Spatial variations in bacterial and archaeal abundance and community composition in boreal forest pine mycorrhizospheres

Abstract Mycorrhizal fungi have a strong impact on soil biota. In this study, bacterial and archaeal populations in different parts of Suillus bovinus - Pinus sylvestris mycorrhizospheres in boreal forest were quantified and identified by DNA analysis. The numbers of bacterial and archaeal 16S rRNA gene copies were highest in uncolonized humus and lowest in fruiting bodies. The numbers of bacterial 16S rRNA gene copies varied from 1.3 × 107 to 3.1 × 109 copies g−1 fw and archaeal copies from 4.1 × 107 to 9.6 × 108 copies g−1 fw. The relatively high number of archaeal 16S rRNA gene copies was likely due to the cold and highly organic habitat. The presence of hyphae appeared to further promote archaeal numbers and the archaea:bacteria ratio was over one in samples containing only fungal material. Most detected archaea belonged to terrestrial Thaumarchaeota. Proteobacteria, Actinobacteria and Acidobacteria were predictably the dominating bacterial taxa in the samples with clear trend of Betaproteobacteria preferring the pine root habitats.