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A new concept of oxalic acid biosynthesis in physiology of copper-tolerant brown-rot fungi
2001 - IRG/WP 01-10394
Recently, a wide variety of roles of oxalic acid (oxalate) in wood decay systems have been receiving much attention. Copper tolerance of wood-rotting basidiomycetes has been believed to be due to the detoxification of copper wood preservatives by oxalate produced by these fungi. However, biochemical mechanism of oxalate biosynthesis in relation to physiology of wood-rotting fungi has not been elucidated although two oxalate-forming enzymes, oxaloacetase and glyoxylate dehydrogenase, have been studied in our laboratory. Recently, a new role of glyoxylate cycle in oxalate biosynthesis in wood- rotting fungi has been presented, and the cycle commonly occurred to varying extents among the fungi although they were grown on glucose. Enzymatic analyses showed that isocitrate was cleaved by isocitrate lyase in the glyoxylate cycle rather than oxidized by isocitrate dehydrogenase in tricarboxylic acid (TCA) cycle, and the fungi were found to lack a normal TCA cycle due to the absence of - ketoglutarate dehydrogenase. It is noteworthy that glucose was efficiently converted to oxalate in a theoretical yield of about 80%, accumulating in the culture media of F. palustris. The results further indicate that acetyl-CoA derived from glucose was not completely oxidized to CO2 in TCA cycle but was mainly converted to oxalate with help of the other coupling metabolic cycles, including glyoxylate cycle. Formation of oxalate from several intermediary metabolites using cell-free extracts of F. palustris confirmed that oxalate is also the final product of the metabolic pathway in the in vitro system. Thus, it is proposed as a new concept that most of copper-tolerant brown-rot fungi may acquire the energy by oxidizing glucose to oxalate, i.e. oxalate fermentation expressed in the following equation; Glucose + 5O2 --> 2 Oxalate + 2CO2 + 4H2O.
E Munir, T Hattori, M Shimada

Spatial arrangement of lignin peroxidase in pine decayed by Phanerochaete chrysosporium and Fomitopsis pinicola
1988 - IRG/WP 1343
By applying immunoelectronmicroscopic methods, lignin peroxidase of the white rot fungus Phanerochaete chrysosporium has been localized in the cytoplasm of hyphae, close to the plasmalemma and on the plasmalemma. Infiltration of wood specimen with culture filtrates, concentrated 300-fold, gave clear information on the penetration of the enzyme into the wood cell wall. Penetration was restricted to superficial areas. No diffusion of enzymes into the cell wall took place in white rot. Likewise, infiltration of wood. degraded by the brown rot fungus Fomitopsis pinicola, did not indicate free diffusion of the enzyme within the cell wall. This was taken as a proof of non-ezymatic cell wall degradation in brown rot.
E Srebotnik, K Messner

The preliminary characterization of ß-1,4-xylanase of the brown-rot fungus Gloeophyllum trabeum
1990 - IRG/WP 1447
The extracellular ß-1,4-xylanase of the brown-rot fungus, Gloeophyllum trabeum, was isolated from crude extract by chromatofocusing method (PBE 94 column chromatography). The isoelectric point was estimated to 4.2-4.8 by cromatofocusing and 4.5 by isoelectric focusing (IEF). The molecular weight of the enzyme was estimated to 37,000 dalton by SDS-PAGE. The optimal temperature for the crude extract xylanase was +70°C. The enzyme stability, after 1 h incubation, decreased sharply above +60°C and pH 6.
A-C Ritschkoff, M Rättö, L Viikari

