Effect of phenolic compounds on cellulose degradation by some white rot basidiomycetes

Abstract Cellulose degradation by several white rot fungi was investigated. In most fungi cellulase production was stimulated by lignin-related phenolics. Detailed investigation of Tremetes versicolor showed that this stimulation was not directly effected by phenols but was due to an indirect induction. The phenol was oxidized by laccase to quinone. The quinone was then reduced by the enzyme cellobiose: quinone-oxidoreductase while cellobiono-lactone was formed from cellobiose. The cellobiono-lactone was responsible for the increased cellulase production in submerged cultures with cellulose as the sole carbon source.     

Extracellular secretion of phenolic substances from living brown algae

The chemical structures of ultraviolet (UV)- absorbing substances secreted from the healthy living brown algae, Eisenia bicyclis and Ecklonia kurome, were demonstrated. The living activity of algal cells was critically examined using a confocal laser-scanning microscope after incorporation of fluorescein diacetate (FDA) into the cells. Using thin-layer chromatography (TLC), reversed-phase three-dimensional high-performance liquid chromatography (RP-3D-HPLC) and gas chromatography-mass spectrometry (GC-MS), it was found that the UV-absorbing substances (λ_max 265–270 nm) secreted from the living brown algae mainly consisted of the three monomeric bromophenols, 2,4-dibromophenol, 2,4,6-tribromophenol and dibromo-iodophenol, but not phloroglucinol or phlorotannins. The other minor compounds detected in the secretions were as follows: benzothiazole, fatty acids (14:1, 16:0 and 18:0 acids), franesol, 3-hydroxy-2,4,4-trimethylpentyl 2-methylpropanoate and squalene. Exudation of phloroglucinol and phlorotannins was ascertained to take place only after the cell death of these algae. These results indicate that, whilst the algae are alive, polymeric phlorotannins are strictly kept within the algal body, and only monomeric bromophenols are secreted into the seawater medium.     

Interaction between phenolic substances and microbial polysaccharides in soil aggregation

Summary The stability of synthetic soil aggregates containing the extracellular polysaccharide fromLipomyces starkeyi is increased and is more persistant when aggregates are infiltrated with either tannic acid or the products from decomposing herbage. Mixing tannic acid with polysaccharide during the preparation of aggregates had no effect. In a field experiment, addition of glucose produced a rapid improvement in soil aggregation which was considered to be due to the formation of microbial polysaccharides. The effect, however, had virtually disappeared after six months. By contrast glucose-treated plots receiving tannic acid 28 and 42 days after the glucose had been applied showed no sign of diminished aggregation at the end of the experiment.     

Ocean acidification and the loss of phenolic substances in marine plants

Rising atmospheric CO(2) often triggers the production of plant phenolics, including many that serve as herbivore deterrents, digestion reducers, antimicrobials, or ultraviolet sunscreens. Such responses are predicted by popular models of plant defense, especially resource availability models which link carbon availability to phenolic biosynthesis. CO(2) availability is also increasing in the oceans, where anthropogenic emissions cause ocean acidification, decreasing seawater pH and shifting the carbonate system towards further CO(2) enrichment. Such conditions tend to increase seagrass productivity but may also increase rates of grazing on these marine plants. Here we show that high CO(2) / low pH conditions of OA decrease, rather than increase, concentrations of phenolic protective substances in seagrasses and eurysaline marine plants. We observed a loss of simple and polymeric phenolics in the seagrass Cymodocea nodosa near a volcanic CO(2) vent on the Island of Vulcano, Italy, where pH values decreased from 8.1 to 7.3 and pCO(2) concentrations increased ten-fold. We observed similar responses in two estuarine species, Ruppia maritima and Potamogeton perfoliatus, in in situ Free-Ocean-Carbon-Enrichment experiments conducted in tributaries of the Chesapeake Bay, USA. These responses are strikingly different than those exhibited by terrestrial plants. The loss of phenolic substances may explain the higher-than-usual rates of grazing observed near undersea CO(2) vents and suggests that ocean acidification may alter coastal carbon fluxes by affecting rates of decomposition, grazing, and disease. Our observations temper recent predictions that seagrasses would necessarily be "winners" in a high CO(2) world.     

