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Extracellular substance from the white rot basidiomycete Irpex lacteus involved in wood degradation
1992 - IRG/WP 92-1571
Cellulases, phenol oxidase, and a substance that both produced and reduced H2O2 were isolated from cultures containing wood or glucose on which the white-rot fungus Irpex lacteus was growing. The rate of wood degradation by the fungus with different amounts of glucose in the medium was measured. More of the substance that produced and reduced H2O2 was found extracellularly in cultures containing wood than in cultures containing glucose. The extent of one-electron oxidation activity of the extracellular substance was correlated with that of the wood-degrading activity, but the extent of phenol oxidase activity was not. The extracellular substance catalyzed the hydroxylation of phenol to hydroquinone and catechol in the presence of H2O2 or of NADH and O2. The substance seemed to be a glycopeptide containing Fe(II) and its molecular weight was very low.
H Tanaka, T Hirano, G Fuse, A Enoki

The involvement of extracellular substances for the generation of hydroxyl radical during wood degradation by white-rot fungi
1997 - IRG/WP 97-10218
The activities of one-electron oxidation, hydroxyl radical generation, and phenol oxidase during the incubation of cultures of four white-rot fungi containing either glucose or wood were periodically measured. Further, their degradation activities against wood were examined during the course of cultivation. The generation of hydroxyl radical was correlated to the activity of wood degradation and it was not dependent upon the activity of oxidants such as phenol oxidase. The generation of hydroxyl radical was mostly due to the extracellular low molecular weight substances that catalyzed redox reaction between electron donors and O2 to produce H2O2 via O2 and to reduce H2O2 to HO·.The substances reduced Fe(III) to Fe(II) and strongly absorbed Fe(II).
H Tanaka, S Itakura, A Enoki

Sequestration of copper ions by the extracellular mucilaginous material (ECMM) of two wood rotting basidiomycetes
2004 - IRG/WP 04-10533
The radial growth rate of colonies originating from either whole or ECMM-free inocula of Coriolus versicolor was investigated. The presence of ECMM allowed colonies to maintain higher growth rates than those form ECMM-free inocula up to 2 mM CuSO4 in the medium. The ECMM of C. versicolor and G. trabeum was able to reduce the diffusion of copper ions in solution. The ‘raw’ ECMM of both fungi had a greater ability to reduce the diffusion of copper ions than ECMM which had been subject to dialysis to remove soluble, low molecular weight components. The ‘insoluble’ fraction of ECMM for both species was more effective than the ‘soluble’ fraction at reducing the diffusion of copper ions. It is concluded that ECMM confers some protection to hyphae against the toxic effects of copper ions on growth in vivo and that this due to the binding of copper ions to both the polysaccharide and to low molecular weight components of the ECMM
D Vesentini, D J Dickinson, R J Murphy

The influence of crystalline and amorphous cellulose on extracellular hydrogen peroxide production by brown-rot fungi
1991 - IRG/WP 1482
The production of hydrogen peroxide (H2O2) has been suggested to play a key role in the degradation of wood by wood-rotting fungi. The production of extracellular hydrogen peroxide was studied by a quantitative method which detects the oxidation of the 2,2-azinobis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) by H2O2 and horseradish peroxidase (HRP) in liquid culture medium. The carbon sources used were crystalline and amorphous cellulose. Two brown-rotters, Serpula lacrymans and Poria placenta, were able to produce clearly detectable amounts of extracellular hydrogen peroxide in liquid medium which contained crystalline cellulose as carbon source. No detectable H2O2 was produced in conditions where amorphous medium was used as carbon source. This result suggests that the conformational structure of the substrate may induce H2O2 production by brown-rot fungi.
A-C Ritschkoff, L Viikari