Suppression of aerial hypha formation by spent culture filtrate of a non-degradative strain of Postia placenta
1991 - IRG/WP 1498
ME20, a wild-type monokaryotic strain of the brown-rot fungus Postia placenta, does not cause significant weight losses in standard soil-wood block decay tests and fails to form aerial hyphae in liquid and agar culture. This abnormal morphological feature may be caused by the same aberrant physiology that prevents the strain from degrading wood efficiently. ME20 releases elevated levels of the autolytic enzymes laminarinase and protease into culture media. These autolytic enzymes may degrade the cell wall and hyphal sheath, thus preventing aerial hypha formation and limiting wood colonization. If abnormally high levels of autolytic enzymes suppress aerial hypha formation, any strain of Postia placenta grown in their presence should take on the appearance of ME20. MAD698, a standard floccose test strain of Postia placenta, was grown in fresh media containing increasing concentrations of filter-sterilized spent culture filtrate of ME20. Aerial hypha formation was strongly inhibited or prevented when the spent culture filtrate made up 40% or more of the medium. Spent media from MAD698 caused a similar effect but only at higher concentrations (80 and 100%). The suppression does not appear to be caused by extracellular autolytic enzymes since commercial preparations of laminarinase, chitinase, and protease did not reproduce this effect. The suppressive agent appeared in ME20 culture filtrate after only two weeks of growth. It has a molecular weight of less than 10,000 and is resistant to boiling. Additional research is needed to characterize ist nature, thus identifying a potential biorational inhibitor of wood-decay fungi.
J A Micales

Evaluation of New Zealand staining fungi for degradation of radiata pine
1999 - IRG/WP 99-10310
This investigation sought to determine the potential of selected NZ staining fungi to induce weight loss and changes in toughness (impact bending strength) and composition in unseasoned radiata pine sapwood. Furthermore, assays were performed to eveluate enzyme production by staining fungi. Sets of side-matched specimens were inoculated with Ophiostoma floccosum, Sphaeropsis sapinea and O. pluriannulatum prior to 8 and 16 weeks incubation, along with non-inoculated control samples. After incubation, samples were equilibrated to 14% wood moisture content before determining toughness and weight loss.Neither nor dry weight were significantly different (p <0.05) between inoculated samples and controls, irrespective of sapstain fungi used. Quantitative chemical analysis showed that there was no significant difference between the lignin and carbohydrate composition of inoculated samples and controls. Enzyme assays demonstrated that all staining fungi tested produced xylanase, but carboxymethylcellulase was not detected. Xylanase values range between 0.07 µ moles/min/ml and 0.66 µ moles/min/ml depending on the fungus tested. Thus we conclude that the New Zealand staining fungi under test, though they produce a slight amount of an hemicellulolytic enzyme, do not degrade radiata pine.
A Schirp, R L Farrell, B Kreber

Effect of light and ventilation condition on the rate of wood decay by the brown rot basidiomycete, Tyromyces palustris
1991 - IRG/WP 1517
Effect of light and the ventilation conditions of incubation jars on the wood decay by Tyromyces palustris (Berk. et Curt.) Murr. FFPRI 0507 was investigated. Under no irradiation of light, the ventilation conditions gave extensive effect on mass loss of the test pieces when the culturing was performed with culture medium designated in Japanese Industrial Standard (JIS) A 9302 (Medium A; glucose 4.0%, malt extract 1.5%, peptone 0.3%). On the other hand, no such kind of effect for ventilation conditions was recognized under light conditions, and the wood decay by the fungus accelerated by additional light irradiation of a considerably small intensity. Next, we investigated the relationship between light and the culture medium composition during the wood decay by the fungus. It was found that almost equivalent mass loss occurred after 60-90 days of cultures when the culturings were performed under light-shield conditions with medium A, the culture medium designated in Japan Wood Preserving Association (JWPA) standard No.1 (medium B; malt extract 2.0%, peptone 1.0%), and another culture medium diluted medium B by two times (medium C). Under the irradiation of light, the mass loss on the cultures in medium B and C was markedly less than that in the same media under no irradiation conditions. These results suggested that effect of light on the wood decay by Tyromyces palustris depended on the concentration of glucose in the culture medium. Further, we also investigated the activities of several extracellular and cell wall bound enzymes in wood meal medium contained medium A. From our experimental results, the activities of cellulase (b-1,4-glucan 4-glucanohydrolase, E.C. and mannanase (b-1,4-mannan mannanohydrolase) depended on light irradiation during the wood decay and these enzyme activities may give extensive effect on the mass loss by Tyromyces palustris.
T Suzuki, M Higaki

