Bacterial community structure in the rhizosphere of three cactus species from semi-arid highlands in central Mexico |
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Authors: | J Félix Aguirre-Garrido Daniel Montiel-Lugo César Hernández-Rodríguez Gloria Torres-Cortes Vicenta Millán Nicolás Toro Francisco Martínez-Abarca Hugo C Ramírez-Saad |
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Institution: | 1. Doctorado en Ciencias Biológicas, UAM-Xochimilco, C.P. 04960, Mexico City, Mexico 2. Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas, IPN, C.P. 11340, Mexico City, Mexico 3. Estación Experimental del Zaidín-CSIC, 18008, Granada, Spain 4. Departamento de Sistemas Biológicos, Universidad Autónoma Metropolitana-Xochimilco, Calz. del Hueso 1100, C.P. 04960, Mexico City, Mexico
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Abstract: | The nature reserve of Tehuacan-Cuicatlan in central Mexico is known for its diversity and endemism mainly in cactus plants.
Although the xerophytic flora is reasonably documented, the bacterial communities associated with these species have been
largely neglected. We assessed the diversity and composition of bacterial communities in bulk (non-rhizospheric) soil and
the rhizosphere of three cactus plant species: Mammillaria carnea, Opuntia pilifera and Stenocereus stellatus, approached using cultivation and molecular techniques, considering the possible effect of dry and rainy seasons. Cultivation-dependent
methods were focused on putative N2-fixers and heterotrophic aerobic bacteria, in the two media tested the values obtained for dry season samples grouped together
regardless of the sample type (rhizospheric or non-rhizospheric), these groups also included the non-rhizospheric sample for
rainy season, on each medium. These CFU values were smaller and significantly different from those obtained on rhizospheric
samples from rainy season. Genera composition among isolates of the rhizospheric samples was very similar for each season,
the most abundant taxa being α-Proteobacteria, Actinobacteria and Firmicutes. Interestingly, the genus Ochrobactrum was highly represented among rhizospheric samples, when cultured in N-free medium. The structure of the bacterial communities
was approached with molecular techniques targeting partial 16S rRNA sequences such as denaturing gradient gel electrophoresis
and serial analysis of ribosomal sequence tags. Under these approaches, the most represented bacterial phyla were Actinobacteria,
Proteobacteria and Acidobacteria. The first two were also highly represented when using isolation techniques. |
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