Influence of Forest Trees on the Distribution of Mineral Weathering-Associated Bacterial Communities of the Scleroderma citrinum Mycorrhizosphere

Abstract

In acidic forest soils, availability of inorganic nutrients is a tree-growth-limiting factor. A hypothesis to explain sustainable forest development proposes that tree roots select soil microbes involved in central biogeochemical processes, such as mineral weathering, that may contribute to nutrient mobilization and tree nutrition. Here we showed, by combining soil analyses with cultivation-dependent analyses of the culturable bacterial communities associated with the widespread mycorrhizal fungus Scleroderma citrinum, a significant enrichment of bacterial isolates with efficient mineral weathering potentials around the oak and beech mycorrhizal roots compared to bulk soil. Such a difference did not exist in the rhizosphere of Norway spruce. The mineral weathering ability of the bacterial isolates was assessed using a microplaque assay that measures the pH and the amount of iron released from biotite. Using this microplate assay, we demonstrated that the bacterial isolates harboring the most efficient mineral weathering potential belonged to the Burkholderia genus. Notably, previous work revealed that oak and beech harbored very similar pHs in the 5-to 10-cm horizon in both rhizosphere and bulk soil environments. In the spruce rhizosphere, in contrast, the pH was significantly lower than that in bulk soil. Because the production of protons is one of the main mechanisms responsible for mineral weathering, our results suggest that certain tree species have developed indirect strategies for mineral weathering in nutrient-poor soils, which lie in the selection of bacterial communities with efficient mineral weathering potentials.

Mineral Types and Tree Species Determine the Functional and Taxonomic Structures of Forest Soil Bacterial Communities

“…In addition, our cultivation-independent approach highlighted a significant enrichment of 16S rRNA gene sequences related to Burkholderia and Collimonas on obsidian and apatite. Moreover, several effective mineralweathering bacterial strains isolated in this study presented a strong homology of their 16S rRNA gene sequences with those of effective mineral-weathering bacterial strains previously isolated from the same experimental site in the rhizosphere or on mineral surfaces (33,68,69). Interestingly, significant positive correlations between the level of mineral dissolution and the relative abundance of 16S rRNA gene sequences assigned to the Betaproteobacteria class or to the Burkholderiales order were found for apatite particles incubated for 4 years in forest soil (33,34).…”

Community structure of bacteria on different types of mineral particles in a sandy soil

“…The expected presence of amorphous ferric oxide/oxyhydroxide coatings on the reddish brown particles attracts organic compounds (Violante et al 2002;Wagai et al 2009). Members of the order Burkholderiales have a variety of physiological traits and lifestyles (Vial et al 2011); they are able to use a wide array of compounds as carbon sources (e.g., Chiarini et al 2006;Morimoto et al 2008;Saito et al 2008) and are revealed to have efficient mineral weathering potentials (Calvaruso et al 2010). This metabolic versatility may help them survive on the reddish brown particles where organic compounds accumulate.…”

Correlation of the Abundance of Betaproteobacteria on Mineral Surfaces with Mineral Weathering in Forest Soils

“…In this context, the release of key nutritive cations by mineral weathering processes is crucial. It is now established that, in addition to purely abiotic processes, soil microorganisms affect ion cycling and plant nutrition by releasing nutritive cations from minerals (5,10,20,21,52).…”