Preliminary studies on cellulase production by selected Basidiomycetes and the effect of copper-chrome-arsenate on these enzymes
1980 - IRG/WP 1122
The growth of wood-destroying fungi on ligno-cellulosic materials depends on the production of many enzymes, of which probably the most important is the multi component cellulase system. Within this system, at least three different kinds of enzym are believed to be involved in crystalline cellulose decomposition. These are endo-1,4-glucanase, exo-1,4-ß glucanase and ß-glucosidase. Most of the recent research on cellulases has concerned isolation, purification and characterisation of the enzymes and their application in the utilisation of cellulosic waste. Information on the chemical inhibition of cellulases is available but there is little reference to the interaction of wood-attacking cellulases and the preservatives which are used to protect wood. The objective of this work is to study the production and activity of cellulases of selected basidiomycetes and to observe the effect of wood-preservatives on these enzymes. Preliminary studies with copper-chrome-arsenate (CCA) are reported here
O Collett

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

Molecular analysis of the basidiomycete Coniophora puteana
1992 - IRG/WP 92-1534
Sodium dodecylsulphate polyacrylamide gel electrophoresis and Western Blotting, using a polyclonal antiserum produced against a whole cell extract of Coniophora puteana, were used to analyse the major proteins and antigens of the wet rot organism Coniophora puteana. The macromolecule profiles of this organism were different from other members of the Coniophora genus and from a set of unrelated organisms. However the profiles for Coniophora marmorata and Coniophora arida were more like that of Coniophora puteana than other organisms analysed. Analysis, by SDS-PAGE of exoproteins indicated differences between members of the Coniophora genus but, whilst there were some intra-species differences overall profiles were similar for all isolates of Coniophora puteana tested. Some cross reactivity of the Coniophora antiserum was noted, both in Western Blotting and in enzyme immunoassay and whilst the antiserum was produced against liquid culture grown organism it was able to detect Coniophora puteana when extracted from infected wood blocks. Furthermore, unlike some other basidiomycetes analysed serum components did not bind nonspecifically to Coniophora puteana.
H E McDowell, D Button, J W Palfreyman

Fenton's reagent as a modification tool in brown-rot decay
1996 - IRG/WP 96-10155
A biomimetic approach was used to clarify the role and importance of the Fenton-type reaction in the carbohydrate degradation by brown-rot fungi. Spruce sawdust and microcrystalline cellulose were modified in the H2O2/Fe(II) treatment. The degree of hydrolysis of the pretreated spruce sawdust was clearly increased with the complete cellulase (Econase), purified endoglucanase from Trichoderma reesei and endoglucanase of Poria placenta. The oxidative pretreatment of microcrystalline cellulose decreased the hydrolyzability of pure cellulose with the complete cellulase, but the hydrolyzability with both purified endoglucanase of Trichoderma reesei and endoglucanase from Poria placenta was increased. Thus, after oxidative treatment with Fenton&apos;s reagent the hydrolysis of both pure cellulose and wood was substantially increased.
M Rättö, A-C Ritschkoff, J Buchert, L Viikari

The probable mechanism of action of boric acid and borates as wood preservatives
1990 - IRG/WP 1450
The tetrahydroxyborate ion [B(OH)4-] acts by complexation with poly-ols and probably attacks decay fungi through extracellular substrate sequestration; intracellular substrate sequestration; enzyme inhibition; and change in membrane function. Work was carried out to investigate this further and to try to explain certain phenomena observed in the area of boron preservation. The effect of Na borate in the presence of different concentrations or various carbohydrates upon the radial growth rate of certain fungi was investigated; along with parallel experiments on the activity of 6-phosphogluconate dehydrogenase as an example of a borate inhibited enzyme system. It was found that upon the addition of certain poly-ols, the inhibitory effect of borate on both fungal growth and enzyme activity could be reduced. These results have been used in the development of our understanding of the mechanism of action of borates as wood preservatives. The commonly held belief that certain mould species are resistant to borates may also need re-evaluation.
J D Lloyd, D J Dickinson, R J Murphy

