Araceli Marcela Ramos

Copper induction of lignin-modifying enzymes in the white-rot fungus Trametes trogii.

Trametes trogii, a white rot basidiomycete involved in wood decay worldwide, produces several ligninolytic enzymes, laccase being the dominant one, with higher titers than those reported for most other white rot fungi studied up to date. The effect of copper on in vitro production of extracellular ligninolytic activities was studied. CuSO4·5H2O concentrations from 1.6 μM to 1.5 mM were tested in a synthetic medium with glucose 20 g/L and asparagine 3 g/L. The addition of copper (up to 1 mM) did not affect growth but strongly stimulated ligninolytic enzyme production; faster decolorization of the polymeric dye Poly R-478 was observed as well. Maximal production of manganese peroxidase, laccase, and glyoxal oxidase [1.28 U/mL, 93.8 U/mL (with a specific activity of 720 U/mg protein), and 0.46 U/mL respectively] was attained with 1 mM CuSO4·5H2O. However, higher copper concentrations inhibited growth and notably decreased manganese peroxidase production, although they did not affect laccase secretion. Laccase activity in the culture filtrate was maximal at 50 C and pH 3.4, and the enzyme was completely stable at pH 4.4 and above, and at 30 C for up to 5 d. Denaturing polyacrylamide gel electrophoresis of extracellular culture fluids showed two laccase activity bands (mol wt 38 and 60 kDa respectively). The pattern of isoenzyme production was not affected by medium composition but differed with culture age.

Pectinolytic enzyme production by Colletotrichum truncatum, causal agent of soybean anthracnose

BACKGROUND Colletotrichum truncatum is the most common pathogenic fungus associated with soybean anthracnose, a prevalent disease in Argentina. Pectinolytic enzymes are involved in the pathogenicity of a wide range of plant pathogenic fungi. OBJECTIVES To explore pectinolytic enzyme production in Argentinian Colletotrichum strains isolated from diseased soybean plants from different geographic locations, as a preliminary step to establish the biological role of the pectinolytic enzymes in the Colletotrichum spp.-soybean system, yet unknown. METHODS Ten strains were screened for in vitro pectinolytic enzyme production on a defined medium based on pectin as carbon source. RESULTS All isolates were able to grow in this medium and polymethylgalacturonase (PMG), polygalacturonase (PG) and pectin lyase (PL) activities were detected. On the whole, the peak of polygalacturonases activities preceded the day of maximum growth, while PL activity reached its highest level afterwards. Strain BAFC 3097 (from Santa Fe province) yielded high titles of the three enzymes (1.08U/ml PG, 1.05U/ml PMG, 156U/ml PL), after a short incubation period (7-10 days). Low synthesis of polygalacturonases in cultures containing glucose as unique carbon source suggests that these enzymes are constitutive in contrast with PL, which was not detected. CONCLUSIONS The disparity observed in enzyme production among strains cannot be related to fungal growth, since no major differences in mycelial yield were found; it was not connected with their geographic origin, but might be associated with differences in virulence among strains not yet evaluated.

Factors influencing cellulase production Saccobolus saccoboloides

Saccobolus saccoboloides was grown in a liq? uid synthetic medium with crystalline cellulose as the only carbon source. Culture supernatant was used to measure activities of the enzymes of the cellulolytic complex: (3-1,4 endoglucanase, (3-1,4 exoglucanase and p-glucosidase. The kinetics of growth and en? zyme production were studied in static and shaken cultures. The influence of various nitrogen sources, on production of the various cellulases in the culture medium was investigated. Growth and cellulolytic en? zymes production were maximal when organic ni- trogenous compounds were supplied. Enzymatic pro? duction was maximal at an initial pH of the growth medium of 6.5. Enzymatic activities were favored in the range of 50-55 C and pH 4.8-5.4.

Molecular characterization of Colletotrichum species causing soybean anthracnose in Argentina

Twenty-six isolates obtained from soybean crops (Glycine max) with typical anthracnose symptoms were identified as Colletotrichum truncatum (73 %) and C. destructivum (26 %). Their genetic relationships were studied using the AFLP method. A UPGMA phenogram divided the strains into two clusters corresponding with the two species. Genetic distances based on association coefficient were 0.71–0.89 among the 18 C. truncatum strains and 0.67–1 among the eight C. destructivum strains. Genetic variability within species, measured in terms of percentage of polymorphic loci, was high (<90%). Only two isolates showed 100% similarity, suggesting high intraspecific variability.

AFLP molecular characterizations of some Saccobolus species (Ascomycota, Pezizales)

Fil: Ramos, Araceli Marcela. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Instituto de Micologia y Botanica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Micologia y Botanica; Argentina

AFLP characterization in pathogenic and coprophilous fungi.

Fil: Cinto, Isabel Esther. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Instituto de Micologia y Botanica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Micologia y Botanica; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biologia Experimental; Argentina