Eduardo Gross

Influence of arbuscular mycorrhizal fungi on growth, mineral composition and production of essential oil in Mentha × piperita L. var. citrata (Ehrh.) Briq. under two phosphorus levels

The aim of the study was to evaluate the effect of the arbuscular mycorrhizal fungi (AMF), Acaulospora morrowiae, Rhizophagus clarus and Scutellospora calospora on the growth and essential oil production of Mentha × piperita L. var. citrata plants. The experiment was conducted in a greenhouse with a 5 × 2 factorial design with five mycorrhizal treatments (uninoculated control, Acaulospora morrowiae, Rhizophagus clarus and Scutellospora calospora, and mixture of inocula) and two P levels (60 and 120 mg P dm-3 soil) with six replicates. Plants were harvested after 75 days of growth for evaluation of dry biomass, mycorrhizal colonization of roots, number of spores in soil, nutrient content of leaves, and composition, content and yield of essential oil. The mycorrhizal treatments influenced all the characteristics evaluated, except the number of spores in soil. AMF colonization was most evident at the lowest dose of phosphate fertilizer applied, except for R. clarus, and in all treatments mycorrhizal colonization was above 45%. Colonization also influenced the nutrient content of the leaves of M. piperita var citrata and increased leaf dry biomass. The content and yield of essential oils were higher in plants colonized by AMF fungi with the 60 mg P fertilization dose, except those colonized by R. clarus which had higher essential oil production only with the 120 mg dm-3 P treatment. The two major components in the essential oils for the plants in all the treatments were linalool and linalyl acetate. n n xa0 n n Key words: Acaulospora, Rhizophagus, Scutellospora, linalool, linalyl acetate, phosphorus fertilization.

Trichoderma asperelloides ethanolic extracts efficiently inhibit Staphylococcus growth and biofilm formation

Fungi from the widely distributed genus Trichoderma are of great biotechnological interest, being currently used in a vast range of applications. Here, we report that high-molecular weight fraction (HWF) derived from Trichoderma asperelloides ethanolic extract exhibits antibiotic activity against staphylococcal biofilms. The antibacterial and anti-biofilm properties of T. asperelloides extracts were evaluated by well-established assays in Staphylococcus aureus ATCC strains (29213 and 6538) and in one clinical isolate from bovine mastitis. The HWF from T. asperelloides eradicated S. aureus by causing substantial matrix de-structuring and biomass reduction (p < 10−5) at concentrations as low as 2.3 μg mL-1. Additionally, we present ultra-structure analysis by the use of scanning electron microscopy as well as transmission microscopy, which showed that T. asperelloides killed cells through cell wall and membrane disturbance. Remarkably, the HWF from T. asperelloides killed S. aureus and eradicated its biofilms in a greater performance than gentamicin (p < 10−5), a known potent antibiotic against S. aureus. Our results indicate that extract from T. asperelloides may represent a promising candidate for the development of new antibiotics against gram-positive bacteria.

Ammonia oxidation (amoA) and nitrogen fixation (nifH) genes along metasandstone and limestone caves of Brazil

Abstract Many cave-dwelling microorganisms have been studied, but little is known about whether genes related to the nitrogen cycle are present in this environment, particularly in sandstone caves. The profiles of nitrogen fixation (nifH) and archaeal and bacterial ammonia oxidation (amoA) genes were analyzed along a cave of metasandstone and limestone lithologies. Using polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis and quantitative PCR to evaluate these genes, we analyzed the variations in the microorganisms and frequency of these genes along the caves. In both caves analyzed for nifH, different community profiles were observed, particularly in entrance samples. Quantitative PCR of the genes showed that samples from the entrance of the caves contained a larger number of copies of amoA. In addition, archaeal amoA was predominant compared to bacterial amoA. The present study demonstrated that the genes for nitrogen fixation and ammonia oxidation are present in both cave lithologies and that their frequency and the organisms present along the caves vary with factors such as the characteristics of the cave itself.

