Bacterial Swarming-Guided Biomineralization Enables Pattern Formation in Engineered Living Materials

Engineered living materials (ELMs) harness the adaptive capabilities of biological systems to create diverse functional materials. While most ELM strategies rely on static microbial assemblies, the role of bacterial motility in structuring living materials remains largely unexplored. Here, we demonstrate that swarming motility in Escherichia coli MG1655 can spatiotemporally organize calcium phosphate. Scanning electron microscopy and X-ray diffraction patterns differentiate regularly spaced concentric hydroxyapatite deposition of bacteria from abiotic precipitation. We further show that bacterial activity promotes local alkalinization, contributing to calcium phosphate mineralization, and that phosphate chemistry, along with calcium concentration, modulates both swarming and mineral patterning. A continuum model captures the spatiotemporal coupling between swarm expansion and mineral deposition, showing that recurrent front arrest and restart can generate concentric rings. Together, we establish bacterial swarming as a dynamic mechanism for spatially organizing biomineralization and provide a framework for programmable pattern formation in ELMs.