Abstract
Recently introduced micronized copper (MC) formulations, consisting of a nanosized fraction of basic copper (Cu) carbonate (CuCO3·Cu(OH)2) nanoparticles (NPs), were introduced to the market for wood protection. Cu NPs may presumably be more effective against wood-destroying fungi than bulk or ionic Cu compounds. In particular, Cu- tolerant wood-destroying fungi may not recognize NPs, which may penetrate into fungal cell walls and membranes and exert their impact. The objective of this study was to assess if MC wood preservative formulations have a superior efficacy against Cu-tolerant wood-destroying fungi due to nano effects than conventional Cu biocides. After screening a range of wood-destroying fungi for their resistance to Cu, we investigated fungal growth of the Cu-tolerant fungus Rhodonia placenta in solid and liquid media and on wood treated with MC azole (MCA). In liquid cultures we evaluated the fungal response to ion, nano and bulk Cu distinguishing the ionic and particle effects by means of the Cu2+ chelator ammonium tetrathiomolybdate (TTM) and measuring fungal biomass, oxalic acid production and laccase activity of R. placenta. Our results do not support the presence of particular nano effects of MCA against R. placenta that would account for an increased antifungal efficacy, but provide evidence that attribute the main effectiveness of MCA to azoles.
Highlights
Copper (Cu) has long been known for its fungicidal properties and it is an essential biocide for wood in contact with the soil, as it is the only active substance that hitherto successfully inhibits wood decomposition by soft rot fungi [1]
transmission electron microscopy (TEM) grids (400 mesh) coated with 8 nm of carbon were incubated for 20 s on a 10 μl droplet of MC azole (MCA) diluted with nanopure water
Our results showed that T. versicolor 159 and R. placenta 45 were the two strains that were less influenced by the MCA formulations
Summary
Copper (Cu) has long been known for its fungicidal properties and it is an essential biocide for wood in contact with the soil, as it is the only active substance that hitherto successfully inhibits wood decomposition by soft rot fungi [1]. The efficacy of Cu- based wood preservatives against wood- destroying fungi is mainly exerted by Cu in its soluble form, as Cu2+ ions [2,3,4]. An increased copper efficacy may be achieved at the nanoscale: several nanoparticles (NPs) have been shown to be more toxic to prokaryotes and eukaryotes than larger particles of PLOS ONE | DOI:10.1371/journal.pone.0142578. Nano and Bulk Copper against Rhodonia placenta An increased copper efficacy may be achieved at the nanoscale: several nanoparticles (NPs) have been shown to be more toxic to prokaryotes and eukaryotes than larger particles of PLOS ONE | DOI:10.1371/journal.pone.0142578 November 10, 2015
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