Basidiospores from Wood-Decay Fungi Transform Laccase Substrates in the Absence of Glucose and Nitrogen Supplements.

Gerhard Gramss,Klaus-Dieter Voigt

doi:10.3390/jof6020062

Gerhard Gramss, Klaus-Dieter Voigt

Open Access

https://doi.org/10.3390/jof6020062

Copy DOI

Abstract

Preparations of bacterial endospores and fungal conidia are applied in biocontrols, biocatalyses, and lignocellulose fermentations. The biocatalytic abilities of basidiospores from mushrooms of the order Agaricales are unknown. To assess their potential in colonizing recalcitrant substrates solely with their inherent resources, spores of the white-rot fungi Stropharia rugoso-annulata (Stru) and Kuehneromyces mutabilis (Kmt, Strophariaceae) were analyzed for surface-bound and internal total carbohydrates, phenols, proteins, minerals, and oxidoreductases to estimate their chemistry and the preconditions to transform the laccase substrates guaiacol and 2,2′-azinobis-(3-ethylbenzthiazoline-6-sulfonate) (ABTS) independent of external glucose and nitrogen. Surfaces of Stru/Kmt spores released (mg kg−1) hexoses, 7300/9700; phenols, >62/220; proteins, 21/168; and laccases, 42/0–0.15 µmol ABTS•+ kg−1 min−1 that mimicked oxidative activities of the resting spores. Milled-spore extracts contained pentoses, 96,600/6750; hexoses, 160,000/15,130; phenols, 452/767; protein, 12,600/924; true laccase, 688/0.30; and enzyme-protein-activating transition metals such as Cu in concentrations typical of wheat grains. Independent of external N and C supply, spores (<1‰) germinated in bideionized water, supported by their surface resources. Kmt spores germinated, too, at comparable rates in N-free solutions of glucose and the not immediately metabolizable ABTS and guaiacol. The release of proteins and oxidoreductase(s) by Kmt spores starting upon germination was higher in guaiacol-incubated idiophase- than in glucose-incubated trophophase-spores and led to the 3–4-fold formation of guaiacol polymerizates and ABTS•+. Constitutive aromatic ring-cleaving dioxygenases in the dormant spore that could be involved in the intrinsic metabolization of guaiacol were not detected. It is concluded that intrinsic resources enable (germinating) spores to release the highly efficient laccases of basidiomycetes and to transform aromatic compounds in the absence of sugar amendments. Spores show therefore plant seed-like autonomy in nutrient modification and acquisition during the early stages of the colonization of inert substrates.

Highlights

Commercial preparations of bacterial endospores, of conidia and spores from ascomycete fungi and yeasts, and of conidia from the basidiomycete Peniophora gigantea are applied in the biocontrol of fungal and insect pests of crop plants [1,2,3] and in the control of weeds [4], the butt rot of conifers [5], and populations of mosquitos [6,7,8]
The release of proteins and oxidoreductase(s) by K. mutabilis (Kmt) spores starting upon germination was higher in guaiacol-incubated idiophase- than in glucose-incubated trophophase-spores and led to the 3–4-fold formation of guaiacol polymerizates and ABTS+
Sporulating basidiomes basidiomesofofS.S.rugoso-annulata rugoso-annulata (Stru) growing on composted wood the were in spring and falland of K. mutabilis (Kmt) were provided by perennial field collected were collected in spring fallBasidiomes

Summary

Introduction

Commercial preparations of bacterial endospores, of conidia and spores from ascomycete fungi and yeasts, and of conidia from the basidiomycete Peniophora gigantea (all referred to as spores) are applied in the biocontrol of fungal and insect pests of crop plants [1,2,3] and in the control of weeds [4], the butt rot of conifers [5], and populations of (malaria) mosquitos [6,7,8]. Spore preparations of vesicular-arbuscular (VA) mycorrhizal fungi, Rhizobium, and Azotobacter spp. promote root and shoot growth in certain plant species [9,10]. No comparable niches have been occupied by basidiospores derived from fruitbodies of homobasidiomycetes whose basic chemistry, energy resources, and biocatalytic activities are largely unknown. Their resulting degree of nutritional autonomy or dependence on external nutrients upon the colonization of recalcitrant substrates attracted no attention

Methods

Results

Discussion

Conclusion