Electron microscopic detection and chemical analysis of three-lamellar structures in wood-destroying fungi
1984 - IRG/WP 1240
In the course of transmission electron microscopical investigations of pine wood decay by various brown- and white-rot fungi extracellular three-lamellar structures (TLS) formed by the fungi were found in specimens stained with ruthenium red. These structures occured in the lumen of the wood cell surrounding the hypha at the outermost layer of the fungal cell wall. In the course of the investigations these structures were also detected in fungi cultivated with glucose on a rotary shaker, where they showed forms similar to tubuli and vesicles. The three-lamellar structures formed by the white-rot fungus Sporotrichum pulverulentum, which were contained in the outermost cell wall layer, were isolated by disintegration of the fungal pellet and subsequent digestion of the fungal cell wall by snail enzyme. It was found that these structures are resistant to the enzymatic digestion and are composed of 80 to 90% carbohydrates, mainly consisting of glucose monomeres, 5 to 10% proteins, containing 5 fractions with molecular weights between 30000 and 200000, and finally 5 to 10% lipids which do not contain any phospholipid.
R Foisner, K Messner, H Stachelberger, M Röhr

Extracellular layers of wood decay fungi and copper tolerance
1983 - IRG/WP 1180
Extracellular layers around the hyphae of brown, white and soft rot fungi have been examined using electron microscopy. These layers were isolated for identification. Particular interest was directed towards the extracellular layers of copper-tolerant soft rot fungi.
D M Francis, L E Leightley

Lignin degradation by wood-degrading fungi
1986 - IRG/WP 1310
The wood-degrading white-rot fungus Phanerochaete chrysosporium, has been the subject of intensive research in recent years and, based upon isolation of the extracelluar enzyme ligninase, major advances have now been made toward elucidating the mechanism by which this fungus degrades lignin. From these developments, a model emerges which could explain the process by which wood-degrading fungi in general, attack lignin.
P J Harvey, H E Schoemaker, J M Palmer

The distribution of introduced acetyl groups and a linseed oil model substance in wood examined by microautoradiography and ESEM
2000 - IRG/WP 00-40169
Microautoradiography, a photographic method that shows the localization of substances labelled with radioactive isotope, and Environmental Scanning Electron Microscopy (ESEM) were combined to enhance sensitivity, resolution and reliability for examination of the distribution of introduced substances in wood. The preparation of microautoradiographs is less complicated when investigated with ESEM and the preparation of ESEM-samples is quick and easy compared to a conventional SEM. When investigating microautoradiographs with ESEM, the wood structure is observed underneath the almost transparent photographic film. Silver grains, indicating the location of studied substances, are clearly distinguish from the wood material. The technique was used in two case studies for examination of cell wall penetration and distribution in pine sapwood. The distribution of acetyl groups, introduced by acetylation with acetic anhydride, and the distribution of a linseed oil model substance, triglycerol trioleate, were examined. Examinations of introduced acetyl groups showed an even distribution of acetyl groups in the wood cell wall at acetylation level of about 5, 15 and 20% (weight gain). Examination of the linseed oil model substance, glycerol trioleate, showed the presence of the model substance on applied surfaces, in rays and in lumen of some latewood cells. No cell wall penetration was observed.
M Rosenqvist

Soft rot studies on CCA treated eucalypt power transmission poles
1981 - IRG/WP 1132
Initial results found for sixty CCA treated eucalypt poles, from a soft-rot survey are discussed. Retentions of CCA within above and below ground pole samples were variable. The variation was attributed mostly to biodegradation and effect of soil environment, rather than leaching. Bacterial decay was found in many poles and was severe in some cases. Although found in the presence of soft-rot decay, bacterial attack also dominated in regions of the CCA treated sapwood. Timber suffering such attack was appreciably softened. Extracellular layers have been observed around fungal hyphae from agar cultures and within soft-rot cavities. Fungal isolates were used to produce such polysaccharides. This material was used to observe the effect of addition of copper and quaternary ammonium compound. Solutions of extracellular polysaccharides exhibited some ability to bind copper and remove it from solution. In the presence of a quaternary compound polysaccharide was precipitated from solution.
L E Leightley

Immunolocalization of extracellular metabolites from Tyromyces palustris
1991 - IRG/WP 1491
Polyclonal antisera produced to extracellular metabolites from the brown-rot fungus Tyromyces palustris was used in immunogold TEM studies. Gold labelling was detected in the fungal cell wall and extracellular slime layer but little or sporadic labelling was noted within the cytoplasm of the fungal hyphae. Gold particles were also found within the wood cell wall of Pinus densiflora decayed by Tyromyces palustris. Erosion of wood cell wall and penetration of hyphae in the wood cell wall were frequently observed. The degradation pattern of lignocellulose by brown-rot fungus was also discussed.
Yoon Soo Kim

