Department of Microbiology, Faculty of Agriculture and Forestry, University of Helsinki, Helsinki, Finland.
Department of Microbiology, Faculty of Agriculture and Forestry, University of Helsinki, Helsinki, Finland
Appl Environ Microbiol. 2018 Apr 2;84(8). doi: 10.1128/AEM.02662-17. Print 2018 Apr 15.
Basidiomycota fungi in the order Polyporales are specified to decomposition of dead wood and woody debris and thereby are crucial players in the degradation of organic matter and cycling of carbon in the forest ecosystems. Polyporales wood-decaying species comprise both white rot and brown rot fungi, based on their mode of wood decay. While the white rot fungi are able to attack and decompose all the lignocellulose biopolymers, the brown rot species mainly cause the destruction of wood polysaccharides, with minor modification of the lignin units. The biochemical mechanism of brown rot decay of wood is still unclear and has been proposed to include a combination of nonenzymatic oxidation reactions and carbohydrate-active enzymes. Therefore, a linking approach is needed to dissect the fungal brown rot processes. We studied the brown rot Polyporales species by following mycelial growth and enzyme activity patterns and generating metabolites together with Fenton-promoting Fe-reducing activity for 3 months in submerged cultures supplemented with spruce wood. Enzyme activities to degrade hemicellulose, cellulose, proteins, and chitin were produced by three Finnish isolates of Substantial secretion of oxalic acid and a decrease in pH were notable. Aromatic compounds and metabolites were observed to accumulate in the fungal cultures, with some metabolites having Fe-reducing activity. Thus, demonstrates a pattern of strong mycelial growth leading to the active production of carbohydrate- and protein-active enzymes, together with the promotion of Fenton biochemistry. Our findings point to fungal species-level "fine-tuning" and variations in the biochemical reactions leading to the brown rot type of wood decay. is a common fungal species in boreal and temperate forests in the Northern Hemisphere encountered as a wood-colonizing saprotroph and tree pathogen, causing a severe brown rot type of wood degradation. However, its lignocellulose-decomposing mechanisms have remained undiscovered. Our approach was to explore both the enzymatic activities and nonenzymatic Fenton reaction-promoting activities (Fe reduction and metabolite production) by cultivating three isolates of in wood-supplemented cultures. Our findings on the simultaneous production of versatile enzyme activities, including those of endoglucanase, xylanase, β-glucosidase, chitinase, and acid peptidase, together with generation of low pH, accumulation of oxalic acid, and Fe-reducing metabolites, increase the variations of fungal brown rot decay mechanisms. Furthermore, these findings will aid us in revealing the wood decay proteomic, transcriptomic, and metabolic activities of this ecologically important forest fungal species.
担子菌门在多孔菌目中的真菌被指定为分解枯木和木质碎屑，因此它们是森林生态系统中有机质降解和碳循环的关键参与者。多孔菌目中的木质腐朽物种包括白腐菌和褐腐菌，这取决于它们的木质腐朽模式。虽然白腐菌能够攻击和分解所有木质纤维素生物聚合物，但褐腐菌主要导致木材多糖的破坏，而木质素单元的修饰较少。褐腐木材腐朽的生化机制尚不清楚，据推测包括非酶氧化反应和碳水化合物活性酶的组合。因此，需要一种连接方法来剖析真菌褐腐过程。我们通过跟踪菌丝生长和酶活性模式以及在补充云杉木材的浸没培养物中产生代谢物以及芬顿促进的铁还原活性，研究了褐腐多孔菌目物种。在 3 个月的时间里，来自芬兰的 3 个分离株产生了降解半纤维素、纤维素、蛋白质和几丁质的酶活性。大量分泌草酸并降低 pH 值是显著的。观察到芳香族化合物和代谢物在真菌培养物中积累，其中一些代谢物具有铁还原活性。因此，表明存在一种强烈的菌丝生长模式，导致碳水化合物和蛋白质活性酶的积极产生，以及芬顿生物化学的促进。我们的发现指向真菌种水平的“微调”和导致褐腐类型木材腐朽的生化反应变化。是北半球北方森林和温带森林中常见的真菌物种，作为一种木材定殖的腐生菌和树木病原体，它会导致严重的褐腐型木材降解。然而，其木质纤维素分解机制仍未被发现。我们的方法是通过在补充木材的培养物中培养 3 个 的分离株，探索其酶活性和非酶芬顿反应促进活性（铁还原和代谢物产生）。我们发现同时产生多种酶活性，包括内切葡聚糖酶、木聚糖酶、β-葡萄糖苷酶、几丁质酶和酸性肽酶，同时产生低 pH 值、积累草酸和具有铁还原代谢物，增加了真菌褐腐分解机制的变化。此外，这些发现将有助于我们揭示这种在生态上重要的森林真菌物种的木材腐朽蛋白质组学、转录组学和代谢活性。
