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Muhammad MA, Balogun EO, Sallau AB, Chia MA, Shuaibu MN. Identification of novel laccase from cyanobacterium Microcystis flos-aquae and enhanced azo dye bioremediation potential. BIORESOURCE TECHNOLOGY 2024; 399:130587. [PMID: 38490464 DOI: 10.1016/j.biortech.2024.130587] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2024] [Revised: 03/11/2024] [Accepted: 03/12/2024] [Indexed: 03/17/2024]
Abstract
Textile industries discharge up to 280,000 tons of dye waste annually, resulting in global pollution and health risks. In Nigeria and other African countries, persistent dyes threaten aquatic life and human health. This study introduces a cost-effective, enzyme-mediated bioremediation alternative using a novel laccase from the cyanobacteriumMicrocystis flos-aquae. This purified enzyme yielded 0.55 % (w/w)with significant activity at 40 °C and pH 4.00. Kinetic studies showed the dependence of M. flos-aquae laccase on Cu2+and its inhibition by EDTA and Fe2+. The efficacy of the enzyme was demonstrated through rapid decolorization of the azo dye Cibacron Brilliant Blue over a wide temperature and pH range. As this enzyme effectively decolorizes dyes across a broad temperature and pH range, it offers a promising solution for bioremediation of textile effluents.
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Affiliation(s)
| | - Emmanuel Oluwadareus Balogun
- Department of Biochemistry, Ahmadu Bello University, Zaria, Nigeria; Africa Centre of Excellence on New Pedagogies in Engineering Education (ACENPEE), Nigeria.
| | | | - Mathias Ahii Chia
- Department of Botany, Ahmadu Bello University, Zaria, Nigeria; Department of Ecology, University of Brasilia, Brazil.
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Comparative Analysis of Transcriptomes of Ophiostoma novo-ulmi ssp. americana Colonizing Resistant or Sensitive Genotypes of American Elm. J Fungi (Basel) 2022; 8:jof8060637. [PMID: 35736120 PMCID: PMC9224576 DOI: 10.3390/jof8060637] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2022] [Revised: 05/26/2022] [Accepted: 06/11/2022] [Indexed: 12/10/2022] Open
Abstract
The Ascomycete Ophiostoma novo-ulmi threatens elm populations worldwide. The molecular mechanisms underlying its pathogenicity and virulence are still largely uncharacterized. As part of a collaborative study of the O. novo-ulmi-elm interactome, we analyzed the O. novo-ulmi ssp. americana transcriptomes obtained by deep sequencing of messenger RNAs recovered from Ulmus americana saplings from one resistant (Valley Forge, VF) and one susceptible (S) elm genotypes at 0 and 96 h post-inoculation (hpi). Transcripts were identified for 6424 of the 8640 protein-coding genes annotated in the O. novo-ulmi nuclear genome. A total of 1439 genes expressed in planta had orthologs in the PHI-base curated database of genes involved in host-pathogen interactions, whereas 472 genes were considered differentially expressed (DEG) in S elms (370 genes) and VF elms (102 genes) at 96 hpi. Gene ontology (GO) terms for processes and activities associated with transport and transmembrane transport accounted for half (27/55) of GO terms that were significantly enriched in fungal genes upregulated in S elms, whereas the 22 GO terms enriched in genes overexpressed in VF elms included nine GO terms associated with metabolism, catabolism and transport of carbohydrates. Weighted gene co-expression network analysis identified three modules that were significantly associated with higher gene expression in S elms. The three modules accounted for 727 genes expressed in planta and included 103 DEGs upregulated in S elms. Knockdown- and knockout mutants were obtained for eight O. novo-ulmi genes. Although mutants remained virulent towards U. americana saplings, we identified a large repertoire of additional candidate O. novo-ulmi pathogenicity genes for functional validation by loss-of-function approaches.