SEM investigation of the production of extracellular mucilaginous material (ECM) by some wood inhabiting and wood decay fungi when grown in wood
1997 - IRG/WP 97-10193
Previous reports have illustrated the involvement of extracellular mucilage (ECM) in wood decay by Basidiomycetes. Its production is investigated in a range of stain, mould and soft rot fungi in Corsican pine, Scots pine and European beech. Fungi examined were: Chaetomium globosum, Ceratocystis coerulescens, Trichoderma harzianum, Ophiostoma piceae, Mucor sp. and Penicillium. sp. The samples were examined in the frozen hydrated (FH) and freeze dried (FD) conditions using SEM. Most of the fungi tested produced ECM with the amounts produced varying from one fungus to the other. Different morphological forms of the mucilage were observed. ECM produced by C. coerulescens was mostly fibrillar, and interesting morphological forms of the ECM were associated with hyphae of T. harzianum. Small amounts of mucilage were produced by O. piceae and Penicillium sp. Further investigation is necessary on the ECM production in Mucor sp.
A R Abu, D J Dickinson, R J Murphy

Reaction of osmium tetroxide with a diphenolic compound as a model substance for demethylated lignin
1986 - IRG/WP 1303
By using caffeic acid as a model substance for diphenolic moieties of demethylated lignin it was found that electron dense particles called by the authors "osmiophilic particles" in former papers are reaction products of OsO4 with the model substance. By these products it is possible to indicate the enzymatic demethylation of lignin taking place during wood decay. The appearance of the electron dense particles in decay patterns described in earlier papers is briefly summarized.
K Messner, E Srebotnik

The effect of tunicamycin on production and secretion of extracellular carbohydrate-degrading enzymes by Postia placenta
1988 - IRG/WP 1342
The extracellular carbohydrate-degrading enzymes of wood-decay fungi are usually heavily glycosylated and therefore stable under most denaturing conditions. It is unlikely that wood decay can be prevented by simply inactivating these enzymes. Tunicamycin, an antibiotic produced by Streptomyces lysosuperificus, prevents the glycosylation of glycoproteins and can interfere with the secretion of these enzymes. The effect of tunicamycin on the production of extracellular carbohydrate-degrading enzymes of Postia placenta was determined in liquid culture. Enzyme production was inhibited at concentrations of 2.5-5 mg/ml; glycosidases were more sensitive than glycanases. Colony morphology was greatly altered at these concentrations, but dry weights decreased only 20-30%. The thermostabilities of xylanase and a-galactosidase, and the pH stability of xylanase, decreased when formed in the presence of low concentrations of tunicamycin. This suggests that the enzymes are produced in an active but nonglycosylated (or underglycosylated) form. The deglycosylation of glycoproteins may be a physiologically specific means of controlling wood-decay fungi.
J A Micales, T L Highley

SEM investigation of the production of extracellular mucilaginous material (ECM) by some wood inhabiting and wood decay fungi when grown on inert surfaces
1997 - IRG/WP 97-10194
A range of wood inhabiting and wood decay fungi have been studied for their production of extracellular mucilage when grown on inert surfaces, for comparison with their growth on wood. The species tested were: Coniophora puteana, Coriolus versicolor, Chaetomium globosum, Trichoderma harzianum, Ceratocystis coerulescens, Ophiostoma piceae, Mucor sp. and Penicillium sp. They were grown on plastic meshes, melinex sheets and glass cover slips and were examined in the freeze dried (FD) and frozen hydrated (FH) conditions. For most of the fungi tested, the ECM production was induced upon contact with the inert surface, although the amount of the ECM produced was far less than that produced by the same fungi in wood. The ECM produced by C. puteana and C. versicolor was similar and more extensive, when compared to that produced by the other fungi. ECM was not produced by Mucor sp. and Penicillium sp.
A R Abu, R J Murphy, D J Dickinson

