Aims: For Ophiostoma (Ceratocystis) ulmi, the ability to undergo morphological change is a crucial factor for its virulence. To gain an understanding of quorum-sensing activity in O. ulmi as it relates to yeast-mycelium dimorphism control, this study examines the effects of branched-chain amino acids as well as their fusel alcohols and fusel acids as quorum sensing molecules. Methods and Results: In a defined medium containing glucose, proline and salts, O. ulmi grew as yeasts when the culture was inoculated with a high density of spores (2 × 10⁷ CFU ml⁻¹) and as mycelia when inoculated with a low spore density (4 × 10⁵ CFU ml⁻¹). The cultures displaying yeast morphology secreted a quorum-sensing factor that shifted the morphology from mycelia to yeast. This quorum-sensing molecule was lipophilic and extractable by organic solvents from the spent medium. Using GC/MS analysis, it was determined that the major compound in the extract was 2-methyl-1-butanol. A similar effect was observed when the branched-chain amino acids (fusel alcohol precursors) were used as the nitrogen source. E, E-farnesol had no effect on the morphology of O. ulmi. Conclusions: Addition of the branched-chain amino acids or one of the compounds detected in the spent medium, 2-methyl-1-butanol or 4-hydroxyphenylacetic acid, or methylvaleric acid, decreased germ tube formation by more than 50%, thus demonstrating a quorum sensing molecule behaviour in O. ulmi cultures. Significance and impact of the study: This study presents advances in the investigation of dimorphism in O. ulmi, complementing the existing scientific basis, for studying, understanding and controlling this phenomenon.

Radiata pine is the main wood species used in the Chilean construction industry, but it must be protected due to its low natural durability. Chemical protection of wood by impregnation allows for a more efficient utilization of the forest resources by extending its useful life. The use of nanoparticles in wood protection has garnered great interest during the last decade, due to their unique physicochemical properties, different from those of larger sized materials. In this research, the impregnation of radiata pine wood with copper nanoparticles (CuNP) was studied in terms of retention, penetration, leaching, and its protective effect against wood rot fungi growth according to EN 113, AWPA A3-91, A9-18, and E11-16. Penetration analysis confirmed a uniform distribution across the wood, with total penetration in the impregnated samples with the highest concentration solution of CuNP. Retention values of the impregnated wood increased proportionally with the concentration of nanoparticles evaluated by EDXRF. Leaching analysis showed copper removal during the first hours of the test, with a constant leaching rate up to 144 h. Impregnated wood mass loss (ML) due to exposure to Gloeophyllum trabeum and Rhodonia placenta fungi were significantly reduced regardless of the CuNP concentration or fungi tested, with an ML smaller than 5% and smaller than 14% for leached samples.

Thraustochytrids are unicellular heterotrophic marine protists that have been described as producing a high content of polyunsaturated fatty acids (PUFAs). Among them, arachidonic acid (ARA) stands out as a precursor of several mediators of pivotal importance for the immune system. However, the biotechnological potential of thraustochytrids for ARA production has not been developed. The objective of this study is to isolate and identify native strains from different Chilean coastal environments and evaluate in vitro the effect of culture parameters such as C/N ratio (19 and 33) and temperature (15 °C and 23 °C) on biomass production and arachidonic acid content. A total of nine strains were identified and classified into four genera of the Thraustochitridae family. The Lng2 strain with 99% identity belongs to the species Ulkenia visurgenis and was the most prominent one for ARA production. Temperature had an effect on the PUFA profile but not on the ARA content nor on the biomass yield. Additionally, the C/N ratio has been identified as a key parameter. The ARA productivity increased by 92% (from 0.6 to 8.3 ARA mg/g-DW) and its total biomass by 62.7% (from 1.9 to 5.1 g/L) at a high C/N ratio (33) as compared to the control.

Wood extractives promote pitch formation during pulp and paper manufacturing. To date, this problem has been controlled by extended storage of the chips and/or chemical additives. Biotreatment of the wood prior to pulping provides an alternative that not only decreases the negative impact of the extractives but may also improve the kraft pulping efficiency. This initiative seeks to verify the quantity and chemical composition of Eucalyptus nitens wood extractives following biotreatment with three albino fungi species (Ophiostoma floccosum, Ophiostoma piceae and Ophiostoma piliferum). Eucalyptus nitens wood chips were sprayed with spore suspensions of Ophiostoma piliferum, Ophiostoma piceae and Ophiostoma floccosum albino strains (1 × 108 spore concentration). After 7 and 21 days of fungal treatment, the extractive content was determined via Soxhlet extraction with an 80:20% n-hexane:ethyl acetate solvent mixture. The Ophiostoma floccosum F1A94, Ophiostoma piliferum F2D8 and Ophiostoma piceae F2A68 strains proved to be most capable of bioreduction with reductions of 35.1%, 33.2% and 29.3%, respectively. The chemical composition of the extract was analyzed via gas chromatography coupled with mass spectrometry, which demonstrated that most of the tested strains could reduce the β-sitosterol content.

Los hongos del género Ophiostoma promueven la ocurrencia de la mancha azul en madera de coníferas, afectando significativamente la calidad en los productos de apariencia. Para la prevención de la mancha azul se han empleado productos químicos de diferente naturaleza. El control biológico de la mancha azul con cepas albinas del género Ophiostoma aparece como una alternativa de promisorio potencial. Algunos de estos hongos cuando cultivados en medio líquido presentan un crecimiento dimórfico, con alta proporción de micelio, que dificulta su utilización. El dimorfismo, transformación reversible de las morfologías levadura y micelio, es controlado por factores químicos y del entorno. En esta investigación mediante la aplicación de un diseño factorial completo de dos niveles, se estudió el efecto de cuatro variables operacionales sobre el crecimiento levaduriforme de la cepa albina PcF2A29 de la especie Ophiostoma piceae (Münch) H. & P. Syd., creciendo en medio de cultivo líquido complejo. Los resultados mostraron que el tamaño del inóculo, la temperatura y la interacción tamaño del inóculo-temperatura tuvieron un efecto estadístico significativo sobre el crecimiento levaduriforme de la cepa albina PcF2A29de la especie O. piceae. De estas variables, el tamaño del inóculo resultó ser el efecto más importante y explicó el 53% de la variabilidad observada. Estos resultados sugieren por primera vez, en la especie O. piceae, la existencia de un mecanismo de detección del quórum asociado a la variable tamaño del inóculo. AbstractOphiostoma fungi promote the occurrence of blue stain in coniferous wood, affecting the appearance wood products quality. Thus, different chemical products have been attempted to control them. Biological control of these sapstaining fungi, using albino strains of Ophiostoma looks like a successfully alternative to be applied. However, some Ophiostoma strains present a dimorphic behavior in liquid culture, which make them difficult to work with. Fungal dimorphism is defined as an environmentally and chemically controlled, reversible transformation of the yeast and mycelia morphologies. In this research, a two level factorial design was applied for evaluating the effect of four operative variables on albino strain PcF2A29 (Ophiostoma piceae (Münch) H. & P. Syd.) yeast-like growth a complex liquid medium. The results showed that inoculum size, temperature and their interaction had a statistically significant effect on yeast-like growth of albino strain PcF2A29. The most important effect was inoculum size. This factor explained 53% of the observed variability. The effect of inoculum size on yeast-like growth, phenomenon that is described in the O. piceae species by the first time with this paper, would be associated to quorum sensing activity.