Serpula lacrymans is one of the most destructive wood-degrading brown rot fungi in temperate environments. Its virulence has often been linked to its ability to grow over non-woody materials and extract calcium (Ca) or iron (Fe) to promote wood degradation in buildings. This fungus has also been a severe problem in historic wooden warships and in modern wooden vessels, sometimes leading to foundering (break up) in high seas. In recent work, we have found evidence supportive of the theory that S. lacrymans can translocate and utilize elements from non-woody sources. In the research presented here, we provide data that complement earlier work suggesting that calcium can actually inhibit wood degradation by this fungus, while iron impurities can relieve this apparent stress. Oxalate analysis from agar, as well as SEM-EDS imaging of calcium oxalate crystals and direct hyphal contact with gypsum substrates, suggest calcium may bind oxalate non-productively and may limit its role in iron sequestration. Work by other researchers showing calcium can inhibit oxalate from detoxifying copper and showing supplemental iron may help fungi overcome copper-based preservatives support our observations. These results relate directly to cultural management of this destructive fungal pest and lend mechanistic information on the role of oxalate during brown rot.

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