Utilization of nitrogenous substance by Serpula lacrymans
1989 - IRG/WP 1397
When Serpula lacrymans degrades wood, the fungus is considered to have to assimilate nitrogen, which is not abundant in the wood, from the third material. The strands/mycelium has grown into the soil under the floor of the wooden house damaged by the dry rot fungus. The authors analyzed the soil samples collected from the ground under the floors of the dryrotted houses. The samples which were collected from the ground covered with the strands/ mycelium of the fungus contained less quantity of nitrogen than the ones from the ground not covered with them.
S Doi, I Togashi

Proposed model for the penetration and decay of wood by the hyphal sheath of the brown-rot fungus Postia placenta
1989 - IRG/WP 1391
Scanning electron microscopy (SEM) of Pinus sp. decayed by the brown-rot fungus Postia placenta confirmed the existence of extracellular membranous structures previously described by transmission electron microscopy (TEM). These structures appear to be an integral part of the hyphal sheath and assume a variety of forms including lamellar sheets, fibrils, and vesicles. These structures were observed (a) on the surface of hyphae, (b) extending from hyphae into the wood surface and covering the S3 layer, (c) embedded in the hyphal sheath and, (d) penetrating into the wood cell wall layers from S3 - S3. We conclude that penetration of the wood cell wall by the complex, multistructured hyphal sheath facilitates the decay process in an orderly and linear progression. The directionality of the decay process appears to alter the fiber orientation of individual wood cell wall layers. This model offers an alternative hypothesis to simple diffusion of wood degrading agents during wood decay by Postia placenta.
F Green III, M J Larsen, L L Murmanis, T L Highley

The EWPMG proposal for the environmental risk assessment of wood preservatives
2001 - IRG/WP 01-50166-09
This paper reviews the protocol prepared by the European Wood Preservative Manufacturer's Group, which could be used by an applicant for product approval under the Biocidal Products Directive 98/8/EC, to produce a risk assessment for an active substance or product in the Product Type 8 Wood Preservatives, in support of the application. The background and scope of the protocol are reviewed. The principles of environmental risk assessment are reviewed with particular reference to wood preservatives. The protocol is described and an example flowchart is included.
E F Baines

Extracellular hydrogen peroxide producing and hydrogen peroxide reducing compounds of wood decay fungi
1991 - IRG/WP 1516
Extracellular H2O2-producing and H2O2-reducing compounds were isolated from wood-containing cultures of all the white-rot and brown-rot fungi and Ascomycetes which well degraded wood, but were not detected in the culture of the fungi which degraded little wood. The compounds are glycopeptides with a low molecular weight, require H2O2 for one-electron oxidation, catalyze the redox reaction between an electron donor such as NADH or ascorbic acid and O2 to produce H2O2 via O2·-, and produce ·OH by Fenton's reaction between the ferrous iron bound to the ligands and H2O2. The compounds show no phenol-oxidase activity and catalyze the hydroxylation of phenol to catechol and hydroquinone in the presence of H2O2.
A Enoki, G Fuse, H Tanaka

Control of sapwood-inhabiting fungi by fractionated extracellular metabolites from Coniophora puteana
1991 - IRG/WP 1494
The objective of this study was to test the fractionated metabolites released by Coniophora puteana for their antagonistic activity against the sapstain fungi Ceratocystis coerulescens and Aureobasidum pullulans, and the molds Asperigillus niger and Penicillium spp. The acetone-soluble fraction obtained from the culture filtrate prepared from Coniophora puteana grown on 6% malt extract agar inhibited mycelial growth in a plate bioassay. The <5k-Da fraction separated from the acetone-soluble fraction also inhibited mycelial growth in the plate bioassay and prevented attack by Ceratocystis coerulescens in wood.
S C Croan, T L Highley

Immuno-electron microscopic localization of extracellular metabolites in spruce wood decayed by brown-rot fungus Postia placenta
1990 - IRG/WP 1441
Degradation by Postia placenta in spruce and birch wood was shown to occur not only in the wood cell wall but also in the middle lamellae region. Middle lamellae was often found to be degraded along the centerline so that cells could separate along this line. Extracellular membrane structures were found surrounding the hyphae and this matrix labelled positively with antisera produced to Postia placenta extracellular metabolites. This matrix was also visible in the secondary wall of degraded birch wood. Antisera labelling was also noted in the secondary cell walls of the wood cells, but not in the middle lamellae region.
Y S Kim, B Goodell, J Jellison

