Inspired by naturally occurring biomaterials, autonomously grown engineered living materials (ELMs) feature cell-driven growth and programmable biological functions. However, the "livingness" of cells poses a short life span and low tolerance to harsh conditions, limiting the practical use of such materials. Here, we developed materials with programmable and dormant functionalities, grown from a mixture of Komagataeibacter rhaeticus and Bacillus endospores under engineered medium conditions. K. rhaeticus produces the bacterial cellulose (BC) matrix that integrates Bacillus spores within, whereas the confined spores keep dormant and are resistant to harsh conditions in the environment. Bacillus spores can germinate and confer desired functions to the materials. Modulating the binding affinity of spores to the BC matrix with genetic engineering can improve cell loading and therefore enhance the material functionality. These materials can serve as a versatile on-demand platform for applications as biosensors, biocatalytic materials, and in situ transformation of mechanically robust cellulose-based composites.

Inspired by biological functions of living systems, researchers have engineered cells as independent functional materials or integrated them within a natural or synthetic matrix to create engineered living materials (ELMs). However, the ‘livingness’ of cells in such materials poses serious drawbacks, such as a short lifespan and the need for cold-chain logistics. Bacterial spores have emerged as a game changer to bypass these shortcomings as a result of their intrinsic dormancy and resistance against harsh conditions. Emerging synthetic biology tools tailored for engineering spores and better understanding of their physical properties have led to novel applications of spore-based materials. Here, we review recent advances in such materials and discuss future challenges for the development of time- and cost-efficient spore-based materials with high performance.