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Afreen S, Shamsi TN, Baig MA, Ahmad N, Fatima S, Qureshi MI, Hassan MI, Fatma T. A novel multicopper oxidase (laccase) from cyanobacteria: Purification, characterization with potential in the decolorization of anthraquinonic dye. PLoS One 2017; 12:e0175144. [PMID: 28384218 PMCID: PMC5383238 DOI: 10.1371/journal.pone.0175144] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2017] [Accepted: 03/21/2017] [Indexed: 01/01/2023] Open
Abstract
A novel extracellular laccase enzyme produced from Spirulina platensis CFTRI was purified by ultrafiltration, cold acetone precipitation, anion exchange and size exclusion chromatography with 51.5% recovery and 5.8 purification fold. The purified laccase was a monomeric protein with molecular mass of ~66 kDa that was confirmed by zymogram analysis and peptide mass fingerprinting. The optimum pH and temperature of the enzyme activity was found at 3.0 and 30°C using ABTS as substrate but the enzyme was quite stable at high temperature and alkaline pH. The laccase activity was enhanced by Cu+2, Zn+2 and Mn+2. In addition, the dye decolorization potential of purified laccase was much higher in terms of extent as well as time. The purified laccase decolorized (96%) of anthraquinonic dye Reactive blue- 4 within 4 h and its biodegradation studies was monitored by UV visible spectra, FTIR and HPLC which concluded that cyanobacterial laccase can be efficiently used to decolorize synthetic dye and help in waste water treatment.
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Affiliation(s)
- Sumbul Afreen
- Cyanobacterial Biotechnology laboratory, Department of Biosciences, Jamia Millia Islamia, New Delhi, India
| | - Tooba Naz Shamsi
- Department of Biotechnology, Jamia Millia Islamia, New Delhi, India
| | - Mohd Affan Baig
- Department of Biotechnology, Jamia Millia Islamia, New Delhi, India
| | - Nadeem Ahmad
- Cyanobacterial Biotechnology laboratory, Department of Biosciences, Jamia Millia Islamia, New Delhi, India
| | - Sadaf Fatima
- Department of Biotechnology, Jamia Millia Islamia, New Delhi, India
| | - M. Irfan Qureshi
- Department of Biotechnology, Jamia Millia Islamia, New Delhi, India
| | - Md. Imtaiyaz Hassan
- Center for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, New Delhi, India
| | - Tasneem Fatma
- Cyanobacterial Biotechnology laboratory, Department of Biosciences, Jamia Millia Islamia, New Delhi, India
- * E-mail:
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Durkovič J, Kačík F, Olčák D, Kučerová V, Krajňáková J. Host responses and metabolic profiles of wood components in Dutch elm hybrids with a contrasting tolerance to Dutch elm disease. ANNALS OF BOTANY 2014; 114:47-59. [PMID: 24854167 PMCID: PMC4071097 DOI: 10.1093/aob/mcu076] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2014] [Accepted: 03/24/2014] [Indexed: 05/23/2023]
Abstract
BACKGROUND AND AIMS Changes occurring in the macromolecular traits of cell wall components in elm wood following attack by Ophiostoma novo-ulmi, the causative agent of Dutch elm disease (DED), are poorly understood. The purpose of this study was to compare host responses and the metabolic profiles of wood components for two Dutch elm (Ulmus) hybrids, 'Groeneveld' (a susceptible clone) and 'Dodoens' (a tolerant clone), that have contrasting survival strategies upon infection with the current prevalent strain of DED. METHODS Ten-year-old plants of the hybrid elms were inoculated with O. novo-ulmi ssp. americana × novo-ulmi. Measurements were made of the content of main cell wall components and extractives, lignin monomer composition, macromolecular traits of cellulose and neutral saccharide composition. KEY RESULTS Upon infection, medium molecular weight macromolecules of cellulose were degraded in both the susceptible and tolerant elm hybrids, resulting in the occurrence of secondary cell wall ruptures and cracks in the vessels, but rarely in the fibres. The (13)C nuclear magnetic resonance spectra revealed that loss of crystalline and non-crystalline cellulose regions occurred in parallel. The rate of cellulose degradation was influenced by the syringyl:guaiacyl ratio in lignin. Both hybrids commonly responded to the medium molecular weight cellulose degradation with the biosynthesis of high molecular weight macromolecules of cellulose, resulting in a significant increase in values for the degree of polymerization and polydispersity. Other responses of the hybrids included an increase in lignin content, a decrease in relative proportions of d-glucose, and an increase in proportions of d-xylose. Differential responses between the hybrids were found in the syringyl:guaiacyl ratio in lignin. CONCLUSIONS In susceptible 'Groeneveld' plants, syringyl-rich lignin provided a far greater degree of protection from cellulose degradation than in 'Dodoens', but only guaiacyl-rich lignin in 'Dodoens' plants was involved in successful defence against the fungus. This finding was confirmed by the associations of vanillin and vanillic acid with the DED-tolerant 'Dodoens' plants in a multivariate analysis of wood traits.
