Members of the phylum Acidobacteria are dominant and metabolically active in rhizosphere soil

A culture-independent survey was performed to search for 16S rRNA gene sequences representing dominant and metabolically active bacteria in rhizosphere soil. PCR- and reverse transcription-PCR-derived clone libraries were constructed from DNA and RNA directly extracted from the soil sample. Acidobacteria-related sequences occupied an unusually large proportion (> 50%) of both rDNA- and rRNA-derived clone libraries. This study suggested that the bacteria belonging to the phylum Acidobacteria might be numerically dominant as well as metabolically active in the soil sample, implying that the phylum Acidobacteria might be highly involved in the biogeochemical cycles of the rhizosphere soil.