Quantifying the Mechanics of Lichen-like Consortia

Lichens are natural-occurring symbiotic consortia containing photosynthetic cyanobacteria and filamentous fungi. The mechanics of natural lichens are not well-studied due to their extremely slow growth, highly heterogenous structure, and difficulty in separating from their growth substrates. Previous work has established co-cultures with enhanced growth rate and biomass accumulation. Here, we utilize a recapitulated lichen-like consortia using the fungus Aspergillus niger and cyanobacterium Synechococcus elongatus to facilitate rapid growth and consistent composition. S. elongatus is engineered to secrete sucrose via expression of a sucrose transporter (cscB) and synthase (SPS) upon IPTG induction. We grow the lichen-like consortia in distinct geometries, including films and fibers. We quantify growth with varying processing conditions and carbon sources and measure the uniaxial stress-strain response of the co-cultures. We observe heterotrophic metabolism of cyanobacterially-produced sucrose, allowing for growth of the co-culture without a carbon source. Our results provide insights into how the structural morphology developed by growing two species together alters the resultant mechanical properties of lichen-like consortia.