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Affiliation(s)
- Jaroslav Durkovič
- Department of Phytology, Technical University, 96053 Zvolen, Slovakia
| | - František Kačík
- Department of Chemistry and Chemical Technologies, Technical University, 96053 Zvolen, Slovakia
| | - Dušan Olčák
- Department of Physics, Technical University of Košice, 04200 Košice, Slovakia
| | - Veronika Kučerová
- Department of Forest Protection and Game Management, Technical University, 96053 Zvolen, Slovakia
| | - Jana Krajňáková
- Department of Agricultural and Environmental Science, University of Udine, 33100 Udine, Italy Department of Biology, University of Oulu, 90014 Oulu, Finland
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Luis P, Gauthier A, Trouvelot S, Poinssot B, Frettinger P. Identification of Plasmopara viticola genes potentially involved in pathogenesis on grapevine suggests new similarities between oomycetes and true fungi. PHYTOPATHOLOGY 2013; 103:1035-44. [PMID: 23634808 DOI: 10.1094/phyto-06-12-0121-r] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Plant diseases caused by fungi and oomycetes result in significant economic losses every year. Although phylogenetically distant, these organisms share many common features during infection. We identified genes in the oomycete Plasmopara viticola that are potentially involved in pathogenesis in grapevine by using fungal databases and degenerate primers. Fragments of P. viticola genes encoding NADH-ubiquinone oxidoreductase (PvNuo), laccase (PvLac), and invertase (PvInv) were obtained. PvNuo was overexpressed at 2 days postinoculation (dpi), during the development of the first hyphal structures and haustoria. PvLac was overexpressed at 5 dpi when genes related to pterostilbene biosynthesis were induced in grapevine. Transcript level for PvInv increased between 1 and 4 dpi before reaching a plateau. These results might suggest a finely tuned strategy of infection depending on nutrition and plant response. Phylogenetic analyses of PvNuo showed that P. viticola clustered with other oomycetes and was associated with brown algae and diatoms, forming a typical Straminipila clade. Based on the comparison of available sequences for laccases and invertases, the group formed by P. viticola and other oomycetes tended to be more closely related to Opisthokonta than to Straminipila. Convergent evolution or horizontal gene transfer could explain the presence of fungus-like genes in P. viticola.