Increased enzymatic activities and levels of superoxide anion and phenolic compounds in cultures of basidiomycetes after temperature stress

Selected strains of basidiomycetes (Abortiporus biennis, Trametes versicolor and Cerrena unicolor) were shown to produce enhanced extracellular peroxidase (EP), superoxide dismutase (SOD) and laccase activities following the exposure of 10-day-old fungal cultures to separate high and low temperature stress. The stressful conditions also caused an increase in the concentrations of phenol compounds and superoxide anion radicals in these cultures. At first, peroxidase activity was observed at 12 hours from the moment of temperature stress application. Laccase activity appeared at 96 hours after the maximum levels of superoxide anion radicals (48 h) and SOD activity (36–72 h). The concentration of phenolic substances grew steadily during the period of cultivation. These relations between laccase, SOD and EP as well as superoxide radicals and phenol levels in the environment of ligninolytic fungi seems to be important in the course of the biosynthesis or biodegradation of lignin, as the consequence of adaptation of these basidiomycetes to environmental temperature conditions.     

Content of auxin-inhibitor-and gibberellin-like substances in humic acids

The content of auxin-, inhibitors-and gibberellin-like substances in freeze-dried humic acids was studied. The results indicate the existence of growth-promoting substances in humic acids, possibly corresponding to IAA or its precursors. Inhibitory activity is more marked during germination than during the growth process. The inhibitory effect caused by high concentration of humic acids could be due to an auxin-like action rather than an input per se of growth inhibitors. A significant amount of both free and conjugated gibberellin-like substances were observed.     

Enzymatic activity in basidiomycetes

The oxidation-reduction activity of the basidiomyceteOudemansiella mucida was studied in relation to its growth in a laboratory fermentor. Cytochromes were detected in the mycelium destroyed by sonication, flavin diaphorase, polyphenoloxidase, peroxidase and catalase were found to be present in the mycelial homogenate from Waring-blendor. The obtained values of the enzymatic activity were dependent on the method of preparation of the mycelium. Homogenization in a Waring-blendor was the most appropriate. Certain interrelationships between the appearance and activity of the enzymes followed and the phase of submerged growth of the fungus were shown. The results document the succession of cytochromes, flavins and polyphenoloxidase and the specific time differences of the activity of catalase and that of peroxidase.     

Role of aliphatic and phenolic hydroxyl groups in uranyl complexation by humic substances

Relativistic density functional calculations of uranyl complexes with alcohols were carried out to study how phenolic and aliphatic hydroxyl groups of humic substances may contribute to uranyl complexation by humic substances. According to recent experimental work, blocking of phenolic OH groups decreases the loading capacity, but has no effect on the key geometric parameters of uranyl humate complexes. This can be understood on the basis of our calculations which showed uranium-oxygen distances to be very similar for complexes with rather different types of O-donor ligands, with average U-O_eq ∼ 237 pm for fivefold coordinated uranyl (VI) complexes, both for O⁻ and OH functional groups. Uranyl complexation by alcohol moieties seems unlikely at environmental conditions as a high pH is required for the deprotonation of these groups; we confirm an alternative complexation mechanism that overcomes the ligand deprotonation problem. Similarities in structures and energetic suggest that complexes of both aliphatic and phenolic alcoholates may well contribute in comparable fashion to the complexation of uranyl by humic acids.     

Sexual selection in mushroom-forming basidiomycetes

We expect that sexual selection may play an important role in the evolution of mushroom-forming basidiomycete fungi. Although these fungi do not have separate sexes, they do play female and male roles: the acceptance and the donation of a nucleus, respectively. The primary mycelium (monokaryon) of basidiomycete fungi, growing from a germinating sexual spore, is hermaphroditic, but it loses female function upon the acceptance of a second nucleus. The resulting dikaryon with two different nuclei in each cell retains a male potential as both nuclei can fertilize receptive mycelia. We tested the occurrence of sexual selection in the model species of mushroom-forming basidiomycetes, Schizophyllum commune, by pairing monokaryons with fully compatible dikaryons. In most pairings, we found a strong bias for one of the two nuclei although both were compatible with the monokaryon when paired alone. This shows that sexual selection can occur in mushroom-forming basidiomycetes. Since the winning nucleus of a dikaryon occasionally varied depending on the receiving monokaryon, we infer that sexual selection can operate through choosiness of the receiving individual (analogous to female choice). However, in other cases the same nucleus won, irrespective of the receiving monokaryon, suggesting that competition between the two nuclei of the donating mycelium (analogous to male–male competition) might also play a role.     

Peroxidase activity in brown-rot basidiomycetes

Summary Basidiomycetes which cause brown-rot of wood possess intracellular but little or no extracellular peroxidase activity. These fungi had been reported not to produce peroxidase.     

