Mechanistic Insights into the Formation of Dumbbell-Shaped Carbonate Minerals: A microscale study

Dumbbell-shaped carbonate minerals are widely recognized as a distinctive morphology induced by microorganisms. Understanding their morphological evolution and growth mechanisms is essential for elucidating bacterial-mediated carbonate mineralization processes. In this study, we used the mineralizing bacterium Curvibacter sp. strain HJ-1 to induce the formation of dumbbell-shaped carbonate minerals within a rapid crystallization system with a Mg/Ca ratio = 5. A range of microscale analytical techniques, including scanning electron microscopy, focused ion beam, and transmission electron microscopy, were employed to systematically investigate the morphological changes and crystallographic orientation of these minerals. The results reveal that the formation process involves the aggregation of Ca-Mg nanoparticles at both ends of the structure, with bacterial cells acting as a template. These findings offer preliminary insights into the formation mechanisms of dumbbell-shaped minerals and provide a scientific basis for biogenic analysis of field samples.