Microfungal 'Weeds' in the Leafcutter Ant Symbiosis

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Antagonistic interactions between garden yeasts and microfungal garden pathogens of leaf-cutting ants

We investigate the diversity of yeasts isolated in gardens of the leafcutter ant Atta texana. Repeated sampling of gardens from four nests over a 1-year time period showed that gardens contain a diverse assemblage of yeasts. The yeast community in gardens consisted mostly of yeasts associated with plants or soil, but community composition changed between sampling periods. In order to understand the potential disease-suppressing roles of the garden yeasts, we screened isolates for antagonistic effects against known microfungal garden contaminants. In vitro assays revealed that yeasts inhibited the mycelial growth of two strains of Escovopsis (a specialized attine garden parasite), Syncephalastrum racemosum (a fungus often growing in gardens of leafcutter lab nests), and the insect pathogen Beauveria bassiana. These garden yeasts add to the growing list of disease-suppressing microbes in attine nests that may contribute synergistically, together with actinomycetes and Burkholderia bacteria, to protect the gardens and the ants against diseases. Additionally, we suggest that garden immunity against problem fungi may therefore derive not only from the presence of disease-suppressing Pseudonocardia actinomycetes, but from an enrichment of multiple disease-suppressing microorganisms in the garden matrix.

Yeasts and filamentous fungi carried by the gynes of leaf-cutting ants

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Filamentous fungi found in Atta sexdens rubropilosa colonies after treatment with different toxic bait formulations

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Selective isolation of dematiaceous fungi from the workers of Atta laevigata (Formicidae: Attini)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Phylogeny of leafcutter ants in the genus Atta Fabricius (Formicidae: Attini) based on mitochondrial and nuclear DNA sequences

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

COEVOLUTION BETWEEN ATTINE ANTS and ACTINOMYCETE BACTERIA: A REEVALUATION

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Generation of Nutrients and Detoxification: Possible Roles of Yeasts in Leaf-Cutting Ant Nests.

The possible roles played by yeasts in attine ant nests are mostly unknown. Here we present our investigations on the plant polysaccharide degradation profile of 82 yeasts isolated from fungus gardens of Atta and Acromyrmex species to demonstrate that yeasts found in ant nests may play the role of making nutrients readily available throughout the garden and detoxification of compounds that may be deleterious to the ants and their fungal cultivar. Among the yeasts screened, 65% exhibited cellulolytic enzymes, 44% exhibited pectinolytic activity while 27% and 17% possess enzyme systems for the degradation of protease and amylase, respectively. Galacturonic acid, which had been reported in previous work to be poorly assimilated by the ant fungus and also to have a negative effect on ants' survival, was assimilated by 64% and 79% of yeasts isolated from nests of A. texana and Acromyrmex respectively. Our results suggest that yeasts found in ant nests may participate in generation of nutrients and removal of potentially toxic compounds, thereby contributing to the stability of the complex microbiota found in the leaf-cutting ant nests.

Monoculture of Leafcutter Ant Gardens

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Nodulação e micorrização em Anadenanthera peregrina var. falcata em solo de cerrado autoclavado e não autoclavado

Anadenanthera peregrina var. falcata (angico-do-cerrado), uma leguminosa arbórea, forma associações simbióticas com bactérias fixadoras de nitrogênio (rizóbios) e com fungos micorrízicos arbusculares. Com o objetivo de avaliar a eficiência da inoculação de fungos micorrízicos e rizóbios no crescimento inicial de plantas de angico-do-cerrado, crescidas em solo autoclavado e em solo não autoclavado com e sem inoculação, foi desenvolvido um experimento em casa de vegetação, utilizando raízes micorrizadas de milho e uma mistura de isolados de rizóbios como inoculantes. O crescimento das plantas foi influenciado positivamente pela concomitante inoculação do fungo micorrízico e do rizóbio, tendo as plantas desse tratamento apresentado biomassa cerca de 60 % maior do que o controle no décimo mês. A inoculação de apenas um dos microssimbiontes, entretanto, não provocou diferença na produção de biomassa das plantas. A percentagem de colonização micorrízica foi significativamente mais alta e o número de nódulos maior nas raízes das plantas crescidas no solo não autoclavado, ocasionados pela população de fungos e rizóbios nativos. Nesse tratamento, houve pequeno acúmulo de matéria no xilopódio, provavelmente em virtude do dreno fotossintético por parte dos microssimbiontes, e a concentração de P na parte aérea e xilopódio dessas plantas foi cerca de 1,2 e 8 vezes maior, respectivamente, por causa da colonização micorrízica.

Analysis of Ant Communities Comparing Two Methods for Sampling Ants in an Urban Park in the City of São Paulo, Brazil

This study aimed to analyze the species composition and functional groups of the ant community and to assess the efficiency of two sampling methods, pitfall and leaf litter sampling, in an urban park. A total of 1,401 ants were collected, which belonged to six subfamilies and 36 species. The predominant species was Wasmannia auropunctata (present in 45.36% of the samples), while the functional group of opportunistic ants were the most frequent (present in 83.75% of the samples) and abundant (95.29% of the total collected specimens) functional group. The Jaccard Similarity Index showed a low similarity between the two sampling methods, as the difference of the number of individuals for each species between these two methods was not significant in only one case (Linepithema sp. 1, p = 0.4561). The fungus-growing and cryptic ants were more collected in leaflitter samples (p<0.0001; p = 0.0348 respectively). Although there was no significant difference (p = 0.6397) between the two sampling methods for the total individuals of opportunistic ants, more species of this group were collected in pitfall traps. This difference was not significant because of the high presence of W. auropunctata, an opportunistic ant, in samples of leaf litter. Due to the predominance of tramp ants in the studied area, this article illustrates the importance of green urban areas in ant control strategies, since these sites could be used as a source of new colonization for these ants. Furthermore, the combination of the two sampling methods seems to be complementary for obtaining a more complete picture of the ant community.

Screening of culture condition for xylanase production by filamentous fungi

The objective of this research was to investigate xylanase production by filamentous fungi (Trichoderma viride) to determine the best cultivation conditions in the process, aiming toward optimization of enzyme production. The best temperature, as well as the best carbon source, for biomass production was determined through an automated turbidimetric method (Bioscreen-C). The enzyme activity of this fungus was separately evaluated in two solid substrates (wheat and soybean bran) and in Vogel medium, pure and by adding other carbon sources. Temperature effects, cultivation time, and spore concentrations were also tested. The best temperature and carbon source for enzyme and biomass production was 25 C and sorbitol, respectively. Maximum xylanase activity was achieved when the fungus was cultivated in wheat bran along with sorbitol (1%, w/v), using a spore concentration of 2 x 10(6) spores. mL(-1), pH 5.0, for 144 h cultivation. The study demonstrated not only the importance of the nature of the substrate in obtaining a system resistant to catabolic repression, but also the importance of the culture conditions for biosynthesis of this enzyme. T. viride showed a high potential for xylanase production under the conditions presented in these assays.

Production of thermostable glucoamylase by newly isolated Aspergillus flavus A 1.1 and Thermomyces lanuginosus A 13.37

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Production and characterization of a milk-clotting protease in the crude enzymatic extract from the newly isolated Thermomucor indicae-seudaticae N31 (Milk-clotting protease from the newly isolated Thermomucor indicae-seudaticae N31)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Production and characterization of polygalacturonase from thermophilic Thermoascus aurantiacus on submerged fermentation

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)