Polysaccharides of xylotrophic basidiomycetes

Physicochemical properties, composition, and structure of the polysaccharides synthesized by the fungi Lentinus edodes, Ganoderma lucidum, and Crinipellis schevchenkovi in a submerged culture were studied. It has been demonstrated that the exo-and endopolysaccharides of submerged mycelia of the fungi studied are similar to the β-1,3-D-glucans of the fruiting bodies.     

Enzymatic activity of basidiomycetes

In mycelial acetone powder of the basidiomyceteOudemansiella mucida, the presence of enzymatic systems of NADH₂-oxidase and-dehydrogenase type and of NAD⁺-dependent alcoholdehydrogenase (using ethanol as substrate) has been detected. NADH₂-oxidase has its optimal pH value in the region of 6,0 and is not too active. NADH₂-dehydrogenase which reduces 2,6-dichlorophenolindophenol is very active, may be eluted from the mycelial preparation with water and its adequate pH is in the region of 6,2. On the other hand, NADH₂-dehydrogenase reducing triphenyltetrazolium chloride is non-eluable with water, its activity depends on the presence of menadione and its adequate pH lies in the region of 7,4.     

Antibiotics from basidiomycetes

Three new antibiotically active metabolites were isolated from cultures of the fungus Pleurotellus hypnophilus. The structures which are closely related to the coriolins were elucidated by spectroscopic methods. Hypnophilin (1) has a hirsutane sceleton whereas pleurotellol (2) and pleurotellic acid (3) are sesquiterpenoids with novel hirsutane skeletons. The common structural feature of all three metabolites is an -methylene ketone moiety. The antibiotics inhibited the growth of several bacteria as well as of some fungi. In cells of the ascitic form of Ehrlich carcinoma RNA and DNA syntheses were more affected than protein synthesis. The mode of action was compared with the antimicrobial and cytotoxic effects of complicatic acid (4) and other -methylene ketones and lactones from higher plants. All the compounds tested reacted rapidly with cysteine to form adducts which were almost devoid of biological activity.Abbreviations ECA-cells Ehrlich carcinoma ascitic cells - MIC Minimal inhibitory concentration - MNNG N-methyl-N-nitro-N-nitrosoguanidine Antibiotics from Basidiomycetes. XIII. T. Anke, W. H. Watson, B. M. Giannetti, and W. Steglich: The alliacols A and B from Marasmius alliaceus (Jacq. ex Fr.) Fr. J. Antibiotics, submitted     

Fruiting body production in basidiomycetes

Mushroom cultivation presents an economically important biotechnological industry that has markedly expanded all over the world in the past few decades. Mushrooms serve as delicacies for human consumption and as nutriceuticals, as “food that also cures”. Mushrooms, the fruiting bodies of basidiomycetous fungi, contain substances of various kinds that are highly valued as medicines, flavourings and perfumes. Nevertheless, the biological potential of mushrooms is probably far from exploited. A major problem up to now is that only a few species can be induced to fruit in culture. Our current knowledge on the biological processes of fruiting body initiation and development is limited and arises mostly from studies of selected model organisms that are accessible to molecular genetics. A better understanding of the developmental processes underlying fruiting in these model organisms is expected to help mushroom cultivation of other basidiomycetes in the future. Received: 17 January 2000 / Received revision: 7 March 2000 / Accepted: 3 April 2000     

Function of phenolic substances in the degradation system of indole-3-acetic acid in strawberries

The homogenate of different strawberry organs inhibits the degradation of IAA in the presence of horse radish peroxidase, while intact strawberry tissues are able to degrade IAA. The chemical nature of peroxidase inhibitors present, in strawberry tissues was in vestigated. Using paper chromatography the following polyphenolic substances inhibiting peroxidase activity were identified: chlorogenic, caffeic, ellagic, gentisic, gallic, and vanillic acids, quercetin and pelarginidin. Monophenolic compounds, also present in strawberry, such as p-hydroxy-phenyloacetic acid and p-hydroxybenzoic acid, are strong stimulators of IAA oxidase. Abscisic acid in very high concentration (1×10^?4M) enhances degradation of IAA by peroxidase. When both poly-and monophenolic compounds at equimolar concentrations are present in the system, only the inhibition of IAA degradation occurs. Tissue explants from the strawberry leaves and petiole degrade less IAA if they are previously forced to synthetize more polyphenols under illumination. Although the difference in IAA-decarboxylation activity between the illumination and dark treated explants was relatively small, nevertheless it was consistent and appears to be very important from a physiological point of view suggesting that there exists a regulatory relationin vivo between IAA degradation and the presence of phenolsin plant tissue. Electron microscope data revealed that phenolic substances are specially isolated from cytoplasm of the receptacle cells.