Cadmium induced changes in Solidago chilensis Meyen (Asteraceae) grown on organically fertilized soil with reference to mycorrhizae, metabolism, anatomy and ultrastructure

Solidago chilensis Meyen (Asteraceae) is a medicinal important plant with few studies on nutrition and metabolism and none information on cadmium phytotoxicity. The objective of this study was to investigate Cd induced responses on the growth and metabolism in S. chilensis and on arbuscular mycorrhiza (AM). The experiment was carried out in a greenhouse, consisting of a 5 × 4 factorial with five doses of manure (0, 3.5, 7, 14 and 21gdm-3) and four doses of cadmium (0, 25, 50 and 75mgdm-3) applied to a Dystrophic Ultisol. After 250 days of plant cultivation, biomass, nutrient content, photosynthetic rate, guaiacol peroxidase activity, mycorrhizal colonization, glomalin content, anatomical and ultrastucture were evaluated. Plants were significantly affected by interaction of manure and Cd doses with anatomical, ultrastructural, physiological and nutritional modifications. Manure applied into Cd contaminated soil significantly improved mycorrhizal colonization and glomalin production. The highest organic manure dose (21gdm-3) alleviated toxicity symptoms of Cd on S. chilensis.

Improvement in menthol extraction of fresh leaves of Mentha arvensis by the application of multi-enzymatic extract of Aspergillus niger

Abstract The objective of this study was to optimize the enzymatic pretreatment process of extracting menthol, a major component of the essential oil stored in the trichomes of fresh leaves of Mentha arvensis, by the action of the crude enzymatic extract previously produced by the Aspergillus niger fungus cultivated in cactus pear. Under the experimental conditions of 42u2009°C, 141u2009min and 58u2009mL of enzyme in 442u2009mL of water, there was an increase of 186.63% in the hydrodistillation yield, which represents an acceptable positive deviation of 12.54% compared to the predicted value of the model obtained by experimental design. Trichome rupture can be confirmed by scanning electron microscopy (SEM) and the chemical structure of the obtained menthol was not modified according to gas chromatography and infrared spectroscopy. The enzymatic pretreatment applied before the hydrodistillation step was successful and proves the potential of the association of biotechnological techniques with a physicochemical process.

Peach-palm (Bactris gasipaes Kunth.) waste as substrate for xylanase production by Trichoderma stromaticum AM7

ABSTRACT This work investigated the xylanase production by fungi isolates from tropical agroforestry systems using peach-palm industrial waste as a substrate. Trichoderma stromaticum AM7 was the best xylanase producer and there was a 160% increase in xylanase activity after optimizing by the Box–Behnken statistical design. The optimization process demonstrated that the maximum activity occurred at 0.95% nitrogen concentration after 6 days of cultivation at 32°C, which achieved a yield of 1440u2009Uu2009g−1 of dry initial substrate. Analysis by scanning electron microscopy showed degradation of the fibers after cultivation. The optimum pH and temperature for xylanase activity were 5.0 and 50°C, respectively. The extensive degradation of the peach-palm waste and xylanase production by T. stromaticum AM7 was due to the combination of a good physicochemical composition of the culture medium and the characteristics of the selected fungus.

ATIVIDADE MICROBIANA EM DIFERENTES CONDIÇÕES DE SOLO E SISTEMAS DE CULTIVO DO CACAUEIRO

As práticas de manejo da terra ou das culturas interferem na estrutura e na atividade microbiana que está direta e fundamentalmente relacionada com as propriedades do solo. As principais atividades dos microrganismos são a decomposição da matéria orgânica e ciclagem de energia e nutrientes, indispensáveis para o crescimento das plantas. A medição de CO 2 liberada pela respiração dos microrganismos aeróbicos e anaeróbicos é um dos métodos mais tradicionais e utilizados para avaliar a atividade metabólica da microbiota do solo. O presente trabalho teve como objetivo estimar a atividade microbiana em 14 áreas, considerando-se diferentes solos e sistemas de produção de cacau. O estudo foi conduzido na Bahia, Brasil, comparando-se tratamentos correspondentes aos sistemas tradicional, SAFs e orgânico de cultivo do cacaueiro. As amostras de solo (de 0-15 cm), em triplicatas, foram coletadas e analisadas quanto à evolução de CO 2 , e propriedades químicas e físicas. A evolução de CO 2 foi maior nos solos 14 (Nitossolo Háplico Eutrófico) e 11 (Cambissolo Háplico Distrófico típico), ambos com cacau cabruca orgânico, em condições edáficas mais favoráveis à microbiota do solo. Os solos com menor atividade microbiana (área 6 Argissolo Vermelho-Amarelo Distrocoeso abrúptico; área 3 Latossolo Amarelo Distrófico câmbico; e área 1 Latossolo Vermelho-Amarelo Distrófico típico), são cultivados em SAF cacau x seringueira e apresentaram limitações de fertilidade.