Minerals Affect the Specific Diversity of Forest Soil Bacterial Communities

Minerals constitute an ecological niche poorly investigated in the soil, in spite of their important role in biogeochemical cycles and plant nutrition. To evaluate the impact of minerals on the structure of the soil bacterial communities, we compared the bacterial diversity on mineral surfaces and in the surrounding soil. Three pure and calibrated minerals (apatite, plagioclase and a mix of phlogopite-quartz) were buried into the organo-mineral layer of a forest soil. After a 4-year incubation in soil conditions, mineral weathering and microbial colonization were evaluated. Apatite and plagioclase were the only two significantly weathered minerals. The analysis of the 16S rRNA gene sequences generated by the cloning-sequencing procedure revealed that bacterial diversity was higher in the surrounding soil and on the unweathered phlogopite-quartz samples compared with the other minerals. Moreover, a multivariate analysis based on the relative abundance of the main taxonomic groups in each compartments of origin demonstrated that the bacterial communities from the bulk soil differed from that colonizing the minerals. A significant correlation was obtained between the dissolution rate of the minerals and the relative abundance of Beta-proteobacteria detected. Notably, many sequences coming from bacteria colonizing the mineral surfaces, whatever the mineral, harbored high similarity with efficient mineral weathering bacteria belonging to Burkholderia and Collimonas genera, previously isolated on the same experimental site. Taken together, the present results provide new highlights concerning the bacterial communities colonizing minerals surfaces in the soil and suggests that the minerals create true ecological niches: the mineralosphere.