Effects of cyproconazole and copper sulphate on the length of the hyphal growth unit (HGU) of the white-rot fungus Coriolus versicolor
2003 - IRG/WP 03-10473
Wood decay basidiomycetes have been shown to produce appreciable quantities of extracellular mucilaginous materials (ECMM). The relationship between ECMM and total biomass production has been investigated in the white-rot fungus Coriolus versicolor (CTB 863 A). Differences in the amount of ECMM produced by the fungus proportionally to the total biomass, were observed under a range of physiological conditions, including the presence of biocides. Such differences suggest that stress may have a role in stimulating an increase in the amount of ECMM produced by C. versicolor. The rationale behind this study is that the increase in the proportional amount of ECMM produced by the organism under a range of different stress conditions, may be explained by the hypothesis of the Hyphal Growth Unit length (HGU). The results presented in this paper support the hypothesis that the length of the HGU is strongly related to the environmental conditions. Cyproconazole at 0.1 mmols l-1 in the growth medium, reduced total biomass by approximately 50% and decreased the length of the HGU by approximately 50%. This change in the HGU length reflects a change in the hyphal behaviour to a highly brached mycelial habit. Associated with this was a 100% increase in the proportion of ECMM in relation to the hyphal biomass. Since ECMM is known to be secreted at the tip of actively growing hyphae, it is hypothesised that by adjusting the length of the HGU, filamentous fungi are able to produce a highly branched mycelium, which leads to the production of high levels of ECMM. This could offer protection against adverse environmental conditions, such as the presence of biocides. These results are discussed with regard to the possible role(s) of ECMM in the decay process and its interaction with preservative treatments.
D Vesentini, D J Dickinson, R J Murphy

Cytoplasmic and extracellular localization of manganese II dependent peroxidase(s) in white rot fungi during degradation of woody materials
1989 - IRG/WP 1416
The manner by which lignin is degraded in-situ in natural substrates by white rot fungi still remains a controversial issue particularly the distribution and role(s) played by lignin degrading enzymes (i.e. manganese II peroxidase and lignin peroxidase). In the present study, use was made of anti-manganese II peroxidase and immunolabelling techniques in conjunction with transmission electron microscopy (TEM) to study the spatial distribution of manganese II peroxidase during degradation of wood and woody fragments by Phanerochaete chrysosporium and Lentinus edodes. Intracellularly, manganese II peroxidase was found localized in the peripheral regions of the fungal cell cytoplasm in association with both the outer cell membrane and membranes within characteristic vesicular bodies. In addition the enzyme was frequently found localized at the interfacial regions of the cell membrane and inner fungal cell wall. Using double immunolabelling procedures and in addition anti-lignin peroxidase, the cytoplasmic distribution of the two lignin degrading enzymes was compared. Both enzymes showed a fairly similar peripheral cytoplasmic localization although manganese II peroxidase tended to be more concentrated compared to lignin peroxidase in peripheral vesicular bodies. Extracellularly, and in solid wood samples manganese II peroxidase was found localized in all wood cell wall regions of either Betula verrucosa, Populus sp. or Fagus sylvatica decayed by either Phanerochaete chrysosporium or Lentinus edodes at both early and late stages of degradation. In particular, manganese II peroxidase was localized in characteristic zones of degradation produced within the secondary wood cell wall regions. These regions displayed a more open structure compared to unattacked wood cell walls and were easily penetrated by lignin degrading enzymes as judged by infiltration and double immunolabelling studies with highly purified and partially purified manganese II and lignin peroxidases. With Lentinus edodes a very characteristic pattern of lignin degradation was noted in which the middle lamella regions between wood cells was selectively degraded. In these regions manganese II peroxidase was found concentrated and associated with its degrading matrix. An extracellular distribution of manganese II peroxidase associated with wood fragments was also observed in liquid cultures of Phanerochaete chrysosporium grown under conditions optimal for peroxidase production. Despite the immersed conditions, similarities between the patterns of attack and extracellular distribution of the enzyme as for solid wood were noted. With both solid wood and wood fragments, manganese II peroxidase penetration was restricted to regions showing structurally modification, and penetration into undecayed cell walls was not observed. The present work suggests a close substrate-enzyme association during wood cell wall and lignin degradation under natural conditions, and in addition, a close correlation between changes in the micromorphology of decay and manganese II peroxidase distribution. Possible reasons for the failure of previous and similar immunolabelling studies to show such a correlation with lignin degrading enzymes are briefly discussed.
G F Daniel, B Pettersson, T Nilsson, J Volc

