Mineral weathering by Collimonas pratensis PMB3(1) as a function of mineral properties, solution chemistry and carbon substrate

Abstract

While the role of mineral weathering (MWe) bacteria in nutrient cycling and plant growth promotion is established, our understanding of the molecular mechanisms involved and how their contribution to MWe varies according to the mineral properties and the environmental conditions remain poorly documented. In this study, we investigate how the type of mineral, the source of carbon and the buffering capacity of the medium impacted the effectiveness at weathering of the strain PMB3(1) of Collimonas pratensis and the molecular mechanisms involved. Using abiotic and biotic weathering tests, we characterised the weatherability of the different minerals considered (i.e., biotite, olivine, garnet, hematite, apatite). We reveal that the model PMB3(1) strain is able to weather all the minerals tested and that its effectiveness is related to the weatherability of each mineral in poorly buffered condition, but not in buffered condition. Using single and double mutants affected in their Glucose-Methanol-Choline oxidoreductase activity and/or the biosynthesis of siderophore, we identify which mechanism the strain PMB3(1) uses to weather minerals in each condition. Our results indicate that the effectiveness at weathering of bacteria depends more strongly on the environmental conditions (carbon source, buffering capacity) than on the mineral type.