Seasonal variations of Bacillus isolated from the rhizosphere of Elaeagnus angustifolia L

The rhizosphere of Elaeagnus angustifolia L. was sampled monthly during one year and the genera of the isolated bacteria were determined. Bacillus predominated in all seasons. Eight groups of Bacillus were identified according to biochemical tests described in the Bergey's Manual, from which, group VII, with B. mycoides and B. laterosporus as the most likely species to define it, predominated (total year average of 60.5%). In order to determine intrageneric variation, additional tests as resistance to antibiotics and use of different carbon sources were assayed. According to both tests, the Bacillus strains isolated from the rhizosphere of E. angustifolia differed significantly throughout the year. These results suggest the adaptation of rhizospheric microbial communities to environmental conditions, so variable in Mediterranean climates, and to the physiological status of the plant.Se muestreó la rizosfera de E. angustifolia L. durante un año y se determinaron los géneros a los que pertenecían las bacterias aisladas. Bacillus predominó durante todo el año. Se identificaron ocho grupos de Bacillus según las pruebas bioquímicas del Manual Bergey's entre los cuales predominaba el grupo VII (media anual 60.5%). Con objeto de determinar la variación intragenérica, se realizaron pruebas de resistencia a antibióticos y metabolización de fuentes de carbono. En ambos casos se encontraron diferencias significativas anua-les. Estos resultados sugieren la gran capacidad de adaptación de las comunidades microbianas rizosféricas tanto a las condiciones ambientales, tan variables en climas mediterráneos, como al estado fisiológico de la planta