Biochemical relationships between biodegradation of cellulose and formation of oxalic acid in brown-rot wood decay
1991 - IRG/WP 1472
Non-enzymic hydrolysis of cellulose with low concentrations of oxalic acid was examined. The incubation of pine wood pulp with 1% oxalic acid (pH 1.3) at 35°C for 4 weeks reduced the original viscosity to 60%. Reducing sugars were liberated from various cellulosic samples by the oxalic acid treatment. However, crystallinities of cellulose in those samples did not change before and after the treatments. Then, the enzymatic formation of oxalic acid was investigated in relation to cellulose biodegradation by brown-rot fungi. We succeeded in isolating oxaloacetase from the brown-rot fungus Tyromyces palustris in cell-free extracts which catalyze hydrolysis of oxaloacetate to produce oxalate and acetate. During the brown-rot wood decay process, oxaloacetase may play an important role in degradation of wood carbohydrate.
M Shimada, Y Akamatsu, A Ohta, M Takahashi

Wharf-borer a threat to stored archaeological timbers
1992 - IRG/WP 92-1560
Increased interest in marine archaeology has occured in recent years. Stored waterlogged archaeological timbers have been shown to be degraded by physical and microbial agents. In recent years a new threat has been highlighted, namely the wharf-borer Nacerdes melanura (L.). The objective of this paper is to outline studies of the morphology, biology, life-history and carbohydrate digestion by this beetle. These studies will allow improved preventative measures to be employed by conservators and archaeologists in the passive holding of archaeological timbers.
A J Pitman, E B G Jones, A M Jones, M Rule

Secretion of ligninolytic enzymes by hyphal autolysis of the white rot fungus Phanerochaete chrysosporium
1991 - IRG/WP 1480
The secretion of ligninases by Phanerochaete chrysosporium was investigated with polyclonal antibodies, followed by immmunogold-silver staining and light microscopy. After growing fungal mycelium on nitrocellulose, extracellular ligninases were detected around old, plasmaless hyphae, but not at arthrospores, chlamydospores, or blastoconidia. Labeling of fungal hyphae on coverslip cultures was observe only when the cell wall was highly porous and translocation of cell material occurred. These experiments suggested that ther is a correlation between hyphal lysis and the release of extracellular ligninases from hyphae.
R Lackner, E Srebotnik, K Messner

Old and new facts on the dry rot fungus Serpula lacrymans
1991 - IRG/WP 1470
The article collates some of the recent literature on the biology of the dry rot fungus Serpula lacrymans. The fungus can grow at 28°C, and maximum wood moisture is above 55%. Serpula Iacrymans degrades crystalline cellulose. The intensive production of extracellular oxalic acid is neutralized by calcium and iron. There is considerable variation among the strains with regard to factors such as growth rate, wood decay and response to preservatives. Possible alternative methods of eradication involve interference with the metabolism of nitrogen and sugars. Gel electrophoresis of mycelial proteins and immunological procedures provide valuable supplementary means of identification. Fruit-bodies can be obtained regularly in artificial culture. Inter-stock breeding of monokaryons to dikaryons up to the third generation shows differences among cultures with regard to growth, reaction to temperature, rate of wood decay and resistance to chemicals
O Schmidt, U Moreth-Kebernik

