Dataset Information

Screening and Evaluation of Streptomyces Species as a Potential Biocontrol Agent against a Wood Decay Fungus, Gloeophyllum trabeum.

ABSTRACT: Two-hundred and fifty-five strains of actinomycetes isolated from soil samples were screened for their antagonistic activities against four well-known wood decay fungi (WDF), including a brown rot fungus, Gloeophyllum trabeum and three white rot fungi Donkioporia expansa, Trametes versicolor, and Schizophyllum commune. A dual culture assay using culture media supplemented with heated or unheated culture filtrates of selected bacterial strains was used for the detection of their antimicrobial activity against four WDF. It was shown that Streptomyces atratus, S. tsukiyonensis, and Streptomyces sp. greatly inhibited the mycelial growth of the WDF tested compared with the control. To evaluate the biocontrol efficacy of S. atratus, S. tsukiyonensis, and Streptomyces sp., wood blocks of Pinus densiflora inoculated with three selected Streptomyces isolates were tested for weight loss, compression strength (perpendicular or parallel to the grain), bending strength, and chemical component changes. Of these three isolates used, Streptomyces sp. exhibited higher inhibitory activity against WDF, especially G. trabeum, as observed in mechanical and chemical change analyses. Scanning electron microscopy showed that cell walls of the wood block treated with Streptomyces strains were thicker and collapsed to a lesser extent than those of the non-treated control. Taken together, our findings indicate that Streptomyces sp. exhibits the potential to be used as a biocontrol agent for wood decay brown rot fungus that causes severe damage to coniferous woods.

SUBMITTER: Jung SJ

PROVIDER: S-EPMC6023252 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

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Screening and Evaluation of Streptomyces Species as a Potential Biocontrol Agent against a Wood Decay Fungus, Gloeophyllum trabeum.

Jung Su Jung SJ Kim Nam Kyu NK Lee Dong-Hyeon DH Hong Soon Il SI Lee Jong Kyu JK

Mycobiology 20180521 2

Two-hundred and fifty-five strains of actinomycetes isolated from soil samples were screened for their antagonistic activities against four well-known wood decay fungi (WDF), including a brown rot fungus, Gloeophyllum trabeum and three white rot fungi Donkioporia expansa, Trametes versicolor, and Schizophyllum commune. A dual culture assay using culture media supplemented with heated or unheated culture filtrates of selected bacterial strains was used for the detectio ...[more]

PMID: 29963315

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Project description:Brown rot fungi are primary decomposers of wood and litter in northern forests. Relative to other microbes, these fungi have evolved distinct mechanisms that rapidly depolymerize and metabolize cellulose and hemicellulose without digesting the more recalcitrant lignin. Its efficient degradative system has therefore attracted considerable attention for the development of sustainable biomass conversion technologies. However, there has been a significant lack of genetic tools in brown rot species by which to manipulate genes for both mechanistic studies and engineering applications. To advance brown rot genetic studies, we provided a gene-reporting system that can facilitate genetic manipulations in a model fungus Gloeophyllum trabeum. We first optimized a transformation procedure in G. trabeum, and then transformed the fungus into a constitutive laccase producer with a well-studied white rot laccases gene (from Trametes versicolor). With this, we built a gene reporting system based on laccase gene's expression and its rapid assay using an 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) indicator dye. The laccase reporter system was validated robust enough to allow us to test the effects of donor DNA's formats, protoplast viability, and gene regulatory elements on transformation efficiencies. Going forward, we anticipate the toolset provided in this work would expedite phenotyping studies and genetic engineering of brown rot species. IMPORTANCE One of the most ubiquitous types of decomposers in nature, brown rot fungi, has lacked robust genetic tools by which to manipulate genes and understand its biology. Brown rot fungi are primary decomposers in northern forests helping recycle the encased carbons in trees back to ecosystem. Relative to other microbes, these fungi employ distinctive mechanisms to disrupt and consume the lignified polysaccharides in wood. Its decay mechanism allows fast, selective carbohydrate catabolization, but without digesting lignin-a barren component that produces least energy trade back for fungal metabolisms. Thus, its efficient degradative system provides a great platform for developing sustainable biotechnologies for biomass conversions. However, progress has been hampered by the lack genetic tools facilitating mechanistic studies and engineering applications. Here, the laccase reporter system provides a genetic toolset for genetic manipulations in brown rot species, which we expect would advance relevant genetic studies for discovering and harnessing the unique fungal degradative mechanisms.

Project description:Fungi secrete a set of glycoside hydrolases and lytic polysaccharide monooxygenases (LPMOs) to degrade plant polysaccharides. Brown-rot fungi, such as Gloeophyllum trabeum, tend to have few LPMOs, and information on these enzymes is scarce. The genome of G. trabeum encodes four auxiliary activity 9 (AA9) LPMOs (GtLPMO9s), whose coding sequences were amplified from cDNA. Due to alternative splicing, two variants of GtLPMO9A seem to be produced, a single-domain variant, GtLPMO9A-1, and a longer variant, GtLPMO9A-2, which contains a C-terminal domain comprising approximately 55 residues without a predicted function. We have overexpressed the phylogenetically distinct GtLPMO9A-2 in Pichia pastoris and investigated its properties. Standard analyses using high-performance anion-exchange chromatography-pulsed amperometric detection (HPAEC-PAD) and mass spectrometry (MS) showed that GtLPMO9A-2 is active on cellulose, carboxymethyl cellulose, and xyloglucan. Importantly, compared to other known xyloglucan-active LPMOs, GtLPMO9A-2 has broad specificity, cleaving at any position along the β-glucan backbone of xyloglucan, regardless of substitutions. Using dynamic viscosity measurements to compare the hemicellulolytic action of GtLPMO9A-2 to that of a well-characterized hemicellulolytic LPMO, NcLPMO9C from Neurospora crassa revealed that GtLPMO9A-2 is more efficient in depolymerizing xyloglucan. These measurements also revealed minor activity on glucomannan that could not be detected by the analysis of soluble products by HPAEC-PAD and MS and that was lower than the activity of NcLPMO9C. Experiments with copolymeric substrates showed an inhibitory effect of hemicellulose coating on cellulolytic LPMO activity and did not reveal additional activities of GtLPMO9A-2. These results provide insight into the LPMO potential of G. trabeum and provide a novel sensitive method, a measurement of dynamic viscosity, for monitoring LPMO activity.ImportanceCurrently, there are only a few methods available to analyze end products of lytic polysaccharide monooxygenase (LPMO) activity, the most common ones being liquid chromatography and mass spectrometry. Here, we present an alternative and sensitive method based on measurement of dynamic viscosity for real-time continuous monitoring of LPMO activity in the presence of water-soluble hemicelluloses, such as xyloglucan. We have used both these novel and existing analytical methods to characterize a xyloglucan-active LPMO from a brown-rot fungus. This enzyme, GtLPMO9A-2, differs from previously characterized LPMOs in having broad substrate specificity, enabling almost random cleavage of the xyloglucan backbone. GtLPMO9A-2 acts preferentially on free xyloglucan, suggesting a preference for xyloglucan chains that tether cellulose fibers together. The xyloglucan-degrading potential of GtLPMO9A-2 suggests a role in decreasing wood strength at the initial stage of brown rot through degradation of the primary cell wall.

Dataset Information

Screening and Evaluation of Streptomyces Species as a Potential Biocontrol Agent against a Wood Decay Fungus, Gloeophyllum trabeum.

Publications

Screening and Evaluation of <i>Streptomyces</i> Species as a Potential Biocontrol Agent against a Wood Decay Fungus, <i>Gloeophyllum trabeum</i>.

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