Investigation of extracellular mucilaginous material in some wood decay fungi
1996 - IRG/WP 96-10188
The external morphology of the extracellular mucilagenous material (ECM) produced by Coriolus versicolor and Coniophora puteana during colonization of Scots pine and beech was studies using SEM. Specimens were examined in the frozen hydrated, freeze-dried and critical point dried state. All technics produced artefacts but the ECM was best preserved when examined the frozen hydated state. Critical point drying damaged the ECM extensively but was useful in partly explaining its nature. ECM was found to line much of the lumen and coated aerial fungal mycelium. Some morphological patterns in which the ECM and fungal hyphae were involved are also descibed.
A R Abu, D J Dickinson, R J Murphy

Extracellular hydrogen peroxide-producing and one-electron oxidation system of brown-rot fungi
1990 - IRG/WP 1445
Wood-component-degrading compounds involved in the initial degradation of the cellulose and lignin in wood were isolated from wood-containing culture of brown-rot fungi, Gloeophyllum trabeum and Tyromyces palustris and partially purified by gel filtration on Sephadex G-25 and DEAE-Sepharose ion-exchange chromatography. The compounds were glycoproteins. The molecular weights of the glycoproteins as determined by gel filtration were very small and about 1,600-2,000. The one-electron oxidation activity of the peptides was determined by measuring ethylene production from 2-keto-4-thiomethylbutyric acid (KTBA). The peptides contained ferrous iron,required H2O2 for KTBA oxidation, were capable of catalyzing the oxidation of NADH to produce H2O2 in the presence of 02 and showed little phenol-oxidase activity under conditions giving high activity against KTBA. The ferrous iron combined with the glycopeptides was oxidized to the ferric state by H2O2.
A Enoki, S Yoshioka, H Tanaka, G Fuse

Extracellular mucilage (ECM) in wood decay basidiomycetes
2002 - IRG/WP 02-10439
The ability of wood decay basidiomycetes to produce extracellular mucilage (ECM) and its relationship with total biomass production is being investigated. Growth and ECM production by the brown-rot fungus Gloeophyllum trabeum (FPRL 108 N) and the white-rot fungus Coriolus versicolor (CTB 863 A) was assessed in liquid culture under different conditions and in the presence of the fungicide cyproconazole. The production of biomass in G. trabeum was significantly influenced by the carbon source, monosaccharides stimulating increased biomass compared with oligosaccharides and polyols. The nitrogen source also significantly affected biomass production, with arginine and L-glutamic acid supporting maximum biomass. The best temperature for growth was 30°C, lower temperature causing a significant reduction in biomass production. The pH optimum for maximum growth was found to be 4.0. ECM production was influenced significantly by the nitrogen source, as well as by the pH of the medium and the temperature of incubation. The greatest proportion of ECM in the total biomass was produced by cultures incubated at 10°C (27% of the total biomass) and at pH 5.0 (16% of the total biomass). The same factors that affected the production of biomass and ECM in G. trabeum, also significantly affected C. versicolor. Again, simple monosaccharides supported the best growth. Amongst the nitrogen sources tested, L-glutamic acid stimulated maximum biomass production (double that of any other nitrogen source tested) whereas the greatest proportion of ECM in the total biomass was produced with arginine and isoleucine as nitrogen sources. The optimal temperature for growth was 22° C, whilst the optimum pH was 5.0. At 10°C the greatest proportion of ECM was produced, which represented about 24% of the total biomass. In terms of pH effects, the greatest proportion of ECM was produced at pH 6.0. The introduction of cyproconazole significantly reduced the amount of biomass produced by both organisms as expected. However, the production of ECM in both species was also affected greatly by the presence of biocide, with the proportion of ECM in the total biomass increasing significantly as the concentration of cyproconazole was raised. The results are discussed with regard to the possible role(s) of ECM in the decay process and its interaction with a specific organic preservative.
D Vesentini, D J Dickinson, R J Murphy

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