Coriolopsis rigida, a potential model of white‑rot fungi that produce extracellular laccases

In the last two decades, a significant amount of work aimed at studying the ability of the white-rot fungus Coriolopsis rigida strain LPSC no. 232 to degrade lignin, sterols, as well as several hazardous pollutants like dyes and aliphatic and aromatic fractions of crude oil, including polycyclic aromatic hydrocarbons, has been performed. Additionally, C. rigida in association with arbuscular mycorrhizal fungi appears to enhance plant growth, albeit the physiological and molecular bases of this effect remain to be elucidated. C. rigida's ability to degrade lignin and lignin-related compounds and the capacity to transform the aromatic fraction of crude oil in the soil might be partially ascribed to its ligninolytic enzyme system. Two extracellular laccases are the only enzymatic components of its lignin-degrading system. We reviewed the most relevant findings regarding the activity and role of C. rigida LPSC no. 232 and its laccases and discussed the work that remains to be done in order to assess, more precisely, the potential use of this fungus and its extracellular enzymes as a model in several applied processes

Occurrence and distribution of soil Fusarium species under wheat crop in zero tillage

The presence of Fusarium species in cultivated soils is commonly associated with plant debris and plant roots. Fusarium species are also soil saprophytes. The aim of this study was to examine the occurrence and distribution of soil Fusarium spp. at different soil depths in a zero tillage system after the wheat was harvested. Soil samples were obtained at three depths (0-5 cm, 5-10 cm and 10-20 cm) from five crop rotations: I, conservationist agriculture (wheatsorghum- soybean); II, mixed agriculture/livestock with pastures, without using winter or summer forages (wheatsorghum- soybean-canola-pastures); III, winter agriculture in depth limited soils (wheat-canola-barley-late soybean); IV, mixed with annual forage (wheat-oat/Vicia-sunflower); V, intensive agriculture (wheat-barley-canola, with alternation of soybean or late soybean). One hundred twenty two isolates of Fusarium were obtained and identified as F. equiseti, F. merismoides, F. oxysporum, F. scirpi and F. solani. The most prevalent species was F. oxysporum, which was observed in all sequences and depths. The Tukey's test showed that the relative frequency of F. oxysporum under intensive agricultural management was higher than in mixed traditional ones. The first 5 cm of soil showed statistically significant differences (p = 0.05) with respect to 5-10 cm and 10-20 cm depths. The ANOVA test for the relative frequency of the other species as F. equiseti, F. merismoides, F. scirpi and F. solani, did not show statistically significant differences (p ≤ 0.05). We did not find significant differences (p ≤ 0.05) in the effect of crop rotations and depth on Shannon, Simpson indexes and species richness. Therefore we conclude that the different sequences and the sampling depth did not affect the alpha diversity of Fusarium community in this system.Instituto de Botánica "Dr. Carlos Spegazzini

Pigmentación de un hongo celulolítico asociado al suelo forestal de Nothofagus pumilio

Nothofagus pumilio “lenga” es una especie del bosque andino patagónico que desarrolla sobre suelos de origen volcánico poco profundos del sur de la isla de Tierra del Fuego (Argentina). Este árbol tolera estreses bióticos y abióticos como el causado por insectos defoliadores y frío, respectivamente. Estos factores alteran el bosque y sus componentes, así como la productividad de sus recursos. Humicolopsis cephalosporioides (anamorfo de Ascomycota) forma parte de las comunidades celulolíticas de los bosques de Nothofagus spp. y se caracteriza, entre otras cosas, por la diferenciación de clamidosporas pigmentadas. El objetivo de este trabajo fue identificar y caracterizar el pigmento localizado en las clamidosporas de este hongo. Parámetros físicoquímicos como espectros UV-visible y la solubilización diferencial, así como el cultivo in-vitro con inhibidores específicos de pigmentos oscuros como el ácido kójico, el sulcotrione y el tricyclazol revelaron que las clamidosporas de H. cephalosporioides contienen melaninas tipo 1,8 dihidroxinaftaleno (DHN). Como en otros hongos dematiáceos, se detectó también en fracciones celulares del hongo actividad lacasa, una enzima que se ha asociado a la síntesis de melanina DHN. La asociación entre la diferenciación de clamidosporas y la síntesis de melaninas sugiere que estos pigmentos cumplen un rol en la protección de las esporas a estreses ambientales que atentan contra su viabilidad, lo cual puede ser de relevancia en la dispersión y propagación de este hongo que degrada el mantillo de N. pumilio.</em

Induction, Isolation, and Characterization of Two Laccases from the White Rot Basidiomycete Coriolopsis rigida

Previous work has shown that the white rot fungus Coriolopsis rigida degraded wheat straw lignin and both the aliphatic and aromatic fractions of crude oil from contaminated soils. To better understand these processes, we studied the enzymatic composition of the ligninolytic system of this fungus. Since laccase was the sole ligninolytic enzyme found, we paid attention to the oxidative capabilities of this enzyme that would allow its participation in the mentioned degradative processes. We purified two laccase isoenzymes to electrophoretic homogeneity from copper-induced cultures. Both enzymes are monomeric proteins, with the same molecular mass (66 kDa), isoelectric point (3.9), N-linked carbohydrate content (9%), pH optima of 3.0 on 2,6-dimethoxyphenol (DMP) and 2.5 on 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), absorption spectrum, and N-terminal amino acid sequence. They oxidized 4-anisidine and numerous phenolic compounds, including methoxyphenols, hydroquinones, and lignin-derived aldehydes and acids. Phenol red, an unusual substrate of laccase due to its high redox potential, was also oxidized. The highest enzyme affinity and efficiency were obtained with ABTS and, among phenolic compounds, with 2,6-dimethoxyhydroquinone (DBQH(2)). The presence of ABTS in the laccase reaction expanded the substrate range of C. rigida laccases to nonphenolic compounds and that of MBQH(2) extended the reactions catalyzed by these enzymes to the production of H(2)O(2), the oxidation of Mn(2+), the reduction of Fe(3+), and the generation of hydroxyl radicals. These results confirm the participation of laccase in the production of oxygen free radicals, suggesting novel uses of this enzyme in degradative processes

Physiological and morphological characteristics of yeasts isolated from waste oil effluents

Pichia membranaefaciens, Cryptococcus laurentii, Rhodotorula glutinis and Candida krusei were isolated from contaminated sites. A significant variability in cell forms and in assimilation profiles was observed in the C. krusei strains. The chitin synthase activity and chitin content allowed us to differentiate three strain types. The variability of the phenotypic traits was higher in C. krusei strains isolated from heavily polluted sites.Fil: Romero, Maria Cristina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Botánica Spegazzini; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Gatti, Eleatrice M de Las Mercedes. Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias. Departamento de Microbiología; ArgentinaFil: Córdoba, Susana Beatríz. Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias. Departamento de Microbiología; ArgentinaFil: Cazau, Maria Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Botánica Spegazzini; ArgentinaFil: Arambarri, Angélica Margarita. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Botánica Spegazzini; Argentin