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Laccase is upregulated via stress pathways in the phytopathogenic fungus Sclerotinia sclerotiorum. Fungal Biol 2013; 117:528-39. [DOI: 10.1016/j.funbio.2013.05.005] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2012] [Revised: 05/22/2013] [Accepted: 05/26/2013] [Indexed: 11/18/2022]
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Durkovic J, Canová I, Lagana R, Kucerová V, Moravcík M, Priwitzer T, Urban J, Dvorák M, Krajnáková J. Leaf trait dissimilarities between Dutch elm hybrids with a contrasting tolerance to Dutch elm disease. ANNALS OF BOTANY 2013; 111:215-27. [PMID: 23264236 PMCID: PMC3555532 DOI: 10.1093/aob/mcs274] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2012] [Accepted: 11/13/2012] [Indexed: 05/15/2023]
Abstract
BACKGROUND AND AIMS Previous studies have shown that Ophiostoma novo-ulmi, the causative agent of Dutch elm disease (DED), is able to colonize remote areas in infected plants of Ulmus such as the leaf midrib and secondary veins. The objective of this study was to compare the performances in leaf traits between two Dutch elm hybrids 'Groeneveld' and 'Dodoens' which possess a contrasting tolerance to DED. Trait linkages were also tested with leaf mass per area (LMA) and with the reduced Young's modulus of elasticity (MOE) as a result of structural, developmental or functional linkages. METHODS Measurements and comparisons were made of leaf growth traits, primary xylem density components, gas exchange variables and chlorophyll a fluorescence yields between mature plants of 'Groeneveld' and 'Dodoens' grown under field conditions. A recently developed atomic force microscopy technique, PeakForce quantitative nanomechanical mapping, was used to reveal nanomechanical properties of the cell walls of tracheary elements such as MOE, adhesion and dissipation. KEY RESULTS 'Dodoens' had significantly higher values for LMA, leaf tissue thickness variables, tracheary element lumen area (A), relative hydraulic conductivity (RC), gas exchange variables and chlorophyll a fluorescence yields. 'Groeneveld' had stiffer cell walls of tracheary elements, and higher values for water-use efficiency and leaf water potential. Leaves with a large carbon and nutrient investment in LMA tended to have a greater leaf thickness and a higher net photosynthetic rate, but LMA was independent of RC. Significant linkages were also found between the MOE and some vascular traits such as RC, A and the number of tracheary elements per unit area. CONCLUSIONS Strong dissimilarities in leaf trait performances were observed between the examined Dutch elm hybrids. Both hybrids were clearly separated from each other in the multivariate leaf trait space. Leaf growth, vascular and gas exchange traits in the infected plants of 'Dodoens' were unaffected by the DED fungus. 'Dodoens' proved to be a valuable elm germplasm for further breeding strategies.
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Mot AC, Silaghi-Dumitrescu R. Laccases: Complex architectures for one-electron oxidations. BIOCHEMISTRY (MOSCOW) 2012; 77:1395-407. [DOI: 10.1134/s0006297912120085] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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Ligninolytic Fungal Laccases and Their Biotechnological Applications. Appl Biochem Biotechnol 2009; 160:1760-88. [DOI: 10.1007/s12010-009-8676-y] [Citation(s) in RCA: 192] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2009] [Accepted: 05/18/2009] [Indexed: 10/20/2022]
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Hoegger PJ, Kilaru S, James TY, Thacker JR, Kües U. Phylogenetic comparison and classification of laccase and related multicopper oxidase protein sequences. FEBS J 2006; 273:2308-26. [PMID: 16650005 DOI: 10.1111/j.1742-4658.2006.05247.x] [Citation(s) in RCA: 285] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A phylogenetic analysis of more than 350 multicopper oxidases (MCOs) from fungi, insects, plants, and bacteria provided the basis for a refined classification of this enzyme family into laccases sensu stricto (basidiomycetous and ascomycetous), insect laccases, fungal pigment MCOs, fungal ferroxidases, ascorbate oxidases, plant laccase-like MCOs, and bilirubin oxidases. Within the largest group of enzymes, formed by the 125 basidiomycetous laccases, the gene phylogeny does not strictly follow the species phylogeny. The enzymes seem to group at least partially according to the lifestyle of the corresponding species. Analyses of the completely sequenced fungal genomes showed that the composition of MCOs in the different species can be very variable. Some species seem to encode only ferroxidases, whereas others have proteins which are distributed over up to four different functional clusters in the phylogenetic tree.
