The oxidation and reduction of manganese underpin numerous processes, from photosynthesis and defense against oxidative stress to the biogeochemical cycling of trace metals and organic matter. Microbial manganese oxidation, which typically leads the formation of MnO 2 (s), was documented more than a century ago. However, its physiological function remains elusive. Also lacking is knowledge of the factors that control the regulation and transcription of the enzymes leading to manganese biomineralization. In this talk I will present a novel reporter gene fusion system that we developed to study the activation of the genes encoding two manganese oxidases in the common bacterium, Pseudomonas putida GB-1. This system has enabled the first temporally and spatially resolved analysis of manganese oxidase promoter activation at the single cell level and ability to correlate gene activation with mineral precipitation across a range of environmental conditions. The mechanism of manganese biomineralization that emerges is one regulated at the population-level and not at the single cell level. Further, the two manganese oxidases are regulated by specific chemical cues that expand the ecological niches for manganese biomineralization. This work provides a new framework to investigate how microbial communities orchestrate the extent, location and timing of biogeochemical transformations, while providing new insights on the interface between life and minerals.