Characterization of microbial communities associated with the rhizosphere of wetland plants from the Sudbury Region

Abstract

The role of microbial communities within the plant rhizosphere is a rapidly developing area of research. Specificity of microbial community structure to plant species and environmental drivers of this relationship are not yet well understood in natural communities, particularly in wetlands. In the present thesis, species-specific differences in those communities as well as environmental influences on those differences were examined separately. In an experiment, six different wetland species taken from field sites around Sudbury, Ontario were grown in mesocosms in a wetland garden for two growing seasons. The species included two species from two genera of the family Cyperaceae each, one species of Poaceae and one species of Ericaceae. Mesocosms were inoculated with a mixture of field rhizosphere soils from all the collected plants. A field study was simultaneously conducted on the rhizospheres of two of those species from wetlands along an industrial disturbance gradient. The microbial community structures of the rhizospheres of the selected wetland plants were determined using next generation 454-pyrosequencing techniques. Microbial community structure in the garden experiment showed specificity to plant taxa which was related to the phylogeny of the host plant, the differences increasing with decreasing taxonomic relatedness of the plants. Differences in the microbial community structure between the investigated plant species were also found in the field, but were secondary to site-specific effects. I conclude that the microbial community structure of the rhizosphere does differ between plant species and that environmental conditions were stronger than plant-microbe interactions in the scale of influence over microbial community structure.