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1.
J Microbiol Methods ; 60(1): 31-40, 2005 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-15567222

RESUMEN

Natamycin is commonly used to control fungal growth on agar media used for bacterial enumeration or strain isolation. However, there is no conclusive report on the possible effect of this antibiotic on bacterial growth or on the diversity of the recovered soil bacteria. Therefore, the possible effects of natamycin on the numbers of bacteria isolated at 12 degrees C from three different soils and soybean rhizosphere soil were investigated using natamycin concentrations ranging from 0 to 200 mg l(-1). Our results demonstrate that natamycin concentrations, which inhibit the growth of fungi on the media, have a small but significant inhibitory effect on the number of bacterial colony forming units. A natamycin concentration of 50-200 mg l(-1) is required for an efficient control of fungal growth on media in our experimental conditions depending on the soil type. Bacterial community structure was assessed on culturable cells (cells washed from enumeration plates: plate-wash approach) obtained at 12 degrees C from soybean rhizosphere soil by performing Ribosomal Intergenic Spacer Analysis (RISA) fingerprinting. We demonstrate that all natamycin concentrations used alter the structure of the recovered, culturable bacterial community, compared to control without natamycin. Using ARDRA (amplification of the 16S rDNA gene and restriction analysis) genotyping of individual isolates, some differences were observed between the bacterial isolates obtained in the presence or absence of natamycin. Bacterial isolates recovered in the presence of natamycin are more tolerant (maximal growth rate and lag phase) to this compound than those isolated without natamycin, indicating a possible selection of resistant strains. Therefore, high concentration of natamycin cannot be used for isolation of bacterial strains with the aim of studying biodiversity and could bias a selection of strains for practical applications.


Asunto(s)
Antifúngicos/farmacología , Bacterias/efectos de los fármacos , Natamicina/farmacología , Microbiología del Suelo , Bacterias/genética , Bacterias/aislamiento & purificación , Bacterias/metabolismo , Recuento de Colonia Microbiana , Dermatoglifia del ADN , Enzimas de Restricción del ADN/metabolismo , ADN Bacteriano/química , ADN Bacteriano/genética , ADN Espaciador Ribosómico/química , ADN Espaciador Ribosómico/genética , Variación Genética , Raíces de Plantas/microbiología , Análisis de Componente Principal , ARN Ribosómico 16S/química , ARN Ribosómico 16S/genética , Glycine max/microbiología
2.
Pest Manag Sci ; 58(12): 1229-35, 2002 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-12476996

RESUMEN

Nutrient-agar plates containing isoxaben (500 mg litre(-1)) were used to isolate isoxaben-metabolising bacteria from four European soils incubated with the herbicide under laboratory conditions. In flask experiments, inoculation of a basal salts medium containing nitrogen and [phenyl-U-14C]isoxaben with an isolate (B2b) resulted in 33% recovery of the initial radioactivity as [14C]carbon dioxide after 2 weeks. A major metabolite identified by GC-MS and NMR analysis as 3-(1-ethyl-1-methylpropyl)isoxazol-5-ylamine accumulated both in basal salts and nutrient broth media. 2,6-Dimethoxybenzoic acid, a suspected metabolite of isoxaben, was not detected in either liquid media. However, the capability of the B2b isolate to use 2,6-dimethoxybenzoic acid as a source of carbon was demonstrated. Soil inoculation with the B2b strain resulted in an increase in the recovery of [14C] carbon dioxide from both [phenyl-U-14C] and [isoxazole-5-14C]isoxaben. The metabolite identified as 3-(1-ethyl-1-methylpropyl)isoxazole-5-ylamine only accumulated if the soil was autoclaved before inoculation. This metabolite was rapidly mineralized by the microflora of a natural soil without history of isoxaben treatment. Homology patterns of sequenced 16S rDNA between isoxaben-transforming isolates and reference strains showed that the four isolates identified belonged to the genus Microbacterium.


Asunto(s)
Bacterias/metabolismo , Benzamidas/metabolismo , Benzoatos/metabolismo , Herbicidas/metabolismo , Isoxazoles/metabolismo , Microbiología del Suelo , Bacterias/genética , Bacterias/aislamiento & purificación , Benzamidas/química , Benzoatos/química , Biodegradación Ambiental , Radioisótopos de Carbono , ADN Ribosómico/química , ADN Ribosómico/genética , Europa (Continente) , Herbicidas/química , Éteres de Hidroxibenzoatos , Isoxazoles/química , Datos de Secuencia Molecular , Estructura Molecular , ARN Ribosómico 16S/genética , Análisis de Secuencia de ADN , Espectroscopía Infrarroja por Transformada de Fourier
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