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Affiliation(s)
- Patrik J Hoegger
- Georg-August-University Göttingen, Institute of Forest Botany, Göttingen, Germany.
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Jacobs J, Roe JL. SKS6, a multicopper oxidase-like gene, participates in cotyledon vascular patterning during Arabidopsis thaliana development. PLANTA 2005; 222:652-66. [PMID: 15986216 DOI: 10.1007/s00425-005-0012-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2005] [Accepted: 04/27/2005] [Indexed: 05/03/2023]
Abstract
SKU5-Similar 6 (SKS6) is a one of a large gene family of 19 members in Arabidopsis thaliana (L.) Heynh that encode multicopper oxidase-like proteins that are related to ferroxidases, ascorbate oxidases and laccases. Only one member of the family has been previously studied; Skewed5 (SKU5) is involved in the control of root growth. The encoded SKS6 protein, like SKU5 appears to lack a functional copper-binding site and is most closely related to Bp10 from Brassica napus and Ntp303 from Nicotiana tobacum. The SKS6 promoter contains many putative regulatory sites and differential expression of an SKS6::GUS reporter gene revealed selective induction in several seedling tissues including guard cells, root cortex cells, and leaf margin hydathodes. It was also expressed later in flower development in flower primordia, ovules, and the abscission zones of seeds and siliques. Furthermore, SKS6 was upregulated in roots in response to treatment of seedlings with the hormones abscisic acid, indole-3 acetic acid, 2,4-dichlorophenoxyacetic acid and aminocyclopropane-1-carboxylate. A loss-of function sks6-1 T-DNA insertion allele revealed that cotyledon vascular patterning is affected in the mutant, suggesting a role for the protein in metabolism of nutrients or hormones in the hydathodes, the sites of auxin synthesis and chemical recycling.
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Affiliation(s)
- Jolanta Jacobs
- Division of Biology, Kansas State University, Ackert Hall, Manhattan, KS 66506, USA
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Iyer G, Chattoo BB. Purification and characterization of laccase from the rice blast fungus,Magnaporthe grisea. FEMS Microbiol Lett 2003; 227:121-6. [PMID: 14568157 DOI: 10.1016/s0378-1097(03)00658-x] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
A 70-kDa extracellular laccase was purified from the rice blast fungus Magnaporthe grisea using gel filtration and ion exchange chromatography The procedure provided 282-fold purification with a specific enzyme activity of 225.91 U mg(-1) and a yield of 11.92%. The enzyme oxidized a wide range of substrates. The highest level of oxidation was detected with syringaldazine as the substrate. Using syringaldazine as the substrate, the enzyme exhibited a pH optimum of 6 and temperature optimum of 30 degrees C, and its K(m) was 0.118 mM. The enzyme was strongly inhibited by Cu-chelating agents.
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Affiliation(s)
- Gopal Iyer
- Plant and Microbial Biology Department, 111 Koshland Hall, University of California, Berkeley, CA 94720, USA.