Breakdown of cellulose derivatives by cellulolytic enzymes. I. Action of fungal ß-glucosidases toward substituted PNP ß-D-glucopyranosides
1998 - IRG/WP 98-10281
The action of fungal ß-glucosidases on the methyl derivatives of p-nitrophenyl (PNP) ß-D-glucopyranoside, which were regioselectively substituted at 0-2, 0-3, 0-4 and 0-6 positions was studied. Several ß-glucosidases from brown-rot, white-rot, and soft-rot fungi and almond were used for the study. These ß-glucosidases did not act on the 2, 3, and 4-0-methyl derivatives, while the 6-0-methyl one was hydrolyzed by all the enzymes to some extent. The results indicate that the methyl group at 0-2, 0-3, 0-4 of the glucopyranoside strongly inhibits the recognition by the ß-glucosidases, while the enzymes do not discriminate the structure difference between PNP ß-glucopyranoside and its methyl derivative at 0-6.
T Nishimura, I Momohara, M Ishihara

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

The nature of osmiophilic particles and their distribution during different stages of brown and white rot decay
1983 - IRG/WP 1213
The distribution of osmiophilic particles during the course of brown and white rot decay was investigated by applying transmission electron microscopic (TEM) methods. It was found that it correlates with the brown and white rot pattern.The osmiophilic particles are produced by the fungus and are supposed to be wood rotting enzymes.
K Messner, H Stachelberger

Wood structure in relation to excessive absorption - a literature survey
1971 - IRG/WP 300
This literature study, composed in connection with &apos;the structure of wood in relation to the excessive absorption&apos;, started from the idea that the subject only could be dealt with successfully if the structure was taken into account in relation to a normal absorption pattern in so far as this knowledge can enlighten the understanding of the abnormal situation. The normal penetration pattern is dealt with in comparison of increasing absorption caused by using several different methods with the drying technique and especially caused by micro-organisms. It transpired that bacteria especially play an important role in excessive absorption. They degrade the wood tissue to such an extent that openings develop which can easily be passed unhindered
S M Jutte

Comparison of the inhibitory effects of borate, germanate, tellurate, arsenite and arsenate on 6-phosphogluconate dehydrogenase
1991 - IRG/WP 1508
Sodium borate inhibits the enzymatic activity of many dehydrogenases, and it is thought that this is due to the complexation of the borate anion with the coenzyme nucleotide. It has been suggested in the past that complexation of this type, leading to enzyme inhibition and other biological effects, is responsible for the inhibition of fungal growth and consequently the protection of boron treated timber. Other ions that have the ability to complex with polyols were investigated for possible dehydrogenase inhibition using 6-phosphogluconate dehydrogenase. Inhibition was found to be caused by compounds of germanium, tellurium and arsenic. The results have been used to further develop our understanding of the mechanisms of action of borates as wood preservatives, and may have important implications.
J D Lloyd, D J Dickinson

A biochemical explanation for the observed patterns of fungal decay in timber
1980 - IRG/WP 1111
Experiments designed to compare the degree of localization of the cellulase enzymes of some white, brown and soft rot organisms are described. The site and nature of binding of the enzymes is discussed. The technique is ellution of mycelium grown in liquid culture with a variety: of agents including acetate buffer, carboxymethyl cellulose solution, borate/glycerol buffer and urea. The mycelium was assayed for cellulase activity before and after washing. Eluted protein was also assayed. The effect on retention of cellulases of treatment with a (1,3) ß glucanase was determined. Brown rot organisms showed a far lower retention of cellulases to the mycelium than the soft and white rot organismns. Carboxymethylcellulose solution was found to be only slightly effective as a protein eluent on the white and soft rot organisms indicating low substrate affinity. 8 M urea was found to be an effective protein eluting agent - possibly implying hydrogen bonding between cellulases and the fungus. Borate/glycerol buffer was also shown to be an effective agent for protein elution - however· less so than urea. This agent probably binds to carbohydrates, either glycoprotein enzymes or binding sites on the organism, thius displacing protein. (1,3) ß glucanase markedly decreased the retention of cellulase activity in soft and white rot organisms indicating binding to a (1,3) ß glucan. It is postulated that cellulase retention mechanisms found in soft and white rot organisms and absent from brown rots have a significant role in the production of the characteristic observed patterns of decay of the three types.
N B Green, D J Dickinson, J F Levy

