitinases that might be contributing towards disease suppression. In this study, we screened for chitinase genes, in a phytopathogen-suppressive soil in three ways: (1) from a metagenomic library constructed from microbial cells extracted from soil, (2) from directly extracted DNA and (3) from bacterial isolates with antifungal and chitinase activities. Terminal restriction fragment length polymorphism (T-RFLP) of chitinase genes revealed differences in amplified chitinase genes from the metagenomic library and the directly extracted DNA, but approximately 40% of the identified chitinase terminal restriction fragments (TRFs) were found in both sources. All of the chitinase TRFs from the isolates were matched to TRFs in the directly extracted DNA and the metagenomic library. The most abundant chitinase TRF in the soil DNA and the metagenomic library corresponded to the TRF103 of the isolate Streptomyces mutomycini and/or Streptomyces clavifer. There were good matches between T-RFLP profiles of chitinase gene fragments obtained from different sources of DNA. However, there were also differences in both the chitinase and the 16S rRNA gene T-RFLP patterns depending on the source of DNA, emphasizing the lack of complete coverage of the gene diversity by any of the approaches used.

Place, publisher, year, edition, pages
United Kingdom: Wiley-Blackwell Publishing Ltd., 2010
Keywords
metagenomic library, chitinase, terminal restriction fragment length polymorphism (T-RFLP), Streptomycetes, suppressive soil
National Category
Biological Sciences
Research subject
Environmental Studies
Identifiers
urn:nbn:se:sh:diva-6179 (URN)10.1111/j.1574-6941.2009.00801.x (DOI)000273065000003 ()2-s2.0-72949101011 (Scopus ID)
Available from: 2011-02-11 Created: 2011-02-11 Last updated: 2017-12-11Bibliographically approved
Hjort, K., Goldberg, A. V., Tsaousis, A. D., Hirt, R. P. & Embley, T. M. (2010). Diversity and reductive evolution of mitochondria among microbial eukaryotes. Philosophical Transactions of the Royal Society of London. Biological Sciences, 365(1541), 713-727
Open this publication in new window or tab >>Diversity and reductive evolution of mitochondria among microbial eukaryotes
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2010 (English)In: Philosophical Transactions of the Royal Society of London. Biological Sciences, ISSN 0962-8436, E-ISSN 1471-2970, Vol. 365, no 1541, p. 713-727Article, review/survey (Refereed) Published
Abstract [en]

All extant eukaryotes are now considered to possess mitochondria in one form or another. Many parasites or anaerobic protists have highly reduced versions of mitochondria, which have generally lost their genome and the capacity to generate ATP through oxidative phosphorylation. These organelles have been called hydrogenosomes, when they make hydrogen, or remnant mitochondria or mitosomes when their functions were cryptic. More recently, organelles with features blurring the distinction between mitochondria, hydrogenosomes and mitosomes have been identified. These organelles have retained a mitochondrial genome and include the mitochondrial-like organelle of Blastocystis and the hydrogenosome of the anaerobic ciliate Nyctotherus. Studying eukaryotic diversity from the perspective of their mitochondrial variants has yielded important insights into eukaryote molecular cell biology and evolution. These investigations are contributing to understanding the essential functions of mitochondria, defined in the broadest sense, and the limits to which reductive evolution can proceed while maintaining a viable organelle.

Keywords
mitochondria, hydrogenosomes, mitosomes, mitochondrial-like organelles
National Category
Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:sh:diva-8344 (URN)10.1098/rstb.2009.0224 (DOI)000274130200003 ()2-s2.0-77349122827 (Scopus ID)
Available from: 2011-05-04 Created: 2011-05-04 Last updated: 2017-12-11Bibliographically approved
Muleta, D., Assefa, F., Hjort, K., Roos, S. & Granhall, U. (2009). Characterization of Rhizobacteria isolated from Wild Coffea arabica L.. Engineering in Life Sciences, 9(2), 100-108
Open this publication in new window or tab >>Characterization of Rhizobacteria isolated from Wild Coffea arabica L.
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2009 (English)In: Engineering in Life Sciences, ISSN 1618-0240, E-ISSN 1618-2863, Vol. 9, no 2, p. 100-108Article in journal (Refereed) Published
Abstract [en]

Rhizobacteria from wild Arabica coffee Populations (Coffea arabica L.) in southwestern Ethiopia were isolated and characterized. The main purpose was to identify coffee-associated rhizobacteria and evaluate their potential in synthesizing the phytohormone indole acetic acid (IAA) and in degrading the ethylene precursor 1-aminocyclopropane-1-carboxylate (ACC). A total of 878 bacterial isolates were screened, of which 395 (45%) isolates were preliminarily characterized using metabolic identification kits (API). Both Gram-negative and Gram-positive bacteria were isolated, with the former group predominating (63% of cases). Based on pre-screening results of the biochemical tests, 51 of the isolates were subjected to PCR-RFLP (Restriction Fragment Length Polymorphism) analysis that yielded ten groups, of which 24 isolates were identified by 16S rRNA gene sequencing. The major genera identified were Pseudomonas (six species) and Bacillus (four species). Single species of Erwinia, Ochrobactrum and Serratia were also identified. The Erwinia sp., Serratia marcescens and many Pseudomonas spp. produced IAA, and some isolates (all Pseudomonas spp.) were also able to degrade ACC. Several of the microbes found in association with wild Arabica coffee bushes have potential agronomic importance, like e.g. Bacillus thuringiensis, which deserve further testing. According to these in vitro Studies, Isolates of Erwinia, Serratia and Pseudomonas are of particular interest in inoculant development due to their plant growth promoting traits.

Keywords
ACC, Coffee populations, Native rhizobacteria, Phytohormones
National Category
Microbiology
Identifiers
urn:nbn:se:sh:diva-8345 (URN)10.1002/elsc.200700031 (DOI)000265855200002 ()2-s2.0-66449119071 (Scopus ID)
Available from: 2011-05-04 Created: 2011-05-04 Last updated: 2017-12-11Bibliographically approved
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