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Untersuchungen über das Auftreten der Erreger der Holländischen Ulmenwelke in Österreich. ACTA ACUST UNITED AC 2001. [DOI: 10.1007/bf02796095] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Robles A, Lucas R, Gálvez A. Phenol-oxidase (laccase) activity in strains of the hyphomycete Chalara paradoxa isolated from olive mill wastewater disposal ponds. Enzyme Microb Technol 2000; 26:484-490. [PMID: 10771050 DOI: 10.1016/s0141-0229(99)00197-0] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Production of laccase activity by nine strains of Chalara paradoxa isolated from olive mill wastewater disposal ponds were studied. Enzyme extracts obtained from cultured broths by adsorption on hydroxyapatite showed a single band of laccase activity on ABTS after polyacrylamide gel electrophoresis (PAGE). They showed small mobility differences, with molecular masses of 67 to 68 kDa. Enzymes from the different strains oxidized a variety of phenolic and non-phenolic substances, and they could be divided into two groups according to their relative activities on substrates. All laccases showed a dual pH dependence of activity, with a maximum in the range of pH 3.0 to 4.5 for ABTS, o-dianisidine and 2,6-dimethoxyphenol, and pH 6.0 (Group 1) or pH 6.5 (Group 2) for syringaldazine and other substrates. Optimal temperatures were in the range of 10 to 28 degrees C for two strains (maximum at 10 degrees C) and 10 to 37 degrees C for the rest. The different enzymes were partially inactivated by heating at 60 degrees C and totally inactivated at 70 degrees C. Laccases were stable in a pH range of 3.0 to 9.0 (except for strain 36A, which was partially inactivated at pH 3.0), but became inactivated at pH 2.0. Altogether these data suggest that Ch. paradoxa strains produce different laccase isoenzymes.
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Affiliation(s)
- A Robles
- Departmento Microbiología, Universidad de Jaén, 23071-, Jaén, Spain
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Binz T, D'Mello N, Horgen PA. A comparison of DNA methylation levels in selected isolates of higher fungi. Mycologia 1998. [DOI: 10.1080/00275514.1998.12026971] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Affiliation(s)
- Thomas Binz
- Biology Group, University of Toronto at Mississauga, Mississauga, Ontario, L5L 1C6 Canada
| | - Nisha D'Mello
- Biology Group, University of Toronto at Mississauga, Mississauga, Ontario, L5L 1C6 Canada
| | - Paul A. Horgen
- Biology Group, University of Toronto at Mississauga, Mississauga, Ontario, L5L 1C6 Canada
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Differential phenol-induced laccase activity and total oxidative capacity of the S and P intersterility groups of the conifer root pathogen Heterobasidion annosum. Microbiol Res 1998. [DOI: 10.1016/s0944-5013(98)80024-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Binz T, Gremaud C, Canevascini G. Production and purification of an extracellular β-galactosidase from the Dutch elm disease fungusOphiostoma novo-ulmi. Can J Microbiol 1997. [DOI: 10.1139/m97-146] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The causal agents of Dutch elm disease, Ophiostoma ulmi (isolate H200) and Ophiostoma novo-ulmi (isolate CKT-11), secreted similar amounts of β-galactosidase in liquid shake cultures when grown on galacturonic acid or sodium pectate (1.45 ± 0.16 and 1.03 ± 0.24 nkat∙mL−1for O. ulmi, respectively, and 1.30 ± 0.08 and 1.28 ± 0.26 nkat∙mL−1for O. novo-ulmi, respectively). Rhamnose and pectin also stimulated secretion but to a lesser extent, whereas on glucose, enzyme activity was barely detectable (≤0.01 nkat∙mL−1). Ophiostoma novo-ulmi was shown by Q-Sepharose chromatography to form two β-galactosidases, named β-galactosidases I and II. In cultures grown on galacturonic acid β-galactosidase I accounted for approximately 75% of the total activity in the culture filtrate. β-Galactosidase I was further purified to apparent electrophoretic homogeneity by means of Sephacryl gel filtration chromatography, chromatofocusing, and Superdex75 gel filtration. The molecular mass of the enzyme was 135 kDa by SDS–PAGE and 123 kDa by gel filtration. Its isoelectric point, determined by chromatofocusing, was 4.9. The optimal pH for enzyme activity was 5.8 and the optimal temperature was 50 °C. The Kmvalues for p-nitrophenyl β-D-galactopyranoside and lactose were 7.52 and 14.23 mM, respectively, and the maximum velocities for these substrates were 1733 and 355 nkat∙mg protein−1, respectively. The Kivalue for D(−)-galactonic acid γ-lactone was 2.29 mM.Key words: Dutch elm disease, β-galactosidase, Ophiostoma ulmi, Ophiostoma novo-ulmi.
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