Microbialites as Self-Assembling and Self-Repairing Building Materials

Living materials, an innovative and emergent class of materials, are expanding our opportunities to construct, maintain, and repair buildings as well as produce materials in resource-scarce locations, such as in space. Natural materials, including bone, wood, and bacterial biofilms, adapt their properties based on environmental factors. These materials naturally exhibit autonomous growth, sensing, metabolite secretion and regeneration. Engineered living materials aim to mimic these characteristics to create functional, stimuli-responsive materials. Lichen are an example of synergistic microbial communities with a heterotrophic fungal partner (mycobiont) and a photoautotrophic partner (photobiont, either an alga or a cyanobacterium). When lichen form minerals, they could also be considered microbialites, generally defined here as microbial communities with lithification capacity. Using microbialites for manufacturing applications has the potential to harness the progress of millions of years of evolution to improve sustainable biomanufacturing strategies.<br/>We hypothesize that by leveraging the synergy between the mycobiont and the photobiont, materials and structures can be grown, which are also capable of self-repair. Here, we present work, which uses organisms capable of forming lichen to produce living materials for prospective infrastructural applications. In lichen, only the co-culture of the two partners is capable of producing the emergent lichen structure, while neither partner alone is capable of doing so. Furthermore, lichen are resilient and can grow (albeit slowly) using carbon dioxide as the sole carbon source.<br/>Our primary goals are (1) designing self-sustaining co-cultures capable of biomineralization, (2) understanding and controlling the contribution of each community member to the overall biomineralization process, and (3) optimizing the material properties of the biomineralized products. Initial efforts have identified promising myco- and photobionts, including Aspergillus niger, Neurospora crassa, Aureobasidium pullulans, Nostoc sp. PCC 6720, and a high pH-tolerant green alga (Chlorella sp.). These selections are based on existing evidence of mutualistic relationships and their potential for contributing to biomineralization.<br/>By manipulating environmental parameters such as pH, light, nutrient availability (incl. CO2), and temperature, we aim to understand and ultimately control the mechanisms through which these organisms contribute to biomineralization and the creation of structures. The produced structures and materials will be examined in terms of hardness and strength using nanoindentation and compression testing, respectively. Scanning Electron Microscopy combined with Energy Dispersive X-ray Spectroscopy and X-Ray Diffraction techniques assist with material characterization such as assessing the composition and structure of the produced material. <br/>In summary, the integration of our insights gained from the sustainable microbial co-cultures and our material characterizations will contribute to the development of novel materials that meet specific structural and environmental requirements, paving the way for their application in sustainable construction and beyond.