Feedback effect of the size of mineral particles on the molecular mechanisms employed by Caballeronia mineralivorans PML1(12) to weather minerals

Mineral dissolution by bacteria is thought to depend on mineral properties, solution chemistry, and the carbon sources metabolized. To investigate whether mineral particle size could impact the effectiveness of weathering and the molecular mechanisms employed by bacteria, the strain Caballeronia mineralivorans PML1(12) was considered. Through microcosm and kinetic experiments, we quantified changes in biotite dissolution, bacterial growth, siderophore biosynthesis, and acidification. The use of different solution chemistries, carbon sources, and particle sizes (from <20 to 500 µm) allowed us to decipher the relative role of acidification- and chelation-driven mineral weathering by bacteria. Results revealed a faster dissolution for smaller particles (<100 µm) that strongly affected both solution chemistry and bacterial physiology, while larger particles (>100 µm) showed a slower and steady dissolution with minimal impact on bacterial processes. These findings underscore the influence and feedback effects of particle size on the dynamics of dissolution and the mechanisms employed by bacteria.