Ultrastructural changes during wood decay by Antrodiella sp. RK1.

Area of Science:

• Wood Science and Technology
• Microbiology
• Biotechnology

Background:

• Fungal decay is a significant factor in wood degradation, impacting its structural integrity and economic value.
• Understanding the mechanisms of wood decay by specific fungal species is crucial for developing effective conservation and bioremediation strategies.
• Southern yellow pine (softwood) and maple (hardwood) represent commercially important timber species with distinct structural properties.

Purpose of the Study:

• To investigate the efficacy of Antrodiella sp. RK1 in degrading softwood and hardwood.
• To analyze the biochemical and ultrastructural changes in wood tissues following fungal treatment.
• To determine the selectivity of fungal degradation towards specific wood components, particularly lignin and carbohydrates.

Main Methods:

• Incubation of southern yellow pine and maple wood samples with Antrodiella sp. RK1 for 12 weeks.
• Quantification of weight loss and analysis of wood sugar composition (glucose, xylose, arabinose, galactose, mannose).
• Microscopic examination using Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) to observe decay structures and fungal morphology.

Main Results:

• Antrodiella sp. RK1 caused substantial weight loss (20% in softwood, 19% in hardwood) and significant lignin degradation (34-35%).
• The fungus exhibited preferential lignin removal over glucose, with higher lignin loss to glucose loss ratios in softwood (3.6) compared to hardwood (2.7).
• SEM and TEM revealed extensive decay, including erosion troughs, bore holes, delignification of secondary walls, and hyphal penetration through cell corners, with abundant Ca(2+) crystals observed.

Conclusions:

• Antrodiella sp. RK1 is an effective wood-decay fungus capable of degrading both softwood and hardwood.
• The fungus primarily targets lignin, while largely preserving other wood sugars, indicating a specific enzymatic degradation pathway.
• Ultrastructural analysis provides insights into the fungal colonization and degradation strategy, highlighting cell corner decay and hyphal penetration.