Production, function and neutralization of oxalic acid produced by the dry rot fungus and other brown rot fungi
1987 - IRG/WP 1330
The formation of oxalic acid by the wood-destroying fungi causing brown rot, is found to be the key which by hydrolysing the hemicellulose brings the cellulose in the tracheid wall in contact with the cellulase enzymes and yeld watersoluble sugars leaving only a lignin skeleton. To control the pH in the substrate the excess oxalic acid is precipitated to water insoluble calcium oxalate by the dry rot fungus in contact with a calcium source. As source glass can be used, however, mortar, concrete or clay soil is better. Heavy metals that form complex compounds with oxalic acid can substitute calcium certain to a degree. The wet rot fungus Coniophora putenea is not dependent on calcium like the dry rot fungus. By producing acetic as well as oxalic acid it might form a buffer solution which controls the pH in the substrate.
J Bech-Andersen

Enzyme immunoassay to detect Postia placenta in field tests: Comparison of plate ELISA with hydrophobic cloth and cotton dipstick
1991 - IRG/WP 2378
Standard indirect enzyme-linked immunosorbent assay in polystyrene 96-well plates was compared to hydrophobic polyester cloth and cotton dipstick for detection of wood-derived antigens from the brown-rot fungus Postia placenta. The ease of handling, larger surface area, and economics of the latter two adsorbents were surveyed for application as field tests for detection of early decay. At high antibody concentrations, the cloth ELISA (C-ELISA) exibited sensitivity comparable to the plate ELISA (P-ELISA), but at lower antibody concentrations signals diminished more rapidly for the C-ELISA. The dipstick assay lacked sensitivity even at high antibody concentrations, and suffered from inability to block a high nonspecific background. Nonporous polystyrene was judged superior to C-ELISA and cotton dipstick as the immobilizing phase for detecting antigen from Postia placenta by immunoassay, although at high antibody concentrations and increased incubation periods, C-ELISA matched the sensitivity of P-ELISA.
C A Clausen

Immuno-scanning electron microscopic localization of extracellular polysaccharidases within the fibrillar sheath of the brown rot fungus Postia placenta
1991 - IRG/WP 1497
Extracellular polysaccharidases of the brown-rot fungus Postia placenta were localized using colloidal gold labeled monoclonal antibodies to the B-1,4-xylanase (32-36kDa) fraction of Postia placenta. Postia placenta was grown from agar onto glass coverslips, immunolabeled with or without prior fixation, and examined by SEM. Enzymes were localized on the hyphal surface and on the clumped fibrillar elements (mycofibrils) of the hyphal sheath following fixation with enzymes. If fixation was omitted, labeling was diffuse and not localized on individual or clumped mycofibrils. We conclude that extracellular decay enzymes are weakly bound (non-covalently), but not identical to, the linear mycofibrillar elements of the hyphal sheath. Enzymes appear to dissociate into the water soluble glucan matrix of the sheath during incubation in physiological buffers when fixation is omitted.
F Green III, C A Clausen, M J Larsen, T L Highley

The effect of Tween 80 on the growth, morphology, and enzyme secretion of Postia placenta
1990 - IRG/WP 1456
The nonionic surfactant Tween 80 (polyethylene oxide sorbitan mono-oleate) has been reported to increase enzyme production and/or secretion in bacteria and fungi. Such a procedure could greatly facilitate research into the physiology of wood-decay fungi since quantities of available enzyme are often limiting. The brown-rot fungus Postia placenta was grown in a synthetic medium supplemented with 0, 0.01, 0.05, 0.1, 0.2, and 0.4% Tween 80. The addition of even the lowest percentage of Tween significantly increased mycelial dry weight and prevented the formation of aerial hyphae. With the exceptions of ß-D-glucosidase and ß-D-galactosidase, extracellular carbohydrate-degrading enzyme production did not change. Levels of xylanase, carboxymethylcellulase, laminarinase, and ß-D-galactosidase remained unaffected by the presence of Tween. Some factor other than secretion mechanisms, such as microelement or nitrogen availability, is probably limiting production of these enzymes.
J A Micales

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