Interactions between fungi, algae, and bacteria: multispecies engineered living materials leverage function and structure

The need for materials that have a limited impact on the environment has led to the development of engineered living materials (ELMs), which integrate living organisms and material applications to generate functional matter. Filamentous fungi offer a promising scaffold to design ELMs, which can be produced from the bottom up, but the possibilities for introducing dynamic functionalities are limited. To solve this, multispecies ELMs can be designed, using bacteria and algae to introduce biological functions in the material. The amenability of bacteria for synthetic biology offers a suitable platform to develop novel functions, while algae can endow the material with photosynthetic properties. Due to the preexisting natural interactions between these organisms and fungi, such as lichens and fungal highways, the establishment of a consortium-based bottom-up ELM becomes feasible. In this review, we summarize the natural mutualistic interactions between fungi, algae, and bacteria and how they can be harnessed for the design and implementation of engineered living materials, using filamentous fungi as their structural backbone. Furthermore, we review the role of such interactions in industrial processes, where they have been engineered for wastewater treatment and biotechnological production. Lastly, we discuss the current challenges of engineered living materials, the advantages of consortia-based solutions, and their future perspectives.