Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 5 de 5
Filtrar
Mais filtros










Tipo de estudo
Intervalo de ano de publicação
1.
Microbiol Res ; 161(4): 299-303, 2006.
Artigo em Inglês | MEDLINE | ID: mdl-16380244

RESUMO

Leucoagaricus gongylophorus, the symbiotic fungus of the leaf-cutting ants, degrades starch, this degradation being supposed to occur in the plant material which leafcutters forage to the nests, generating most of the glucose which the ants utilize for food. In the present investigation, we show that laboratory cultures of L. gongylophorus produce extracellular alpha-amylase and maltase which degrade starch to glucose, reinforcing that the ants can obtain glucose from starch through the symbiotic fungus. Glucose was found to repress alpha-amylase and, more severely, maltase activity, thus repressing starch degradation by L. gongylophorus, so that we hypothesize that: (1) glucose down-regulation of starch degradation also occurs in the Atta sexdens fungus garden; (2) glucose consumption from the fungus garden by A. sexdens stimulates degradation of starch from plant material by L. gongylophorus, which may represent a mechanism by which leafcutters can control enzyme production by the symbiotic fungus. Since glucose is found in the fungus garden inside the nests, down-regulation of starch degradation by glucose is supposed to occur in the nest and play a part in the control of fungal enzyme production by leafcutters.


Assuntos
Agaricales/enzimologia , Agaricales/metabolismo , Formigas/microbiologia , Amido/metabolismo , Simbiose , Agaricales/fisiologia , Animais , Formigas/fisiologia , Folhas de Planta/parasitologia
2.
Folia Microbiol (Praha) ; 50(5): 421-5, 2005.
Artigo em Inglês | MEDLINE | ID: mdl-16475502

RESUMO

A survey of the filamentous fungi other than the symbiotic one found in association with Atta sexdens rubropilosa colonies was carried out. Different fungal species (27 taxa) were isolated a few days after treating the workers with toxic baits (sulfluramid; Mirex-S), from 40 laboratory and 20 field nests. Syncephalastrum racemosum (54%) and Escovopsis weberi (21%), Trichoderma harzianum (38%) and Fusarium oxysporum (23%) were the prevalent species in laboratory and field nests, respectively. Acremonium kiliense, Acremonium strictum, E. weberi, F. oxysporum, Fusarium solani, Moniliella suaveolens and T. harzianum were found in both nests' groups. We revealed that many filamentous fungi can co-exist in a dormant state inside the nests of these insects and some of them appear to be tightly associated with this environment.


Assuntos
Fungos/classificação , Fungos/isolamento & purificação , Himenópteros/microbiologia , Microbiologia do Solo , Animais , Fungos/crescimento & desenvolvimento , Simbiose
3.
Braz. j. med. biol. res ; 37(10): 1463-1472, Oct. 2004. ilus, mapas, tab
Artigo em Inglês | LILACS | ID: lil-383031

RESUMO

Leaf-cutting ants of the genera Atta and Acromyrmex (tribe Attini) are symbiotic with basidiomycete fungi of the genus Leucoagaricus (tribe Leucocoprineae), which they cultivate on vegetable matter inside their nests. We determined the variation of the 28S, 18S, and 5.8S ribosomal DNA (rDNA) gene loci and the rapidly evolving internal transcribed spacers 1 and 2 (ITS1 and ITS2) of 15 sympatric and allopatric fungi associated with colonies of 11 species of leafcutter ants living up to 2,600 km apart in Brazil. We found that the fungal rDNA and ITS sequences from different species of ants were identical (or nearly identical) to each other, whereas 10 GenBank Leucoagaricus species showed higher ITS variation. Our findings suggest that Atta and Acromyrmex leafcutters living in geographic sites that are very distant from each other cultivate a single fungal species made up of closely related lineages of Leucoagaricus gongylophorus. We discuss the strikingly high similarity in the ITS1 and ITS2 regions of the Atta and Acromyrmex symbiotic L. gongylophorus studied by us, in contrast to the lower similarity displayed by their non-symbiotic counterparts. We suggest that the similarity of our L. gongylophorus isolates is an indication of the recent association of the fungus with these ants, and propose that both the intense lateral transmission of fungal material within leafcutter nests and the selection of more adapted fungal strains are involved in the homogenization of the symbiotic fungal stock.


Assuntos
Animais , Formigas , DNA Espaçador Ribossômico , Fungos , Simbiose , Brasil , Variação Genética , Folhas de Planta , Reação em Cadeia da Polimerase , Análise de Sequência de DNA
4.
Braz J Med Biol Res ; 37(10): 1463-72, 2004 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-15448866

RESUMO

Leaf-cutting ants of the genera Atta and Acromyrmex (tribe Attini) are symbiotic with basidiomycete fungi of the genus Leucoagaricus (tribe Leucocoprineae), which they cultivate on vegetable matter inside their nests. We determined the variation of the 28S, 18S, and 5.8S ribosomal DNA (rDNA) gene loci and the rapidly evolving internal transcribed spacers 1 and 2 (ITS1 and ITS2) of 15 sympatric and allopatric fungi associated with colonies of 11 species of leafcutter ants living up to 2,600 km apart in Brazil. We found that the fungal rDNA and ITS sequences from different species of ants were identical (or nearly identical) to each other, whereas 10 GenBank Leucoagaricus species showed higher ITS variation. Our findings suggest that Atta and Acromyrmex leafcutters living in geographic sites that are very distant from each other cultivate a single fungal species made up of closely related lineages of Leucoagaricus gongylophorus. We discuss the strikingly high similarity in the ITS1 and ITS2 regions of the Atta and Acromyrmex symbiotic L. gongylophorus studied by us, in contrast to the lower similarity displayed by their non-symbiotic counterparts. We suggest that the similarity of our L. gongylophorus isolates is an indication of the recent association of the fungus with these ants, and propose that both the intense lateral transmission of fungal material within leafcutter nests and the selection of more adapted fungal strains are involved in the homogenization of the symbiotic fungal stock.


Assuntos
Formigas/fisiologia , DNA Espaçador Ribossômico/genética , Fungos/genética , Variação Genética , Simbiose , Animais , Brasil , Fungos/fisiologia , Folhas de Planta , Reação em Cadeia da Polimerase , Análise de Sequência de DNA
5.
Folia Microbiol (Praha) ; 47(3): 259-62, 2002.
Artigo em Inglês | MEDLINE | ID: mdl-12099266

RESUMO

Killer activity was screened in 99 yeast strains isolated from the nests of the leaf-cutting ant Atta sexdens against 6 standard sensitive strains, as well as against each other. Among this yeast community killer activity was widespread since 77 strains (78%) were able to kill or inhibit the growth of at least one standard strain or nest strain. Toxin production was observed in representatives of all the studied genera including Aureobasidium, Rhodotorula, Tremella and Trichosporon, whose killer activity has not yet been described.


Assuntos
Formigas/microbiologia , Leveduras/isolamento & purificação , Animais , Meios de Cultura , Concentração de Íons de Hidrogênio , Fatores Matadores de Levedura , Micotoxinas/análise , Micotoxinas/isolamento & purificação , Fenótipo , Rhodotorula/isolamento & purificação , Rhodotorula/metabolismo , Especificidade da Espécie , Trichosporon/isolamento & purificação , Trichosporon/metabolismo , Leveduras/classificação , Leveduras/metabolismo
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...