Perenniporia meridionalis Decock & Stalpers is a wood decay macrofungus which grows on hardwoods (seldom on conifers) in Central and Southern Europe, as far as Caucasus towards East. Since the species was quite recently taxonomically revised (1), only few isolates of this species are available and literature concerning biotechnological applications is almost absent. Mycological researchers of DSTA (University of Pavia) obtained its own isolate in 2010 by means of a sporoma collected in Italy, near Iseo Lake (BS), whose identity was checked by molecular analysis (2). Enzymes of wood decay fungi can be exploited as a tool to achieve biodegradation of lignocellulosic agricultural residues aimed at sustainable production of biofuels and chemicals (3). P. meridionalis was therefore tested for the ability of growing on stems of Medicago sativa L., one of the most important plants cultured in Northern Italy. Fungal mycelium grown in liquid cultures was inoculated onto previously triturated and sterilized dried stems in Petri dishes; sterile water was added to keep the fungus hydrated; growth at 37°C was subsequently observed week by week for a month. This temperature was chosen after a preliminary growth profile test on 2% Malt Extract Agar (MEA). Incubation at 37°C resulted in a wide colonized area: even though quantitative determination was not possible, mycelium in fact appeared homogeneously woolly and substratum completely embedded. Microscopy was performed both by: a) optical microscope 100x to 1000x (Zeiss Axioplan); b) SEM (Tescan FE-SEM, MIRA XMU series) which is equipped with EDAX spectrometer, at an accelerating voltage of 15-20 kVolt in high vacuum. Observations were only partially consistent with each other, since SEM allows a much finer discrimination between fungal structures and vegetal ones. Stem appeared deeply destructured by chemical (enzymatic) degradation particularly affecting the not-lignified component. Typical structures of wood decay fungi such as abundant arboriform skeleto-binding hyphae spread as a capillary net were observed. Skeins of hyphal projections with a wide diameter clearly engaged in stem penetration were found; such projections showed sharp distal ends, while proximal ones looked bell-shaped instead. The surface of both hyphal types was often sprinkled with scarce to abundant encrustations likely to be oxalate crystals. Even in substrata poor in minerals, fungi are well known to precipitate cations (and particularly Ca2+) for several alleged functions among which pathogenesis, pH regulation, removal or reservoir of metals (4). These preliminary results show that P. meridionalis displays remarkable versatility being able to efficiently colonize and degrade a substratum unusual for a lignicolous fungus. Quantification of the degree of biodegradation of plant cell wall polymers is in progress.

110° Congresso della Società Botanica Italiana - II Inter. Plant Science Conference (IPSC) - Pavia, 14 - 17 September 2015

GIROMETTA, CAROLINA ELENA;DONDI, DANIELE;MALAGODI, MARCO;NIELSEN, ERIK;SAVINO, ELENA
2015-01-01

Abstract

Perenniporia meridionalis Decock & Stalpers is a wood decay macrofungus which grows on hardwoods (seldom on conifers) in Central and Southern Europe, as far as Caucasus towards East. Since the species was quite recently taxonomically revised (1), only few isolates of this species are available and literature concerning biotechnological applications is almost absent. Mycological researchers of DSTA (University of Pavia) obtained its own isolate in 2010 by means of a sporoma collected in Italy, near Iseo Lake (BS), whose identity was checked by molecular analysis (2). Enzymes of wood decay fungi can be exploited as a tool to achieve biodegradation of lignocellulosic agricultural residues aimed at sustainable production of biofuels and chemicals (3). P. meridionalis was therefore tested for the ability of growing on stems of Medicago sativa L., one of the most important plants cultured in Northern Italy. Fungal mycelium grown in liquid cultures was inoculated onto previously triturated and sterilized dried stems in Petri dishes; sterile water was added to keep the fungus hydrated; growth at 37°C was subsequently observed week by week for a month. This temperature was chosen after a preliminary growth profile test on 2% Malt Extract Agar (MEA). Incubation at 37°C resulted in a wide colonized area: even though quantitative determination was not possible, mycelium in fact appeared homogeneously woolly and substratum completely embedded. Microscopy was performed both by: a) optical microscope 100x to 1000x (Zeiss Axioplan); b) SEM (Tescan FE-SEM, MIRA XMU series) which is equipped with EDAX spectrometer, at an accelerating voltage of 15-20 kVolt in high vacuum. Observations were only partially consistent with each other, since SEM allows a much finer discrimination between fungal structures and vegetal ones. Stem appeared deeply destructured by chemical (enzymatic) degradation particularly affecting the not-lignified component. Typical structures of wood decay fungi such as abundant arboriform skeleto-binding hyphae spread as a capillary net were observed. Skeins of hyphal projections with a wide diameter clearly engaged in stem penetration were found; such projections showed sharp distal ends, while proximal ones looked bell-shaped instead. The surface of both hyphal types was often sprinkled with scarce to abundant encrustations likely to be oxalate crystals. Even in substrata poor in minerals, fungi are well known to precipitate cations (and particularly Ca2+) for several alleged functions among which pathogenesis, pH regulation, removal or reservoir of metals (4). These preliminary results show that P. meridionalis displays remarkable versatility being able to efficiently colonize and degrade a substratum unusual for a lignicolous fungus. Quantification of the degree of biodegradation of plant cell wall polymers is in progress.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11571/1182295
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